CN102392082A - Method for preparing glucose by catalyzing hydrolysis of cellulose by low-solubility organic acid - Google Patents

Abstract

The invention discloses a method for preparing glucose by catalyzing cellulose hydrolysis with low solubility organic acid. The main steps of the method are as follows: put 0.5wt%~10wt% crushed cellulose raw material, 0.5wt%~5wt% organic acid and water in a reaction kettle to obtain a mixed solution, and put the mixed solution at 150°C~200 Under the condition of ℃, it can be hydrolyzed for 0~3h. After the reaction is cooled to room temperature, the hydrolyzate is filtered and separated. The filtered filtrate is the sugar solution. The filter residue contains unhydrolyzed cellulose raw materials and residual organic acids. The residue can be hydrolyzed again after adding water. After repeated hydrolysis, adding fresh cellulose raw material or organic acid can realize rehydrolysis. The invention combines the advantages of few hydrolysis by-products of water-soluble organic acids and easy separation of solid acid hydrolysis products, can make full use of organic acids and cellulose raw materials for continuous hydrolysis to prepare glucose, and is suitable for industrial continuous production and application.

Description

A kind of low-solubility organic acid catalyzes the method of cellulose hydrolysis to prepare glucose

technical field

The invention belongs to the field of biomass conversion, and in particular relates to a method for preparing glucose by catalyzing cellulose hydrolysis with low solubility organic acid. the

Background technique

The production of bioethanol is one of the main methods of biomass resource conversion and utilization, and the key step is how to hydrolyze the cellulose or hemicellulose in the fiber raw material into fermentable sugars. Compared with cellulase hydrolysis, the acid-catalyzed hydrolysis process has the advantages of low cost and easy control of reaction conditions, but the acid-catalyzed hydrolysis process also has disadvantages including high equipment requirements, difficult wastewater treatment, complex hydrolyzate and difficult purification. .In order to solve the problem of complex products in the process of acid hydrolysis, some researchers proposed to use organic acids such as formic acid or maleic acid to hydrolyze cellulose. Since organic acids are weaker than inorganic acids such as sulfuric acid or hydrochloric acid, the hydrolysis reaction has high selectivity. It effectively reduces the production of by-products such as 5-hydroxymethylfurfural, and the sugar solution obtained by hydrolysis is more suitable for the production of ethanol by subsequent fermentation; The use of solid acids such as sulfonated carbons to catalyze the hydrolysis of cellulose was proposed. On the one hand, the separation of the solid acid catalyst and glucose is simple; on the other hand, this type of solid acid can be used again for hydrolysis reaction after certain treatment, which effectively reduces the cost of the catalyst. However, the use of organic acids such as formic acid to catalyze the hydrolysis method makes it difficult to separate the main product glucose and organic acid, and the use of solid acid to hydrolyze cellulose has disadvantages such as long hydrolysis time and low reaction efficiency, which limits the practical application of the above two acids . the

Contents of the invention

The object of the present invention is to overcome the above-mentioned deficiencies in the prior art, and provide a method for preparing glucose by hydrolyzing cellulose with organic acid catalysis. The benzoic acid series organic acids used in the present invention have special dissolving properties, and have realized heterogeneous and homogeneous transitions at different temperatures. For example, the solubility of DNBA in water at room temperature is only 0.135g, while the solubility in boiling water is greater than 5g, and the solubility is increased by more than 30 times. Therefore, at the hydrolysis temperature, the hydrolysis reaction of this type of organic acid is a homogeneous acid-catalyzed reaction, which is similar to organic acids such as formic acid, and has the characteristics of high hydrolysis efficiency and few reaction by-products. When the reaction is finished, the system is cooled to room temperature, and most of the organic acid is precipitated from the water phase, and the product can be separated by a simple filtration method, which has the property of easy separation of solid acid. The invention combines the advantages of high-efficiency hydrolysis of liquid acid and easy separation of solid acid hydrolyzate, and is suitable for industrial continuous production. the

The object of the present invention is achieved through the following technical solutions: a method for preparing glucose by catalyzing cellulose hydrolysis with a class of low solubility organic acids, comprising the steps of:

(1) Crushing the cellulose raw material for subsequent use;

(2) placing 0.5wt%-10wt% cellulose raw material, 0.5wt%-5wt% organic acid and water in a reaction kettle to obtain a mixed solution;

(3) hydrolyzing the mixed solution obtained in step (2) at a temperature of 150°C to 200°C for 0 to 3 hours;

