Perovskite catalyst for lignin degradation and preparation method thereof

Abstract

The application discloses a perovskite catalyst for lignin degradation and a preparation method thereof. Para-carboxybenzaldehyde and pyrrole are used as raw materials to obtain symmetrical porphyrin, then KH550 is added to make the amino group on the KH550 and the carboxyl group on the substrate dehydrate and condense to obtain an intermediate 1, the intermediate 1 is reacted with cobalt chloride hexahydrate to form a metal complex, then modified perovskite matrix and deionized water are added, and the siloxane on the metal complex is hydrolyzed and grafted on the surface of the modified perovskite matrix to obtain the perovskite catalyst. The perovskite catalyst has higher stability due to the multilayer coating. When the perovskite catalyst is irradiated to form an oxidation-reduction system of an electron-hole pair, the oxidant adsorbed on the catalyst is changed into a free radical to act on the lignin substrate, so that the lignin is degraded. The surface metal porphyrin can increase the redox potential of the catalyst, so that the catalyst has a smaller dosage compared with a traditional catalyst.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lignin degradation, and particularly relates to a perovskite catalyst for lignin degradation and a preparation method thereof. BACKGROUND

[0002] There is great potential for the production of liquid fuels and high value-added chemical products from lignocellulosic resources which are widely distributed, have large reserves, are renewable, inexpensive and low-polluting. Lignocellulose mainly has three parts, namely cellulose, hemicellulose and lignin. Cellulose and hemicellulose are sugar molecules connected by glycosidic bonds, and by breaking the glycosidic bonds, they can be degraded and converted into sugar platform compounds, which can be further converted into chemicals or liquid alkanes by hydrodeoxygenation. Lignin accounts for 20%-30% of the total weight of plant skeleton, second only to cellulose. However, the chemical structure of lignin is complex, and it has a three-dimensional network irregular structure, so it is difficult to use lignin to prepare chemical products or fuels. Therefore, finding a catalyst with excellent performance to catalytically degrade lignin is the key to efficient utilization of lignin. SUMMARY

[0003] The present application aims to provide a perovskite catalyst for lignin degradation and a preparation method thereof, which solves the problems of low degradation efficiency and high dosage of the perovskite catalyst at the present stage.

[0004] The object of the present application can be achieved by the following technical solutions.

[0005] A preparation method of a perovskite catalyst for lignin degradation, specifically comprising the following steps:

[0006] Step S1: uniformly mix p-carboxybenzaldehyde and propionic acid, reflux under the condition of a rotation speed of 150-200 r / min and a temperature of 140-145 DEG C, and add pyrrole to react for 30-40 min, cool to room temperature, add deionized water and methanol, and stand for 10-15 h, filter to remove the filtrate, uniformly mix the substrate, KH550, 1-hydroxybenzotriazole and tetrahydrofuran under the condition of a rotation speed of 200-300 r / min and a temperature of 25-30 DEG C, and react for 3-5 h to prepare an intermediate 1;

[0007] Step S2: add the intermediate 1 into DMF, stir and reflux under the condition of a rotation speed of 150-200 r / min and a temperature of 155-160 DEG C, and add cobalt chloride hexahydrate to stir for 30-40 min, then cool to 60-70 DEG C, add a modified perovskite matrix and deionized water, and continue to stir for 1-1.5 h, filter to remove the filtrate, and dry the filter cake to prepare the perovskite catalyst.

[0008] Further, the carboxyl benzaldehyde, propionic acid, pyrrole, deionized water and methanol in step S1 are used in a ratio of 70 mmol: 100 mL: 3 mL: 40 mL: 40 mL, and the molar ratio of the substrate, KH550, 1-hydroxybenzotriazole is 1:1:1.1.

[0009] Further, the intermediate 1, DMF, cobalt chloride hexahydrate, modified perovskite matrix and deionized water in step S2 are used in a ratio of 0.15 g: 20 mL: 0.5 g: 1 g: 10 mL.

