Method for producing methanol by intensifying straw saccharification through titanium dioxide photocatalysis coupling enzyme
Through the method of photocatalytic coupling enzyme strengthening of titanium dioxide, the problem of high cost and low efficiency of catalysts in the existing straw gasification methanol production process is solved, and efficient and environmentally friendly methanol production is achieved.
Patent Information
- Application Number
- CN202411910257.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-24
- Publication Date
- 2025-03-28
AI Technical Summary
The catalyst in the existing straw gasification methanol production process has high cost, low efficiency, requires a high temperature and high pressure environment and is not environmentally friendly.
Using the method of photocatalytic coupling enzyme strengthening of titanium dioxide, the steps of straw pretreatment, cellulose enzymatic removal, preparation of compounded TiO2 photocatalysts and catalytic reduction sugars to produce methanol, so as to achieve methanol production in straw saccharification.
The enzymatic saccharification rate of straw is improved, and the prepared compound TiO2 photocatalyst has the advantages of stable chemical properties, high catalytic activity, environmentally friendly and low cost, and realizes the ability to selectively generate methanol under normal temperature and pressure.
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Figure CN119707628A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of straw resource utilization, and in particular relates to a method for strengthening straw saccharification and methanol production by titanium dioxide photocatalysis coupled with enzyme. Background Art
[0002] The increasing shortage of fossil energy and the deterioration of the ecological environment have led people to continuously develop and utilize green and renewable biomass energy to replace traditional fossil energy. Lignocellulosic biomass is an important renewable carbon resource, among which crop straw is the simplest, most productive and most widely distributed biomass resource on the earth. Crop straw can be used to produce biogas through anaerobic fermentation, alcohol and hydrocarbon fuels through hydrothermal catalysis, cracking and liquefaction, bio-oil quality improvement and solid fuel preparation. The development of these technologies can effectively solve the problems of fossil energy shortage and ecological environment deterioration.
[0003] Methanol (CH3OH) is the simplest saturated monohydric alcohol and an important intermediate in the production of high value-added chemicals. The development of methanol economy is conducive to the green and low-carbon transformation of the chemical, energy and transportation industries. The technology of using crop straw to produce methanol is generally divided into two parts. The first part is the production of raw gas and synthesis gas by thermal chemical gasification of biomass; the second part is the synthesis of crude methanol by catalysis under certain pressure and temperature conditions, and the crude methanol is distilled to obtain methanol products. The cell wall in the straw has a high degree of fiberization and is difficult to decompose. Therefore, it is much more difficult to produce methanol from straw than using fossil energy. In addition, the existing methanol synthesis catalysts have the disadvantages of high cost, corrosion and loss of equipment by strong acids and alkalis, high temperature and high pressure environment, environmental unfriendliness, long cycle and low efficiency. Summary of the invention
[0004] In order to solve the problems of high catalyst cost, low efficiency, high temperature and high pressure environment and environmental unfriendliness in the existing straw gasification process for producing methanol, the present invention provides a method for enhancing straw saccharification and methanol production by titanium dioxide photocatalysis coupled with enzyme.
[0005] The technical solution of the present invention:
[0006] A method for enhancing straw saccharification and methanol production by titanium dioxide photocatalysis coupled with enzymes, comprising the following steps:
[0007] Step 1: Straw pretreatment:
[0008] The straw powder is placed in deionized water and stirred for a period of time, and then TiO2 is added. After stirring for a certain period of time, the pH is adjusted to alkaline, and the resulting mixed system is transferred to an ultrasonic and photocatalytic reactor, first adsorbed in the dark, and then the catalytic reaction is completed under ultraviolet light. After the reaction is completed, titanium dioxide and straw are separated, and the straw is dried to constant weight to complete the straw pretreatment;
[0009] Step 2: Enzymatic hydrolysis of cellulose:
[0010] Adding acetic acid-sodium acetate buffer to the pretreated straw obtained in step 1, adding cellulase to the obtained mixed system for enzymolysis, and filtering to obtain an enzymolysis solution containing reducing sugars;
[0011] Step 3: Preparation of composite TiO2 photocatalyst:
[0012] A certain amount of TiO2 is dispersed in an alkaline solution, H-TiO2 is synthesized by hydrothermal method, and the solution is washed with deionized water and dilute nitric acid until neutral. The obtained H-TiO2 sample is collected and a certain amount of ammonium chloride and ethanol solution are added, and the solution is heated under reflux to obtain NH4-TiO2. The NH4-TiO2 sample is collected, a certain amount of NH4-TiO2 is added with a certain amount of copper nitrate solution and zinc chloride solution, and the solid sample is collected after stirring at room temperature for a certain period of time, and then dried and calcined to obtain a composite TiO2 photocatalyst CZ-TiO2.
