Cu-based catalyst supported on mgal layered double hydroxide, preparation method thereof and application of the catalyst in preparation of low-carbon alcohol from biomass synthesis gas in-situ adsorbed with co2

Abstract

The application discloses a MgAl layered double metal oxide supported Cu-based catalyst and a preparation method thereof and application of the catalyst in preparation of low-carbon alcohols from biomass synthesis gas in-situ adsorption of CO2. The catalyst is prepared by using modified MgAl-LDH powder prepared by co-modification of polymethyl methacrylate and calcium oxide as a carrier and Cu-based multi-metal oxide as an active component, and the catalyst has high total carbon conversion (20% to 30%) and high low-carbon alcohol yield (≥60%) in the reaction of preparing low-carbon alcohols from biomass synthesis gas, by virtue of high adsorption of CO2 of MgAl layered double metal oxide obtained after calcination of the catalyst and high dispersion of Cu-based multi-metal oxide on the carrier. The catalyst preparation method is simple, low in cost and easy to realize large-scale preparation, and provides an ideal selection for industrial production of low-carbon alcohols from biomass synthesis gas.

Description

Technical Field

[0001] This invention relates to the field of low-carbon alcohol synthesis technology, and in particular to Cu-based catalysts supported on MgAl layered bimetallic oxides, their preparation methods, and their application in the in-situ adsorption of CO2 to enhance the preparation of low-carbon alcohols from biomass syngas. Background Technology

[0002] Low-carbon mixed alcohols (hereinafter referred to as low-carbon alcohols) refer to liquid mixtures composed of C1-C5 alcohols. They can be used as gasoline additives and clean fuels, and can be separated to obtain basic chemical raw materials such as methanol, ethanol, propanol, butanol, and pentanol. Furthermore, low-carbon alcohols are also important hydrogen carriers (methanol, ethanol, and propanol contain 12.5%, 13.0%, and 13.3% hydrogen, respectively), possessing characteristics such as safe storage and transportation, and easy flow at low temperatures. Their market application potential is enormous, especially with the steady advancement of dual-carbon policies; developing the low-carbon alcohol fuel transportation industry is of great significance for achieving the goal of "carbon peaking and carbon neutrality." Currently, low-carbon alcohols are mainly produced from traditional fossil fuels such as petroleum, coal, and natural gas. With the decreasing availability of fossil fuels and the serious carbon emissions from traditional low-carbon alcohol production processes, there is an urgent need to find renewable alternative raw materials and develop new green, low-carbon, economical, and efficient low-carbon alcohol synthesis pathways.

[0003] In recent years, the production of green low-carbon alcohols (referred to as green alcohols) by coupling syngas (H2 / CO / CO2) obtained from renewable biomass gasification or carbon dioxide (CO2) directly captured from the air with green hydrogen (H2) produced by renewable energy power generation and water electrolysis has been extensively studied. Syngas obtained from traditional biomass gasification processes typically requires gas reforming to increase the hydrogen-to-carbon ratio (H2-CO2) / (CO+CO2) of the syngas, thus meeting the requirements for green alcohol synthesis. Steam gasification can significantly increase the H2 content in the syngas, improving the hydrogen-to-carbon ratio. Our team's patent CN117106485A discloses a method for producing hydrogen-rich biomass syngas by coupling biomass through catalytic cracking, steam reforming, and water-gas shift reaction, achieving a hydrogen content as high as 90%, greatly reducing process complexity and significantly enhancing the utilization value of biomass syngas. Based on this, our team's patent CN118767924A discloses a metal oxide-promoted CuO-ZnO-Al2O3 nanocatalyst with highly dispersed multiple interfacial active sites, which can achieve efficient conversion of biomass syngas into methanol.

[0004] Compared to CO, CO2 possesses thermodynamic stability and chemical inertness, making the development of highly efficient catalysts crucial for the hydrogenation of CO2 to lower alcohols. Cu-based catalysts, such as Cu / ZnO, Cu / ZrO2, and Cu / ZnO / Al2O3, exhibit good catalytic activity for CO2 conversion and are considered the most promising catalysts for industrial applications. However, Cu-based catalysts still suffer from problems such as low CO2 conversion rate and methanol selectivity, and poor catalyst stability due to the generation of a large amount of water as a byproduct in the reverse water-gas shift reaction. This is especially true for biomass syngas conversion, which contains both CO and CO2, where the conversion tends to favor CO over CO2. To improve the performance of Cu-based catalysts in the CO2 hydrogenation to methanol production, Chinese patent CN103263926A discloses a metal oxide catalyst formed by high-temperature calcination of a hydrotalcite-like compound as a precursor. Subsequently, Chinese patent ZL201810864352.X disclosed a CO2 hydrogenation catalyst based on adsorption enhancement, which uses activated commercial hydrotalcite compounds as a support and multi-metal oxides as loading materials, utilizing the gas adsorption of the support and its synergistic effect with the surface loading materials to improve methanol selectivity. Physically mixing Cu / ZnO / Al2O3 with MgAl-LDHs at the powder level can also improve the yield of CO2 adsorption-enhanced in-situ hydrogenation to methanol (Chemical Engineering Journal, 2019, 378: 122052). However, the hydrotalcites used in the prior art are all commercial hydrotalcites with low specific surface area and pore volume, resulting in very limited CO2 adsorption capacity and CO2 conversion rates often below 10%.

