BIOFUEL PRODUCTION USING NANOZEOLITE CATALYST
A method of converting biovapors to biofuel includes directing biovapors derived from decomposition of biomass, said biovapors comprising at least C5 and C6 compounds, into a catalytic reaction chamber; and contacting the biovapors with a catalyst composition comprising a nanozeolite.
The present application claims the benefit of priority to co-pending U.S. Patent Application No. 62/191,166, filed on Jul. 10, 2015, the content of which is hereby incorporated by reference herein in its entirety.
The present application is related to International Patent Application No. PCT/US14/62256, which was filed on Oct. 24, 2014, and which claims the benefit of U.S. Patent Application No. 61/895,905 filed on Oct. 25, 2013, the content of which is hereby incorporated by reference herein in its entirety.
INCORPORATION BY REFERENCEAll patents, patent applications and publications cited herein are hereby incorporated by reference in their entirety in order to more fully describe the state of the art as known to those skilled therein as of the date of the invention described herein.
TECHNICAL FIELDThe present disclosure relates generally to catalysts and processes for use in making renewable fuels, and more particularly to catalysts for the chemical conversion of biomass to renewable fuels and other useful chemical compounds.
Zeolites have been known for some time as catalysts in hydrocarbon conversions. Zeolites are crystalline aluminosilicates with a characteristic porous structure made up of a three dimensional network of SiO4 and AlO4 tetrahedra cross-linked by shared oxygen atoms with a variety of structures and aluminum contents. Other atoms can be incorporated into the zeolite lattice, such as phosphorus, germanium, gallium or boron. The catalytic activity of zeolites relies on their acidity. Non-tetravalent atoms within the tetrahedral array, such as trivalent aluminum, gallium or boron, create a positive charge deficiency, which can be compensated by a cation such as H+, ammonium, etc. In addition, the pores and channels through the crystalline structure of the zeolite enable the materials to act as selective molecular sieves particularly if the dimensions of the channels fall within a range which enables the diffusion of large molecules to be controlled. Thus, acidic zeolites can be used as selective catalysts.
Zeolites have been used for the conversion of organic molecules into gasoline range hydrocarbons. Methanol or ethanol can be converted to gasoline range of hydrocarbons via dehydration and oligomerization. H-ZSM-5 (10-membered ring) is used as a catalyst for methanol to gasoline process by ExxonMobil Research and Engineering Company in the MTG (methanol to gasoline) process.
Numerous processes have been investigated for the conversion of biomass feedstocks into biofuel. Such processes include gasification, slow pyrolysis and fast pyrolysis. The products from these reactions tend to be of low quality and are not useful, without significant post-processing, as transportation fuels. In particular, catalytic fast pyrolysis employs pyrolysis of biomass over a catalyst in a single reactor. The pyrolysis takes place at high temperatures, e.g., greater than 600° C., and results in of low aromatic yield and unacceptably high coking (greater than 30% and even greater than 50%).
Systems describing the catalytic conversion of biomass into fuels and other useful chemical compounds also have been previously described. Some such methods involve subjecting volatile components derived from biomass to one or more catalysts such as dehydration catalysts, aromatization catalysts, and gas upgrading catalysts. The process products tend to be of better quality than the simple thermal processes. However, the same catalyst used for gasoline formation can also lead to polymerization of olefins leading to coking, e.g., the build-up of a high carbon content residue on the zeolite catalyst sites and the deactivation of the catalyst. Coking can increase the frequency of catalyst reactivation, increasing production costs and reducing yield and productivity.
Catalytic processes for conversion of biomass to biofuel that improve catalyst life, reduce coking and increase fuel yield are desired.
SUMMARYA nanozeolite catalyst for use in the production of biofuel from biomass is described. In one aspect, a method of converting biovapors to biofuel includes directing biovapors derived from decomposition of biomass, said biovapors including at least C5 and C6 compounds, into a catalytic reaction chamber separate from the decomposed biomass; and contacting the biovapors with a catalyst composition including a nanozeolite. In one or more embodiments, the C5 and C6 compounds are cyclic.
In one or more embodiments, at least 60% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 2 μm, or at least 80% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 2 μm, or at least 90% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 2 μm, at least 25% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 1 μm, at least 40% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 1 μm, or at least 50% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 1 μm.
In any preceding embodiment, the nanozeolite crystallite has a silica to alumina ratio in the range of 50-250.
In any preceding embodiment, the nanozeolite catalyst comprises ZSM-5 and is for example a nanozeolite selected from a group consisting of ZSM-5, beta-zeolite, modernite-zeolite, zeolite-Y and mixtures thereof.
In any preceding embodiment, the catalyst composition further includes a non-zeolite binder.
In any preceding embodiment, the biovapors are contacted with a catalyst composition heated at a temperature in the range of 350° C.-500° C.
In any preceding embodiment, the biovapors are contacted with a catalyst composition at a weight hourly space velocity of 0.1-1.0 hr-1.
In any preceding embodiment, contacting the biovapors with a catalyst composition includes sequentially contacting the biovapors with two or more catalysts compositions.
In any preceding embodiment, the catalyst compositions are different, or the catalyst compositions are the same.
In any preceding embodiment, the catalyst compositions are subjected to different reaction conditions, and for example, the temperature of the catalyst conditions are different, or the temperature of the first catalyst composition is lower than the temperature of the second catalyst composition.
In any preceding embodiment, the second catalyst is a guard catalyst and the biovapors are contacted with the guard catalyst prior to contacting the biovapors with the nanozeolite catalyst composition, and for example, the guard catalyst is selected from the group consisting of a dehydration catalyst, decarboxylation catalyst, decarbonylation catalyst, and deoxygenation catalyst, or the guard catalyst is selected from the group consisting of (1) heterogeneous heteropolyacids (HPAs) and their salts, (2) natural clay minerals, such as those containing alumina or silica (including zeolites), (3) cation exchange resins, (4) metal oxides, (5) mixed metal oxides, (6) inorganic acids or metal salts derived from these acids such as metal sulfides, metal sulfates, metal sulfonates, metal nitrates, metal phosphates, metal phosphonates, metal molybdates, metal tungstates, metal borates, and (7) combinations of groups 1 to 6, or the guard catalyst comprises a nanozeolite, or the guard catalyst is selected from the group consisting of (1) alkali and alkaline metal or metal oxides or metal hydroxides supported catalysts, where in the alkali metals are Lithium, Sodium, potassium, magnesium, strontium, cesium and Rubidium (2) basic transition metal supported catalysts such as zinc oxide, copper oxides etc., (3) hydrotalcites or layered double hydroxide catalysts such as Mg6Al2(OH)16CO3.4H2O and (4) solid super basic catalysts such as KF on europium oxide, KF on hydrotalcites.
In any preceding embodiment, the biovapors are obtained from a decomposition process selected from chemical, thermal and biological decomposition processes.
In any preceding embodiment, the thermal process includes pyrolysis, or the chemical process comprises acid hydrolysis.
In one or more embodiments, pyrolysis includes heating biomass at temperatures of less than 600° C. to generate pyrolysis vapors.
In one or more embodiments, water or steam is injected into biomass during pyrolysis.
In one or more embodiments, the ratio of steam to biomass is in the range of 0.5 to 0.9 (wt/wt).
In one or more embodiments, the fuel yield is greater than 6.5%, or greater than 7.0% or greater than 7.5%, or greater than 8.0% or greater than 8.5% by weight of input biomass, or in the range of 6.5-12% by weight of input biomass.
In one or more embodiments, the reaction is carried out without addition of a cosolvent, such as methanol, ethanol or dimethyl ether.
In one or more embodiments, the fuel product contains less than 3 wt % benzene and less than 1 wt % durene.