[0013] Step 4: Catalytic reduction of sugar to produce methanol:
[0014] The enzymatic hydrolyzate containing reducing sugars obtained in step 2, water and acetonitrile are mixed in proportion to obtain a mixed solution and the composite TiO2 photocatalyst obtained in step 3 are placed in a photocatalytic reactor, nitrogen is introduced after mixing, and a photocatalytic reaction is carried out under the irradiation of a high-pressure ultraviolet lamp to obtain methanol.
[0015] Furthermore, in step 1, the particle size of the straw powder is 60 mesh, the mass volume ratio of the straw powder to deionized water is 10g:500-1000mL, and the time for soaking and stirring the straw powder in deionized water is 0.5-1.5h.
[0016] Furthermore, in step 1, the particle size of TiO2 is 20 nm, the amount of TiO2 added is calculated based on the mass ratio of straw powder to TiO2 of 10:0.5-2, the stirring time after adding TiO2 is 0.5-1.5 h, and the pH is adjusted to an alkaline pH value of 8-11.
[0017] Furthermore, in step 1, the adsorption time under dark conditions is 0.5 to 1.5 hours, the catalytic reaction time under ultraviolet light is 0.5 to 1.5 hours, and the wavelength of the ultraviolet light is 365 nm.
[0018] Furthermore, the concentration of the acetic acid-sodium acetate buffer in step 2 is 0.10 mol / L, and the pH is 4.0-7.0; the amount of the cellulase added is calculated based on the mass ratio of the pretreated straw to the cellulase of 0.2-5 g:20000 U, and the enzymatic activity of the cellulase is 50000 U / g; and the reaction conditions of the enzymolysis are enzymolysis at 150 r / min and 30-60° C. for 24-72 h.
[0019] Furthermore, the alkaline solution in step three is a NaOH solution with a concentration of 10 mol / L, the mass volume ratio of TiO2 to the alkaline solution is 0.5-2 g:90 mL, and the temperature of the hydrothermal synthesis is 130-180°C.
[0020] Furthermore, in step three, the mass volume ratio of the H-TiO2 sample, ammonium chloride and ethanol solution is 1-5g:5-30g:100mL, the volume concentration of the ethanol solution is 50%; and the heating reflux time is 8-20h.
[0021] Furthermore, the concentrations of the copper nitrate solution and the zinc chloride solution in step three are both 1 mol / L, and the mass volume ratio of the NH4-TiO2 sample, the copper nitrate solution and the zinc chloride solution is 0.5-5 g:7.81 mL:1-30 mL; the concentration of copper ions in the obtained reaction system is 5 wt%, the concentration of zinc ions is 1.25-7.25 wt%, the stirring time at room temperature is 12-36 h, and the calcination is calcined at 400-600 ° C for 1-3 h.
[0022] Furthermore, in step 4, the volume ratio of the enzymatic hydrolyzate containing reducing sugars, water and acetonitrile in the mixed solution is 1:1:8, and the volume mass ratio of the mixed solution to the composite TiO2 photocatalyst is 10mL:100-300mg.
[0023] Furthermore, in step 4, the nitrogen introduction time is 1 to 3 minutes, the wavelength of the ultraviolet lamp is 365 nm, and the irradiation time is 12 to 48 hours.
[0024] Beneficial effects of the present invention:
[0025] The present invention uses crop straw as raw material, and adopts TiO2 photocatalytic pretreatment method to couple cellulase to jointly promote crop straw saccharification, so that the enzymatic saccharification rate of crop straw can reach 92.82% at best. The present invention also couples and loads metal copper and zinc on TiO2, optimizes the preparation process parameters of the composite TiO2 photocatalyst, and the synthesized composite TiO2 photocatalyst has the advantages of stable chemical properties, high catalytic activity, environmental friendliness and low cost compared with the existing methanol synthesis catalyst. The present invention realizes the ability of reducing sugar to selectively generate methanol at normal temperature and pressure through the efficient catalytic ability of the composite TiO2 photocatalyst, and the methanol yield can reach 5.99%.
