Catalyst for preparing formic acid through thermocatalytic CO2 hydrogenation as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst for preparing formic acid through thermocatalysis CO2 hydrogenation and a preparation method and application of the catalyst in a reaction for preparing formic acid through thermocatalysis CO2 hydrogenation, the catalyst comprises an active component and a carrier for bearing the active component, the active component is a transition metal monatomic atom, the carrier is modified by an organic ligand in advance, and the organic ligand is a transition metal monatomic atom. One end of the organic ligand is uniformly grafted on the surface of the carrier, and the other end of the organic ligand is coordinated with a transition metal single atom. The preparation method of the catalyst is simple, expensive ligands do not need to be used, and the cost is low; the transition metal in the catalyst is in a monatomic dispersed state, and the utilization rate of the metal is high. The prepared catalyst shows good catalytic activity on a reaction for preparing formic acid through thermocatalytic CO2 hydrogenation under the condition that an organic solvent is not used; the catalyst even can thermocatalyze CO2 hydrogenation in a water phase to prepare formic acid under the condition of not adding alkali.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a catalyst for preparing formic acid by thermal catalytic CO2 hydrogenation, a preparation method thereof, and an application in a thermal catalytic CO2 hydrogenation reaction for preparing formic acid. Background Art

[0002] With the continuous growth of population and the acceleration of global industrialization, the increasingly frequent human activities have not only accelerated the consumption of fossil fuels, but also led to a large amount of greenhouse gas CO2 emissions. This has not only caused a waste of resources, but also brought adverse effects on the ecological environment. However, CO2 is also a C1 resource that is abundant, cheap, easy to obtain, non-toxic and recyclable. Converting it into high-value-added fuels or chemicals is recognized as an ideal strategy to solve the shortage of fossil fuels and the carbon emission crisis.

[0003] The hydrogenation of carbon dioxide to formic acid (CO2+H2→HCOOH) can not only effectively "reduce carbon emissions", but also achieve efficient storage of hydrogen energy and synthesize high value-added chemicals. In this reaction, the utilization rate of atoms is as high as 100%, which is in line with the development concept of "green chemistry". Literature shows that the conversion of CO2 hydrogenation to formic acid can be achieved through electrocatalysis, photocatalysis and thermal catalysis. The electrocatalytic synthesis process is clean, but it is limited by factors such as hydrogen evolution competition reaction and slow reaction kinetics, and this technology is still greatly hindered on the road to industrialization; the photocatalytic reaction conditions are mild, but its energy source is mainly sunlight, which is limited by geography and climate; the thermal catalytic method can achieve large-scale and continuous conversion of CO2 to formic acid, which is easy to commercialize, and is expected to accelerate the industrialization of CO2 hydrogenation to formic acid.

[0004] Regarding the reaction of preparing formic acid by thermal catalytic hydrogenation of CO2, domestic and foreign scholars have conducted in-depth research on two types of catalytic systems, homogeneous catalysts and heterogeneous catalysts. For homogeneous catalysts, organic ligands are often used to coordinate with metal ions (Ru, Ir, Mn, etc.) to obtain homogeneous metal complexes, which have the advantages of high utilization of active centers, strong selectivity, and high activity. For example, the patent document with application publication number CN 105772091 A discloses a class of catalysts that can reduce CO2 and their application in CO2 reduction reactions; the catalyst includes a metal and a ligand, the metal is iridium, cobalt, rhodium, ruthenium, iron, osmium, palladium, platinum, copper, zinc and manganese, etc., and the ligand is a heterocyclic compound containing a C=N double bond in the structure; this type of catalyst was used for the first time in the reduction reaction of CO2, the reaction uses water as a solvent, and the reaction can proceed smoothly under alkali-free conditions. The highest TON at room temperature can reach more than 10,000, which is the highest value currently achieved under alkali-free conditions; in the presence of alkali, a TON of >140,000 can be obtained, and the highest TOF