[0010] Further, the modified perovskite matrix is prepared by the following steps:

[0011] Step A1: The wheat straw is crushed into small pieces of 2-3 mm, compacted to fill a dry pot, and placed in a muffle furnace at a temperature of 300-350°C for carbonization for 4-5h. Then, the potassium hydroxide solution is added, and stirred at a speed of 300-500r / min for 2-3h. After filtration and drying, the porous matrix is prepared by washing with sulfuric acid solution for 1-1.5h, and then washing with deionized water until neutral;

[0012] Step A2: The lanthanum nitrate hexahydrate, cerium nitrate hexahydrate and deionized water are mixed uniformly to prepare a metal ion solution. Citric acid and ethylene glycol are added to the metal ion solution, and ammonia water is added to adjust the pH value to 6-8. The gel is formed by stirring at a speed of 200-300r / min and a temperature of 90-95°C. The catalytic matrix is prepared by drying the gel at a temperature of 200-250°C, and then sintering in a muffle furnace at a temperature of 1000-1050°C for 10-12h;

[0013] Step A3: The porous matrix, catalytic matrix and ethanol are mixed, and then ultrasonic treated at a power of 100-120W for 10-15min. Then, the tetraethyl orthosilicate is added, and stirred at a speed of 300-500r / min and a temperature of 20-25°C. After stirring for 30-40min, the filtrate is removed by filtration. The substrate is dried to prepare the modified perovskite matrix.

[0014] Further, the mass ratio of the wheat straw and potassium hydroxide in step A1 is 1:4, the concentration of the potassium hydroxide solution is 6mol / L, and the concentration of the sulfuric acid solution is 0.5mol / L.

[0015] Further, the use amount ratio of the lanthanum nitrate hexahydrate, cerium nitrate hexahydrate and deionized water in step A2 is 100 mmol: 100 mmol: 1 L, and the use amount ratio of the citric acid, ethylene glycol and metal ion solution is 12.5 mmol: 12.5 mmol: 1 L.

[0016] Further, the use amount ratio of the porous matrix, catalytic matrix, ethanol, tetraethyl orthosilicate, concentrated hydrochloric acid and deionized water in step A3 is 3 g: 1 g: 10 mL: 0.63 g: 0.11 g: 50 mL, and the concentration of the concentrated hydrochloric acid is 12 mol / L.

[0017] The perovskite catalyst for lignin degradation prepared by the method has the following beneficial effects: the perovskite catalyst for lignin degradation is prepared by using p-carboxybenzaldehyde and pyrrole as raw materials to obtain symmetrical porphyrin, then adding KH550, and, under the action of 1-hydroxybenzotriazole, dehydrating and condensing the amino group on the KH550 and the carboxyl group on the substrate to obtain an intermediate 1, reacting the intermediate 1 with cobalt chloride hexahydrate to form a metal complex, and adding a modified perovskite matrix and deionized water, so that the siloxane on the metal complex is hydrolyzed and grafted on the surface of the modified perovskite matrix to obtain the perovskite catalyst. The modified perovskite matrix is prepared by using small-surface wheat straw as raw material, crushing and carbonizing the small-surface wheat straw, activating the small-surface wheat straw with a potassium hydroxide solution, and finally obtaining a porous matrix by acid washing. The metal ion solution is prepared by dissolving lanthanum nitrate hexahydrate and cerium nitrate hexahydrate in deionized water. The citric acid and ethylene glycol are used as complexing agents to form a gel, and then high-temperature calcination is performed to obtain a catalytic matrix. The catalytic matrix and the porous matrix are ultrasonically dispersed, and then a modified perovskite matrix is prepared by silica sol coating and compounding. The perovskite catalyst has higher stability due to the multi-layer coating. When the perovskite catalyst is irradiated, an oxidation-reduction system of an electron-hole pair is formed, the oxidant adsorbed on the catalyst is changed into a free radical, and the free radical acts on the lignin substrate to degrade the lignin. The metal porphyrin on the surface of the catalyst can increase the redox potential of the catalyst, so that the catalyst has a smaller amount of use compared with a traditional catalyst. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0019] Embodiment 1

[0020] A preparation method of a perovskite catalyst for lignin degradation, specifically comprising the following steps:

[0021] Step S1: uniformly mix p-carboxybenzaldehyde and propionic acid, under the condition of 150 r / min rotation speed and 140℃ temperature, reflux and add pyrrole, react for 30 min, cool to room temperature, add deionized water and methanol, stand for 10 h, remove the filtrate by filtration, uniformly mix the substrate, KH550, 1-hydroxybenzotriazole and tetrahydrofuran, under the condition of 200 r / min rotation speed and 25℃ temperature, react for 3 h, to prepare intermediate 1;

[0022] Step S2: add intermediate 1 into DMF, under the condition of 150 r / min rotation speed and 155℃ temperature, stir and reflux, and add cobalt chloride hexahydrate, stir for 30 min, then cool to 60℃, add modified perovskite matrix and deionized water, continue to stir for 1 h, remove the filtrate by filtration, and dry the filter cake to prepare the perovskite catalyst.

[0023] The amount ratio of p-carboxybenzaldehyde, propionic acid, pyrrole, deionized water and methanol in step S1 is 70 mmol:100 mL:3 mL:40 mL:40 mL, and the molar ratio of the substrate, KH550 and 1-hydroxybenzotriazole is 1:1:1.1.

[0024] The amount ratio of intermediate 1, DMF, cobalt chloride hexahydrate, modified perovskite matrix and deionized water in step S2 is 0.15 g:20 mL:0.5 g:1 g:10 mL.

[0025] The modified perovskite matrix is prepared by the following steps:

[0026] Step A1: crush the wheat straw into 2 mm small pieces, compactly fill the dry pot, and put it into the muffle furnace, carbonize for 4 h under the condition of 300℃ temperature, then add potassium hydroxide solution, stir for 2 h under the condition of 300 r / min rotation speed, filter and dry, then heat for 1 h under the condition of 750℃ temperature and nitrogen protection, wash with sulfuric acid solution for 1 h, and then wash with deionized water until neutral, to prepare the porous matrix;

[0027] Step A2: uniformly mix lanthanum nitrate hexahydrate, cerium nitrate hexahydrate and deionized water to prepare a metal ion solution, add citric acid and ethylene glycol to the metal ion solution, and add ammonia water to adjust the pH value to 6, stir to form a gel under the condition of 200 r / min rotation speed and 90℃ temperature, dry the gel under the condition of 200℃ temperature, and then add it into the muffle furnace, sinter for 10 h under the condition of 1000℃ temperature, to prepare the catalytic matrix.

[0028] Step A3: The porous substrate, catalytic substrate and ethanol were mixed, and after ultrasonic treatment for 10 min at a power of 100 W, tetraethyl orthosilicate was added, and stirring was carried out at a rotation speed of 300 r / min and a temperature of 20℃, and concentrated hydrochloric acid and deionized water were added, and after stirring for 30 min, the filtrate was removed by filtration, and the substrate was dried to obtain a modified perovskite substrate.

[0029] The mass ratio of wheat straw to potassium hydroxide in step A1 was 1:4, the concentration of the potassium hydroxide solution was 6 mol / L, and the concentration of the sulfuric acid solution was 0.5 mol / L.

[0030] The amount ratio of lanthanum nitrate hexahydrate, cerium nitrate hexahydrate and deionized water in step A2 was 100 mmol:100 mmol:1 L, and the amount ratio of citric acid, ethylene glycol and metal ion solution was 12.5 mmol:12.5 mmol:1 L.

[0031] The amount ratio of the porous substrate, catalytic substrate, ethanol, tetraethyl orthosilicate, concentrated hydrochloric acid and deionized water in step A3 was 3 g:1 g:10 mL:0.63 g:0.11 g:50 mL, and the concentration of the concentrated hydrochloric acid was 12 mol / L.

[0032] Example 2

[0033] A preparation method of a perovskite catalyst for lignin degradation, specifically comprising the following steps:

[0034] Step S1: The p-carboxybenzaldehyde and propionic acid were mixed uniformly, and refluxing was carried out at a rotation speed of 150 r / min and a temperature of 145℃, and pyrrole was added, and reaction was carried out for 35 min, and the temperature was cooled to room temperature, and deionized water and methanol were added, and the mixture was allowed to stand for 13 h, and the filtrate was removed by filtration, and the substrate, KH550, 1-hydroxybenzotriazole and tetrahydrofuran were mixed uniformly, and reaction was carried out at a rotation speed of 200 r / min and a temperature of 30℃ for 4 h to obtain an intermediate 1.

