METHOD FOR REMOVING OXYGEN FROM A GAS STREAM

A process for removing oxygen from a gas stream and a method of controlling the process are provided herein. The deoxygenation process of the present invention may include the steps of combining a feed stream, such as a natural gas feed stream, with hydrogen and contacting the combined stream with a catalyst composition under conditions sufficient to remove at least a portion of the oxygen from the combined gas. In some cases, the catalyst composition can comprise copper and the conditions of the contacting may be such that at least a portion of the copper remains in a reduced state during deoxygenation. The method of controlling the deoxygenation process described herein includes utilizing measured values of parameters of the deoxygenated stream to control one or more parameters of the feed gas stream introduced into the deoxygenation zone and achieve a desired level of oxygen removal.

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Description
FIELD OF THE INVENTION

This invention relates to systems and methods for removing oxygen from a gas stream. In another aspect, embodiments of this invention also relate to methods for controlling such processes.

BACKGROUND

Natural gas is widely used as a fuel source and has many commercial, residential, and industrial applications. Primarily produced from subterranean formations, natural gas often includes undesired constituents such as sulfur, water, nitrogen, carbon dioxide, and/or oxygen. In some cases, these components are naturally-occurring as a result of the particular formation from which the gas was produced. In other cases, these contaminants can enter the gas stream as a result of the methods or systems used to facilitate production of the gas from the underground deposit or as a result of its transportation from one location to another.

Oxygen is one component often present in natural gas, especially natural gas produced from mature fields, that is desirable to remove. Early in the life of a gas deposit, sufficient pressure typically exists for the natural gas to flow freely from the formation. As the field matures and the gas is depleted, the pressure of the deposit decreases and the gas must be extracted from the formation. At times, oxygen may enter the gas stream as a result of the extraction methods used, typically through leaks in the removal or transport system. Allowed to remain in high concentrations in the natural gas stream, oxygen contributes to corrosion (especially in the presence of residual water) and may also cause undesired side reactions in downstream processing equipment, which may lead to excessive equipment shut downs and lost production. As a result, producers must remove excess oxygen from natural gas in order to meet pipeline specifications, which typically limit oxygen contents to 50 parts per million by volume (ppmv) or less.

Blending is one method used by producers to incorporate high oxygen-content gas into a pipeline-compliant product, although the volume of low-oxygen gas required to produce an on-specification product severely limits the volume high oxygen gas any one facility can accept. Other conventional oxygen removal techniques, including, for example, catalytic deoxygenation methods, are often limited by expensive catalysts, high operating temperatures and/or pressures, and/or significant downtime resulting from production outages required to manage catalyst regeneration or replacement. As a result, many producers limit production and/or intake of high-oxygen natural gas, which leaves a significant natural gas resource under utilized.

Thus, a need exists for an effective, convenient, and relatively inexpensive system and method for removing oxygen from a natural gas stream. The system should be operationally flexible and efficient and should also be capable of large scale implementation in both new and existing facilities. Ideally, the system would minimize capital and operating expenses while maximizing production in terms of both throughput and days on stream.

SUMMARY

Some embodiments of the present invention concerns a process for removing oxygen from a natural gas stream, the process comprising: (a) combining an oxygen-containing natural gas stream with a reducing agent to form a combined gas stream; and (b) contacting at least a portion of the combined gas stream with at least one copper-containing catalyst in a deoxygenation zone to thereby provide an oxygen-depleted gas stream, wherein the contacting is carried out under conditions sufficient to maintain at least a portion of the copper of the copper-containing catalyst in a reduced state during the contacting.

Another embodiment of the present invention concerns a process for removing oxygen from a natural gas stream, the process comprising: (a) introducing oxygen-containing natural gas and hydrogen into a deoxygenation zone, wherein the hydrogen is present in the deoxygenation zone in a non-stoichiometric amount relative to the amount of oxygen present in the deoxygenation zone; and (b) removing at least a portion of the oxygen from the natural gas with at least one catalyst in the deoxygenation zone to thereby provide an oxygen-depleted natural gas stream, wherein the average temperature of the deoxygenation zone is less than about 480° F.

Yet another embodiment of the present invention concerns a method for controlling a process for removing oxygen from a gas stream, the method comprising the steps of (a) combining an oxygen-containing feed gas stream with a hydrogen stream to thereby provide a combined feed gas stream; (b) passing at least a portion of the combined feed gas stream through a deoxygenation zone, wherein the passing comprises contacting the combined feed gas stream with at least one catalyst to remove at least a portion of the oxygen from the combined feed gas stream and provide an oxygen-depleted gas stream; (c) measuring a value for at least one parameter of the oxygen-depleted gas stream; (d) comparing the measured value for the parameter of the oxygen-depleted gas stream determined in step (c) with a target value for the parameter of the oxygen-depleted gas stream to determine a difference; and (e) based on the difference, controlling at least one parameter of the combined gas stream in order to minimize the difference.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a schematic depiction of a natural gas process facility configured according to some embodiments of the present invention, particularly illustrating the use of hydrogen injection to control the oxygen content of a natural gas stream;

FIG. 2 is a schematic depiction of a deoxygenation zone configured according to some embodiments of the present invention, particularly illustrating certain aspects of a method of controlling the deoxygenation process; and

FIG. 3 is a flowchart representing the major steps involved in a method for controlling a deoxygenation process according to some embodiments of the present invention, particularly useful for controlling the deoxygenation zone schematically depicted in FIG. 2.

 DETAILED DESCRIPTION

Turning initially to FIG. 1, a gas processing facility 10 configured according to one or more embodiments of the present invention is provided. Gas processing facility 10 is illustrated as generally comprising a sulfur removal zone 20, a deoxygenation zone 30, and a product treatment zone 40. Product treatment zone 40 can include one or more processes used to treat the deoxygenated gas stream and, in some embodiments shown in FIG. 1, may include, for example, at least one component removal zone 50 and/or at least one product purification zone 60.

In operation, a feed gas stream in conduit 110 introduced into gas processing facility 10 may first be passed through sulfur removal zone 20 in order to remove one or more sulfur-containing compounds. Thereafter, the resulting desulfurized stream in conduit 112 can be combined with a reducing agent via conduit 114a prior to, and/or with a reducing agent in conduit 114b simultaneous with, its introduction into deoxygenation zone 30. Once in deoxygenation zone 30, the oxygen-containing gas stream, in combination with the reducing agent, may contact at least one catalyst composition under conditions sufficient to remove at least a portion of the oxygen present in the gas stream introduced into deoxygenation zone 30. The resulting oxygen-depleted gas stream in conduit 118 may optionally be routed for further separation and/or processing in a product treatment zone 40, which, as shown in the embodiment depicted in FIG. 1, can include at least one component removal zone 50 and/or at least one product purification zone 60.

In one embodiment, the feed gas stream introduced into gas processing facility 10 via conduit 110 may originate from any suitable feed gas source (not shown), such as, for example, an upstream processing unit or facility, a natural source, or any other suitable gas source. In some embodiments, the feed gas stream in conduit 110 may originate from a natural source, such as, for example, a subterranean oil and gas formation. Optionally, the gas stream in conduit 110 may have undergone one or more pre-processing steps, such as, for example, separation, drying, or other processing step (not shown) prior to being introduced into gas processing facility 10 via conduit 110.

The feed gas stream in conduit 110 can comprise a mixture of one or more different components, and may, in some embodiments, include one or more hydrocarbons. When the feed gas stream in conduit 110 is a hydrocarbon-containing gas stream, it can comprise at least about 1, at least about 2, at least about 5, at least about 10, at least about 25, at least about 30, at least about 40, at least about 50 and/or not more than about 99, not more than about 97, not more than about 95, not more than about 90, not more than about 85, not more than about 75 mole percent of one or more hydrocarbon components, based on the total moles of the hydrocarbon-containing gas stream.