[0005] Layered bimetallic oxides (MgAl-LDOs), obtained by calcining MgAl layered bimetallic hydroxides (MgAl-LDHs), have a surface rich in basic sites and are typical hydrotalcite-like medium-temperature (200℃~400℃) CO2 adsorbents. To enhance the CO2 adsorption performance and stability of MgAl-LDOs, researchers have attempted to optimize the structure of MgAl-LDHs through methods such as layer exfoliation (Inorganic Chemistry, 2020, 59: 17722), cation substitution, alkali doping (RSC Advances, 2013, 3: 3414), composite material construction (Chemistry of Materials, 2012, 24: 4531), and improvement of preparation methods (Journal of Hazardous materials, 2019, 373: 285), achieving some progress. Among these methods, combining MgAl-LDH with porous carbon materials such as graphene (GO) and carbon nanotubes (CNTs) to form composite materials and regulating the exfoliation and dispersion of MgAl-LDH can enhance the CO2 adsorption performance of MgAl-LDO. However, the high cost of these carbon materials limits the industrial application of MgAl-LDO. Therefore, developing low-cost, high-performance MgAl-LDO adsorbents is crucial for improving in-situ CO2 adsorption and enhancing the performance of biomass syngas conversion to low-carbon alcohols. Summary of the Invention

[0006] This invention addresses the problems of poor CO2 adsorption capacity and low CO2 conversion rate in existing CO2 adsorption-enhanced CO2 hydrogenation catalysts for producing low-carbon alcohols, and the difficulty in achieving efficient co-conversion of CO and CO2 from biomass syngas to low-carbon alcohols. It provides a Cu-based catalyst supported on a MgAl layered bimetallic oxide, its preparation method, and its application in the in-situ CO2 adsorption-enhanced biomass syngas production of low-carbon alcohols. This invention utilizes PMMA and MgAl-LDH to form a PMMA-modified MgAl-LDH composite material with an organic-inorganic interpenetrating network structure. The pore-forming effect generated by the combustion degradation of PMMA increases the specific surface area and pore volume of MgAl-LDO. Simultaneously, CaO doping enhances the CO2 adsorption capacity of MgAl-LDO.

[0007] The purpose of this invention is to provide a Cu-based catalyst supported on a MgAl layered bimetallic oxide, wherein the compositional formula of the catalyst is: (Cu x Zn y Al z M m+ n O x+y+1.5z+0.5m*n ) w @[Mg a Al b(OH) c (CO3) d O a+1.5b-0.5c-d •CaO, where M m+ M is a doped metal cation, selected from Ce. 4+ Zr 4+ and Ti 4+ One of them; x, y, z, n, a, b, c are all molar contents, and 2x+2y+2.5z+(1+0.5m)n=1, x / y=1~2, n≥0, 2a+2.5b+0.5c=1, a / b=2~10; w is the loading amount of Cu-based multi-metal oxide, w=60~90 wt%.

[0008] Preferably, the value of x ranges from 0.05 to 0.30, the value of y ranges from 0.02 to 0.15, and the value of z ranges from 0.005 to 0.020.

[0009] Further optimization is made, the value of x is in the range of 0.05~0.10, and x:y:z:n =1:1:0.2:0.05~2:1:0.2:0.05.

[0010] This invention also protects the preparation method of the Cu-based catalyst supported by the MgAl layered bimetallic oxide (MgAl-LDO•CaO). The modified MgAl-LDH powder (MgAl layered bimetallic hydroxide) prepared by co-modification of polymethyl methacrylate (PMMA) and calcium oxide (CaO) is used as the support, and Cu-based multi-metallic oxide is used as the active component. The catalyst precursor is prepared by co-precipitation, and then calcined to obtain the Cu-based catalyst supported by the MgAl layered bimetallic oxide MgAl-LDO•CaO.

[0011] This invention addresses the problems of low specific surface area and pore volume, poor CO2 adsorption capacity, and insignificant effect of CO2 adsorption enhancement on CO2 hydrogenation to produce low-carbon alcohols by commercially available hydrotalcites. Furthermore, traditional Cu-based catalysts struggle to achieve efficient co-conversion of CO and CO2 from biomass syngas to low-carbon alcohols. First, polymethyl methacrylate (PMMA), prepared by in-situ emulsion polymerization, is used as a structure modifier, and CaO is used as an adsorption enhancer to regulate the microstructure of MgAl-LDH and enhance its CO2 adsorption capacity, thereby significantly improving the mid-temperature CO2 adsorption performance of the calcined MgAl-LDO•CaO. Then, modified MgAl-LDH is used as a support, and Cu-based multi-metal oxides are used as the active component to construct a Cu-based nanocatalyst with highly dispersed multi-interfacial active sites, while simultaneously introducing Ce. 4+ Zr 4 + Ti 4+Metal cations increase the oxygen vacancy concentration, further promoting the adsorption and activation of CO2 in biomass syngas and the formation and conversion of alcohol intermediates, thus achieving efficient production of low-carbon alcohols from biomass syngas.

[0012] Preferably, the preparation method specifically includes the following steps:

[0013] S1. PMMA microspheres were prepared by in-situ emulsion polymerization.

[0014] S2: Modified MgAl-LDH powder was prepared by co-precipitation using PMMA microspheres prepared in step S1 as a structure regulator and CaO as an adsorption enhancer.

[0015] S3: The modified MgAl-LDH powder prepared in step S2 is used as a support and Cu-based multi-metal oxide is used as an active component to prepare a catalyst precursor by co-precipitation method, and then calcined to obtain a Cu-based catalyst supported by MgAl layered bimetallic oxide MgAl-LDO•CaO.

[0016] Further optimized, step S1 specifically involves: adding methyl methacrylate, potassium persulfate, sodium bicarbonate, deionized water, sodium dodecyl sulfate, and emulsifier OP-10 sequentially into a reaction vessel; mixing at room temperature and then heating to 70°C~80°C for polymerization reaction for 3~6 hours; cooling to below 50°C and filtering to obtain a white PMMA emulsion; demulsifying the PMMA emulsion with aluminum sulfate aqueous solution to obtain a solid product; washing with water and drying to finally obtain PMMA microspheres; wherein the mass ratio of methyl methacrylate to deionized water is 1:(1.5~5); the amount of potassium persulfate is 0.2%~1.0% of methyl methacrylate; the amount of sodium bicarbonate is 0.1%~0.5% of methyl methacrylate; the amount of sodium dodecyl sulfate is 1%~3% of methyl methacrylate; and the amount of emulsifier is 1%~3% of methyl methacrylate.

