Ga-modified copper-based catalyst, preparation method thereof and application of Ga-modified copper-based catalyst in preparation of methanol by hydrogenation of carbon dioxide

Abstract

The invention provides a Ga-modified copper-based catalyst, a preparation method thereof and an application of the Ga-modified copper-based catalyst in preparation of methanol by hydrogenation of carbon dioxide, the Ga-modified copper-based catalyst comprises a carrier and an active component loaded on the carrier, the carrier is a Ga-modified TiO2-Al2O3 composite oxide, and the active component is a Cu oxide. The Ga-modified copper-based catalyst has the performance of catalyzing the reaction for preparing methanol through carbon dioxide hydrogenation, and methanol can be generated at high selectivity under the reaction conditions of low temperature and high pressure.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular relates to a Ga-modified copper-based catalyst, a preparation method thereof, and an application thereof in the hydrogenation of carbon dioxide to produce methanol. Background Art

[0002] At present, methanol synthesis mainly relies on fossil fuels and is carried out through the syngas catalytic pathway, accompanied by a large amount of CO 2 With the implementation of the "dual carbon" policy, the construction of coal-to-methanol production enterprises with an annual production capacity of less than 1 million tons has been prohibited in China. 2 Catalytic hydrogenation to directly generate high value-added products is particularly important. Currently, Cu-based catalysts are widely used due to their low price, abundant reserves, and high CO 2 The hydrogenation reaction has been widely studied due to its good activity and methanol selectivity. 2 O 3 Although the catalyst has high activation CO 2 However, due to its easy deactivation (Ostwald ripening effect and particle migration) and high activity in the reverse water gas reaction (RWGS), CO 2 Low conversion rate and low methanol selectivity limit its industrial application.

[0003] In order to improve the activity of the catalyst, CO 2 The researchers optimized the catalyst structure and support composition to adjust the metal-support interaction and CO conversion rate and methanol selectivity. 2 and carbonyl species adsorption and hydrogenation conversion capacity, reducing by-products. Some studies have shown that combining single oxides or compounding with alumina can achieve complementary effects. Some studies have tested the use of titanium dioxide or zirconium dioxide to modify alumina carriers to form composite oxides, which can adjust the acidity and metal carrier interaction without losing good structural properties. For example, Baston et al. found that in Al prepared by sol-gel technology 2 O 3 -ZrO 2 Mo on 6+ has a lower reduction temperature, which indicates that ZrO 2 The addition of TiO weakens the interaction between the active component and the carrier (Catal. Today, 2015; 246: 184-190). Lin et al. showed that 2The composite supports (Ti-Ce and Ti-Zr) significantly increased the surface area and promoted the dispersion and adsorption of metals. The binary supports effectively improved the methanol production rate and selectivity (Catal. Today, 2021; 371, 150–161). However, the binary support design still has some limitations, especially in terms of the long-term stability and reaction selectivity of the catalyst. Therefore, it is an effective way to continue to dope the binary composite support with additives to regulate the methanol selectivity.

[0004] The Chinese patent application with publication number CN113058583A invented a CO 2 A bimetallic solid solution catalyst for efficient hydrogenation synthesis of methanol and dimethyl ether. The catalyst uses Ga and Zr as metal sources and is prepared by solvent evaporation induced self-assembly (EISA) method. x Bimetallic oxide solid solution catalyst at 3MPa, 603K, 24000ml / (g cat · h ) conditions, CO 2 The single-pass conversion rate exceeded 9.0%, and the selectivity of methanol and dimethyl ether reached 72.7%. However, the hydrogenation activity of this type of solid solution catalyst needs to be further improved and still cannot meet the requirements of industrial production.

[0005] The Chinese patent application with publication number CN102580750A relates to a CO2-containing material whose main components are Cu and Zn oxides and a multifunctional composite carrier of Ti and Al oxides. 2 Preparation method and application of hydrogenation methanol catalyst. The catalyst is prepared by a parallel flow co-precipitation method. In terms of mass percentage, the Cu content is 10% to 50%, the Zn content is 3% to 25%, the total content of Ti and Al is 1% to 25%, and the remainder is O. The catalyst has excellent performance with high activity at relatively low temperature and low pressure. However, copper and zirconium as the main components lead to complex active sites and difficulty in regulating product selectivity, and the content accounts for a relatively high proportion. The aggregation of copper particles leads to a reduction in active sites or the catalyst is prone to deactivation, so the product selectivity of the catalyst is low.