[0035] Step S2: The intermediate 1 was added to DMF, and stirring refluxing was carried out at a rotation speed of 150 r / min and a temperature of 160℃, and cobalt chloride hexahydrate was added, and after stirring for 35 min, the temperature was lowered to 65℃, and the modified perovskite substrate and deionized water were added, and stirring was continued for 1.5 h, and the filtrate was removed by filtration, and the filter cake was dried to obtain a perovskite catalyst.

[0036] The amount ratio of p-carboxybenzaldehyde, propionic acid, pyrrole, deionized water and methanol in step S1 was 70 mmol:100 mL:3 mL:40 mL:40 mL, and the molar ratio of the substrate, KH550 and 1-hydroxybenzotriazole was 1:1:1.1.

[0037] The intermediate 1, DMF, cobalt chloride hexahydrate, modified perovskite base and deionized water in step S2 are used in a ratio of 0.15 g:20 mL:0.5 g:1 g:10 mL.

[0038] The modified perovskite base is prepared by the following steps:

[0039] Step A1: The wheat straw is crushed into 2mm small pieces, compacted to fill a dry pot, and placed in a muffle furnace. After carbonization at a temperature of 330℃ for 4.5h, the potassium hydroxide solution is added, and stirred at a speed of 300r / min for 2.5h. After filtration and drying, the porous base is prepared by washing with sulfuric acid solution for 1.3h, and then washing with deionized water until neutral.

[0040] Step A2: The lanthanum nitrate hexahydrate, cerium nitrate hexahydrate and deionized water are mixed uniformly to prepare a metal ion solution. Citric acid and ethylene glycol are added to the metal ion solution, and ammonia water is added to adjust the pH value to 7. The gel is formed by stirring at a speed of 200r / min and a temperature of 95℃. The gel is dried at a temperature of 230℃ and then sintered in a muffle furnace at a temperature of 1030℃ for 11h to prepare the catalytic base.

[0041] Step A3: The porous base, catalytic base and ethanol are mixed, and then ultrasonic treated at a power of 110W for 13min. Tetraethyl orthosilicate is added, and stirred at a speed of 300r / min and a temperature of 25℃. Concentrated hydrochloric acid and deionized water are added, and stirred for 35min. After removing the filtrate by filtration, the substrate is dried to prepare the modified perovskite base.

[0042] The mass ratio of the wheat straw to potassium hydroxide in step A1 is 1:4, the concentration of the potassium hydroxide solution is 6mol / L, and the concentration of the sulfuric acid solution is 0.5mol / L.

[0043] The amount ratio of the lanthanum nitrate hexahydrate, cerium nitrate hexahydrate and deionized water in step A2 is 100mmol:100mmol:1L, and the amount ratio of citric acid, ethylene glycol and metal ion solution is 12.5mmol:12.5mmol:1L.

[0044] The amount ratio of the porous base, catalytic base, ethanol, tetraethyl orthosilicate, concentrated hydrochloric acid and deionized water in step A3 is 3g:1g:10mL:0.63g:0.11g:50mL, and the concentration of the concentrated hydrochloric acid is 12mol / L.

[0045] Example 3

[0046] A preparation method of a perovskite catalyst for lignin degradation, specifically comprising the following steps:

[0047] Step S1: uniformly mix p-carboxybenzaldehyde and propionic acid, under the conditions of a rotation speed of 200 r / min and a temperature of 145 DEG C, reflux and add pyrrole, and react for 40 min, cool to room temperature, add deionized water and methanol, stand for 15 h, filter to remove the filtrate, uniformly mix the substrate, KH550, 1-hydroxybenzotriazole and tetrahydrofuran, under the conditions of a rotation speed of 300 r / min and a high temperature of 30 DEG C, and react for 5 h to prepare an intermediate 1;

[0048] Step S2: add the intermediate 1 into DMF, under the conditions of a rotation speed of 200 r / min and a temperature of 160 DEG C, stir and reflux and add cobalt chloride hexahydrate, stir for 40 min, then cool to 70 DEG C, add a modified perovskite matrix and deionized water, continue to stir for 1.5 h, filter to remove the filtrate, and dry the filter cake to prepare the perovskite catalyst.

