A catalyst for CO2 capture and conversion coupling with biomass oxidation, a preparation method therefor and an application thereof

Abstract

The present invention discloses a catalyst for in-situ CO2 capture and coupling reduction with biomass oxidation, a preparation method therefor and an application thereof. The catalyst is applied to the coupling reaction of photocatalytic CO2 reduction and biomass oxidation. The preparation of the catalyst is to synthesize layered double hydroxides (LDHs) containing CO32− between layers by using coprecipitation method, hydrothermal method, sol-gel method and the like, wherein the chemical formula is [M1-x2+Mx3+(OH)2]x+(An−)x/n.Math.mH2O, which has a thickness of 20-30 nm and an average particle diameter of 60-90 nm. Then metal ion vacancy defects are produced on LDHs laminate by using a NaOH/KOH selective etching to obtain the corresponding catalyst. The catalyst is used in photocatalytic reaction, characterized in that CO32− is continuously consumed in the reaction process, and the catalyst can absorb CO2 in the air for recovery after the reaction, and can be repeatedly used to continuously consume CO2 in the air, thus realizing the direct capture and effective utilization of CO2.

Claims

1. A preparation method of a catalyst for CO.sub.2 capture and conversion coupling with biomass oxidation, characterized in that the preparation method comprises the following steps: A. Dissolve soluble metal salts M.sup.2+ and M.sup.3+ in deionized water to prepare a solution A, wherein the molar ratio of M.sup.2+:M.sup.3+ is 2-4:1, and the anion is CO.sub.3.sup.2−; the total concentration of M.sup.2+ and M.sup.3+ ions is 0.16-0.20 mol/L; M.sup.2+ is one of Zn.sup.2+, Co.sup.2+, Ni.sup.2+ and Cu.sup.2+; M.sup.3+ is one of Al.sup.3+, Fe.sup.3+ and Ga.sup.3+; B. Dissolve alkali and carbonate in deionized water to prepare a precipitant solution B, wherein the concentration of alkali solution is 0.1-0.2 mol/L and the concentration of carbonate is 0.25-0.35 mol/L; said alkali is NaOH or KOH, and said carbonate is Na.sub.2CO.sub.3 or K.sub.2CO.sub.3. C. Drop equal volumes of solution A and solution B into the reactor at the same time, keep the pH of the solution at 9-11, and stir at 400-600 r/min to obtain LDHs suspension; age in a 60-80° C. water bath for 12-18 h, wash and centrifuge the suspension until neutral; dry at 50-60° C. for 12-24 h, take it out and grind it to obtain powdered LDHs, whose chemical formula is [M.sub.1-x.sup.2+M.sub.x.sup.3+(OH).sub.2].sup.x+(A.sup.n−).sub.x/n.Math.mH.sub.2O; the thickness is 20-30 nm; D. Prepare the etching solution by adding LDHs powder into the etching solution so that the LDHs content in the solution is 2.3-2.8 mg/ml; etch for 1-2 h, centrifuge and wash the solution until neutral, and dry for 12-24 h at 50-60° C. to obtain a catalyst with defect points; Said etching solution is KOH or NaOH solution with the concentration of 1-2 mol/L.

2. A preparation method of a catalyst for CO.sub.2 capture and conversion coupling with biomass oxidation according to claim 1, characterized in that the hydrotalcite prepared in step C is one of CuCoAl-LDHs, CuCoFe-LDHs, ZnCoFe-LDHs and CuZnGa-LDHs.

3. A catalyst for CO.sub.2 capture and conversion coupling with biomass oxidation prepared by the method according to claim 1, characterized in that the chemical expression is: CO.sub.3.sup.2−-M.sup.2+M.sup.3+-LDHs, wherein M.sup.2+ is one of Zn.sup.2+, Co.sup.2+, Ni.sup.2+, and Cu.sup.2+; M.sup.3+ is one of Al.sup.3+, Fe.sup.3+ and Ga.sup.3+; the molar ratio of M.sup.2+ to M.sup.3+ is 2-4:1; the catalyst has a two-dimensional layered structure, metal ion vacancy defects are arranged on the laminate, and there are abundant CO.sub.3.sup.2− between layers.

4. An application of the catalyst for CO.sub.2 capture and conversion coupling with biomass oxidation according to claim 3, wherein the catalyst is used in the photocatalytic reaction, characterized in that CO.sub.3.sup.2− is continuously consumed in the reaction process, and the catalyst can absorb CO.sub.2 in the air to recover after the reaction, and can be repeatedly used to continuously consume CO.sub.2 in the air.