[0026] The production process for preparing methanol using crop straw as raw material provided by the present invention requires simple equipment, has low energy consumption, and is environmentally friendly, providing new technical support for promoting clean, low-carbon and efficient utilization of energy, promoting clean energy low-carbon transformation, and biomass resource conversion. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 This is a comparison chart of methanol yields obtained by catalysis of different composite TiO2 photocatalysts in Examples 3 to 6. DETAILED DESCRIPTION
[0028] The technical solution of the present invention is further described below in conjunction with the embodiments, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the protection scope of the present invention. The process equipment or devices not specifically noted in the following embodiments are all conventional equipment or devices in the art. If not specifically specified, the raw materials used in the embodiments of the present invention can be obtained commercially; if not specifically specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.
[0029] Example 1
[0030] This embodiment provides a method for enhancing the saccharification of straw to produce methanol by coupling titanium dioxide photocatalysis with enzymes, and the specific steps are as follows:
[0031] Step 1: Straw pretreatment:
[0032] The corn stalks were crushed into 60 mesh to obtain corn stalk powder, 10 g corn stalk powder was added into 1000 mL deionized water, and the mixture was soaked and stirred for 0.5 h, and then 0.5 g TiO2 with a particle size of 20 nm was added. In this embodiment, titanium dioxide P25 was used, and the pH was adjusted to 8 after stirring for 0.5 h. The resulting mixed system was transferred into an ultrasonic and photocatalytic reactor, and first adsorbed for 0.5 h in the dark, and then catalytically reacted for 0.5 h under 365 nm ultraviolet light. After the reaction was completed, titanium dioxide and stalks were separated by a G3 sand core funnel, and the stalks were dried to constant weight to complete the stalk pretreatment;
[0033] Step 2: Enzymatic hydrolysis of cellulose:
[0034] 3 g of pretreated straw was weighed and placed in a 100 mL conical flask, 0.10 mol / L acetic acid-sodium acetate buffer was added to obtain a mixed system with a pH of 4.8, 20,000 U of cellulase was added to the obtained mixed system for enzymolysis, and the enzymatic activity of the cellulase used in this example was 50,000 U / g; enzymolysis was performed at 150 r / min and 30° C. for 72 h; and an enzymolysis solution containing reducing sugars was obtained by filtration. The enzymolysis saccharification rate in this example was 71.98%.
[0035] Step 3: Preparation of composite TiO2 photocatalyst:
[0036] Disperse 3g of TiO2 in 90mL of 10mol / L NaOH alkaline solution, hydrothermally synthesize H-TiO2 at 130℃, rinse with deionized water and dilute nitric acid until neutral, and collect the obtained H-TiO2 sample; take 3g of H-TiO2 sample, add 18g of ammonium chloride solution and 100mL of 50% ethanol solution by volume, heat and reflux for 8h to obtain NH4-TiO2, take 1g of NH4-TiO2 sample, add 7.81mL1mol / L copper nitrate solution and 1.95mL1mol / L zinc chloride solution, the concentration of copper ions in the obtained system is 5wt%, and the concentration of zinc ions is 1.25wt%, stir at room temperature for 12h, collect the solid sample, dry it, and calcine it at 400℃ for 3h to obtain the composite TiO2 photocatalyst CZ-TiO2;
[0037] Step 4: Catalytic reduction of sugar to produce methanol:
[0038] Mix 1 mL of the enzymatic hydrolyzate containing reducing sugars obtained in step 2, 1 mL of water and 8 mL of acetonitrile in proportion, place the obtained mixed solution and 200 mg of the composite TiO2 photocatalyst obtained in step 3 in a photocatalytic reactor, introduce nitrogen for 2 minutes after mixing, and carry out photocatalytic reaction under 365 nm high-pressure ultraviolet lamp for 12 hours to obtain methanol.