[0005] >30000h -1. The patent document with application publication number CN 108424359 A discloses a method for preparing formate / formic acid by catalyzing CO2 hydrogenation reduction in an aqueous phase with a ruthenium complex. Under the condition of adding a weak base (1-2 mol / L KHCO3), CO2 is catalyzed for preparing formate at 90-130°C in an aqueous phase. The catalytic CO2 hydrogenation reduction shows good catalytic activity in the process of catalytic CO2 hydrogenation, and the TON reaches up to 3380; without adding a base, CO2 is catalyzed for preparing formic acid directly in an aqueous phase with a TON of 920. The patent document with application publication number CN 105503563B discloses a method for catalyzing CO2 hydrogenation reduction with a sulfur-containing iridium complex. Under the condition of adding a weak base (1-2 mol / L KHCO3), CO2 is catalyzed for preparing formic acid at 70-100°C in an aqueous phase. The catalytic CO2 hydrogenation reduction shows good catalytic activity in the process of catalytic CO2 hydrogenation, and the TON reaches up to 232. However, the use of expensive organic ligands increases the production cost of catalysts and creates safety and environmental issues, hindering their development towards industrial application.

[0006] A method for preparing formate by catalytic hydrogenation of CO2 is disclosed in the patent document with application publication number CN 105367404 B, which is characterized in that CO2 is used as raw material, and reacts with hydrogen under catalysis of nanoporous palladium catalyst and alkaline conditions to prepare formate. The catalyst used is a heterogeneous catalyst, which avoids the use of expensive organic ligands. However, Pd exists in a bulk state in the nanoporous palladium catalyst, and the effective utilization rate of Pd is low. In addition, the amount of precious metal Pd is large, resulting in a higher reaction cost. Summary of the invention

[0007] In order to solve the above technical problems, the present invention discloses a catalyst for preparing formic acid by thermal catalytic CO2 hydrogenation, a preparation method and an application thereof. The preparation method of the catalyst is simple, does not require the use of expensive ligands, and has low cost. The transition metal in the catalyst is in a single-atom dispersed state, thereby improving the utilization rate of the metal. The prepared catalyst exhibits good catalytic activity for the thermal catalytic CO2 hydrogenation to prepare formic acid reaction without the use of an organic solvent. The catalyst can even thermally catalytically hydrogenate CO2 to prepare formic acid in an aqueous phase without the addition of an alkali.

[0008] A thermal catalytic CO2 hydrogenation catalyst for producing formic acid in the present invention that solves the above technical problems includes an active component and a carrier that carries the active component, wherein the active component is a transition metal single atom, the carrier is pre-modified with an organic ligand, one end of the organic ligand is uniformly grafted on the surface of the carrier, and the other end of the organic ligand is coordinated with the transition metal single atom.

[0009] In the thermal catalytic CO2 hydrogenation to formic acid catalyst, the organic ligand is covalently grafted on the carrier surface by chemical methods, which effectively promotes the dispersion of transition metals. The transition metals are evenly distributed on the catalyst carrier in a single-atom state. This formed framework structure improves the atomic utilization rate of transition metals compared to the physical impregnation method. In addition, the interaction between the donor groups in the organic ligand and the transition metal atoms can effectively regulate the electronic structure of the transition metal atoms and effectively improve the activity and stability of the catalyst in the thermal catalytic CO2 hydrogenation to formic acid reaction.

[0010] The carrier is a carbon material, SBA-15, or one or more oxides of silicon, aluminum, indium, cerium, zirconium, zinc, manganese, tin, titanium, tungsten, and molybdenum; preferably, the carbon material is mesoporous carbon.

[0011] The organic ligand is a silane coupling agent, and its molecular formula contains at least one electron-donating group; in the optimization scheme, the silane coupling agent includes one or more of 3-aminopropyltrimethoxysilane, N-methyl-3-aminopropyltrimethoxysilane, (N,N-dimethyl-3-aminopropyl)trimethoxysilane, N,N-diethyl-3-aminopropyltrimethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, diethylenetriaminopropyltrimethoxysilane, aminophenyltrimethoxysilane, and 2-(diphenylphosphino)ethyltriethoxysilane.

[0012] The molar ratio of the organic ligand to the carrier is 0.2 to 10:1. If the amount of the organic ligand is too high, the pores of the carrier will be blocked, reducing the specific surface area and pores of the carrier; if the amount is too low, it is not conducive to the stability and dispersion of the transition metal. More preferably, the molar ratio of the organic ligand to the carrier is 2:1.

[0013] The content of the active component is 0.1-7.0 wt% based on the mass of the carrier; preferably, the transition metal atom is selected from ruthenium or palladium metal; more preferably, the transition metal atom is selected from ruthenium metal.