[0017] Further optimization, the specific steps of step S1 are as follows: Methyl methacrylate, potassium persulfate, sodium bicarbonate, deionized water, sodium dodecyl sulfate, and emulsifier OP-10 are added sequentially to the reaction vessel. After ultrasonic vibration at room temperature for 20-40 min, the mixture is heated to 75±0.5℃ and polymerized for 3-6 hr. The temperature is then lowered to below 50℃, and the mixture is filtered through a standard sieve of >80 mesh to obtain a white PMMA emulsion. The PMMA emulsion is then demulsified with a 10% aluminum sulfate aqueous solution to obtain a solid product. The product is then washed repeatedly with deionized water and dried in an oven at 80℃ for 12-24 hr to finally obtain PMMA microspheres.

[0018] Further optimization, the specific steps of step S2 are as follows: calcium oxide powder and the PMMA microspheres obtained in step S1 are uniformly dispersed in deionized water to form suspension A1, and Mg is prepared.2+ And Al 3+ A mixed aqueous solution B1 was prepared by dissolving the precipitant in water to form solution C1. Solutions B1 and C1 were simultaneously added dropwise to solution A1 at room temperature for co-precipitation to obtain solution D1. The pH of solution D1 was controlled at 9.0–9.5. After stirring and aging at room temperature for 8–24 hours, the solution was filtered, washed, and dried to form modified MgAl-LDH•CaO powder. The amount of CaO added was [missing information - likely a percentage] of MgAl. a Al b (OH) c (CO3) d O a+1.5b-0.5c-d (i.e., MgAl-LDH) mass 2%~10%, PMMA microspheres added amount is Mg a Al b (OH) c (CO3) d O a+1.5b-0.5c-d The weight is 10% to 50%, and the drying temperature is 80 to 120℃.

[0019] Further optimization, the specific steps of step S3 are as follows: the modified MgAl-LDH•CaO powder obtained in step S2 is uniformly dispersed in deionized water to form suspension A2, and Cu is prepared. 2+ Zn 2+ Al 3+ A mixed aqueous solution B2 containing doped metal cations was prepared by dissolving the precipitant in water to form solution C2. Solutions B2 and C2 were simultaneously added dropwise to solution A2 at 60℃~70℃ for co-precipitation to obtain solution D2. The pH of solution D2 was controlled at 9.0~9.5. The solution was then stirred and aged at 80℃~90℃ for 3~6 hours, followed by filtration, washing, drying, and calcination to obtain a Cu-based catalyst supported on a MgAl layered bimetallic oxide (MgAl-LDO•CaO). MgAl-LDO•CaO comprised 10%~40% of the mass of the Cu-based catalyst supported on the MgAl layered bimetallic oxide, and the mass ratio of modified MgAl-LDH•CaO powder to MgAl-LDO•CaO was 1.5~2:1. The calcination atmosphere was air, the calcination temperature was 450℃~550℃, the calcination time was 3~5 hours, and the heating rate was 1~10℃ / min.

[0020] Further optimization involves a modified MgAl-LDH•CaO powder addition amount to a mass ratio of 5 / 3 to 20 / 11 to MgAl-LDO•CaO. The amount of modified MgAl-LDH•CaO powder added is calculated based on a mass loss of 40% to 45% during the calcination process to form MgAl-LDO•CaO, and the fact that MgAl-LDO•CaO accounts for 10% to 40% of the mass of the Cu-based catalyst supported on the MgAl layered bimetallic oxide.

[0021] Further optimization, in step S2, Mg 2+ And Al 3+ The molar ratio is 2:1 to 10:1, the total concentration is 0.5 to 2.0 mol / L, and the anion is nitrate or chloride ion; the precipitant is a combination of sodium carbonate and sodium hydroxide or a combination of potassium carbonate and potassium hydroxide, and CO3... 2－ and OH － The molar ratio is 0.3:1 to 1:1, and the total concentration is 0.5 to 2.0 mol / L.

[0022] Further optimization, in step S3, Cu 2+ Zn 2+ Al 3+ The molar ratio of the doped metal cation to the nitrate cation is 1:1:0.2:0.05~2:1:0.2:0.05, the total concentration is 0.5~3.0 mol / L, the anion is nitrate ion or chloride ion; the precipitant is a combination of sodium carbonate and sodium hydroxide or a combination of potassium carbonate and potassium hydroxide, CO3 2－ and OH － The molar ratio is 0.3:1 to 1:1, and the total concentration is 0.5 to 3.0 mol / L.

[0023] This invention also protects the application of the catalyst in the in-situ adsorption of CO2 to enhance the preparation of lower alcohols from biomass syngas. The catalyst is loaded into a reactor and reduced in a hydrogen atmosphere at 220°C–300°C for 2–20 hours. After reduction, biomass syngas is introduced at a reaction pressure of 2–8 MPa and a volume hourly space velocity of 2000–10000 h⁻¹. -1 The low-carbon alcohols are synthesized under the following conditions: the composition of the biomass syngas is as follows (by volume fraction): H2 65%–75%, CO2 15%–20%, CO 5%–10%, and CH4 2%–5%. The low-carbon alcohol synthesis proposed in this invention is carried out in a fixed-bed reactor, specifically by pressing, crushing, and sieving the catalyst powder before loading it into the fixed-bed reactor.

[0024] Preferably, the hydrogen atmosphere is pure H2 or a 10% H2 / N2 mixture.

[0025] Preferably, the biomass is selected from at least one of sugarcane bagasse, straw, bamboo shavings, wood chips, branches, bark, kitchen waste, and livestock and poultry manure. For biomass syngas preparation, see CN117106485A.

[0026] Preferably, the reaction temperature is 220℃~250℃, the syngas pressure is 2~6 MPa, and the volume hourly space velocity is 2000~6000 h⁻¹. -1 .

