阅读说明：本技术 一种循环制备乙酰丙酸和糠醛的方法 (Method for circularly preparing levulinic acid and furfural ) 是由 陈新德 陈雪芳 熊莲 黄超 张海荣 于 2019-09-16 设计创作，主要内容包括：本发明公开了一种循环制备乙酰丙酸和糠醛的方法,一锅法稀酸水解、超高交联吸附树脂吸附/脱附制备乙酰丙酸和糠醛,工艺简单、绿色环保,实现秸秆等木质纤维素直接水解制备乙酰丙酸和糠醛过程中稀酸废水的“零排放”,解决了现有技术秸秆等木质纤维素直接水解制备乙酰丙酸和糠醛过程中酸废水排放量大、产物分离提纯困难的问题。(The invention discloses a method for circularly preparing levulinic acid and furfural, which is characterized in that levulinic acid and furfural are prepared by one-pot dilute acid hydrolysis and adsorption/desorption of ultrahigh crosslinked adsorption resin, the process is simple, green and environment-friendly, zero emission of dilute acid wastewater in the process of directly hydrolyzing lignocellulose such as straw to prepare the levulinic acid and the furfural is realized, and the problems of large discharge amount of acid wastewater and difficult product separation and purification in the process of directly hydrolyzing the lignocellulose such as straw to prepare the levulinic acid and the furfural in the prior art are solved.)

1. A method for circularly preparing levulinic acid and furfural is characterized by comprising the following steps:

(1) crushing a lignocellulose raw material, mixing the crushed lignocellulose raw material with a dilute acid solution, and reacting for 30-300 min at 140-210 ℃; carrying out suction filtration on the slurry, and washing the obtained solid residue for multiple times to obtain lignin; the obtained filtrate is hydrolysate; wherein the concentration of the dilute acid solution is 0.1-5 wt%, and the mass ratio of the lignocellulose raw material to the dilute acid solution is 1: 4-1: 20;

(2) adding ultrahigh cross-linked adsorbent resin into the hydrolysate obtained in the step (1) according to the addition amount of 0.5-20 wt% of the mass of the hydrolysate, then placing the hydrolysate in a constant-temperature shaking table at the temperature of 15-40 ℃ for oscillation for 0.5-5 h, filtering, collecting the adsorbed ultrahigh cross-linked adsorbent resin, and recovering waste liquid as dilute acid solution for hydrolysis in the step (1);

(3) eluting the adsorbed ultrahigh cross-linked adsorbent resin obtained in the step (2) by using 10-50 times of low-carbon alcohol solution, wherein the desorption temperature is 25-45 ℃, and the time is 10-50 min, and filtering to obtain regenerated ultrahigh cross-linked adsorbent resin and low-carbon alcohol eluent; the low-carbon alcohol solution eluent is subjected to reduced pressure distillation to separate levulinic acid and furfural, and then is recycled;

(4) and (3) recycling the filtrate obtained in the step (2) as 100 parts of waste liquid rich in organic carboxylic acid obtained by circulating the dilute acid solution for hydrolysis in the step (1) for 2-20 times, adding the waste liquid into 5-50 parts by mass of alcoholic solution, performing esterification reaction at 80-200 ℃ for 30-150 min, recovering the ester compound from the obtained product by reduced pressure distillation, and further applying the residual waste water to the step (1).

2. The method for cyclically preparing levulinic acid and furfural according to claim 1, wherein the lignocellulosic raw materials comprise more than one of bagasse, wheat straw, corn cobs, corn stover, rice straw and cotton stalks.

3. The method for cyclically preparing levulinic acid and furfural according to claim 1, wherein the ultrahigh cross-linked adsorption resin is more than one of polystyrene, polyacrylate and polyacrylamide, and the specific surface area of the ultrahigh cross-linked adsorption resin is 200-1000 m²/m³The average particle size is 0.25-0.80 mm, the water content is 30-80%, and the average pore diameter is 2-20 nm.

4. The method for cyclically preparing levulinic acid and furfural according to claim 1, wherein the acid solution is a mixture of more than one of hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid and water.

5. The method for cyclically preparing the levulinic acid and the furfural according to claim 1, wherein the low carbon alcohol solution is one or more of methanol, ethanol, propanol and glycol, or a mixture of one or more of methanol, ethanol, propanol and glycol and water, and the low carbon alcohol concentration is 40-75 wt%.

The technical field is as follows:

the invention relates to a method for circularly preparing levulinic acid and furfural.

Background art:

lignocellulose is the most abundant biomass resource on earth, and is mainly composed of cellulose, hemicellulose and lignin. The cellulose is a linear chain polysaccharide compound formed by connecting glucose monomers, the depolymerized glucose can be used for preparing 5-hydroxymethylfurfural, and the 5-hydroxymethylfurfural can be further dehydrated to prepare the high value-added platform compound levulinic acid. Levulinic acid also becomes fructonic acid and levo-gluconic acid, and a polyfunctional compound containing carbonyl, a-hydrogen and carboxyl is an important platform compound and can be used in various industries such as plastic modifiers, medicines, industrial chemicals, spices, solvents, pesticide intermediates, lubricating oil additives and the like. The hemicellulose is a branched chain heteropolysaccharide compound mainly formed by connecting xylose, glucose, galactose and the like, and the depolymerized xylose can be used for preparing furfural. Furfural is active in chemical property, is an important organic chemical product, can prepare a variety of derivatives through reactions such as oxidation, condensation and the like, and is widely applied to industries of synthetic plastics, medicines, pesticides and the like.