In some embodiments, the feed gas stream in conduit 110 can be a natural gas stream. As used herein, the term “natural gas stream” refers to a hydrocarbon-containing stream including hydrocarbons having six or less carbon atoms per molecule. In some embodiments, the feed gas stream in conduit 110 at least about 40, at least about 50, at least about 60, at least about 75 mole percent and/or not more than about 99, not more than about 95, not more than about 85 mole percent of one or more hydrocarbons having six or less carbon atoms per molecule. Examples of hydrocarbons present in a natural gas feed stream can include, but are not limited to, methane, ethane, ethylene, propane, propylene, butane, butene, pentane, pentene, hexane, and hexene, and isomers thereof, and combinations thereof. Further, some embodiments, the feed gas stream in conduit 110 may include less than about 30, less than about 25, less than about 20, less than about 10, less than about 5, or less than about 1 mole percent of hydrocarbon components having more than six carbon atoms per molecule. In some embodiments, the feed gas stream may not comprise naphtha, gasoline, or other petroleum cuts that have normal boiling points heavier than naphtha and gasoline.

When the feed gas stream in conduit 110 comprises a natural gas feed stream, a large portion of the hydrocarbons present in the stream may be hydrocarbons having three or less carbon atoms per molecule. In particular, in some embodiments, the feed gas stream may include at least about 40, at least about 50, at least about 60, at least about 75 mole percent and/or not more than about 99, not more than about 95, not more than about 90, not more than about 85 mole percent of hydrocarbons having three or less carbon atoms per molecule. Additionally, in other embodiments, the feed gas stream in conduit 110 may also include methane in an amount of at least about 40, at least about 50, at least about 60, at least about 70, at least about 80, at least about 90 mole percent, based on the total moles of hydrocarbon present in the feed gas stream. In some embodiments, methane may be present in an amount of at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, at least about 50, at least about 55, at least about 60, at least about 65, at least about 75 mole percent, based on the total moles of the feed gas stream. In the same or other embodiments, the feed gas stream in conduit 110 can have an average energy content of at least about 500, at least about 650, at least about 750, at least about 850, at least about 950 BTU/ft3 and/or not more than about 4500, not more than about 4000, not more than about 3000, not more than about 2500, not more than about 2000, not more than about 1500 BTU/ft3.

In addition, the feed gas stream may also include minor amounts of other non-hydrocarbon components, such as, for example, inert gas components. Examples of inert gas components can include, but are not limited to, nitrogen, neon, xenon, argon, helium, krypton, radon, and combinations thereof. According to some embodiments, the feed gas stream in conduit 110 can comprise less than about 10, less than about 5, less than about 2, less than about 1, or less than about 0.5 mole percent of one or more of the inert gas components listed above. For example, in some embodiments, the feed gas stream in conduit 110 can comprise less than about 5, less than about 2, less than about 1, or less than about 0.5 mole percent of one or more inert gases selected from the group consisting of neon, xenon, argon, helium, krypton, radon, and combinations thereof, while in the same or another embodiment, the feed gas stream may include less than about 10, less than about 8, less than about 6, less than about 4, less than about 2, or less than about 1 mole percent of nitrogen and/or helium. According to some embodiments, the feed gas stream in conduit 110 may not be an inert gas stream and it may include no, or substantially no, inert gas components.

The feed gas stream in conduit 110 may also include small amounts of one or more combustion products, such as, for example, carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx), sulfur oxides (SOx), and combinations thereof. According to some embodiments, the feed gas stream in conduit 110 can include less than about 2, less than about 1, less than about 0.5, or less than about 0.25 mole percent of one or more combustion products listed above, based on the total moles of the feed gas steam. In the same or other embodiments, the feed gas stream in conduit 110 may comprise less than about 2000, less than about 1500, less than about 1000, less than about 500 parts per million by weight (ppmw) of CO and/or CO2, based on the total weight of the feed gas stream. Depending, in part, on the source of the feed gas stream in conduit 110, the feed gas stream may, in some embodiments, include no, or substantially no, combustion products.

The feed gas stream in conduit 110 can also comprise water. In some embodiments, the feed gas stream in conduit 110 can comprise at least about 50, at least about 100, at least about 250, at least about 500 parts per million by weight (ppmw) and/or not more than about 0.5 weight percent, not more than about 0.1 weight percent, not more than about 5000, or not more than about 1000 ppmw of water based on the total weight of feed gas stream in conduit 110. Where the water content of the feed gas exceeds one or more of the upper limits provided above, gas processing facility 110 can further comprise an upstream drying zone (not shown in FIG. 1) for removing at least a portion of the water from the incoming stream. The drying zone, when present, may include physical separation devices, such as vapor-liquid separators, for removing large volumes of water from the inlet gas and/or it may include one or more drying vessels employing mole sieve or other solid desiccant for contacting the feed gas and removing water from the stream in conduit 110.

In some embodiments, the feed gas stream in conduit 110 may also include one or more sulfur-containing components including, for example, organic and/or inorganic sulfur-containing compounds. Examples of sulfur-containing compounds that may be present in the feed gas stream in conduit 110 include, but are not limited to, hydrogen sulfide (H2S), carbonyl sulfide (COS), carbon disulfide (CS2), mercaptans (R—SH), organic sulfides (R—S—R), organic disulfide (R—S—S—R), and combinations thereof. The amount and/or type of sulfur present in the feed gas stream may depend, at least in part, on the source of the feed gas stream and on any upstream processing to which the stream may have been subjected. In some embodiments, the feed gas stream in conduit 110 can include less than about 5, less than about 2, less than about 1, or less than about 0.5 mole percent of one or more sulfur-containing compounds, based on the total moles of the feed gas stream.

When the feed gas stream in conduit 110 includes a sufficient amount of one or more sulfur-containing compounds, it may be desirable to treat the feed gas stream in conduit 110 to remove at least a portion of the sulfur-containing compounds in sulfur removal zone 20 prior to introduction of the stream into deoxygenation zone 30, as generally illustrated in some embodiments depicted in FIG. 1. Sulfur removal zone 20 illustrated in FIG. 1 can comprise any process or unit capable of removing at least a portion of one or more sulfur-containing compounds from the feed gas stream in conduit 110. In some embodiments, sulfur removal zone 20 may be configured to reduce the amount of sulfur in the feed gas stream by at least about 10, at least about 20, at least about 30, at least about 40, at least about 50, at least about 60 percent, based on the total amount of sulfur originally present in the feed gas stream introduced into sulfur removal zone 20 via conduit 110. Optionally, at least a portion of the sulfur removal process utilized in sulfur removal zone 20 can be carried out in the presence of hydrogen, which can be added via conduit 111 as shown in FIG. 1. When used, hydrogen may be present in an amount of at least about 500, at least about 750, at least about 1000 parts per million by volume (ppmv), and/or not more than about 5000, not more than about 2500, not more than about 1500 ppmv.

Sulfur removal zone 20 can include any suitable type of sulfur removal process or treatment step. In some embodiments, sulfur removal zone 20 may employ a liquid solvent, such as an amine or caustic, for contacting the incoming gas stream in a column or washer. In the same or another embodiment, sulfur removal zone 20 can employ at least one solid sulfur removal compound, such as an adsorbent, utilized in one or more fixed or moving bed vessels. As used herein, the term “adsorbent” is not limited to material capable of chemically and/or physically adsorbing one or more sulfur-containing compounds, but is also intended to encompass materials that catalyze and/or absorb sulfur-containing materials. When the adsorbent material present in sulfur removal zone 20 includes a solid support, it may optionally be promoted with at least one desulfurization metal supported on, in, and/or within at least a portion of the support material. The support material can comprise a porous material such as, for example, alumina, zinc, silica, and combinations thereof. In some embodiments, the support material can comprise zinc oxide.

When the adsorbent material is promoted with at least one desulfurization metal, the metal can comprise any metal capable of chemically reacting or coordinating with one or more types of sulfur-containing compounds. Examples of suitable desulfurization metals can include, but are not limited to, nickel, cobalt, molybdenum, copper, silver, ruthenium, rhodium, palladium, tungsten, manganese, chromium, and combinations thereof. When utilized, the desulfurization metal can be present in the adsorbent material in an amount of at least about 0.5, at least about 1, at least about 2 weight percent and/or not more than about 8, not more than about 6, not more than about 5 weight percent, based on the total weight of the absorbent material. When the adsorbent includes two or more desulfurization metals, the total weight of both metals may fall in the ranges above, while the amount of each individual metal may be at least about 0.25, at least about 0.5, at least about 1 and/or not more than about 5, not more than about 4, not more than about 2.5, not more than about 1.5 weight percent, based on the total weight of the adsorbent material. In some embodiments, the adsorbent can comprise a copper-promoted zinc oxide adsorbent.