[0014] The present invention provides a method for preparing a catalyst for preparing formic acid by thermal catalytic CO2 hydrogenation, comprising the following steps:

[0015] (1) preparing a carrier modified with an organic ligand;

[0016] (2) dispersing the organic ligand-modified carrier prepared in step (1) into a mixed solution of a transition metal precursor and triphenylphosphine, reacting for a certain period of time, filtering, washing, and drying to obtain a thermal catalytic CO2 hydrogenation catalyst for producing formic acid.

[0017] The preparation method of the organic ligand modified carrier in step (1) is: firstly, the carrier is dispersed in toluene by ultra-dispersion, and then the organic ligand is added thereto, and refluxed to obtain the carrier modified by the organic ligand; preferably, the molar ratio of the organic ligand to the transition metal in the transition metal precursor is 10 to 200: 1. If the molar ratio of the two is too low, part of the metal cannot be adsorbed on the carrier, resulting in a waste of the transition metal, and if it is too high, a waste of the organic ligand is caused.

[0018] Preferably, the reflux temperature is 70-100° C., and the reflux time is 4-12 h.

[0019] As above, the transition metal precursor in step (2) is at least one of ruthenium (III) tris(acetylacetonate), ammonium hexachlororuthenate, ruthenium trichloride, sodium chloroiridate, iridium acetate, hydrated iridium trichloride, and chloroiridic acid hexahydrate.

[0020] The molar ratio of the organic ligand to the transition metal in the transition metal precursor is 10-200:1.

[0021] Preferably, the molar ratio of triphenylphosphine to the transition metal in the transition metal precursor is 2-30:1. If the molar ratio of the two is too high, it is not conducive to the coordination of the transition metal with the organic ligand on the surface of the carrier, resulting in a waste of the transition metal. If the molar ratio is too low, the electronic control ability of the transition metal is reduced, which is not conducive to the improvement of the activity of the transition metal. More preferably, the molar ratio of the two is 4-10:1.

[0022] Preferably, based on the mass of the carrier, the content of the transition metal is 0.1-7.0 wt%.

[0023] The reaction time in step (2) is 2-8 hours.

[0024] The drying in step (2) is vacuum drying, the drying temperature is 60° C.-68° C., and the drying time is 10-15 hours; preferably, the drying temperature is 65° C. and the drying time is 12 hours.

[0025] The catalyst in the present invention can be used as a catalyst in the reaction of hydrogenating formic acid with thermal catalyst CO2. The hydrogenation reaction of CO2 is carried out with or without alkali, with the addition of a catalyst, deionized water as a solvent, H2 as a hydrogen source, the reaction temperature at 60-150°C, the reaction time at 4-24h; the total pressure of the reaction gas at 3-10MPa, wherein the pressure ratio of CO2 to H2 is 0.2-5:1; preferably, the reaction temperature at 80-105°C, the reaction time at 4-12h; the total pressure of the reaction gas at 4-7MPa, the pressure ratio of CO2 to H2 is 37:63.

[0026] The base includes at least one of inorganic bases such as sodium hydroxide, sodium bicarbonate, potassium bicarbonate, sodium carbonate, ammonium bicarbonate, potassium carbonate, and potassium hydroxide, or at least one of organic bases such as triethylamine, propylamine, diethylamine, ethylamine, dimethylamine, and piperidine.

[0027] Preferably, the concentration of the base in the reaction system is in the range of 0.5 to 5 mol / L.

[0028] The present invention has the following beneficial effects:

[0029] The catalyst of the present invention exhibits good catalytic activity for the thermal catalytic CO2 hydrogenation to formic acid reaction without using an organic solvent; the catalyst can even thermally catalytically hydrogenate CO2 to formic acid in an aqueous phase without adding an alkali.

[0030] The preparation method of the present invention is simple, does not require the use of expensive ligands, and has low cost; it can achieve high dispersion of transition metals and improve the utilization rate of metals; the organic ligands in the catalyst can achieve effective regulation of the electronic structure of the transition metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a simplified schematic diagram of the organic ligand-modified SBA-15 carrier prepared in Example 1 of the present invention.

[0032] Figure 2 This is the infrared spectrum of the organic ligand-modified SBA-15 carrier prepared in Example 1 of the present invention.

