A CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas and its preparation method

Abstract

The present invention relates to the technical field of preparation of composite catalysts, specifically a CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas and a preparation method thereof, comprising the following preparation steps: S1. Preparation of a modified liquid; S2. Preparation of a precursor gel; S3. Modification of the precursor gel; S4. Formation of a catalyst. The oxygen vacancy modified solvent of the present invention can effectively regulate the oxygen vacancy content in the CuZn catalyst by introducing Ga elements. The presence of oxygen vacancies can promote the transfer of electrons from ZnO to Cu, enhance the interaction between Cu / ZnO, and generate more Zn δ+ defects, and regulate Cu 0 / (Cu 0 +Cu + ) ratio, the electron-rich Cu is beneficial to the dissociation and adsorption of CO, thereby promoting the key surface intermediate CH x *. At the same time, oxygen vacancies can also promote the activation and adsorption of CO, generating more key intermediates (such as CO* and CH x O*), thereby improving the selectivity of low-carbon alcohols.

Description

Technical Field

[0001] The present invention relates to the technical field of composite catalyst preparation, in particular to a CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas and a preparation method thereof. Background Art

[0002] The dwindling supply of fossil fuel resources and environmental concerns have prompted in-depth research into alternative energy sources. As clean energy sources, low-carbon alcohols are considered intermediates for many chemical products, green and clean gasoline additives, and potential fuel additives. To date, existing methods for synthesizing low-carbon alcohols, such as hydration of petroleum-derived olefins and biofermentation, have been reported. Unfortunately, these technologies suffer from low efficiency, high raw material costs, and complex product separation. For these reasons, the catalytic synthesis of low-carbon alcohols from synthesis gas derived from non-petroleum carbon resources such as coal, natural gas, biomass, or CO2 has become the most efficient and cleanest way to utilize energy resources and the most promising research focus. Currently, the catalytic conversion of synthesis gas to low-carbon alcohols over CuZnAl catalysts holds great promise due to its low raw material cost and low energy consumption, but still faces significant challenges due to the high methanol content.

[0003] Alkali and transition metal-modified CuZnAl methanol catalysts focus on enhancing CO dissociation and C-C coupling, improving selectivity for lower alcohols. Significant progress has recently been made in the synthesis of lower alcohols from syngas using CuZnAl catalysts, with the CLP method (complete liquid phase technique) being used to prepare CuZnAl catalysts in slurry form. These slurry catalysts achieve high selectivity for lower alcohols without the introduction of alkali or Fischer-Tropsch elements, advancing the general understanding of CuZnAl as a methanol catalyst and providing new insights into the active sites involved in carbon chain growth. However, the impact of reaction conditions (such as temperature, pressure, and gas composition) on catalyst performance remains unclear, requiring further optimization. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the object of the present invention is to provide a CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas and a preparation method thereof.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas comprises the following preparation steps:

[0007] S1. Preparation of a modified solution: 0.8-2.2 parts of Al(NO3)3·9H2O, 1.5-2 parts of a 10% chloroplatinic acid solution, and 6-7 parts of citric acid are dissolved in 45-55 parts of anhydrous ethanol, and ultrasonically dispersed at 60-70°C for 25-30 minutes. Subsequently, 0.1-0.3 parts of hexadecyltrimethylammonium bromide and 0.5-0.8 parts of sodium lauryl sulfate are added, and the mixture is stirred at 48-53°C for 2-3 hours. The temperature is then raised to 92-98°C and maintained for 25-35 minutes to obtain a modified solution.

[0008] S2. Preparation of a precursor gel: 0.6-0.82 parts of Cu(NO3)2·3H2O and 0.18-0.4 parts of Zn(NO3)2·6H2O were dissolved in 50-70 parts of an oxygen vacancy-modified solvent and stirred for 25-30 min to obtain a precursor gel;

[0009] S3 modification of the precursor gel: 8-12 parts of the modified solution obtained in step S1 were added to the precursor gel obtained in step S2, and stirring was continued until a green sol was formed, and aged for 10 days to obtain a modified precursor gel;

[0010] S4. Catalyst formation: Liquid paraffin was added to the modified precursor gel obtained in step S3, and the mixture was heat treated for 7-8h under a nitrogen atmosphere of 50mL / min to obtain a CuZn-based composite catalyst for synthesizing low-carbon alcohols from synthesis gas.