[0006] In summary, the current CO 2 The main problem with copper-based catalysts for hydrogenation to methanol is the defects in the binary carrier structure and performance, which make it impossible to achieve good activity at low temperatures while maintaining high methanol selectivity; the copper content of the active metal component is too high, and the copper particles are prone to agglomeration, resulting in catalyst deactivation. Summary of the invention

[0007] The present invention aims to improve the methanol selectivity and CO 2In order to overcome the disadvantage of low conversion rate, a Ga-modified copper-based catalyst and a preparation method thereof and an application in the hydrogenation of carbon dioxide to methanol are provided. The Ga-modified copper-based catalyst has the performance of catalyzing the hydrogenation of carbon dioxide to methanol, and can produce methanol with high selectivity under low temperature and high pressure reaction conditions.

[0008] The present invention is achieved through the following technical solutions: A Ga-modified copper-based catalyst, comprising a carrier and an active component supported on the carrier, wherein the carrier is Ga-modified TiO 2 -Al 2 O 3 The composite oxide, wherein the active component is Cu oxide.

[0009] Preferably, based on CuO, the loading of Cu is 2 -Al 2 O 3 1%~15% of the mass of composite oxides; CuO and TiO 2 -Al 2 O 3 The sum of the mass of the composite oxides is taken as the basis, with Ga 2 O 3 The Ga doping amount is 0.25%~1%.

[0010] The preparation method of the Ga-modified copper-based catalyst of the present invention comprises the following steps: S1, the aluminum source is dissolved in ethanol, then the acid is added dropwise and stirred to obtain solution A; the template is dissolved in ethanol and stirred to obtain solution B; solution A is added to solution B, and the titanium source is added after stirring, and the stirring is continued, and then aged and calcined to obtain TiO with an ordered mesoporous structure. 2 -Al 2 O 3 Composite oxides; S2, dissolve copper salt in water to make Cu salt solution; drop the Cu salt solution onto TiO 2 -Al 2 O 3 The composite oxide surface was left to stand and dried to obtain Cu / TiO 2 -Al 2 O 3 sample; S3, dissolving gallium salt in water to prepare gallium salt solution; dropping the gallium salt solution onto Cu / TiO 2 -Al 2 O 3 The sample surface was allowed to stand, dried, and calcined to obtain a Ga-modified copper-based catalyst.

[0011] Preferably, in S1, the aluminum source is a mixture of one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum isopropoxide and sodium aluminate; the titanium source is a mixture of one or more of tetrabutyl titanate, titanium isopropoxide, titanium tetrachloride and barium metatitanate.

[0012] Preferably, in S2, the copper salt is copper sulfate, copper nitrate, copper chloride, copper citrate, copper acetylacetonate or copper oxalate.

[0013] Preferably, in S2, the gallium salt is gallium nitrate.

[0014] Preferably, in S3, the calcination temperature is 350-450° C., and the calcination time is 4-6 hours.

[0015] The present invention also provides the use of the Ga-modified copper-based catalyst in the production of methanol by hydrogenation of carbon dioxide.

[0016] Preferably, the application method of the Ga-modified copper-based catalyst in the production of methanol by hydrogenation of carbon dioxide is as follows: 2 The Ga-modified copper-based catalyst is reduced in a mixed atmosphere of Ar, the reduction temperature is 150-600°C, and the reduction time is 2-4 hours; then carbon dioxide is introduced to carry out a hydrogenation reaction.

[0017] Preferably, the temperature of the hydrogenation reaction is 220-300°C.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention introduces titanium dioxide into a single alumina carrier to rearrange the electronic structure of the carrier, and then adds a Ga additive with an inert electron pair effect to promote the transfer of electrons to the copper active phase, thereby enhancing the CO 2 As well as the adsorption of carbonyl species on active sites, promoting the hydrogenation conversion of carbonyl species and improving CO 2 The conversion rate and methanol selectivity of hydrogenation methanol catalyst are improved to achieve the purpose of improving methanol selectivity under low temperature conditions ( Figure 1 Compared with traditional copper-based catalysts, this catalyst effectively improves CO 2 The defects of low conversion rate and low methanol selectivity are overcome, and the selectivity and yield of the target product methanol are significantly improved. The catalyst of the present invention has good application prospects in the field of preparing high value-added chemicals by hydrogenation of carbon dioxide.

[0019] Furthermore, the catalyst of the present invention preferably has a suitable Ga doping amount, so that a higher methanol selectivity and CO 2 Conversion rate.

[0020] The Ga-modified copper-based catalyst of the present invention is used to catalyze the carbon dioxide hydrogenation reaction, achieving a high methanol selectivity and CO2 conversion rate, solving the problem of CO 2 The defects are low conversion rate and low methanol selectivity.