In some embodiments, sulfur removal zone 20 may further include one or more other types of processes or treatment steps capable of removing one or more other types of compounds from the incoming gas stream. For example, in some embodiments, gas processing facility 10 may also include one or more treatment zones located upstream of sulfur removal zone 20 for removing inorganic or organic silicon materials and/or particulates. In some embodiments, such treatment zones can include one or more beds of materials such as activated alumina, which, in addition to removing silicon materials, may also be capable of converting at least a portion of one or more sulfur-containing compounds into other sulfur-containing compounds which are more easily removed within sulfur removal zone 20. Additionally, as discussed previously, gas processing facility 10 may also include one or more drying zones located before or after sulfur removal zone 20 to reduce the level of water in the feed gas stream to an amount in the ranges described previously.

Further, sulfur removal zone 20 may, if needed, also include one or more moisture removal or drying zones to reduce the level of water in the feed gas stream to an amount within the ranges provided previously.

Sulfur removal zone 20 can be operated under conditions sufficient to remove at least a portion of one or more sulfur-containing compounds from the feed gas stream in conduit 110. In some embodiments, the desulfurization processes or steps conducted within sulfur removal zone 20 may be carried out at an average temperature of at least about 40° F., at least about 75° F., at least about 100° F., at least about 150° F., at least about 200° F., at least about 250° F., at least about 300° F., at least about 350° F. and/or not more than about 800° F., not more than about 700° F., not more than about 650° F., not more than about 600° F. The pressure of the feed gas stream being treated in sulfur removal zone 20 may also vary, but, in some embodiments, can be at least about 100, at least about 200, at least about 300, at least about 500, at least about 600, at least about 750, at least about 850, at least about 900, and/or not more than about 2500, not more than about 2000, not more than about 1500, not more than about 1000, not more than about 750 psi.

Referring again to FIG. 1, the desulfurized gas stream in conduit 112 exiting sulfur removal zone 20 can comprise less than about 100, less than about 75, or less than about 50, less than about 25, less than about 15, less than about 10, or less than about 1 ppmv of one or more sulfur-containing components. In some embodiments, the desulfurized gas stream in conduit 116 can have a total sulfur content of at least about 1, at least about 2, at least about 5, at least about 10 and/or not more than about 40, not more than about 25, not more than about 20, not more than about 10 ppmv, based on the total volume of the desulfurized feed gas stream in conduit 112. This may represent, in some embodiments, a total sulfur removal efficiency of at least about 50, at least about 60, at least about 70, at least about 80, at least about 90 percent, based on the total amount of sulfur originally present in the feed gas stream in conduit 110. As used herein, the term “sulfur removal efficiency” refers to the difference between the total sulfur content of the desulfurized feed gas stream in conduit 112 and the total sulfur content of the feed gas stream in conduit 110, expressed as a percentage of the total sulfur content of the feed gas stream in conduit 110. In one embodiment, the desulfurized gas stream in conduit 112 can comprise less than about 20, less than about 15, less than about 10, less than about 5 percent of the total amount of sulfur originally present in the feed gas stream in conduit 110, based on the total amount, by weight, of sulfur present in the feed gas stream in conduit 110.

As shown in FIG. 1, the desulfurized gas stream in conduit 116 may subsequently be routed to a deoxygenation zone 30. In some embodiments, the desulfurized gas stream in conduit 112 can have a total oxygen content of at least about 20, at least about 50, at least about 100, at least about 200, at least about 300, at least about 500, at least about 750, at least about 1000 ppmv and/or not more than about 15,000, not more than about 12,500, not more than about 10,000, not more than about 7500, not more than about 5000, not more than about 2500 ppmv, based on the total volume of the stream in conduit 112. In some embodiments, this may be the same as, or may be slightly lower than, the total oxygen content of the feed gas stream introduced into gas processing facility 10 via conduit 110. Accordingly, in some embodiments, sulfur removal zone 20 may not remove any substantial amount of oxygen from the feed gas stream, such that the oxygen content of the feed gas stream in conduit 110 is within about 50, within about 40, within about 30, within about 20, within about 10, or within about 5 percent of the total amount of oxygen in the desulfurized feed gas stream in conduit 112.

As shown in one embodiment depicted in FIG. 1, at least a portion of the desulfurized, but oxygen-containing feed gas stream in conduit 112 can optionally be combined with a reducing agent via conduit 114a to thereby provide a combined gas stream in conduit 116. Alternatively, or in addition, all or a portion of the reducing agent can be combined with the desulfurized feed gas stream within deoxygenation zone 30, as shown conduit 114b. In some embodiments, the reducing agent can comprise hydrogen and, in the same or other embodiments, the reducing agent can be a hydrogen-containing gas stream comprising at least about 50, at least about 65, at least about 75, at least about 85, at least about 90, at least about 95 weight percent hydrogen, based on the total weight of the stream. The hydrogen may originate from any suitable source and, in some embodiments, may originate from other areas within or external to gas processing facility 10.

According to some embodiments, the hydrogen (or other reducing agent, when used) combined with the oxygen-containing gas stream in conduit 116 may be present in the combined gas stream in a non-stoichiometric amount as compared to the amount of oxygen present in the combined stream. As used herein, the term “non-stoichiometric” refers to an amount of hydrogen other than the amount required to exactly react with the oxygen according to the following chemical equation: 2H2+O2->2H2O. Amounts of hydrogen that exceed or fall short of the stoichiometric amount of hydrogen in the oxygen-containing gas stream are each considered to be “non-stoichiometric,” as described herein. In some embodiments, the amount of hydrogen present in the combined gas stream in conduit 116 and/or within deoxygenation zone 30 may be at least about 40, at least about 50, at least about 60, at least about 70, at least about 80, at least about 85, at least about 90, at least about 95 and/or not more than about 200, not more than about 175, not more than about 150, not more than about 125, not more than about 115, not more than about 110, not more than about 105 percent of stoichiometric.

When hydrogen is present in the combined gas feed stream in conduit 116 in a non-stoichiometric amount, the molar ratio of hydrogen to oxygen in the combined gas stream in conduit 116 may not be 2:1. In some embodiments, hydrogen may be present in a sub-stoichiometric amount (i.e., the oxygen may be present in a stoichiometric excess) such that the molar ratio of hydrogen to oxygen in the combined gas stream may be less than 2:1, less than about 1.99:1, less than about 1.95:1, less than about 1.90:1, less than about 1.85:1. In other embodiments, hydrogen may be present in a stoichiometric excess so that the molar ratio of hydrogen to oxygen in the combined stream is at least about 2:01:1, at least about 2.05:1, at least about 2.10:1, or at least about 2.15:1. When all or part of the hydrogen (or other reducing agent) is added to the oxygen-containing feed gas stream within deoxygenation zone 20 via conduit 114b, the molar ratio of the total amount of hydrogen to the total amount of oxygen within desulfurization zone 20 may also fall within one or more of the ranges described above. Specific methods for controlling the amount of hydrogen added to the feed gas stream will be discussed in detail shortly.

Turning again to FIG. 1, the gas stream in conduit 116, which may optionally be a combined gas feed stream including hydrogen or other reducing agent introduced via conduit 114a, can then be routed into deoxygenation zone 30, wherein at least a portion of the gas stream can be contacted with at least one catalyst composition under conditions sufficient to remove at least a portion of the oxygen from the gas stream and provide an oxygen-depleted gas stream in conduit 118. In some embodiments, the contacting can be carried out under conditions sufficient to remove at least about 80, at least about 90, at least about 95, at least about 97, at least about 99, at least about 99.5 percent of the total amount of oxygen introduced into deoxygenation zone 30 via conduit 116, based on the total amount of oxygen originally present in the gas stream in conduit 116. Accordingly, the oxygen-depleted gas stream withdrawn from deoxygenation zone 30 via conduit 118 can comprise less than about 20, less than about 10, less than about 5, less than about 2, less than about 1, less than about 0.5 percent of the total amount of oxygen originally introduced into deoxygenation zone 30 in the oxygen-containing feed gas stream in conduit 116.

The catalyst composition used to contact the feed gas stream introduced into deoxygenation zone 30 in conduit 116 can comprise at least one support and one or more catalytic metals. In some embodiments, the catalytic metal or metals may be impregnated onto at least a portion of the support material, while, in other embodiments, the catalytic metal or metals may be at least partially dispersed throughout the support material matrix. The support material of the catalyst composition can comprise material capable of withstanding the operating conditions within deoxygenation removal zone 30 while providing sufficient support and porosity to facilitate the necessary deoxygenation reactions. In some embodiments, the support material can be selected from the group consisting of silica, alumina, zinc oxide, and combinations thereof.

