Preparation of molecular sieve supported metal catalyst and application of molecular sieve supported metal catalyst in catalyzing hydrogenation of carbon dioxide to prepare low-carbon alcohol

Abstract

The invention relates to the technical field of catalysts, in particular to preparation of a molecular sieve supported metal catalyst and application of the molecular sieve supported metal catalyst in catalyzing hydrogenation of carbon dioxide to prepare low-carbon alcohol. The preparation method of the molecular sieve supported metal catalyst comprises the following steps: (1) preparing an A-ZSM-48 molecular sieve, wherein A comprises at least one of potassium or sodium; (2) preparing a modified liquid: adding water into a water-soluble salt containing B, and mixing to obtain the modified liquid; b is at least one of Cu, Zn, Fe, Co, Pt and Ru; and (3) mixing the A-ZSM-48 molecular sieve with the modified liquid, concentrating, drying, and roasting to obtain the molecular sieve supported metal catalyst, the catalyst has high carbon dioxide conversion rate, the obtained low-carbon alcohol has high selectivity, the use demand of noble metal is reduced, and carbon dioxide resource utilization with more cost benefits is realized.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to the preparation of a molecular sieve-supported metal catalyst and its application in catalyzing the hydrogenation of carbon dioxide to produce low-carbon alcohols. Background Art

[0002] The catalysts for the hydrogenation of CO2 to low-carbon alcohols can be roughly divided into four categories: metal catalysts, tandem catalysts, metal carbide catalysts and supported catalysts. Metal catalysts can be further subdivided into precious metal catalysts and transition metal catalysts.

[0003] Precious metals (such as platinum, palladium, rhodium, etc.) show high activity and selectivity in catalysis, and have good reaction stability and catalytic efficiency. However, the limited resources and high prices of precious metals restrict their widespread use in industrial applications.

[0004] In contrast, transition metal catalysts (such as iron, cobalt, copper, etc.) show obvious advantages in terms of economy and have high catalytic activity in CO2 hydrogenation reactions. However, these catalysts are prone to metal particle sintering or carbon deposition under high temperature reaction conditions, resulting in catalyst deactivation, poor product selectivity, and usually accompanied by the formation of by-products.

[0005] By combining different types of catalysts, tandem catalysts can more efficiently promote the conversion of CO2 to low-carbon alcohols, significantly improving the efficiency and selectivity of the reaction. However, the design of a tandem catalyst system is complex, requiring precise adjustment of the combination ratio of different catalysts, and different catalysts may require different reaction conditions, which greatly increases the difficulty and complexity of the operation.

[0006] Metal carbide catalysts, due to their excellent electronic properties, can adjust the electron density of metal active sites, thereby improving catalytic activity, effectively reducing the formation of by-products, and improving the selectivity of target products. However, the structure of metal carbide catalysts is relatively sensitive and prone to decomposition or transformation, which in turn leads to the decline of catalyst performance and catalytic stability.

[0007] Supported catalysts can effectively disperse metal active sites by selecting suitable carriers (such as metal organic frameworks, oxides, nitrides, etc.), thereby improving the stability of the catalyst. However, the rapid growth and aggregation of metal particles on the carrier will lead to catalyst deactivation, so the choice of carrier has an important influence on the dispersion of metal particles and catalytic performance. In addition, the synthesis methods of some carriers are relatively complicated, which may be unfavorable for the industrial application of catalysts.