[0011] Preferably, the preparation of the oxygen vacancy modified solvent in step S2 comprises the following steps:

[0012] S21. 3-5 parts of modified hydrated gallium nitrate are dissolved in 50-70 parts by mass of 60% ethylene glycol solution to obtain a preliminary mixed solution;

[0013] S22. Ultrasonic dispersion of the preliminary mixed solution at 30-40° C. for 15-20 min at a frequency of 40-60 kHz to obtain an oxygen vacancy-modified solvent.

[0014] Preferably, the preparation of modified hydrated gallium nitrate in step S21 comprises the following steps:

[0015] S31. Dissolve 2-5 parts of Ga(NO3)3·5H2O in 60-80 parts of a mixed solvent, add 0.5-1.5 parts of disodium ethylenediaminetetraacetate, and stir magnetically at 30-40°C for 0.5-1h to form a preliminary mixed solution;

[0016] S32. Aqueous ammonia was slowly added dropwise until the pH of the solution was 3-4, and the mixture was stirred for 20-30 min before the solution was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 110-120 ° C for 3-4 h to obtain a secondary mixed solution;

[0017] S33. The secondary mixed solution obtained in step S32 is cooled, centrifuged, and separated. The resulting precipitate is washed three times with anhydrous ethanol and vacuum-dried at 55-60° C. for 10-12 hours to finally obtain modified hydrated gallium nitrate.

[0018] Preferably, the mixed solvent in step S31 is a mixture of 60% by mass ethylene glycol solution and deionized water, wherein the mass ratio of the 60% by mass ethylene glycol solution to the deionized water is 3:1.

[0019] Preferably, the stirring speed in steps S1, S2 and S3 is 350-450 r / min.

[0020] Preferably, the aging condition in step S3 is room temperature and away from light.

[0021] Preferably, in step S4, the mass ratio of liquid paraffin to modified precursor gel is 2-3:1.

[0022] Preferably, the frequency of ultrasonic dispersion in step S1 is 40-60 kHz.

[0023] Preferably, the temperature of the heat treatment in step S4 is 275-285°C.

[0024] A CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas is prepared by the above preparation method.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The aluminum (Al) element in the modified solution is uniformly loaded onto the CuZn substrate surface in the form of nano-alumina. This enhances the metal-support interaction, inhibits the sintering of Cu / Zn particles, and significantly improves the catalyst's thermal stability. Simultaneously, the synergistic effect of citric acid and hexadecyltrimethylammonium bromide forms a mesoporous structure, increasing the specific surface area. The introduction of aluminum regulates the acid-base balance on the catalyst surface, promoting CO adsorption and CC coupling, thereby enhancing the catalytic effect of the present invention.

[0027] 2. The oxygen vacancy modified solvent of the present invention can effectively regulate the oxygen vacancy content in the CuZn catalyst by introducing Ga elements. The presence of oxygen vacancies can promote the transfer of electrons from ZnO to Cu, enhance the interaction between Cu / ZnO, and generate more Zn δ+ defects, and regulate Cu 0 / (Cu 0 +Cu + ) ratio, the electron-rich Cu is beneficial to the dissociation and adsorption of CO, thereby promoting the key surface intermediate CH x*. At the same time, oxygen vacancies can also promote the activation and adsorption of CO, generating more key intermediates (such as CO* and CH x O*), thereby improving the selectivity of low-carbon alcohols. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of the preparation process of the CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas according to the present invention;

[0029] Figure 2 This is an X-ray diffraction analysis diagram of the CuZn-based composite catalyst for preparing lower alcohols from synthesis gas obtained in Examples 1-5 of the present invention;