[0021] Furthermore, the present invention uses a Ga-modified copper-based catalyst to achieve a higher methanol selectivity at a lower hydrogenation reaction temperature, thereby reducing CO 2 Energy consumption of hydrogenation reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 The design concept of the catalyst prepared by the present invention.

[0024] Figure 2 The ordered mesoporous TiO prepared in Comparative Example 3 and Examples 1, 2 and 4 of the present invention 2 -Al 2 O 3 H catalysis of Ga-modified copper-based catalysts supported on composite oxides 2 -TPR spectrum. DETAILED DESCRIPTION

[0025] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0026] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0027] It should be noted that the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

[0028] The Ga-modified copper-based catalyst, carrier and active component loaded on the carrier of the present invention, wherein the carrier is Ga-treated TiO with an ordered mesoporous structure. 2 -Al 2 O 3 Composite oxide, the active component is Cu oxide.

[0029] Among them, the copper loading is calculated as CuO / TiO 2 -Al 2 O 3 The mass of the composite oxide is 1%~15%, and the gallium doping content is Ga 2 O 3 Calculated as Cu / TiO 2 -Al 2 O 3 0.25% to 1% by mass, more preferably 0.25% to 0.5% by mass. Through TiO 2 -Al 2 O 3 The composite oxide carrier is modified to adjust the electronic properties of the carrier surface, promote the transfer of electrons to the active metal, strengthen the species adsorption and hydrogenation activation at the active sites, further optimize the reaction path for methanol synthesis, and achieve the purpose of improving methanol selectivity under low temperature conditions.

[0030] The preparation method of the Ga-modified copper-based catalyst of the present invention comprises the following specific steps: (1) preparing solutions of an aluminum source and a template agent with ethanol respectively, and stirring in a water bath to obtain an aluminum source solution and a template agent solution; (2) adding an acid to the aluminum source solution obtained in step (1), and after sufficient stirring, adding the acid to the template solution obtained in step (1) to obtain a mixed solution, and stirring the mixed solution in a water bath; (3) Adding the titanium source to the mixed solution obtained in step (2), stirring in a water bath, aging, and calcining to obtain TiO with an ordered mesoporous structure 2 -Al 2 O3 Composite oxide supports; (4) Dissolve the copper salt to make a Cu salt solution, and drop it dropwise into the TiO 2 -Al 2 O 3 The surface of the composite oxide support was then left to stand at room temperature and vacuum dried to obtain the uncalcined Cu / TiO 2 -Al 2 O 3 sample; (5) Dissolve the gallium salt to make a gallium salt solution, and drop it dropwise into the Cu / TiO prepared in step (4). 2 -Al 2 O 3 The sample surface was then allowed to stand at room temperature, vacuum dried, and calcined to obtain a Ga-modified copper-based catalyst.

[0031] In step (1) of the present invention, the water bath stirring temperature is 25-35° C., and the stirring time is 4 h.

[0032] In step (2) of the present invention, the acid may be one of hydrochloric acid, nitric acid, sulfuric acid, and acetic acid, preferably hydrochloric acid or nitric acid; after adding the acid, the stirring temperature in the water bath is 25-35°C, and the stirring time is 15-30 min; after mixing, the stirring temperature in the water bath is 25-35°C, and the stirring time is 2 h.

[0033] In step (3) of the present invention, the aging time is preferably 48 hours; the aging temperature is preferably 55°C-60°C; the calcination time is preferably 4 hours; and the calcination temperature is preferably 550°C.

[0034] In step (4) of the present invention, the copper salt is preferably one of copper sulfate, copper nitrate, copper chloride, copper citrate, copper acetylacetonate and copper oxalate; and the gallium salt is preferably gallium nitrate.

[0035] In step (4) of the present invention, the molar ratio of copper salt to gallium salt is (0.01-0.2): (0.001-0.005); in step (4) and step (5), the standing time at room temperature is 12-24 hours; the vacuum drying temperature is 80°C-120°C, and the drying time is 12 hours-48 hours.

[0036] In step (5) of the present invention, the calcination temperature is 350-450° C. and the calcination time is 4-6 hours.

[0037] The Ga-modified copper-based catalyst of the present invention can be used as a hydrogenation catalyst for catalyzing the hydrogenation of carbon dioxide to produce methanol. The specific method is: the Ga-modified copper-based catalyst is heated in H 2 -Ar mixed atmosphere (H 2The reduction is carried out at a volume concentration of 10%, the reduction temperature is 150℃~600℃, the reduction time is 2h~4h, and then a mixed gas of hydrogen, carbon dioxide and nitrogen is introduced to carry out hydrogenation reaction, the reaction temperature is 220~300℃, and the reaction space velocity is 1500~6000mL g cat -1 h -1 During the reaction, H 2 :CO 2 :N 2 The volume ratio is preferably 66:22:12.