[0008] Ding L et al. (see: Ding L, Shi T, Gu J, et al. CO2 hydrogenation to ethanol over Cu@Na-Beta[J]. Chem, 2020, 6(10): 2673-2689) prepared a high-performance Cu@Na-Beta catalyst by a two-step method. In the synthesis of the Cu@Na-Beta catalyst, 6.00 g of Na-Beta zeolite (Si / Al about 25) with a particle size of about 0.1 mm was used to introduce intracrystalline mesopores by alkaline treatment, using 200 mL of 0.200 mol / L NaOH solution at 65 °C for 30 minutes, followed by filtration, washing and drying (labeled as alk-Beta). Then, CuO was introduced into the pores of alk-Beta by impregnation with Cu(NO3)2 ethanol solution, and then calcined at 450 °C for 3 hours (labeled as CuO / alk-Beta). In the next step, 1.00 g CuO / alk-Beta was thoroughly mixed with a Na-Beta zeolite synthesis gel, which was made of 0.125 g Al2(SO4)3·18H2O, 3.16 g 20% ​​tetraethylamino hydroxide (TEAOH), 0.540 g SiO2 and 0.0275 g NaOH. The synthesis gel was crystallized at 180 °C for 2 days by dry gel conversion method, then thoroughly washed with water and calcined in air at 550 °C for 4 hours to remove the template agent. The sample was labeled CuO@Na-Beta. Before catalytic testing, CuO@Na-Beta was reduced with 5% H2 / N2 gas at 350 °C for 1.5 hours (labeled as Cu@Na-Beta catalyst). At 300 °C, 1.3 MPa pressure and 12000 mL / gcat / h space velocity, the CO2 conversion rate of Cu@Na-Beta catalyst can reach 12.2%. Chinese invention patent CN115283008A discloses a catalyst for preparing low-carbon alcohols from carbon dioxide, and its preparation method and application. The preparation method is: a uniformly mixed cobalt precursor 1, cobalt precursor 2 and molecular sieve are subjected to mechanical ball milling and heat treatment to obtain a catalyst product. The invention provides a method for preparing a catalyst for preparing low-carbon alcohols from carbon dioxide, using cobalt precursor 1, cobalt precursor 2 and molecular sieve as raw materials, and converting Co single atom sites (Co x+ ) and Co nanocluster sites (Co 0 ) is introduced into the molecular sieve to create Co 0 -Co x+ The double sites can catalyze the formation of alcohols and the growth of carbon chains, greatly promoting the selectivity of low-carbon alcohols, which is higher than 85%, among which C 3+ The alcohol selectivity was higher than 40%.

[0009] Existing catalysts used for CO2 hydrogenation to produce low-carbon alcohols still face several problems, mainly manifested in high cost, complex synthesis methods or high design difficulty, and poor catalyst stability (such as loss of active components, sintering or aggregation leading to deactivation). These problems have significantly restricted the further development and practical application of CO2 hydrogenation to produce low-carbon alcohols catalysts.

[0010] Therefore, the technical problem to be solved by the present invention is to overcome the problems in the prior art of high cost of CO2 hydrogenation catalysts to produce low-carbon alcohols, easy aggregation of metal active sites during catalyst preparation, and easy sintering or carbon deposition of metal particles during use, resulting in easy deactivation and poor stability of the catalyst. Summary of the invention

[0011] Based on the purpose of solving the above technical problems, the technology of the present invention is proposed, which specifically relates to the preparation of a molecular sieve-supported metal catalyst and its application in catalyzing the hydrogenation of carbon dioxide to produce low-carbon alcohols.

[0012] The present invention provides a method for preparing a molecular sieve-supported metal catalyst, comprising the following steps: Step (1), preparing A-ZSM-48 molecular sieve: mixing an alkali source containing A with water, adding a template agent and mixing, then adding an aluminum source and mixing, then adding a silicon source and mixing, adding ZSM-48 as a seed crystal and mixing, then placing in an autoclave at 140-180° C. for crystallization for 40-80 hours, filtering, washing, drying, and calcining at 500-600° C. for 3-7 hours to obtain A-ZSM-48 molecular sieve; Wherein, A includes at least one of potassium or sodium; the alkali source containing A includes at least one of hydroxide, carbonate and bicarbonate containing A; Step (2), preparing a modified liquid: adding water to a water-soluble salt containing B and mixing to obtain a modified liquid; Wherein, B is at least one of Cu, Zn, Fe, Co, Pt, and Ru, and the water-soluble salt containing B includes at least one of a sulfate or chloride containing B; Step (3), preparing a molecular sieve-supported metal catalyst: the A-ZSM-48 molecular sieve prepared in step (1) is mixed with the modified liquid prepared in step (2), concentrated, dried, and then transferred to a muffle furnace for calcination at 500-600° C. for 3-7 hours to obtain a molecular sieve-supported metal catalyst.

[0013] Furthermore, the template agent includes at least one of hexamethylenediamine, 1,6-pentanediamine, 1,8-octanediamine, hexamethyldiammonium bromide, and dimethylbiscyclohexylammonium hydroxide.

[0014] Furthermore, the aluminum source includes at least one of aluminum oxyhydroxide, sodium aluminate, pseudo-boehmite, and aluminum sulfate.

[0015] Furthermore, the silicon source includes at least one of silica sol, fumed silica, macroporous silica gel, tetraethyl orthosilicate, and sodium silicate.

[0016] Furthermore, the alkali source containing A includes at least one of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate.

[0017] Further, the alkali source containing A includes sodium hydroxide and potassium hydroxide.

[0018] Furthermore, the alkali source containing A includes sodium hydroxide and potassium hydroxide in a molar ratio of 1:(0.9-1.3).

