PRETREATMENT OF FATS AND OILS IN THE PRODUCTION OF BIOFUELS

Abstract

Methods are disclosed for the treatment of feedstocks comprising a fatty acid- or triglyceride-containing component to remove contaminants that are detrimental to the conversion of such feedstocks to hydrocarbons, and especially biofuel fractions such as diesel or aviation biofuels. Contaminants contributing to the presence of trace elements in animal fats and/or plant oils, as components of feedstocks, hinder the ability to catalytically convert these feedstocks, for example by hydroprocessing, to biofuels.

Description

STATEMENT OF PRIORITY

This application claims priority to U.S. Provisional Application No. 61/428,640 which was filed on Dec. 30, 2010, the contents of which are hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

Aspects of the invention relate to the pretreatment of feedstocks comprising a fatty acid- or triglyceride-containing component (e.g., an animal fats or a plant oil) to remove contaminants such as phosphorous that are detrimental to hydroprocessing operations used to convert such feedstocks to hydrocarbon-containing biofuels (e.g., a diesel biofuel or an aviation biofuel).

DESCRIPTION OF RELATED ART

Environmental concerns over fossil fuel greenhouse gas (GHG) emissions have led to an increasing emphasis on renewable energy sources. The production of biofuels is expanding at a rapid pace worldwide as a result of commitments to GHG reduction, including the climate agreement at Kyoto and associated European Union directives. Increasing petroleum prices and government regulations are providing further incentives for viable alternatives to fossil-derived energy sources. Ultimately, the widespread adoption of biofuels will depend on the development of new technologies to produce high quality transportation fuels from biologically derived feedstocks, having a significant organic oxygen content. The new biofuels must be compatible with the existing, petroleum-derived fuel specifications and infrastructure. In view of these objectives, the art has recognized the need for economically attractive processing routes to convert renewable carbon sources into high quality hydrocarbon fuels or fuel blendstocks, which are comparable to their petroleum-derived counterparts.

A proposed pathway for the production of biofuels, including diesel fuel and aviation fuel fractions, is through the hydroprocessing of fatty acids and/or trigylcerides derived from renewable feedstocks, including animal fats and plant oils. The common feature of these biological feedstock components is that they are composed of triglycerides and free fatty acids (FFA), both of which contain aliphatic carbon chains having from 6 to 24 carbon atoms. Triglycerides in fats and oils are namely triesters or glycerol and three fatty acids, and these trigylcerides have the following structure

where R₁, R₂, and R₃ represent C₆-C₂₄ hydrocarbon radicals, which are typically straight chained and either saturated or unsaturated (i.e., mono-, di-, or poly-unsaturated). The fatty acids (or FFA), which are not esterified in a triglyceride, therefore have the formula R—(C═O)—OH, where R may be a hydrocarbon radical R₁, R₂, or R₃ as described with respect to the formula above. Some mono- and diglycerides may be contained in these renewable feedstock components instead of, or in addition to, the triglycerides.

Conversion of these fatty acid- or triglyceride-containing feedstock components to biofuels suitable for use as transportation fuels, or otherwise for blending into such fuels with a petroleum-derived component, generally involves a number of hydroprocessing reactions (e.g., hydrogenation and deoxygenation, which includes decarboxylation, decarbonylation, and/or hydrodeoxygenation, as well as other possible reactions including hydrocracking and hydroisomerization) to convert the triglycerides and FFA into hydrocarbons having an acceptable molecular weight (and boiling point) range for a given type of fuel. Representative conversion processes are described, for example, in US Publication Nos. 2009/0077865, 2009/0077866, 2009/0077868, 2009/0229172, 2009/0229174, 2009/0283442, 2009/0300970, 2009/0321311, 2010/0076238, and 2010/0160698.

The development of fuel compositions, and particularly those useful as transportation fuels, which are derived at least partly from feedstocks having renewable components, is therefore an ongoing objective of major industrial importance. Compositions, or fractions useful for blending into compositions, most desirably have characteristics (e.g., energy value, distillation curve, and density, in addition to organic oxygen and aromatic content) that are representative of their counterpart petroleum-derived compositions or blending fractions, used for the same intended purpose (e.g., as a diesel fuel). Methods for producing such compositions and fractions in the most economical manner possible represent ongoing objectives in the development of biofuel alternatives.

