Process for treating grains to produce materials useful in chemicals and biofuels

Abstract

A method for treating grain having starch and non-starch carbohydrates, wherein the starch is present in an amount of at least 10% by weight based on the dry weight of the grain. Contacting the grains with a solution containing at least one alpha-hydroxysulfonic acid; and reacting under acid hydrolysis conditions to produce a product suitable for the production of chemicals and / or fuels.

Description

Technical Field

[0001] The present invention relates to a method for processing renewable raw materials for producing materials that can be used in the production of chemicals and fuels, and in particular to a method for processing cereal grains for the production of chemicals and fuels. Background Art

[0002] Many efforts to partially or completely replace fossil-derived resources for the sustainable production of chemicals and / or fuels focus on the use of corn, sugarcane, biomass and other agricultural residues. For example, in the corn dry milling process, the whole grain is ground (milled) into a powder. The powder is then physically and chemically prepared for fermentation to produce a paste by cooking, and the paste is hydrolyzed using enzymatic saccharification to release sugars. The sugar mixture is then fermented together with the solids to produce ethanol. The fermentation product is distilled to separate the ethanol from the unconverted solids and the process water or stillage retained at the bottom of the still. In a typical process, the whole stillage is separated into a thin stillage (liquid fraction) and a solid fraction known as wet stillage grain (WDG).

[0003] The solids contain mainly the unfermented remains of the grain (protein, fiber, fat). Grain fiber contains sugars in the form of unconverted polysaccharides such as cellulose, hemicellulose and resistant starch.

[0004] The main obstacle to using fiber in WDG is the expensive pretreatment step to release these sugars and make the cellulose and other polysaccharides in the feedstock susceptible to enzymatic hydrolysis. One of the leading candidates for such pretreatment is dilute mineral acid hydrolysis (usually sulfuric acid or hydrochloric acid). The conditions for successful pretreatment in dilute acid hydrolysis are determined by a combination of three factors: time, temperature, and acid concentration. Elevated temperature leads to the loss of sugars as degradation products, and increasing acid concentration (to reduce temperature) comes at the expense of acid and neutralizing salts used in downstream equipment.

[0005] Farone et al. (US5820687, October 13, 1998) and Baniel et al. (WO2010 / 026572A1, September 1, 2009) have described attempts to separate sulfuric acid and sugars using ionic resin separation or hydrochloric acid and sugars by amine extraction and subsequent thermal regeneration of the acid. Both methods are cumbersome and expensive.

[0006] To address these issues, Tetarenko et al. (US9428816B2, August 30, 2016) provided a method for treating ethanol production byproducts by treating WDG or stillage with an α-hydroxysulfonic acid solution to produce fermentable sugars for the production of biofuels or ethanol.

[0007] Processing grains to recover more sugars from starch and fiber in a single process remains a challenge. Summary of the Invention

[0008] According to one aspect of the present invention, there is provided a method for processing grain to produce a feedstock for the production of chemicals and / or fuels, the method comprising the steps of providing grain comprising starch and non-starch carbohydrates, wherein the starch is present in an amount of at least 10% by weight based on the dry weight of the grain; contacting the grain with a solution comprising at least one α-hydroxysulfonic acid; and reacting the grain with the solution under acid hydrolysis conditions, thereby producing a feedstock suitable for the production of chemicals and / or fuels. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The process of the present invention will be better understood by reference to the following detailed description of the preferred embodiments and the accompanying drawings referenced therein, in which:

[0010] Figure 1 and Figure 2 is a block flow diagram illustrating an embodiment of the acid hydrolysis step of the process according to the present invention;

[0011] Figure 3 is a block flow diagram illustrating one embodiment of further processing the product of the present invention by fermentation;

[0012] Figure 4 is a block flow diagram illustrating another embodiment of further processing the product of the present invention by enzymatic hydrolysis and fermentation; and

[0013] Figure 5 is a block flow diagram illustrating yet another embodiment for further processing the products of the present invention by other alternatives of catalytic conversion and / or fermentation. DETAILED DESCRIPTION

[0014] The present invention provides a method for processing cereal grain to produce a feedstock suitable for producing chemicals and fuels. The method allows for processing cereal grain without first requiring conversion, such as by enzymatic conversion, of starch into sugars. Advantageously, cereal grain can be processed according to the method of the present invention without requiring an energy-intensive milling step.

[0015] The methods of the invention allow starch and non-starch carbohydrates in the grain to become more accessible for subsequent utilization, for example, by acid hydrolysis, with or without enzymatic hydrolysis, to produce sugars for further conversion to chemicals and / or fuels.

[0016] Now refer to Figure 1 , a method 10 of the present invention is provided for processing grain 12.

[0017] So-called "grain" refers to cereal grains, grain legumes, oilseed grains, and combinations thereof. Examples of suitable cereal grains include, but are not limited to, wheat, rye, oats, barley, buckwheat, quinoa, chia seeds, and combinations thereof. Examples of suitable grain legumes include, but are not limited to, beans, lentils, lupines, peas, peanuts, and combinations thereof. Examples of suitable oilseed grains include, but are not limited to, rapeseed, corn, cottonseed, soybeans, sunflowers, safflower, grapeseed, black cumin, castor, linseed, camelina, and combinations thereof. Preferably, whole grain grains, grain legumes, and / or oilseed legumes are used as feed for the method of the present invention. In some cases, the shell or husk can be used alone or together with the cereal grains, grain legumes, and oilseed grains as raw materials, provided that the raw materials have the following suitable characteristics.