5. An application of the catalyst for CO.sub.2 capture and conversion coupling with biomass oxidation according to claim 4, characterized in that it is applied according to the following steps: (1) Disperse CO.sub.3.sup.2−-M.sup.2+M.sup.3+-LDHs catalyst and biomass into acetonitrile or water to prepare a reaction solution, wherein the catalyst concentration is 0.5-1 mg/mL and the biomass concentration is 1.5-2 mg/mL; place the reaction solution in a top-illuminated stainless steel high-pressure photocatalytic reactor, replace the air in the reactor with inert gas, control the pressure at 0.1-0.6 MPa, and irradiate it with a visible light source to make it react; Said biomass is one of 3-hydroxybutyrolactone, glycerol, sorbitol, xylitol and 5-HMF; (2) Take out the reaction solution after 5-6 h of reaction, place it in the air and stir it at room temperature to have the catalyst recover for 12-24 h, so that the catalyst interlayer is in full contact with the air, and absorb CO.sub.2 in the air to convert it into interlayer CO.sub.3.sup.2− to achieve the purpose of capturing CO.sub.2 in the air. The reaction between catalyst laminates is
CO.sub.2+2OH.sup.−═CO.sub.3.sup.2−+H.sub.2O Use the recovered photocatalyst for the reaction in step (1) for a plurality of times until the biomass conversion rate is close to 100%, centrifuge the reaction solution from the catalyst, and separate the product from the solvent by a distillation method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 shows the XRD diffraction pattern of CuCoAl-LDHs prepared in embodiment 1 before and after etching, wherein a is the unetched CuCoAl-LDHs, and b is the etched CuCoAl-LDHs.

[0039] FIG. 2 shows the scanning electron microscope (SEM) photograph of CuCoAl-LDHs prepared in embodiment 1 before and after etching, wherein a is unetched CuCoAl-LDHs, and b is etched CuCoAl-LDHs.

[0040] FIG. 3 shows the solid UV diffuse reflection spectrum of CuCoAl-LDHs prepared in embodiment 1 before and after etching, wherein a is the unetched CuCoAl-LDHs, and b is the etched CuCoAl-LDHs.

[0041] FIG. 4 shows the energy band positions of the catalyst prepared in embodiment 1.

[0042] FIG. 5 shows the catalytic performance of CuCoAl-LDHs prepared in embodiment 1 before and after etching according to the conditions of the application example, wherein a is unetched CuCoAl-LDHs, and b is etched CuCoAl-LDHs.

[0043] FIG. 6 shows the yield of the catalyst prepared in embodiment 1 for 6 hours after photocatalytic oxidation of 5-HMF oxidation according to the conditions of the application example.

[0044] FIG. 7 shows the cumulative yield of the catalyst prepared in embodiment 1 for 30 hours after repeated use of photocatalytic 5-HMF according to the conditions of the application example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment 1

[0045] A: Weigh 0.002 mol of Cu(NO.sub.3).sub.2.Math.6H.sub.2O solid, 0.01 mol of Co(NO.sub.3).sub.2.Math.6H.sub.2O solid, and 0.006 mol of Al(NO.sub.3).sub.3.Math.9H.sub.2O solid and dissolve them in a beaker containing 100 mL of deionized water.

[0046] B: Weigh 0.03 mol of anhydrous Na.sub.2CO.sub.3 solid and 0.015 mol of NaOH solid and dissolve them in a beaker containing 100 mL of deionized water.

[0047] C: Add 100 mL of deionized water into the three-necked flask, and titrate the two liquid solutions in Steps A and B into the flask at the same titration rate, keeping the pH in the titration process within the range of 9-11. After the dropwise addition, place the three-necked flask in a 60° C. water bath for crystallization for 12 hours, followed by centrifugating, washing, drying and grinding to obtain CuCoAl-LDHs.

[0048] D: Take 0.1 g of CuCoAl-LDHs sample, add 40 mL of 1 mol/L KOH solution and have it etched in a 60° C. water bath for 1 hour, followed by centrifugating, washing to neutrality, drying and grinding to obtain catalyst CuCoAl-LDHs with defect points.

Embodiment 2

[0049] A: Weigh 0.002 mol of Cu(NO.sub.3).sub.2.Math.6H.sub.2O solid, 0.01 mol of Co(NO.sub.3).sub.2.Math.6H.sub.2O solid, and 0.006 mol of Fe(NO.sub.3).sub.3.Math.9H.sub.2O solid. Dissolve the three salts in a beaker containing 100 mL of deionized water.

[0050] B: Weigh 0.03 mol of anhydrous Na.sub.2CO.sub.3 solid and 0.015 mol of NaOH solid and dissolve them in a beaker containing 100 mL of deionized water.

[0051] C: Add 100 mL of deionized water into the three-necked flask, and titrate the two liquid solutions in Steps A and B into the flask at the same titration rate, keeping the pH in the titration process within the range of 9-11, and then have the solution crystallize in a water bath at 60° C. for 12 hours, followed by centrifuging, washing, drying and grinding to obtain CuCoFe-LDHs.