[0019] Further, step (1) is: step (1) is: mixing 1-3g of an alkali source containing A with 80-120mL of water, adding 3-6g of a template agent, then adding 0.1-0.5g of an aluminum source, then adding 30-50g of a silicon source, and finally adding 0.5-1g of ZSM-48 as a seed crystal, and then placing in an autoclave at 140-180°C for crystallization for 40-80 hours, filtering, washing, drying, and calcining at 500-600°C for 3-7 hours to obtain an A-ZSM-48 molecular sieve.

[0020] Furthermore, in step (2), the ratio of the water-soluble salt containing B to water is 1-3 g: 8-15 mL.

[0021] Furthermore, in step (2), the water-soluble salt containing B includes at least one of copper sulfate, zinc sulfate, ferric sulfate, ferrous sulfate, cobalt sulfate, copper chloride, zinc chloride, ferric chloride, ferrous chloride, cobalt chloride, or a hydrate thereof.

[0022] Furthermore, in step (2), the water-soluble salt containing B includes copper sulfate pentahydrate and zinc sulfate.

[0023] Furthermore, in step (2), the water-soluble salt containing B comprises copper sulfate pentahydrate and zinc sulfate in a mass ratio of 9-15:1.

[0024] Furthermore, in step (3), the mass ratio of A-ZSM-48 molecular sieve to modifying liquid is 4-6 g:10-20 g.

[0025] Furthermore, in step (3), the calcination heating rate is 1.5-2.5°C / min.

[0026] The present invention also provides a molecular sieve-supported metal catalyst prepared according to the above preparation method.

[0027] The present invention also provides the use of the molecular sieve-supported metal catalyst in catalyzing the hydrogenation of carbon dioxide to produce low-carbon alcohols.

[0028] Furthermore, the application steps include: making the molecular sieve-loaded metal catalyst into particles, loading them in a catalytic reactor, and reducing the particles with a hydrogen atmosphere; then sending a mixed gas consisting of hydrogen, carbon dioxide and nitrogen into the reactor for catalytic reaction, and controlling the catalytic reaction pressure, temperature and mixed gas flow rate to prepare low-carbon alcohols.

[0029] Compared with the prior art, the present invention is progressive in that: The use of ZSM-48 molecular sieve-loaded metal catalysts for the hydrogenation of carbon dioxide to produce low-carbon alcohols has significant advantages. First, the unique pore structure of the ZSM-48 molecular sieve effectively promotes the uniform dispersion of metals, avoids sintering or carbon deposition of metal particles, and significantly improves the stability and reaction efficiency of the catalyst. Secondly, the synergistic effect of the metal active sites optimizes the selectivity for ethanol and inhibits the formation of by-products. In addition, the ZSM-48 molecular sieve carrier can maintain the stability of the catalyst at high temperatures and extend its service life. While improving catalytic activity and optimizing selectivity, the high stability and high temperature resistance of the ZSM-48 molecular sieve-loaded metal catalyst give it good potential for industrial application, further reducing the demand for the use of precious metals, thereby achieving a more cost-effective resource utilization of carbon dioxide.

[0030] The molecular sieve-supported metal catalyst prepared by the present invention is effective for methanol, ethanol, C3 + Low-carbon alcohols such as ethanol have good selectivity, high catalytic CO2 conversion rate, and good catalytic effect in the synthesis of low-carbon alcohols.

[0031] In the present invention, potassium- or sodium-containing alkali sources are combined with ZSM-48 molecular sieves to prepare sodium-type or potassium-type molecular sieve-loaded metal catalysts, both of which have good selectivity for low-carbon alcohols. The catalyst prepared from the potassium-containing alkali source has better total alcohol selectivity, while the catalyst prepared from the sodium-containing alkali source has better selectivity for methanol.

[0032] In the present invention, the catalyst prepared by containing both sodium and potassium in the alkali source has a higher total alcohol selectivity, and the two promote each other and synergistically enhance the total alcohol selectivity and CO2 conversion rate.

[0033] In the present invention, the effect of the catalyst prepared by the water-soluble salt containing zinc is poorer than that of the water-soluble salt containing copper; while keeping the total amount of water-soluble salt unchanged, the catalyst prepared by the water-soluble salt containing copper and zinc (for example, the ratio of the water-soluble salts of the two is 9-15:1) has a higher catalytic CO2 conversion rate, and the conversion of methanol, C3 + The selectivity of alcohol and total alcohol is higher.

[0034] The catalyst of the present invention has excellent performance and good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is the XRD pattern of Cu / Na-ZSM-48 of Example 1.

[0036] Figure 2 This is the SEM image of Cu / Na-ZSM-48 of Example 1.

[0037] Figure 3 This is a TEM image of Cu / Na-ZSM-48 of Example 1. DETAILED DESCRIPTION

[0038] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Silica sol: HS-40, Guangdong Huierte Nanotechnology Co., Ltd.

