Modified filter aid, preparation method and filtering treatment method of straw cellulose enzymatic hydrolysate

Abstract

The invention provides a modified filter aid, a preparation method and a filtering treatment method of straw cellulose enzymatic hydrolysate. Wherein the modified filter aid is prepared from a filter aid, alkali liquor and a silane coupling agent. When the modified filter aid provided by the invention is added into the high-viscosity enzymatic hydrolysate, the filtering efficiency and flux can be greatly improved, and the filter aid is easy to recover, can be recycled and has relatively good economic practicability.

Description

Technical Field

[0001] The invention relates to the technical field of biomass energy utilization, and more particularly to a modified filter aid, a preparation method and a filtering treatment method for straw cellulose enzymatic hydrolyzate. Background Art

[0002] Straw is a biomass resource with fast regeneration speed and high yield, and is also a widely distributed biomass renewable resource in nature. If straw can be used in a high-value way and converted into sugar or other useful chemicals after degradation, it can not only alleviate the shortage of fossil energy such as coal, oil, and natural gas, but also avoid environmental pollution caused by burning straw.

[0003] In recent years, in order to improve the utilization rate of straw, the separation of straw components has become the research focus of its high-value utilization. The contents of cellulose, hemicellulose and lignin in straw are 40-50%, 20-30% and 10-15% respectively. The key to high-value utilization of straw is to destroy the cross-linked structure of the three major components in straw, separate and extract cellulose, hemicellulose and lignin, of which cellulose and hemicellulose can continue to be enzymatically hydrolyzed to generate C5 and C6 sugars, which have been used in industry for fermentation to produce ethanol, butanol, lactic acid and other biomass chemicals.

[0004] At present, there are many methods for the treatment of straw cellulose enzymatic hydrolysis and saccharification. However, during the process of cellulose enzymatic hydrolysis, the viscosity of the hydrolysate will continue to increase, and the particle size of the hydrolysate is small (1-10μm), which greatly affects the filtration and centrifugation efficiency of the hydrolysate under high viscosity. In the solid-liquid separation of the hydrolysate on an industrial scale, the filtration and centrifugation of the solution are difficult, time-consuming and power-consuming. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a modified filter aid and a preparation method thereof. The modified filter aid provided by the present invention can be added to a high viscosity solution to greatly accelerate the filtration efficiency and flux of the solution.

[0006] Firstly, one of the purposes of the present invention is to provide a modified filter aid, which is prepared from a filter aid, an alkali solution A, and a silane coupling agent, wherein the filter aid is selected from natural silica powder.

[0007] Preferably, the natural silicon dioxide powder is selected from at least one of natural diatomaceous earth, perlite and clay; more preferably, the particle size of the natural silicon dioxide powder is 50 to 300 meshes.

[0008] Preferably, the alkali solution A is selected from an aqueous solution of an inorganic strong base; more preferably, the alkali solution A is selected from an aqueous solution of at least one alkali selected from sodium hydroxide and potassium hydroxide.

[0009] Preferably, the silane coupling agent is selected from at least one of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N,N-diethyl-3-(trimethoxysilyl)propylamine, N,N-diethyl-3-(triethoxysilyl)propylamine, N1-(3-(trimethoxysilyl)propyl)ethane-1,2-diamine and N1-(3-(triethoxysilyl)propyl)ethane-1,2-diamine.

[0010] Secondly, the second object of the present invention is to provide a method for preparing the modified filter aid of one of the objects of the present invention.

[0011] Specifically, the method comprises the following steps:

[0012] The filter aid is washed with water to remove inorganic salts and impurities, and alkaline solution A is added to adjust the pH. After adding a silane coupling agent for reaction, the modified filter aid is obtained after solid-liquid separation, solid phase washing and drying.

[0013] Furthermore, in the above steps, the pH is adjusted to 10-14 using alkaline solution A; the solid-liquid ratio of the added filter aid to the added alkaline solution A is 1 / 5-1 / 20; the mass of the added silane coupling agent is 0.1-1% of the mass of the filter aid, preferably 0.5-1%.