[0027] Compared with existing technologies, this invention has the following advantages: The catalyst for enhancing the in-situ adsorption of CO2 in biomass syngas to produce low-carbon alcohols provided by this invention utilizes PMMA and MgAl-LDH to form a PMMA-modified MgAl-LDH composite material with an organic-inorganic interpenetrating network structure. After calcination in air, the pore-forming effect generated by the combustion degradation of PMMA is utilized to increase the specific surface area and pore volume of MgAl-LDO. Simultaneously, CaO doping enhances the CO2 adsorption capacity of MgAl-LDO. Furthermore, by doping Cu-based multi-metal oxides with Ce... 4+ Zr 4+ Ti 4+ The formation of reducible oxides by metal cations increases the oxygen vacancy concentration of the catalyst, promotes the adsorption and activation of CO2 in biomass syngas, and the formation and conversion of intermediates in the synthesis of low-carbon alcohols. This allows the catalyst to maintain a high yield of low-carbon alcohols (≥60%) even under conditions of high total carbon (CO+CO2) conversion (20%~30%). Furthermore, the catalyst preparation method is simple, low-cost, and easy to achieve large-scale production, providing an ideal choice for the industrial production of low-carbon alcohols from biomass syngas. Attached Figure Description

[0028] Figure 1 This is a scanning electron microscope image of the MgAl-LDH•CaO adsorbent precursor prepared according to Example 1.

[0029] Figure 2 The image shows a scanning electron microscope (SEM) image of the MgAl-LDO•CaO adsorbent prepared according to Example 1.

[0030] Figure 3 The adsorption curves of CO2 after calcination and activation of the MgAl-LDO•CaO adsorbent prepared according to Example 1 are shown.

[0031] Figure 4 Scanning electron microscope (SEM) image of the CuZnCeAl@MgAl-LDO•CaO catalyst prepared according to Example 1. Detailed Implementation

[0032] The following embodiments are further illustrations of the present invention, but not limitations thereof.

[0033] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention. Unless otherwise specified, the experimental materials and reagents used herein are commercially available products conventionally available in this field.

[0034] This invention verifies through numerous experiments that the addition of PMMA can significantly improve the dispersion of the MgAl-LDH precursor, reduce the size of MgAl-LDH nanosheets, increase the specific surface area of ​​calcined MgAl-LDO, and expose more Mg-O adsorption active sites. Compared with commercially available hydrotalcite-like compounds after calcination and activation, the CO2 adsorption capacity obtained by thermogravimetric analysis is stronger and the adsorption rate is faster, which is more conducive to enhancing the hydrogenation activity of CO2 in the modified MgAl-LDO supported Cu-based catalyst.

[0035] Based on the preparation of modified MgAl-LDH, it is used as a support to support Cu-based multi-metal oxides to form a catalyst with metal-metal interface and metal-oxide interface, which endows the catalyst with good metal dispersion and strong synergistic effect between interfacial active sites, thereby enhancing the conversion of biomass syngas to low carbon alcohols through in-situ efficient adsorption of CO2.

[0036] The preparation of low-carbon alcohols from biomass syngas was carried out in a micro fixed-bed reactor with an inner diameter of 8 mm and a length of 200 mm. First, catalyst particles were loaded into the middle of the reactor. Pure hydrogen or a hydrogen / nitrogen mixture was introduced and reduced at 220℃~300℃ for 2~20 hours. Then, syngas was introduced to establish system back pressure, and the reaction temperature was set and gradually increased. The reaction products were separated into gas and liquid phases via a cold trap. The tail gas was analyzed online using a GC 9800 gas chromatograph (Shanghai Kechuang) with Ar as the carrier gas (flow rate 30 mL / min) and detected by a thermal conductivity detector (TCD). A TDX-01 (2 m × 3 mm) carbon molecular sieve column was used. After the reaction, the liquid products were collected and analyzed offline using an Agilent 7890 gas chromatograph with a flame ionization detector (FID) and an FFAP capillary column (30 m × 0.25 mm × 0.25 μm) using Ar as the carrier gas (flow rate 30 mL / min).

[0037] Based on the content of each component in the reaction tail gas, the total carbon conversion rate and the yield of lower alcohols in the syngas are calculated using the number of moles of carbon atoms. The calculation formula is as follows:

[0038] Total carbon conversion (%) = [n(CO)in + n(CO2)in - n(CO)out - n(CO2)out] / [n(CO)in + n(CO2)in]

[0039] CO2 conversion rate (%) = [n(CO2)in-n(CO2)out] / [n(CO2)in]

[0040] Lower alcohol yield (%) = m(liquid) × w(ROH) / [m(H2+CO+CH4+CO2)in-m(H2+CO+CH4+CO2)out]

[0041] In the formula, n(CO)in, n(CO2)in and n(CO)out, n(CO2)out are the moles of CO and CO2 in the feed gas and tail gas, respectively, in mol; m(liquid) is the mass of the liquid product collected in the cold trap, in g; w(ROH) is the total mass concentration of lower alcohols in the liquid product as determined by gas chromatography, in wt%; m(H2+CO+CH4+CO2)in and m(H2+CO+CH4+CO2)out are the H2+CO+CH4+CO2 ... 2、 The total mass of the four components: CO, CH4, and CO2.

[0042] Example 1

[0043] Preparation and application of CuZnAlCe@MgAl-LDO•CaO catalyst:

[0044] (1) PMMA preparation: 60 g of methyl methacrylate, 0.3 g of potassium persulfate, 0.3 g of sodium bicarbonate, 300 g of deionized water, 1.5 g of sodium dodecyl sulfate and 1 g of emulsifier OP-10 were weighed and added to a four-necked flask. After ultrasonic vibration at room temperature for 30 min, the mixture was heated to 75±0.5 ℃ and polymerized for 4 hr. After cooling to below 50 ℃, the mixture was filtered through a standard sieve with a mesh size of >80 to obtain a white PMMA emulsion. The PMMA emulsion was demulsified with a 10% aluminum sulfate aqueous solution to obtain a solid product. The solid product was then washed repeatedly with deionized water and dried in an oven at 80 ℃ for 12 hr to obtain PMMA microspheres.