The catalytic metal employed by the deoxygenation catalyst composition in deoxygenation zone 30 can comprise any metal capable of facilitating removal of at least a portion of the oxygen from the incoming gas stream. In some embodiments, the catalytic metal used in deoxygenation zone 30 can be selected from the group consisting of copper, platinum, palladium and combinations thereof. In other embodiments, the catalytic metal can comprise copper. The amount of catalytic metal present within the catalyst composition may vary but, in some embodiments, may be at least about 1, at least about 2, at least about 2.5, at least about 3 and/or not more than about 20, not more than about 15, not more than about 10, not more than about 8, not more than about 6, not more than about 5 weight percent, based on the total weight of the catalyst composition. In other embodiments, the catalytic metal can be present in the catalyst composition in an amount of at least about 10, at least about 15, at least about 20, at least about 30 and/or not more than about 70, not more than about 65, not more than about 60, not more than about 50 weight percent, based on the total weight of the catalyst composition. In part, the amount of catalytic metal present may be impacted by the distribution of the catalytic metal over or within the support material.

According to some embodiments, the step of contacting the oxygen-containing feed gas stream with the catalyst composition may be carried out such that at least a portion of the catalytic metal remains in a reduced state during all, or substantially all, of the contacting step. This is contrary to many conventional deoxygenation processes, which permit an increasing amount of catalyst to become oxidized (i.e., a decreasing amount of catalyst in a reduced state) as oxygen is removed from the feed gas stream. In part, addition of hydrogen into the combined gas stream in conduit 116 and/or addition of hydrogen to deoxygenation zone 30 during the contacting step may help facilitate on-line reduction of at least a portion of the catalyst metal during the deoxygenation process. Although not wishing to be bound by theory, it is believed that, as the catalytic metal becomes oxidized during oxygen removal from the gas stream, at least a portion of the injected hydrogen may facilitate immediate or near immediate reduction of at least a portion of the oxidized catalyst, thereby retaining at least a portion of the catalytic metal in a reduced state. According to some embodiments of the present invention, at least about 10, at least about 20, at least about 30, at least about 40, at least about 50, at least about 60, at least about 70, at least about 80, at least about 90 percent of the total amount of catalytic metal of the catalyst composition remains in a reduced state during contacting. In one embodiment, less than about 30, less than about 20, less than about 10, or less than about 5 percent of the total amount of catalytic metal of the catalyst composition remains in an oxidized state during the contacting step.

In order to facilitate reduction of the catalytic metal within the deoxygenation zone while simultaneously removing oxygen from the feed gas stream, the temperature of deoxygenation zone 30 during contacting can be maintained at temperature of at least about 325° F., at least about 330° F., at least about 340° F., at least about 345° F., at least about 350° F., at least about 355° F., at least about 360° F., at least about 365° F., at least about 370° F., at least about 375° F., at least about 380° F., at least about 385° F., at least about 390° F., at least about 395° F., at least about 400° F. and/or not more than about 480° F., at least about 475° F., at least about 470° F., at least about 465° F., at least about 460° F., at least about 455° F., at least about 450° F., at least about 445° F., at least about 440° F., at least about 435° F., at least about 430° F., at least about 425° F. The contacting step may be carried out at a temperature in the range of from about 325° F. to about 480° F., about 340° F. to about 460° F., about 350° F. to about 450° F., or about 400° F. to about 425° F. The total pressure within deoxygenation zone 30 can be at least about 500, at least about 600, at least about 750, at least about 850, at least about 900 pounds per square inch (psi) and/or not more than about 2500, not more than about 2250, not more than about 2000, not more than about 1750, not more than about 1500 psi. In some embodiments, the desulfurized gas stream in conduit 112 and/or the combined gas stream in conduit 116 may be heated and/or compressed as needed in order to achieve the desired temperature and/or pressure for the contacting step.

The deoxygenation catalyst composition employed in deoxygenation zone 30 may be in any suitable form and can, in some embodiments, be arranged in one or more fixed bed reactors located within deoxygenation zone 30. According to some embodiments, deoxygenation zone 30 may include two or more fixed bed reactors arranged in series, such that the deoxygenated gas stream from the first, or lead, bed can be used as the feed stream to the second, or lag, bed. In another embodiment, deoxygenation zone 30 may include two fixed bed reactors arranged in parallel, such that one reactor can be configured to receive and contact the feed gas stream with the catalyst composition, while the other reactor is off line and is not receiving a feed gas stream. In addition to including the deoxygenation catalyst composition described above, one or more reactors utilized in deoxygenation zone 30 can include additional catalyst or sorbent materials located before, after, or amongst the deoxygenation catalyst to help remove one or more other components of the gas stream including, for example, sulfur-containing compounds and/or water.

In some embodiments of the present invention, the amount of hydrogen introduced into feed stream in conduit 112 and/or into desulfurization zone 30 can be adjusted during at least a portion of the contacting step carried out in desulfurization zone 30 in order to achieve a desired level of oxygen removal. According to some embodiments, at least a portion of the adjusting may be carried out to maintain the molar ratio of hydrogen to oxygen in the oxygen-containing feed gas stream in conduit 116 within about 10, within about 5, within about 2, or within about 1 percent of a controlled set point, which may fall within one or more of the ranges provided above. For example, in some embodiments, the controlled set point of the hydrogen to oxygen ratio in the feed stream in conduit 116 can be at least about 1.80:1, at least about 1.85:1, at least about 1.90:1 at least about 1.95:1 and/or not more than about 2.2:1, not more than about 2.15:1, not more than about 2.10:1, not more than about 2.05:1, not more than about 2.01:1.

According to some embodiments, at least a portion of the adjusting can be carried out to maintain the amount of hydrogen present in the oxygen-depleted stream exiting deoxygenation zone 30 via conduit 118 above a maximum upper threshold limit and/or below a minimum lower threshold limit. In the same or other embodiments, the adjusting of the hydrogen-to-oxygen ratio in the feed gas in conduit 116 can be carried out to maintain the amount of oxygen in the oxygen-depleted gas steam in conduit 118 above a maximum upper threshold limit and/or below a minimum lower threshold limit. In addition to adjusting amount of hydrogen introduced into the feed stream in conduit 116, the temperature of the feed stream and/or the overall flow rate of the combined feed gas stream in conduit 116 may also be adjusted in order to control the degree of oxygen removal achieved in deoxygenation zone 30. Specific embodiments of methods for controlling the operation of a deoxygenation reactor within deoxygenation zone 30 will now be discussed in further detail with reference to FIGS. 2 and 3.

Turning now to FIG. 2, one embodiment of a deoxygenation reactor 230 suitable for use in deoxygenation zone 30 of FIG. 1 is shown. Additionally, FIG. 3 provides a flow chart outlining the major steps of a method 300 of controlling a deoxygenation reactor including, for example, deoxygenation reactor 230 shown in FIG. 2. As shown by the embodiment of deoxygenation reactor 230 depicted in FIG. 2, an oxygen-containing feed gas stream in conduit 210 can be combined with hydrogen (or other reducing agent) in conduit 214, and the combined gas stream in conduit 216 can be introduced into a bed of deoxygenation catalyst 222 within deoxygenation reactor 230. The resulting oxygen-depleted gas stream in conduit 216 can then be withdrawn from an upper portion of deoxygenation reactor 230 and sent to further downstream processing, transportation, and/or storage.

As shown in FIG. 3, the first step 310 of method 300 for controlling the oxygen removal process carried out in the system of FIG. 2, is to determine a value for at least one parameter of the oxygen-depleted gas stream in conduit 218. Examples of parameters to be determined can include, for example, oxygen content of the oxygen-depleted gas stream, the hydrogen content of in the oxygen-depleted gas stream, the pH of the oxygen-depleted feed gas stream, and combinations thereof. Such parameters can be measured using, for example, on-line analyzers such as on-line pH analyzer 252 and on-line hydrogen and/or oxygen analyzer 254 shown in FIG. 2. Additionally, other methods of determining these parameters, such as, for example pH paper or hand-held gas monitoring devices such as DRAEGER tubes may also be used alone, or in combination with online measurements.