[0030] Figure 3 Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and particle size analysis diagrams of the CuZn-based composite catalysts for preparing low-carbon alcohols from synthesis gas obtained in Examples 1-5 of the present invention (wherein, a1-e1 are TEM images of Examples 1-5, a2-e2 are HRTEM images of Examples 1-5, and a3-e3 are histograms of the Cu particle size distribution in Examples 1-5, respectively). DETAILED DESCRIPTION

[0031] The present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] See also Figure 1-3 , the present invention provides a technical solution:

[0033] Example 1

[0034] A method for preparing a CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas (in this embodiment, each mass portion is 10g):

[0035] S1. Preparation of a modified solution: 0.8 parts of Al(NO3)3·9H2O, 1.5 parts of a 10% chloroplatinic acid solution, and 6 parts of citric acid were dissolved in 45 parts of anhydrous ethanol and ultrasonically dispersed at 60°C for 25 min at a frequency of 40 kHz. Subsequently, 0.1 parts of hexadecyltrimethylammonium bromide and 0.5 parts of sodium lauryl sulfate were added. The mixture was stirred at 350 r / min at 48°C for 2 h, and the temperature was then raised to 92°C and maintained for 25 min to obtain a modified solution.

[0036] S2. Preparation of precursor gel: 0.6 parts of Cu(NO3)2·3H2O and 0.4 parts of Zn(NO3)2·6H2O were dissolved in 50 parts of 60% ethylene glycol solution and stirred at 350 rpm for 25 min to obtain a precursor gel;

[0037] S3 modification of the precursor gel: 8mL of the modified solution obtained in step S1 was added to the precursor gel obtained in step S2, and stirred at a speed of 350r / min until a green sol was formed, and aged for 10 days at room temperature in the dark to obtain a modified precursor gel;

[0038] S4. Catalyst formation: Liquid paraffin was added to the modified precursor gel obtained in step S3, with the mass ratio of liquid paraffin to modified precursor gel being 2:1. The mixture was heat-treated at 275°C for 7 h under a nitrogen atmosphere of 50 mL / min to obtain a CuZn-based composite catalyst for synthesizing low-carbon alcohols from synthesis gas.

[0039] Example 2

[0040] A method for preparing a CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas (in this embodiment, each mass portion is 1g, and the molar ratio of Al to Ga is ensured to be 2:1):

[0041] S1. Preparation of a modified solution: 2.2 parts of Al(NO3)3·9H2O, 2 parts of a 10% chloroplatinic acid solution, and 7 parts of citric acid were dissolved in 55 parts of anhydrous ethanol and ultrasonically dispersed at 70°C for 30 min at a frequency of 60 kHz. Subsequently, 0.3 parts of hexadecyltrimethylammonium bromide and 0.8 parts of sodium lauryl sulfate were added. The mixture was stirred at 450 r / min at 53°C for 3 h, and the temperature was then raised to 98°C and maintained for 35 min to obtain a modified solution.

[0042] S2. Preparation of precursor gel: 0.655 parts of Cu(NO3)2·3H2O and 0.345 parts of Zn(NO3)2·6H2O were dissolved in 70 parts of oxygen vacancy modified solvent and stirred at 450 r / min for 30 min to obtain a precursor gel;

[0043] S3. Modification of the precursor gel: 12 mL of the modified solution obtained in step S1 was added to the precursor gel obtained in step S2, and stirred at a speed of 450 r / min until a green sol was formed, and aged for 10 days at room temperature in the dark to obtain a modified precursor gel;

[0044] S4. Catalyst formation: Liquid paraffin was added to the modified precursor gel obtained in step S3, with the mass ratio of liquid paraffin to modified precursor gel being 3:1. The mixture was heat-treated at 285°C for 8 h under a nitrogen atmosphere of 50 mL / min to obtain a CuZn-based composite catalyst for synthesizing low-carbon alcohols from synthesis gas.