[0039] Example 2
[0040] This embodiment provides a method for enhancing the saccharification of straw to produce methanol by coupling titanium dioxide photocatalysis with enzymes, and the specific steps are as follows:
[0041] Step 1: Straw pretreatment:
[0042] The corn stalks were crushed into 60 mesh to obtain corn stalk powder, 10 g corn stalk powder was added into 1000 mL deionized water, and the mixture was soaked and stirred for 1.0 h, and then 2 g TiO2 with a particle size of 20 nm was added. In this embodiment, titanium dioxide P25 was used, and the pH was adjusted to 11 after stirring for 1.0 h. The resulting mixed system was transferred into an ultrasonic and photocatalytic reactor, and first adsorbed for 1.0 h in the dark, and then catalytically reacted for 1.0 h under 365 nm ultraviolet light. After the reaction was completed, titanium dioxide and stalks were separated by a G3 sand core funnel, and the stalks were dried to constant weight to complete the stalk pretreatment;
[0043] Step 2: Enzymatic hydrolysis of cellulose:
[0044] 3 g of pretreated straw was weighed and placed in a 100 mL conical flask, 0.10 mol / L acetic acid-sodium acetate buffer was added to obtain a mixed system with a pH of 4.8, 20,000 U of cellulase was added to the obtained mixed system for enzymolysis, and the enzymatic activity of the cellulase used in this example was 50,000 U / g; enzymolysis was performed at 150 r / min and 60° C. for 24 h; and an enzymolysis solution containing reducing sugars was obtained by filtration. The enzymolysis saccharification rate in this example was 62.15%.
[0045] Step 3: Preparation of composite TiO2 photocatalyst:
[0046] Disperse 3g of TiO2 in 90mL of 10mol / L NaOH alkaline solution, hydrothermally synthesize H-TiO2 at 180℃, rinse with deionized water and dilute nitric acid until neutral, and collect the obtained H-TiO2 sample; take 3g of H-TiO2 sample, add 18g of ammonium chloride solution and 100mL of 50% ethanol solution by volume, heat and reflux for 20h to obtain NH4-TiO2, take 1g of NH4-TiO2 sample, add 7.81mL1mol / L copper nitrate solution and 1.95mL1mol / L zinc chloride solution, the concentration of copper ions in the obtained system is 5wt%, and the concentration of zinc ions is 1.25wt%, after stirring at room temperature for 24h, collect the solid sample and dry it, and calcine it at 600℃ for 1h to obtain the composite TiO2 photocatalyst CZ-TiO2;
[0047] Step 4: Catalytic reduction of sugar to produce methanol:
[0048] Mix 1 mL of the enzymatic hydrolyzate containing reducing sugars obtained in step 2, 1 mL of water and 8 mL of acetonitrile in proportion, place the obtained mixed solution and 200 mg of the composite TiO2 photocatalyst obtained in step 3 in a photocatalytic reactor, introduce nitrogen for 3 minutes after mixing, and carry out photocatalytic reaction under 365 nm high-pressure ultraviolet lamp for 48 hours to obtain methanol.
[0049] Example 3
[0050] This embodiment provides a method for enhancing the saccharification of straw to produce methanol by coupling titanium dioxide photocatalysis with enzymes, and the specific steps are as follows:
[0051] Step 1: Straw pretreatment:
[0052] The corn stalks were crushed into 60 mesh to obtain corn stalk powder, 10 g corn stalk powder was added into 1000 mL deionized water, soaked and stirred for 1.5 h, and then 1 g TiO2 with a particle size of 20 nm was added. In this embodiment, titanium dioxide P25 was used, and the pH was adjusted to 10 after stirring for 1.5 h. The resulting mixed system was transferred into an ultrasonic and photocatalytic reactor, first adsorbed for 1.5 h in the dark, and then catalytically reacted for 1.5 h under 365 nm ultraviolet light. After the reaction was completed, titanium dioxide and stalks were separated by a G3 sand core funnel, and the stalks were dried to constant weight to complete the stalk pretreatment;
[0053] Step 2: Enzymatic hydrolysis of cellulose:
[0054] 3 g of pretreated straw was weighed and placed in a 100 mL conical flask, 0.10 mol / L acetic acid-sodium acetate buffer was added to obtain a mixed system with a pH of 4.8, 20,000 U of cellulase was added to the obtained mixed system for enzymolysis, and the enzymatic activity of the cellulase used in this example was 50,000 U / g; enzymolysis was performed at 150 r / min and 50° C. for 48 h; and an enzymolysis solution containing reducing sugars was obtained by filtration. The enzymolysis saccharification rate in this example was 92.82%.