[0014] Furthermore, after adding alkaline solution A to adjust the pH and adding a silane coupling agent, the reaction is carried out at room temperature for 1 to 2 hours.

[0015] Again, the third object of the present invention is to provide a filtering treatment method for straw cellulose enzymatic hydrolyzate with a modified filter aid as one of the objects of the present invention.

[0016] Specifically, the modified filter aid, which is one of the purposes of the present invention, can promote the solid-liquid separation of the filtrate; preferably, it can well accelerate the filtration efficiency of the straw cellulose hydrolysate, realize the continuous operation of filtering and washing the hydrolysate, and extract lignin in the filter cake at the same time, and the filter aid can also be recycled, having good economic use value.

[0017] It is worth mentioning that in the conventional straw comprehensive utilization process, the mixed sugar solution after the straw cellulose is enzymatically hydrolyzed by cellulase is usually filtered and the enzymatic residue is washed before being sent to the subsequent stage for sugar solution fermentation. Therefore, the filtration efficiency of the straw cellulose enzymatic hydrolyzate affects the efficiency of the straw comprehensive utilization process.

[0018] In the present invention, a certain amount of modified filter aid is added to the straw cellulose enzymatic hydrolysate to accelerate the filtration efficiency and flux, wherein the method for filtering and washing the straw cellulose enzymatic hydrolysate with the modified filter aid comprises the following steps:

[0019] Step 1: Add modified filter aid to the straw cellulose enzymatic hydrolyzate, separate the mixed solution into solid and liquid, wash the filter residue, and collect the filtrate.

[0020] Step 2: adding the filter residue to alkali solution B to heat and react, filtering again to obtain a solid phase of straw ash and filter aid and a liquid phase containing lignin;

[0021] Preferably, the specifics are as follows:

[0022] Step 1: After the straw raw material is completely enzymatically hydrolyzed, a certain amount of treated modified filter aid is added to the straw cellulose enzymatic hydrolyzate, and the mixed solution is continuously filtered through solid-liquid separation equipment such as a belt filter and a disc filter, and the filtered residue is washed with water to wash away the residual sugar liquid in the solid, and the filtrate is collected for subsequent fermentation operation;

[0023] Step 2: adding the filter residue to alkaline solution B to heat and react, filtering again to obtain a solid phase of straw ash and filter aid and a solution containing alkaline lignin.

[0024] Preferably, in step 1, the amount of modified filter aid added is 1 / 10 to 1 / 50 of the liquid volume.

[0025] Preferably, in step 2, the alkali solution B is an aqueous solution of sodium hydroxide or potassium hydroxide; and the solid-liquid ratio of the filter residue to the alkali solution B is 1 / 5 to 1 / 20.

[0026] Preferably, in step 2, the filter residue is in alkaline solution, the pH of the reaction system is 12-14, the reaction temperature is 20-60° C., and the reaction time is 1-4 h.

[0027] Furthermore, the straw ash and the solid phase of the filter aid can be used for the regeneration of the filter aid. Specifically, the regeneration method of the filter aid is: calcining the straw ash and the solid phase of the filter aid to obtain the regenerated filter aid.

[0028] Preferably, the filter aid regeneration method is as follows: the obtained straw ash and the solid phase of the filter aid are placed in a muffle furnace for calcination to obtain a regenerated filter aid.

[0029] Preferably, the temperature for calcining the solid phase straw ash and filter aid is 480-550° C., and the calcination time is 2-3 hours.

[0030] It is worth mentioning that since the ash contained in the straw is amorphous silica ash, it is loose and porous and can be directly mixed and reused as a recovered filter aid, which has little effect on the performance of the filter aid.

