TWI549934B - Method of preparing butanol from a butyric acid-containing aqueous fermentative liquid - Google Patents

Description

Method for preparing butanol from aqueous fermentation broth containing butyric acid

The present invention relates to a method for producing butanol, and more particularly to a method for preparing butanol from an aqueous fermentation broth containing butyric acid, wherein the aqueous fermentation broth containing butyric acid is carried out using a microorganism in a carbohydrate Obtained by fermentation reaction.

Today, with limited resources, due to the declining oil resources, in order to solve the energy problem, there has been research on the production of bioethanol as a fuel. The term "raw ethanol" refers to ethanol produced by fermenting sugars in crops through microorganisms, and can be used as a fuel alone or in combination with gasoline.

However, the use of ethanol as a fuel is not without drawbacks. One known disadvantage is that there is usually more or less moisture in the environment. When the ethanol blended gasoline is in contact with the water in the environment, the water is absorbed into the ethanol mixture. In gasoline, ethanol and water are mutually soluble and separated from gasoline, which is not conducive to the subsequent use of mixed gasoline. In contrast, butanol mixed gasoline does not absorb water even when water is introduced therein, so that the separation of butanol from gasoline does not occur. Therefore, in the case of using butanol mixed gasoline, storage, transportation, supply systems, and traffic workers who can use butanol mixed gasoline No additional equipment is required in the appliance. In addition, butanol has a lower vapor pressure than ethanol, thereby reducing the likelihood of causing gas resistance in automotive engines. Furthermore, butanol has a similar air-fuel ratio to gasoline, which means that a relatively larger amount of butanol can be mixed with gasoline without affecting engine performance.

Although the raw material butanol has the above advantages, since butanol is more toxic to the organism than ethanol, the strain producing butanol loses its effect of preparing butanol at a certain point of time, making it difficult to be in the fermentation broth. Accumulate to a sufficiently high concentration of butanol. For example, when Clostridium acetobutyricum is used to carry out typical ABE (acetone-butanol-ethanol) fermentation, the productivity of ABE is as low as 0.2 g/hL (g/hr-liter), and the fermentation broth The concentration of butanol in the process does not exceed about 1.3%, requiring a relatively large fermentation reactor. In addition, since the concentration of butanol in the fermentation broth is not high, the energy requirement for separating and concentrating butanol from the fermentation broth is also high.

For the fermentation broth with a low concentration of butanol, it is proposed to distill and recover the raw material butanol contained in the fermentation broth, however, the energy required to separate 1 liter of butanol by this method is 5,000 kcal or higher. It is not far from the burning heat of n-butanol of 6,400 kcal / liter, so it is not economical. It has also been proposed to recover butanol from the fermentation broth by liquid-liquid extraction. For example, US Patent No. 4,260,836 to Sidney Levy discloses a liquid-liquid extraction process using a fermentation broth containing a fluorocarbon having a high butanol extraction coefficient; awarded to Richard J. Cenedella, U.S. Patent No. 4,628,116. No. Patent discloses a liquid-liquid extraction method for liquid-liquid extraction of butanol and butyric acid from a fermentation broth using a vinyl bromide solution; "In Situ Extractive Fermentation of Acetone and Butanol" (Biotech, and Bioeng., Vol. 31, p. 135-143, 1988) discloses a A butanol liquid-liquid extraction method using oleyl alcohol. However, since the butanol concentration in the fermentation broth is too low (not more than about 2%), the separation and purification costs of such liquid-liquid extraction methods are still high. In addition, extraction solvents with high butanol extraction coefficients may also deactivate the strains used to prepare butanol, making liquid-liquid extraction methods less attractive.

US Patent No. 5,753,474 to David Edward Ramey, which teaches a two-step fermentation process comprising first using Clostridium tyrobutylicum as a strain to produce only butyric acid, and then using Clostridium acetobutylicum as a strain to select Only produce butanol. Among them, the use of a fermentation reactor for immobilizing the strain on a fibrous bed can increase the productivity to 6 g/hL, but the maximum concentration of butanol in the fermentation broth still does not exceed about 2%.

Further, it has been proposed to first extract the butyric acid in the fermentation broth and then convert the butyric acid into butanol. Among them, according to the literature "Extractive Fermentation for Butyric Acid Production from Glucose by Clostridium tyrobutylicum" (Biotechnol Bioeng. 2003 Apr 5; 82(1): 93-102) Transferring the fermentation broth discharged from the fiber bed reactor to the hollow fiber membrane extraction column; using a water-insoluble trialkylamine (for example, Alamine 336) as an extractant in the extraction column to carry out the reaction Reactive extraction to obtain a trialkylammonium butyrate. Then, the trialkylammonium butyrate is transferred to another hollow fiber membrane extraction column using sodium hydroxide as an extractant to regenerate the trialkylamine to obtain a sodium butyrate aqueous solution having a high concentration. Thereafter, hydrochloric acid was added to an aqueous solution of sodium butyrate to obtain an aqueous solution of butyric acid. Although the high-purity butyric acid can be produced by the above method, a high amount of acid and alkali are required (it is necessary to consume 1 mole of sodium hydroxide and 1 mole of hydrochloric acid for the preparation of 1 molar acid), which is not preferable.