[0055] Step 3: Preparation of composite TiO2 photocatalyst:
[0056] Disperse 3g of TiO2 in 90mL of 10mol / L NaOH alkaline solution, hydrothermally synthesize H-TiO2 at 150℃, rinse with deionized water and dilute nitric acid until neutral, and collect the obtained H-TiO2 sample; take 3g of H-TiO2 sample, add 18g of ammonium chloride solution and 100mL of 50% ethanol solution by volume, heat and reflux for 12h to obtain NH4-TiO2, take 1g of NH4-TiO2 sample, add 7.81mL of 1mol / L copper nitrate solution and 1.95mL of 1mol / L zinc chloride solution, the concentration of copper ions in the obtained system is 5wt%, and the concentration of zinc ions is 1.25wt%, after stirring at room temperature for 24h, collect the solid sample and dry it, and calcine it at 500℃ for 2h to obtain the composite TiO2 photocatalyst CZ-TiO2;
[0057] Step 4: Catalytic reduction of sugar to produce methanol:
[0058] 1 mL of the enzymatic hydrolyzate containing reducing sugar obtained in step 2, 1 mL of water and 8 mL of acetonitrile were mixed in proportion, and the obtained mixed solution and 200 mg of the composite TiO2 photocatalyst obtained in step 3 were placed in a photocatalytic reactor, and nitrogen was introduced for 2 minutes after mixing, and photocatalytic reaction was carried out under 365 nm high-pressure ultraviolet light for 24 hours to obtain methanol. The methanol yield of this example is 4.37%.
[0059] Example 4
[0060] This embodiment provides a method for enhancing the saccharification of straw to produce methanol by coupling titanium dioxide photocatalysis with enzymes, and the specific steps are as follows:
[0061] Step 1: Straw pretreatment:
[0062] The corn stalks were crushed into 60 mesh to obtain corn stalk powder, 10 g corn stalk powder was added into 1000 mL deionized water, soaked and stirred for 1.5 h, and then 1 g TiO2 with a particle size of 20 nm was added. In this embodiment, titanium dioxide P25 was used, and the pH was adjusted to 10 after stirring for 1.5 h. The resulting mixed system was transferred into an ultrasonic and photocatalytic reactor, first adsorbed for 1.5 h in the dark, and then catalytically reacted for 1.5 h under 365 nm ultraviolet light. After the reaction was completed, titanium dioxide and stalks were separated by a G3 sand core funnel, and the stalks were dried to constant weight to complete the stalk pretreatment;
[0063] Step 2: Enzymatic hydrolysis of cellulose:
[0064] Weigh 3 g of pretreated straw and put it into a 100 mL conical flask, add 0.10 mol / L acetic acid-sodium acetate buffer to obtain a mixed system with a pH of 4.8, add 20000 U of cellulase to the obtained mixed system for enzymolysis, and the enzymatic activity of the cellulase used in this example is 50000 U / g; enzymolysis is carried out at 150 r / min and 50° C. for 48 h; filter to obtain an enzymolysis solution containing reducing sugars;
[0065] Step 3: Preparation of composite TiO2 photocatalyst:
[0066] Disperse 3g of TiO2 in 90mL of 10mol / L NaOH alkaline solution, hydrothermally synthesize H-TiO2 at 150℃, rinse with deionized water and dilute nitric acid until neutral, and collect the obtained H-TiO2 sample; take 3g of H-TiO2 sample, add 18g of ammonium chloride solution and 100mL of 50% ethanol solution by volume, heat and reflux for 12h to obtain NH4-TiO2, take 1g of NH4-TiO2 sample, add 7.81mL1mol / L copper nitrate solution and 3.91mL1mol / L zinc chloride solution, the concentration of copper ions in the obtained system is 5wt%, and the concentration of zinc ions is 2.5wt%, after stirring at room temperature for 24h, collect the solid sample and dry it, and calcine it at 500℃ for 2h to obtain the composite TiO2 photocatalyst CZ-TiO2;
[0067] Step 4: Catalytic reduction of sugar to produce methanol:
[0068] 1 mL of the enzymatic hydrolyzate containing reducing sugar obtained in step 2, 1 mL of water and 8 mL of acetonitrile were mixed in proportion, and the obtained mixed solution and 200 mg of the composite TiO2 photocatalyst obtained in step 3 were placed in a photocatalytic reactor, and nitrogen was introduced for 2 minutes after mixing, and photocatalytic reaction was carried out under 365 nm high-pressure ultraviolet light for 24 hours to obtain methanol. The methanol yield of this example is 4.69%.