[0031] It is worth mentioning that the straw cellulose hydrolysate is a suspension containing muddy and sticky fine particles, and the filtration efficiency is not good using conventional filtration methods. The present invention proposes adding a certain amount of modified filter aid during conventional filtration or centrifugation of the straw cellulose hydrolysate. Since the added modified filter aid can form rigid particles with porous cake layers, the viscosity of the filter cake is reduced, and it has good permeability and low fluid resistance, which can greatly accelerate the filtration efficiency and flux; at the same time, the obtained filter residue can be used to recover the lignin therein by alkali dissolution method, and the remaining straw ash can be mixed with the filter aid after regeneration and recycled. It can be seen that the present invention provides a low-cost continuous treatment process that can accelerate the production efficiency and production scale of straw biomass, thereby better serving the industrial utilization of straw biomass.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] 1. The modified filter aid used in the present invention has a large specific surface area, can adsorb colloidal substances in enzymatic hydrolysates such as lignin and polysaccharides, and form a filter cake with a high porosity, and is also well suitable for the acidic environment under enzymatic hydrolysis or strong acid cellulose hydrolysis.

[0034] 2. The present invention adopts an amino-type silane coupling agent to modify the filter aid, which better avoids the compaction of the filter aid during the filtration of the enzymatic solution and the subsequent alkaline extraction of lignin, thereby affecting the filtration rate. The main reason is that the surface properties of the filter aid can be changed through pretreatment. Colloidal substances such as lignin and polysaccharides in the enzymatic solution are negatively charged and repel each other. When the local amino-positive charge center on the surface of the filter aid is adsorbed and neutralized, the repulsive force of the colloidal particles disappears and flocculation occurs. This flocculation includes self-aggregation of the colloidal particles and aggregation on the surface of the filter aid. This aggregate is a soft flocculent with shear reversibility. The loose soft flocculent filter layer is conducive to filtration dehydration and the formation of a uniform filter cake.

[0035] 3. The method of adding the modified filter aid to the enzymatic hydrolyzate is simple and easy, which accelerates the filtration rate of the enzymatic hydrolyzate and reduces the water content of the filter cake, thereby increasing the solid-liquid separation efficiency, so that the solid-liquid separation operation can be carried out continuously. At the same time, the lignin in the filter cake can be easily extracted, and the filter aid of the present invention is easy to recover and can be recycled, and is suitable for the industrial application of straw biomass. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The process flow chart of the present invention using modified filter aids to promote enzymatic hydrolysis of straw cellulose and lignin extraction is shown. DETAILED DESCRIPTION

[0037] The present invention is described in detail below in conjunction with specific drawings and embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

[0038] In the following examples and comparative examples, unless otherwise specified, the experimental methods used are conventional methods, and the materials, reagents, etc. used are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0039] In the following embodiments and comparative examples, the filter used may be a disc filter, a belt filter or other filtering equipment. For example, a disc filter FT-1-400 produced by Chongqing Jiangbei Machinery Co., Ltd. with a filtering area of ​​1 m 2 , power is 5.5KW, speed is 260r / min, operating pressure is 0.1MPa, and water washing volume is the volume of enzymatic hydrolyzate.

[0040] In the following examples and comparative examples, the source of the straw raw material is not limited to the common wheat, corn, and sugarcane straws, but can be straws of various crops.

[0041] In the following examples and comparative examples, the source of the straw cellulose enzymatic hydrolyzate is a mixed solution obtained by the straw pretreatment and enzymatic hydrolysis method provided in the patent application (application number CN103031340A or application number CN103031339A).

[0042] Example 1

[0043] Add 10 kg of washed natural diatomaceous earth to NaOH alkali solution, the solid-liquid ratio of natural diatomaceous earth to alkali solution is 1 / 5, add 10 g of 3-aminopropyltrimethoxysilane, the pH of the reaction system is 10, react at room temperature for 1 hour, filter the solid after the reaction, wash with water and dry to obtain the modified filter aid. Add the modified filter aid to the cellulose hydrolysate, the amount added is 1 / 10 of the volume of the hydrolysate, filter with a disc filter, wash the filtered residue with water, and the filtrate is the sugar-containing solution for fermentation. Add the filter residue to NaOH alkali solution for reaction, the solid-liquid ratio of the filter residue to the alkali solution is 1 / 5, the pH of the reaction system is 12, react at 20°C for 1 hour and filter again, the filtrate is the alkaline lignin solution, and the filtered solid phase is recovered for standby use.