[0045] Wherein, the preparation of the oxygen vacancy modified solvent in step S2 comprises the following steps:

[0046] S21. 5 parts of modified hydrated gallium nitrate were dissolved in 70 parts by mass of 60% ethylene glycol solution to obtain a preliminary mixed solution;

[0047] S22. The preliminary mixed solution was ultrasonically dispersed at 40° C. for 20 min at a frequency of 60 kHz to finally obtain an oxygen vacancy-modified solvent.

[0048] The preparation of modified hydrated gallium nitrate in step S21 comprises the following steps:

[0049] S31. Dissolve 1 part of Ga(NO₃)₃·5H₂O in 80 parts of a mixed solvent (a mixture of 60% ethylene glycol solution and deionized water in a 3:1 mass ratio). Add 1.5 parts of disodium ethylenediaminetetraacetate, and stir magnetically at 40°C for 1 hour to form a preliminary mixed solution.

[0050] S32. Aqueous ammonia was slowly added dropwise until the pH of the solution was 4. After stirring for 30 min, the solution was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 120 ° C for 4 h to obtain a secondary mixed solution;

[0051] S33. The secondary mixed solution obtained in step S32 is cooled, centrifuged, and separated. The obtained precipitate is washed three times with anhydrous ethanol and vacuum-dried at 60° C. for 12 h to finally obtain modified hydrated gallium nitrate.

[0052] Example 3

[0053] A method for preparing a CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas (in this embodiment, each mass portion is 10g, and the molar ratio of Al to Ga is ensured to be 1:1):

[0054] S1. Preparation of a modified solution: 1.1 parts of Al(NO3)3·9H2O, 1.6 parts of a 10% chloroplatinic acid solution, and 6.5 parts of citric acid were dissolved in 50 parts of anhydrous ethanol and ultrasonically dispersed at 65°C for 27 minutes at a frequency of 50 kHz. Subsequently, 0.2 parts of hexadecyltrimethylammonium bromide and 0.6 parts of sodium lauryl sulfate were added. The mixture was stirred at 400 r / min at 50°C for 2.5 hours, and the temperature was then raised to 95°C and maintained for 30 minutes to obtain a modified solution.

[0055] S2. Preparation of precursor gel: 0.71 parts of Cu(NO3)2·3H2O and 0.29 parts of Zn(NO3)2·6H2O were dissolved in 60 parts of oxygen vacancy modified solvent and stirred at 400 r / min for 27 min to obtain a precursor gel;

[0056] S3. Modification of the precursor gel: 10 mL of the modified solution obtained in step S1 was added to the precursor gel obtained in step S2, and stirred at a speed of 400 r / min until a green sol was formed, and aged for 10 days at room temperature in the dark to obtain a modified precursor gel;

[0057] S4. Catalyst formation: Liquid paraffin was added to the modified precursor gel obtained in step S3, with a mass ratio of liquid paraffin to modified precursor gel being 2.5:1. The mixture was heat-treated at 280°C for 7.5h under a nitrogen atmosphere at a flow rate of 50mL / min to obtain a CuZn-based composite catalyst for synthesizing low-carbon alcohols from synthesis gas.

[0058] Wherein, the preparation of the oxygen vacancy modified solvent in step S2 comprises the following steps:

[0059] S21. 3 parts of modified hydrated gallium nitrate were dissolved in 60 parts by mass of 60% ethylene glycol solution to obtain a preliminary mixed solution;

[0060] S22. The preliminary mixed solution was ultrasonically dispersed at 35° C. for 17 minutes at a frequency of 50 kHz to obtain an oxygen vacancy-modified solvent.

[0061] The preparation of modified hydrated gallium nitrate in step S21 comprises the following steps:

[0062] S31. Dissolve 1 part of Ga(NO₃)₃·5H₂O in 65 parts of a mixed solvent (a mixture of 60% ethylene glycol solution and deionized water in a 3:1 mass ratio), add 0.7 parts of disodium ethylenediaminetetraacetate, and stir magnetically at 33°C for 0.8 h to form a preliminary mixed solution.

