CN114890884B - Method for high-value utilization of corncob acid hydrolysis residues - Google Patents

Abstract

The invention belongs to the technical field of high-value utilization of industrial waste biomass resources, and relates to a method for high-value utilization of corncob acid hydrolysis residues. The process converts components in the residue into the platform chemicals levulinic acid and polyurethane foam enhancers, respectively, by utilizing them. The invention takes corncob acid hydrolysis residue as a raw material, adopts feed supplement cyclic hydrolysis to realize the preparation of levulinic acid with high solid content and high concentration, and the hydrolysis residue can be used as a polyurethane foam material reinforcing agent. The process realizes the efficient conversion of the corncob acid hydrolysis residues, and provides a new method for the high-valued utilization of biomass resources.

Description

A method for high-value utilization of corncob acid hydrolysis residue

technical field

The invention belongs to the technical field of conversion and utilization of industrial waste biomass resources, and in particular relates to a method for high-value utilization of corncob acid hydrolysis residues.

Background technique

As a by-product of corn crops, corncobs are mainly composed of 35%-40% hemicellulose, 32%-36% cellulose, 17%-20% lignin and 1.2%-1.8% ash. Corn cob is also a huge amount of biomass resources. According to statistics, my country's corn cob output will reach 88 million tons in 2020. The hemicellulose in corncob can be effectively converted into xylose, furfural and other products through acid hydrolysis, and the scale of industrial production has been formed. Corncob acid hydrolysis residue is the waste residue after producing xylose or furfural from corncob acid water. Since most of the hemicellulose has been removed, its cellulose content is relatively high, which can reach 40% to 70%. However, corncob acid hydrolysis residues (xylose residues and furfural residues) are usually burned as by-products and have not been fully utilized for high value.

The high-value utilization of corncob hydrolysis residues has always attracted much attention. For example, Yu Xiang et al. have studied the separation and purification of cellulose and lignin by two-stage treatment with alkaline H ₂ O ₂ and NaClO ₂ (Chinese Journal of Papermaking , 2016, 35(6): 38-42.), Huang Yanqin et al. studied the pyrolysis characteristics of corncob acid hydrolysis residues (Journal of Agricultural Machinery. 2012, 43(6): 86-91.) In addition, corncob hydrolysis The residue can also be used as raw material to produce alcohol (CN101413016), lactic acid (CN102286553, activated carbon (CN88101457), humic acid (CN102517338), sodium carboxymethyl cellulose (CN102887957), etc.

In recent years, the conversion of corncob acid hydrolysis residue into levulinic acid has been considered as a high-value utilization method. Levulinic acid is one of the 12 bio-based platform chemicals screened by the U.S. Department of Energy. It has excellent reaction characteristics and can be widely used in chemical, pharmaceutical, pesticide, solvent, spice, oil additive and plasticizer fields. Sun Yan et al. used furfural slag with a solid ratio of 1:10 as raw material, hydrolyzed it in 1% sulfuric acid at 180 °C for 60 min, and obtained levulinic acid with a yield of 9.41 wt% (Chemical Engineer, 2019, 33(11): 4). Xu Xiuxiu et al. used furfural slag raw materials with a solid-to-liquid ratio of 1:10, and the molar yield of levulinic acid reached 66.6 mol% under the reaction conditions of 2% sulfuric acid, 180 °C and 2 h (Journal of Chemical Engineering of Chinese Universities, 2015, 29(6 ): 1377-1382). Zhao Qianqian et al. hydrolyzed furfural slag with a solid-to-liquid ratio of 1:20, reacted with 6% sulfuric acid at 200 °C for 40 min, and the yield of levulinic acid was 51.9 mol% (Shandong Industrial Technology, 2015 (7): 265-266). According to existing research reports, all processes adopt a batch reaction process with low solid-liquid ratio (1:10~20). Due to the low concentration of raw materials, the reaction process is not optimally controlled, resulting in low concentration of levulinic acid in the hydrolyzed product. , Low raw material hydrolysis efficiency and other deficiencies further lead to the problems of low raw material utilization rate and high energy consumption of levulinic acid extraction, which has become one of the main limiting factors for the current high production cost of levulinic acid. In addition, the hydrolysis residue produced during the preparation of levulinic acid is also a new solid waste, and how to utilize it is also an important problem that needs to be solved.