[0038] In the method for preparing methanol by catalytic hydrogenation of carbon dioxide of the present invention, the reaction temperature of the hydrogenation reaction is more preferably 240-260°C.

[0039] Comparative Example 1 Step 1: Take TiO 2 -Al 2 O 3 2.7 g of the carrier (water absorption rate is 76.9%) is spread flat on a surface dish for later use; the raw materials are weighed according to the copper loading amount of 10%, 0.91118 g of copper nitrate is dissolved in a certain amount of deionized water, and dripped onto the weighed carrier drop by drop, and allowed to stand at room temperature for 24 hours, vacuum dried at 120°C for 48 hours, and calcined at 350°C for 4 hours.

[0040] Step 2: The solid obtained in step 1 is mixed with 10% H 2 / Ar mixed atmosphere, the temperature was 350℃ for 4h to obtain ordered mesoporous TiO 2 -Al 2 O 3 The supported Cu catalyst had a copper loading of 10% and a gallium loading of 0%; the fixed bed space velocity was set to 3000 mL g cat -1 h -1 Then the temperature was raised to 220°C and H2O2 with a volume ratio of 66:22:12 was introduced. 2 / CO 2 / N 2 The raw gas and gas phase products were analyzed by chromatography, and the methanol selectivity was 64.25%, CO 2 The conversion rate was 1.8%.

[0041] Comparative Example 2 Step 1: Take TiO 2 -Al 2 O 34.25 g of the carrier (water absorption rate is 60%) is spread flat on a surface dish for later use; the raw materials are weighed according to the copper loading amount of 15%, 2.278 g of copper nitrate is dissolved in a certain amount of deionized water, and dripped onto the weighed carrier drop by drop, and allowed to stand at room temperature for 12 h, vacuum dried at 80 ° C for 48 h, and calcined at 350 ° C for 4 h.

[0042] Step 2: The solid obtained in step 1 is mixed with 10% H 2 / Ar mixed atmosphere, the temperature was 350℃ for 4h to obtain ordered mesoporous TiO 2 -Al 2 O 3 The supported Cu metal catalyst had a copper loading of 15% and a gallium loading of 0%; the fixed bed space velocity was set to 3000 mL g cat -1 h -1 Then the temperature was raised to 220°C and H2O2 with a volume ratio of 66:22:12 was introduced. 2 / CO 2 / N 2 The raw gas and gas phase products were analyzed by chromatography, and the methanol selectivity was 78.43%, CO 2 The conversion rate is 7.73%. Comparative Example 3 Step 1: Take TiO 2 -Al 2 O 3 4.25 g of the carrier (water absorption rate of 60%) was spread on a surface dish for later use; the raw materials were weighed according to the copper loading of 15%, 2.278 g of copper nitrate was dissolved in a certain amount of deionized water, and dripped onto the weighed carrier drop by drop, and allowed to stand at room temperature for 12 h, vacuum dried at 80 ° C for 48 h, and calcined at 350 ° C for 4 h to obtain 15% Cu / TiO 2 -Al 2 O 3 Catalyst samples.

[0043] Step 2: The solid obtained in step 1 is mixed with 10% H 2 / Ar mixed atmosphere, the temperature was 350℃ for 4h to obtain ordered mesoporous TiO 2 -Al 2 O 3 The supported Cu catalyst had a copper loading of 15% and a gallium loading of 0%; the fixed bed space velocity was set to 3000 mL g cat -1 h -1 Then the temperature was raised to 240°C and H2O2 with a volume ratio of 66:22:12 was introduced. 2 / CO 2 / N 2The raw gas and gas phase products were analyzed by chromatography, and the methanol selectivity was 63.4%, CO 2 The conversion rate is 7.85%.

[0044] Comparative Example 4 Step 1: Take γ-Al 2 O 3 4.25 g of the carrier was spread flat on a surface dish for later use; raw materials were weighed according to a copper loading of 15%, 2.278 g of copper nitrate was dissolved in a certain amount of deionized water, and the solution was dripped onto the weighed carrier drop by drop, and the mixture was allowed to stand at room temperature for 12 h, and then vacuum dried at 80°C for 48 h.

[0045] Step 2: Weigh the Cu / γ-Al prepared in step 1 above. 2 O 3 5g of the sample was spread on a surface dish for later use. Raw materials were weighed according to the gallium doping amount of 0.25%. 0.0279g of gallium nitrate was dissolved in a certain amount of deionized water and dripped into the Cu / γ-Al 2 O 3 The sample was left at room temperature for 24 h, vacuum dried at 120 °C for 48 h, and calcined at 350 °C for 4 h.