[0049] The amount ratio of p-carboxybenzaldehyde, propionic acid, pyrrole, deionized water and methanol in step S1 is 70 mmol:100 mL:3 mL:40 mL:40 mL, and the molar ratio of the substrate, KH550 and 1-hydroxybenzotriazole is 1:1:1.1.

[0050] The amount ratio of the intermediate 1, DMF, cobalt chloride hexahydrate, modified perovskite matrix and deionized water in step S2 is 0.15 g:20 mL:0.5 g:1 g:10 mL.

[0051] The modified perovskite matrix is prepared by the following steps:

[0052] Step A1: crush the wheat straw into small pieces of 3 mm, compactly fill a dry pot, and put into a muffle furnace, carbonize under the condition of a temperature of 350 DEG C for 5 h, then add potassium hydroxide solution, stir under the condition of a rotation speed of 500 r / min for 3 h, filter and dry, then heat under the condition of a temperature of 800 DEG C and nitrogen protection for 1.5 h, wash with sulfuric acid solution for 1.5 h, and then wash with deionized water until neutral to prepare a porous matrix;

[0053] Step A2: uniformly mix lanthanum nitrate hexahydrate, cerium nitrate hexahydrate and deionized water to prepare a metal ion solution, add citric acid and ethylene glycol into the metal ion solution, and add ammonia water to adjust the pH value to 8, stir under the condition of a rotation speed of 300 r / min and a temperature of 95 DEG C to form a gel, dry the gel under the condition of a temperature of 250 DEG C, and then put into a muffle furnace, sinter under the condition of a temperature of 1050 DEG C for 12 h to prepare a catalytic matrix;

[0054] Step A3: The porous substrate, catalytic substrate and ethanol were mixed, and after ultrasonic treatment for 15 min at a power of 120 W, tetraethyl orthosilicate was added, and stirring was carried out at a rotation speed of 500 r / min and a temperature of 25 ℃, and concentrated hydrochloric acid and deionized water were added, and after stirring for 40 min, the filtrate was removed by filtration, and the substrate was dried to obtain a modified perovskite substrate.

[0055] The mass ratio of wheat straw to potassium hydroxide in step A1 was 1:4, the concentration of the potassium hydroxide solution was 6 mol / L, and the concentration of the sulfuric acid solution was 0.5 mol / L.

[0056] The amount of use of the lanthanum nitrate hexahydrate, cerium nitrate hexahydrate and deionized water in step A2 was 100 mmol: 100 mmol: 1 L, and the amount of use of the citric acid, ethylene glycol and metal ion solution was 12.5 mmol: 12.5 mmol: 1 L.

[0057] The amount of use of the porous substrate, catalytic substrate, ethanol, tetraethyl orthosilicate, concentrated hydrochloric acid and deionized water in step A3 was 3 g: 1 g: 10 mL: 0.63 g: 0.11 g: 50 mL, and the concentration of the concentrated hydrochloric acid was 12 mol / L.

[0058] Comparative Example 1

[0059] This comparative example uses a catalytic substrate instead of a modified perovskite substrate compared with Example 1, and the remaining steps are the same.

[0060] Comparative Example 2

[0061] This comparative example uses a modified perovskite substrate as a perovskite catalyst compared with Example 1.

[0062] 0.1 g of lignin, 10 mL of 1 mol / L sodium hydroxide solution and 2 mL of isopropyl alcohol were mixed uniformly, 0.01 g of the catalyst prepared in Examples 1-3 and Comparative Examples 1-2 was added respectively to obtain a degradation sample, 1 mL of 30% hydrogen peroxide was added to the sample respectively, and the reaction was carried out under the condition of a temperature of 150 ℃ and irradiation of a 365 nm ultraviolet lamp for 60 min, the filter residue was removed by filtration, 3 mL of 50% sulfuric acid was added to the filtrate, and after standing for 30 min, the filter cake was the undegraded lignin, and the degradation rate was calculated, and the results are shown in the following table.