In another aspect, a catalyst system for conversion of biovapors into biofuel, includes a catalyst reactor comprising at least two catalyst compositions positioned and arranged for sequential contact with a vapor, wherein the first catalyst comprises a guard catalyst selected to reduce oxygen content and increase the hydrogen content of an oxygenated C5 and C6 compound-containing biovapor, and wherein the second catalyst comprises a nanozeolite catalyst wherein at least 90% of the zeolite crystallites have a largest dimension of less than or equal to 200 μm.
In one or more embodiments, at least 25% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 1 μm, or at least 40% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 1 μm, or at least 50% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 1 μm, or the nanozeolite crystallite has a silica to alumina ratio in the range of 50-250.
In one or more embodiments, the nanozeolite catalyst comprises ZSM-5, and for example, the nanozeolite is selected from a group consisting of ZSM-5, beta-zeolite, modernite-zeolite, zeolite-Y and mixtures thereof.
In one or more embodiments, the catalyst composition further comprises a non-zeolite binder.
In one or more embodiments, the first and second catalyst compositions are different.
In one or more embodiments, the first and second catalyst compositions are the same.
These and other aspects and embodiments of the disclosure are illustrated and described below.
The invention is described with reference to the following figures, which are presented for the purpose of illustration only and are not intended to be limiting.
In the Drawings:
The specification discloses compositions and methods for the production of aromatic and olefinic compounds, and more specifically biofuels, using a decomposition process to generate biovapors from biomass and a catalytic process to convert the biovapors into biofuels. In other embodiments, processes for converting biovapors into fuel in a high yield, low coking process are disclosed.
In one aspect, certain catalysts or combination of catalysts have been discovered that can increase yields of fuel products and/or reduce coke formation and/or control product formation (e.g., higher production of aromatics and/or olefins relative to other fuels) as compared to processes using conventional catalysts. In other aspects, certain reaction conditions are disclosed that, in combination with certain catalysts or combination of catalysts, lower yields of coke formation and/or provide more controlled product formation (e.g., higher production of aromatics and/or olefins relative to other fuels) as compared to processes lacking these reaction conditions.
In one aspect, a method for producing biofuels or biofuel components from biovapors employs a catalyst composition comprising a nanozeolite. “Biofuel” as used herein is understood to mean a composition derived from a non-petroleum biomass having a mixture of hydrocarbons in the correct chain lengths, chain conformations, and compound ratios to be used as a fuel or a fuel component. A fuel is a composition useful as a fuel in internal combustion engines, such as commonly found in transportation vehicles (e.g., automobiles, airplanes, trains, and heavy machinery), the composition including, but not limited to, a composition classifiable as a jet engine fuel, a diesel engine fuel, or a gasoline engine fuel. A “fuel component” is a composition containing some or all of the components of a fuel (in the same or different proportions from those found in a fuel) that can be blended with other ingredients to obtain a fuel.
It has been surprisingly discovered that the zeolite catalysts having a crystallite size of less than 2 microns produce fuel yields, lower yields of coke formation and/or provide more controlled product formation (e.g., higher production of aromatics and/or olefins relative to other fuels) as compared to processes using conventional catalysts. It has been surprisingly discovered that the silica alumina ratio (SAR) of the nanozeolite catalyst composition can be selected to further enhance the yield and composition of the biofuel and reduction of coking. Thus, for example, a zeolite crystallite size of less than 2 microns and silica alumina ratio (SAR) in the range of 50 to 250 can be used. Moreover, the two properties exhibit a non-linear relationship, such that an optimal silica alumina ratio (SAR) can be identified for any given zeolite crystallite size. Conversely, an optimal zeolite crystallite size can be identified for any given silica alumina ratio (SAR).
In one aspect, the method of converting biovapors to biofuel includes directing biovapors derived from decomposition of biomass into a catalytic reaction chamber. The decomposition process is selected to produce an oxygenated feedstock rich in C5 and C6 compounds, such as sugars and anhydrosugars. The biovapors contact and react with a catalyst composition including a nanozeolite, wherein the nanozeolite has a crystallite size and a silica to alumina ratio (SAR) selected to maximize fuel yield and reduce coking.
CatalystThe zeolite catalyst is a nanozeolite. As defined herein a nanozeolite is a zeolite in which at least 60% of the nanozeolite catalyst crystallites have a largest dimension of less than 200 μm. In other embodiments, at least 70% or at least 80% or at least 90% or at least 95% of the nanozeolite catalyst crystallites have a largest dimension of less than or equal to 200 μm or any range bounded by any stated value. In one or more embodiments, at least 25% of the nanozeolite catalyst crystallites have a largest dimension of less than or equal to 100 μm. In other embodiments, at least 40% or at least 50% of the nanozeolite catalyst crystallites have a largest dimension of less than or equal to 100 μm or any range bounded by any value stated. In one particular catalyst composition, at least 90% of the zeolite crystallites have a largest dimension of less than 200 μm and at least 50% of the zeolite crystallites have a largest dimension of less than or equal to 100 μm. In some embodiments, the zeolite has an average crystallite size of between 1 μm and 2 μm, or between 750 nm and 1 μm, or between 500 nm and 750 nm, or between 250 nm and 500 nm, or between 125 and 250 nm, or between 25 and 125 nm or any range bounded by any value stated herein. In one particular embodiment, the zeolite has an average crystallite size in the range of 250 nm-2 μm. In other embodiments, at least 50% or at least 60% or at least 70% or at least 80% or at least 90% of the nanozeolite catalyst crystallites have a largest dimension in the range of 250 nm-2 μm. In one or more embodiments, the zeolite crystallite size is predominantly less than 1 micron, or less than 900 nm, or less than 800 nm, or less than 700 nm or less than 600 nm, or less than 500 nm, or less than 200 nm, less than 150 nm, less than 100 nm and even less than 50 nm and as small as 40 nm or any range bounded by any of the stated values.
Zeolite materials are typically provided as particles, which can be further incorporated into the extrudate catalyst compositions described herein. Although the particles can be on the micron scale, e.g., 10 μm-500 μm, or 50-300 μm, or 100-200 μm average particle size, the particles can encompass a number of smaller crystalline domains or crystallites. These crystallites contain the active domains that are the sites for catalytic activity.
In one or more embodiments, the catalyst provides a fuel yield of at least 6.5 wt % (preferably 7-8 wt %) based on processed biomass and/or a coking rate of less than 3 wt % (preferably 1-2 wt %) based on processed biomass.
In one or more embodiments, the nanozeolite has a silica to alumina ratio (SAR) in the range of 50 to 180 and the nanozeolite catalyst has a zeolite crystallite size elected to provide a fuel yield of at least 6.5 wt % (preferably 7-8 wt %) based on processed biomass and/or a coking rate of less than 3 wt % (preferably 1-2 wt %) based on processed biomass. In one or more embodiments, the alumina ratio (SAR) is in the range of 50 to 250 (mol/mol), or 80 to 200 (mol/mol), or 90 to 180 (mol/mol), or 120 to 150 (mol/mol) or any range bounded by any of the stated values.
The catalyst composition used in the conversion of biomass to biofuel according to one or more embodiments can be in the form of an extrudate, e.g., extruded pellets, and the extrudate can include a zeolite catalyst and a non-zeolite binder. The catalyst composition includes a zeolite having a microporous crystalline phase distributed in a non-zeolite binder in a configuration that provides mesoporosity and macroporosity. The zeolite catalyst is a nanozeolite. For clarity, reference to a “catalyst composition,” “zeolite composition” or “zeolite catalyst composition” means a catalyst composition containing both a zeolite material and a non-zeolite binder. Reference to “zeolite” or “zeolite catalyst” refers to the zeolite materials used in the catalyst composition.
The zeolite in the catalyst composition can be greater than or equal to 50 wt % of the composition. In some embodiments, the zeolite makes up no more than 80 wt % of the final catalyst composition, and in a particular embodiment, the zeolite makes up about 55-70 wt %, or about 60-65 wt %, of the final catalyst composition.