In view of the above problems, if the hydrolysis residue of corncob acid with high solid content can be efficiently converted into high-concentration levulinic acid, and the utilization of the hydrolysis residue can be realized, the above-mentioned deficiencies in the hydrolysis process of levulinic acid can be effectively overcome, and the reduction of The production cost of levulinic acid is of great significance to promote the high-value utilization of corn cob biomass resources.

Contents of the invention

The purpose of the present invention is to provide a method for high-value utilization of corncob acid hydrolysis residue, which can use industrial waste biomass xylose residue and furfural residue as raw materials to prepare levulinic acid and polyurethane foam enhancer.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A method for high-value utilization of corncob acid hydrolysis residues, using corncob acid hydrolysis residues as raw materials to prepare high-solid content, high-concentration levulinic acid and polyurethane foam enhancers;

Wherein, the preparation method of levulinic acid comprises the following steps:

S1. Mix the corncob acid hydrolysis residue with water, control the initial solid-liquid mass ratio of 1:8~10, add concentrated sulfuric acid to make the raw material liquid sulfuric acid mass concentration 1.0~3.5% for hydrolysis reaction, the reaction temperature is 160~210 ℃, the reaction During the process, feeding was carried out twice. When the temperature of the reaction solution reached the set temperature, the first feeding was carried out to make the solid-liquid ratio 1:6~7. After 10 min, the second feeding was carried out so that the solid-liquid ratio was 1:4~5, solid-liquid separation is carried out after the reaction, and the reaction solution containing the product levulinic acid and the hydrolysis residue are respectively obtained;

S2. Add new corncob acid hydrolysis residue to the obtained reaction solution containing the product levulinic acid, repeat the hydrolysis process of S1, and circulate the hydrolysis 4 times in total, without adding concentrated sulfuric acid during the reaction process, and finally obtain high-concentration levulinic acid The reaction solution.

Further, it is characterized in that, in the above-mentioned S1 and S2, in each hydrolysis reaction, when the temperature of the reaction solution rises to the set temperature, the timing starts, and the reaction time is 60-120 min.

Further, no concentrated sulfuric acid is added during the reaction in S2.

Furthermore, the preparation method of the polyurethane foam reinforcing agent is as follows: after each solid-liquid separation, the hydrolysis residue is dried and crushed to obtain a polyurethane foam reinforcing agent.

Further, the hydrolyzed residue was dried at 100 °C to constant weight, and then crushed to 180 mesh, which can be used as a reinforcing agent for polyurethane foam materials, and the addition amount is 7% of the polyol content.

Further, the use of hydrolysis residues to prepare polyurethane foam materials includes the following raw materials in parts by weight: 100 parts of 4110 polyether polyol, 1 part of triethylenediamine, 1 part of stannous octoate, 2.5 parts of AK8805 silicone oil, 3 parts of deionized water, hydrolysis 7 parts of residue enhancer, 1.05 parts of isocyanate PMDI.

Further, the acid hydrolysis residue of corncob is the solid xylose residue and/or furfural residue produced during the production process of xylose and/or furfural by hydrolysis of corncob acid.