[0045] (2) Preparation of PMMA-modified MgAl-LDH•CaO: Weigh 2.42 g of CaO powder and 7.25 g of PMMA microspheres obtained in step (1) and uniformly disperse them in deionized water to form suspension A1. Weigh 61.54 g of magnesium nitrate hexahydrate and 30 g of aluminum nitrate nonahydrate to prepare MgAl-LDH•CaO. 2+ And Al 3+ A mixed aqueous solution B1 with a molar ratio of 3:1 and a total concentration of 1 mol / L, weigh out CO3. 2－ and OH －Sodium carbonate and sodium hydroxide in a 1:1 molar ratio were dissolved in water to prepare a 1 mol / L mixed alkaline solution C1. Solutions B1 and C1 were simultaneously added dropwise to solution A1 at room temperature for co-precipitation to obtain solution D1. The pH of solution D1 was controlled at 9.5. After stirring and aging at room temperature for 24 hours, the solution was filtered, washed, and dried at 100℃ to form PMMA-modified MgAl-LDH•CaO. The amount of CaO added was 10% of the mass of MgAl-LDH, and the amount of PMMA added was 30% of the mass of MgAl-LDH. A portion of the PMMA-modified MgAl-LDH•CaO adsorbent precursor was calcined in air at 500℃ for 4 hours to form MgAl-LDO•CaO adsorbent.

[0046] (3) Preparation of CuZnAlCe@MgAl-LDO•CaO catalyst: 21.6 g of PMMA-modified MgAl-LDH•CaO powder was weighed and uniformly dispersed in deionized water to form suspension A2. 25.64 g of copper nitrate trihydrate, 14.88 g of zinc nitrate hexahydrate, 3.75 g of aluminum nitrate nonahydrate and 1.09 g of cerium nitrate hexahydrate were weighed to prepare CuZnAlCe@MgAl-LDO•CaO catalyst. 2+ Zn 2+ Al 3+ and Ce 4+ A mixed aqueous solution B2 with a molar ratio of 2:1:0.2:0.05 and a total concentration of 1 mol / L, weigh out CO3. 2－ and OH － Sodium carbonate and sodium hydroxide in a molar ratio of 0.5:1 were dissolved in water to prepare a mixed alkaline solution C2 with a concentration of 1.5 mol / L. Solution B2 and solution C2 were simultaneously added dropwise to solution A2 at 70℃ to obtain solution D2 for co-precipitation. The pH of solution D2 was controlled at 9.5. After stirring and aging at 80℃ for 6 hours, the solution was filtered, washed, dried, and then calcined in air at 500℃ for 5 hours at a rate of 5℃ / min from room temperature to obtain the catalyst. The amount of modified MgAl-LDH•CaO powder added was calculated based on the fact that the mass loss during the calcination process to form MgAl-LDO•CaO was 40% and that MgAl-LDO•CaO accounted for 40% of the catalyst mass.

[0047] (4) Biomass syngas to produce low-carbon alcohols: The catalyst powder is pressed into tablets, crushed, and sieved to obtain 40-80 mesh catalyst particles. 1 g of catalyst particles is weighed and loaded into a reactor. After reducing the catalyst with a 10% H2 / N2 mixed gas at 300℃ for 5 h, biomass syngas with a composition of n(H2):n(CO2):n(CO):n(CH4) = 70:20:6:4 is introduced. The reactor is then subjected to a reaction at a temperature of 220℃~300℃, a pressure of 4.0 MPa, and a space velocity of 4000 h⁻¹. -1The reaction was carried out under the following conditions. The results are shown in Table 1. It can be seen that as the reaction temperature increases from 220℃ to 280℃, the total carbon and CO2 conversion rates and the yield of lower alcohols gradually increase. Further increasing the temperature to 300℃ leads to a decrease in the synthesis performance of lower alcohols.

[0048] Table 1 Effect of reaction temperature on the synthesis performance of lower alcohols

[0049] Comparative Example 1:

[0050] Referring to Example 1, in step (2), unmodified MgAl-LDH, PMMA-modified MgAl-LDH (PMMA addition amount is 30% and 40% of the mass of MgAl-LDH respectively) or CaO-modified MgAl-LDH (CaO addition amount is 10% and 40% of the mass of MgAl-LDH respectively) were prepared respectively. Then, commercially available MgAl-LDO activated by calcination at 500℃ for 4 hours, unmodified and PMMA-modified or CaO-modified MgAl-LDH were used as carriers to prepare catalysts according to step (3) of Example 1. They were then crushed, pressed into tablets, and sieved to 40~80 mesh to obtain 40~80 mesh catalyst particles.

[0051] Catalyst particles were loaded into the reactor for the preparation of low-carbon alcohols from biomass syngas. Referring to Example 1, after reducing the catalyst with a 10% H2 / N2 mixture at 300°C for 5 h, biomass syngas with a composition of n(H2):n(CO2):n(CO):n(CH4) = 70:20:6:4 was introduced. The reaction conditions were: temperature 250°C, pressure 4.0 MPa, and space velocity 4000 h⁻¹. -1 Synthesize lower alcohols under specific conditions.

[0052] Table 2 shows a comparison of the low-carbon alcohol synthesis performance of the PMMA-modified MgAl-LDH•CaO supported catalyst. It can be seen that, compared with the activated commercial MgAl-LDO supported catalyst, the unmodified MgAl-LDH supported catalyst prepared in this invention exhibits better low-carbon alcohol synthesis performance. Furthermore, PMMA or CaO-modified MgAl-LDH supported catalysts can further improve the low-carbon alcohol synthesis performance, while the PMMA-modified MgAl-LDH•CaO supported catalyst shows the best low-carbon alcohol synthesis performance, indicating a synergistic effect between PMMA and CaO. Furthermore, increasing the PMMA addition from 30% to 40% had little impact on the synthesis performance of lower alcohols. However, increasing the CaO addition from 10% to 40%, while improving the CO2 and total carbon conversion rates in the syngas, significantly reduced the yield of lower alcohols. This is because while increased CaO enhances CO2 adsorption, excessive CaO promotes the CO2-to-CO side reaction via the reverse water-gas shift reaction, leading to reduced selectivity for lower alcohols. This further demonstrates the synergistic effect of PMMA and CaO in improving the catalyst's performance in lower alcohol synthesis. Figure 1 and Figure 2 It can be seen that the calcined PMMA-modified MgAl-LDO•CaO has smaller nanosheets and more abundant pores compared to the uncalcined PMMA-modified MgAl-LDH•CaO. When Cu-based multi-metal oxides are supported on PMMA-modified MgAl-LDH•CaO, the calcined PMMA-modified MgAl-LDO•CaO catalyst support exhibits higher and faster CO2 adsorption capacity compared to activated commercial MgAl-LDO. Figure 3 Meanwhile, the porosity effect generated by PMMA combustion can improve the dispersion of active sites at the catalyst metal oxide interface and the interaction between the metal and the support, thereby reducing the size of the active metal particles. Figure 4 This improves the performance of low-carbon alcohol synthesis.