Therefore, there is still a need for a commercially valuable process for producing butanol which is capable of producing butanol from a fermentation broth in high yield. The present invention provides a method for preparing a raw material butanol from an aqueous fermentation broth containing butyric acid in a high yield in response to the research and development of the demand, wherein most of the materials added in each step can be separated in subsequent operations. Come out, so that it can be recycled and reused, which is more economical.

An object of the present invention is to provide a method for preparing butanol from an aqueous fermentation broth containing butyric acid, wherein the aqueous fermentation broth containing butyric acid is obtained by performing a fermentation reaction using a microorganism in a carbohydrate, and the method comprises the following Step: a) mixing an extraction solvent containing a water-insoluble trialkylamine with the aqueous fermentation broth containing butyric acid for liquid/liquid extraction to obtain an aqueous phase and a trialkylammonium salt a non-aqueous phase of the butyrate; b) heating the non-aqueous phase of step a) to decompose the trialkylammonium butyrate therein to give butyric acid and a trialkylamine; c) the step b) the obtained butyric acid is esterified with methanol to obtain methyl butyrate; and d) the methyl butyrate obtained in the step c) is subjected to hydrogenolysis to obtain butanol and methanol.

1‧‧‧Aqueous carbohydrate solution

2, 4‧‧‧ Aqueous fermentation broth

3‧‧‧Inorganic acid

5‧‧‧ extraction solvent

6‧‧‧ extract

7‧‧‧The remnant

8‧‧‧butyric acid

9‧‧‧Methanol

10‧‧‧ Methyl butyrate

11‧‧‧ Hydrogen

12‧‧‧ Mixture of butanol and methanol

13‧‧‧butanol

100‧‧‧ Fermentation reactor

200‧‧‧pH adjustment slot

300‧‧‧ extractor

400‧‧‧heater

500‧‧‧esterification reactor

600‧‧‧hydrogenation reactor

700‧‧‧Distillation tower

1 is a schematic diagram of a reaction scheme according to an embodiment of the present invention, in which a carbohydrate aqueous solution 1 is used as a raw material, and sequentially passed through a fermentation reactor 100, a pH adjusting tank 200, an extractor 300, a heater 400, and esterification. Butanol 13 is provided in stages of reactor 500, hydrogenolysis reactor 600, and distillation column 700.

Figure 2 is a schematic diagram of an extraction process in accordance with an embodiment of the present invention.

The invention will be described in detail below with reference to the specific embodiments of the present invention. The invention may be practiced in various different forms without departing from the spirit and scope of the invention. The person stated. In addition, the terms "a", "an" and "the"

The present invention provides a method for preparing butanol from an aqueous fermentation broth containing butyric acid, wherein the aqueous fermentation broth containing butyric acid is obtained by performing a fermentation reaction using a microorganism in a carbohydrate, and the method comprises the following steps: a) mixing an extraction solvent containing a water-insoluble trialkylamine with the aqueous fermentation broth containing butyric acid for liquid/liquid extraction to obtain an aqueous phase and a non-aqueous solution containing trialkylammonium butyrate Phase b) heating the non-aqueous phase of step a) to decompose the trialkylammonium butyrate to give butyric acid and trialkylamine; c) esterifying the butyric acid obtained in step b) with methanol The reaction yields methyl butyrate; and d) the hydrogenolysis of methyl butyrate obtained in step c) to give butanol and methanol.

In the process of the invention, butanol is prepared from an aqueous fermentation broth containing butyric acid. Wherein, the aqueous fermentation broth containing butyric acid can be obtained by any fermentation reaction using a microorganism in a carbohydrate. Wherein, in a fermentation reactor filled with a carrier and immobilized with a microorganism capable of converting a carbohydrate into butyric acid by a fermentation reaction, an aqueous solution of carbohydrate is added to the reactor to carry out a fermentation reaction, providing a desired An aqueous fermentation broth containing butyric acid. Appropriate carbohydrates are used depending on the microorganisms used. Preferably, a mixed system comprising a strain having a butyric acid-producing ability and a strain having a carbon-fixing ability is used in the fermentation reactor to convert the carbohydrate into butyric acid in a low carbon loss manner. Here, the term "carbon-fixing ability" means having the ability to convert CO and/or CO ₂ into a carbon source and convert it into an organic substance.