SUMMARY OF THE INVENTION

The present invention is associated with the discovery of important benefits that result from the treatment of feedstocks comprising a fatty acid- or triglyceride-containing component, in order to remove contaminants that have been found to be detrimental in the conversion of such feedstocks to hydrocarbons, and especially biofuel fractions such as diesel or aviation biofuels. Without being bound by theory, contaminants contributing to the presence of trace elements in animal fats and/or plant oils, as components of feedstocks, hinder the ability to catalytically convert these feedstocks to hydrocarbons using hydroprocessing. For example, certain elements and compounds containing these elements (e.g., phosphorous and phosphorous-containing compounds) poison or reduce the activity of hydroprocessing catalysts, thereby shortening their useful life and consequently increasing the overall cost of biofuel production. Treating methods to reduce certain contaminants of the fatty acid- or triglyceride-containing component (and therefore contaminants of the feedstock), to the greatest extent possible, therefore provide important commercial advantages.

Embodiments of the present invention are therefore directed to methods for treating a feedstock comprising a fatty acid- or triglyceride-containing component. Representative components comprise one or more contaminants, which may, for example, be selected from the group consisting of calcium (Ca), iron (Fe), magnesium (Mg), sodium (Na), phosphorous (P), and potassium (K). The method comprises contacting the feedstock with an ion exchange resin to provide a treated feedstock having a reduced concentration of at least one of the contaminants.

Particular embodiments of the present invention are directed to methods for making a hydroprocessed biofuel from a feedstock comprising, consisting of, or consisting essentially of, an animal fat, a plant oil, or a mixture thereof. The methods comprise contacting the feedstock with one or more ion exchange resins, including a cation exchange resin and/or an anion exchange resin, with the use of both types of resins (e.g., in series) according to a representative embodiment. A preferred resin, which may be used alone or optionally in combination with one or more other resins, is a macroreticulated, strong acid cation exchange resin. The contacting between the feedstock and resin(s) provides a treated feedstock having a reduced concentration of one or more contaminants as discussed above and, for example, selected from the group consisting of Ca, Fe, Mg, Na, P, and K. The methods may further comprise contacting the treated feedstock with hydrogen and a hydroprocessing catalyst to provide a hydroprocessed product, and fractionating the hydroprocessed product to recover the hydroprocessed biofuel.

Further embodiments of the present invention are directed to hydroprocessed biofuels made according to these methods (e.g., using fractionation to recover the biofuel from a hydroprocessed product), in addition to biofuel compositions made by blending the hydroprocessed biofuel with a petroleum-derived fuel (e.g., present in the composition in an amount from about 1% to about 99% by weight). The biofuels, and fuel compositions comprising these biofuels, advantageously exhibit greatly reduced greenhouse gas (GHG) emissions, compared to their petroleum-derived counterparts, based on a lifecycle assessment (LCA) up to and including the ultimate combustion of the fuel composition by the end user. For vegetable oils and animal fats, the GHG emissions associated with obtaining these feedstock components are in many cases considered negligible, as these biofuel sources are otherwise normally waste products of foods already produced for human and animal consumption. The biofuels and biofuel compositions have suitable characteristics, in terms of overall makeup (e.g., relatively large, minimally required, amounts of hydrocarbons within a particular boiling range) and in terms of quality (e.g., relatively small, maximally allowed, amounts of thermally unstable compounds such as oxygenates) for use as a fuel composition or a fuel composition blending component.

These and other embodiments and aspects relating to the present invention are apparent from the following Detailed Description.

DETAILED DESCRIPTION

Representative fatty acid- or triglyceride-containing components, present in feedstocks suitable for the present invention, may be animal fats, plant oils, or a mixture of fats and oils. Such components, beneficially comprising renewable carbon, typically contain both fatty acids and triglycerides, with the possible additional presence of monoglycerides and diglycerides that may be treated and hydroprocessed as well, as discussed in greater detail below. The fatty acid- or triglyceride-containing component may also include derivative classes of compounds such as fatty acid alkyl esters (FAAE), which embrace fatty acid methyl esters (FAME) and fatty acid ethyl esters (FAEE). Examples of animal fats include lard, tallow, train oil, milk fat, fish oil, sewage sludge, and/or recycled fats of the food industry, including various waste streams such as yellow and brown greases. Examples of plant oils include rapeseed oil, corn oil, colza oil, canola oil, tall oil, sunflower oil, soybean oil, hempseed oil, olive oil, linseed oil, mustard oil, palm oil, peanut oil, castor oil, coconut oil, jatropha oil, camelina oil, salicornia oil, pennycress oil, algal oil, and mixtures thereof. Mixtures of one or more of these animal fats and one or more of these plant oils can also be used. The fatty acids and triglycerides of the typical animal fat or plant oil contain aliphatic hydrocarbon chains in their structures, as described above, with the majority of these chains having from about 8 to about 24 carbon atoms. Most of these fats and oils contain significant proportions (e.g., at least about 30%, or at least about 50%) of aliphatic hydrocarbon chains with 16 and 18 carbon atoms.