[0069] Example 5
[0070] This embodiment provides a method for enhancing the saccharification of straw to produce methanol by coupling titanium dioxide photocatalysis with enzymes, and the specific steps are as follows:
[0071] Step 1: Straw pretreatment:
[0072] The corn stalks were crushed into 60 mesh to obtain corn stalk powder, 10 g corn stalk powder was added into 1000 mL deionized water, soaked and stirred for 1.5 h, and then 1 g TiO2 with a particle size of 20 nm was added. In this embodiment, titanium dioxide P25 was used, and the pH was adjusted to 10 after stirring for 1.5 h. The resulting mixed system was transferred into an ultrasonic and photocatalytic reactor, first adsorbed for 1.5 h in the dark, and then catalytically reacted for 1.5 h under 365 nm ultraviolet light. After the reaction was completed, titanium dioxide and stalks were separated by a G3 sand core funnel, and the stalks were dried to constant weight to complete the stalk pretreatment;
[0073] Step 2: Enzymatic hydrolysis of cellulose:
[0074] Weigh 3 g of pretreated straw and put it into a 100 mL conical flask, add 0.10 mol / L acetic acid-sodium acetate buffer to obtain a mixed system with a pH of 4.8, add 20000 U of cellulase to the obtained mixed system for enzymolysis, and the enzymatic activity of the cellulase used in this example is 50000 U / g; enzymolysis is carried out at 150 r / min and 50° C. for 48 h; filter to obtain an enzymolysis solution containing reducing sugars;
[0075] Step 3: Preparation of composite TiO2 photocatalyst:
[0076] Disperse 3g of TiO2 in 90mL of 10mol / L NaOH alkaline solution, hydrothermally synthesize H-TiO2 at 150℃, rinse with deionized water and dilute nitric acid until neutral, and collect the obtained H-TiO2 sample; take 3g of H-TiO2 sample, add 18g of ammonium chloride solution and 100mL of 50% ethanol solution by volume, heat and reflux for 12h to obtain NH4-TiO2, take 1g of NH4-TiO2 sample, add 7.81mL1mol / L copper nitrate solution and 7.81mL1mol / L zinc chloride solution, the concentration of copper ions in the obtained system is 5wt%, and the concentration of zinc ions is 5wt%, after stirring at room temperature for 24h, collect the solid sample and dry it, and calcine it at 500℃ for 2h to obtain the composite TiO2 photocatalyst CZ-TiO2;
[0077] Step 4: Catalytic reduction of sugar to produce methanol:
[0078] 1 mL of the enzymatic hydrolyzate containing reducing sugar obtained in step 2, 1 mL of water and 8 mL of acetonitrile were mixed in proportion, and the obtained mixed solution and 200 mg of the composite TiO2 photocatalyst obtained in step 3 were placed in a photocatalytic reactor, and nitrogen was introduced for 2 minutes after mixing, and photocatalytic reaction was carried out under 365 nm high-pressure ultraviolet light for 24 hours to obtain methanol. The methanol yield of this example is 5.99%.