Examples of butyric acid producing strains include, but are not limited to, Clostridium tyrobutylicum , Clostridium butylicum , Clostridium acetobutyricum , Clostridium beijerinckii . And combinations of the foregoing. Examples of strains having carbon sequestration ability include, but are not limited to, Clostridium Coskatii , Clostridium Ljungdahlii , Clostridium difficile , Clostridium authoethanogenium , Clostridium ragsdalei or a combination of the foregoing.

The carbohydrate can be, for example, a saccharide, including monosaccharides, disaccharides, polysaccharides, and mixtures thereof. Wherein, the monosaccharide may be, for example, pentose, hexose, glucose, xylose, galactose, or any mixture of the foregoing; the disaccharide may be, for example, lactose or sucrose. , cellobiose, or any mixture of the foregoing; the polysaccharide may be, for example, starch, glycogen, cellulose, or any mixture of the foregoing. Examples of the aqueous carbohydrate solution include, for example, an aqueous glucose solution, a sugar cane juice, a corn steep liquor, or a pentose-hexose mixture obtained by hydrolyzing a lignin material. The aqueous carbohydrate solution can also be A solution containing soluble sugars obtained by treating biomass with a saccharification process. Suitable green biomasses include, but are not limited to, for example, corn stover, corncob, straw, corn fiber, and the like.

In addition to the saccharide, the aqueous carbohydrate solution may also contain an organic acid such as lactic acid or acetic acid. In an embodiment of the invention, the aqueous carbohydrate solution may comprise lactic acid and at least one saccharide, and wherein the weight ratio of lactic acid to the at least one saccharide is from 0.1:1 to 10:1, such as 0.3: 1 to 3:1, more preferably 0.5:1 to 1.5:1, in one example, the weight of lactic acid is greater than or equal to the weight of the at least one saccharide. It has been found that the amount of carbon dioxide produced by the fermentation reaction of the organic acid (for example, lactic acid) and the saccharide in the aqueous carbohydrate solution is lower than that of the fermentation reaction using the saccharide as a single carbohydrate, and thus the carbon can be lowered. Decrease in yield, increase butyric carbon yield. As shown in the following examples, in a specific embodiment of the present invention, a solution containing glucose and lactic acid is used as a carbohydrate aqueous solution, and a fermentation reaction is carried out using Clostridium tyrosii as a microorganism to provide an aqueous solution containing butyric acid. Fermentation broth.

According to the method of the present invention, in step a), an extraction solvent containing a water-insoluble trialkylamine is mixed with the aqueous fermentation broth containing butyric acid for liquid/liquid extraction to obtain an aqueous phase and a trialkyl group-containing solvent. The non-aqueous phase of ammonium butyrate. Step a) can be carried out at any temperature as long as it can maintain a two-phase state (non-aqueous phase/aqueous phase).

The extraction solvent of step a) may be a water-insoluble trialkylamine itself or a mixture comprising the water-insoluble trialkylamine. Preferably, the water-insoluble trialkylamine has the formula NR ₁ R ₂ R ₃ wherein R ₁ , R ₂ and R ₃ are the same or different and each independently is a C 5 -C 10 alkyl group. More preferably, in the step a) of the present invention, the water-insoluble trialkylamine of the formula NR ₁ R ₂ R ₃ wherein the R ₁ , R ₂ and R ₃ are the same alkyl group, for example, selected from the group consisting of The following group of water insoluble trialkylamines: triamylamine, trihexylamine, trioctylamine, tridecylamine, and combinations of the foregoing.

Optionally, the extraction solvent of step a) may comprise a diluent to increase the fluidity of the extraction solvent and improve the extraction efficiency. Any suitable diluent may be employed as long as it is miscible with the trialkylamine and does not undergo a vigorous chemical reaction with the trialkylamine or butyric acid in the subsequent heating step. Examples of suitable diluents include, but are not limited to, for example, acetophenone, kerosene, n-butanol, and the like.

According to the method of the present invention, the liquid/liquid extraction in step a) is carried out to react butyric acid in the aqueous fermentation broth with a trialkylamine to produce a water-insoluble trialkylammonium butyrate to obtain a trialkylammonium butyrate. The non-aqueous phase of salt. Thereafter, the non-aqueous phase is heated in step b) to decompose the trialkylammonium butyrate therein to obtain butyric acid and a trialkylamine.