The particular zeolite for inclusion in the catalyst composition can be selected from those used in liquid fuel production from oxyhydrocarbon feedstocks. The zeolite can be selected with consideration of the particular chemical reactions and the natures of feedstock contemplated. The zeolite provides nano- and microporous crystalline walls with desirable active sites, which provide the desired shape selectivity and reaction time to convert the oxygenated sugar-based feedstock into biofuels and fuel components.
In one or more embodiments, the zeolite can be ZSM-5, beta-, modernite-, and zeolite-Y. The zeolite can be doped with other metals at either the Si or Al site, for example, with one or more of gallium (Ga), lanthanum (La), zinc (Zn), chromium (Cr), iron (Fe) or vanadium (V). In particular, the zeolite can be ZSM-5, an aluminosilicate zeolite belonging to the pentasil family of zeolites. ZSM-5 has a high silicon to aluminum ratio and is acidic with the use of protons to keep the material charge-neutral. In one or more embodiment, the silica alumina ratio in the zeolite catalyst in is the range of 50 to 250 (mol/mol). In specific embodiments, the silica alumina ratio in the zeolite catalyst is the range of 50 to 180 (mol/mol) or 90 to 150 (mol/mol). In one or more embodiments, the alumina ratio (SAR) is in the range of 50 to 250 (mol/mol), or 80 to 200 (mol/mol), or 90 to 180 (mol/mol), or 120 to 150 (mol/mol) or any range bounded by any of the stated values. The ZSM-5 can be doped with other metals at either the Si or Al site, for example, with one or more of gallium (Ga), lanthanum (La), zinc (Zn), chromium (Cr), iron (Fe) or vanadium (V).
The non-zeolite binder material can be selected to impart desirable thermal and mechanical properties, among others, to the zeolite catalyst composition. In one or more embodiments, the non-zeolite binder material is an inorganic oxide, such as silica, titania, zirconia, talc, magnesia, alumina, silica-alumina, calcium oxide, kaolin, clays and combinations of thereof. In one or more embodiments, the non-zeolite binder material is an alumina-containing crystalline material. In particular, the non-zeolite binder material can be a clay, e.g., a kaolin clay. The non-zeolite binder can further include alumina (aluminum oxide). In one or more embodiments, the low bulk density zeolite catalyst is a blend of ZSM-5 zeolite with kaolin clay and alumina oxide as a binder. The relative amounts of zeolite and non-zeolite binder can vary. The amount of zeolite in the catalyst composition can vary from 50 to 80% and the amount of non-zeolite binder can vary from 10% to 40%.
In one or more embodiments, the catalyst composition has a narrow size distribution of mesopore-scale pore volume. For example, the mesopore-scale pore volume can have an average pore diameter of 20 Å to 500 Å. The total pore volume can be in the range of 0.2-0.8 mL(cm3)/g. In other embodiments, the zeolite crystals/particles are uniformly distributed within the non-zeolite binder and have a mesoporosity defined as an average pore size in the range of 20 to 500 Angstroms with an average total pore volume between 0.3 to 0.6 cm3/g. In some embodiments, the catalyst composition used in the conversion of biomass to biofuel can have an average mesopore diameter of 50 Å to 100 Å, and an average total pore volume of at least 0.4 mL/g.
The catalyst composition also includes nanoporosity, which arises from the zeolite structure itself. For example, the zeolite cage molecule forms pore opening on the range of a few angstroms, e.g. 5-10 Å. These pore provide shape selectivity, for example, permitting access to feedstock molecules of certain sizes, while excluding larger molecules. In additions, the acidity, which varies with the SAR, can effect oxygen removal and aromatization.
A catalyst composition containing at least 50% by weight of a nanozeolite catalyst, such as ZSM-5, optionally with a silica alumina ratio between 90 and 250, exhibits lower coking propensity and longer cycle times in converting biomass vapors to gasoline, diesel and jet range hydrocarbons as compared to conventional catalyst composition, e.g., when compared to catalyst that does not meet the suggested criteria of silica alumina ratio and particle size.
It has been surprisingly observed that the use of nanozeolites increases fuel yield per unit biomass input. Also observed, the use of nanozeolites increases catalyst lifetime and thereby also increases fuel yield between regenerations. In addition, the use of nanozeolites reduces the amount of coking that occurs in the biofuel manufacturing process. It has been surprisingly determined that catalysts having zeolite crystallites that are predominantly, e.g., less than or equal to 2 microns, or less than 1 micron, or less than 900 nm, or less than 800 nm, or less than 700 nm or less than 600 nm, or less than 500 nm, or less than 200 nm, less than 150 nm, less than 100 nm and even less than 50 nm and as small as 40 nm, provide high biofuel or biofuel component yields and decrease coking. The zeolite crystallite size gives rise to mesoporosity, e.g., an average pore size in the range of 20 to 500 Angstroms with an average pore volume between 0.3 to 0.6 cm3/g and in some embodiments, an average pore volume of at least 0.4 mL/g.
The improved performance using nanozeolite materials is surprising and runs counter to conventional wisdom that would suggest a larger crystal size and correspondingly large pore volume would provide better fuel yields. Larger pore volume allows the feedstock molecules to spend more time in the catalyst pore volume and provides a greater number of contacts with acid sites at which catalytic conversions occur. For typical fuel feedstocks, such as methanol, in the well-known methanol to gasoline (MTG) process, six methanol molecules are required to undergo numerous reactions in order to form an aromatic compound. Thus, the larger pore volumes and longer residence times are needed and advantageous. Chemical composition, and in particular the relative amounts of silica and alumina in the zeolite catalyst, also plays a role in catalyst performance. Thus, for an MTG process, it is desired that the system provide a relatively long residence time and be highly reactive (high acidity (e.g., SAR 30)) that can drive, first, the dehydration of methanol and then build up the molecular structure to form aromatics.
In contrast, nanocrystalline size of the nanozeolite provide smaller pore size and reduced diffusion path lengths—factors that conventionally suggest a poorer fuel yield. Therefore, it is surprising that in fact higher fuel yield and longer catalyst life is attained. While not bound by any particular mode of operation, it is believed that the nanocrystalline size reduces pore size and pore volume, resulting in shorter diffusion path lengths. The nanozeolite particles or crystallites have large external surface areas and high surface activity. The external surface acidity is advantageous, particularly when the zeolite is used as catalyst in reactions involving bulky molecules, such as those found in biovapors. The higher fuel yields may be attributed to the greater number of active sites. The shorter diffusion path lengths reduces the opportunity for further interaction of the catalyst reaction products with the catalyst, which is attributed with carbonization and coking. Lastly, as the reaction products increase in molecular weight (e.g., size), they are excluded from the zeolite interior pathways and confined to the macroporous pathways, where there are fewer catalytically active sites and where the impact of coking is less severe (given the larger pore size and volume).
In one embodiment, a catalyst for conversion of biovapors containing C5 and C6 sugars includes at least two tunable variables: (1) a nanozeolite having a crystallite size selected to provide a diffusion path length that limits the number of reactive interactions of the feedstock molecules with active sites on the catalyst; and (2) an acidity, that is the relative number of acid sites present in the catalyst, that can be selected to provide a greater or lesser number of acid reactive sites along the diffusion pathway. The two variable can be adjusted together to provide a maximum reactivity for optimal fuel conversion with the fewest number of contacts. By reducing the number of contacts, the chances of undesirable side reactions such as those that lead to coking are reduced.
By way of example, for those catalysts having a longer diffusion pathway, e.g., the nanozeolite crystallite size is on the order of 1-2 microns, then a higher SAR associated with lower acidity can be used, e.g., SAR 120-250. In other examples, for those catalysts having a shorter diffusion pathway, e.g., the nanozeolite crystallite size is on the order of 100-500 nm, then a lower SAR associated with higher acidity can be used, e.g., SAR 50-90. However, such relationships between zeolite crystallite size and SAR is exemplary only, and other combinations are within the scope of the invention.