[0063] S32. Aqueous ammonia was slowly added dropwise until the pH of the solution reached 3.5. After stirring for 22 min, the solution was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 112 ° C for 3.5 h to obtain a secondary mixed solution;

[0064] S33. The secondary mixed solution obtained in step S32 is cooled, centrifuged, and separated. The obtained precipitate is washed three times with anhydrous ethanol and vacuum-dried at 56° C. for 10.5 h to finally obtain modified hydrated gallium nitrate.

[0065] Example 4

[0066] A method for preparing a CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas (in this embodiment, each mass portion is 5g, ensuring that the molar ratio of Al to Ga is 1:2):

[0067] S1. Preparation of a modified solution: 1.2 parts of Al(NO3)3·9H2O, 1.7 parts of a 10% chloroplatinic acid solution, and 6.6 parts of citric acid were dissolved in 52 parts of anhydrous ethanol and ultrasonically dispersed at 67°C for 29 minutes at a frequency of 55 kHz. Subsequently, 0.2 parts of hexadecyltrimethylammonium bromide and 0.7 parts of sodium lauryl sulfate were added. The mixture was stirred at 400 r / min at 52°C for 2.5 hours, and the temperature was then raised to 96°C and maintained for 33 minutes to obtain a modified solution.

[0068] S2. Preparation of precursor gel: 0.764 parts of Cu(NO3)2·3H2O and 0.236 parts of Zn(NO3)2·6H2O were dissolved in 65 parts of oxygen vacancy modified solvent and stirred at 400 r / min for 28 min to obtain a precursor gel;

[0069] S3. Modification of the precursor gel: 11 mL of the modified solution obtained in step S1 was added to the precursor gel obtained in step S2, and stirred at a speed of 400 r / min until a green sol was formed, and aged for 10 days at room temperature in the dark to obtain a modified precursor gel;

[0070] S4. Catalyst formation: Liquid paraffin was added to the modified precursor gel obtained in step S3, with a mass ratio of liquid paraffin to modified precursor gel being 2.6:1. The mixture was heat-treated at 283°C for 7.5h under a nitrogen atmosphere of 50mL / min to obtain a CuZn-based composite catalyst for synthesizing low-carbon alcohols from synthesis gas.

[0071] Wherein, the preparation of the oxygen vacancy modified solvent in step S2 comprises the following steps:

[0072] S21. 4 parts of modified hydrated gallium nitrate were dissolved in 65 parts by mass of 60% ethylene glycol solution to obtain a preliminary mixed solution;

[0073] S22. The preliminary mixed solution was ultrasonically dispersed at 37° C. for 19 minutes at a frequency of 55 kHz to obtain an oxygen vacancy-modified solvent.

[0074] The preparation of modified hydrated gallium nitrate in step S21 comprises the following steps:

[0075] S31. Dissolve 1.9 parts of Ga(NO₃)₃·5H₂O in 70 parts of a mixed solvent (a mixture of 60% ethylene glycol solution and deionized water in a 3:1 mass ratio), add 1 part of disodium ethylenediaminetetraacetic acid, and stir magnetically at 35°C for 0.7 h to form a preliminary mixed solution.

[0076] S32. Aqueous ammonia was slowly added dropwise until the pH of the solution reached 3.4. After stirring for 25 min, the solution was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 115 ° C for 3.5 h to obtain a secondary mixed solution;

[0077] S33. The secondary mixed solution obtained in step S32 is cooled, centrifuged, and separated. The obtained precipitate is washed three times with anhydrous ethanol and vacuum-dried at 58° C. for 11 h to finally obtain modified hydrated gallium nitrate.

[0078] Example 5

[0079] A method for preparing a CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas (in this embodiment, each mass portion is 10g):

[0080] S1. Preparation of a modified solution: 1.9 parts of a 10% chloroplatinic acid solution and 6.5 parts of citric acid were dissolved in 50 parts of anhydrous ethanol and ultrasonically dispersed at 65°C for 27 minutes at a frequency of 50 kHz. Subsequently, 0.2 parts of hexadecyltrimethylammonium bromide and 0.6 parts of sodium lauryl sulfate were added. The mixture was stirred at 420 rpm at 50°C for 2.5 hours, and the temperature was then raised to 95°C and maintained for 30 minutes to obtain a modified solution.