Once a value for a parameter of the oxygen-depleted gas stream has been determined, the measured value can be compared with a target value for that parameter to determine a difference, as represented by step 320 in FIG. 3. Subsequently, as shown by step 330, based on the difference, at least one of the parameters of the oxygen-containing feed gas stream in conduit 116 can be controlled in order to minimize the difference between the measured and target values for the selected parameter of the oxygen-depleted stream. Examples of parameters of the oxygen-containing feed gas stream that may be controlled can include, for example, the molar ratio of hydrogen to oxygen in the combined oxygen-containing gas stream, the temperature of the combined gas stream, or both the molar ratio of hydrogen to oxygen and the temperature of the combined gas stream. When the parameter of the oxygen-containing feed gas stream selected is the molar ratio of hydrogen to oxygen in the combined oxygen-containing gas stream, this parameter may be controlled by adjusting the amount of hydrogen injected into the oxygen-containing feed gas stream in conduit 210. Alternatively, or in addition, this parameter may also be controlled by adjusting the amount of oxygen in and/or the flow rate of the feed gas stream in conduit 210, although the latter may be more desirable from a practical standpoint.

The target value itself and how the one or more feed stream parameters are controlled to minimize the difference between the measured value and the target value can be dependent, at least in part, on the amount of hydrogen and oxygen in the combined oxygen-containing feed gas stream in conduit 216. The feed stream parameters may be controlled to maintain a non-stoichiometric ratio of hydrogen to oxygen, although the particular target values and methods of adjusting the feed gas parameters may depend on whether the combined oxygen-containing feed gas stream introduced into deoxygenation reactor 230 has a stoichiometric excess of hydrogen (i.e., a sub-stoichiometric amount of oxygen) or a sub-stoichiometric amount of hydrogen (i.e., a stoichiometric excess of oxygen). Specific examples of target values for the parameters of the oxygen-depleted gas stream, as well as methods of controlling the selected parameter of the oxygen-containing feed gas stream, for each of these situations will now be discussed in greater detail below.

According to some embodiments of the present invention, the oxygen-containing feed gas stream in conduit 216 shown in FIG. 2 can have a non-stoichiometric molar ratio of hydrogen to oxygen such that the hydrogen is present in the oxygen-containing feed gas stream in a sub-stoichiometric amount. According to one embodiment, the molar ratio of hydrogen to oxygen in the combined oxygen-containing stream in conduit 216 may be less than 2:1 and can be, for example, within one or more of the ranges described above with respect to the combined feed stream in conduit 218 of FIG. 2 measured in step 310 of method 300 depicted in FIG. 3. The parameter of the oxygen-depleted gas stream in conduit 216 of FIG. 2 may be the total oxygen content and the target value used for comparison to the measured value in step 320 may be a maximum oxygen limit and/or a minimum oxygen limit. When the target value is a maximum oxygen limit, the target value may be not more than about 25, not more than about 20, not more than about 15, not more than about 10, not more than about 5, not more than about 2 ppmw of oxygen, based on the total volume of the weight of the oxygen-depleted stream. When the target value is a minimum oxygen limit, the target value may be at least about 1, at least about 2, at least about 5 ppmw of oxygen, based on the total weight of the oxygen-depleted gas stream. Because hydrogen is introduced into deoxygenation reactor 230 in a sub-stoichiometric amount, the hydrogen content of the oxygen-depleted gas stream may be less than about 10, less than about 5, less than about 2, or less than about 1 ppmw, based on the total weight of the oxygen-depleted stream in conduit 218. In some embodiments, the oxygen-depleted stream in conduit 218 may comprise no hydrogen.

When the parameter of the oxygen-depleted gas stream in conduit 218 measured in step 310 includes total oxygen content, the oxygen content can be determined by using, for example, on-line analyzer 254 shown in FIG. 2. Once a value for the parameter has been measured, the measured value may be transmitted by, for example, a signal, shown in FIG. 2 as dashed line 280, to a control system 250, wherein it may be compared with a target value for oxygen content that is introduced into control system 250 by another signal represented by dashed line 282. The target value may be directly input by a user or it may originate from a set point generated from past process information or another source. Once control system 250 has received both the measured and target values for oxygen content of the oxygen-depleted gas stream in conduit 218 (or other measured parameter), it can compare the measured value to the target value to determine a difference.

Once a difference has been determined between the total oxygen content of the oxygen-depleted gas stream in conduit 218 and the target value provided to control system 250, at least one of the parameters of the combined feed stream in conduit 216 can be adjusted or controlled, as shown by step 330 of method 300. When the parameter of oxygen-depleted gas stream 218 measured in step 310 is the total oxygen content of the oxygen-depleted gas stream and the target value is a minimum oxygen content, the parameter of the combined feed gas stream controlled in step 330 can be the amount of hydrogen introduced into the feed gas stream in conduit 110. For example, if the difference between the measured oxygen content and the minimum target value is negative (i.e., the measured value is less than the minimum target value), then the difference can be minimized by reducing the amount of hydrogen in conduit 214 combined with the feed gas stream in conduit 210 by, for example, closing valve 258 shown in FIG. 2.

In the same or another embodiment, the target value compared to the measured oxygen content of the oxygen-depleted gas stream can be a maximum oxygen content. According to this embodiment, the controlling step 330 depicted in FIG. 3 can include adjusting the amount of hydrogen introduced into and/or the temperature of the feed gas stream in conduit 210. For example, when the difference between the measured oxygen content and the target value for maximum oxygen content in the oxygen-depleted gas stream in conduit 218 is positive (i.e., the measured value exceeds the target value), the controlling step 330 of method 300 may include increasing the amount of hydrogen added to the combined feed gas stream in conduit 216 by, for example, opening valve 258 shown in FIG. 2.

Additionally, or in the alternative, when difference between the measured oxygen content and the maximum oxygen content is positive (i.e., when the measured value exceeds the target value), the temperature of the combined gas stream in conduit 216 can also be increased to affect a reduction in the amount of oxygen in the oxygen-depleted gas stream in conduit 218. The use of feed gas temperature to control the oxygen content of the oxygen-depleted steam in conduit 218 can be used as needed, optionally in combination with the step of adjusting the amount of hydrogen added to the feed gas stream, until the temperature of the feed gas stream approaches a temperature of at least about 425° F., at least about 435° F., at least about 445° F., or at least about 450° F.

When the temperature of the feed gas stream in conduit 216 exceeds a temperature of approximately 450° F. and the measured oxygen content of the oxygen-depleted gas stream in conduit 218 exceeds the target value for maximum oxygen content, the catalyst composition in deoxygenation reactor 230 may require further reduction and/or replacement. According to the present invention, replacement and/or reduction of the catalyst may be due, at least in part, to poisoning of the catalyst by other contaminants, such as sulfur-containing compounds. Unlike many conventional deoxygenation processes, which require frequent catalyst change outs or treatment steps, the method of operation of the present invention substantially eliminates the need to replenish the catalyst composition due to oxygen-related contamination. If the deoxygenation zone includes only one reactor, the entire zone may need to be shut down during such a step. However, if deoxygenation zone includes two or more reactors, operated in parallel or series, at least one of the reactors may remain on-line and operating while the catalyst in one or more other reactors is changed out or reduced.

In contrast to conventional processes, the typical time intervals between required reduction or replacement of catalyst 222 of deoxygenation reactor 230 can be, for example, at least about 2 months, at least about 4 months, at least about 8 months, at least about 1 year and/or not more than about 5 years, not more than about 2.5 years, not more than about 2 years, not more than about 18 months, measured as time-on-stream. In contrast, many conventional deoxygenation processes used to treat similar feed streams have a far lower time-on-stream, sometimes on the order of a month or less.

According to other embodiments of the present invention, hydrogen may be present in the oxygen-containing feed gas stream in a stoichiometric excess. In these embodiments, the molar ratio of hydrogen to oxygen in the oxygen-containing gas stream in conduit 216 may be greater than about 2:1 and can be, for example, within one or more of the ranges described above. According to these embodiments, the parameter of the oxygen-depleted gas stream in conduit 216 measured during step 310 of method 300 may be the total hydrogen content and the target value used for comparison in step 320 may be a maximum hydrogen limit and/or a minimum hydrogen limit. When the target value includes a maximum hydrogen limit, the target value for the hydrogen in the oxygen-depleted stream may be not more than about 100, not more than about 75, not more than about 50, not more than about 25, not more than about 20, not more than about 10 ppmw, based on the total weight of the oxygen-depleted stream in conduit 218. When the target value for hydrogen content in the oxygen-depleted stream is a minimum hydrogen content, the target value may be at least about 1, at least about 2, at least about 5, or at least about 10 ppmw, based on the total weight of the stream. In some embodiments, the total oxygen content of stream in conduit 218 may be less than about 20, less than about 15, less than about 10, or less than about 5 ppmw, based on the total weight of the stream. In some embodiments, the deoxygenated stream in conduit 218 can comprise no oxygen.