Catalyst SynthesisThe catalyst composition can be prepared, in particular with reference to the specified micro-, meso- and macroporosity, by combining the zeolite catalyst and non-zeolite binder, with pore formers that create macro-porosity in the final extruded catalyst which are advantageous for performance of the catalyst. It is also contemplated that precursors to the above mentioned materials can be used. For example, colloidal alumina sols, and suspensions of any of above mentioned oxides can be used in the precursor, which are converted into the binder with subsequent processing.
Nanozeolites can be synthesized in an aqueous phase and the composition, temperature, crystallization time, aging time etc. are controlled to allow nanozeolites to form. The principle of the synthesis is derived from the nucleation and crystallization: facilitating the nucleation, which produces nuclei as much as possible; and controlling a subsequent slow growth of crystal particles. See, e.g., Chem. Mater., 2005, 17 (10), pp 2494-2513; Micropor. Mesopor. Matl 156 (2012), pp 97-105; Ceram. Intl, 30 (2013) pp 683-689; Micropor. Mesopor. Matl 156 (2012), pp 29-35; J. Catal. 302 (2013), pp 15-125; Wan et al. Chemica 2013 Conference Proceedings, Brisbain, Australia, Sep. 20-Oct. 2, 2013, Paper No. 30454, for further details in preparation of nanozeolite, the contents of which are incorporated by reference. Alternatively, nanozeolites can be obtained from commercial sources, such as Advanced Chemical Supplier, Medford, Mass. (http://www.acsmaterial.com/product.asp?cid=33&id=141)
According to one or more embodiments, the catalyst composition can be prepared using a sacrificial template method. A templating material is initially homogenously distributed in a continuous matrix of the heat stable phase (e.g., the zeolite and the non-zeolite binder materials) and is thereafter removed to result in a porous material. According to one or more embodiments, a zeolite catalyst composition is prepared by mixing a zeolite catalyst, an alumina-containing material, a sacrificial organic material having particle size and burn out properties selected to provide the desired mesopore and macropore size and pore distribution. The templating agents targets to form pores preferably greater than 500 Å.
Typical sacrificial organic materials include organic materials, such as dense or hollow polymer beads, or particles. Within this broad range of suitable materials, suitable materials include cellulose, starch, polyethylene, PTFE, latex, polyethylene glycol (PEG), acicular carbons, carbon black, activated carbon, graphite, carboxylic acids such as oxalic acid, and lingo-sulfonic acid and combinations thereof. The size, shape and arrangement of the sacrificial organic material offers significant versatility to independently tailor the porosity, pore size distribution and pore morphology. The organic compound is preferably selected based upon the nanozeolite material being used, so as to provide pore volume of appropriate size and shape. It should be appreciated that the amount of meso and macro pore-sized pore volume provided depends at least in part upon the amount of sacrificial organic material included in the precursor. In addition to the nanozeolite crystallite properties, the size of the meso and macro pore-sized pores depends at least in part on the particle or bead size of the sacrificial organic material. Thus, the amount and size of meso and macro pore-sized pore volume can be selectively controlled by selecting the proper amount and size of sacrificial organic material. Exemplary particle size can range from about 1 μm to 250 μm, or preferably between about 5 μm and 180 μm. In other embodiments, the particle size can be much smaller, particularly when using carbon as the sacrificial material.
The zeolite catalyst, alumina-containing material and sacrificial organic material are combined to obtain a paste of a consistency suitable for further post-processing, such as molding or extruding. Also, the binder materials may be provided in part in colloidal form so as to facilitate extrusion of the bound components. The mixture may also be combined with other materials, used as diluents or glidants to assist in the powder processing. It may be advantageous to precombine the powder ingredients. The combined powder ingredients can be sieved to reduce agglomeration and provide a uniform particle size.
The resulting paste can be formed into a desired shape and then heated to form the crystalline composition and burn out the sacrificial organic material, thereby introduce macroporosity and/or mesoporosity into the composition. Calcine temperatures are preferably kept below a temperature known to degrade or modify the catalytic properties of the zeolite. In exemplary embodiments, the precursor is heated to temperatures in the range of 300-700° C., and preferably in the range of 500-600° C. The solidified crystalline microporous zeolite composition contains a meso and macro pore-sized pore volume having the desired narrow pore-sized distribution.
Biomass to Biofuel ConversionThe catalyst composition prepared in accordance with the invention is particularly useful as a catalyst for the generation of renewable liquid fuels, e.g., “biofuels,” from biomass. In one or more embodiments, it can be used for the production of desired aromatics such as benzene, toluene, and xylene (BTX) and other substituted aromatic fuels from pyrolysis gases. Conversion of biovapors to fuel or fuel components of diesel or jet fuel is also contemplated. It has been surprisingly determined that pyrolysis vapors derived at relatively low pyrolysis temperatures, e.g., less than 400° c., or less than 350° C., when separated from the pyrolysis reactor and directed, without condensation, over a heated catalyst bed including a nanozeolite produces high fuel yields (e.g., greater than 6.5%, or greater than 7.0% or greater than 7.5%, or greater than 8.0% or greater than 8.5% by weight of input biomass, or in the range of 6.5-12% by weight of input biomass) with very low coking (e.g., less than 5 wt %, or less than 4 wt %, or less than 3 wt % or even less than 2 wt % by weight of input biomass).
Biovapors containing oxygenated feedstocks rich in C5 and C6 sugars can be generated from biomass using a number of conventional processes, such as chemical, thermal and biological decomposition processes. Exemplary chemical processes include acid hydrolysis of cellulosic materials. There are normally two ways to hydrolyze cellulose: chemically and enzymatically. The chemical method uses acids to hydrolyze cellulose under high temperature and pressure. The enzymatic method uses bacteria secreted proteins to hydrolyze cellulose, namely cellulase. Thermal processes can include pyrolysis.
The process of heating a combustible material in either a reduced oxygen environment or oxygen-free environment is called pyrolysis. Pyrolyzing wood and other forms of mixed biomass produces a high carbon content coke (also called biochar) and a complex mixture of decomposition products. Depending on the conditions of the pyrolysis, the composition of the products can be varied. In general, when subject to high temperatures (e.g., 800° C.) for prolonged periods of time, pyrolysis ultimately yields syngas. At lower temperatures and time intervals, increasingly complex hydrocarbons and oxygenated hydrocarbons are present in the gas stream from the pyrolyzed biomass. The composition of pyrolysis gases can be complex and typically includes a range of oxygenated organic molecules, many having a size and/or molecular weight that is larger than conventional feedstocks such as methanol, ethanol and dimethyl ether (DME).
The biomass used herein can be any biomass capable of being converted to liquid and gaseous hydrocarbons when subjected to pyrolysis. As used herein, the term ‘biomass’ includes any material derived or readily obtained from plant or animal sources. Such material can include without limitation: (i) plant products such as bark, leaves, tree branches, tree stumps, hardwood chips, softwood chips, grape pumice, sugarcane bagasse, switchgrass; and (ii) pellet material such as grass, wood and hay pellets, crop products such as corn, wheat and kenaf. This term may also include seeds such as vegetable seeds, sunflower seeds, fruit seeds, and legume seeds. The term ‘biomass’ can also include: (i) waste products including animal manure such as poultry derived waste; (ii) commercial or recycled material including plastic, paper, paper pulp, cardboard, sawdust, timber residue, wood shavings and cloth; (iii) municipal waste including sewage waste; (iv) agricultural waste such as coconut shells, pecan shells, almond shells, coffee grounds; and (v) agricultural feed products such as rice straw, wheat straw, rice hulls, corn stover, corn straw, and corn cobs.