[0040] ZSM-48: molecular sieve, product number NKF-17-100, Tianjin Nanhua Catalyst Co., Ltd.

[0041] ZSM-5: molecular sieve, product number NKF-5-18H, Tianjin Nanhua Catalyst Co., Ltd.

[0042] ZSM-22: molecular sieve, product number NKF-22-40, Tianjin Nanhua Catalyst Co., Ltd.

[0043] Example 1 (1) Preparation of Na-ZSM-48 molecular sieve: Under stirring conditions, 1.2 g (0.03 mol) of NaOH was added to 90 mL of deionized water and stirred until completely dissolved. Then, 4.34 g of H2N(CH2)6NH2 (HAD, hexamethylenediamine) was added. After sufficient stirring, 0.2 g of pseudo-boehmite was added. After stirring until the mixed solution became clear and transparent, 37.5 g of silica sol was slowly added. After the mixture was stirred at room temperature for 2 hours, 0.75 g of ZSM-48 was added as a seed crystal and stirred evenly to obtain a synthetic gel. The synthesized gel was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and crystallized at 160°C for 2 days. The product was filtered, washed with ethanol and ultrapure water, dried in an oven at 110°C for 8 hours, and then calcined at 550°C for 5 hours to remove the template HAD, obtaining the product Na-ZSM-48 molecular sieve.

[0044] (2) Synthesis of Cu / Na-ZSM-48 catalyst: Dissolve 1.96g CuSO4·5H2O in 10mL ultrapure water and stir to completely dissolve it. Add 5g of the product obtained in step (1) to the above impregnation solution, stir at 80°C for 4 hours, and then stand for 12 hours. After rotary evaporation, place in an oven at 110°C for 6 hours, and then transfer to a muffle furnace and roast at 550°C for 5 hours. The roasting temperature is increased at a rate of 2°C / min to obtain a Cu / Na-ZSM-48 catalyst. The product was subjected to XRD, SEM and TEM tests. The results are shown in the figure. Figure 1-3 .

[0045] according to Figure 1-3 The test shows that the catalyst prepared in Example 1 has the characteristic peaks of ZSM-48 and good crystallinity; the morphology is shuttle-shaped, with a radial dimension of 0.3-1 µm and a length of about 1-3 µm; the copper nanoparticles are evenly distributed on the ZSM-48 molecular sieve carrier, with a particle size of 1-6 nm.

[0046] (3) Catalytic performance evaluation: The Cu / Na-ZSM-48 catalyst obtained in step (2) was pressed into pellets and then made into particles with a mesh size of 60-100. 300 mg was weighed and placed in a catalytic reactor under a H2 atmosphere at a gas velocity of 2000 mL / (g cat ·h -1 ), reduced at 300℃ for 2 hours, then H2, CO2 and N2 with a volume ratio of 3:1:1 were fully mixed in a gas mixing device and then sent to the reactor. The catalytic reaction was controlled at a pressure of 4.0MPa, a temperature of 240℃ and a gas velocity of 4000mL / (g cat ·h -1 ) conditions. Then the reaction products were analyzed by gas chromatography to calculate the conversion rate of CO2 and the selectivity of low-carbon alcohols. The test results are shown in Table 1.

[0047] The carbon dioxide conversion rate and product selectivity were calculated according to the following formula: Carbon dioxide conversion rate = (inlet carbon dioxide mole number - outlet carbon dioxide mole number) / import carbon dioxide mole number × 100%; product selectivity = outlet product mole number × number of carbon atoms in the product / (inlet carbon dioxide mole number - outlet carbon dioxide mole number) × 100%.

[0048] Example 2 (1) Preparation of Na-ZSM-48 molecular sieve: Under stirring conditions, 1.10 g of NaOH was added to 95 mL of deionized water and stirred until completely dissolved, then 4.5 g of H2N(CH2)6NH2 (HAD, hexamethylenediamine) was added, and 0.25 g of pseudo-boehmite was added after sufficient stirring. After stirring until the mixed solution became clear and transparent, 35.5 g of silica sol was slowly added. After the mixture was stirred at room temperature for 3 hours, 0.8 g of ZSM-48 was added as a seed crystal and stirred evenly to obtain a synthetic gel; The synthesized gel was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and crystallized at 170°C for 2.5 days. The product was filtered, washed with ethanol and ultrapure water, dried in an oven at 110°C for 8.5 hours, and then calcined at 570°C for 6 hours to remove the template HAD, obtaining the product Na-ZSM-48 molecular sieve.