[0079] Example 6
[0080] This embodiment provides a method for enhancing the saccharification of straw to produce methanol by coupling titanium dioxide photocatalysis with enzymes, and the specific steps are as follows:
[0081] Step 1: Straw pretreatment:
[0082] The corn stalks were crushed into 60 mesh to obtain corn stalk powder, 10 g corn stalk powder was added into 1000 mL deionized water, soaked and stirred for 1.5 h, and then 1 g TiO2 with a particle size of 20 nm was added. In this embodiment, titanium dioxide P25 was used, and the pH was adjusted to 10 after stirring for 1.5 h. The resulting mixed system was transferred into an ultrasonic and photocatalytic reactor, first adsorbed for 1.5 h in the dark, and then catalytically reacted for 1.5 h under 365 nm ultraviolet light. After the reaction was completed, titanium dioxide and stalks were separated by a G3 sand core funnel, and the stalks were dried to constant weight to complete the stalk pretreatment;
[0083] Step 2: Enzymatic hydrolysis of cellulose:
[0084] Weigh 3 g of pretreated straw and put it into a 100 mL conical flask, add 0.10 mol / L acetic acid-sodium acetate buffer to obtain a mixed system with a pH of 4.8, add 20000 U of cellulase to the obtained mixed system for enzymolysis, and the enzymatic activity of the cellulase used in this example is 50000 U / g; enzymolysis is carried out at 150 r / min and 50° C. for 48 h; filter to obtain an enzymolysis solution containing reducing sugars;
[0085] Step 3: Preparation of composite TiO2 photocatalyst:
[0086] Disperse 3g of TiO2 in 90mL of 10mol / L NaOH alkaline solution, hydrothermally synthesize H-TiO2 at 150℃, rinse with deionized water and dilute nitric acid until neutral, and collect the obtained H-TiO2 sample; take 3g of H-TiO2 sample, add 18g of ammonium chloride solution and 100mL of 50% ethanol solution by volume, heat and reflux for 12h to obtain NH4-TiO2, take 1g of NH4-TiO2 sample, add 7.81mL1mol / L copper nitrate solution and 11.73mL1mol / L zinc chloride solution, the concentration of copper ions in the obtained system is 5wt%, and the concentration of zinc ions is 7.25wt%, after stirring at room temperature for 24h, collect the solid sample and dry it, and calcine it at 500℃ for 2h to obtain the composite TiO2 photocatalyst CZ-TiO2;
[0087] Step 4: Catalytic reduction of sugar to produce methanol:
[0088] 1 mL of the enzymatic hydrolyzate containing reducing sugar obtained in step 2, 1 mL of water and 8 mL of acetonitrile were mixed in proportion, and the obtained mixed solution and 200 mg of the composite TiO2 photocatalyst obtained in step 3 were placed in a photocatalytic reactor, and nitrogen was introduced for 2 minutes after mixing, and photocatalytic reaction was carried out under 365 nm high-pressure ultraviolet light for 24 hours to obtain methanol. The methanol yield of this example is 5.86%.
Claims
1. A method for enhancing straw saccharification and methanol production by titanium dioxide photocatalysis coupled with enzyme, characterized in that: The steps include: Step 1: Straw pretreatment: The straw powder is placed in deionized water and stirred for a period of time, and then TiO2 is added. After stirring for a certain period of time, the pH is adjusted to alkaline, and the resulting mixed system is transferred to an ultrasonic and photocatalytic reactor, first adsorbed in the dark, and then the catalytic reaction is completed under ultraviolet light. After the reaction is completed, titanium dioxide and straw are separated, and the straw is dried to constant weight to complete the straw pretreatment; Step 2: Enzymatic hydrolysis of cellulose: Adding acetic acid-sodium acetate buffer to the pretreated straw obtained in step 1, adding cellulase to the obtained mixed system for enzymolysis, and filtering to obtain an enzymolysis solution containing reducing sugars; Step 3: Preparation of composite TiO2 photocatalyst: A certain amount of TiO2 is dispersed in an alkaline solution, H-TiO2 is synthesized by hydrothermal method, and the solution is washed with deionized water and dilute nitric acid until neutral. The obtained H-TiO2 sample is collected and a certain amount of ammonium chloride and ethanol solution are added, and the solution is heated under reflux to obtain NH4-TiO2. The NH4-TiO2 sample is collected, a certain amount of NH4-TiO2 is added with a certain amount of copper nitrate solution and zinc chloride solution, and the solid sample is collected after stirring at room temperature for a certain period of time, and then dried and calcined to obtain a composite TiO2 photocatalyst CZ-TiO2. Step 4: Catalytic reduction of sugar to produce methanol: The enzymatic hydrolyzate containing reducing sugars obtained in step 2, water and acetonitrile are mixed in proportion to obtain a mixed solution and the composite TiO2 photocatalyst obtained in step 3 are placed in a photocatalytic reactor, nitrogen is introduced after mixing, and a photocatalytic reaction is carried out under the irradiation of a high-pressure ultraviolet lamp to obtain methanol.