Any of the heating methods conventional in the art can be used to carry out step b) of the process of the invention. For example, evaporation can be carried out using an evaporator or distillation using a distillation column to carry out step b), but not limited thereto. Depending on the type of water-insoluble trialkylamine used in step a), step b) is carried out at a suitable temperature. For example, when a water-insoluble trialkylamine is used as an extraction solvent, triammonium butyrate is obtained, and since the triammonium butyrate starts to decompose at 90 to 100 ° C, it can be 90 to 100. Step b) is carried out at a temperature of ° C or higher to obtain butyric acid and triamylamine. Wherein, when step b) is carried out by distillation, butyric acid can be directly isolated from the top of the column, and triamylamine can be obtained at the bottom of the column, the butyric acid can enter step c), and the triamylamine can be recovered and returned to the step. a) Use.

According to the process of the invention, the butyric acid obtained in step b) is esterified with methanol in step c) to give methyl butyrate. The esterification reaction can be carried out in the presence of an esterification catalyst at a temperature of, for example, 80 to 300 ° C and a pressure of 1 to 20 atm. and 1 to 10 mol of methanol per mole of the methane. In general, if the reaction temperature is lower than 80 ° C, the catalytic activity is low, and the conversion rate is lowered; conversely, if the reaction temperature is higher than 300 ° C, a larger amount of by-products may be formed to lower the selectivity.

Preferably, step c) is carried out at a lower pressure, which has the advantage that a lower pressure facilitates partial evaporation of the feed, thereby effecting an esterification reaction in a gas-liquid coexisting state to increase thermodynamic equilibrium conversion (thermodynamic equilibrium conversion). ). Further, it has been found that if the amount of methanol and butyric acid is close to the stoichiometric ratio (1:1), the conversion rate is lowered to 70 to 80%, and therefore, it is preferred to use excess methanol in step c) to increase the conversion of butyric acid. In general, a conversion of 95% or more can be obtained with 2 moles or more of methanol per mole of acid; however, if the molar ratio of methanol to butyric acid is too high, it may increase. The formation of by-products, thereby reducing selectivity.

A homogeneous or heterogeneous esterification catalyst can be employed in step c). Examples of homogeneous catalysts include, but are not limited to, for example, sulfuric acid, hydrochloric acid or nitric acid; examples of heterogeneous catalysts include, but are not limited to, for example, ion exchange resins, zeolites, siallite, alumina, sulfonated carbon (sulfonated carbon), heteropoly acid (heteropoly acid).

In one embodiment of the present invention, in the presence of an esterification catalyst, at a temperature of from 60 to 140 ° C and a pressure of from 1 to 4 atm, in the range of from 1 to 7 mol of methanol per mole of butyric acid. The esterification reaction of step c) is carried out, The catalyst used may be selected from the group consisting of ion exchange resins, zeolites, alumina, alumina, sulfonated carbons, heteropolyacids, and combinations of the foregoing.

According to the process of the present invention, the methyl butyrate obtained in the step c) is subjected to a hydrogenolysis reaction in the step d) to obtain butanol and methanol. The hydrogenolysis reaction can be carried out in the presence of a hydrogenolysis catalyst. In general, as the reaction temperature increases, the conversion rate of the hydrogenolysis reaction increases correspondingly, and the product selectivity decreases accordingly; and as the reaction pressure increases, the conversion rate increases accordingly. Therefore, the reaction conditions are usually adjusted depending on the characteristics of the hydrogenolysis catalyst used, and are not limited to those disclosed herein. In one embodiment of the present invention, in the presence of a hydrogenolysis catalyst, at a temperature of from 120 to 300 ° C and a pressure of from 1 to 100 atm, and from 1 to 100 moles of hydrogen per mole of methyl mordate. The hydrogenolysis reaction of step d) is carried out.

Any suitable hydrogenolysis reaction catalyst can be used to carry out step d) of the process of the invention. For example, but not limited thereto, the hydrogenolysis catalyst may be one or more selected from the group consisting of copper, zinc, chromium, nickel, cobalt, silver, molybdenum, palladium, rhodium, ruthenium, and An oxide of the foregoing metal. The hydrogenolysis catalyst can also be used in the form of a supported support. For example, in one embodiment of the present invention, a copper catalyst (i.e., Cu/SiO ₂ ) supported on cerium oxide is used as a hydrogenolysis reaction catalyst.

Methyl butyrate can be decomposed by the hydrogenolysis reaction of step d) to obtain butanol and methanol, wherein butanol can be used as a fuel, and methanol can be recovered for use in step c).