[0053] Table 2. Performance of catalysts supported on different supports for the synthesis of low alcohols

[0054] Comparative Example 2:

[0055] PMMA-modified MgAl-LDH•CaO was prepared according to steps (1) and (2) of Example 1 above. Then, the amount of modified MgAl-LDH•CaO powder added in step (3) was changed to obtain CuZnAlZr@MgAl-LDO•CaO catalysts with different MgAl-LDO•CaO contents. These catalysts were then crushed, pressed into tablets, and sieved to 40-80 mesh and loaded into a reactor for the preparation of low-carbon alcohols from biomass syngas. The reaction conditions were: temperature 240℃, pressure 5.0 MPa, and space velocity 4000 h⁻¹. -1 The reaction results are shown in Table 3. It can be seen that with the gradual increase of the modified MgAl-LDH•CaO addition, the total carbon and CO2 conversion rates, as well as the yield of lower alcohols, all first increase and then decrease. This is because the increased content of MgAl-LDO•CaO obtained after calcination of MgAl-LDH•CaO significantly promotes the adsorption of CO2 by the catalyst, increasing the local partial pressure of CO2 on the catalyst surface. Simultaneously, Cu-based multi-metal oxides, as active metal species, can be highly dispersed and efficiently synergistically combined on the MgAl-LDO•CaO support, thus significantly improving the synthesis performance of lower alcohols. However, excessive PMMA-modified MgAl-LDH•CaO content in the catalyst means less active metal for lower alcohol synthesis, leading to a decrease in the synthesis performance of lower alcohols.

[0056] Table 3 Effect of MgAl-LDO•CaO content on the synthesis performance of lower alcohols

[0057] Example 2:

[0058] Preparation and application of CuZnAlZr@MgAl-LDO•CaO catalyst:

[0059] (1) PMMA preparation: 60 g of methyl methacrylate, 0.12 g of potassium persulfate, 0.06 g of sodium bicarbonate, 90 g of deionized water, 0.6 g of sodium dodecyl sulfate and 0.6 g of emulsifier OP-10 were weighed and added to a four-necked flask. After ultrasonic vibration at room temperature for 20 min, the mixture was heated to 75±0.5℃ and polymerized for 3 hr. After cooling to below 50℃, the mixture was filtered through a standard sieve with a mesh size of >80 to obtain a white PMMA emulsion. The PMMA emulsion was demulsified with a 10% aluminum sulfate aqueous solution to obtain a solid product. The solid product was then washed repeatedly with deionized water and dried in an oven at 80℃ for 20 hr to obtain PMMA microspheres.

[0060] (2) Preparation of PMMA-modified MgAl-LDH•CaO: Weigh 0.19 g of CaO powder and 4.84 g of PMMA microspheres obtained in step (1) and uniformly disperse them in deionized water to form suspension A1. Weigh 16.26 g of magnesium chloride hexahydrate and 9.66 g of aluminum chloride hexahydrate to prepare MgAl-LDH•CaO with a metal ion molar ratio of 2:1 and a concentration of 2 mol / L. 2+ And Al 3+ A mixed aqueous solution B1, weighing CO3 2－ and OH － Potassium carbonate and potassium hydroxide in a molar ratio of 0.3:1 were dissolved in water to prepare a mixed alkaline solution C1 with a concentration of 2 mol / L. Solutions B1 and C1 were simultaneously added dropwise to solution A1 at room temperature to co-precipitate and obtain solution D1. The pH of solution D1 was controlled at 9.0. After stirring and aging at room temperature for 15 hours, the solution was filtered, washed, and dried at 120℃ to form PMMA-modified MgAl-LDH•CaO. The amount of CaO added was 2% of the mass of MgAl-LDH, and the amount of PMMA added was 50% of the mass of MgAl-LDH.

[0061] (3) Preparation of CuZnAlZr@MgAl-LDO•CaO catalyst: 4.92 g of modified MgAl-LDH•CaO powder was weighed and uniformly dispersed in deionized water to form suspension A2. 8.53 g of copper chloride dihydrate, 6.82 g of anhydrous zinc chloride, 2.41 g of aluminum chloride hexahydrate, and 1.07 g of zirconium nitrate were weighed to prepare Cu... 2+ Zn 2+ Al 3+ and Zr 4+ A mixed aqueous solution B2 with a molar ratio of 1:1:0.2:0.05 and a total concentration of 0.5 mol / L was prepared. CO3 was weighed out. 2－ and OH － Sodium carbonate and sodium hydroxide in a molar ratio of 1:1 were dissolved in water to prepare a mixed alkaline solution C2 with a concentration of 0.5 mol / L. Solution B2 and solution C2 were simultaneously added dropwise to solution A2 at 60℃ to obtain solution D2 for co-precipitation. The pH of solution D2 was controlled at 9.0. After stirring and aging at 90℃ for 3 hours, the solution was filtered, washed, dried, and then calcined in air at 550℃ for 3 hours at a rate of 1℃ / min from room temperature to obtain the catalyst. The amount of modified MgAl-LDH•CaO powder added was calculated based on the fact that the mass loss during the calcination process to form MgAl-LDO•CaO was 45% and that MgAl-LDO•CaO accounted for 20% of the catalyst mass.