[0046] Step 3: The solid obtained in step 2 is mixed with 10% H 2 / Ar mixed atmosphere, the temperature was 350℃ for 4h to obtain γ-Al 2 O 3 The supported Cu catalyst had a copper loading of 15% and a gallium loading of 0.25%; the fixed bed space velocity was set to 3000 mL g cat -1 h -1 Then the temperature was raised to 240°C and H2O2 with a volume ratio of 66:22:12 was introduced. 2 / CO 2 / N 2 The raw gas and gas phase products were analyzed by chromatography, and the methanol selectivity was 85.7%, CO 2 The conversion rate is 11.23%.

[0047] Example 1 Step 1: Take TiO 2 -Al 2 O 3 4.25 g of the carrier (water absorption rate of 60%) was spread on a surface dish for later use; the raw materials were weighed according to the copper loading of 15%, 2.278 g of copper nitrate was dissolved in a certain amount of deionized water, and dripped onto the weighed carrier drop by drop, and allowed to stand at room temperature for 12 h, and vacuum dried at 80°C for 48 h.

[0048] Step 2: Weigh the Cu / TiO 2 -Al 2 O3 5 g of the sample was spread on a surface dish for later use. Raw materials were weighed according to the gallium doping amount of 0.25%. 0.0279 g of gallium nitrate was dissolved in a certain amount of deionized water and dripped into the Cu / TiO 2 -Al 2 O 3 The sample was left at room temperature for 24 h, vacuum dried at 120 °C for 48 h, and calcined at 350 °C for 4 h.

[0049] Step 3: The solid obtained in step 2 is mixed with 10% H 2 / Ar mixed atmosphere, the temperature was 350℃ for 4h to obtain ordered mesoporous TiO 2 -Al 2 O 3 The supported Cu catalyst had a copper loading of 15% and a gallium loading of 0.25%; the fixed bed space velocity was set to 3000 mL g cat -1 h -1 Then the temperature was raised to 240°C and H2O2 with a volume ratio of 66:22:12 was introduced. 2 / CO 2 / N 2 The raw gas and gas phase products were analyzed by chromatography, and the methanol selectivity was 98.41%, CO 2 The conversion rate is 14.82%. Example 2 Step 1: Take TiO 2 -Al 2 O 3 4.25 g of the carrier (water absorption rate of 60%) was spread on a surface dish for later use; the raw materials were weighed according to the copper loading of 15%, 2.278 g of copper nitrate was dissolved in a certain amount of deionized water, and dripped onto the weighed carrier drop by drop, and allowed to stand at room temperature for 12 h, and vacuum dried at 80°C for 48 h.

[0050] Step 2: Weigh the Cu / TiO 2 -Al 2 O 3 5g of the sample was spread on a surface dish for later use. Raw materials were weighed according to the gallium doping amount of 0.5%. 0.056g of gallium nitrate was dissolved in a certain amount of deionized water and dripped into the Cu / TiO 2 -Al 2 O 3 The sample was left at room temperature for 24 h, vacuum dried at 120 °C for 48 h, and calcined at 350 °C for 4 h.

[0051] Step 3: The solid obtained in step 2 is mixed with 10% H 2 / Ar mixed atmosphere, the temperature was 350℃ for 4h to obtain ordered mesoporous TiO 2-Al 2 O 3 The supported Cu catalyst had a copper loading of 15% and a gallium loading of 0.5%; the fixed bed space velocity was set to 3000 mL g cat -1 h -1 Then the temperature was raised to 240°C and H2O2 with a volume ratio of 66:22:12 was introduced. 2 / CO 2 / N 2 The raw gas and gas phase products were analyzed by chromatography, and the methanol selectivity was 97.23%, CO 2 The conversion rate is 13.45%. Example 3 Step 1: Take TiO 2 -Al 2 O 3 4.25 g of the carrier (water absorption rate of 60%) was spread on a surface dish for later use; the raw materials were weighed according to the copper loading of 15%, 2.278 g of copper nitrate was dissolved in a certain amount of deionized water, and dripped onto the weighed carrier drop by drop, and allowed to stand at room temperature for 12 h, and vacuum dried at 80°C for 48 h.

[0052] Step 2: Weigh the Cu / TiO 2 -Al 2 O 3 5 g of the sample was spread on a surface dish for later use. Raw materials were weighed according to the gallium doping amount of 0.75%. 0.084 g of gallium nitrate was dissolved in a certain amount of deionized water and dripped into the Cu / TiO 2 -Al 2 O 3 The sample was left at room temperature for 24 h, vacuum dried at 120 °C for 48 h, and calcined at 350 °C for 4 h.