[0049] (2) Synthesis of Cu / Na-ZSM-48 catalyst: 2.05 g of CuSO4·5H2O was dissolved in 12.5 mL of ultrapure water and stirred to completely dissolve. 5.2 g of the product obtained in step (1) was added to the above impregnation solution and stirred at 85°C for 3.2 hours, then allowed to stand for 10 hours, and then dried in an oven at 105°C for 4.5 hours after rotary evaporation. The mixture was then transferred to a muffle furnace and calcined at 560°C for 5.5 hours at a calcination rate of 2.2°C / min to obtain a Cu / Na-ZSM-48 catalyst.

[0050] (3) The prepared Cu / Na-ZSM-48 catalyst was placed in a catalytic reactor, and the catalytic performance of the catalyst was evaluated according to the method of step (3) in Example 1. The results are shown in Table 1.

[0051] Example 3 (1) Preparation of K-ZSM-48 molecular sieve: Under stirring conditions, 1.683 g (0.03 mol) of KOH was added to 90 mL of deionized water and stirred until completely dissolved. 4.34 g of HAD was added and stirred thoroughly. 0.2 g of pseudo-boehmite was added and stirred until the mixed solution became clear and transparent. Then 37.5 g of silica sol was slowly added. After stirring at room temperature for 2 hours, 0.75 g of ZSM-48 was added as a seed crystal and stirred evenly to obtain a synthetic gel. The synthesized gel was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and crystallized at 160°C for 2 days. The product was filtered, washed, dried in an oven at 110°C for 8 hours, and then calcined at 550°C for 5 hours to remove the template HAD, obtaining the product K-ZSM-48 molecular sieve.

[0052] (2) Synthesis of Cu / K-ZSM-48 catalyst: 1.96 g of CuSO4·5H2O was dissolved in 10 mL of ultrapure water and stirred to completely dissolve. 5 g of the product obtained in step (1) was added to the impregnation solution and stirred at 80°C for 4 hours, then allowed to stand for 12 hours, and then dried in an oven at 110°C for 6 hours, and then transferred to a muffle furnace and calcined at 550°C for 5 hours to remove the template agent HAD, thereby obtaining the product Cu / K-ZSM-48 catalyst.

[0053] (3) The prepared Cu / K-ZSM-48 catalyst was placed in a catalytic reactor, and the catalytic performance of the catalyst was evaluated according to the method of step (3) in Example 1. The results are shown in Table 1.

[0054] Example 4 (1) Preparation of K / Na-ZSM-48 molecular sieve: Under stirring conditions, 0.6 g (0.015 mol) NaOH and 0.8415 g (0.015 mol) KOH were added to 90 mL deionized water and stirred until completely dissolved. 4.34 g HAD was added and stirred thoroughly. 0.2 g pseudo-boehmite was added and stirred until the mixed solution became clear and transparent. Then 37.5 g silica sol was slowly added. After stirring at room temperature for 2 hours, 0.75 g ZSM-48 was added as a seed crystal and stirred evenly to obtain a synthetic gel. The synthesized gel was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and crystallized at 160°C for 2 days. The product was filtered, washed, dried in an oven at 110°C for 8 hours, and then calcined at 550°C for 5 hours to remove the template HAD, obtaining the product K / Na-ZSM-48 molecular sieve.

[0055] (2) Synthesis of Cu / K / Na-ZSM-48 catalyst: 1.96 g of CuSO4·5H2O was dissolved in 10 mL of ultrapure water and stirred to completely dissolve. 5 g of the product obtained in step (1) was added to the impregnation solution and stirred at 80°C for 4 hours, then allowed to stand for 12 hours, and then dried in an oven at 110°C for 6 hours, and then transferred to a muffle furnace and calcined at 550°C for 5 hours to remove the template agent HAD, thereby obtaining the product Cu / K / Na-ZSM-48 catalyst.

[0056] (3) The prepared Cu / K / Na-ZSM-48 catalyst was placed in a catalytic reactor, and the catalytic performance of the catalyst was evaluated according to the method of step (3) in Example 1. The results are shown in Table 1.

[0057] Example 5 (1) Preparation of K / Na-ZSM-48 molecular sieve: Under stirring conditions, 0.6 g (0.015 mol) NaOH and 0.8415 g (0.015 mol) KOH were added to 90 mL deionized water and stirred until completely dissolved. 4.34 g HAD was added and stirred thoroughly. 0.2 g pseudo-boehmite was added and stirred until the mixed solution became clear and transparent. Then 37.5 g silica sol was slowly added. After stirring at room temperature for 2 hours, 0.75 g ZSM-48 was added as a seed crystal and stirred evenly to obtain a synthetic gel. The synthesized gel was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and crystallized at 160°C for 2 days. The product was filtered, washed, dried in an oven at 110°C for 8 hours, and then calcined at 550°C for 5 hours to remove the template HAD, obtaining the product K / Na-ZSM-48 molecular sieve.