[0081] S2. Preparation of precursor gel: 0.82 parts of Cu(NO3)2·3H2O and 0.18 parts of Zn(NO3)2·6H2O were dissolved in 60 parts of oxygen vacancy modified solvent and stirred at 420 r / min for 27 min to obtain a precursor gel;

[0082] S3. Modification of the precursor gel: 10 mL of the modified solution obtained in step S1 was added to the precursor gel obtained in step S2, and stirred at a speed of 420 r / min until a green sol was formed, and aged for 10 days at room temperature in the dark to obtain a modified precursor gel;

[0083] S4. Catalyst formation: Liquid paraffin was added to the modified precursor gel obtained in step S3, with a mass ratio of liquid paraffin to modified precursor gel being 2.5:1. The mixture was heat-treated at 280°C for 7.5h under a nitrogen atmosphere at a flow rate of 50mL / min to obtain a CuZn-based composite catalyst for synthesizing low-carbon alcohols from synthesis gas.

[0084] Wherein, the preparation of the oxygen vacancy modified solvent in step S2 comprises the following steps:

[0085] S21. 3 parts of modified hydrated gallium nitrate were dissolved in 60 parts by mass of 60% ethylene glycol solution to obtain a preliminary mixed solution;

[0086] S22. The preliminary mixed solution was ultrasonically dispersed at 35° C. for 17 minutes at a frequency of 50 kHz to obtain an oxygen vacancy-modified solvent.

[0087] The preparation of modified hydrated gallium nitrate in step S21 comprises the following steps:

[0088] S31. Dissolve 4 parts of Ga(NO₃)₃·5H₂O in 75 parts of a mixed solvent (a mixture of 60% ethylene glycol solution and deionized water in a 3:1 mass ratio). Add 1.3 parts of disodium ethylenediaminetetraacetate, and stir magnetically at 38°C for 0.9 h to form a preliminary mixed solution.

[0089] S32. Aqueous ammonia was slowly added dropwise until the pH of the solution reached 3.6. After stirring for 28 min, the solution was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 118 ° C for 3.6 h to obtain a secondary mixed solution;

[0090] S33. The secondary mixed solution obtained in step S32 is cooled, centrifuged, and separated. The obtained precipitate is washed three times with anhydrous ethanol and vacuum-dried at 59° C. for 11.5 h to finally obtain modified hydrated gallium nitrate.

[0091] The CuZn-based composite catalyst for syngas to low-carbon alcohols was named CZA in performance and characterization tests. x G y , where x and y represent the molar ratios of Al and Ga, respectively. In the following performance tests and characterization tests, the CuZn-based composite catalysts for synthesizing lower alcohols from synthesis gas obtained in Examples 1-5 were named CZA, CZA2G1, CZA1G1, CZA1G2, and CZG, respectively.

[0092] Performance testing:

[0093] The CuZn-based composite catalyst for synthesizing lower alcohols from synthesis gas prepared in Examples 1-5 was supplemented with liquid paraffin to 300 mL and then placed in a reactor at a temperature of 280°C and a pressure of 4 MPa. Synthesis gas was introduced into the reactor at a flow rate of 150 mL / min, and the reaction was carried out while maintaining an n(H2) / n(CO) ratio of 2. During the reaction, the product composition was analyzed using a Hisense GC-950 chromatograph. In the gaseous product, organic components (C1-C5 hydrocarbons, dimethyl ether, methanol, and ethanol) were analyzed online using a flame ionization detector (FID detector, HP-PLOT / Q column), and inorganic components (H2, CO, CH4, and CO2) were analyzed online using a thermal conductivity detector (TCD detector, TDX-01 column). Alcohols in the liquid product were detected offline using an FID detector (HP-INNOWAX column). The content of each component in the product was quantitatively analyzed using an external standard method. The CO conversion rate and product selectivity were calculated as follows:

[0094] ,

[0095] ,

[0096] Where i represents all C-containing compounds in the gas and liquid products except CO, n(CO) out Indicates the amount of CO in the outlet gas (mol), n i (g) and n i (I) represents the number of carbon atoms (mol) of component i in the outlet gas and liquid phase, respectively;

[0097] S(i) represents the selectivity of the catalyst for product i,

[0098] S (lower alcohol) = S (ethanol) + S (propanol) + S (butanol) + S (pentanol) + S (hexanol),

[0099] Space-time yield (STY, g·g -1 ·h -1 ) = (total alcohol mass / catalyst mass) / reaction time,

[0100] S (total alcohol) = S (methanol) + S (ethanol) + S (propanol) + S (butanol) + S (pentanol) + S (hexanol),

[0101] C 2+ Alcohol / total alcohol = S (low-carbon alcohol) / S (total alcohol), the results are shown in Table 1:

[0102] Table 1 Catalytic performance of catalysts for syngas to low-carbon alcohols at 280°C, 4 MPa, n(H2) / n(CO) = 2.0, 150 mL / min

[0103]

[0104] The CZG catalyst (Cu particles 27.3 nm) exhibited the highest CO conversion (56.4%) and lower alcohol selectivity (76.5%), confirming that smaller Cu particles facilitated increased active site exposure and oxygen vacancy effects. Catalysts containing Ga (CZA1G2 and CZG) exhibited significantly improved lower alcohol selectivity, indicating that the oxygen vacancies introduced by Ga promoted CO adsorption and CC coupling, suppressing the formation of byproducts such as methane. A comparison of CZA2G1 (Al:Ga molar ratio of 2:1) with CZA1G2 (Al:Ga molar ratio of 1:2) revealed that higher Ga content significantly enhanced lower alcohol selectivity.

[0105] Characterization Tests:

[0106] 1. X-ray diffraction analysis

[0107] Attachment Figure 2 The X-ray diffraction (XRD) patterns of the CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas prepared in Example 1-5 are shown. Three obvious diffraction peaks appeared at 43.4°, 50.5° and 74.2°, corresponding to the Cu (111), (200) and (220) crystal planes, respectively. These diffraction peaks are due to the reduction of CuO by carbon / hydrogen radicals generated by the decomposition of liquid paraffin during the heat treatment of the catalyst precursor. No signal peak of ZnO was observed, indicating that ZnO existed in an amorphous form or was below the detection limit of XRD. There was a weak carbon peak at 23.6°, indicating that the liquid paraffin had decomposed. No diffraction peaks corresponding to Al and Ga were observed in the catalyst, indicating that they existed in a highly dispersed or encapsulated form in the ZnO matrix.

[0108] 2. Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and particle size analysis

[0109] The microstructure and affinity of Cu and ZnO in the products obtained in Examples 1-5 were studied using TEM and HRTEM. Figure 3 As shown in (a3-e3). We can observe the presence of black spherical nanoparticles in all catalysts, which correspond to Cu, and the average particle size of Cu in CZA, CZA2G1, CZA1G1, CZA1G2 and CZG catalysts is 33.2nm, 32.9nm, 48.2nm, 30.3nm and 27.3nm, respectively. Although the Cu particle size obtained by TEM analysis is larger than that obtained by XRD analysis, their change trends are consistent, so there is no essential difference in the conclusions. In addition, the microstructures of Cu and ZnO were observed by HRTEM images (see Appendix). Figure 3(a2-e2)), the lattice spacing of 0.21 nm and 0.25 nm corresponds to the Cu (111) and ZnO (101) planes, respectively, and the two substances are adjacent, which helps to induce strong Cu / ZnO interaction, thereby promoting the formation of catalytic active sites during CO hydrogenation to low-carbon alcohols.