[0053] Step 3: The solid obtained in step 2 is mixed with 10% H 2 / Ar mixed atmosphere, the temperature was 350℃ for 4h to obtain ordered mesoporous TiO 2 -Al 2 O 3 The supported Cu catalyst had a copper loading of 15% and a gallium loading of 0.75%; the fixed bed space velocity was set to 3000 mL g cat -1 h -1 Then the temperature was raised to 240°C and H2O2 with a volume ratio of 66:22:12 was introduced. 2 / CO 2 / N 2 The raw gas and gas phase products were analyzed by chromatography, and the methanol selectivity was 95.40%, CO 2 The conversion rate was 9.00%. Example 4 Step 1: Take TiO 2 -Al 2 O 3 4.25 g of the carrier (water absorption rate of 60%) was spread on a surface dish for later use; the raw materials were weighed according to the copper loading of 15%, 2.278 g of copper nitrate was dissolved in a certain amount of deionized water, and dripped onto the weighed carrier drop by drop, and allowed to stand at room temperature for 12 h, and vacuum dried at 80°C for 48 h.

[0054] Step 2: Weigh the Cu / TiO 2 -Al 2 O 3 5g of the sample was spread on a surface dish for later use. Raw materials were weighed according to the gallium doping amount of 1%. 0.1125g of gallium nitrate was dissolved in a certain amount of deionized water and dripped into the Cu / TiO 2 -Al 2 O 3 The sample was left at room temperature for 24 h, vacuum dried at 120 °C for 48 h, and calcined at 350 °C for 4 h.

[0055] Step 3: The solid obtained in step 2 is mixed with 10% H 2 / Ar mixed atmosphere, the temperature was 350℃ for 4h to obtain ordered mesoporous TiO 2 -Al 2 O 3 The supported Cu catalyst had a copper loading of 15% and a gallium loading of 1%; the fixed bed space velocity was set to 3000 mL g cat -1 h -1 Then the temperature was raised to 240°C and H2O2 with a volume ratio of 66:22:12 was introduced. 2 / CO 2 / N 2 The raw gas and gas phase products were analyzed by chromatography, and the methanol selectivity was 90.05%, CO 2 The conversion rate is 8.07%. Example 5 Step 1: Take TiO 2 -Al 2 O 3 4.25 g of the carrier (water absorption rate of 60%) was spread on a surface dish for later use; the raw materials were weighed according to the copper loading of 15%, 2.278 g of copper nitrate was dissolved in a certain amount of deionized water, and dripped onto the weighed carrier drop by drop, and allowed to stand at room temperature for 12 h, and vacuum dried at 80°C for 48 h.

[0056] Step 2: Weigh the Cu / TiO 2 -Al 2 O 35 g of the sample was spread on a surface dish for later use. Raw materials were weighed according to the gallium doping amount of 0.25%. 0.0279 g of gallium nitrate was dissolved in a certain amount of deionized water and dripped into the Cu / TiO 2 -Al 2 O 3 The sample was left at room temperature for 24 h, vacuum dried at 120 °C for 48 h, and calcined at 350 °C for 4 h.

[0057] Step 3: The solid obtained in step 2 is mixed with 10% H 2 / Ar mixed atmosphere, the temperature was 350℃ for 4h to obtain ordered mesoporous TiO 2 -Al 2 O 3 The supported Cu catalyst had a copper loading of 15% and a gallium loading of 0.25%; the fixed bed space velocity was set to 3000 mL g cat -1 h -1 Then the temperature was raised to 260°C and H2O2 with a volume ratio of 66:22:12 was introduced. 2 / CO 2 / N 2 The raw gas and gas phase products were analyzed by chromatography, and the methanol selectivity was 84.90%, CO 2 The conversion rate is 9.10%. Example 6 Step 1: Take TiO 2 -Al 2 O 3 4.25 g of the carrier (water absorption rate of 60%) was spread on a surface dish for later use; the raw materials were weighed according to the copper loading of 15%, 2.278 g of copper nitrate was dissolved in a certain amount of deionized water, and dripped onto the weighed carrier drop by drop, and allowed to stand at room temperature for 12 h, and vacuum dried at 80°C for 48 h.

[0058] Step 2: Weigh the Cu / TiO 2 -Al 2 O 3 5 g of the sample was spread on a surface dish for later use. Raw materials were weighed according to the gallium doping amount of 0.25%. 0.0279 g of gallium nitrate was dissolved in a certain amount of deionized water and dripped into the Cu / TiO 2 -Al 2 O 3 The sample was left at room temperature for 24 h, vacuum dried at 120 °C for 48 h, and calcined at 350 °C for 4 h.