[0033] Figure 3 This is a CO2 programmed temperature desorption diagram of the organic ligand-modified SBA-15 and the unmodified organic ligand SBA-15 prepared in Example 1 of the present invention.

[0034] Figure 4 It is the N2 adsorption-desorption isotherm diagram of the organic ligand-modified SBA-15 prepared in Example 5 of the present invention and the unmodified organic ligand SBA-15.

[0035] Figure 5 This is the pore size distribution diagram of the organic ligand-modified SBA-15 prepared in Example 5 of the present invention and the unmodified organic ligand SBA-15.

[0036] Figure 6 This is a SEM mapping image of the thermal catalytic CO2 hydrogenation to formic acid catalyst prepared in Example 7 of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose of the invention, technical solution and technical effects of the present invention more clearly understood, the technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0038] Example 1

[0039] Weigh 200 mg of SBA-15 and disperse it in 50 mL of toluene. Add 200 μL of 3-aminopropyltrimethoxysilane dropwise. Transfer to an 80°C oil bath and reflux for 10 h to obtain a triaminopropyltrimethoxysilane-modified SBA-15 carrier.

[0040] 100 mg of 3-aminopropyltrimethoxysilane-modified SBA-15 carrier was dispersed into 50 mL of a mixed solution of chloroiridic acid hexahydrate (0.01 mmol) and triphenylphosphine (0.06 mmol), and the mixture was reacted for 6 h before filtering, washing, and drying to obtain a thermal catalytic CO2 hydrogenation catalyst for formic acid. The drying was performed in vacuum at a temperature of 64°C and a drying time of 11 h.

[0041] like Figure 1 As shown, SBA-15 is pre-modified with 3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane is covalently grafted on the surface of the carrier SBA-15 by chemical method, one end of the organic ligand 3-aminopropyltrimethoxysilane is uniformly grafted on the surface of the carrier, and the other end is coordinated with the transition metal single atom. Such distribution can effectively promote the dispersion of transition metal iridium, so that the transition metal is uniformly distributed on the catalyst carrier in a single atomic state, and the framework structure formed thereby improves the atomic utilization rate of the transition metal.

[0042] like Figure 2 FIG. 4 is an infrared spectrum of the organic ligand-modified SBA-15 carrier prepared in this example. The appearance of characteristic peaks of CH and NH bonds proves the successful modification of SBA-15 by 3-aminopropyltrimethoxysilane.

[0043] Figure 2 The SBA-15 line in the middle refers to: the other contents are the same as those in this embodiment, wherein 200 μL of 3-aminopropyltrimethoxysilane organic ligand is not added.

[0044] like Figure 3 As shown in the figure, it is the CO2 programmed temperature desorption diagram of the organic ligand modified SBA-15 and the unmodified organic ligand SBA-15 prepared in this example. The amino group in the organic ligand modified carrier provides an active site for CO2 adsorption, and a locally enriched CO2 environment is generated near the transition metal single atom, thereby showing a larger CO2 desorption amount, which indicates that the atomic utilization of the transition metal is improved.

[0045] Example 2

[0046] 200 mg of carbon material was weighed and dispersed in 50 mL of toluene, 300 μL of 3-aminopropyltrimethoxysilane was added dropwise, and the mixture was transferred to an oil bath at 80°C and refluxed for 10 h to obtain a carbon support modified with 3-aminopropyltrimethoxysilane.

[0047] 100 mg of 3-aminopropyltrimethoxysilane-modified carbon support was dispersed in 50 mL of a mixed solution of chloroiridic acid hexahydrate (0.01 mmol) and triphenylphosphine (0.06 mmol), and the mixture was reacted for 4 h, filtered, washed, and dried to obtain a thermal catalytic CO2 hydrogenation catalyst for formic acid. The drying was performed in vacuum, the drying temperature was 63°C-68°C, and the drying time was 14 h.

[0048] Example 3

[0049] Weigh 200 mg of SBA-15 and disperse it in 50 mL of toluene. Add 300 μL of aminophenyltrimethoxysilane dropwise. Transfer to an oil bath at 80°C and reflux for 8 h to obtain aminophenyltrimethoxysilane-modified SBA-15.