[0063] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Degradation rate 98.3％ 98.5％ 98.5％ 94.3％ 88.9％

[0064] As shown in the above table, the degradation rate of the catalyst prepared in Examples 1-3 is 98.3-98.5%, which indicates that the present application has a very good degradation effect.

[0065] The above merely illustrates and describes the concept of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or adopt similar ways to replace, as long as the modifications or supplements do not deviate from the concept of the present application or exceed the scope defined by the present claims, and the modifications or supplements shall fall within the protection scope of the present application.

Claims

1. A method for the preparation of a perovskite catalyst for lignin degradation, characterized by: Specifically comprising the following steps: Step S1: mixing p-carboxyl benzaldehyde and propionic acid and refluxing, adding pyrrole, and reacting; cooling to room temperature, adding deionized water and methanol, standing, filtering to remove the filtrate, mixing the substrate, KH550, 1-hydroxybenzotriazole and tetrahydrofuran, and reacting to prepare intermediate 1; Step S2: adding intermediate 1 into DMF, stirring and refluxing under heating, adding cobalt chloride hexahydrate, stirring, cooling, adding modified perovskite matrix and deionized water, and continuing to stir, filtering to remove the filtrate, and drying the filter cake to prepare the perovskite catalyst; The modified perovskite matrix is prepared by the following steps: Step A1: crushing wheat straw into small pieces, filling a dry pot, carbonizing in a muffle furnace, adding potassium hydroxide solution, stirring, filtering and drying, heating and keeping warm, washing with sulfuric acid solution, and washing with deionized water until neutral to prepare a porous matrix; Step A2: mixing lanthanum nitrate hexahydrate, cerium nitrate hexahydrate and deionized water uniformly to prepare a metal ion solution, adding citric acid and ethylene glycol into the metal ion solution, adding ammonia water, stirring to form a gel, drying the gel, and sintering in a muffle furnace to prepare a catalytic matrix; Step A3: mixing the porous matrix, the catalytic matrix and ethanol, ultrasonic treatment, adding tetraethyl orthosilicate, stirring, adding concentrated hydrochloric acid and deionized water, stirring, filtering to remove the filtrate, and drying the substrate to prepare the modified perovskite matrix.

2. The method for preparing a perovskite catalyst for lignin degradation according to claim 1, characterized in that: The amount ratio of p-carboxyl benzaldehyde, propionic acid, pyrrole, deionized water and methanol in step S1 is 70 mmol:100 mL:3 mL:40 mL:40 mL, and the molar ratio of the substrate, KH550 and 1-hydroxybenzotriazole is 1:1:1.

1.

3. The method for preparing a perovskite catalyst for lignin degradation according to claim 1, characterized in that: The amount ratio of intermediate 1, DMF, cobalt chloride hexahydrate, modified perovskite matrix and deionized water in step S2 is 0.15 g:20 mL:0.5 g:1 g:10 mL.

4. The method for preparing a perovskite catalyst for lignin degradation according to claim 1, characterized in that: The mass ratio of wheat straw to potassium hydroxide in step A1 is 1:4, the concentration of potassium hydroxide solution is 6 mol / L, and the concentration of sulfuric acid solution is 0.5 mol / L.

5. The method for preparing a perovskite catalyst for lignin degradation according to claim 1, characterized in that: The amount ratio of lanthanum nitrate hexahydrate, cerium nitrate hexahydrate and deionized water in step A2 is 100 mmol:100 mmol:1 L, and the amount ratio of citric acid, ethylene glycol and metal ion solution is 12.5 mmol:12.5 mmol:1 L.

6. The method for preparing a perovskite catalyst for lignin degradation according to claim 1, characterized in that: The amount ratio of porous matrix, catalytic matrix, ethanol, tetraethyl orthosilicate, concentrated hydrochloric acid and deionized water in step A3 is 3 g:1 g:10 mL:0.63 g:0.11 g:50 mL, and the concentration of concentrated hydrochloric acid is 12 mol / L.

7. A perovskite catalyst for lignin degradation, characterized by: Prepared according to the preparation method of any one of claims 1-6. Prepared according to the preparation method of any one of claims 1-6.