2. The method of titanium dioxide photocatalysis coupled with enzyme to enhance straw saccharification and methanol production according to claim 1, characterized in that: Step 1: The particle size of the straw powder is 60 mesh, the mass volume ratio of the straw powder to deionized water is 10g:500-1000mL, and the time for soaking and stirring the straw powder in deionized water is 0.5-1.5h.
3. The method for enhancing straw saccharification and methanol production by titanium dioxide photocatalysis coupled with enzyme according to claim 1 or 2, characterized in that: Step 1: The particle size of TiO2 is 20 nm, and the amount of TiO2 added is calculated based on the mass ratio of straw powder to TiO2 of 10:0.5-2. The stirring time after adding TiO2 is 0.5-1.5 h, and the pH is adjusted to an alkaline pH value of 8-11.
4. The method of titanium dioxide photocatalysis coupled with enzyme to enhance straw saccharification and methanol production according to claim 3, characterized in that: In step 1, the adsorption time under dark conditions is 0.5 to 1.5 hours, the catalytic reaction time under ultraviolet light is 0.5 to 1.5 hours, and the wavelength of the ultraviolet light is 365 nm.
5. The method for enhancing straw saccharification and methanol production by titanium dioxide photocatalysis coupled with enzyme according to claim 4, characterized in that: In step 2, the concentration of the acetic acid-sodium acetate buffer is 0.10 mol / L, and the pH is 4.0-7.0; the amount of the cellulase added is calculated based on the mass ratio of the pretreated straw to the cellulase of 0.2-5 g:20000 U, and the enzymatic activity of the cellulase is 50000 U / g; the reaction conditions of the enzymolysis are enzymolysis at 150 r / min and 30-60° C. for 24-72 h.
6. The method of titanium dioxide photocatalysis coupled with enzyme to enhance straw saccharification and methanol production according to claim 5, characterized in that: In step 3, the alkaline solution is a NaOH solution with a concentration of 10 mol / L, the mass volume ratio of TiO2 to the alkaline solution is 0.5-3 g:90 mL, and the temperature of the hydrothermal synthesis is 130-180°C.
7. The method of titanium dioxide photocatalysis coupled with enzyme to enhance straw saccharification and methanol production according to claim 6, characterized in that: Step 3: The mass volume ratio of the H-TiO2 sample, ammonium chloride and ethanol solution is 1-5g:5-30g:100mL, and the volume concentration of the ethanol solution is 50%; the heating reflux time is 8-20h.
8. The method of titanium dioxide photocatalysis coupled with enzyme to enhance straw saccharification and methanol production according to claim 7, characterized in that: Step 3: The concentrations of the copper nitrate solution and the zinc chloride solution are both 1 mol / L, and the mass volume ratio of the NH4-TiO2 sample, the copper nitrate solution and the zinc chloride solution is 0.5-5 g:7.81 mL:1-30 mL; the concentration of copper ions in the obtained reaction system is 5 wt%, the concentration of zinc ions is 1.25-7.25 wt%, the stirring time at room temperature is 12-36 h, and the calcination is calcined at 400-600 ° C for 1-3 h.
9. The method of titanium dioxide photocatalysis coupled with enzyme to enhance straw saccharification and methanol production according to claim 8, characterized in that: In step 4, the volume ratio of the enzymatic hydrolyzate containing reducing sugars, water and acetonitrile in the mixed solution is 1:1:8, and the volume mass ratio of the mixed solution to the composite TiO2 photocatalyst is 10mL:100-300mg.
10. The method for enhancing straw saccharification and methanol production by titanium dioxide photocatalysis coupled with enzyme according to claim 9, characterized in that: In step 4, the nitrogen introduction time is 1 to 3 minutes, the wavelength of the ultraviolet lamp is 365 nm, and the irradiation time is 12 to 48 hours.