[0050] Weigh 100 mg of aminophenyltrimethoxysilane-modified SBA-15 and disperse it in 50 mL of a mixed solution of chloroiridic acid hexahydrate (0.01 mmol) and triphenylphosphine (0.06 mmol). After reacting for 4 hours, filter, wash, and dry to obtain a thermal catalytic CO2 hydrogenation catalyst for formic acid. The drying is vacuum drying, the drying temperature is 66°C, and the drying time is 13 hours.

[0051] Example 4

[0052] 200 mg of carbon material was weighed and dispersed in 50 mL of toluene, 300 μL of aminophenyltrimethoxysilane was added dropwise, and the mixture was transferred to an oil bath at 80° C. and refluxed for 6 h to obtain SBA-15 modified with aminophenyltrimethoxysilane.

[0053] 100 mg of aminophenyltrimethoxysilane-modified carbon material was dispersed in 50 mL of a mixed solution of chloroiridic acid hexahydrate (0.01 mmol) and triphenylphosphine (0.06 mmol), and the mixture was reacted for 4 h, filtered, washed, and dried to obtain a thermal catalytic CO2 hydrogenation catalyst for formic acid. The drying was performed in vacuum at a temperature of 62°C and a drying time of 12 h.

[0054] Example 5

[0055] Weigh 200 mg of SBA-15 and disperse it in 50 mL of toluene. Add 600 μL of 3-aminopropyltrimethoxysilane dropwise, transfer to an oil bath at 80 °C and reflux for 8 h to obtain SBA-15 modified with 3-aminopropyltrimethoxysilane.

[0056] 100 mg of 3-aminopropyltrimethoxysilane-modified SBA-15 was weighed and dispersed into a mixed solution of 50 mL of trichloroaluminium (0.01 mmol) and triphenylphosphine (0.05 mmol), reacted for 4 h, filtered, washed, and dried to obtain a thermal catalytic CO2 hydrogenation catalyst for formic acid. The drying was vacuum drying at a drying temperature of 68 ° C and a drying time of 10 h.

[0057] Figure 4 and Figure 5 The N2 adsorption-desorption isotherms and pore size distribution of the organic ligand-modified SBA-15 prepared in this example and the unmodified organic ligand SBA-15 in comparative example 1 show that, relative to the unmodified organic ligand SBA-15, the specific surface area and pore size of the carrier are significantly reduced after the introduction of triaminopropyltrimethoxysilane, proving the successful introduction of triaminopropyltrimethoxysilane.

[0058] Figure 4 and Figure 5 The SBA-15 line in the middle refers to: the other contents are the same as those in this embodiment, wherein 600 μL of 3-aminopropyltrimethoxysilane organic ligand is not added.

[0059] Example 6

[0060] Weigh 200 mg of SBA-15 and disperse it in 50 mL of toluene. Add 300 μL of N-methyl-3-aminopropyltrimethoxysilane dropwise. Transfer to an 80°C oil bath and reflux for 10 h to obtain SBA-15 modified with N-methyl-3-aminopropyltrimethoxysilane.

[0061] 100 mg of SBA-15 modified with N-methyl-3-aminopropyltrimethoxysilane was dispersed in a mixed solution of 50 mL of chloroiridic acid hexahydrate (0.01 mmol) and triphenylphosphine (0.05 mmol), and the mixture was reacted for 6 h before filtering, washing, and drying to obtain a thermal catalytic CO2 hydrogenation catalyst for formic acid. The drying was performed in vacuum at a temperature of 60°C and a drying time of 15 h.

[0062] Example 7

[0063] 200 mg of SBA-15 was weighed and dispersed in 50 mL of toluene, 400 μL of 3-aminopropyltrimethoxysilane was added dropwise, and the mixture was transferred to an oil bath at 80°C and refluxed for 8 h to obtain a carbon material modified with 3-aminopropyltrimethoxysilane.

[0064] 100 mg of 3-aminopropyltrimethoxysilane-modified SBA-15 was dispersed in 50 mL of a mixed solution of ruthenium trichloride (0.03 mmol) and triphenylphosphine (0.15 mmol), and the mixture was reacted for 4 h, filtered, washed, and dried to obtain a thermal catalytic CO2 hydrogenation catalyst for formic acid. The drying was performed in vacuum at a temperature of 65 ° C and a drying time of 12 h.