The present invention has the following beneficial effects:

The invention uses industrial waste biomass corncob acid hydrolysis residue as raw material, and the residue generally contains residual sulfuric acid and is not easy to utilize. But using it as raw material for hydrolysis can not only use residual acid as a catalyst, save the amount of hydrolysis acid, but also realize the direct use of wet slag, which not only reduces pollution but also improves efficiency. At the same time, corn cob acid hydrolysis residue has a high cellulose content (40% to 70%), which is suitable for hydrolysis conversion. By adopting the feeding cycle hydrolysis process, the efficient hydrolysis of high solid content substrates (≥15wt%) can be achieved, which not only improves The concentration and yield of the hydrolyzed product levulinic acid have been improved, and the recycling of sulfuric acid has been realized. The main reason is that, through the feeding process, the reaction hydrolysis system can maintain a lower raw material concentration range, which not only facilitates the heat and mass transfer of the hydrolysis process, but also alleviates the inhibitory effect of high-concentration substrates and reduces by-products. , such as the generation of humus, is conducive to promoting the generation of raw materials to target products.

In addition, the hydrolysis residue can be used as a polyurethane foam enhancer after simple processing, realizing the high-value utilization of the residue. In summary, the present invention provides a method for high-value utilization of corncob acid hydrolysis residues. This process not only realizes the efficient conversion and utilization of corncob acid hydrolysis residues, but also can effectively improve the comprehensive economic benefits of deep processing and utilization of corncob resources.

Description of drawings

Fig. 1 is a statistical diagram of different hydrolysis process contrast experiments in contrast experiment 1 of the present invention;

Fig. 2 is a statistical diagram showing the influence of reinforcing agent addition on polyurethane foam density and compressive strength in Comparative Experiment 3 of the present invention.

Detailed ways

A method for high-value utilization of corncob acid hydrolysis residue provided by the present invention will be described in detail below in conjunction with the examples, but they should not be understood as limiting the protection scope of the present invention.

Example 1

Weigh 3 g of xylose residue and 30 mL of water and mix them evenly in an autoclave. The initial solid-to-liquid mass ratio is 1:10. Add concentrated sulfuric acid to make the acid concentration of the raw material liquid 1.0%. When the temperature was raised to 210°C, timing was started, and the first feeding (xylose residue) was carried out at the same time. After feeding, the solid-liquid ratio was 1:7, and the second feeding (xylose residue) was carried out after the reaction was continued for 10 min. After feeding, the solid-liquid ratio was 1:5, and the reaction was continued for 90 min before ending. After the reaction liquid was cooled to room temperature, solid-liquid separation was carried out to obtain a reaction liquid containing the product levulinic acid, and the mass yield of levulinic acid was 14.5%. The reaction liquid was directly used for the next batch of hydrolysis, no concentrated sulfuric acid was added in the reaction, and other conditions were the same as the first time, a total of 4 cycles of hydrolysis, the final concentration of levulinic acid reaction liquid was 95.6 g/L. The residue after the reaction was dried at 100°C to constant weight, and crushed to 180 mesh as a polyurethane foam enhancer.

Example 2

Weigh 3.75 g of xylose residue and 30 mL of water and mix them evenly in an autoclave. The initial solid-liquid mass ratio is 1:8. Add concentrated sulfuric acid to make the acid concentration of the raw material liquid 3.5%. Raise the temperature to 160°C and start timing. At the same time, the first feed is carried out. After the feed, the solid-liquid ratio is 1:6. After continuing the reaction for 10 minutes, the second feed is carried out. After the feed, the solid-liquid ratio is 1:5. Continue The reaction ended after 30 min. After the reaction liquid was cooled to room temperature, solid-liquid separation was carried out to obtain a reaction liquid containing the product levulinic acid, and the mass yield of levulinic acid was 15.1%. Concentrated sulfuric acid was no longer added to the reaction, and other conditions were the same as the first time. The hydrolysis cycle was repeated 4 times, and the final concentration of levulinic acid reaction liquid was 102.3 g/L. The residue after the reaction was dried at 100°C to constant weight, and crushed to 180 mesh as a polyurethane foam enhancer.