[0018] Suitable grains 12 have starch and non-starch carbohydrates. Starch is present in an amount of at least 10% by weight based on the dry weight of the grain. The grains 12 also contain non-starch carbohydrates, including but not limited to sugars, lignin, cellulose, hemicellulose, glycogen, chitin, and combinations thereof. Starch content can be readily determined by one of ordinary skill in the art. Examples of methods for measuring starch content include, but are not limited to, polarimetry, HPLC, and the like.

[0019] In contrast to conventional methods, in which the grains are pretreated to convert starch to sugars prior to acid hydrolysis, the grains 12 can be processed according to the method of the present invention without pretreatment. Alternatively, the grains 12 can be pretreated to a suitable particle size, which may include crushing and / or grinding. The appropriate particle size will depend on the specific grains used. In a preferred embodiment, the grains 12 are subjected to an optional particle size reduction step 14. Advantageously, however, the method of the present invention does not require subjecting the grains to an energy-intensive grinding step, for example, as required in conventional methods in which the grains are first ground into a meal before cooking.

[0020] The advantage of the optional particle size reduction step 14 is that it opens the grain to improve access to starch and non-starch carbohydrates in subsequent processing steps. The particle size reduction step 14 can simply be a step of cracking the husk or skin of the grain 12. In another embodiment, the particle size reduction step 14 can separate the grain into two or more fragments. Suitable equipment for particle size reduction includes, for example, but is not limited to, hammer mills, jet mills, grinders, crushers, pulverizers, choppers, shredders, and the like.

[0021] The grain 12 is conveyed directly or indirectly through an optional particle size reduction step 14 to an acid hydrolysis step 16. In the acid hydrolysis step 16, the grain 12 is contacted with a solution containing at least one alpha-hydroxysulfonic acid under acid hydrolysis conditions.

[0022] Suitable α-hydroxysulfonic acids for use in the process of the present invention have the following general formula:

[0023]

[0024] wherein R1 and R2 are independently hydrogen, an alkyl group having 1 to 9 carbon atoms or a hydroxyl group. The α-hydroxysulfonic acid may be a mixture of acids having the above general formula.

[0025] α-Hydroxysulfonic acid can generally be prepared by reacting at least one carbonyl compound or a precursor of a carbonyl compound (e.g., trioxane, paraformaldehyde, metaldehyde, etc.) with sulfur dioxide or a precursor of sulfur dioxide (e.g., sulfur and an oxidizing agent, or sulfur trioxide and a reducing agent) and water according to the following General Reaction 1.

[0026]

[0027] wherein R1 and R2 are independently hydrogen, an alkyl group having 1 to 9 carbon atoms, or a hydroxyl group.

[0028] Illustrative examples of carbonyl compounds that can be used to prepare the α-hydroxysulfonic acids used in the present invention are listed in Table 1:

[0029] Table 1

[0030]

[0031]

[0032] Carbonyl compound and / or its precursor can be the mixture of compound described above or its precursor.For example, mixture can be carbonyl compound or precursor, such as for example known trioxane that heat recovery is formaldehyde at elevated temperature, or can make alcohol dehydrogenation and be converted into the alcohol of aldehyde by method well known to those skilled in the art.This type of example that is converted into aldehyde from alcohol is described below.The example of the source of carbonyl compound can be the mixture of glycolaldehyde and other aldehydes and ketone produced by fast pyrolysis oil, such as described in " Fast Pyrolysis and Bio-oil Upgrading, Biomass-to-Diesel Workshop ", Pacific Northwest National Laboratory, Richland, Washington, September 5 to 6, 2006.Carbonyl compound and its precursor can also be ketone and / or aldehyde with or without the mixture of alcohol preferably in the scope of 1 to 7 carbon atoms that can be converted into ketone and / or aldehyde.

[0033] The preparation of α-hydroxysulfonic acids by the combination of an organic carbonyl compound, SO 2 and water is a general reaction and is exemplified below for acetone.

[0034]

[0035] Alpha-hydroxysulfonic acid appears to be as strong as HCl, if not stronger.

[0036] The grain 12 is mixed with water and at least one alpha-hydroxysulfonic acid in an acid hydrolysis step 16. The starch and non-starch polysaccharides in the grain 12 are converted to at least one fermentable sugar through the acid hydrolysis reaction with the alpha-hydroxysulfonic acid.

[0037] The acid hydrolysis step 16 may include many components, including α-hydroxysulfonic acid that is added or generated in situ. As used herein, the term "in situ" refers to components generated throughout the process; it is not limited to the specific reactor produced or used and is therefore synonymous with the components generated in the process. When generated in situ, the carbonyl compound or initial carbonyl compound (such as trioxane) should be added with sulfur dioxide and water in a certain amount and under conditions that effectively form α-hydroxysulfonic acid. The carbonyl compound or its precursor and sulfur dioxide or its precursor should be added in an amount to produce α-hydroxysulfonic acid (or reconstituted) based on about 1% by weight of the total solution, preferably about 5% by weight, most preferably about 10% by weight to about 55% by weight, preferably about 50% by weight, and more preferably in the range of about 40% by weight. For this reaction, excess sulfur dioxide is not necessary, but any excess sulfur dioxide can be used to drive the equilibrium in reaction 1 to favor the formation of acid at elevated temperatures.