[0059] Step 3: The solid obtained in step 2 is mixed with 10% H 2 / Ar mixed atmosphere, the temperature was 350℃ for 4h to obtain ordered mesoporous TiO 2 -Al2 O 3 The supported Cu catalyst had a copper loading of 15% and a gallium loading of 0.25%; the fixed bed space velocity was set to 3000 mL g cat -1 h -1 Then the temperature was raised to 280°C and H2O2 with a volume ratio of 66:22:12 was introduced. 2 / CO 2 / N 2 The raw gas and gas phase products were analyzed by chromatography, and the methanol selectivity was 76.4%, CO 2 The conversion rate is 9.80%. Example 7 Step 1: Take TiO 2 -Al 2 O 3 4.25 g of the carrier (water absorption rate of 60%) was spread on a surface dish for later use; the raw materials were weighed according to the copper loading of 15%, 2.278 g of copper nitrate was dissolved in a certain amount of deionized water, and dripped onto the weighed carrier drop by drop, and allowed to stand at room temperature for 12 h, and vacuum dried at 80°C for 48 h.

[0060] Step 2: Weigh the Cu / TiO 2 -Al 2 O 3 5 g of the sample was spread on a surface dish for later use. Raw materials were weighed according to the gallium doping amount of 0.25%. 0.0279 g of gallium nitrate was dissolved in a certain amount of deionized water and dripped into the Cu / TiO 2 -Al 2 O 3 The sample was left at room temperature for 24 h, vacuum dried at 120 °C for 48 h, and calcined at 350 °C for 4 h.

[0061] Step 3: The solid obtained in step 2 is mixed with 10% H 2 / Ar mixed atmosphere, the temperature was 350℃ for 4h to obtain ordered mesoporous TiO 2 -Al 2 O 3 The supported Cu catalyst had a copper loading of 15% and a gallium loading of 0.25%; the fixed bed space velocity was set to 3000 mL g cat -1 h -1 Then the temperature was raised to 300°C and H2O2 with a volume ratio of 66:22:12 was introduced. 2 / CO 2 / N 2 The raw gas and gas phase products were analyzed by chromatography, and the methanol selectivity was 63.4%, CO 2 The conversion rate is 13.02%. Table 1 shows the CO of the 10 catalysts prepared above. 2 Catalytic performance data of hydrogenation to methanol.

[0062] Table 1 CO of each catalyst 2 Catalytic performance data of hydrogenation to methanol

[0063] From the data comparison of Comparative Examples 1 and 2, it is found that when the Cu loading content is 15%, the Cu / TiO 2 -Al 2 O 3 The catalytic activity of the catalyst is better. Comparing the data of Comparative Examples 2 and 3, it can be seen that at 240 °C, CO 2 The conversion rate is higher than that of CO at 220℃ 2 From the performance data of Comparative Example 3 and Examples 1 to 4, it is clear that the selectivity of methanol and CO 2 The conversion rate increases first and then decreases with the increase of Ga doping amount, indicating that adding a small amount of Ga can improve the selectivity of methanol and CO 2 However, excessive introduction of Ga will inhibit hydrogenation activity and reduce methanol selectivity. In addition, the 0.25% Ga-doped Cu / TiO synthesized by the isovolumetric impregnation method in Example 1 2 -Al 2 O 3 The catalyst exhibits better hydrogenation performance under low temperature conditions. On the catalyst of Example 1, the methanol selectivity is about 1.38 times that of the pure copper-based catalyst (Comparative Example 3) at a reaction temperature of 240°C. By comparing Example 1 with Examples 5 to 7, it can be seen that as the catalytic reaction temperature increases, CO 2 The conversion first decreases and then increases, while the methanol selectivity continues to decrease. 2 -Al 2 O 3 The methanol selectivity of the catalyst at 240 °C is 1.16-1.55 times that at 260-300 °C (Examples 5-7), indicating that Ga doping significantly improves CO 2 Methanol selectivity of hydrogenation methanol under low temperature conditions. Comparison of Example 1 and Comparative Example 4 shows that relative to γ-Al 2 O 3 The carrier is TiO 2 -Al 2 O 3 Catalysts prepared with composite oxide supports can further improve CO 2 Methanol selectivity and CO in hydrogenation to methanol 2 Conversion rate.