Conventional methods for pyrolyzing carbon-containing material may be used in the multistage method and system described herein. A number of well-known pyrolysis reactors, including fixed bed reactors, fluidized bed reactors, circulating bed reactors, bubbling fluid bed reactors, vacuum moving bed reactors, entrained flow reactors, cyclonic or vortex reactors, rotating cone reactors, auger reactors, ablative reactors, microwave or plasma assisted pyrolysis reactors, and vacuum moving bed reactors can be employed for the pyrolysis process. A biomass fractionator, such as that described in U.S. Pat. No. 8,216,430, assigned to Cool Planet Energy Systems, Inc., which details the placement of biomass in thin sheets in compartments and subjects the biomass to controllable pyrolysis conditions, also may be used. Auger pyrolyzers and pyrolysis methods can also be used, such as those described in United States Publication 2014/0183022, published Jul. 3, 2014, which is incorporated herein by reference. In some embodiments, pyrolysis is conducted at temperatures in the range of 250° C.-500° C. or preferably in the range of 350° C.-425° C. to produce a mixture of oxygenated hydrocarbon vapors, collectively referred to as pyrolysis vapors. Biomass is typically comprised of a wide array of compounds classified within the categories of cellulose, hemicelluloses, lignin, starches, and lipids. These compounds go through multiple steps of decomposition when subject to the pyrolysis process. For example, hemicelluloses comprise C5 sugars such as fructose and xylose, which yield furfural and hydroxymethylfurfurals upon thermolysis. The latter compounds can be further converted to fuel intermediates furan and tetrahydrofuran.
The pyrolysis vapors generated from the thermal degradation of biomass are directed to one or more catalytic reactor(s) for conversion to biofuel. In one or more embodiments, biomass pyrolysis vapors are converted to gasoline, diesel and/or jet fuel or fuel components by passing the pyrolysis vapors over a catalyst composition as described herein that has been heated to a temperature in the range of 350° C.-500° C. at a weight hourly space velocity (weight of vapor feed per unit weight catalyst/hour) of 0.1-10 hr−1. In some embodiments, water or steam optionally is injected during pyrolysis and the combination of biovapors and steam or water is passed over the zeolite catalyst composition bed. In some embodiments, the water source can be process water collected as a byproduct of the conversion of biovapors into gasoline, diesel and jet range hydrocarbons. The ratio of steam to biomass can be in the range of 0.05 to 0.9 (wt/wt). Addition of water or steam to the catalyst process has been observed to increase fuel yield and/or reduce coking. In one or more embodiments, the fuel yield increases by up to 5% or by up to 10% or by up to 15% or by up to 20% as compared to a comparable process run in the absence of steam. In one or more embodiments, coke formation decreases by up to 5% or by up to 10% or by up to 15% or by up to 20% as compared to a comparable process run in the absence of steam. Without being bound by any theory of operation, the steam may serve to clean the catalyst and remove coke as it forms, thereby maintaining the active surface area of the catalyst for longer periods of time and increasing total fuel yields for the lifetime of the catalyst.
The zeolite catalyst composition subjects the pyrolysis gases to a number of chemical conversions. Due to the acid sites on the zeolite catalyst, the catalyst subjects the pyrolysis gases to one or more of dehydrogenation, decarboxylation, decarbonylation, cyclization and aromatization reaction. As noted above, the nanocrystalline zeolite provides short diffusion pathways for the pyrolysis gases through the catalyst to improve catalyst efficiency and reduce coking.
The single zeolite reactor can be replaced with multiple reactors in series when needed. The catalyst in such multiple reactors can be the same catalyst or different catalysts. When multiple reactors are used, they can be operated at the same temperature or at different temperatures. When multiple catalytic reactors are used, the effluent from the first reactor can be passed to the second reactor without intermediate processing. In some embodiments, the first and second catalysts can be contained within the same reactor, positioned so that the flowing vapors interact sequentially with the first and second catalyst compositions. In other embodiments, the effluent from each reactor is condensed, with liquid product being separated and the non-condensable gaseous product being introduced in to the subsequent catalytic reactor for further fuel production.
The catalyst composition is housed in a catalytic reactor and can be a fixed bed reactor or a vertical reactor. The catalytic reactor can include a single catalyst composition or multiple catalyst compositions to which a reactant gas is exposed to sequentially, e.g., in a single or in multiple catalytic reactors. The multiple catalyst beds can be the same or different; the catalytic processing conditions, e.g., temperature, pressure, dwell time, can be the same or different.
In one or more embodiments, the catalytic process includes at least two catalyst beds. In one embodiment, a first catalyst bed includes a ‘guard’ catalyst and a second catalyst bed includes the nanozeolite catalyst. A process for converting biomass vapors to gasoline, diesel and jet range hydrocarbons includes advantageously first passing the biovapors generated from pyrolysis of biomass through a guard catalyst under one set of temperature and pressure conditions before they are converted using such a nanozeolite catalyst at either the same or different temperature and pressure conditions, according to one or more embodiments. The guard catalyst can be selected to be a dehydration catalyst, decarboxylation catalyst, decarbonylation catalyst, deoxygenation catalyst or other catalyst that can reduce the oxygen content and increase the hydrogen content of the biovapor. Biomass decomposition, such as by pyrolysis at temperatures below 400° C., typically produces oxygenated feedstocks (primarily sugars and sugar-alcohols). The guard catalyst can reduce the hydrogen and oxygen content of the feedstock, for example by removal of water, formaldehyde and carbon dioxide, to provide furans and other olefinic compounds. Use of a guard catalyst to increase the quality of the biovapor stream entering the nanozeolite catalyst train can improve fuel yield and reduce coking on the nanozeolite catalyst.
The guard catalyst can be an acidic catalyst or a basic catalyst or a combination of acidic and basic catalyst at various ratios. Suitable guard catalysts which are acidic useful for the present invention are heterogeneous (or solid) acid catalysts. At least one solid acid catalyst may be supported on at least one catalyst support (herein referred to as a supported acid catalyst). Solid acid catalysts include, but are not limited to, (1) heterogeneous heteropolyacids (HPAs) and their salts, (2) natural clay minerals, such as those containing alumina or silica (including zeolites), (3) cation exchange resins, (4) metal oxides, (5) mixed metal oxides, (6) inorganic acids or metal salts derived from these acids such as metal sulfides, metal sulfates, metal sulfonates, metal nitrates, metal phosphates, metal phosphonates, metal molybdates, metal tungstates, metal borates, and (7) combinations of groups 1 to 6. Guard catalysts that are suitable for the present invention that are basic catalysts are heterogeneous (or solid) basic catalysts. At least one of the solid basic catalyst or basic components may be supported on at least one catalyst support (herein referred to as supported basic catalysts). Such basic catalysts include, but not limited to (1) alkali and alkaline metal or metal oxides or metal hydroxides supported catalysts, where in the alkali metals are Lithium, Sodium, potassium, magnesium, strontium, cesium and Rubidium (2) basic transition metal supported catalysts such as zinc oxide, copper oxides etc., (3) hydrotalcites or layered double hydroxide catalysts such as Mg6Al2(OH)16CO3.4H2O (4) solid super basic catalysts such as KF on europium oxide, KF on hydrotalcites etc. In one or more embodiments, the guard catalyst can be a nanozeolite catalyst as described herein. In particular embodiments, the guard catalyst is nano-ZSM-5. The guard bed can be operated at temperatures independent of the zeolite catalytic reactor.
In one or more embodiments, the both the first and second catalyst beds includes a zeolite catalyst composition as described herein; however, the specific zeolite catalyst composition used in each catalyst bed can be the same or different. The catalyst beds can be run under different conditions, e.g., at different temperatures. For example, the first catalyst bed can be operated at a temperature in the range of 250-400° C. and the second catalyst bed can be operated at a temperature in the range of 300-500° C. In one or more embodiments, the temperature of the second catalyst bed in greater than that of the first catalyst bed. The lower temperature is not as efficient at converting the pyrolysis gases into fuel grade molecules, however, it can begin the conversion of the oxygenates to simpler molecules, such as furans and olefins. The second bed is run at a higher temperature that is capable of forming the fuel molecules. Because the reactant mix has been simplified by reaction the first bed, conversion to fuel grade molecules is more efficient and the dwell time can be reduced. This reduces the changes of coking at the higher temperatures of the second bed.