Example 3

Weigh 3.3 g of xylose residue and 30 mL of water and mix them evenly in an autoclave. The initial solid-to-liquid mass ratio is 1:9. Add concentrated sulfuric acid to make the acid concentration of the raw material liquid 2.5%. When the temperature was raised to 170°C, timing was started, and at the same time, the first feeding was carried out. After the feeding, the solid-liquid ratio was 1:7. After continuing the reaction for 10 minutes, the second feeding was carried out. After the feeding, the solid-liquid ratio was 1:4. The reaction ended after 90 min. After the reaction liquid was cooled to room temperature, solid-liquid separation was carried out to obtain a reaction liquid containing the product levulinic acid, and the mass yield of levulinic acid was 14.8%. The reaction liquid was directly used for the next batch of hydrolysis, the reaction conditions were the same as the first time, a total of 4 cycles of hydrolysis, and the final concentration of levulinic acid reaction liquid was 99.2 g/L. After the reaction, the residue was dried at 100°C to constant weight, and crushed to 180 mesh as a polyurethane foam enhancer.

Example 4

Weigh 3.75 g of furfural slag and 30 mL of water and mix them evenly in an autoclave. The initial solid-to-liquid mass ratio is 1:8. Add concentrated sulfuric acid to make the acid concentration of the raw material liquid 3.0%. Start timing at 160 ℃, and at the same time feed the first time, after feeding, the solid-liquid ratio is 1:7, continue the reaction for 10 minutes, then carry out the second feeding, after feeding, the solid-liquid ratio is 1:5, continue the reaction End after 70 min. After the reaction liquid was cooled to room temperature, solid-liquid separation was carried out to obtain a reaction liquid containing the product levulinic acid, and the mass yield of levulinic acid was 15.7%. The reaction liquid was directly used for the next batch of hydrolysis, the reaction conditions were the same as the first time, and the hydrolysis cycle was repeated 4 times, and the final concentration of levulinic acid reaction liquid was 110.4 g/L. After the reaction, the residue was dried at 100°C to constant weight, and crushed to 180 mesh as a polyurethane foam enhancer.

Example 5

Weigh 3.3 g of furfural slag and 30 mL of water and mix them evenly in an autoclave. The initial solid-to-liquid mass ratio is 1:9. Add concentrated sulfuric acid to make the acid concentration of the raw material liquid 2.0%. Start timing at 210 ℃, and at the same time feed the first time, after feeding, the solid-liquid ratio is 1:6, continue the reaction for 10 minutes, then carry out the second feeding, after feeding, the solid-liquid ratio is 1:5, continue the reaction End after 90 min. After the reaction liquid was cooled to room temperature, solid-liquid separation was carried out to obtain a reaction liquid containing the product levulinic acid, and the mass yield of levulinic acid was 15.0%. The reaction liquid was directly used for the next batch of hydrolysis, the reaction conditions were the same as the first time, and the hydrolysis cycle was repeated 4 times, and the final concentration of levulinic acid reaction liquid was 100.7 g/L. After the reaction, the residue was dried at 100°C to constant weight, and crushed to 180 mesh as a polyurethane foam enhancer.

Example 6

Weigh 3 g of xylose residue and 30 mL of water and mix them evenly in an autoclave. The initial solid-to-liquid mass ratio is 1:10. Add concentrated sulfuric acid to make the acid concentration of the raw material liquid 1.0%. Raise the temperature to 180°C and start timing. At the same time, the first feeding is carried out. After the feeding, the solid-liquid ratio is 1:6. After continuing the reaction for 10 minutes, the second feeding is carried out. After the feeding, the solid-liquid ratio is 1:4. The reaction ended after 90 min. After the reaction liquid was cooled to room temperature, solid-liquid separation was carried out to obtain a reaction liquid containing the product levulinic acid, and the mass yield of levulinic acid was 15.5%. The reaction solution was directly used for the next batch of hydrolysis, the reaction conditions were the same as the first time, and the hydrolysis cycle was repeated 4 times, and the final concentration of levulinic acid reaction solution was 108.3 g/L. After the reaction, the residue was dried at 100°C to constant weight, and crushed to 180 mesh as a polyurethane foam enhancer.