The feedstock may contain entirely the fatty acid- or triglyceride-containing component (i.e., may comprise 100% of this component). Otherwise, this component may be mixed with other renewable and/or non-renewable (i.e., fossil-derived) components of the feedstock, which may similarly benefit from the treatment method and/or hydroprocessing. The fatty acid- or triglyceride-containing component is present in the feedstock generally in an amount of at least about 10% by weight (e.g., from about 10% to about 100% by weight), typically at least about 50% by weight (e.g., from about 50% to about 99.5% by weight), and often at least about 80% by weight (e.g., from about 80% to about 99% by weight).

Animal fats and/or plant oils, as fatty acid or triglyceride-containing components, typically contain a higher oxygen content (e.g., about 5-25% organic oxygen) and a lower energy content (e.g., about 15-20% lower), relative to petroleum-derived liquid fuel fractions. Other properties of the fatty acids and triglycerides in these fats and oils render them generally less favorable, compared to petroleum-derived fractions, for blending into a transportation fuel composition. These characteristics, however, may be improved using hydrotreating, hydrocracking, and/or hydroisomerization, as specific hydroprocessing reactions, to remove oxygen (by conversion to water) and convert the remaining aliphatic hydrocarbon portions of the fatty acids and triglycerides to hydrocarbons with a lower average molecular weight and possibly a greater degree of branching (or content of isoparaffins), in order to meet specifications for blending into distillate fuels such as diesel and aviation fuel. Hydroprocessing of the fatty acid- or triglyceride-containing feedstock component therefore upgrades this component, which, following separation (e.g., by fractionation) of the resulting, hydroprocessed product, can provide a hydroprocessed biofuel meeting composition and quality standards applicable to petroleum-derived components. According to embodiments of the invention, a biofuel that does not require further blending with petroleum-derived hydrocarbons, such as an on-spec diesel biofuel, is obtained after feedstock treatment (or pretreatment), hydroprocessing, and fractionation, as described herein.

Hydroprocessing of feedstocks comprising a fatty acid- or triglyceride-containing component is improved if the quality of the feedstock is upgraded according to treatment (or pretreatment) methods described herein. In particular, these methods purify such feedstocks by separating one or more contaminants comprising a heteroatom (i.e., an atom other than C, H, O) that is not present in the fatty acid or triglyceride structure, as discussed above. Representative contaminants that are separated according to methods described herein therefore include alkali metals, alkaline earth metals, transition metals, or non-metals other than C, H, or O. A particular non-metal of interest is phosphorous. The contaminants are often present in ionic form, but may also be in elemental form, or otherwise covalently bonded in compounds containing the contaminant elements. In any case, the presence of these contaminants can be detected, for example, based on the characteristic emission wavelengths of the elements in ionized form using inductively coupled plasma (ICP) analytical techniques.

The removal of one or more of these contaminants therefore provides a treated feedstock having a reduced amount or concentration of at least one contaminant, such that removal may be evidenced by a trace element analysis of the feedstock both before and after contact with the ion exchange resin (or combination of resins, such as both a cation exchange resin and an anion exchange resin). Importantly, the separated elements are in general detrimental to the overall activity and useful life of the hydroprocessing catalyst, which often represents a major expense (e.g., due to the use of catalytic metals including, in some cases, noble metals and/or the use of support materials such as zeolites) in the production of hydroprocessed biofuels. Representative elements that are desirably separated, at least partially, from the feedstock include Ca, Fe, Mg, Na, P, and K. Representative feedstocks, for example, comprise a total concentration of these elements that is generally from about 10 ppm to 200 ppm, typically from about 20 ppm to about 150 ppm, and often from about 30 ppm to about 100 ppm, by weight. The concentration of P (phosphorous) in the feedstock, which can particularly adversely impact the performance of a hydroprocessing catalyst, is generally from about 5 ppm to about 150 ppm, typically from about 10 ppm to about 100 ppm, and often from about 15 ppm to about 50 ppm by weight. A particular analytical technique for the measurement of the concentrations of these elements, both prior and subsequent to treatment, is inductively coupled plasma atomic emission spectrometry (ICP-AES), according to ASTM D5600-09.