[0038] Various factors influence the conversion of the grain 12 in the acid hydrolysis step 16. The temperature and pressure of the acid hydrolysis step 16 should be within a range effective to form α-hydroxysulfonic acid and hydrolyze the grain starch and non-starch polysaccharides into hexoses and / or pentoses. The acid hydrolysis step 16 is conducted at a temperature of at least 50°C, depending on the α-hydroxysulfonic acid used, although such temperature may be as low as room temperature (e.g., 20°C), depending on the acid and pressure used. Depending on the α-hydroxysulfonic acid used, the temperature of the acid hydrolysis step 16 may preferably range up to and including 150°C. In a preferred embodiment, the temperature ranges from 80°C to 100°C. In a more preferred embodiment, the temperature ranges from 90°C to 130°C. The reaction is preferably conducted at as low a pressure as possible to contain free sulfur dioxide for the formation of the α-hydroxysulfonic acid. The reaction may also be conducted at a pressure as low as 1 barg, preferably 4 barg, to a pressure as high as 10 barg. The temperature and pressure selected will depend on the particular α-hydroxysulfonic acid selected and will be based on metallurgical and containment vessel economic considerations in a manner understood by those skilled in the art.

[0039] The amount of α-hydroxysulfonic acid solution relative to the "dry weight" of the grain 12 determines the final concentration of fermentable sugars obtained. Therefore, it is desirable to have the highest possible grain concentration. This is balanced by the absorptive properties of the grain; mixing, transport, and heat transfer become increasingly difficult as the relative amount of grain solids to liquid increases. The weight percentage of grain to total liquid can range from 1% to 35% by weight, or even higher, depending on the equipment selected and the properties of the grain 12.

[0040] The temperature and reaction time of the acid hydrolysis step 16 may be selected so that a maximum amount of extractable carbohydrates are hydrolyzed and extracted from the grain 12 as fermentable sugars while limiting the formation of degradation products.

[0041] The acid hydrolysis step 16 can be carried out in a single reactor or in multiple reactors. Suitable reactor designs include, for example, but not limited to, intermittent, trickle bed, co-current, countercurrent, stirred tank and fluidized bed reactors. The most economical solution can be achieved by adopting a classification of reactors. In one embodiment, a series of reactors with an elevated temperature profile can be used so that the desired sugar fraction is extracted in each reactor. The outlet of each reactor can then be cooled before merging product stream 24, or product stream 24 can be fed separately to subsequent steps.

[0042] The acid hydrolysis step 16 can be operated in a continuous, semi-continuous, batch or semi-batch mode. Examples of continuous flow systems include continuous stirred tank reactors (CSTRs), plug flow reactors, and combinations thereof. The acid hydrolysis reaction 16 can also be carried out in multiple system vessels and / or reactors, in packed bed flow reactors. In a preferred embodiment, the acid hydrolysis step 16 is practiced using a continuous flow system operating at steady state equilibrium.

[0043] Product stream 24 contains at least one fermentable sugar or monosaccharide, such as a hexose and / or pentose sugar, which is suitable for further processing.

[0044] After the acid hydrolysis step 16, the effluent is sent to the acid removal step 18. The reaction in reaction 1 is a true equilibrium, which results in the easy reversibility of the acid. That is, when heated, the equilibrium shifts towards the starting carbonyl compound, sulfur dioxide and water. If volatile components (e.g., sulfur dioxide) are allowed to leave the reaction mixture by evaporation or other methods, the acid reaction is completely reversed, and the solution becomes effectively neutral. Therefore, by raising the temperature and / or reducing the pressure in the acid removal step 18, sulfur dioxide can be driven off, and due to Le Chatelier's principle, the reaction is completely reversed.

[0045] The fate of the carbonyl compound depends on the properties of the materials used. If the carbonyl group is also volatile (e.g., acetaldehyde), the material is also easily removed in the gas phase. Carbonyl compounds that are slightly soluble in water, such as benzaldehyde, can form a second organic phase and therefore can be separated mechanically. Therefore, the carbonyl compound can be removed in a conventional manner, for example, by continuously applying heat and / or vacuum, steam and nitrogen stripping, solvent washing, centrifugation, etc.

[0046] Thus, the formation of α-hydroxysulfonic acids is reversible because as the temperature increases, sulfur dioxide and / or aldehydes and / or ketones can flash evaporate from the mixture and condense or be absorbed elsewhere for recycling. These reversible acids, which are about as strong as strong mineral acids, have been found to be effective in grain treatment reactions. We have found that these treatment reactions produce very few of the degradation products produced by other conventional mineral acids. In addition, because the acids are effectively removed from the reaction mixture during the acid removal step 18, neutralization with bases and the formation of salts that complicate downstream processing are substantially avoided. The ability to reverse and recycle these acids also allows the use of higher concentrations than would otherwise be economically or environmentally feasible. As a direct result, the temperatures employed in grain treatment can be lowered to reduce the formation of degradation products.

[0047] It has been found that the equilibrium position given in reaction 1 at any given temperature and pressure is highly influenced by the nature of the carbonyl compound used, with steric and electronic effects having a strong influence on the thermal stability of the acid. More steric bulk around the carbonyl group tends to favor lower thermal stability of the acid form. Therefore, the strength of the acid and the temperature at which it readily decomposes can be tuned by selecting the appropriate carbonyl compound.