In operation, a raw biovapor obtained, for example, as a heated gas directly from a pyrolysis reactor is fed, optionally without condensation, into a catalyst reactor having a guard catalyst and a nanozeolite catalyst such as a nanoscale BTX catalyst. The catalysis reactor is arranged for sequential contact with first guard and then the BTX catalyst. The run can be continuous as long as the fuel output remain within acceptable parameters. The quality of the fuel output is monitored in terms of fuel yield, fuel oxygen content and/or coke levels. Thus, fuel levels should remain above a threshold level, while fuel oxygen content and coke should remain below threshold levels during operation. After the catalyst is spent, it can be regenerated.
The invention is illustrated in the following examples, which are not intended to be limiting of the invention and are presented solely for illustrative purposes.
Example 1 Evaluation of Commercially Available ZeolitesThe catalysts of the present invention obtained from various catalyst vendors were characterized by silica alumina ratio, the zeolite particle size and the porosity (pore diameter and pore volume). In general, pore size, pore volume and BET surface area decrease as the silica alumina ratio (SAR) increases.
Significant differences were observed in the physical properties and particle sizes of various ZSM-5 zeolite samples. The BET surface area was lowered from 400 m2/g to 340 m2/g as the silica-alumina ratio increased. There was also a corresponding trend in decreasing average pore diameter and average pore volume data as the silica-alumina ratio increased. The SEM pictures also revealed differences in crystal morphologies among samples. While some ZSM-5 samples are planar and cylindrical, the others are more spherical or agglomerated spherical particles. When noticed closely, the SEM picture for the sample with silica-alumina ratio of 120, it appears that the ZSM-5 particles are more uniform when compared to the other catalyst samples under investigation. Also, the size of these crystallites appear to be less than 2 microns versus all other samples, where the size was above 3 microns, and even particles in the range of 6 to 10 microns were also noticed as agglomerates. Thus, the only sample in Table 1 having a predominant number of crystallites with a crystallite size of less than 2 μm is the SAR 120 ZSM-5 catalyst.
Example 2 Experiments on Catalyst Activity MeasurementsThe catalyst activity measurements for the catalysts in Table 1 were performed in a vertical reactor system. The vertical reactor system had a batch pyrolyzer that is coupled to either a single catalytic reactor or multiple catalytic reactors that are in series. A schematic illustration of the experimental set up is shown in
The raw fuel and process water were collected and separated. The light gases from the gas liquid separator were recirculated back into the pyrolyzer and/or the guard bed reactor and/or the first zeolite catalytic reactor, with the use of a compressor. The unit operated between 7-8 psi and pressure was controlled by a solenoid valve/back pressure regulator arrangement placed after the condenser. As the reaction progressed, the light gases that accumulated in the reactor beyond 8 psi were vented into the exhaust. The flow rate of the purge gases was also measured and analyzed for complete mass balance.
A batch pyrolyzer with a guard bed and single zeolite reactor configuration was used to evaluate the zeolite catalysts with light gas recirculation as mentioned above. Biomass used in this work was pine pellets (commercially obtained horse bedding pine pellets) with a moisture content of approximately 6%. For each experiment, the pyrolysis chamber was loaded with 200 g of pine pellets. The pyrolysis vapors, recirculation gases, and carrier gas were pre-mixed and pre-heated before they entered the catalytic reactor. N2 (at 0.1 SCFH) is used as carrier gas at all times to help drive the pyrolysis vapors into first, the guard bed, followed by the zeolite catalytic reactor. N2 is preheated to 300° C. before it entered the pyrolysis chamber. Pyrolysis of biomass occurred from 150° C. to 370° C. in 4 hours. The pyrolysis vapors were fed directly (without condensation) into the catalytic reactor. The unit was run for an additional hour at 370° C. to drive off any residuals in the pyrolysis chamber and the catalytic reactor. The reactor was cooled and char was collected next day by opening the pyrolysis chamber. The collected char was weighed to get the % char yield from the experiment and stored for further analysis. The experiment was repeated, by loading fresh biomass (200 grams) and continuing the run as described above. Several runs were performed in this manner as long as the fuel production was meaningful, as measured by oxygen content of the produced fuel. The set of runs were stopped when the fuel production declined as a result of catalyst coking. The length of the run and the fuel yields were used to differentiate the performance of various zeolite catalysts. The amount of oxygen in the fuel (due to the presence of un-converted heavy oxygenates) was also measured and used as an end of run/cycle criteria for a particular catalyst being investigated. Experiments were compared with the same guard catalyst (and its amount) and with the same amount of zeolite catalyst, thus any difference in performance is a direct effect of the nature and type of the zeolite catalyst used, while all other process parameters are maintained the same.
The guard reactor was loaded with 100 grams of high surface area alumina catalyst. The guard catalyst is approximately ⅛th in diameter extrudates obtained from Alfa Aesar. The guard bed was operated at 325-370° C. Input to the guard bed was pyrolysis vapors, N2 carrier gas, and recirculated light gases, all of which are preheated at least to 300° C. and not above 370° C.
The amount of zeolite catalyst used was also 100 grams. The zeolite catalyst(s) used were also ⅛th inch extrudates. After a set of experiments are complete (e.g., after about 3 to 8 days of tests, depending on the catalyst activity and longevity), both the alumina guard catalyst and the zeolite catalyst were removed and subject to manual regeneration from which the coke information was deduced. Thus, the amount of coke burnt is cumulative for those set of experiments. The output from the condenser is fuel and process water which is separated, measured and subjected for further analysis. Particular attention was paid to amount of benzene and durene in the fuel. The amount of polyaromatic compounds and oxygenates were also measured using GC and GC-MS. Table 2A shows experimental data obtained by screening 200 gram batches of biomass using these various ZSM-5 zeolite catalysts.
Since the pyrolysis occurred up to a temperature of 370° C., which was maintained the same for all catalysts tested, the amount of char collected was more or less uniform and in the 36% to 39% range. However, significant differences in fuel yield and fuel oxygen content were observed depending on the type of ZSM-5 catalyst being tested. As discussed in greater detail below, biomass processed using ZSM-5 catalyst sample #3 far out-performed the other catalysts.
Referring to Table 2A, catalyst samples 1, 2, 4 and 5, having zeolite crystallites greater than 3 μm, had average fuel yields of 6.3% or less, as compared to an average fuel yield of 6.8% for catalyst sample #3, having zeolite crystallites predominantly less than 2 μm. The light gas yield was also higher. More significant, increasing trend in fuel oxygen, and lower fuel yields were noticed for catalyst samples 1, 2, 4 and 5 after 4 days of evaluation, indicating the unsuitability of these catalysts and greatly reducing the total, cumulative fuel yielded during the run-life of the catalyst. While all other catalysts indicated a downward trend of fuel production by day 4 and day 5, indicating catalyst degradation, catalyst sample #3 continued consistent fuel production till day 8, thus proving its longevity when compared to other zeolite ZSM-5 catalysts tested. Comparative performance of the various ZSM-5 catalyst compositions is shown in Table 2B.
Note the significantly longer catalyst life and higher total fuel production. Interestingly, although the total coke formation for sample #3 is higher than for the other catalysts tested (not surprising given its longer run time), the fuel to coke ratio is commensurate with the other catalysts.