The separation of one or more contaminants is carried out by contacting the feedstock with an ion exchange resin, and preferably a strong base or weak base anion exchange resin or a strong acid cation exchange resin. Combinations of these resins may also be used, with combinations including the separate use (e.g., in series) of two or more ion exchange resins in discreet zones or beds within the same or separate columns. Combinations also include mixtures, for example in various mixing ratios, of ion exchange resins in a resin bed of ion exchange resin. Representative strong base and weak base anion exchange resins have quaternary ammonium functional groups and amine functional groups, respectively. Representative strong acid cation exchange resins have sulfonic acid functional groups. Using known ion exchange techniques, the exchangeable sites of these resins may be in any desired form for use in the treatment methods, although the sites of base resins are preferably in their hydroxide (—OH) forms and the sites of acid resins are preferably in their hydrogen (—H) form.

Contacting between the feedstock comprising a fatty acid- or triglyceride-containing component and the ion exchange resin may be performed batchwise or continuously, with the main consideration being a sufficient residence time within the resin bed to achieve a desired degree of separation of one or more contaminants. If continuous contacting is used, a representative liquid hourly space velocity (LHSV) is from about 0.05 hr⁻¹ to about 10 hr⁻¹. As is understood in the art, the LHSV, or volumetric liquid flow rate over the catalyst bed divided by the bed volume, represents the number of equivalent resin bed volumes of feedstock processed every hour. LHSV is therefore related to the inverse of the feedstock residence time in the bed. In view of the present disclosure, those having skill in the art will be able to select the appropriate contacting conditions to achieve a desired level of contaminant removal for a particular feedstock composition and ion exchange resin. Generally, the treated feedstock obtained from the treatment methods will have a total concentration of Ca, Fe, Mg, Na, P, and K that is reduced by at least about 35% (e.g., from about 35% to about 99%), typically at least about 50% (e.g., from about 50% to about 95%), and often by at least about 75% (e.g., from about 75% to about 90%), relative to the feedstock prior to this treatment. The total concentration of these contaminants in the treated feedstock is generally less than about 50 ppm (e.g., from about 1 ppm to about 50 ppm) by weight, typically less than about 20 ppm (e.g., from about 1 ppm to about 20 ppm) by weight, and often less than about 10 ppm (e.g., from about 1 ppm to about 10 ppm) by weight. Advantageously, the concentration of phosphorous (P) in the treated feedstock is reduced by at least about 40% (e.g., from about 40% to about 99.9%), typically at least about 60% (e.g., from about 60% to about 99%), and often by at least about 90% (e.g., from about 90% to about 98%), relative to the feedstock prior to this treatment. The concentration of P in the treated feedstock is generally less than about 20 ppm (e.g., from about 0.1 ppm to about 20 ppm) by weight, typically less than about 5 ppm (e.g., from about 0.1 ppm to about 5 ppm) by weight, and often less than about 3 ppm (e.g., from about 0.1 ppm to about 3 ppm) by weight. The treatment methods, however, generally do not substantially impact the feedstock composition in other respects, including its organic oxygenate content, which typically ranges from about 5% to about 25% by weight in both the untreated and treated feedstock.