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is incorporated to illustrate one embodiment of the method of the present invention. As shown in Fig. 1, the aqueous carbohydrate solution 1 is supplied to the fermentation reactor 100 to be fermented to produce an aqueous fermentation liquid 2. Thereafter, the pH may be adjusted to a suitable range in the pH adjusting tank 200 before the extraction is performed according to the demand, and water is obtained. Fermentation liquid 4. Next, the aqueous fermentation broth 4 is supplied to the extractor 300 and extracted with an extraction solvent 5 (for example, trioctylamine) containing a water-insoluble trialkylamine to obtain a non-aqueous phase containing a trialkylammonium butyrate. Extract 6, and raffinate 7. The extract 6 is supplied to a heater 400 to be decomposed to obtain butyric acid 8 and a trialkylamine 5, wherein the trialkylamine 5 is recovered and sent to the extractor 300. Thereafter, butyric acid 8 is sent to the esterification reactor 500 to carry out an esterification reaction with methanol 9, to obtain methyl butyrate 10. Methyl butyrate 10 is then sent to a hydrogenolysis reactor 600 (hydrogen 11 is supplied), and subjected to a hydrogenolysis reaction to obtain a mixed liquid 12 of butanol and methanol. The mixture 12 of butanol and methanol is further supplied to the distillation column 700, and separated into products butanol 13 and methanol 9, wherein the methanol 9 is recovered and sent to the esterification reactor 500.

As described above, the method of the present invention firstly combines an extraction solvent containing a water-insoluble trialkylamine with the aqueous fermentation broth containing butyric acid for liquid/liquid extraction, and heats the obtained non-aqueous phase to decompose three of them. Alkyl ammonium butyrate to obtain butyric acid and trialkylamine, and then the obtained butyric acid is esterified with methanol, and the obtained methyl butyrate is subsequently subjected to hydrogenolysis reaction, thereby preparing from the fermentation liquid. Butanol. Since the butyric acid contained in the fermentation liquid can be extracted in a high yield with an extraction solvent containing a water-insoluble trialkylamine, the subsequent esterification reaction of butyric acid with methanol and hydrogenolysis of methyl butyrate can also be carried out in a high yield. The invention can achieve the purpose of preparing butanol from the fermentation liquid with high efficiency. In addition, the materials used in the method of the present invention, including water-insoluble trialkylamine and methanol, can be separated in subsequent operations, and further recycled and reused, which is more economical. Further, if desired, the butyric acid and methyl butyrate obtained in the method of the present invention can be utilized as a product, and the elasticity is more applied.

[Examples]

The invention is further illustrated by the following specific embodiments in which the analytical methods used are as follows.

Optical Density: The optical density of the cell suspension at a wavelength of 600 nm (OD600) was measured with a spectrophotometer (OPTIZEN, model 2120 UV plus) to analyze the free cell density.

Concentration of sugars and organic acids in the reaction solution: high performance liquid chromatography with Aminex HPX-87H column (300 x 7.8 mm), 75 °C column oven and refractive index detector (HPLC) (Agilent HP-1100) analysis of solutions containing organic acids and sugars. The mobile phase was 18 mM sulfuric acid at a flow rate of 6 ml/min. Determine the concentration of sugars and organic acids based on the standard calibration curve.

Gas composition: Gas was analyzed by gas chromatography (GC) (YL6100 GC) equipped with a ShinCarbon ST 100/120 mesh column (2 m x 1 mm ID micropacked). The temperature of the syringe and detector were set to 100 ° C and 200 ° C, respectively. The carrier gas was helium and the flow rate was 10 ml/min. The residence time is compared to the standard residence time to define the carbon dioxide peak.

Preparation example: Preparation of aqueous fermentation broth containing butyric acid

[Microbial culture]

In the present preparation, the microorganism Clostridium tyrobutylicum (ATCC 25755 ) used was purchased from the Bioresource Collection and Research Center (BCRC). Before use, the stock culture was anaerobic precultured with a serum bottle containing 100 ml of Reinforced Clostridial Medium (RCM; purchased from Merck) with stirring at 37 °C. ) lasted for 48 hours.

Prepare a basal medium containing the following ingredients per liter of deionized water: 5 grams of yeast extract, 5 grams of peptone, 3 grams of ammonium sulfate, 1.5 grams of potassium dihydrogen phosphate, 0.6 g of aqueous magnesium sulfate (MgSO ₄ ‧7H ₂ O) and 0.03 g of aqueous ferric sulphate (FeSO ₄ ‧7H ₂ O) (see Wu et al., Biotechnology and Bioengineering 2003, 82(1), 93-102). Thereafter, glucose and/or lactic acid as a carbon source is added to the basal medium to prepare a feedstock, wherein when the raw material is used for the cell culture in a volume-increasing manner for "cell fixation", the glucose concentration of the configured raw material is 10 g/ Liters; when the raw materials are used in the "batch fermentation reaction" to produce organic compounds, the raw materials have a glucose concentration of 15 g/liter and a lactic acid concentration of 15 g/l. The material was autoclaved for 30 minutes at 121 ° C, 15 psig (pounds per square foot gauge).