Example 3 Effect of Water Addition on Catalytic ActivityDe-ionized water was injected into the pyrolyzer. The ratio of de-ionized water to Biomass was 0.2:1. De-ionized water was injected over a period of 4 hours during which the pyrolysis temperature was ramped from 150° C. to 370° C. Water injection was stopped after this 4 hour period, while the pyrolyzer continued to stay for an additional hour at 370° C. to drive off any residual gases. The de-ionized water was preheated to a temperature of 300° C. before it was injected into the pyrolyzer. The amount of fuel produced with and without de-ionized water injection was very similar and about 7%. However, the fuel oxygen analysis indicated that the amount of oxygen in the fuel is lowered by the presence of steam. Also the total coke reduced by 4.19 grams from 32.46 grams to 28.27 grams upon addition of steam. On an individual basis, steam addition affected the coke reduction on ZSM-5 catalyst more than the coke reduction on guard catalyst. 20% coke reduction was noticed on ZSM-5 catalyst upon addition of steam at a steam to biomass ratio of 0.2:1.
The effect of water addition is demonstrated in Table 3. A reduction of zeolite catalyst coking is observed (10.15 g with water vs. 12.84 g without water), without significant reduction in fuel yields (6.8% with water vs. 6.9% without water).
In order to verify the hydrothermal stability of this zeolite catalyst with silica-alumina ratio of 120, 100 grams of this catalyst was subject to temperature cycles between 300° C. and 600° C. for 500 hours using a mixture of 30% steam and balance N2. The testing cycle was such that the catalyst was placed in a reactor where in it takes ½ hour to reach 600° C., stays at 600° C. for 1 hour and drops to 300° C. in ½ hour and this cycle from 300° C. to 600° C. is continued for 500 hours. In other words, the catalyst was periodically at 600° C. for about 250 cycles. After 500 hours, the amount of water consumed was measured and the catalyst was removed. The catalyst was subject to BET measurements. Data presented in Table 4 and
Nano zeolite extrudates were prepared by combining nano zeolite powder and alumina binder. Alumina binder was commercially obtained high surface area alumina powder. Nano zeolite powder with a silica to alumina ratio (SAR) of 50, was prepared as follows. First a nano-zeolite seed solution was prepared. This seed solution was prepared by mixing Tetraethylorthosilicate (TEOS) solution and 25% Tetrapropylammonium hydroxide (TPAOH) in a 42/58 weight ratio. This solution is mixed at room temperature for 2 hours in a sealed autoclave, until homogenous. The mixing is then stopped, and the solution is allowed to stand overnight at room temperature in the sealed autoclave. This hydrolyzed solution in the autoclave was then placed in a convection oven at 80° C. and aged for 72 hours to develop the nano-crystalline seeds. This nano-crystalline seed solution was used “as is” for the production of nano-zeolite powder during its synthesis. Characterization of this nano-seed solution is done by drying a small amount, calcining the dried solids at 550° C. in air for 8 hours, and testing the solids by BET surface area method using N2 adsorption technique. Typical surface area of the dried and calcined nano-seed powder is 500 to 800 m2/g.
The synthesis of ZSM-5 nano zeolite with SAR 50 began by making two precursor solutions, which are mixed to generate a precursor gel. In order to generate a SAR of 50 of the final nano-zeolite powder, a higher SAR ratio of the precursor gel is required. Thus a SAR of 75 was used of the precursor gel to obtain a formed nano zeolite powder with a nominal target of SAR 50.
To obtain the first precursor solution, sodium silicate solution, DI water, the nano-seed solution (preparation method described above), and 40% TPAOH were mixed together. A typical formulation would use 450.5 grams of sodium silicate at SiO2/Na2O ratio of 2.5, 530 grams DI water, 14.2 g zeolite seed solution, and 15.4 g of 40% TPAOH (tetra-propyl ammonium hydroxide) solution in water.
To obtain the second precursor solution, DI Water, Sulfuric Acid, and Aluminum Sulfate decaoctahydrate were mixed together. A typical formulation would use, 530 g of DI water, 45 g of sulfuric acid, and 18.5 g of Aluminum sulfate decaoctahydrate. This solution was mixed until clear.
The second precursor solution was added to the first precursor solution while vigorously mixing, resulting in a gel. This precursor gel was placed in a sealed autoclave and heated to 175° C. for 20 hours, under autogenous pressure.
After this 20 hours synthesis step was completed, the autoclave was cooled and opened to collect its contents, which is a slurry of crystalline nano zeolite material. This slurry was filtered to remove the zeolite material from its mother liquor. The mother liquor can be advantageously recycled back to the precursor solutions and used instead of DI water for subsequent batches of nano-zeolite production. The collected nano zeolite filter cake was then dried and broken into lumps before subjecting it to an ion-exchange process. Ion exchange was performed by bathing the nano-zeolite lumps in a one molar solution of ammonium nitrate. This bathing was repeated for at least 4 times (or 4 exchanges) over a total of 8 hours. The exchanged ammonium nano zeolite is then filtered, dried and calcined at 550° C. for 8 hours to remove the ammonia cations, resulting in crystalline nano zeolite HZSM-5 material.
The resultant ZSM-5 nano-zeolite powder is characterized by BET procedure using N2 adsorption for Surface area. Typical surface area for nano zeolite powder with SAR=50 is between 425 to 460 m2/g. The ZSM-5 nano-zeolite powder is also characterized by XRF to confirm the SAR ratio. SEM analysis was also performed to measure the crystallite sizes of the nano zeolite thus produced. X-ray diffraction analysis was performed to measure the % crystallinity of the nano zeolite powder.
For production of the final catalyst in extrudates, the nano-zeolite powder lumps were ball milled for 1 hour in low speed tumbling using alumina as media in the ball mill. This ball milled nano-zeolite powder was mixed at 80/20 weight ratio with an alumina binder, in this case Dispal 23N4-80 from Sasol Inc. DI water was added to this mixture sufficient to form a stiff but workable dough. The dough was extruded mechanically into strands through a ⅛ inch orifice, forming strands of “green” catalyst. These strands are dried and broken up by hand to “green” extrudates of average ⅛ inch diameter by ¼ to ½ inch in length. The “green” catalyst extrudates were then fired in alumina crucibles in a furnace at 550° C. for 8 hours under air atmosphere to result in final extruded catalyst containing a nano-zeolite with SAR 50.
Finished extrudates were then characterized by BET procedure using N2 adsorption for Surface area. Typical surface area for final extrudates with SAR 50 is between 380 and 420 m2/g. The final catalyst extrudates were also characterized by XRF to determine the sodium content and any other impurities and their levels. The crush strength of the extrudates and the bulk density of the extrudates was also measured.
Similar methods were used to prepare a ZSM-5 nano-zeolite powder having SAR 120.
Catalytic activity for conversion of biovapors to biofuel was investigate for the catalyst prepared in Example 5. Catalyst performance is shown in Table 6. The table also includes the average fuel and coke yields after a multiday run.
The catalyst activity measurements for the catalysts in Table 6 were performed substantially as described in Example 2, except that 150 g of alumina guard catalyst and 150 g of zeolite catalyst were used for samples 6 and 7; 450 g of biomass were processed daily. 200 g of alumina guard catalyst and 200 g of zeolite catalyst were used for sample 8; 600 g of biomass were processed daily. The data from each run is reported in Tables 7-9 below.
Unless otherwise defined, used or characterized herein, terms that are used herein (including technical and scientific terms) are to be interpreted as having a meaning that is consistent with their accepted meaning in the context of the relevant art and are not to be interpreted in an idealized or overly formal sense unless expressly so defined herein. For example, if a particular composition is referenced, the composition may be substantially, though not perfectly pure, as practical and imperfect realities may apply; e.g., the potential presence of at least trace impurities (e.g., at less than 1 or 2%) can be understood as being within the scope of the description; likewise, if a particular shape is referenced, the shape is intended to include imperfect variations from ideal shapes, e.g., due to manufacturing tolerances. Percentages or concentrations expressed herein can represent either by weight or by volume.