[0044] Example 2

[0045] 10 kg of washed natural diatomaceous earth was added to NaOH alkali solution, the solid-liquid ratio of natural diatomaceous earth to alkali solution was 1 / 5, 50 g of 3-aminopropyltrimethoxysilane was added, the pH of the reaction system was 10, the reaction was carried out at room temperature for 1 hour, the solid was filtered after the reaction was completed, and the modified filter aid was obtained after washing with water and drying. The modified filter aid was added to the cellulose hydrolysate, the amount added was 1 / 10 of the volume of the hydrolysate, and the filter residue was washed with water after filtration, and the filtrate was the sugar-containing solution for fermentation. The filter residue was added to NaOH alkali solution and heated for reaction, the solid-liquid ratio of the filter residue to the alkali solution was 1 / 5, the pH of the reaction system was 12, and the reaction was carried out at 20°C for 1 hour and then filtered again. The filtrate was the alkaline lignin solution, and the solid phase after filtration was recovered for standby use.

[0046] Example 3

[0047] 10 kg of washed natural diatomaceous earth was added to NaOH alkali solution, the solid-liquid ratio of natural diatomaceous earth to alkali solution was 1 / 5, 100 g of 3-aminopropyltrimethoxysilane was added, the pH of the reaction system was 10, the reaction was carried out at room temperature for 1 hour, the solid was filtered after the reaction was completed, and the modified filter aid was obtained after washing with water and drying. The modified filter aid was added to the cellulose hydrolysate, the amount added was 1 / 10 of the volume of the hydrolysate, and the filter residue was washed with water after filtration, and the filtrate was the sugar-containing solution for fermentation. The filter residue was added to NaOH alkali solution for heating reaction, the solid-liquid ratio of the filter residue to the alkali solution was 1 / 5, the pH of the reaction system was 12, and the reaction was carried out at 20°C for 1 hour and then filtered again. The filtrate was the alkaline lignin solution, and the solid phase after filtration was recovered for standby use.

[0048] Example 4

[0049] 10 kg of washed natural diatomaceous earth was added to NaOH alkali solution, the solid-liquid ratio of natural diatomaceous earth to alkali solution was 1 / 5, 50 g of 3-aminopropyltriethoxysilane was added, the pH of the reaction system was 10, the reaction was carried out at room temperature for 1 hour, the solid was filtered after the reaction was completed, and the modified filter aid was obtained after washing with water and drying. The modified filter aid was added to the cellulose hydrolysate, the amount added was 1 / 10 of the volume of the hydrolysate, and the filter residue was washed with water after filtration, and the filtrate was the sugar-containing solution for fermentation. The filter residue was added to NaOH alkali solution and heated for reaction, the solid-liquid ratio of the filter residue to the alkali solution was 1 / 5, the pH of the reaction system was 12, and the reaction was carried out at 20°C for 1 hour and then filtered again. The filtrate was the alkaline lignin solution, and the solid phase after filtration was recovered for standby use.

[0050] Example 5

[0051] 10 kg of washed natural diatomaceous earth was added to NaOH alkali solution, the solid-liquid ratio of natural diatomaceous earth to alkali solution was 1 / 10, 50 g of N, N-diethyl-3-(trimethoxysilyl)propylamine was added, the pH of the reaction system was 12, the reaction was carried out at room temperature for 2 hours, the solid was filtered after the reaction was completed, and the modified filter aid was obtained after washing with water and drying. The modified filter aid was added to the cellulose hydrolysate, the amount added was 1 / 10 of the volume of the hydrolysate, and the filter residue was washed with water after filtration, and the filtrate was the sugar-containing solution for fermentation. The filter residue was added to NaOH alkali solution for heating reaction, the solid-liquid ratio of the filter residue to the alkali solution was 1 / 10, the pH of the reaction system was 13, and the reaction was carried out at 40°C for 2 hours and then filtered again. The filtrate was the alkaline lignin solution, and the solid phase after filtration was recovered for standby use.