[0065] The conventional preparation method of ruthenium trichloride is to add metallic ruthenium powder into 6 mol / L hydrochloric acid. At this time, RuO4 reacts with hydrochloric acid to generate chlororuthenic acid (H2RuC16). The obtained chlororuthenic acid is then heated and concentrated, and a dark brown RuCl3 precipitate is precipitated in the solution. The precipitate is washed with a small amount of deionized water and dried in a vacuum at 50°C.

[0066] Figure 6 This is the element mapping diagram of the thermal catalytic CO2 hydrogenation to formic acid catalyst prepared in this example. It can be seen from the figure that N, P and Ru elements are evenly distributed on the carrier.

[0067] Example 8

[0068] 200 mg of carbon material was weighed and dispersed in 50 mL of toluene, 600 μL of 3-aminopropyltrimethoxysilane was added dropwise, and the mixture was transferred to an oil bath at 80° C. and refluxed for 4 h to obtain a carbon material modified with 3-aminopropyltrimethoxysilane.

[0069] 100 mg of 3-aminopropyltrimethoxysilane-modified carbon material was dispersed in 50 mL of a mixed solution of ruthenium trichloride (0.03 mmol) and triphenylphosphine (0.15 mmol), and the mixture was reacted for 6 h, filtered, washed, and dried to obtain a thermal catalytic CO2 hydrogenation catalyst for formic acid. The drying process was vacuum drying, the drying temperature was 61 ° C, and the drying time was 12 h.

[0070] Example 9

[0071] Weigh 200 mg of CeO2 and disperse it in 50 mL of toluene. Add 300 μL of 3-aminopropyltrimethoxysilane dropwise. Transfer to an 80°C oil bath and reflux for 10 h to obtain 3-aminopropyltrimethoxysilane-modified CeO2.

[0072] 100 mg of 3-aminopropyltrimethoxysilane-modified CeO2 was weighed and dispersed into 50 mL of a mixed solution of ruthenium trichloride (0.03 mmol) and triphenylphosphine (0.15 mmol), and after reacting for 6 h, the mixture was filtered, washed, and dried to obtain a thermal catalytic CO2 hydrogenation catalyst for formic acid. The drying process was vacuum drying, the drying temperature was 65 ° C, and the drying time was 12 h.

[0073] Example 10

[0074] 200 mg of SBA-15 was weighed and dispersed in 50 mL of toluene, 400 μL of 3-aminopropyltrimethoxysilane was added dropwise, and the mixture was transferred to an oil bath at 80°C and refluxed for 8 h to obtain a carbon material modified with 3-aminopropyltrimethoxysilane.

[0075] 100 mg of 3-aminopropyltrimethoxysilane-modified SBA-15 was weighed and dispersed into 50 mL of a mixed solution of ruthenium trichloride (0.03 mmol) and triphenylphosphine (0.6 mmol), and after reacting for 6 h, the mixture was filtered, washed, and dried to obtain a thermal catalytic CO2 hydrogenation catalyst for formic acid. The drying was performed in vacuum at a temperature of 65 ° C and a drying time of 12 h.

[0076] Embodiment 11

[0077] Weigh 200 mg of TiO2 and disperse it in 50 mL of toluene. Add 40 μL of (N,N-dimethyl-3-aminopropyl)trimethoxysilane dropwise. Transfer to a 70 °C oil bath and reflux for 12 h to obtain (N,N-dimethyl-3-aminopropyl)trimethoxysilane-modified TiO2.

[0078] 100 mg of (N,N-dimethyl-3-aminopropyl)trimethoxysilane-modified TiO2 was dispersed in a mixed solution of 50 mL of tri(acetylacetonate)ruthenium(III) (0.03 mmol) and triphenylphosphine (0.9 mmol), reacted for 2 h, filtered, washed, and dried to obtain a thermal catalytic CO2 hydrogenation catalyst for formic acid. The drying was vacuum drying, the drying temperature was 65 ° C, and the drying time was 12 h.

[0079] Example 12

[0080] Weigh 200 mg of mesoporous carbon and disperse it in 50 mL of toluene, add 2000 μL of N,N-diethyl-3-aminopropyltrimethoxysilane dropwise, transfer to a 100 °C oil bath and reflux for 5 h to obtain TiO2 modified with N,N-diethyl-3-aminopropyltrimethoxysilane.