Over extended period of feedstock treatment, the ion exchange resin(s) become “spent” by virtue of having all or a substantial portion of their useable ion exchange sites occupied by the separated contaminants. At some point, therefore, it becomes necessary remove the spent resin(s) from their treatment service and regenerate the resin(s) by displacing the separated contaminants into a regenerant solution that is passed over the spent resin(s), subjecting these resin(s) to ions (e.g., hydroxide ions or hydrogen ions) that can restore the active exchange sites for continued use in feedstock contaminant removal. Regenerant solutions for strong and weak base anion exchange resins, for example, include sodium hydroxide, ammonium hydroxide, and/or sodium carbonate. Regenerant solutions for strong acid cation exchange resins include, for example, sulfuric acid and/or other strong acids. In the case of regenerating resins used to contact fatty acid- or triglyceride-containing components, an intermediate resin wash (e.g., with an aliphatic alcohol such as methanol) may be beneficial prior to introducing the regenerant. In a representative operation, a swing-bed system may be employed, such that some ion exchange resin, in at least a first bed, may be used for a period of time until it becomes spent, at which time at least a second bed of fresh ion exchange resin, after having been regenerated, is placed in service while the first bed is regenerated. The condition of the resin(s), in terms of ion exchange capacity remaining until a spent condition is attained, can be monitored by the amount(s) or percentages of any one or more contaminants that “break through” the bed without being separated.

Particular embodiments of the invention, utilizing the treatment (or pretreatment) methods described above, relate to novel production methods for fuel compositions that are at least partially, but often completely, derived from renewable carbon sources. These sources include a fatty acid- or triglyceride-containing component and optionally other components, as discussed above, which may likewise be derived from renewable carbon. Representative methods comprise contacting the treated feedstock, obtained from the above treatment methods, with hydrogen to provide a hydroprocessed product. This subsequent hydroprocessing of the treated feedstock beneficially reduces its total oxygen content and increases its total heating value.

Hydroprocessing which includes hydrotreating (e.g., hydrodeoxygenation) and preferably both hydrotreating and hydrocracking reactions (optionally with hydroisomerization), involves contacting the treated feedstock with hydrogen and in the presence of a suitable hydroprocessing catalyst, generally under conditions sufficient to convert a large proportion of the organic oxygenates in the treated feedstock to CO, CO₂ and water that are easily separated from the hydroprocessed product. The hydrogen may be present in one or more streams and may be substantially pure (e.g., as makeup or fresh hydrogen) or relatively impure (e.g., as recycle hydrogen), as long as sufficient hydrogen partial pressure is maintained in the hydroprocessing reaction environment to achieve the desired performance parameters, for example conversion, catalyst stability, and product isoparaffin content (in the case of production of a high quality diesel biofuel including catalytic hydroisomerization and associated conditions).

Typical hydroprocessing conditions include a temperature (e.g., average catalyst bed temperature, as measured in fixed bed systems) from about 40° C. (104° F.) to about 700° C. (1292° F.), and often from about 200° C. (302° F.) to about 600° C. (1112° F.), and a hydrogen partial pressure from about 700 kPa (100 psig) to about 21 MPa (3000 psig), and often from about 3.1 MPa (400 psig) to about 10.5 MPa (1500 psig). In addition to pressure and temperature, the residence time of the treated feedstock (which may be hydroprocessed in conjunction with other feedstocks) and hydrogen in the catalyst bed or reaction zone can also be adjusted to increase or decrease the reaction severity and consequently the quality of the resulting hydroprocessed product. With all other variables unchanged, lower residence times are associated with lower reaction severity. Therefore, increasing the LHSV, or flow rate of the treated feedstock processed over a given quantity of catalyst, directionally decreases residence time and consequently the extent of the hydrotreating, hydrocracking, and/or hydroisomerization reactions. A typical range of LHSV according to the present invention is from about 0.1 hr⁻¹ to about 20 hr⁻¹, often from about 0.5 hr⁻¹ to about 10 hr⁻¹. The quantity of hydrogen introduced to the hydroprocessing reactor(s) or reaction zone(s) may be based on the stoichiometric amount needed to completely convert the oxygen present in the treated feedstock to H₂O. In representative embodiments, the reaction may be carried out in the presence of hydrogen in an amount ranging from about 90% to about 600% of the stoichiometric amount.