[0052] Example 6

[0053] 10 kg of washed natural diatomaceous earth was added to KOH alkali solution, the solid-liquid ratio of natural diatomaceous earth to alkali solution was 1 / 10, 50 g of N, N-diethyl-3-(triethoxysilyl)propylamine was added, the pH of the reaction system was 12, the reaction was carried out at room temperature for 2 hours, the solid was filtered after the reaction was completed, and the modified filter aid was obtained after washing with water and drying. The modified filter aid was added to the cellulose hydrolysate, the amount added was 1 / 10 of the volume of the hydrolysate, and the filter residue was washed with water after filtration, and the filtrate was the sugar-containing solution for fermentation. The filter residue was added to KOH alkali solution and heated for reaction, the solid-liquid ratio of the filter residue to the alkali solution was 1 / 10, the pH of the reaction system was 13, and the reaction was carried out at 40°C for 2 hours and then filtered again. The filtrate was the alkaline lignin solution, and the solid phase after filtration was recovered for standby use.

[0054] Example 7

[0055] 10 kg of washed natural diatomaceous earth was added to KOH alkali solution, the solid-liquid ratio of natural diatomaceous earth to alkali solution was 1 / 20, 50 g of N1-(3-(trimethoxysilyl)propyl)ethane-1,2-diamine was added, the pH of the reaction system was 14, the reaction was carried out at room temperature for 2 hours, the solid was filtered after the reaction was completed, and the modified filter aid was obtained after washing with water and drying. The modified filter aid was added to the cellulose hydrolysate, the amount added was 1 / 10 of the volume of the hydrolysate, and the filter residue was washed with water after filtration, and the filtrate was the sugar-containing solution for fermentation. The filter residue was added to KOH alkali solution for heating reaction, the solid-liquid ratio of the filter residue to the alkali solution was 1 / 20, the pH of the reaction system was 14, and the reaction was carried out at 60°C for 4 hours and then filtered again. The filtrate was the alkaline lignin solution, and the filtered solid phase was recovered for standby use.

[0056] Example 8

[0057] 10 kg of washed natural diatomaceous earth was added to KOH alkali solution, the solid-liquid ratio of natural diatomaceous earth to alkali solution was 1 / 20, 50 g of N1-(3-(triethoxysilyl)propyl)ethane-1,2-diamine was added, the pH of the reaction system was 14, the reaction was carried out at room temperature for 2 hours, the solid was filtered after the reaction was completed, and the modified filter aid was obtained after washing with water and drying. The modified filter aid was added to the cellulose hydrolysate, the amount added was 1 / 10 of the volume of the hydrolysate, and the filter residue was washed with water after filtration, and the filtrate was the sugar-containing solution for fermentation. The filter residue was added to KOH alkali solution for heating reaction, the solid-liquid ratio of the filter residue to the alkali solution was 1 / 20, the pH of the reaction system was 14, and the reaction was carried out at 60°C for 4 hours and then filtered again. The filtrate was the alkaline lignin solution, and the filtered solid phase was recovered for standby use.

[0058] Example 9

[0059] 10 kg of washed natural clay was added to NaOH alkali solution, the solid-liquid ratio of natural clay to alkali solution was 1 / 5, 50 g of 3-aminopropyltrimethoxysilane was added, the pH of the reaction system was 10, the reaction was carried out at room temperature for 1 hour, the solid was filtered after the reaction was completed, and the modified filter aid was obtained after washing with water and drying. The modified filter aid was added to the cellulose hydrolysate, the amount added was 1 / 10 of the volume of the hydrolysate, and the filter residue was washed with water after filtration, and the filtrate was the sugar-containing solution for fermentation. The filter residue was added to NaOH alkali solution and heated for reaction, the solid-liquid ratio of the filter residue to the alkali solution was 1 / 5, the pH of the reaction system was 12, and the reaction was carried out at 20°C for 1 hour and then filtered again. The filtrate was the alkaline lignin solution, and the solid phase after filtration was recovered for standby use.