[0052] D: Take 0.1 g of CuCoFe-LDHs sample, add 40 mL of 1 mol/L KOH solution and have it etched in a 60° C. water bath for 1 hour, followed by centrifugating, washing to neutrality, drying and grinding to obtain photocatalyst CuCoFe-LDHs with high catalytic performance.

Embodiment 3

[0053] A: Weigh 0.002 mol of Zn(NO.sub.3).sub.2.Math.6H.sub.2O solid, 0.01 mol of Co(NO.sub.3).sub.2.Math.6H.sub.2O solid, and 0.006 mol of Fe(NO.sub.3).sub.3.Math.9H.sub.2O solid. Dissolve the three salts in a beaker containing 100 mL of deionized water.

[0054] B: Weigh 0.03 mol of anhydrous Na.sub.2CO.sub.3 solid and 0.015 mol of NaOH solid and dissolve them in a beaker containing 100 mL of deionized water.

[0055] C: Synthesize ZnCoFe-LDHs by coprecipitation method; add 100 mL of deionized water into the three-necked flask, and titrate the two liquid solutions in Steps A and B into the 500 mL flask at the same titration rate, keeping the pH in the titration process within the range of 9-11, and then have the solution crystallize in a water bath at 60° C. for 12 hours, followed by centrifuging, washing, drying and grinding to obtain ZnCoFe-LDHs.

[0056] D: Take 0.2 g of ZnCoFe-LDHs sample, add 40 mL of 2 mol/L KOH solution and have it etched in a 60° C. water bath for 2 hours, followed by centrifugating, washing to neutrality, drying and grinding to obtain photocatalyst with high catalytic performance.

[0057] Application of Catalyst

Embodiment 4

[0058] A: Weigh 0.002 mol of Cu(NO.sub.3).sub.2.Math.6H.sub.2O solid, 0.01 mol of Zn(NO.sub.3).sub.2.Math.6H.sub.2O solid, and 0.006 mol of Ga(NO.sub.3).sub.3.Math.9H.sub.2O solid. Dissolve the three salts in a beaker containing 100 mL of deionized water.

[0059] B: Weigh 0.03 mol of anhydrous Na.sub.2CO.sub.3 solid and 0.015 mol of NaOH solid and dissolve them in a beaker containing 100 mL of deionized water.

[0060] C: Synthesize CuZnGa-LDHs by coprecipitation method; add 100 mL of deionized water into the three-necked flask, and titrate the two liquid solutions in Steps A and B into the 500 mL flask at the same titration rate, keeping the pH in the titration process within the range of 9-11, and then have the solution crystallize in a water bath at 60° C. for 12 hours, followed by centrifuging, washing, drying and grinding to obtain CuZnGa-LDHs.

[0061] D: Take 0.2 g of CuZnGa-LDHs sample, add 40 mL of 2 mol/L KOH solution and have it etched in a 60° C. water bath for 2 hours, followed by centrifugating, washing to neutrality, drying and grinding to obtain photocatalyst with high catalytic performance.

Application Example

[0062] The catalysts prepared in embodiments 1-4 are used separately in the coupling reaction of photocatalytic CO.sub.2 reduction and 5-HMF oxidation:

[0063] The reaction condition are as follows: put 30 mg of catalyst powder, 120 mg of 5-HMF and 60 mL of acetonitrile solution into a top-illuminated reactor, screw up the reactor and inject inert gas to displace the air in the device, close the outlet valve and inject inert gas to enable the pressure in the reactor reach 0.2 MPa, seal the reaction system, and have it stand for a period of time to observe whether the reactor leaks air. Under the condition that the airtightness of the reactor is good, turn on the 300 W Xe lamp to irradiate the reaction. After the reaction starts, take 1 mL of gas with a stainless steel gas-tight syringe at an interval of 1 h and inject it into gas chromatography for detection. The reaction activity of the catalyst is evaluated by detecting the concentration of the product in the gas. The contents of CO, CH.sub.4 and H.sub.2 in the gas are mainly tested. FIG. 5 shows the test results of embodiment 1.

[0064] Take out the reactor liner after 6 h of reaction, and stir it in the air at room temperature for 12 h to make the catalyst fully absorb CO.sub.2 in the air. After the catalyst recovers, repeat the photocatalytic reaction for five times, and take out the reaction solution. After centrifugation, use liquid chromatography to quantitatively analyze the products. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Cumulative CO FDCA yield Sample yield μmol/g % Embodiment 1 326.3 74.1 Embodiment 2 312.9 73.1 Embodiment 3 298.2 71.5 Embodiment 4 312.2 72.2

[0065] As shown in Table 1, the cumulative CO yield is 298-326 μmol/g, while the yield of the 5-HMF oxidation product, furan-2,5-dicarboxylic acid (FDCA), is 71.5-74.1%.