[0048] The acid removal step 18 in the process 10 of the present invention represents a particular advantage over conventional mineral acid treatments. Advantageously, the process of the present invention results in a potentially less expensive treatment system by eliminating the subsequent acid neutralization step and salt formation.

[0049] The effluent from acid hydrolysis step 16 is introduced into acid removal step 18 where the acid is removed in its component forms and then recovered (and optionally washed) as a component or in its reconstituted form and recycled to acid hydrolysis step 16 via recycle stream 22. Product stream 24, which contains at least one fermentable sugar (e.g., hexoses and optionally pentoses), is substantially free of α-hydroxysulfonic acid.

[0050] The acid removal step 18 can be performed by applying heat and / or vacuum to reverse the formation of α-hydroxy sulfonic acid to its starting material to produce a product stream 24 containing fermentable sugars that is substantially free of α-hydroxy sulfonic acid. Specifically, the product stream 24 is substantially free of α-hydroxy sulfonic acid, meaning that no more than about 2 wt% is present in the product stream 24, preferably no more than about 1 wt% is present in the product stream 24, more preferably no more than about 0.2 wt%, and most preferably no more than about 0.1 wt%.

[0051] The temperature and pressure will depend on the specific α-hydroxysulfonic acid used. Preferably, the degree of heating is reduced to preserve the sugars obtained in the acid hydrolysis step 16. The acid removal 18 can be carried out at a temperature in the range of 50°C, preferably 80°C, more preferably 90°C to 150°C, preferably to 120°C. The pressure can be in the range of 1 bar (atmospheric pressure) to 3 bars, more preferably 1 bar to 2 bars. It will be understood by those skilled in the art that the acid hydrolysis step 16 and the acid removal step 18 can be carried out in the same container or in separate containers, or in many different types of containers, depending on the reactor configuration and staging, as long as the system is designed so that the reaction is carried out under conditions that are conducive to the formation and maintenance of the α-hydroxysulfonic acid and the removal of the reverse reaction.

[0052] For example, the reaction in the acid hydrolysis step 16 can be operated at a temperature of 100° C. and a pressure of 4 barg in the presence of α-hydroxyethanesulfonic acid, while the acid removal step 18 can be operated at 110° C. and a pressure of 0.5 barg. It is further contemplated that the α-hydroxysulfonic acid formed by reactive distillation can be advantageously reversed. Optional additional carbonyl compound, SO 2 , and water can be added to the recycle stream 22 as necessary. The removed starting material and / or α-hydroxysulfonic acid can be condensed or washed by contact with water and recycled to the acid hydrolysis 16 as the recycle stream 22.

[0053] Now go to Figure 2 , the product stream 24 may be used directly in further processing, or the product stream 24 may be sent to a solids separation step 26 for clarifying the product stream by removing grain residues, such as protein.

[0054] The solids separation step 26 may include one or more solids separation devices for purifying the liquid product stream to remove impurities by adsorption, distillation, crystallization, evaporation, precipitation, separation, or chemical reaction.

[0055] The solids separation step produces a solids stream 28 having a high protein content, preferably greater than 30 wt% protein, more preferably greater than 40 wt% protein, which can be further purified.

[0056] The product stream 24, 124 may be subjected to a number of different processes for further processing into chemicals and / or fuels, non-limiting examples of which are discussed further below.The product stream 24, 124 may be subjected to a process selected from biological, biochemical, chemical, and combinations thereof.

[0057] In one embodiment of the process for further processing, as Figure 3 As illustrated, product streams 24, 124 are passed to a fermentation step 32 to convert the sugars into alcohols that can be used, for example, as biofuel.

[0058] In fermentation step 32, one or more microorganisms (e.g., yeast or bacteria) can be used to convert sugars into biofuels such as ethanol, other alcohol fermentation products, such as n-butanol, isobutanol, isopropanol, and / or organic acids, such as lactic acid, succinic acid, acetic acid, and propionic acid. The microorganisms convert sugars present in product streams 24, 124 (including but not limited to glucose, xylose, arabinose, mannose, and galactose) into fermentation products.

[0059] Suitable microorganisms include antibacterials, yeasts and fungi. Examples of suitable antibacterials include, but are not limited to, Clostridia, Escherichia coli (Escherichia coli), colibacillary recombinant strains, genetically modified strains of Zymomonas mobilis (such as those disclosed in Zhang (US7,223,575B2, May 29, 2007) and Viitanen (US7,741,119B2, June 22, 2010; US7,741,084B2, June 22, 2010) and combinations thereof. Examples of suitable yeasts or fungi include, but are not limited to, the species Saccharomyces, Kluyveromyces, Candida, Pichia, Schizosaccharomyces, Hansenula, Kloeckera, Schwanniomyces, Yarrowia, Aspergillus, Trichoderma, Humicola, Acremonium, Fusarium, Penicillium, and combinations thereof. Fermentation can also be performed with engineered recombinant yeasts to ferment hexose and pentose sugars into ethanol. Recombinant yeast that can ferment one or both of the pentose sugars xylose and arabinose to ethanol are described in Ho et al. (US 5,789,210 August 4, 1998), Otero et al. (US 6,475,768 Bl November 5, 2002), Gorwa-Grauslund et al. (EP 1727890 Bl May 14, 2008), and Boles et al. (WO 2006 / 096130 Al September 14, 2006). Xylose utilization can be mediated by the xylose reductase / xylitol dehydrogenase pathway (e.g., Ho et al. (WO 97 / 42307 November 3, 1997) or the xylose isomerase pathway (e.g., Concilio et al. (WO 2007 / 028811 A1 September 6, 2006) and Klaassen et al. (WO 2009 / 109631 A1 September 11, 2009). It is also contemplated that the fermenting organism can also produce fatty alcohols, for example, as described in Hu et al. (WO 2008 / 119082 A2 October 2, 2008) and Keasling et al. (WO 2007 / 136762 A2 May 18, 2007).In another embodiment, the fermentation can be performed by yeast capable of fermenting primarily C6 sugars, for example by using commercially available strains such as. and