[0060] Example 10

[0061] 10 kg of washed natural perlite was added to NaOH alkali solution, the solid-liquid ratio of natural perlite to alkali solution was 1 / 5, 50 g of 3-aminopropyltrimethoxysilane was added, the pH of the reaction system was 10, the reaction was carried out at room temperature for 1 hour, the solid was filtered after the reaction was completed, and the modified filter aid was obtained after washing with water and drying. The modified filter aid was added to the cellulose hydrolysate, the amount added was 1 / 10 of the volume of the hydrolysate, and the filter residue was washed with water after filtration, and the filtrate was the sugar-containing solution for fermentation. The filter residue was added to NaOH alkali solution and heated for reaction, the solid-liquid ratio of the filter residue to the alkali solution was 1 / 5, the pH of the reaction system was 12, and the reaction was carried out at 20°C for 1 hour and then filtered again. The filtrate was the alkaline lignin solution, and the solid phase after filtration was recovered for standby use.

[0062] Embodiment 11

[0063] 10 kg of washed natural diatomaceous earth was added to NaOH alkali solution, the solid-liquid ratio of natural diatomaceous earth to alkali solution was 1 / 5, 50 g of 3-aminopropyltrimethoxysilane was added, the pH of the reaction system was 10, the reaction was carried out at room temperature for 1 hour, the solid was filtered after the reaction was completed, and the modified filter aid was obtained after washing with water and drying. The modified filter aid was added to the cellulose hydrolysate, the amount added was 1 / 50 of the volume of the hydrolysate, and the filter residue was washed with water after filtration, and the filtrate was the sugar-containing solution for fermentation. The filter residue was added to NaOH alkali solution and heated for reaction, the solid-liquid ratio of the filter residue to the alkali solution was 1 / 5, the pH of the reaction system was 12, and the reaction was carried out at 20°C for 1 hour and then filtered again. The filtrate was the alkaline lignin solution, and the solid phase after filtration was recovered for standby use.

[0064] Comparative Example 1

[0065] The cellulose hydrolysate is filtered using a disc filter, and the filtered residue is washed with water. The filtrate is the sugar-containing solution for fermentation. The residue is added to NaOH alkali solution for heating reaction, the solid-liquid ratio of the residue to the alkali solution is 1 / 5, the pH of the reaction system is 12, and the reaction is carried out at 20°C for 1h before filtering again. The filtrate is the alkaline lignin solution.

[0066] Comparative Example 2

[0067] The washed natural diatomaceous earth is added to the cellulose hydrolysate in an amount of 1 / 10 of the volume of the hydrolysate, filtered using a disc filter, and the filtered residue is washed with water. The filtrate is the sugar-containing solution for fermentation. The residue is added to the NaOH alkali solution for heating reaction, the solid-liquid ratio of the residue to the alkali solution is 1 / 5, the pH of the reaction system is 12, and the reaction is carried out at 20°C for 1h before filtering again. The filtrate is the alkaline lignin solution.

[0068] Table 1 shows the filtration performance test data for Examples 1 to 11 and Comparative Examples 1 to 2. All Examples and Comparative Examples use the same filtration device, and the amount of filtration water washing and cellulose hydrolysate used are the same. The filtration time is the time taken for the first filtration of the straw hydrolysate to be completed. The filtrate sugar yield is calculated based on the total content of glucose and xylose, that is, the proportion of sugar in the filtrate after washing relative to the content in the straw hydrolysate; the filter cake moisture content is the proportion of moisture in the filter cake to the total mass of the filter cake when the hydrolysate is first filtered. The alkaline lignin recovery rate is the proportion of lignin in the straw hydrolysate that enters the alkaline solution.

[0069] Table 1

[0070]

[0071] It can be seen from the data in Table 1 that after the modified filter aid is added in Examples 1 to 11, even when the amount of modified filter aid added is less (Example 11), the filtration time of the filtrate is significantly shortened, and the sugar yield and lignin yield of the filtrate are significantly increased. At the same time, the water content of the filter cake is also reduced, and the solid content is increased, which can save water and electricity during filtration and drying, and has significant process economy.

[0072] It can be seen from Comparative Example 1 that when no filter aid is added, the filtration time is long, the water content of the filter cake is too high, and the yield of sugar and the yield of lignin are both low.

[0073] It can be seen from Comparative Example 2 that, although the direct use of natural diatomaceous earth helps to shorten the filtration time and increase the yield of sugar solution and lignin, the effect is obviously not as good as that of the modified natural diatomaceous earth.