When the parameter of the oxygen-depleted gas stream in conduit 218 measured in step 320 of method 300 includes total hydrogen content, the hydrogen content can be determined by using, for example, an on-line analyzer 254 shown in FIG. 2. In a similar manner as described previously, a value for the measured parameter may be transmitted by signal 280 shown in FIG. 2 to control system 250, wherein it may be compared with a target value introduced by another signal 282. Once a difference between the measured and target values has been determined, at least one of the parameters of the combined feed stream in conduit 216 can be adjusted, as shown by step 330 of method 300.

When the parameter of oxygen-depleted gas stream 218 measured in step 310 is the total hydrogen content and the target value is a minimum hydrogen content, the parameter of the combined feed gas stream controlled in step 330 may be the amount of hydrogen introduced into the feed gas stream in conduit 210. For example, if the difference between the measured hydrogen content and the minimum target value is negative (i.e., the measured value is less than the minimum target value), then the difference can be minimized by increasing the amount of hydrogen combined with the feed gas stream in conduit 210 by, for example, opening valve 258. Additionally, or in the alternative, the difference between the measured total hydrogen content and a minimum hydrogen content of the oxygen-depleted gas in conduit 218 can also be minimized by adjusting the temperature of the combined gas stream in conduit 216. For example, when difference between the measured oxygen content and the minimum hydrogen content is negative (i.e., the measured value is less than the minimum target value), the temperature of the combined gas stream in conduit 216 can be increased to affect additional reaction of the oxygen in the feed gas stream with the injected hydrogen.

When the measured parameter of the oxygen-depleted gas includes total hydrogen content, the target value can include a maximum hydrogen content. According to this embodiment, step 330 depicted in FIG. 3 can also include adjusting the amount of hydrogen introduced into the feed gas stream in conduit 210. For example, when the difference between the measured hydrogen content and the target value for maximum hydrogen content in the oxygen-depleted gas stream in conduit 218 is positive (i.e., the measured value exceeds the target value), step 330 of method 300 can include reducing the amount of hydrogen added to the combined feed gas stream in conduit 216 by, for example, closing valve 258. Additionally or alternatively, positive differences between the measured hydrogen content and the maximum hydrogen value can be reduced by reducing the temperature of the feed gas stream in conduit 216.

Additionally, the molar ratio of hydrogen to oxygen in the combined feed gas stream in conduit 216 can also be adjusted by adjusting the flow rate and/or oxygen content of the oxygen-containing feed gas stream in conduit 210. Because the oxygen content of the feed gas stream may be more difficult to control, increasing or decreasing the flow rate of the oxygen-containing stream in conduit 210 may also be used to adjust the molar ratio of hydrogen to oxygen in the combined feed stream in conduit 216 introduced into deoxygenation reactor 230.

In some embodiments, the parameter of the oxygen-depleted gas stream in conduit 218 measured in step 320 of method 300 can be pH, which can be determined by using, for example, on-line pH analyzer 252 shown in FIG. 2. In a similar manner as previously discussed, the measurement obtained by on-line pH analyzer 252 can be transmitted to control system 250 via signal 284 and compared to a target value introduced into control system 250 via signal 282. Thereafter, a difference can be determined between the measured and target pH values and one or more parameters of the combined feed gas stream in conduit 216 can be adjusted to minimize the difference. When the parameter of the oxygen-depleted gas stream in conduit 218 measured in step 310 is pH and the target value is a minimum pH, the parameter of the combined feed gas stream in conduit 216 to be adjusted in step 320 can be temperature. For example, if the difference between the measured pH value and the minimum pH value is negative (i.e., if the measured value is less than the minimum target value), the temperature of the combined gas stream in conduit 216 can be increased. In some embodiments, the minimum pH of the oxygen-depleted gas stream in conduit 218 can be at least about 5, at least about 5.1, at least about 5.25 and/or not more than about 6.5, not more than about 6.0, not more than about 5.75.

Referring again to FIG. 3, in some embodiments, steps 310 through 330 of method 300 may be repeated one or more times in order to effectively minimize the difference between the measured and target values. The steps of method 300 may be repeated until the difference between the measured and target value is not more than about 10, not more than about 5, not more than about 2, not more than about 1 percent of the target value. Similarly, method 300 may not even be initiated until the difference between the measured and target values is at least about 1, at least about 2, at least about 5 percent of the target value. The steps of method 300 described according to several embodiments of the present invention may be repeated at least 1, at least 2, at least 3 and/or not more than about 20, not more than about 10, not more than about 5 times. In other embodiments when method 300 is carried out using control system 250, the method may be carried out on a continuous basis, as needed, when deoxygenation reactor 230 is in operation. Further, although illustrated in FIG. 2 as being carried out by control system 250, it is also possible that at least a part, or all, of the steps of method 300 may be performed manually.

Referring back to FIG. 1, the deoxygenated stream 118 withdrawn from deoxygenation zone 30 can have a total oxygen content of less than about 25, less than about 20, less than about 10, less than about 5 ppmw, based on the total weight of the stream. In some embodiments, the oxygen-depleted gas stream in conduit 118 can comprise at least about 1, at least about 2, at least about 5 ppmw of hydrogen and/or not more than about 100, not more than about 75, not more than about 50, not more than about 25 ppmw of hydrogen, based on the total weight of the deoxygenated stream in conduit 118. Additionally, the pH of the deoxygenated stream can be at least about 5, at least about 5.5, or at least about 6.

As shown in FIG. 1, upon removal from deoxygenation zone 118, the oxygen-depleted gas stream may then be subjected to further separation or purification processes in product separation zone 40. In some embodiments, at least a portion of product separation zone 40 can be operated under cryogenic conditions and/or may be configured to remove one or more components from the deoxygenated stream, including, for example nitrogen, helium, C2 and heavier hydrocarbons and the like. The specific configuration of columns or processes within product separation zone 40 is not limited and may depend, at least in part, on the type and source of the feed gas in conduit 110 and the desired products to be provided via conduit 122 and others (not shown in FIG. 1).

Although described herein with respect to a natural gas stream, it should also be understood that the processes for removing oxygen and the method for controlling the oxygen removal processes described above may be applicable to various other types of feed gas streams, particularly hydrocarbon-containing feed gas streams having hydrocarbon contents within the ranges described previously.

Example

Several trial runs were conducted using a lab-scale deoxygenation reactor to determine the ability of several different catalyst compositions to remove oxygen from a natural gas feed stream. For each run, the reactor, which was formed from 6 inch, schedule 80 pipe, was loaded with upper and lower support beds including ½ inch, ¼ inch, and ⅛ inch ceramic support balls arranged in 6-inch layers. Between the support beds, the reactor was loaded with 1 cubic foot of catalyst material, as described below.

The first trial, Run 1, was conducted by passing oxygen-containing natural gas having an average flow rate of 0.146 MMSCFD and an average temperature of 88° F. through a fixed bed of 2 to 4 mm beads of 0.3 weight percent palladium on alumina catalyst. For Run 1, the feed gas had an average oxygen content of 2554 ppm and a hydrogen content of 0.01 mole percent. The composition of the oxygen-containing feed gas used in Run 1 is summarized in Table 1, below. Upon passage of the gas through the deoxygenation reactor, a sample of the oxygen-depleted gas stream was withdrawn and its composition determined using ASTM D-5443. Additional detailed component analyses were performed using a multi-isomer analysis by GC and a GC-MS qualitative analysis. The results of the compositional analyses are provide in Table 2, below. A second trial, Run 2, was carried out on the same reactor system, under similar conditions and using a stream of oxygen-containing natural gas having a similar composition. The actual composition of the feed gas used during Trial 2 is summarized in Table 1 below. During Run 2, the natural gas feed stream, which had an average flow rate of 0.135 MMSCFD and an average temperature of 65° F., was passed through a fixed bed of the same palladium catalyst used during Run 1. Compositions of the product gas collected during Run 2 are summarized in Tables 1 and 2, below.