[cell fixation]

About 300 ml of the microbial suspension prepared in the serum bottle was inoculated into a 5 liter fermentation tank which was filled with 4 liters of a raw material containing a carbon source of glucose (10 g/liter). Thereafter, the microorganisms were allowed to grow for 7 days until the concentration of the microbial cells reached an optical density (OD600) of 5.

The cells were immobilized on phosphorylated polyvinyl alcohol gel particles according to the method disclosed by Chen, K. (see "Immobilization of microorganism with phosphorylated polyvinyl alcohol (PVA) gel," Enzyme Microbiob. Technol. 1994, 16, 679-83. The full text is hereby incorporated by reference. The above microbial suspension was centrifuged at 6,500 rpm (revolutions per minute) for 10 minutes in a centrifuge (KUBOTA, model 7780) to collect the cells, and then the collected cells were added to the PVA. In the aqueous solution, a suspension mixture having a suspension ratio of about 9% w/v (weight/volume) is obtained, that is, 20 g of wet cells per liter of the PVA solution; thereafter, the polyvinyl alcohol-cell mixture is dropped to saturated boric acid and phosphoric acid. The sodium solution was gently stirred for 1 to 2 hours to form microparticle-fixed particles having a diameter of 3 to 4 mm; thereafter, the formed particles were washed with water.

[Batch fermentation reaction]

Batch fermentation was carried out in a 2 liter stirred fermentation tank. Wherein, after the fermentation tank is filled with a raw material solution containing carbon source of glucose (15 g/L) and L-lactic acid (15 g/L), nitrogen is aerated to reach an anaerobic state, and pH is adjusted with 2N sodium hydroxide. Value to 6.0. Thereafter, 70 g of the above-prepared polyvinyl alcohol granules immobilized with Clostridium tyrosii prepared in an inoculum size of about 5% w/v were inoculated, and fermentation was carried out at 37 ° C at a stirring speed of 600 rpm. The pH was maintained at approximately 6 ± 0.1 by the addition of 2N sodium hydroxide solution. The fermentation reaction is continued until butyric acid is stopped due to product inhibition. The liquid and gas components in the fermentation tank were analyzed to confirm that the final butyric acid concentration was 17.2 g/liter, the butyric acid carbon yield was 83%, and no carbon loss occurred due to carbon dioxide generation.

Example 1: Extraction of butyric acid from fermentation broth

[Extraction with trioctylamine]

A fermentation broth of 18,941 grams was provided having a pH of 6.6 and containing 2.4% by weight of butyric acid. After adjusting the pH of the fermentation broth to about 2.43 with sulfuric acid, as shown in Fig. 2, the fermentation broth is divided into five batches, and the weight is 4,000, 3, 675, 4,000, 3,500, 3,766 g, and each batch of fermentation broth is Trioctylamine was subjected to secondary cross-flow extraction. In the first stage, 500 grams of trioctylamine is mixed with the fermentation broth and extracted while The pH of the aqueous phase was maintained at about 1.28 with sulfuric acid. In the second stage, 487 g of trioctylamine was mixed with the first stage raffinate (i.e., the aqueous phase) and extracted, and the pH of the aqueous phase was maintained at about 2.58 with sulfuric acid. The extracts of each stage (ie, the non-aqueous phase) are mixed with the next batch of fermentation broth, and the second-stage cross-flow extraction is also performed. After extracting the five batches of the fermentation broth, 719 g of the first-stage extract and 678 g of the second-stage extract were obtained, and the composition contained trioctyl ammonium butyrate.

The extraction efficiency of the above extraction operation was confirmed in the following manner (see Shu Liangcheng et al., "Study on the conditions of separation and extraction of butyric acid in fermentation broth", Chemical Engineering, Vol. 39, No. 8, August 2011, the full text of this document For reference here). The obtained first-stage extract is reacted with sodium hydroxide in the second-stage extract to form sodium butyrate, and the concentration of sodium butyrate is analyzed by high performance liquid chromatography (HPLC). It was found that the sodium butyrate concentration was 19% by weight.

[heating the extract to obtain butyric acid]

1,397 g of the foregoing extract was placed in a flask, heated to boiling under a pressure of 30 mmHg, and the vaporized gas was condensed through a condenser above the flask to obtain 313 g of a liquid having a butyric acid concentration of 76.8. weight%. Further, distillation was carried out in a batch rectification column at a pressure of 30 mmHg, and 133 g of a distillate liquid was collected, wherein the concentration of butyric acid was 97.5% by weight and the concentration of propionic acid was 2.4% by weight.

The above results show that the method of the present invention can be easily mixed in the form of trialkylamine butyrate by the step a) by mixing the extraction solvent of the aqueous insoluble trialkylamine with the aqueous fermentation broth containing butyric acid and performing liquid/liquid extraction. Butyric acid is separated from the fermentation broth in high yield; and the heating operation of step b) can decompose step a) non-aqueous phase (ie the aforementioned A trialkylammonium butyrate in the extract) to obtain a high purity butyric acid solution.