[0060] Preferably, the fermentation step 32 is carried out at or near the optimal temperature and pH for the selected fermentation microorganism. For example, the temperature can be in the range of 25°C to 55°C. The pH can be in the range of 3.0 to 7.0. The dosage of the fermentation microorganism will depend on many parameters, such as the activity of the fermentation microorganism, the desired fermentation time, the volume of the reactor, etc. It should be understood that these parameters can be adjusted as needed by those skilled in the art to achieve optimal fermentation conditions.

[0061] The fermentation step 32 can be carried out in batch, continuous or fed-batch mode with or without agitation. The fermentation step 32 can employ a series of fermentation reactors (not shown).

[0062] The fermentation step 32 produces an overhead CO2 stream and a liquid alcohol-containing stream, preferably containing at least one alcohol having 2 to 18 carbon atoms. The liquid alcohol-containing stream is sent to a recovery step 34. The recovery step 34 may include one or more of a distillation column, a solid / liquid separation device, an evaporator, a centrifuge, a decanter, an oil skimmer, a filter, a membrane, and the like.

[0063] When the product to be recovered in the alcohol-containing stream is a distillable alcohol, such as ethanol, the alcohol may be recovered from the aqueous stream by distillation in recovery step 34. When the product to be recovered in the alcohol-containing stream is not a distillable alcohol, such as a fatty alcohol, the alcohol may be recovered in recovery step 34 by removing the alcohol as a solid or as an oil.

[0064] In one embodiment of the recovery step 34, the effluent from the fermentation step 34 is sent to a distillation column to separate ethanol from the effluent. The bottoms stream from the distillation column is then sent to a solid / liquid separation to separate the solid stream from the liquid stream. The liquid stream from the solid / liquid separation is sent to an evaporator to produce a concentrated liquid or syrup. The concentrated liquid or syrup is then sent to a centrifuge for removing oil from the de-oiled syrup. In one embodiment, oil can also be recovered from the evaporator. The de-oiled syrup is rich in protein and can be used as, for example, animal feed. The oil removed from the liquid stream can be used as a bio-oil feedstock for processing into fuels and / or chemicals.

[0065] exist Figure 1 In embodiments in which product stream 24 is passed to a fermentation step without first passing through a solids separation step, the solids recovered from the effluent of recovery step 34 by solid / liquid separation will include unconverted solids from acid hydrolysis 16 of grain 12, as well as fermentation solids.

[0066] exist Figure 2 In embodiments where product stream 124 is passed to a fermentation step after passing through solids separation step 26, the solids recovered by solid / liquid separation in recovery step 34 will include fermentation solids.

[0067] Now refer to Figure 4 Another embodiment of further processing provides subjecting product stream 24 and / or solid stream 28 to enzymatic hydrolysis 36 to provide a hydrolysate.

[0068] The enzymatic hydrolysis 36 and fermentation 32 steps can be performed in separate vessels or in the same vessel. In one embodiment, the enzymatic hydrolysis 36 can be partially completed and the partially hydrolyzed stream can be fermented in the fermentation step 32. In another embodiment, simultaneous saccharification and fermentation (SSF) can be performed, wherein the enzymatic hydrolysis 36 can be performed until the final percent solids target is reached, and then the hydrolyzed biomass can be fermented in the fermentation step 32.

[0069] In the enzymatic hydrolysis step 36, the product stream 24 and / or the solid stream 28 are contacted with a cellulase, a beta-glucosidase, a xylanase, a glucoamylase, or a combination thereof. Depending on the temperature, the product stream 24 and / or the solid stream 28 can be adjusted to a temperature within the optimal range for enzyme activity. Generally speaking, a temperature range of 15°C to 100°C, preferably 20°C to 85°C, and more preferably 30°C to 70°C is suitable for most cellulases. The temperature can be adjusted by heat exchange before introduction into the enzymatic hydrolysis step 36. Alternatively, the enzyme can be added to the product stream 24 before, during, or after adjusting the temperature and pH of the product stream 24 in the hydrolysis reaction vessel. Preferably, the enzyme is contacted with the product stream 24 after the temperature and pH have been adjusted. The desired operating conditions, including temperature and pH, will be determined based on the selected enzyme.

[0070] Cellulase is an enzyme or mixture of enzymes that can hydrolyze cellulose. A cellulase mixture can include cellobiohydrolase (CBH), glucanase (GBH), endoglucanase (EG) and beta-glucosidase. The term "beta-glucosidase" refers to an enzyme that hydrolyzes the glucose dimer, cellobiose, into glucose.

[0071] The enzymatic hydrolysis step 36 can also be performed in the presence of one or more xylanases. Examples of xylanases include, for example, but are not limited to, xylanases 1 and 2 (Xyn1 and Xyn2) and beta-xylosidase.