Two additional trial runs, Runs 3 and 4, were both carried out in a similar manner to Runs 1 and 2 described previously, except the natural gas was passed through a fixed bed of copper-containing catalyst according to one embodiment of the present invention. The copper-containing catalyst used during Runs 3 and 4 included 3×3 tablets of 40 percent copper (II) oxide, with the balance of zinc oxide and alumina. During Run 3, the average contacting temperature between the natural gas stream and the catalyst was at 370° F., while the contacting temperature during Run 4 was increased to 395° F. The composition of the feed and product gases for Runs 3 and 4 are also summarized in Tables 1 and 2, below.

TABLE 1 Composition of Inlet and Outlet Streams of Deoxygenation Reactor with Various Catalysts Run 1 Run 2 Run 3 Run 4 Inlet Outlet Change Inlet Outlet Change Inlet Outlet Change Inlet Outlet Change Component Mole % Mole % Mole % Mole % Mole % Mole % Mole % Mole % Mole % Mole % Mole % Mole % Nitrogen 8.51 9.54 1.03 8.83 9.16 0.33 8.13 7.71 −0.42 8.13 8.22 0.09 Carbon Dioxide 0.86 0.86 0.00 0.82 0.86 0.04 0.82 0.84 0.01 0.82 0.83 0.01 Helium 0.35 0.32 −0.04 0.34 0.35 0.01 0.34 0.33 −0.01 0.34 0.33 −0.01 Hydrogen 0.01 0.01 0.00 0.82 0.68 −0.14 1.20 1.05 −0.15 1.20 0.97 −0.23 Oxygen 2554 ppm 0.14 — 0.10 0.02 −0.08 0.09 0.01 −0.08 0.09 0.01 −0.08 Methane 68.70  65.89 −2.80 68.37 69.51 1.14 67.80 67.21 −0.59 67.80 69.76 1.96 Ethane 7.85 8.22 0.37 8.08 7.91 −0.18 7.86 8.43 0.58 7.86 7.80 −0.06 Propane 7.16 7.86 0.70 6.91 6.77 −0.14 7.20 7.88 0.68 7.20 6.74 −0.46 Iso-Butane 1.37 1.56 0.19 1.21 1.17 −0.05 1.41 1.43 0.02 1.41 1.19 −0.22 N-Butane 3.36 3.80 0.43 3.09 2.56 −0.53 3.52 3.51 −0.01 3.52 2.83 −0.69 Iso-Pentane 0.76 0.80 0.04 0.69 0.54 −0.15 0.82 0.76 −0.06 0.82 0.63 −0.19 N-Pentane 0.74 0.76 0.02 0.65 0.45 −0.20 0.75 0.72 −0.04 0.75 0.58 −0.18 Hexane+ 0.33 0.39 0.05 0.13 0.05 −0.08 0.15 0.14 −0.01 0.15 0.11 −0.04

TABLE 2 Detailed C6+ Composition of Inlet and Outlet Streams of Deoxygenation Reactor with Various Catalysts Run 1 Run 2 Run 3 Run 4 Inlet Outlet Change Inlet Outlet Change Inlet Outlet Change Inlet Outlet Change Component Mole % Mole % Mole % Mole % Mole % Mole % Mole % Mole % Mole % Mole % Mole % Mole % 2,2-dimethylbutane 0.0030 0.0101 0.0071 0.0003 0.0000 −0.0003 0.0001 0.0003 0.0002 0.0001 0.0001 0.0000 2,3-dimethylbutane 0.0056 0.0228 0.0172 0.0022 0.0003 −0.0019 0.0050 0.0082 0.0032 0.0050 0.0016 −0.0034 2-methylpentane 0.0369 0.0300 −0.0069 0.0094 0.0030 −0.0064 0.0091 0.0203 0.0112 0.0091 0.0098 0.0007 3-methylpentane 0.0382 0.0223 −0.0159 0.0256 0.0087 −0.0169 0.0221 0.0359 0.0138 0.0221 0.0248 0.0027 Methylcyclopentane 0.0372 0.0803 0.0431 0.0209 0.0060 −0.0149 0.0365 0.0221 −0.0144 0.0365 0.0169 −0.0196 Benzene 0.0027 0.0048 0.0020 0.0016 0.0006 −0.0010 0.0005 0.0002 −0.0003 0.0005 0.0002 −0.0003 Cyclohexane 0.0262 0.0194 −0.0068 0.0110 0.0051 −0.0059 0.0023 0.0017 −0.0006 0.0023 0.0031 0.0008 n-hexane 0.1277 0.1114 −0.0163 0.0483 0.0144 −0.0339 0.0644 0.0461 −0.0183 0.0644 0.0440 −0.0204 2,2-dimethylpentane 0.0023 0.0070 0.0047 0.0001 0.0002 0.0001 0.0011 0.0002 −0.0009 0.0011 0.0012 0.0001 2,4-dimethylpentane 0.0057 0.0118 0.0061 0.0005 0.0014 0.0009 0.0006 0.0001 −0.0005 0.0006 0.0006 0.0000 3-methylhexane 0.0057 0.0078 0.0020 0.0010 0.0029 0.0019 0.0007 0.0004 −0.0003 0.0007 0.0007 0.0000 1,t3-dimethylcyclopentane 0.0007 0.0009 0.0002 0.0000 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,c3-dimethylcyclopentane 0.0006 0.0005 −0.0001 0.0001 0.0004 0.0003 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,t2-dimethylcyclopentane 0.0002 0.0004 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Toluene 0.0008 0.0016 0.0008 0.0001 0.0004 0.0003 0.0004 0.0002 −0.0002 0.0004 0.0000 −0.0004 Methylcyclohexane 0.0049 0.0038 −0.0011 0.0012 0.0020 0.0008 0.0029 0.0035 0.0006 0.0029 0.0030 0.0001 Ethylcyclopentane 0.0000 0.0031 0.0031 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-heptane 0.0217 0.0345 0.0128 0.0019 0.0024 0.0005 0.0024 0.0022 −0.0002 0.0024 0.0027 0.0003 2,4 + 2,5-dimethylhexane 0.0003 0.0030 0.0026 0.0000 0.0000 0.0000 0.0002 0.0003 0.0001 0.0002 0.0005 0.0003 1,t2,c4-trimethylcyclopentane 0.0001 0.0002 0.0001 0.0001 0.0000 −0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,t2,c3-trimethylcyclopentane 0.0002 0.0002 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 2-methylheptane 0.0002 0.0015 0.0013 0.0000 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,c2,t4-trimethylcyclopentane 0.0002 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 3-methylheptane 0.0006 0.0002 −0.0004 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,c3-dimethylcyclohexane 0.0003 0.0001 −0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,t4-dimethylcyclohexane 0.0004 0.0000 −0.0004 0.0001 0.0000 −0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 methyl-ethylcyclopentanes 0.0002 0.0000 −0.0002 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,C4&1,t3-dimethylcyclohexane 0.0006 0.0000 −0.0006 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,c2-dimethylcyclohexane 0.0007 0.0001 −0.0006 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Ethylcyclohexane 0.0002 0.0001 −0.0001 0.0000 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Ethylbenzene 0.0003 0.0004 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 m + p-xylene 0.0005 0.0005 −0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 o-xylene 0.0001 0.0016 0.0014 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-octane 0.0060 0.0093 0.0033 0.0004 0.0002 −0.0002 0.0000 0.0000 0.0000 0.0000 0.0003 0.0003 Trimethylhexanes 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Dimethylheptanes 0.0002 0.0000 −0.0002 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Isopropylcyclopentane 0.0001 0.0000 −0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-propylcyclopentane 0.0001 0.0000 −0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 3-methyloctane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Trimethylcyclohexanes 0.0001 0.0001 −0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Isopropylbenzene 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Isopropylcyclohexane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-propylcyclohexane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-propylbenzene 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 m-ethyltoluene 0.0002 0.0000 −0.0002 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 p-ethyltoluene 0.0001 0.0000 −0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,3,5-trimethylbenzene + 4,5- 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 methylnonane o-ethyltoluene + 3-methylnonane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,2,3-trimethylbenzene 0.0000 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-nonane 0.0002 0.0001 −0.0001 0.0001 0.0000 −0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 2-methylnonane 0.0001 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 tert-butylbenzene 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,2,4-trimethylbenzene 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Isobutylcyclohexane + 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 t-butylcyclohexane isobutylbenzene 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 sec-butylbenzene 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-butylcyclohexane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,3-diethylbenzene 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,2-diethylbenzene + 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-butylbenzene 1,4-diethylbenzene 0.0000 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-decane 0.0008 0.0004 −0.0004 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 unidentified C9 naphthenes + C10 0.0002 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 paraffins unidentified C10 aromatics + C11 0.0001 0.0002 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 paraffins Ungrouped C10's 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-undecane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 isododecane+ 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

The preferred forms of the invention described above are to be used as illustration only, and should not be used in a limiting sense to interpret the scope of the present invention. Obvious modifications to the exemplary embodiments, set forth above, could be readily made by those skilled in the art without departing from the spirit of the present invention.