[0058] (2) Synthesis of Zn / K / Na-ZSM-48 catalyst: Dissolve 1.96 g ZnSO4 in 10 mL ultrapure water and stir to completely dissolve. Add 5 g of the product obtained in step (1) to the impregnation solution, stir at 80°C for 4 hours, and then stand for 12 hours. After rotary evaporation, place in an oven at 110°C for 6 hours, transfer to a muffle furnace and calcine at 550°C for 5 hours to remove the template agent HAD, and obtain the product Zn / K / Na-ZSM-48 catalyst.

[0059] (3) The prepared Zn / K / Na-ZSM-48 catalyst was placed in a catalytic reactor, and the catalytic performance of the catalyst was evaluated according to the method of step (3) in Example 1. The results are shown in Table 1.

[0060] Example 6 (1) Preparation of K / Na-ZSM-48 molecular sieve: Under stirring conditions, 0.6 g (0.015 mol) NaOH and 0.8415 g (0.015 mol) KOH were added to 90 mL deionized water and stirred until completely dissolved. 4.34 g HAD was added and stirred thoroughly. 0.2 g pseudo-boehmite was added and stirred until the mixed solution became clear and transparent. Then 37.5 g silica sol was slowly added. After stirring at room temperature for 2 hours, 0.75 g ZSM-48 was added as a seed crystal and stirred evenly to obtain a synthetic gel. The synthesized gel was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and crystallized at 160°C for 2 days. The product was filtered, washed, dried in an oven at 110°C for 8 hours, and then calcined at 550°C for 5 hours to remove the template HAD, obtaining the product K / Na-ZSM-48 molecular sieve.

[0061] (2) Synthesis of Cu-Zn / K / Na-ZSM-48 catalyst: 1.82 g CuSO4·5H2O and 0.14 g ZnSO4 (the total mass of the two is 1.96 g, and the mass ratio is 13:1) are dissolved in 10 mL ultrapure water and stirred to completely dissolve. 5 g of the product obtained in step (1) is added to the impregnation solution and stirred at 80°C for 4 hours, then allowed to stand for 12 hours, and then dried in an oven at 110°C for 6 hours, and then transferred to a muffle furnace and calcined at 550°C for 5 hours to remove the template agent HAD, thereby obtaining the product Cu-Zn / K / Na-ZSM-48 catalyst.

[0062] (3) The prepared Cu-Zn / K / Na-ZSM-48 catalyst was placed in a catalytic reactor, and the catalytic performance of the catalyst was evaluated according to the method of step (3) in Example 1. The results are shown in Table 1.

[0063] Comparative Example 1 (1) Preparation of Na-ZSM-48 molecular sieve: Under stirring conditions, 1.2 g (0.03 mol) of NaOH was added to 90 mL of deionized water and stirred until completely dissolved. Then 4.34 g of H2N(CH2)6NH2 (HAD, hexamethylenediamine) was added. After sufficient stirring, 0.2 g of pseudo-boehmite was added. After stirring until the mixed solution became clear and transparent, 37.5 g of silica sol was slowly added. After the mixture was stirred at room temperature for 2 hours, a synthetic gel was obtained. The synthesized gel was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and crystallized at 160°C for 10 days (since no seed crystal was used, the crystallization time was extended). The crystallized product was filtered, washed with ethanol and ultrapure water, dried in an oven at 110°C for 8 hours, and then calcined at 550°C for 5 hours to remove the template HAD, thereby obtaining the product Na-ZSM-48 molecular sieve.

[0064] (2) Synthesis of Cu / Na-ZSM-48 catalyst: 1.96 g of CuSO4·5H2O was dissolved in 10 mL of ultrapure water and stirred to completely dissolve. 5 g of the product obtained in step (1) was added to the above impregnation solution and stirred at 80°C for 4 hours, then allowed to stand for 12 hours, and then dried in an oven at 110°C for 6 hours after rotary evaporation. The mixture was then transferred to a muffle furnace and calcined at 550°C for 5 hours at a calcination rate of 2°C / min to obtain a Cu / Na-ZSM-48 catalyst.

[0065] (3) The prepared Cu / Na-ZSM-48 catalyst was placed in a catalytic reactor, and the catalytic performance of the catalyst was evaluated according to the method of step (3) in Example 1. The results are shown in Table 1.