[0072] Sources of cellulases include, for example, but are not limited to, species such as Aspergillus, Humicola, Trichoderma, Myceliophthora, Chrysosporium, Bacillus, Thermobifida, Thermotoga, Acremonium, Aureobasidium, Bjerkandera, Ceriporiopsis, Coprinus, Coriolus, Cryptococcus, Filibrassis, and the like. asidium, Fusarium, Magnaporthe, Mucor, Neocallimastix, Neurospora, Paecilomyces, Penicillium, Phanerochaete, Phlebia, Piromyces, Pleurotus, Schizophyllum, Talaromyces, Thermoascus, Thielavia, Tolypocladium, Trametes, and combinations thereof.

[0073] The cellulase dosage is selected to convert the cellulose in the product stream 24 and / or the solid stream 28 into glucose. For example, a suitable cellulase dosage may be in the range of 10 to 150 biomass hydrolysis units (BHU) per gram of cellulose. The term biomass hydrolysis unit refers to the enzyme concentration.

[0074] In practice, enzymatic hydrolysis 36 can be carried out in one or a series of hydrolysis reactors. The number of hydrolysis reactors in the system depends on the cost of the reactor, the volume of the aqueous slurry, and other factors. The enzymatic hydrolysis 36 carried out with cellulase produces an aqueous sugar stream (hydrolyzate) comprising glucose, unconverted cellulose, lignin, and other sugar components. The hydrolysis can be carried out in two stages (see, for example, Brink (US5,536,325 July 16, 1996)) or can be carried out in a single stage.

[0075] In SSF, a combination of enzymes and yeast is used to convert polysaccharides to sugars and simultaneously ferment the sugars to ethanol and carbon dioxide, producing solids from the grain (in the presence of ethanol). Figure 2 In embodiments, the fermentation products include solids without first being separated), water, and carbon dioxide which may be removed or captured.

[0076] Now refer to Figure 5 , another embodiment of further processing provides subjecting the product streams 24, 124 to catalytic hydrogenation and condensation. In this embodiment, the product streams 24, 124 are subjected to a hydrogenolysis step 42, wherein they are contacted with hydrogen in the presence of a hydrogenolysis catalyst to form a plurality of oxygenated intermediates. The oxygenated intermediates are then further processed in a condensation step 44 to generate a fuel blend catalyzed by a catalyst comprising acid and / or basic functional sites to produce a liquid fuel. In this manner, the product streams 24, 124 are converted into higher hydrocarbons that can be used as biofuel components. As used herein, the term "higher hydrocarbons" refers to hydrocarbons having an oxygen-to-carbon ratio less than that of at least one component of the grain feedstock.

[0077] In one such example, the product streams 24, 124 are further processed to produce a mixture of C4+ compounds that can be used for biofuels, such as described in Chheda et al. (US2011 / 0154721A1 June 30, 2011 and US2011 / 0282115A1 November 17, 2011), the disclosures of which are hereby incorporated by reference. As another such example, the product streams 24, 124 can be further processed to produce a mixture of C4+ compounds that can be used for biofuels, such as described in Cortright et al. (US2008 / 0216391A1 September 11, 2008), the disclosures of which are hereby incorporated by reference. The solid stream 28 can also be suitable for fast pyrolysis reactions to produce fuels and chemicals.

[0078] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the detailed description herein. It should be understood that the detailed description herein is not intended to limit the invention to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

[0079] Example

[0080] The following non-limiting examples of embodiments of the methods of the present invention claimed herein are provided for illustrative purposes only.

[0081] General methods and materials

[0082] In the examples, aldehydes or aldehyde precursors and sulfur dioxide were obtained from Sigma-Aldrich Co.

[0083] Corn kernels and sorghum kernels were obtained from commercial sources. The composition of the materials was analyzed using standard NREL methods (TP-510-48087), and the results of the following average compositions on a dry basis are presented in Table 2:

[0084] Table 2

[0085]

[0086] Analytical methods

[0087] Determination of oxygenated species in aquifers .

[0088] Flow through the mobile phase stream of Bio-rad post (Aminex HPX-87H, 300mm x 7.8mm) by injection and analyze sample or standard. Reverse-phase HPLC system (Shimadzu) is equipped with RI detector and UV detector, and signal is recorded as peak value on data acquisition and data processing system. Use external calibration to come quantitative component by the calibration curve of the injection of target component based on known concentration. Some components are calculated by using single point standard.

[0089] HPLC instrument conditions:

[0090] Column: Bio-Rad Aminex HPX-87H (300 mm x 7.8 mm)

[0091] Flow rate: 0.6ml / min

[0092] Column oven: 30°C

[0093] Injection volume: 10 μl

[0094] UV detector: @320NM

[0095] RI detector: Mode-A; Range-100

[0096] Running time: 70 minutes

[0097] Mobile phase: 5 mM sulfuric acid aqueous solution

[0098] The sample was injected directly or diluted with water to remove particulate matter. If precipitate was present in the sample or diluted sample, the sample was passed through a 0.2 μm syringe filter. The sample was analyzed for glucose, xylose, arabinose, acetic acid, hydroxymethylfurfural, and furfural.