[0110] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas, characterized in that: The method comprises the following preparation steps: S1. Preparation of a modified solution: 0.8-2.2 parts of Al(NO3)3·9H2O, 1.5-2 parts of a 10% chloroplatinic acid solution, and 6-7 parts of citric acid are dissolved in 45-55 parts of anhydrous ethanol, and ultrasonically dispersed at 60-70°C for 25-30 minutes. Subsequently, 0.1-0.3 parts of hexadecyltrimethylammonium bromide and 0.5-0.8 parts of sodium lauryl sulfate are added, and the mixture is stirred at 48-53°C for 2-3 hours. The temperature is then raised to 92-98°C and maintained for 25-35 minutes to obtain a modified solution. S2. Preparation of a precursor gel: 0.6-0.82 parts of Cu(NO3)2·3H2O and 0.18-0.4 parts of Zn(NO3)2·6H2O were dissolved in 50-70 parts of an oxygen vacancy-modified solvent and stirred for 25-30 min to obtain a precursor gel; S3 modification of the precursor gel: 8-12 parts of the modified solution obtained in step S1 were added to the precursor gel obtained in step S2, and stirring was continued until a green sol was formed, and aged for 10 days to obtain a modified precursor gel; S4 catalyst formation: liquid paraffin was added to the modified precursor gel obtained in step S3, and the mixture was heat treated under a nitrogen atmosphere of 50 mL / min for 7-8 h to obtain a CuZn-based composite catalyst for synthesis of lower alcohols from synthesis gas; The preparation of the oxygen vacancy modified solvent in step S2 comprises the following steps: S21. 3-5 parts of modified hydrated gallium nitrate are dissolved in 50-70 parts by mass of 60% ethylene glycol solution to obtain a preliminary mixed solution; S22. Ultrasonic dispersion of the preliminary mixed solution at 30-40° C. for 15-20 min at a frequency of 40-60 kHz to obtain an oxygen vacancy-modified solvent.

2. The method for preparing a CuZn-based composite catalyst for preparing lower alcohols from synthesis gas according to claim 1, wherein: The preparation of modified hydrated gallium nitrate in step S21 comprises the following steps: S31. Dissolve 2-5 parts of Ga(NO3)3·5H2O in 60-80 parts of a mixed solvent, add 0.5-1.5 parts of disodium ethylenediaminetetraacetate, and stir magnetically at 30-40°C for 0.5-1h to form a preliminary mixed solution; S32. Aqueous ammonia was slowly added dropwise until the pH of the solution was 3-4, and the mixture was stirred for 20-30 min before the solution was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 110-120 ° C for 3-4 h to obtain a secondary mixed solution; S33. The secondary mixed solution obtained in step S32 is cooled, centrifuged, and separated. The resulting precipitate is washed three times with anhydrous ethanol and vacuum-dried at 55-60° C. for 10-12 hours to finally obtain modified hydrated gallium nitrate.

3. The method for preparing a CuZn-based composite catalyst for preparing lower alcohols from synthesis gas according to claim 2, wherein: In step S31, the mixed solvent is a mixture of 60% by mass ethylene glycol solution and deionized water, wherein the mass ratio of the 60% by mass ethylene glycol solution to the deionized water is 3:

1.

4. The method for preparing a CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas according to claim 1, wherein: The stirring speed in steps S1, S2 and S3 is 350-450 r / min.

5. The method for preparing a CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas according to claim 1, wherein: The aging conditions in step S3 are room temperature and light-proof.

6. The method for preparing a CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas according to claim 1, wherein: In step S4, the mass ratio of liquid paraffin to modified precursor gel is 2-3:

1.

7. The method for preparing a CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas according to claim 1, wherein: The frequency of ultrasonic dispersion in step S1 is 40-60 kHz.

8. The method for preparing a CuZn-based composite catalyst for preparing lower alcohols from synthesis gas according to claim 1, wherein: The temperature of the heat treatment in step S4 is 275-285°C.

9. A CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas, characterized by: The CuZn-based composite catalyst for preparing low-carbon alcohols from synthesis gas is prepared by the preparation method according to any one of claims 1 to 8.

Images