Suitable hydroprocessing catalysts have a catalytic metal, which may be noble or non-noble. Representative catalysts include those comprising at least one Group VIII metal for catalyzing the desired hydroprocessing reactions, such as iron, cobalt, and nickel (e.g., cobalt and/or nickel) and/or at least one Group VI metal, such as molybdenum and tungsten. Noble metals, such as ruthenium, palladium, and platinum, may also be used. A representative hydroprocessing catalyst comprises a metal selected from the group consisting of ruthenium, platinum, palladium, iron, cobalt, nickel, molybdenum, tungsten, and mixtures thereof (e.g., a mixture of cobalt and molybdenum). A Group VIII metal, when used, is typically present in the catalyst in an amount ranging from about 2 to about 20 weight percent, and normally from about 4 to about 12 weight percent, based on the volatile-free catalyst weight. A Group VI metal is typically present in an amount ranging from about 1 to about 25 weight percent, and normally from about 2 to about 25 weight percent, also based on the volatile-free catalyst weight. A volatile-free catalyst sample may be obtained by subjecting the catalyst to drying at 200-350° C. (392-662° F.) under an inert gas purge or vacuum for a period of time (e.g., 2 hours), so that water and other volatile components are driven from the catalyst. In general, the catalytic metal, or combination of metals, of a suitable hydroprocessing catalyst is disposed on a high surface area support material such as a refractory inorganic oxide (e.g., silica, alumina, titania, and/or zirconia). A carbon support may also be used. It is within the scope of the invention to use more than one type of catalyst for carrying out the hydroprocessing reactions, and different catalysts may be used in the same or different reaction vessels. Two or more catalyst beds of the same or different catalyst and one or more quench points may also be utilized in a reaction vessel or vessels to provide the hydroprocessed product.

After reaction of the pretreated feedstock in the presence of hydrogen, a catalyst, and hydroprocessing conditions as described above, the total effluent (or hydroprocessed product) obtained directly from the hydroprocessing reactor(s) or reaction zone(s), prior to any downstream separation and purification steps, has an organic oxygen content that is generally reduced from about 90% to about 99.9%, relative to the oxygen content of the pretreated feedstock. Organic oxygen originally present in the fatty acids and triglycerides of the feedstock is therefore generally converted, to a large extent, to water that is easily separated from the desired hydrocarbons recovered from the hydroprocessed product. Accompanying its decrease in organic oxygen is an increase in the heating value, on a mass basis, of the hydroprocessed product. This heating value increases typically by a factor ranging from about 1.5 to about 3, compared to that of the feedstock, either before or after pretreatment.

Fractionation or other separation methods may then be used to separate a desired hydroprocessed biofuel from hydrogen, light hydrocarbons, water, and other lower value byproducts present in the total effluent (or hydroprocessed product). At least a portion of the separated hydrogen, optionally together with light hydrocarbons, may be recycled to the hydroprocessing reactor(s) or reaction zone(s), such that the combined gas stream of make-up hydrogen (which may be of varying purity) and recycle hydrogen is sufficient to achieve a hydrogen partial pressure within the ranges described above. The hydroprocessed biofuel, obtained after this separation of byproducts, comprises predominantly hydrocarbons, typically at least about 90% hydrocarbons (e.g., from about 90% to about 99.9% hydrocarbons) by weight, and often at least about 97% hydrocarbons (e.g., from about 97% to about 99.5% hydrocarbons) by weight.

The organic oxygenate content of the hydroprocessed product, as well as the hydroprocessed biofuel, is generally less than about 0.1% by weight and typically less than 0.01% by weight, with lower amounts of organic oxygen being generally associated with more severe hydroprocessing (hydrodeoxygenation) conditions (e.g., higher temperatures and hydrogen partial pressures, and/or lower LHSV). While a reduction in organic oxygenates directionally increases heating value, this improvement in the quality of the hydroprocessed biofuel is achieved at the expense of increased energy required for the hydroprocessing reactions. Optimization of the organic oxygen content is therefore possible, depending on the intended end use. If desired, for example, further processing may be used to reduce the organic oxygenate content to less than 10 ppm, and even less than 1 ppm by weight, rendering the hydroprocessed biofuel suitable as a blending component for a number of transportation fuels, including aviation fuel.

The hydroprocessed product may in general be separated using any of a number of separation steps, or a combination of separation steps, to recover a hydroprocessed biofuel. Representative separation steps include those employing a single-stage or multiple stages of vapor-liquid equilibrium, such as flash or distillation (fractionation) separations, respectively. These separations may also be performed in the presence of flowing gas (e.g., hydrogen) to effect stripping of all or a portion of the hydroprocessed product. Any of these flash separation, distillation, and/or stripping operations may be carried out in conjunction with absorption. Various separation methods, using one or more of these steps and preferably comprising flash separating (e.g., in the presence of flowing hydrogen to effect hot hydrogen stripping) and fractionating the hydroprocessed product, are suitable for recovering the hydroprocessed biofuel. This biofuel is namely a hydroprocessed product fraction (e.g., a hydroprocessed diesel biofuel, a hydroprocessed aviation biofuel, a hydroprocessed naphtha biofuel, etc.) comprising hydrocarbons having normal boiling points characteristic of their counterpart petroleum-derived fractions used for the same application. Therefore, following separation of the hydroprocessed product (e.g., by fractionation), the resulting hydroprocessed biofuel, having a significant quantity of paraffinic and iso-paraffinic hydrocarbons, may be used in neat form, for example as a diesel fuel. It is also possible to blend, with a hydroprocessed biofuel, one or more petroleum-derived fractions, in a subsequent blending step.