[0099] General procedure for the formation of α-hydroxysulfonic acids

[0100] Aldehydes and ketones will readily react with sulfur dioxide in water to form α-hydroxysulfonic acids according to Reaction 1 above. These reactions are generally rapid and somewhat exothermic. The order of addition (SO2 to carbonyl or carbonyl to SO2) does not appear to affect the outcome of the reaction. If the carbonyl compound is capable of undergoing the aldol reaction, the preparation of a concentrated mixture (>30 wt %) is performed at subambient temperatures to minimize side reactions. The progress of the reaction is followed using in situ infrared spectroscopy (ISIR), which employs a probe (Sentinal probe from Mettler Toledo Autochem) inserted into the pressure reaction vessel or system. In addition to being able to see the starting materials: water (1640 cm -1 ), carbonyl (from about 1750cm -1 to 1650cm -1 , depending on the organic carbonyl structure) and SO2 (1331cm -1 ), the formation of α-hydroxysulfonic acid is accompanied by SO3 - The formation of the characteristic band of the group (about 1200 cm -1 broad band) and the extension of α-hydroxyl groups (around 1125 cm -1 In addition to monitoring the formation of α-hydroxysulfonic acid, the relative position of the equilibrium at any temperature and pressure can be easily assessed by the relative peak heights of the starting components and the acid complex. The unequivocal presence of α-hydroxysulfonic acid under biomass hydrolysis conditions can also be confirmed using ISIR, and the growth of sugars in the reaction mixture can be monitored by monitoring the appropriate IR bands.

[0101] Example 1

[0102] Formation of 40% by weight of α-hydroxyethanesulfonic acid from acetaldehyde .

[0103] To a 2-liter C-276 Parr autoclave equipped with DiComp IR optics was added 1346.1 grams of an ice-cold, denitrogenated aqueous solution containing 17.96% by weight of acetaldehyde. The top was placed on the reactor and the vessel was connected to two single-ended Hoke vessels, which contained a total of 362.04 grams of sulfur dioxide. The pressure integrity of the sealed reactor was ensured by testing with nitrogen for 15 minutes at 50 psig. The reactor was cooled to below 5°C using external cooling and the nitrogen cap was vented. IR acquisition was started and after a few minutes, sulfur dioxide was injected into the acetaldehyde / water solution from the attached Hoke vessel. The pressure in the reactor reached about 3 bar and then quickly dropped to atmospheric pressure as the ISIR indicated the appearance of SO2, which was then rapidly consumed. During the acid formation period, the temperature of the reaction mixture increased by about 42°C (3°C to 45°C). The ISIR and reaction pressure indicated that the reaction was complete in about 10 minutes. The final solution showed an infrared spectrum with the following characteristics:-1 The broad band centered at 1038 cm -1 and 1015cm -1 The reaction mixture was cooled to room temperature and the contained atmosphere was vented through a caustic scrubber. The reactor was purged to remove any unreacted SO₂ or acetaldehyde by two cycles of pressurizing with nitrogen to 50 psig followed by venting. This yielded 1698.78 g of a mixture which, by proton NMR analysis, contained 39.3 wt% α-hydroxyethanesulfonic acid.

[0104] Example 2

[0105] Formation of 40% by weight of α-hydroxyethanesulfonic acid from metaldehyde

[0106] To a 2-liter C-276 Parr autoclave equipped with DiComp IR optics, 999.98 grams of denitrogenated water and 212.02 grams of metaldehyde (water-insoluble) were added. The vessel head was attached and connected to two single-ended Hoke vessels containing a total of 338.19 grams of sulfur dioxide. The reactor was sealed and pressure integrity was confirmed by testing with nitrogen for 15 minutes at 100 psig. The nitrogen cap was vented very slowly to prevent any loss of free metaldehyde that was not wetted by water. Agitation was started at 1000 rpm and IR acquisition was started. After 5 minutes, sulfur dioxide from the attached Hoke vessel was added to the metaldehyde / water slurry. The pressure in the reactor reached approximately 2.5 bar. ISIR indicated the presence of SO 2 . The temperature of the reaction mixture was slowly raised to 30 ℃ and then increased to 50 ℃ in 10 ℃ increments. During the transition from 40°C to 50°C, the reaction temperature suddenly increased to 65°C, and the ISIR indicated the formation of acid. This was accompanied by the consumption of SO2 and a drop in the reactor pressure. The ISIR of the reaction mixture indicated that the reaction was complete within a few minutes. The final solution showed an infrared spectrum with the following characteristics: -1 The broad band centered at 1038 cm -1 and 1015cm -1 The reaction mixture was cooled to room temperature and the contained atmosphere was vented through a caustic scrubber. The reactor was purged to remove any unreacted SO₂ or acetaldehyde by two cycles of pressurizing with nitrogen to 50 psig followed by venting. This produced 1468.74 g of a light yellow homogeneous liquid which, by proton NMR analysis, contained 36.7 wt% α-hydroxyethanesulfonic acid.

[0107] Example 3 to Example 8

[0108] Hydrolysis of corn and sorghum grains with α-hydroxyethanesulfonic acid (HESA) solution

[0109] This is the general procedure for Examples 3 through 8. Approximately 100 to 150 grams of the resulting corn kernels (Examples 3 through 5) or sorghum kernels (Examples 6 through 8) (dry weight basis reported in Column B) were placed in a 1000 ml autoclave equipped with a DiCompIR probe. Approximately 350 to 400 grams of a 4.5% by weight solution of α-hydroxyethanesulfonic acid (the exact concentration is listed in Column C of Table 3) was added at room temperature.