The inventors hereby states their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set forth in the following claims.

Claims

1. A process for removing oxygen from a natural gas stream, said process comprising:

(a) combining an oxygen-containing natural gas stream with a reducing agent to form a combined gas stream; and
(b) contacting at least a portion of said combined gas stream with at least one copper-containing catalyst in a deoxygenation zone to thereby provide an oxygen-depleted gas stream, wherein said contacting is carried out under conditions sufficient to maintain at least a portion of the copper of said copper-containing catalyst in a reduced state during said contacting.

2. The process of claim 1, wherein said contacting is carried out under conditions sufficient to maintain at least 40 percent of the copper of said copper-containing catalyst in a reduced state during said contacting of step (b).

3. The process of claim 1, wherein said reducing agent comprises hydrogen.

4. The process of claim 1, wherein said contacting of step (b) is carried out at an average temperature of at least about 350° F. and not more than about 480° F.

5. The process of claim 1, wherein the molar ratio of hydrogen to oxygen in said combined gas stream is not 2:1.

6. The process of claim 5, wherein the molar ratio of hydrogen to oxygen in said combined gas stream is less than 2:1.

7. The process of claim 1, wherein the pH of said oxygen-depleted gas stream is at least 5.

8. The process of claim 1, wherein said combining of step (a) is carried out prior to said contacting of step (b).

9. The process of claim 1, wherein said oxygen-containing natural gas stream comprises oxygen in an amount of at least about 50 parts per million by weight (ppmw) and not more than about 15,000, ppmw, based on the total weight of said oxygen-containing natural gas stream.

10. The process of claim 1, further comprising, during at least a portion of said contacting of step (b), adjusting the amount of hydrogen combined with said oxygen-containing natural gas stream.

11. The process of claim 1, wherein said oxygen-containing natural gas stream comprises C1 to C6 hydrocarbons in an amount of at least about 25 weight percent, based on the total weight of said oxygen-containing natural gas stream.

12. The process of claim 1, wherein said oxygen-containing natural gas stream comprises less than about 15 weight percent of one or more inert gases selected from the group consisting of nitrogen, neon, xenon, argon, helium, krypton, radon, and combinations thereof.

13. The process of claim 1, further comprising, prior to said combining of step (b), removing at least a portion of one or more sulfur-containing compounds from a natural gas stream to thereby provide a desulfurized natural gas stream, wherein said oxygen-containing natural gas stream combined with said reducing agent comprises said desulfurized natural gas stream.

14. A process for removing oxygen from a natural gas stream, said process comprising:

(a) introducing oxygen-containing natural gas and hydrogen into a deoxygenation zone, wherein said hydrogen is present in said deoxygenation zone in a non-stoichiometric amount relative to the amount of oxygen present in said deoxygenation zone; and
(b) removing at least a portion of the oxygen from the natural gas with at least one catalyst in said deoxygenation zone to thereby provide an oxygen-depleted natural gas stream, wherein the average temperature of said deoxygenation zone is less than about 480° F.

15. The process of claim 14, wherein said hydrogen is present in a sub-stoichiometric amount relative to the amount of oxygen present in said deoxygenation zone.

16. The process of claim 14, wherein said catalyst is a copper-containing catalyst.

17. The process of claim 16, wherein the average temperature of said deoxygenation zone is at least 325° F.

18. The process of claim 14, wherein said oxygen-depleted gas stream comprises less than about 25 ppmw of oxygen, based on the total weight of said oxygen-depleted gas stream.

19. The process of claim 14, further comprising, measuring the hydrogen content and/or oxygen content of said oxygen-depleted gas stream and, based on the measured value of said hydrogen and/or oxygen content of said oxygen-depleted gas stream, adjusting the amount of hydrogen introduced into said deoxygenation zone and/or adjusting the average temperature of said deoxygenation zone.

20. The process of claim 14, wherein said oxygen-depleted gas stream comprises less than 20 percent of the total amount of oxygen introduced into the deoxygenation zone.

21. A method for controlling a process for removing oxygen from a gas stream, said method comprising:

(a) combining an oxygen-containing feed gas stream with a hydrogen stream to thereby provide a combined feed gas stream; and
(b) passing at least a portion of said combined feed gas stream through a deoxygenation zone, wherein said passing comprises contacting said combined feed gas stream with at least one catalyst to remove at least a portion of the oxygen from said combined feed gas stream and provide an oxygen-depleted gas stream;
(c) measuring a value for at least one parameter of said oxygen-depleted gas stream;
(d) comparing the measured value for said parameter of said oxygen-depleted gas stream determined in step (c) with a target value for said parameter of said oxygen-depleted gas stream to determine a difference; and
(e) based on said difference, controlling at least one parameter of said combined gas stream in order to minimize said difference.

22. The method of claim 21, wherein said parameter of said oxygen-depleted gas stream measured in step (c) is selected from the group consisting of the amount of oxygen in said oxygen-depleted gas stream, the amount of hydrogen in said oxygen-depleted gas stream, the pH of said oxygen-depleted gas stream, and combinations thereof.

23. The method of claim 21, wherein said parameter of said combined gas stream controlled in step (e) is selected from the group consisting of the molar ratio of hydrogen to oxygen of said combined gas stream, the temperature of said combined gas stream, and both the molar ratio of hydrogen to oxygen and the temperature of said combined gas stream.

24. The method of claim 21, wherein said measuring of step (c) includes determining a value for the oxygen content of said oxygen-depleted gas stream, and wherein step (d) comprises comparing the measured value for said oxygen content of said oxygen-depleted gas stream determined in step (c) with a target value for said oxygen content of said oxygen-depleted gas stream to determine said difference.

25. The method of claim 24, wherein said target value is a maximum oxygen limit, wherein said oxygen content of said oxygen-depleted gas stream measured in step (c) is higher than said maximum oxygen limit, wherein said controlling of step (e) includes increasing the molar ratio of hydrogen to oxygen in said combined gas stream and/or increasing the temperature of said combined gas stream.

26. The method of claim 24, wherein said target value is a minimum oxygen limit, wherein the oxygen content of said oxygen-depleted gas stream measured in step (c) is lower than said minimum oxygen limit, wherein said controlling of step (e) includes reducing the molar ratio of hydrogen to oxygen in said combined gas stream.

27. The method of claim 21, wherein said measuring of step (c) includes determining a value for the hydrogen content of said oxygen-depleted gas stream and wherein said comparing of step (d) comprises comparing the value for said hydrogen content of said oxygen-depleted gas stream measured in step (c) with a target value for said hydrogen content of said oxygen-depleted gas stream to determine said difference.

28. The method of claim 21, wherein said measuring of step (c) includes determining a value for the pH said oxygen-depleted gas stream and wherein said comparing of step (d) comprises comparing said value for said pH of said oxygen-depleted gas stream determined in step (c) with a target value for said pH of said oxygen-depleted gas stream to determine said difference.

29. The method of claim 21, further comprising, repeating steps (a) through (e) until said difference has a value that is not more than about 10 percent of said target value.

30. The method of claim 21, wherein at least a portion of steps (a) through (e) are carried out with an automated control system.

Patent History
Publication number: 20150203772
Type: Application
Filed: Jan 21, 2014
Publication Date: Jul 23, 2015
Applicant: BADGER MIDSTREAM ENERGY, LP (HOUSTON, TX)
Inventors: Kurt R. Schoch (Amarillo, TX), David J. Artrip (Conroe, TX)
Application Number: 14/160,157
Classifications
International Classification: C10L 3/10 (20060101);