Further embodiments of the invention therefore relate to methods of preparing biofuel compositions. Representative methods comprise blending a hydroprocessed product fraction, and particularly a hydroprocessed biofuel made according to methods described herein, with a petroleum-derived component. Such fuel compositions incorporate a hydroprocessed biofuel and therefore have a carbon content that is at least partly derived from renewable carbon. The carbon footprint of the biofuel is thereby reduced according to U.S. government greenhouse gas (GHG) emission accounting practices, in which emissions associated with the combustion of fuels derived from natural oils (i.e., animal fats or plant oils), are not reported in the lifecycle assessment (LCA) of the GHG emission value, since carbon from these oils is renewed over a very short time frame compared to petroleum-derived components. Of particular interest with respect to the biofuel compositions described herein are distillate fuels such as diesel and aviation fuels.

Representative biofuel compositions associated with the present invention may be prepared by blending the hydroprocessed biofuels, made according to the methods described above, with a petroleum-derived diesel or aviation fuel, or other petroleum-derived fraction, which is present in the resulting fuel composition in an amount from about 30% to about 98% by weight. According to particular fuel compositions, (i) generally from 1 to about 50%, and typically from 1 to about 30%, of the hydroprocessed biofuel fraction (e.g., a hydroprocessed distillate biofuel) by weight is blended with (ii) generally from about 30% to about 99%, and typically from about 50% to about 98% of a petroleum-derived fraction (e.g., a petroleum-derived distillate fuel) by weight.

Overall, aspects of the invention are associated with methods for pretreating a feedstock comprising a fatty acid- or triglyceride-containing component, wherein the resulting pretreated feedstock may be hydroprocessed with improved performance, due to the removal of contaminants that are detrimental to the hydroprocessing catalyst. Further aspects are associated with hydroprocessed biofuels made by a combination of pretreatment and hydroprocessing, as well as fuel compositions (e.g., diesel or aviation fuel compositions) exhibiting a reduced carbon footprint, comprising these hydroprocessed biofuels. Those having skill in the art, with the knowledge gained from the present disclosure, will recognize that various changes could be made in these methods, as well as in compositions made by these methods, without departing from the scope of the present invention. Mechanisms used to explain theoretical or observed phenomena or results, shall be interpreted as illustrative only and not limiting in any way the scope of the appended claims.

The following example is set forth as representative of the present invention. The example is not to be construed as limiting the scope of the invention as other equivalent embodiments will be apparent in view of the present disclosure and appended claims.

EXAMPLE

A representative plant oil, namely camelina oil, as a feedstock for biofuel production, was analyzed for trace metals by inductively coupled plasma atomic emission spectrometry (ICP-AES). Three jars were then filled with 100 ml each of this feedstock, and 10 g of a different ion exchange resin was added to each jar. In particular, these resins were (1) a strong base anion exchange resin having quaternary ammonium functional groups in the hydroxide form, (2) a weak base anion exchange resin having amine functional groups, and (3) a strong acid cation exchange resin having sulfonic acid functional groups in the hydrogen form. The jars containing resin and camelina oil were subsequently sealed and shaken manually for 5 seconds, before being placed onto a mechanical shaker. After 3 days of mechanical shaking, the resulting, treated oil samples were filtered from the resins and submitted for the same ICP-AES analysis. The feedstock analyses, both prior to and after treatment, as well as the types of resins used, are summarized in Table 1 below. The total percentage removal of Ca, Fe, Mg, Na, P, and K combined, as well as the percentage removal of phosphorous (P), are also included in this table.