[0066] Comparative Example 2 (1) Preparation of Cu / Al2O3 catalyst: Al2O3 was calcined at 550°C in a muffle furnace for 2 hours to remove adsorbed water and impurities. 1.96 g of CuSO4·5H2O powder was weighed and dissolved in 5 mL of ultrapure water to prepare a copper sulfate solution. Then, the copper sulfate solution was added dropwise to 5 g of the calcined Al2O3 and stirred thoroughly. Then, it was placed in an oven at 110°C for 10 hours to remove moisture. Then, it was transferred to a muffle furnace and calcined at 550°C for 5 hours to obtain a Cu / Al2O3 catalyst.

[0067] (2) The prepared Cu / Al2O3 catalyst was placed in a catalytic reactor, and the catalytic performance of the catalyst was evaluated according to the method of step (3) in Example 1.

[0068] Comparative Example 3 (1) Preparation of Cu / ZSM-5 catalyst: 1.96 g of CuSO4·5H2O was dissolved in 10 mL of ultrapure water and stirred to completely dissolve it to prepare an impregnation solution. 5 g of ZSM-5 molecular sieve was added and stirred at 80°C for 4 hours, then allowed to stand for 12 hours. After rotary evaporation to dryness, the mixture was placed in an oven at 110°C for 6 hours, and then transferred to a muffle furnace and calcined at 550°C for 5 hours to obtain a Cu / ZSM-5 catalyst.

[0069] (2) The prepared Cu / ZSM-5 catalyst was placed in a catalytic reactor, and the catalytic performance of the catalyst was evaluated according to the method of step (3) in Example 1.

[0070] Comparative Example 4 (1) Preparation of Cu / ZSM-22 catalyst: 1.96 g of CuSO4·5H2O was dissolved in 10 mL of ultrapure water and stirred to completely dissolve it to prepare an impregnation solution. 5 g of ZSM-22 molecular sieve was added and stirred at 80°C for 4 hours, then allowed to stand for 12 hours. After rotary evaporation to dryness, it was placed in an oven at 110°C for 6 hours and then transferred to a muffle furnace and calcined at 550°C for 5 hours.

[0071] (2) The prepared Cu / ZSM-22 catalyst was placed in a catalytic reactor, and the catalytic performance of the catalyst was evaluated according to the method of step (3) in Example 1.

[0072] The catalytic performance test results of each embodiment and comparative example are shown in Table 1.

[0073] Table 1: Catalytic performance test results of catalysts test Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 CO2 conversion rate (%) 16.8 15.9 16.6 18.9 5.2 20.4 14.1 6.3 14.6 11.2 CO selectivity (%) 8.7 8.1 8.6 7.8 38.7 5.7 10.3 58.7 14.5 19.9 CH4 selectivity (%) 5.6 6.8 5.0 4.4 24.6 4.1 9.5 10.1 9.0 14.3 Methanol selectivity (%) 54.3 53.7 40.2 43.7 30.3 46.8 44.7 22.8 38.2 39.0 Ethanol selectivity (%) 20.8 20.0 30.9 28.6 5.5 27.6 23.9 5.0 24.9 20.6 C3+ alcohol selectivity (%) 10.6 11.4 15.3 15.5 0.9 15.8 11.6 3.4 13.4 6.2 Total alcohol selectivity (%) 85.7 85.1 86.4 87.8 36.7 90.2 80.2 31.2 76.5 65.8 Combined with the test results in Table 1, it can be seen that the molecular sieve supported metal catalyst prepared by the present invention has a significant effect on methanol, ethanol, C3 + Low-carbon alcohols such as ethanol have good selectivity, high catalytic CO2 conversion rate, and good catalytic effect in the synthesis of low-carbon alcohols.

[0074] According to the test results of Examples 1 and 3 in Table 1, it can be seen that the sodium-type or potassium-type molecular sieve-loaded metal catalyst prepared by combining potassium- or sodium-containing alkali sources with ZSM-48 molecular sieves has good selectivity for low-carbon alcohols. The catalyst prepared from the potassium-containing alkali source has better total alcohol selectivity, while the catalyst prepared from the sodium-containing alkali source has better selectivity for methanol.

[0075] According to the test results of Examples 1, 3, and 4 in Table 1, the catalyst prepared by containing both sodium and potassium in the alkali source has a higher total alcohol selectivity, and the two promote each other to improve the total alcohol selectivity and CO2 conversion rate.

[0076] According to the test results of Examples 4-5 in Table 1, the effect of the catalyst prepared by the water-soluble salt containing zinc is poorer than that of the water-soluble salt containing copper; and according to the comparison of Examples 4-6, when the total amount of water-soluble salt is kept unchanged, the catalytic CO2 conversion rate of Example 6 of the catalyst prepared by the water-soluble salt containing copper and zinc is higher, and the methanol, C3 + The selectivity of alcohol and total alcohol is higher.