[0081] 100 mg of N,N-diethyl-3-aminopropyltrimethoxysilane-modified mesoporous carbon was dispersed in 50 mL of a mixed solution of ammonium hexachlororuthenate (0.03 mmol) and triphenylphosphine (0.3 mmol), and the mixture was reacted for 8 h, filtered, washed, and dried to obtain a thermal catalytic CO2 hydrogenation catalyst for formic acid. The drying was vacuum drying, the drying temperature was 65 ° C, and the drying time was 12 h.

[0082] Embodiment 13

[0083] Weigh 200 mg of ZnO and disperse it in 50 mL of toluene. Add 1000 μL of 3-(2-aminoethylamino)propyltrimethoxysilane dropwise. Transfer to a 90 °C oil bath and reflux for 9 h to obtain 3-(2-aminoethylamino)propyltrimethoxysilane-modified TiO2.

[0084] 100 mg of 3-(2-aminoethylamino)propyltrimethoxysilane-modified ZnO was dispersed into 50 mL of a mixed solution of hydrated iridium trichloride (0.03 mmol) and triphenylphosphine (0.3 mmol), and the mixture was reacted for 5 h, filtered, washed, and dried to obtain a thermal catalytic CO2 hydrogenation catalyst for formic acid. The drying was performed in vacuum, the drying temperature was 65°C, and the drying time was 12 h.

[0085] Embodiment 14

[0086] Other contents are as in Example 1, wherein the organic ligand is 3-(2-aminoethylamino)propyltrimethoxysilane, and the transition metal ion precursor is ammonium hexachlororuthenate.

[0087] Embodiment 15

[0088] Other contents are as in Example 1, wherein the organic ligand is diethylenetriaminopropyltrimethoxysilane, and the transition metal ion precursor is sodium iridium chloride.

[0089] Example 16

[0090] Other contents are as in Example 1, wherein the organic ligand is 2-(diphenylphosphino)ethyltriethoxysilane, and the transition metal ion precursor is iridium acetate.

[0091] Application Example 1 Thermal Catalytic CO2 Hydrogenation to Formic Acid Reaction

[0092] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 8h. After testing, the TON of formic acid generated was 350 and the TOF value was 44h -1 .

[0093] Application Example 2 Thermal Catalytic CO2 Hydrogenation to Formic Acid Reaction

[0094] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 30 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 6 MPa; P CO2 / P H2=37 / 63; reaction temperature 100℃; reaction time 8h. After testing, the TON of formic acid generated was 140 and the TOF value was 17h -1 .

[0095] Application Example 3 Thermal Catalytic CO2 Hydrogenation to Formic Acid Reaction

[0096] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 80°C; reaction time 8h. After testing, the TON of formic acid generated was 16 and the TOF value was 2h -1 .

[0097] Application Example 4 Thermal Catalytic CO2 Hydrogenation to Formic Acid Reaction

[0098] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; a total pressure of 7 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 8h. After testing, the TON of formic acid generated was 62 and the TOF value was 8h -1 .

[0099] Application Example 5 Thermal Catalytic CO2 Hydrogenation to Formic Acid Reaction

[0100] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 6.3 mL of triethylamine; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 8h. After testing, the TON of formic acid generated was 71 and the TOF value was 9h -1 .

[0101] Application Example 6 Thermal Catalytic CO2 Hydrogenation to Formic Acid Reaction

[0102] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 1.26 g of sodium bicarbonate; total pressure 6 MPa; P CO2 / P H2=37 / 63; reaction temperature 100℃; reaction time 8h. After testing, the TON of formic acid generated was 122 and the TOF value was 15h -1 .

[0103] Application Example 7 Thermal Catalytic CO2 Hydrogenation to Formic Acid Reaction

[0104] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 2.52 g of sodium bicarbonate; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 8h. After testing, the TON of formic acid generated was 122 and the TOF value was 15h -1 .

[0105] Application Example 8 Thermal Catalytic CO2 Hydrogenation to Formic Acid Reaction

[0106] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 1.2 g of sodium hydroxide; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 8h. After testing, the TON of formic acid generated was 122 and the TOF value was 15h -1 .

[0107] Application Example 9 Thermal Catalytic CO2 Hydrogenation to Formic Acid

[0108] The catalyst prepared in Example 7 was used to heat-catalyze the hydrogenation of CO2 to produce formic acid. The specific reaction conditions were: using a 25mL reactor; adding 15mg of catalyst; 15mL of water; 3g of potassium bicarbonate; total pressure 6MPa; PCO2 / PH2=37 / 63; reaction temperature 100°C; reaction time 8h. After testing, the TON of the generated formic acid was 127, and the TOF value was 16h -1 .