[0062] (4) Biomass syngas to low-carbon alcohols: The catalyst powder is pressed into tablets, crushed, and sieved to obtain 40-80 mesh catalyst particles. 1 g of catalyst particles is weighed and loaded into a reactor. The catalyst is reduced with H2 at 250℃ for 2 h. Biomass syngas with a composition of n(H2):n(CO2):n(CO):n(CH4) = 70:15:10:5 is introduced. The reactor is operated at 250℃, 2-8 MPa, and a space velocity of 4000 h⁻¹. -1 Lower alcohols were synthesized under the specified conditions. The reaction results are shown in Table 4. It can be seen that with the increase of reaction pressure, the total carbon and CO2 conversion rates, as well as the yield of lower alcohols, gradually increase.

[0063] Table 4 Effect of reaction pressure on the synthesis performance of lower alcohols

[0064] Example 3:

[0065] Preparation and application of CuZnAlTi@MgAl-LDO•CaO catalyst:

[0066] (1) PMMA preparation: 60 g of methyl methacrylate, 0.6 g of potassium persulfate, 0.18 g of sodium bicarbonate, 180 g of deionized water, 1.8 g of sodium dodecyl sulfate and 1.8 g of emulsifier OP-10 were weighed and added to a four-necked flask. After ultrasonic vibration at room temperature for 40 min, the mixture was heated to 75±0.5℃ and polymerized for 3 hr. After cooling to below 50℃, the mixture was filtered through a standard sieve with a mesh size of >80 to obtain a white PMMA emulsion. The PMMA emulsion was demulsified with a 10% aluminum sulfate aqueous solution to obtain a solid product. The solid product was then washed repeatedly with deionized water and dried in an oven at 80℃ for 24 hr to obtain PMMA microspheres.

[0067] (2) Preparation of PMMA-modified MgAl-LDH•CaO: Weigh 0.76 g of CaO powder and 1.53 g of PMMA microspheres obtained in step (1) and uniformly disperse them in deionized water to form suspension A1. Weigh 51.28 g of magnesium nitrate hexahydrate and 7.5 g of aluminum nitrate nonahydrate to prepare MgAl-LDH•CaO with a metal ion molar ratio of 10:1 and a concentration of 0.5 mol / L. 2+ And Al 3+ A mixed aqueous solution B1, weighing CO3 2－ and OH －Sodium carbonate and sodium hydroxide in a molar ratio of 0.6:1 were dissolved in water to prepare a mixed alkaline solution C1 with a concentration of 0.5 mol / L. Solutions B1 and C1 were simultaneously added dropwise to solution A1 at room temperature to co-precipitate and obtain solution D1. The pH of solution D1 was controlled at 9.5. After stirring and aging at room temperature for 8 hours, the solution was filtered, washed, and dried at 80℃ to form PMMA-modified MgAl-LDH•CaO. The amount of CaO added was 5% of the mass of MgAl-LDH, and the amount of PMMA added was 10% of the mass of MgAl-LDH.

[0068] (3) Preparation of CuZnAlTi@MgAl-LDO•CaO catalyst: 2.99 g of modified MgAl-LDH•CaO powder was weighed and uniformly dispersed in deionized water to form suspension A2. 12.79 g of copper chloride dihydrate, 6.82 g of anhydrous zinc chloride, 2.41 g of aluminum chloride hexahydrate and 0.47 g of titanium tetrachloride were weighed to prepare Cu 2+ Zn 2+ Al 3+ and Ti 4+ A mixed aqueous solution B2 with a molar ratio of 1.5:1:0.2:0.05 and a total concentration of 3 mol / L, weigh out CO3. 2－ and OH － Sodium carbonate and sodium hydroxide in a molar ratio of 0.3:1 were dissolved in water to prepare a mixed alkaline solution C2 with a concentration of 3 mol / L. Solution B2 and solution C2 were simultaneously added dropwise to solution A2 at 60℃ to obtain solution D2 for co-precipitation. The pH of solution D2 was controlled at 9.5. After stirring and aging at 85℃ for 5 hours, the solution was filtered, washed, dried, and then calcined in air at 450℃ for 5 hours from room temperature at a rate of 10℃ / min to obtain the catalyst. The amount of modified MgAl-LDH•CaO powder added was calculated based on the fact that the mass loss during the calcination process to form MgAl-LDO•CaO was 40% and that MgAl-LDO•CaO accounted for 10% of the catalyst mass.

[0069] (4) Biomass syngas to low-carbon alcohols: The catalyst powder is pressed into tablets, crushed, and sieved to obtain 40-80 mesh catalyst particles. 1g of catalyst particles is weighed and loaded into a reactor. The catalyst is reduced with H2 at 220℃ for 20 h. Biomass syngas with a composition of n(H2):n(CO2):n(CO):n(CH4) = 65:20:10:5 is introduced at 250℃, 4 MPa, and space velocity of 2000-10000 h⁻¹. -1 Lower alcohols were synthesized under the specified conditions. The reaction results are shown in Table 5. It can be seen that as the space velocity increases, the total carbon and CO2 conversion rates gradually decrease, but the yield of lower alcohols gradually increases.

[0070] Table 5 Effect of reaction space velocity on the synthesis performance of lower alcohols

[0071] The above description of the embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A Cu-based catalyst supported on a MgAl layered bimetallic oxide, characterized in that, The compositional formula of the catalyst is: (Cu x Zn y Al z M m+ n O x+y+1.5z+0.5m*n ) w @[Mg a Al b (OH) c (CO3) d O a+1.5b-0.5c-d •CaO, where M m+ M is a doped metal cation, selected from Ce. 4+ Zr 4+ and Ti 4+ One of them; x, y, z, n, a, b, c are all molar contents, and 2x+2y+2.5z+(1+0.5m)n=1, x / y=1~2, n≥0, 2a+2.5b+0.5c=1, a / b=2~10; w is the loading amount of Cu-based multi-metal oxide, w=60~90 wt%.

2. The catalyst according to claim 1, characterized in that, The value of x ranges from 0.05 to 0.30, the value of y ranges from 0.02 to 0.15, and the value of z ranges from 0.005 to 0.

020.