(4) After the hydrolyzate is cooled to room temperature, filter and separate, the filtered filtrate is glucose solution, and the filter residue is unhydrolyzed cellulose raw material and residual organic acid;

(5) After adding water to the filter residue obtained in step (4), repeat steps (3), (4) to continue hydrolysis and separation. the

After the filter residue in the step (4) is supplemented with water, continue to repeat (3), (4) after the steps 4 to 6 times, the unhydrolyzed cellulose is in a colloidal suspension in the hydrolyzate, which can be removed by dumping, and the precipitated residue is organic acids. At this time, the cellulose raw material must be supplemented. the

The cellulose raw material includes more than one of microcrystalline cellulose, sawdust, bagasse and corn stalks. the

After the filter residue in the step (4) is replenished with water, after continuing to repeat (3), (4) steps 8 to 10 times, the organic acid must be replenished. the

The organic acid includes more than one of benzoic acid, p-nitrobenzoic acid, 3,5 dinitrobenzoic acid (DNBA) and phthalic acid. the

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

(1) The acid used in the present invention is a low-solubility organic acid, with mild reaction conditions and low energy consumption; compared with inorganic acids such as sulfuric acid, the content of by-products in the hydrolyzate is low, which is beneficial to the subsequent fermentation reaction to prepare ethanol. the

(2) The present invention combines the advantages of efficient hydrolysis of liquid acid and easy separation of solid acid hydrolyzate. Compared with water-soluble organic acids such as formic acid and maleic acid, most of the organic acids are precipitated from the water during the cooling process of the reaction system, and simple filtration can realize product separation. Compared with the hydrolysis process of solid acid such as sulfonated carbon, the organic acid is a homogeneous reaction at the reaction temperature, so the efficiency of the hydrolysis reaction is greatly improved, and the hydrolysis time is shortened. the

(3) The present invention makes full use of organic acid and cellulose raw materials. The hydrolysis residue is mainly unhydrolyzed cellulose and organic acids precipitated during cooling, which can be hydrolyzed again after adding water. After repeated hydrolysis, fresh cellulose raw material or organic acid is added to realize hydrolysis again. the

Detailed ways

The present invention will be further described below in conjunction with the examples. It should be noted that the examples are not intended to limit the protection scope of the present invention. the

In this embodiment, the cellulose raw material is microcrystalline cellulose, and the organic acid catalyst is DNBA. the

Example 1

Avicel and DNBA were added to water according to the ratio shown in Table 1, and reacted at different temperatures for 2 hours. After filtration, the filtrate is used for glucose analysis and detection, and the residue is used for further hydrolysis. The details are shown in Table 1. the

Table 1 Comparison of the hydrolysis effects of DNBA on microcrystalline cellulose at different temperatures

It can be seen from Table 1 that the hydrolysis temperature has a significant effect on the glucose yield. When the temperature is lower than 190℃, the yield of glucose increases with the increase of hydrolysis temperature; when the temperature is higher than 190℃, the yield of glucose tends to decrease. It shows that at a higher temperature, the conversion of the product glucose into hydroxymethylfurfural and other by-products is enhanced, which makes the glucose yield decrease instead. the

Example 2

Avicel and DNBA were added to water according to the ratio shown in Table 2, and hydrolyzed at 190° C. for different times. After filtration, the filtrate is used for glucose analysis and detection, and the residue is used for further hydrolysis. The details are shown in Table 2. the

Comparison of the hydrolysis effect of DNBA on microcrystalline cellulose under different hydrolysis time in table 2

It should be pointed out that it takes about 40 minutes for the reaction system to heat up from room temperature to the target temperature, and the heating process is not included in the hydrolysis reaction time. Therefore, when the hydrolysis time is 0 h, the glucose yield is greater than zero. It can be seen from Table 2 that when hydrolyzed at 190°C, the glucose yield basically reached the maximum at 1 h, and the increase in the glucose yield was limited when the reaction time was prolonged, and even the glucose degraded and the final yield decreased. At the same time, for the consideration of reducing energy consumption, the hydrolysis time of 1 h is enough. the

Example 3

Add microcrystalline cellulose and DNBA to water according to the ratio shown in Table 3, and hydrolyze at 190°C for 1 hour. After filtration, the filtrate is used for glucose analysis and detection, and the residue is used for further hydrolysis. The details are shown in Table 3. the