Control Experiment 1

Under the same amount of raw materials and hydrolysis reaction conditions, the effects of unfed, one-fed and two-fed processes on the formation of levulinic acid were compared, and the results are shown in Figure 1. Specific reaction conditions: the mass concentration of corn cob hydrolysis residue is 20%, 3% H ₂ SO ₄ is added for the first hydrolysis, the reaction temperature is 170 °C, and the reaction time is 60 min. The time of one feed is when the temperature is raised to the specified temperature for 0 min, and the time of the second feed is when the temperature is raised to the specified temperature for 0 min and 10 min respectively.

It can be seen from the results of comparative experiments that the yield of levulinic acid was 12.58% and the concentration of levulinic acid was 25.17 g/L using the batch reaction without feeding. Using one feeding process, the yield of levulinic acid increased to 15.00%, and the concentration of levulinic acid was 30.00 g/L. When the 2-feeding process was adopted, the yield of levulinic acid increased to 15.08%, and the concentration of levulinic acid was 30.17g/L. It can be seen that under the same amount of raw materials, the yield and concentration of the product can be effectively improved by adopting the 2 feeding process. Compared with the unfed process, the yield and concentration of levulinic acid increased by 19.87% and 19.86%, respectively. The reason for the increase is that the reaction hydrolysis system can maintain a lower raw material concentration range through the feeding process, which is not only beneficial to the heat and mass transfer of the hydrolysis process, but also alleviates the inhibitory effect of high-concentration substrates and reduces by-products , such as the generation of humus, is conducive to promoting the generation of raw materials to target products.

In addition, the influence of feeding timing on the production of levulinic acid was further investigated. When the temperature of the raw material liquid was raised to the set temperature, the timing was started, and the production intensity was significantly different when the two feedings were set at different times. The results are shown in Table 1 below.

From Table 1, it can be seen that when the raw material liquid is warmed up to the set temperature, it is better to feed the feed at 0 min and 10 min respectively. At this time, the concentration, yield and production intensity of levulinic acid are the largest. Comparing the production intensity results, it was found that the production intensity of the batch reaction without feeding was 0.42 g/(L·min), and it was increased to 0.50 g/(L·min) under the condition of two feeding processes, which proved that the feeding process can effectively improve Increase production intensity and promote production efficiency.

Control Experiment 2

In order to realize the preparation of high-concentration levulinic acid, a cycle hydrolysis control experiment was carried out. The specific operation process: after the first hydrolysis reaction is completed, the solid-liquid separation is firstly carried out to obtain the reaction liquid containing the product levulinic acid. The reaction liquid is used for the hydrolysis of the next batch, and the reaction conditions are the same as the first time. The number of hydrolysis is investigated from 1 to 6 times of hydrolysis, and the number of hydrolysis cycles is determined according to the technical and economic evaluation results of product extraction. The result is as follows.

The factory works 8,000 hours per year, the cost of sulfuric acid is 650 yuan/t, the price of levulinic acid is 20,000 yuan/t, the extraction agent is 12,000 yuan/t of dimethyl tetrahydrofuran, and the hydrolysis residue of corn cob is 100 yuan/t. After that, there is a loss of 1%, which is equivalent to changing the extraction agent every 100 times of extraction separation, and the extraction rate of levulinic acid is set to 0.8462. The economic analysis of each cycle obtained according to the set parameters is shown in Table 2.

From the data in Table 2, it can be seen that the extraction profit without circulating hydrolysis is the lowest, which is because the concentration of levulinic acid in the hydrolyzed product is too low, resulting in an increase in the amount of extractant and the cost of extraction. As the number of cycles increases, the concentration of levulinic acid also increases, which is beneficial to the extraction of the product and also helps to reduce the cost of the extraction agent. However, an excessive increase in the number of times will also result in a decrease in product yield. Therefore, according to the comprehensive comparison and calculation results, the profit is the highest when hydrolyzed 4 times, so 4 times hydrolyzed is selected as the suitable process condition.