Examples 2 to 4: Esterification reaction

Example 2: High purity butyric acid (purchased from Alfa Aesar, purity 99+%, CAS No.: 107-92-6), and methanol with Amberlyst 35 wet ion exchange resin as an acidic catalyst (purchased from Rohm & Haas Company) was placed in a 250 ml three-necked flask equipped with a reflux condenser and stirred, wherein the molar ratio of butyric acid to methanol was 1:2, and the concentration of the acidic catalyst was 20 g/liter. The molar yield of methyl butyrate obtained was 64.9% after heating and maintaining the reactants at 80 ° C for the esterification reaction for 2 hours.

Example 3: The operation of Example 2 was repeated except that the molar ratio of butyric acid to methanol was 1:3, the concentration of the acidic catalyst was 100 g/L, and the reaction was carried out for 75 minutes to obtain butyric acid. The molar yield of the methyl ester was 89.8%.

Example 4: The operation of Example 2 was repeated except that the molar ratio of butyric acid to methanol was 1:4, the concentration of the acidic catalyst was 200 g/L, and the reaction was carried out for 75 minutes to obtain butyric acid. The molar yield of the methyl ester was 99.9%.

As shown in the above Examples 2 to 4, the step c) of the method of the present invention esterifies the butyric acid obtained in the step b) with methanol to obtain methyl butyrate, wherein the reaction conditions and the butyric acid are adjusted by The molar ratio of methanol can be as high as 99.9%. In addition, since the process of the present invention is carried out by esterification with methanol, in the case of using excess methanol to increase the conversion, the remaining methanol of the reaction is apparent because of its boiling point (64.7 ° C) and the boiling point of the product methyl butyrate (102 ° C). Different and easy to separate and recycle.

Example 5: Hydrogenolysis reaction - I

Strem's copper-chromium catalyst was placed in a packed bed reactor (length 55 cm, inner diameter 1.32 cm, outer diameter 1.8 cm), respectively, as shown in Table 1 The hydrogen gas was supplied at a rate of 1,100 ml/min to carry out hydrogenolysis of methyl butyrate, and the results are shown in Table 1.

Example 6: Hydrogenolysis reaction-II

[Preparation of Cu/SiO ₂ catalyst]

30 g of copper nitrate trihydrate and 200 ml of deionized water were added to the beaker and stirred, after which the mixed solution was titrated to a pH of 8 to 9 with an aqueous solution of sodium hydroxide to form a slurry solution. After adding 44 ml (containing 28% of SiO ₂ ) tetraethyl citrate solution to the slurry solution and stirring and mixing, it was placed in a batch reactor and heated to 80 ° C to react for aging for 4 hours. Thereafter, the product was suction-filtered and placed in an oven at a temperature of 120 ° C for 16 hours to prepare a Cu/SiO ₂ catalyst. After the obtained catalyst product was pressed into an ingot and dried, air calcination was carried out at 400 ° C for 4 hours, and then a reduction reaction was carried out at 240 ° C for 4 hours at a hydrogen flow rate of 1500 ml/min.

[hydrogenation reaction]

The same experimental apparatus as in Example 5 was used, but 20 g of the catalyst prepared in the present example was packed in a reaction tube, and hydrogenolysis of methyl butyrate was carried out by using methyl butyrate flow rate and hydrogen flow rate shown in Table 2, respectively. The results of the reaction are shown in Table 2.

As shown in Examples 5 and 6, the step d) of the method of the present invention hydrogenates the methyl butyrate of the step c) to obtain butanol and methanol, which can be obtained without using extreme conditions under appropriate reaction conditions. The conversion of methyl butyrate to butanol yield is close to 100% with almost no reaction loss.

Comparative example 1

The operation of Example 5 was repeated except that ethyl butyrate was used as the reactant, the hydrogen flow rate was 1,100 ml/min, the amount of the catalyst was 60 g, and the reaction conditions as shown in Table 3 were employed. The results are also shown in Table 3.

Comparative example 2

The procedure of Example 5 was repeated except that butyl butyrate was used as the reactant, the hydrogen flow rate was 1,100 ml/min, and the reaction conditions as shown in Table 4 were employed, and the results are also shown in Table 4.

Comparative example 3

The operation of Example 5 was repeated except that methyl butyrate, ethyl butyrate, and butyl butyrate were used as reactants, and the hydrogen flow rate was 1,100 ml/min, and the hourly space velocity (WHSV) was 0.1. /hour. The highest butanol yields obtained for the different reactants were compared as shown in Table 5.