Although the terms, first, second, third, etc., may be used herein to describe various elements, these elements are not to be limited by these terms. These terms are simply used to distinguish one element from another. Thus, a first element, discussed below, could be termed a second element without departing from the teachings of the exemplary embodiments. Spatially relative terms, such as “above,” “below,” “left,” “right,” “in front,” “behind,” and the like, may be used herein for ease of description to describe the relationship of one element to another element, as illustrated in the figures. It will be understood that the spatially relative terms, as well as the illustrated configurations, are intended to encompass different orientations of the apparatus in use or operation in addition to the orientations described herein and depicted in the figures. For example, if the apparatus in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term, “above,” may encompass both an orientation of above and below. The apparatus may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. Further still, in this disclosure, when an element is referred to as being “on,” “connected to,” “coupled to,” “in contact with,” etc., another element, it may be directly on, connected to, coupled to, or in contact with the other element or intervening elements may be present unless otherwise specified.
The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of exemplary embodiments. As used herein, singular forms, such as “a” and “an,” are intended to include the plural forms as well, unless the context indicates otherwise.
It will be appreciated that while a particular sequence of steps has been shown and described for purposes of explanation, the sequence may be varied in certain respects, or the steps may be combined, while still obtaining the desired configuration. Additionally, modifications to the disclosed embodiment and the invention as claimed are possible and within the scope of this disclosed invention.
Claims
1. A method of converting biovapors to biofuel, comprising:
- directing biovapors derived from decomposition of biomass, said biovapors comprising at least C5 and C6 compounds, into a catalytic reaction chamber separate from the decomposed biomass; and
- contacting the biovapors with a catalyst composition comprising a nanozeolite.
2. The method of claim 1, wherein the C5 and C6 compounds are cyclic.
3. The method of claim 1, wherein at least 60% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 2 μm.
4. The method of claim 1, wherein at least 80% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 2 μm.
5. The method of claim 1, wherein at least 90% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 2 μm.
6. The method of claim 1, wherein at least 25% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 1 μm.
7. The method of claim 1, wherein at least 40% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 1 μm.
8. The method of claim 1, wherein at least 50% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 1 μm.
9. The method of claim 1, wherein nanozeolite crystallite has a silica to alumina ratio in the range of 50-250.
10. The method of claim 1, wherein the nanozeolite catalyst comprises ZSM-5.
11. The method of claim 1, wherein the nanozeolite is selected from a group consisting of ZSM-5, beta-zeolite, modernite-zeolite, zeolite-Y and mixtures thereof.
12. The method of claim 1, wherein the catalyst composition further comprises a non-zeolite binder.
13. The method of claim 1, wherein the biovapors are contacted with a catalyst composition heated at a temperature in the range of 350° C.-500° C.
14. The method of claim 1, wherein the biovapors are contacted with a catalyst composition at a weight hourly space velocity of 0.1-1.0 hr−1.
15. The method of claim 1, wherein contacting the biovapors with a catalyst composition comprises sequentially contacting the biovapors with two or more catalysts compositions.
16. The method of claim 15, wherein the catalyst compositions are different.
17. The method of claim 15, wherein the catalyst compositions are the same.
18. The method of claim 15, wherein the catalyst compositions are subjected to different reaction conditions.
19. The method of claim 18, wherein the temperature of the catalyst conditions are different.
20. The method of claim 19, wherein the temperature of the first catalyst composition is lower than the temperature of the second catalyst composition.
21. The method of claim 15, wherein the second catalyst is a guard catalyst and the biovapors are contacted with the guard catalyst prior to contacting the biovapors with the nanozeolite catalyst composition.
22. The method of claim 21, wherein the guard catalyst is selected from the group consisting of a dehydration catalyst, decarboxylation catalyst, decarbonylation catalyst, and deoxygenation catalyst.
23. The method of claim 21, wherein the guard catalyst is selected from the group consisting of (1) heterogeneous heteropolyacids (HPAs) and their salts, (2) natural clay minerals, such as those containing alumina or silica (including zeolites), (3) cation exchange resins, (4) metal oxides, (5) mixed metal oxides, (6) inorganic acids or metal salts derived from these acids such as metal sulfides, metal sulfates, metal sulfonates, metal nitrates, metal phosphates, metal phosphonates, metal molybdates, metal tungstates, metal borates, and (7) combinations of groups 1 to 6.
24. The method of claim 21, wherein the guard catalyst comprises a nanozeolite.
25. The method of claim 21, wherein the guard catalyst is selected from the group consisting of (1) alkali and alkaline metal or metal oxides or metal hydroxides supported catalysts, where in the alkali metals are Lithium, Sodium, potassium, magnesium, strontium, cesium and Rubidium (2) basic transition metal supported catalysts such as zinc oxide, copper oxides etc., (3) hydrotalcites or layered double hydroxide catalysts such as Mg6Al2(OH)16CO3.4H2O and (4) solid super basic catalysts such as KF on europium oxide, KF on hydrotalcites.
26. The method of claim 1, wherein the biovapors are obtained from a decomposition process selected from chemical, thermal and biological decomposition processes.
27. The method of claim 26, wherein the thermal process comprises pyrolysis.
28. The method of claim 26, wherein the chemical process comprises acid hydrolysis.
29. The method of claim 26, wherein pyrolysis comprises heating biomass at temperatures of less than 600° C. to generate pyrolysis vapors.
30. The method of claim 27, wherein water or steam is injected into biomass during pyrolysis.
31. The method of claim 30, wherein the ratio of steam to biomass is in the range of 0.5 to 0.9 (wt/wt).
32. The method of claim 1, wherein the fuel yield is greater than 6.5%, or greater than 7.0% or greater than 7.5%, or greater than 8.0% or greater than 8.5% by weight of input biomass, or in the range of 6.5-12% by weight of input biomass.
33. The method of claim 1, wherein the reaction is carried out without addition of a cosolvent, such as methanol, ethanol or dimethyl ether.
34. The method of claim 1, wherein the fuel product contains less than 3 wt % benzene and less than 1 wt % durene.
35. A catalyst system for conversion of biovapors into biofuel, comprising:
- a catalyst reactor comprising at least two catalyst compositions positioned and arranged for sequential contact with a vapor,
- wherein the first catalyst comprises a guard catalyst selected to reduce oxygen content and increase the hydrogen content of an oxygenated C5 and C6 compound-containing biovapor, and
- wherein the second catalyst comprises a nanozeolite catalyst wherein at least 90% of the zeolite crystallites have a largest dimension of less than or equal to 200 μm.
36. The catalyst system of claim 35, wherein at least 25% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 1 μm.
37. The catalyst system of claim 35, wherein at least 40% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 1 μm.
38. The catalyst system of claim 35, wherein at least 50% of the crystallites of the nanozeolite catalyst have a largest dimension that is less or equal to 1 μm.
39. The catalyst system of claim 35, wherein nanozeolite crystallite has a silica to alumina ratio in the range of 50-250.
40. The catalyst system of claim 35, wherein the nanozeolite catalyst comprises ZSM-5.
41. The catalyst system of claim 35, wherein the nanozeolite is selected from a group consisting of ZSM-5, beta-zeolite, modernite-zeolite, zeolite-Y and mixtures thereof.
42. The catalyst system of claim 35, wherein the catalyst composition further comprises a non-zeolite binder.
43. The catalyst system of claim 35, wherein the first and second catalyst compositions are different.
44. The catalyst system of claim 35, wherein the first and second catalyst compositions are the same.
Type: Application
Filed: Jul 11, 2016
Publication Date: Jan 12, 2017
Inventors: Rajashekharam MALYALA (Camarillo, CA), Mark L. JARAND (Newbury Park, CA), Timothy Alan THOMPSON (Ventura, CA), Haijun WAN (Camarillo, CA), Arindom SAHA (Camarillo, CA), Iliiana CHILACHKA (Camarillo, CA)
Application Number: 15/206,655