[0074] Furthermore, the solid phases filtered and recovered in Example 2, Example 9, and Example 10 were selected and put into a muffle furnace for calcination recovery, the calcination temperature was set to 550° C., the calcination time was 2 h, and the powder after calcination was regarded as a natural filter aid. The silane reagent was added again for modification and use according to the method of Example 2, Example 9, and Example 10, and the filtration time of the enzymatic hydrolyzate of the repeatedly recycled filter aid and the water content of the filtered filter cake were tested to evaluate the recycling situation. The specific data are shown in Table 2.

[0075] Table 2

[0076]

[0077] It can be seen from the data in Table 2 that the recovered filter aid can be reused after calcination and re-modification, and can promote the filtration of the enzymatic hydrolyzate. Among them, the filter aid of Example 2 has little difference in effect when reused, and the filter aids of Examples 9 and 10 increase the filtration time when reused, and the water content of the filter cake does not change much.

[0078] The use of the modified filter aid provided by the invention has a good effect of promoting filtration of a high-viscosity mixed liquid, and has process economy of low energy consumption and high yield.

[0079] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A modified filter aid, characterized in that: The modified filter aid is prepared from a filter aid, alkali solution A, and a silane coupling agent; The filter aid is selected from natural silicon dioxide powder.

2. The modified filter aid according to claim 1, characterized in that The natural silicon dioxide powder is selected from at least one of natural diatomaceous earth, perlite and clay; The particle size of the natural silicon dioxide powder is 50 to 300 meshes.

3. The filter aid according to claim 1, characterized in that The alkali solution A is selected from an aqueous solution of an inorganic strong base; Preferably, the alkali solution A is an aqueous solution of at least one alkali selected from sodium hydroxide and potassium hydroxide.

4. The modified filter aid according to claim 1, characterized in that The silane coupling agent is selected from at least one of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N,N-diethyl-3-(trimethoxysilyl)propylamine, N,N-diethyl-3-(triethoxysilyl)propylamine, N1-(3-(trimethoxysilyl)propyl)ethane-1,2-diamine and N1-(3-(triethoxysilyl)propyl)ethane-1,2-diamine.

5. The method for preparing the modified filter aid according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: washing the filter aid with water, adding alkaline solution A to adjust pH, adding a silane coupling agent for reaction, performing solid-liquid separation, and washing and drying the solid phase to obtain the modified filter aid.

6. The method for preparing the modified filter aid according to claim 5, characterized in that: The solid-liquid ratio of the mass of the filter aid to the added alkali solution A is 1 / 5 to 1 / 20; and / or, The pH is adjusted to 10-14.

7. The method for preparing the modified filter aid according to claim 5, characterized in that: The mass of the added silane coupling agent is 0.1-1% of the mass of the filter aid, preferably 0.5-1%; and / or, The reaction time is 1 to 2 hours, and the reaction temperature is room temperature.

8. A method for filtering a straw cellulose enzymatic hydrolyzate using the modified filter aid according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: Step 1: adding a modified filter aid to the straw cellulose enzymatic hydrolyzate, performing solid-liquid separation on the mixed solution, washing the filter residue, and collecting the filtrate; Step 2: Add the filter residue to alkaline solution B for heating and reaction, and filter again to obtain a solid phase of straw ash and filter aid and a liquid phase containing lignin.

9. The method according to claim 8, characterized in that In the step 1, the modified filter aid is added in an amount of 1 / 10 to 1 / 50 of the liquid volume; and / or, In the step 2, the solid-liquid ratio of the filter residue to the alkali solution B is 1 / 5 to 1 / 20; and / or, The alkali solution B is an aqueous solution of sodium hydroxide or potassium hydroxide; and / or, The pH of the reaction system is 12 to 14; and / or, The heating reaction temperature is 20 to 60°C; and / or, The heating reaction time is 1 to 4 hours.

10. The method according to claim 8, characterized in that The method further comprises step three: calcining the straw ash and the solid phase of the filter aid to obtain a regenerated filter aid; Preferably, The temperature at which the solid phase straw ash and filter aid are calcined is 480-550° C.; and / or, The solid phase straw ash and filter aid are calcined for 2 to 3 hours.

Images