It can be seen from Table 3 that with the increase of cellulose dosage, the glucose yield showed a downward trend, while the glucose concentration showed a rapid upward trend. The higher the concentration of glucose in the hydrolyzate, the more conducive to the operation steps such as the concentration of the subsequent fermentation process. Therefore, when the concentration of the cellulose raw material is controlled at 5-10%, both the glucose yield and the glucose concentration can be higher. the

Table 3 DNBA compares the hydrolysis effects of different concentrations of microcrystalline cellulose

Example 4

Avicel and DNBA were added to water according to the proportions shown in Table 4, and hydrolyzed at 190° C. for 1 h. After filtration, the filtrate is used for glucose analysis and detection, and the residue is used for further hydrolysis. The details are shown in Table 4. the

Table 4 Comparison of the hydrolysis effects of microcrystalline cellulose with different DNBA dosages

It can be seen from Table 4 that microcrystalline cellulose can also be hydrolyzed to produce a small amount of glucose without a catalyst, and when a small amount of organic acid is added, the glucose yield increases rapidly. But when the amount of organic acid exceeds 1wt%, the glucose yield increases limitedly, and even drops slightly. The possible reason is that when the amount of organic acid is high, the rate of side reaction also increases rapidly, so that the final glucose yield decreases instead. Therefore, when DNBA is used for cellulose hydrolysis, the dosage should be controlled within 1%. the

Example 5

Add microcrystalline cellulose and DNBA to water according to the ratio shown in Table 5, and hydrolyze at 190°C for 0.5h. After filtration, the filtrate is used for glucose analysis and detection, and the hydrolyzed residue is used for further hydrolysis after adding water. The details are shown in Table 5. the

The hydrolysis effect comparison of table 5 different hydrolysis times

a. Hydrolyzed residue After 5 times of hydrolysis, cellulose is colloidal in water, and DNBA is still a solid precipitate. Pour out the colloidal cellulose mixture, add 5g of fresh cellulose, and carry out the sixth hydrolysis. the

b Add DNBA1g to the hydrolysis residue for the ninth hydrolysis. the

Hydrolysis at 190°C for 1 hour will cause the cellulose hydrolysis residue to appear brown, indicating that the hydrolyzate has undergone a polymerization reaction to form humus. In order to realize repeated hydrolysis of cellulose residue, the hydrolysis time is controlled to 0.5h. It can be seen from Table 5 that the repeat experiment not only utilizes DNBA organic acid, the effective times can reach 6 times, but also utilizes unhydrolyzed cellulose, so that the total yield of glucose reaches 33% (glucose hydrolyzed 1 to 5 times can be obtained rate sum). the

Claims (5)

1. one type of low solubility organic acid catalysis cellulose hydrolysis prepares the method for glucose, it is characterized in that comprising the steps:

(1) cellulosic material is carried out pulverization process, subsequent use;

(2) place reaction kettle to obtain mixed solution in the cellulosic material of 0.5 wt% ~ 10 wt%, organic acid and the water of 0.5 wt% ~ 5 wt%;

(3) with gained mixed solution in the step (2) at 150 ℃ ~ 200 ℃ following hydrolysis 0 ~ 3 h;

(4) hydrolyzed solution is cooled to the room temperature after-filtration, filtrating is that Glucose Liquid, filter residue are unhydrolysed cellulosic material and residual organic acid;

(5) with after the filter residue make up water that obtains in the step (4), repeatedly repeating step (3), (4).

2. one type of low solubility organic acid catalysis cellulose hydrolysis according to claim 1 prepares the method for glucose, after the filter residue make up water that it is characterized in that obtaining in the said step (4), and behind the repeating step (3), (4) 4 ~ 6 times, the plain raw material of supplementary fibre.

3. one type of low solubility organic acid catalysis cellulose hydrolysis according to claim 1 prepares the method for glucose, after the filter residue make up water that it is characterized in that obtaining in the said step (4), behind the repeating step (3), (4) 8 ~ 10 times, replenishes organic acid.

4. one type of low solubility organic acid catalysis cellulose hydrolysis according to claim 1 prepares the method for glucose, it is characterized in that said cellulosic material comprises more than one in Microcrystalline Cellulose, sawdust, bagasse, the corn straw.

5. one type of low solubility organic acid catalysis cellulose hydrolysis according to claim 1 prepares the method for glucose; It is characterized in that said organic acid comprises more than one in phenylformic acid, p-Nitrobenzenecarboxylic acid, 3,5 dinitrobenzoic acids (DNBA) or the phthalic acid.