Control Experiment 3

The residue after the hydrolysis reaction is dried at 100°C to constant weight, and crushed to a size above 180 mesh can be used as a polyurethane foam enhancer. In the control experiment, the reinforcing agent was added to the polyurethane rigid foam synthesis formula according to different addition ratios (0-10%), and the components are shown in Table 3 below.

Specific foaming process: Take 100 parts of 4110 polyether polyol, 1 part of triethylenediamine, 1 part of stannous octoate, 2.5 parts of silicone oil AK8805, 3 parts of deionized water, and different proportions of hydrolysis residues (0~10 parts). Mix well, add isocyanate PMDI (isocyanate index 1.05), pour it into the mold after high-speed stirring, the mixture reacts and expands at room temperature to form polyurethane foam, remove the mold to obtain polyurethane rigid foam, and place it for 24 hours to measure the density and compressive strength of polyurethane rigid foam. The result is shown in Figure 2 below.

The control experiment found that: when the particle size of the reinforcing agent is less than 180 mesh, there is uneven mixing of materials. When the particle size is 180 mesh and above, the material is easy to mix evenly, so the particle size of the reinforcing agent is determined to be 180 mesh. In addition, it can be further seen from the results in Figure 2 that the compressive strength of polyurethane foam without reinforcing agent is 0.1554 MPa. With the addition of reinforcing agents, both the density and compressive strength of polyurethane foam increase gradually, and the compressive strength increases faster. When the addition amount is 7%, the compressive strength of polyurethane foam reaches 0.1948 MPa, which is 25.35% higher than that without reinforcement. This shows that the addition of reinforcing agent can effectively improve the compressive strength of polyurethane foam and enhance the mechanical properties of polyurethane foam. However, when the reinforcing agent exceeds 7%, the compressive strength of polyurethane foam begins to decrease, because the addition of excess reinforcing agent will increase the viscosity of the system and affect the foaming process. At the same time, too much reinforcing agent will cause the cells to coalesce and reduce the mechanical properties of the material. Therefore, the amount of reinforcing agent added is determined to be 7% of the amount of polyol.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made, these improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (3)

1. A method for high-value utilization of corncob acid hydrolysis residues, characterized in that, the acid hydrolysis residues of corncobs are used as raw materials to prepare a polyurethane foam enhancer; specifically, the corncob acid hydrolysis residues are mixed with water to control the initial The mass ratio of solid to liquid is 1:8~10. Add concentrated sulfuric acid so that the mass concentration of sulfuric acid in the raw material liquid is 1.0~3.5% for hydrolysis reaction. The reaction temperature is 160~210°C. When the temperature was fixed, the first feed was carried out to make the solid-liquid ratio 1:6~7, and the second feed was carried out after 10 min to make the solid-liquid ratio 1:4-5. After the reaction, the solid-liquid separation was carried out. Respectively obtain the reaction solution containing the product levulinic acid and the hydrolysis residue; the drying condition of the hydrolysis residue is 100°C to constant weight, and the crushed particle size is 180 mesh; Wherein, the preparation method of the polyurethane foam reinforcing agent is as follows: after each solid-liquid separation, the hydrolysis residue is dried and crushed to obtain a polyurethane foam reinforcing agent. 2. The method for high-value utilization of a kind of corncob acid hydrolysis residue according to claim 1, characterized in that, utilizing the hydrolysis residue to prepare the polyurethane foam material comprises the following raw materials in parts by weight: 100 parts of 4110 polyether polyol, 1 part of triethylenediamine, 1 part of stannous octoate, 2.5 parts of AK8805 silicone oil, 3 parts of deionized water, 7 parts of hydrolysis residue enhancer, and 1.05 parts of isocyanate PMDI. 3. A method for high-value utilization of corncob acid hydrolysis residues according to claim 1, characterized in that: the corncob acid hydrolysis residues are produced in the production process of xylose and/or furfural produced by corncob acid hydrolysis solid xylose residue and/or furfural residue.