[0064] Figure 2 The ordered mesoporous TiO prepared in Comparative Example 3 and Examples 1, 2 and 4 of the present invention 2 -Al 2 O 3 H catalysis of Ga-modified copper-based catalysts supported on composite oxides 2 -TPR spectra, there are four types of reduction peaks in all four groups of catalysts, and these four reduction peaks are all attributed to the reduction of CuO species. This is mainly because compared with the other two metal ions (Ti 4+ and Ga 3+ ), Cu 2+ It is easier to be reduced at low temperatures, and titanium oxide and gallium oxide do not have reduction conditions below 600°C. The reduction peak of the unmodified catalyst in the figure is shorter. After modification, the peak height of the catalyst reduction peak is slightly increased, and the peak shape is significantly wider. Among them, the peak height of the catalyst doped with 0.25% Ga is significantly increased, the peak width is narrowed, but the area is significantly increased, which indicates that the number of active centers contained on the surface of the catalyst is significantly increased after modification. After modification, the reduction peak migrates to the low temperature zone as a whole, and the peak tail value decreases by about 21°C, indicating that the difficulty of reduction is reduced. It is worth noting that with the increase of Ga content, the reduction temperature of the modified catalyst in the low temperature zone (200~350°C) shows a trend of first decreasing and then increasing. When 0.25% Ga is doped, the reduction temperature of Cu in the low temperature zone is the lowest. When the Ga doping amount reaches 1%, the reduction temperature of the catalyst moves to high temperature as a whole compared with 0.25% and 0.5% Ga doping. This may be due to the excessive Ga content, which leads to the formation of larger CuO particles during the calcination of the catalyst. In summary, doping with an appropriate amount of Ga additive can promote the dispersion of CuO, so that the CuO species can be completely reduced at a lower temperature. The present invention utilizes the strong interaction between the titanium-aluminum composite oxide carrier with an ordered mesoporous structure and the metal active component and the inert electron pair effect of the Ga additive to promote the dispersion of the active component and the adsorption and hydrogenation conversion of the carbonyl species, thereby improving the catalyst stability and CO 2 Conversion and methanol selectivity.

Claims

1. A Ga-modified copper-based catalyst, characterized in that The Ga-modified copper-based catalyst comprises a carrier and an active component loaded on the carrier, wherein the carrier is a Ga-modified TiO2-Al2O3 composite oxide, and the active component is a Cu oxide.

2. The Ga-modified copper-based catalyst according to claim 1, characterized in that Calculated in terms of CuO, the loading amount of Cu is 1%~15% of the mass of the TiO2-Al2O3 composite oxide; based on the sum of the masses of CuO and the TiO2-Al2O3 composite oxide, calculated in terms of Ga2O3, the doping amount of Ga is 0.25%~1%.

3. The method for preparing the Ga-modified copper-based catalyst according to claim 1 or 2, characterized in that: The steps include: S1, dissolving the aluminum source in ethanol, then dropping the acid and stirring to obtain solution A; dissolving the template in ethanol and stirring to obtain solution B; adding solution A to solution B, stirring and then adding the titanium source, continuing to stir, then aging and calcining to obtain a TiO2-Al2O3 composite oxide with an ordered mesoporous structure; S2, dissolving copper salt in water to prepare a Cu salt solution; dropping the Cu salt solution onto the surface of the TiO2-Al2O3 composite oxide, standing and drying, to obtain a Cu / TiO2-Al2O3 sample; S3, dissolving the gallium salt in water to prepare a gallium salt solution; dropping the gallium salt solution onto the surface of the Cu / TiO2-Al2O3 sample, allowing it to stand, drying, and calcining to obtain a Ga-modified copper-based catalyst.

4. The method for preparing a Ga-modified copper-based catalyst according to claim 3, characterized in that: In S1, the aluminum source is a mixture of one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum isopropoxide and sodium aluminate; the titanium source is a mixture of one or more of tetrabutyl titanate, titanium isopropoxide, titanium tetrachloride and barium metatitanate.

5. The method for preparing a Ga-modified copper-based catalyst according to claim 3, characterized in that: In S2, the copper salt is copper sulfate, copper nitrate, copper chloride, copper citrate, copper acetylacetonate or copper oxalate.

6. The method for preparing a Ga-modified copper-based catalyst according to claim 3, characterized in that: In S2, the gallium salt is gallium nitrate.

7. The method for preparing a Ga-modified copper-based catalyst according to claim 3, characterized in that: In S3, the calcination temperature is 350~450°C and the calcination time is 4~6h.

8. Use of the Ga-modified copper-based catalyst according to claim 1 or 2 in the production of methanol by hydrogenation of carbon dioxide.

9. The use according to claim 8, characterized in that: The Ga-modified copper-based catalyst is reduced in a H2-Ar mixed atmosphere at a reduction temperature of 150-600°C for a reduction time of 2-4 hours; then carbon dioxide is introduced to carry out a hydrogenation reaction.

10. The use according to claim 8, characterized in that: The temperature of the hydrogenation reaction is 220~300℃.

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