China is a traditional big agricultural country, and about 9 hundred million tons of straw wastes are generated every year. Therefore, the straw is used for preparing important platform compounds of levulinic acid and furfural by a chemical conversion method, and the application prospect is wide. However, during the hydrolysis of straw to produce levulinic acid and furfural, a range of other compounds such as formic acid, acetic acid and 5-hydroxymethylfurfural, acid-soluble lignin, etc. are formed. To obtain levulinic acid and furfural with higher purity, the degradation product mixture must be separated and purified. The Chinese invention patent CN107175136A discloses a weak base anion exchange resin and a method for purifying levulinic acid by using the same, when the weak base anion exchange resin provided by the patent is used for purifying dilute hydrolysate of the levulinic acid, negative pressure distillation is not needed, the dilute hydrolysate can be regenerated, and the method has the advantages of high exchange capacity, high exchange speed and the like. However, we also see from the patent that the weak base anion exchange resin needs to be washed alternately by hydrochloric acid and sodium hydroxide solution in the regeneration process, so a large amount of acid-base waste liquid is generated in the process, and the environmental burden is caused. Aiming at the defects of large discharge amount of acid wastewater, difficult separation and purification of products and the like in the process of preparing levulinic acid and furfural by directly hydrolyzing straws, an environment-friendly method for preparing the levulinic acid and the furfural is urgently required to be explored.

The invention content is as follows:

the invention aims to provide a method for circularly preparing levulinic acid and furfural, which has simple process and environmental protection, realizes zero discharge of dilute acid wastewater in the process of preparing the levulinic acid and the furfural by directly hydrolyzing lignocellulose such as straw and the like, and solves the problems of large discharge amount of the acid wastewater and difficult product separation and purification in the process of preparing the levulinic acid and the furfural by directly hydrolyzing the lignocellulose such as straw and the like in the prior art.

The invention is realized by the following technical scheme:

a method for circularly preparing levulinic acid and furfural, which comprises the following steps:

(1) crushing a lignocellulose raw material, mixing the crushed lignocellulose raw material with a dilute acid solution, and reacting for 30-300 min at 140-210 ℃; carrying out suction filtration on the slurry to obtain solid residues, and washing the solid residues for multiple times to obtain lignin; the obtained filtrate is hydrolysate; wherein the concentration of the dilute acid solution is 0.1-5 wt%, and the mass ratio of the lignocellulose raw material to the dilute acid solution is 1: 4-1: 20;

(2) adding ultrahigh cross-linked adsorbent resin into the hydrolysate obtained in the step (1) according to the addition amount of 0.5-20 wt% of the mass of the hydrolysate, then placing the hydrolysate in a constant-temperature shaking table at the temperature of 15-40 ℃ for oscillation for 0.5-5 h, filtering, collecting the adsorbed ultrahigh cross-linked adsorbent resin, and recovering waste liquid as dilute acid solution for hydrolysis in the step (1);

(3) eluting the adsorbed ultrahigh cross-linked adsorbent resin obtained in the step (2) by using 10-50 times of low-carbon alcohol solution, wherein the desorption temperature is 25-45 ℃, and the time is 10-50 min, and filtering to obtain regenerated ultrahigh cross-linked adsorbent resin and low-carbon alcohol eluent; the low-carbon alcohol solution eluent is subjected to reduced pressure distillation to separate levulinic acid and furfural, and then is recycled;

(4) and (3) recycling the filtrate obtained in the step (2) as 100 parts of waste liquid rich in organic carboxylic acid obtained by circulating the dilute acid solution for hydrolysis in the step (1) for 2-20 times, adding the waste liquid into 5-50 parts by mass of alcoholic solution, performing esterification reaction at 80-200 ℃ for 30-150 min, recovering the ester compound from the obtained product by reduced pressure distillation, and further applying the residual waste water to the step (1).

The lignocellulose raw material comprises more than one of bagasse, wheat straw, corn cob, corn straw, rice straw and cotton stalk.

The ultrahigh cross-linked adsorption resin is more than one of polystyrene, polyacrylate and polyacrylamide, and has a specific surface area of 200-1000 m²/m³The average particle size is 0.25-0.80 mm, the water content is 30-80%, and the average pore diameter is 2-20 nm.

The acid solution is a mixture of more than one of hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid and water.

The low-carbon alcohol solution is one or more of methanol, ethanol, propanol and glycol, or a mixture of one or more of methanol, ethanol, propanol and glycol and water, and the concentration of the low-carbon alcohol is 40-75 wt%.

Compared with the prior art, the invention has the following advantages:

(1) the ultrahigh cross-linked adsorption resin with controllable structure and performance is used for separating and purifying the levulinic acid and the furfural in the hydrolysate, has the advantages of high adsorption capacity, quickness and the like, simultaneously uses low-carbon alcohol (methanol, ethanol and the like) as a regeneration solvent, is green and environment-friendly, can be repeatedly used, has simple, convenient and feasible separation process, high efficiency, quickness, low equipment investment and operation cost, low wastewater discharge and avoids the problem of environmental pollution, and is a high-efficiency clean separation process.

(2) A green circulating hydrolysis route for preparing the levulinic acid and the furfural by straw one-pot dilute acid hydrolysis and ultrahigh cross-linked adsorption resin adsorption/desorption is established, aiming at the fact that straw hydrolysate after the levulinic acid and the furfural are separated still contains organic carboxylic acid substances such as formic acid and acetic acid and inorganic acid substances used in hydrolysis, a circulating hydrolysis method is adopted, the amount of acid needed in the straw hydrolysis process is reduced, and zero emission of acid wastewater generated in the process of preparing the levulinic acid and the furfural by directly hydrolyzing the straws in one pot is realized.

The specific implementation mode is as follows:

the following is a further description of the invention and is not intended to be limiting.