[0110] The reactor was sealed with a top containing a magnetically coupled 4-blade down-pitch impeller, equipped with a heating strip and purged by adding nitrogen to 50 psig and then venting to room temperature. The reaction mixture was heated to a target temperature of 115° C. to 125° C. (column D) with stirring (1000 rpm) and held at temperature for the necessary time (column E).

[0111] During this period, in situ IR showed the presence of acid, SO2 and acetaldehyde in the equilibrium mixture, as well as a sugar characteristic band at 1000 cm -1 At the end of the reaction period, acid reversal was accomplished by opening the reactor gas cap to an overhead condensation system to recover the acid while maintaining the reactor temperature at 100°C. The overhead recovery system consisted of 1 / 4" C-267 tubing extending down into a 500 ml three-necked round-bottom flask filled with 150 g of DI water, immersed in a wet ice bath, and equipped with a dry ice / acetone condenser on the outlet.

[0112] The progress of the acid reversal was monitored by using in situ IR in the reactor. The reversal was continued until the in situ IR showed no trace of α-hydroxyethanesulfonic acid or SO2 remaining in the reaction mixture. The reactor condensation system was then closed and the reactor was cooled to room temperature. In all cases, the overhead condensate contained >70% of the α-hydroxyethanesulfonic acid charged to the system as analyzed by proton NMR (column F). The cooled reactor was opened and the contents filtered through a medium glass frit funnel using a vacuum aspirator to draw the liquid through the funnel. The reactor was rinsed with three separate portions of water, noting the weight of all rinses, which were used to complete the transfer of the solids and the solids in the rinse funnel. The residual solid was dried in air to constant weight and then analyzed for moisture (the recovered weight on a dry basis is listed in column G). HPLC analysis of the filtrate plus rinses was used to obtain the hydrolysis results (columns H to J).

[0113] Table 3

[0114]

[0115]

[0116] The examples show that more than 75% of the glucans (from starch or cellulose) in corn and sorghum grains were converted to glucose, with the remaining glucans being soluble oligomers and little sugar degradation, as indicated by the low furfural concentration in the filtrate. Furthermore, the sugar stream was fermented to produce ethanol at the same yield level as a sugar stream from a dry corn ethanol plant, and more than 90% of the monosaccharides were consumed during fermentation.

[0117] Additional evidence

[0118] Based on the results presented by Blackbourn et al. (US9,290,821B2 March 22, 2016), the present inventors anticipate that similar results will be achieved for other α-hydroxysulfonic acids as those presented herein for α-hydroxyethanesulfonic acid. Specifically, Table 1 of Blackbourn et al. (repeated below) shows that the recoveries of xylose, glucose, and furfural can be comparable for α-hydroxyethanesulfonic acid, α-hydroxymethanesulfonic acid, and bis-α-dihydroxyethanesulfonic acid. Although Blackbourn et al. used different starting materials than the present invention (i.e., biomass and WDG), it is expected that the relative effectiveness of other α-hydroxysulfonic acids will be reasonably anticipated for grains with starch and non-starch carbohydrates in the present method.

[0119] Table 4 (copied from Blackbourn et al.)

[0120]

[0121]

[0122] *Based on %w of xylan in feed (0.88 g of xylan yields 1.0 g of xylose, theoretically)

[0123] **Based on %w glucan in feed

[0124] *** Allow the reactor to reach the specified temperature and shut down immediately.

Claims

1. A method for processing cereal grain to produce a feedstock for the production of chemicals and / or fuels, the method comprising the steps of: - providing a cereal grain comprising starch and non-starch carbohydrates, wherein the starch is present in an amount of at least 10% by weight based on the dry weight of the cereal grain; - contacting the grains with a solution containing at least one α-hydroxysulfonic acid; as well as - reacting the grain with the solution under acid hydrolysis conditions, thereby producing a feedstock suitable for the production of chemicals and / or fuels.

2. The method of claim 1, wherein the grain is selected from the group consisting of cereal grains, grain legumes, oilseed grains, and combinations thereof.

3. The method of claim 1, further comprising the step of removing the α-hydroxy sulfonic acid from the product by heating and / or reducing pressure to produce an acid-depleted product containing at least one fermentable sugar that is substantially free of the α-hydroxy sulfonic acid.

4. The method according to claim 3, further comprising the step of recycling the removed α-hydroxysulfonic acid as a component or in a recombinant form thereof to the contacting step.

5. The method of claim 3, further comprising the step of fermenting the deacidified product to produce at least one alcohol.

6. The method of claim 3, further comprising the step of fermenting the deacidified product to produce at least one organic acid.

7. The method according to claim 3, further comprising the step of hydrolyzing the deacidified product.

8. The method of claim 7, further comprising fermenting the hydrolysate to produce at least one alcohol.

9. The method of claim 1, wherein the solution has an α-hydroxysulfonic acid concentration in the range of 1 wt% to 55 wt%.

10. The method of claim 1, wherein the α-hydroxysulfonic acid is produced from a carbonyl compound or a precursor of a carbonyl compound with sulfur dioxide and water.

11. The method of claim 1, wherein the α-hydroxysulfonic acid is generated in situ.

12. The method of claim 1, wherein the contacting step is performed at a temperature in the range of about 50°C to about 150°C and a pressure in the range of 1 barg to about 10 barg.

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