[0077] According to the comparison between Example 1 and Comparative Examples 1-2 in Table 1, it can be seen that when the catalyst is prepared without using ZSM-48 seeds or without using ZSM-48 to prepare the catalyst, the catalytic CO2 conversion rate is low and the total alcohol selectivity efficiency is low.

[0078] According to the comparison between Example 1 and Comparative Examples 3-4 in Table 1, it can be seen that the catalysts prepared by using other types of molecular sieves are inferior to the molecular sieve-loaded metal catalysts prepared by using ZSM-48 as the seed to obtain the A-ZSM-48 molecular sieve; ZSM-48 as the seed to prepare the molecular sieve-loaded metal catalyst is more suitable for the preparation system of the present invention and the obtained catalyst has excellent effect.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the invention has been described in detail with reference to the aforementioned embodiments, it is still possible for a person skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to replace some of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions claimed to be protected by the present invention.

Claims

1. A method for preparing a molecular sieve-supported metal catalyst, characterized in that: The steps include: Step (1), preparing A-ZSM-48 molecular sieve: mixing an alkali source containing A with water, adding a template agent and mixing, then adding an aluminum source and mixing, then adding a silicon source and mixing, adding ZSM-48 as a seed crystal and mixing, then placing in an autoclave at 140-180° C. for crystallization for 40-80 hours, filtering, washing, drying, and calcining at 500-600° C. for 3-7 hours to obtain A-ZSM-48 molecular sieve; Wherein, A includes at least one of potassium or sodium; the alkali source containing A includes at least one of hydroxide, carbonate and bicarbonate containing A; Step (2), preparing a modified liquid: adding water to a water-soluble salt containing B and mixing to obtain a modified liquid; Wherein, B is at least one of Cu, Zn, Fe, Co, Pt, and Ru, and the water-soluble salt containing B includes at least one of a sulfate or chloride containing B; Step (3), preparing a molecular sieve-supported metal catalyst: the A-ZSM-48 molecular sieve prepared in step (1) is mixed with the modified liquid prepared in step (2), concentrated, dried, and then transferred to a muffle furnace for calcination at 500-600° C. for 3-7 hours to obtain a molecular sieve-supported metal catalyst.

2. The preparation method according to claim 1, characterized in that: The template agent includes at least one of hexamethylenediamine, 1,6-pentanediamine, 1,8-octanediamine, hexamethyldiammonium bromide, and dimethylbiscyclohexylammonium hydroxide; and / or, the aluminum source includes at least one of aluminum oxyhydroxide, sodium aluminate, pseudo-boehmite, and aluminum sulfate; And / or, the silicon source includes at least one of silica sol, fumed silica, macroporous silica gel, tetraethyl orthosilicate, and sodium silicate.

3. The preparation method according to claim 1, characterized in that: The alkali source containing A includes sodium hydroxide and potassium hydroxide in a molar ratio of 1: (0.9-1.3).

4. The preparation method according to claim 1, characterized in that: In step (2), the ratio of the water-soluble salt containing B to water is 1-3 g: 8-15 mL; And / or, in step (3), the mass ratio of A-ZSM-48 molecular sieve to modifying liquid is 4-6 g:10-20 g.

5. The preparation method according to claim 1, characterized in that: Step (1) is: Mix 1-3 g of an alkali source containing A with 80-120 mL of water, add 3-6 g of a template and mix, then add 0.1-0.5 g of an aluminum source and mix, then add 30-50 g of a silicon source and mix, and finally add 0.5-1 g of ZSM-48 as a seed crystal and mix, then place in an autoclave at 140-180 ° C for crystallization for 40-80 hours, filter, wash, dry, and calcine at 500-600 ° C for 3-7 hours to obtain an A-ZSM-48 molecular sieve.

6. The preparation method according to claim 1, characterized in that: The water-soluble salt containing B includes copper sulfate pentahydrate and zinc sulfate in a mass ratio of 9-15:

1.

7. The preparation method according to claim 1, characterized in that: The calcination heating rate in step (3) is 1.5-2.5°C / min.

8. A molecular sieve-supported metal catalyst prepared according to the preparation method according to any one of claims 1 to 7.

9. Use of the molecular sieve-supported metal catalyst according to claim 8 in catalyzing the hydrogenation of carbon dioxide to produce lower alcohols.

10. The use according to claim 9, characterized in that: The application steps include: making the molecular sieve-loaded metal catalyst into particles, loading them in a catalytic reactor, and reducing the particles with a hydrogen atmosphere; then sending a mixed gas consisting of hydrogen, carbon dioxide and nitrogen into the reactor for catalytic reaction, and controlling the catalytic reaction pressure, temperature and mixed gas flow rate to prepare low-carbon alcohols.

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