3. The method for preparing the Cu-based catalyst supported on the MgAl layered bimetallic oxide according to claim 1 or 2, characterized in that, A modified MgAl-LDH powder prepared by co-modification of polymethyl methacrylate and calcium oxide was used as a support, and Cu-based multi-metal oxide was used as the active component. A catalyst precursor was prepared by co-precipitation, and then calcined to obtain a Cu-based catalyst supported by MgAl layered bimetallic oxide MgAl-LDO•CaO.

4. The preparation method according to claim 3, characterized in that, Specifically, the steps include the following: S1. PMMA microspheres were prepared by in-situ emulsion polymerization. S2: Modified MgAl-LDH powder was prepared by co-precipitation using PMMA microspheres prepared in step S1 as a structure regulator and CaO as an adsorption enhancer. S3: The modified MgAl-LDH powder prepared in step S2 is used as a support and Cu-based multi-metal oxide is used as an active component to prepare a catalyst precursor by co-precipitation method, and then calcined to obtain a Cu-based catalyst supported by MgAl layered bimetallic oxide MgAl-LDO•CaO.

5. The preparation method according to claim 4, characterized in that, The specific steps of step S1 are as follows: Methyl methacrylate, potassium persulfate, sodium bicarbonate, deionized water, sodium dodecyl sulfate, and emulsifier OP-10 are added sequentially to a reaction vessel. After mixing at room temperature, the mixture is heated to 70℃~80℃ for polymerization reaction for 3~6 hours. After cooling to below 50℃, the mixture is filtered to obtain a white PMMA emulsion. The PMMA emulsion is demulsified with aluminum sulfate aqueous solution to obtain a solid product. After washing with water and drying, PMMA microspheres are finally obtained. The mass ratio of methyl methacrylate to deionized water is 1:(1.5~5), the amount of potassium persulfate is 0.2%~1.0% of methyl methacrylate, the amount of sodium bicarbonate is 0.1%~0.5% of methyl methacrylate, the amount of sodium dodecyl sulfate is 1%~3% of methyl methacrylate, and the amount of emulsifier is 1%~3% of methyl methacrylate.

6. The preparation method according to claim 4, characterized in that, The specific steps of step S2 are as follows: Calcium oxide powder and PMMA microspheres obtained in step S1 are uniformly dispersed in deionized water to form suspension A1, and Mg is prepared. 2+ And Al 3+ A mixed aqueous solution B1 was prepared by dissolving the precipitant in water to form solution C1. Solutions B1 and C1 were simultaneously added dropwise to solution A1 at room temperature for co-precipitation to obtain solution D1. The pH of solution D1 was controlled at 9.0–9.

5. After stirring and aging at room temperature for 8–24 hours, the solution was filtered, washed, and dried to form modified MgAl-LDH•CaO powder. The amount of CaO added was [missing information - likely a percentage] of MgAl. a Al b (OH) c (CO3) d O a+1.5b-0.5c-d The amount of PMMA microspheres added is 2%~10% by mass, and the amount of Mg is... a Al b (OH) c (CO3) d O a+1.5b-0.5c-d The weight is 10% to 50% of the product, and the drying temperature is 80℃ to 120℃.

7. The preparation method according to claim 6, characterized in that, In step S2, Mg 2+ And Al 3+ The molar ratio is 2:1 to 10:1, the total concentration is 0.5 to 2.0 mol / L, and the anion is nitrate or chloride ion; the precipitant is a combination of sodium carbonate and sodium hydroxide or a combination of potassium carbonate and potassium hydroxide, and CO3... 2－ and OH － The molar ratio is 0.3:1 to 1:1, and the total concentration is 0.5 to 2.0 mol / L.

8. The preparation method according to claim 4, characterized in that, The specific steps of step S3 are as follows: The modified MgAl-LDH•CaO powder obtained in step S2 is uniformly dispersed in deionized water to form suspension A2, and Cu is prepared. 2+ Zn 2+ Al 3+ A mixed aqueous solution B2 containing doped metal cations was prepared by dissolving the precipitant in water to form solution C2. Solution B2 and solution C2 were simultaneously added dropwise to solution A2 at 60℃~70℃ to co-precipitate and obtain catalyst precursor solution D2. The pH of solution D2 was controlled at 9.0~9.

5. Then, after stirring and aging at 80℃~90℃ for 3~6 hours, the solution was filtered, washed, dried, and calcined to obtain a Cu-based catalyst supported on a MgAl layered bimetallic oxide (MgAl-LDO•CaO). MgAl-LDO•CaO accounted for 10%~40% of the mass of the Cu-based catalyst supported on the MgAl layered bimetallic oxide, and the mass ratio of modified MgAl-LDH•CaO powder to MgAl-LDO•CaO was 1.5~2:

1. The calcination atmosphere was air, the calcination temperature was 450℃~550℃, the calcination time was 3~5 hours, and the heating rate was 1~10℃ / min.

9. The preparation method according to claim 8, characterized in that, In step S3, Cu 2+ Zn 2+ Al 3+ The molar ratio of the doped metal cation to the nitrate cation is 1:1:0.2:0.05~2:1:0.2:0.05, the total concentration is 0.5~3.0 mol / L, the anion is nitrate ion or chloride ion; the precipitant is a combination of sodium carbonate and sodium hydroxide or a combination of potassium carbonate and potassium hydroxide, CO3 2－ and OH － The molar ratio is 0.3:1 to 1:1, and the total concentration is 0.5 to 3.0 mol / L.

10. The application of the catalyst according to claim 1 or 2 in the in-situ adsorption of CO2 to enhance the preparation of lower alcohols from biomass syngas, characterized in that, The catalyst was loaded into a reactor and reduced in a hydrogen atmosphere at 220°C–300°C for 2–20 hours. After reduction, biomass syngas was introduced, the reaction pressure was 2–8 MPa, and the volume hourly space velocity was 2000–10000 h⁻¹. -1 Low-carbon alcohols are synthesized under the following conditions; the composition of the biomass syngas is as follows, by volume fraction: H2 accounts for 65%~75%, CO2 accounts for 15%~20%, CO accounts for 5%~10%, and CH4 accounts for 2%~5%.

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