As shown in the above Example 5 and Comparative Examples 1 to 3, the method of the present invention uses the same method as the highest butanol yield which can be obtained by hydrogenolysis with ethyl butyrate or butyl butyrate as a reactant. Methyl ester can achieve higher butanol yields. Further, the results of Comparative Example 3 were compared with the results of Example 5 (Table 1), and it was found that under the same reaction conditions (60 g of catalyst, 200 ° C reaction temperature, reaction pressure of 400 or 500 psi, butyrate flow rate) 6 g/hr), the method of the invention does achieve a higher butanol yield using methyl butyrate. In addition, the present invention uses methyl butyrate for hydrogenolysis reaction, and the obtained product is butanol and methanol, which can be easily distinguished by its boiling point. Separation is carried out with differences.

The above embodiments are merely illustrative of the principles and effects of the present invention, and are illustrative of the technical features of the present invention and are not intended to limit the scope of the present invention. Any changes or arrangements that can be easily accomplished by those skilled in the art without departing from the technical principles and spirit of the invention are within the scope of the invention. Accordingly, the scope of the invention is set forth in the appended claims.

1‧‧‧Aqueous carbohydrate solution

2, 4‧‧‧ Aqueous fermentation broth

3‧‧‧Inorganic acid

5‧‧‧ extraction solvent

6‧‧‧ extract

7‧‧‧The remnant

8‧‧‧butyric acid

9‧‧‧Methanol

10‧‧‧ Methyl butyrate

11‧‧‧ Hydrogen

12‧‧‧ Mixture of butanol and methanol

13‧‧‧butanol

100‧‧‧ Fermentation reactor

200‧‧‧pH adjustment slot

300‧‧‧ extractor

400‧‧‧heater

500‧‧‧esterification reactor

600‧‧‧hydrogenation reactor

700‧‧‧Distillation tower

Claims (13)

A method for preparing butanol from an aqueous fermentation broth containing butyric acid, wherein the aqueous fermentation broth containing butyric acid is obtained by performing a fermentation reaction using a microorganism in a carbohydrate, the method comprising the steps of: a) An extraction solvent containing a water-insoluble trialkylamine is mixed with the aqueous fermentation broth containing butyric acid for liquid/liquid extraction to obtain an aqueous phase and a non-aqueous solution containing trialkylammonium butyrate. a non-aqueous phase, wherein the water-insoluble trialkylamine has the formula NR ₁ R ₂ R ₃ , R ₁ , R ₂ , R ₃ are the same or different and are each independently a C 5 -C 10 alkyl group; Heating the non-aqueous phase of step a) to decompose the trialkylammonium butyrate thereof to obtain butyric acid and a trialkylamine; c) esterifying the butyric acid obtained by separating from step b) with methanol, Methyl butyrate is obtained; and d) the methyl butyrate obtained in step c) is subjected to a hydrogenolysis reaction to obtain butanol and methanol. The method of claim 1, wherein the microorganism is selected from the group consisting of Clostridium tyrobutylicum, Clostridium butylicum, Clostridium acetobutyricum, Clostridium beijerinckii (Clostridium beijerinckii), and combinations of the foregoing. The method of claim 1, wherein R ₁ , R ₂ , and R ₃ are the same alkyl group. The method of claim 1, wherein the water-insoluble trialkylamine is selected from the group consisting of triamylamine, trihexylamine, trioctylamine, tridecylamine, and combinations thereof. The method of claim 1, wherein step c) is present in an esterification catalyst It is carried out under the conditions of a temperature of 60 to 140 ° C and a pressure of 1 to 4 atm, and 1 to 7 mol of methanol per mole of butyric acid. The method of claim 5, wherein the esterification catalyst is a solid acid catalyst having super acid properties selected from the group consisting of ion exchange resins, zeolites, siallite, alumina, sulfonated carbon. (sulfonated carbon), heteropoly acid, and combinations of the foregoing. The method of claim 1, wherein the step d) is in the presence of a hydrogenolysis catalyst at a temperature of from 120 to 300 ° C and a pressure of from 1 to 100 atm, and from 1 to 100 mol of hydrogen per mole of methyl mordate. Under the conditions. The method of claim 7, wherein the hydrogenolysis catalyst is selected from the group consisting of copper, zinc, chromium, nickel, cobalt, silver, molybdenum, palladium, rhodium, iridium, oxides of the foregoing metals, and combinations thereof . The method of claim 8, wherein the hydrogenolysis reaction catalyst is supported on a carrier. The method of claim 9, wherein the hydrogenolysis reaction catalyst is Cu/SiO ₂ . The method of any one of claims 1 to 10, further comprising supplying the trialkylamine obtained in step b) to step a). The method of any one of claims 1 to 10, further comprising supplying the methanol obtained in step d) to step c). The method of claim 11, further comprising supplying the methanol obtained in step d) to step c).