TABLE 1
Performance of Ion Exchange Resins in Contaminant Removal
		Treated w/	Treated w/	Treated w/
	Camelina	Strong Base	Weak Base	Strong Acid
Contam-	Oil	Anion Exch.	Anion Exch.	Cation Exch.
inant	(feedstock)	Resin	Resin	Resin
Ca	17.6	17.7	5.6	9.2
Fe	0.6	0.7	0.3	0.6
Mg	9.6	9.7	3.3	2.3
Na	11.7	11.4	1.8	3.5
P	36.2	9.8	7.6	1.8
K	1.2	<0.1	<0.1	<0.1
Total	76.9	49.3	18.6	17.5
% Removal		35.9	75.8	77.2
(total)
% Removal		72.9	79.0	95.0
(P)

The results in Table 1 above demonstrate the effectiveness of the various ion exchange resins for removing contaminants, and particularly phosphorous, from a plant oil that may be hydroprocessed to provide a biofuel. The removal of phosphorous and metallic contaminants can beneficially improve the activity and useful life of a typical hydroprocessing catalyst.

Claims

1. A method for treating a feedstock comprising a fatty acid- or triglyceride-containing component comprising one or more contaminants, the method comprising contacting the feedstock with an ion exchange resin to provide a treated feedstock having a reduced concentration of at least one of the contaminants.

2. The method of claim 1, wherein the one or more contaminants is an alkali metal, an alkaline earth metal, a transition metal, or a non-metal other than C, H, or O.

3. The method of claim 2, wherein the one or more contaminants is selected from the group consisting of Ca, Fe, Mg, Na, P, and K.

4. The method of claim 1, wherein the fatty acid or triglyceride-containing component is an animal fat, a plant oil, or a mixture thereof.

5. The method of claim 4, wherein the animal fat is selected from the group consisting of lard, tallow, train oil, milk fat, fish oil, grease, sewage sludge, and mixtures thereof.

6. The method of claim 4, wherein the plant oil is selected from the group consisting of rapeseed oil, corn oil, colza oil, canola oil, tall oil, sunflower oil, soybean oil, hempseed oil, olive oil, linseed oil, mustard oil, palm oil, peanut oil, castor oil, coconut oil, jatropha oil, camelina oil, salicornia oil, pennycress oil, algal oil, and mixtures thereof.

7. The method of claim 1, wherein the ion exchange resin is a strong base or weak base anion exchange resin, a strong acid cation exchange resin, or a combination thereof.

8. The method of claim 7, wherein the strong base anion exchange resin has quaternary ammonium functional groups.

9. The method of claim 7, wherein the weak base anion exchange resin has amine functional groups.

10. The method of claim 7, wherein the strong acid cation exchange resin has sulfonic acid functional groups.

11. The method of claim 3, wherein the treated feedstock has a total concentration of Ca, Fe, Mg, Na, P, and K contaminants that is reduced by at least about 35% relative to the feedstock.

12. The method of claim 1, wherein the treated feedstock has a concentration of P that is reduced by at least about 70% relative to the feedstock.

13. The method of claim 1, further comprising contacting the treated feedstock with hydrogen under catalytic hydroprocessing conditions to provide a hydroprocessed product.

14. The method of claim 13, wherein the contacting with hydrogen under catalytic hydroprocessing conditions results in both hydrotreating and hydrocracking reactions.

15. The method of claim 13, further comprising fractionating the hydroprocessed product to recover a hydroprocessed biofuel.

16. The method of claim 15, wherein the hydroprocessed biofuel is a hydroprocessed diesel biofuel or a hydroprocessed aviation biofuel.

17. A method for making a hydroprocessed biofuel from a feedstock comprising an animal fat, a plant oil, or a mixture thereof, the method comprising:

(a) contacting the feedstock with a macroreticulated, strong acid cation exchange resin to provide a treated feedstock having a reduced concentration of one or more contaminants selected from the group consisting of Ca, Fe, Mg, Na, P, and K;

(b) contacting the treated feedstock with hydrogen and a hydroprocessing catalyst to provide a hydroprocessed product; and

(c) separating the hydroprocessed product to recover the hydroprocessed biofuel.

18. The method of claim 17, wherein the cation exchange resin is in the hydrogen form.

19. The method of claim 17, further comprising blending the hydroprocessed biofuel with from about 1% to 99% by weight of a petroleum-derived fuel.

20. A biofuel composition made by the method of claim 19.