[0109] Application Example 10 Thermal Catalytic CO2 Hydrogenation to Formic Acid Reaction (Alkali-free Generation)

[0110] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 8h. After testing, the TON of formic acid generated was 24 and the TOF value was 3h -1Application Example 11 Thermal Catalytic CO2 Hydrogenation to Formic Acid

[0111] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 85°C; reaction time 8h. After testing, the TON of formic acid generated was 92 and the TOF value was 12h -1 .

[0112] Application Example 12 Thermal Catalytic CO2 Hydrogenation to Formic Acid Reaction

[0113] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 90°C; reaction time 8h. After testing, the TON of formic acid generated was 126 and the TOF value was 16h -1 .

[0114] Application Example 13 Thermal Catalytic CO2 Hydrogenation to Formic Acid Reaction

[0115] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 95°C; reaction time 8h. After testing, the TON of formic acid generated was 163 and the TOF value was 20h -1 .

[0116] Application Example 14 Thermal Catalytic CO2 Hydrogenation to Formic Acid

[0117] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 105°C; reaction time 8h. After testing, the TON of formic acid generated was 291 and the TOF value was 36h -1 .

[0118] Application Example 15 Thermal Catalytic CO2 Hydrogenation to Formic Acid Reaction

[0119] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 4h. After testing, the TON of formic acid generated was 80 and the TOF value was 20h -1 .

[0120] Application Example 16 Thermal Catalytic CO2 Hydrogenation to Formic Acid

[0121] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 6h. After testing, the TON of formic acid generated was 83 and the TOF value was 14h -1 .

[0122] Application Example 17 Thermal Catalytic CO2 Hydrogenation to Formic Acid

[0123] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 10h. After testing, the TON of formic acid generated was 114 and the TOF value was 11h -1 .

[0124] Application Example 18 Thermal Catalytic CO2 Hydrogenation to Formic Acid Reaction

[0125] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 12h. After testing, the TON of formic acid generated was 127 and the TOF value was 11h -1 .

[0126] Application Example 19 Thermal Catalytic CO2 Hydrogenation to Formic Acid

[0127] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; a total pressure of 4 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 8h. After testing, the TON of formic acid generated was 48 and the TOF value was 6h -1 .

[0128] Application Example 20 Thermal Catalytic CO2 Hydrogenation to Formic Acid

[0129] The catalyst prepared in Example 7 was used to thermally catalyze the hydrogenation of CO2 to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 5 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 8h. After testing, the TON of formic acid generated was 83 and the TOF value was 10h -1 .

[0130] Application Example 21 Thermal Catalytic CO2 Hydrogenation to Formic Acid

[0131] The catalyst prepared in Example 7 was used to thermally catalyze the hydrogenation of CO2 to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 5 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 8h. After testing, the TON of formic acid generated was 83 and the TOF value was 10h -1 .

[0132] Application Example 22 Thermal Catalytic CO2 Hydrogenation to Formic Acid

[0133] The catalyst prepared in Example 7 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; a total pressure of 7 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 8h. After testing, the TON of formic acid generated was 321 and the TOF value was 40h -1 .

[0134] Application Example 23 Thermal Catalytic CO2 Hydrogenation to Formic Acid Reaction

[0135] The catalyst prepared in Example 9 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 8h. After testing, the TON of formic acid generated was 67 and the TOF value was 8h -1 .

[0136] Application Example 24 Thermal Catalytic CO2 Hydrogenation to Formic Acid

[0137] The catalyst prepared in Example 10 was used to thermally catalyze the CO2 hydrogenation to produce formic acid. The specific reaction conditions were: using a 25 mL reactor; adding 15 mg of catalyst; 15 mL of water; 4.2 mL of triethylamine; total pressure 6 MPa; P CO2 / P H2 =37 / 63; reaction temperature 100℃; reaction time 8h. After testing, the TON of formic acid generated was 112 and the TOF value was 14h -1 .

[0138] The embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A thermal catalytic CO2 hydrogenation catalyst for preparing formic acid, comprising an active component and a carrier for carrying the active component, characterized in that: The active component is a transition metal single atom, one end of the organic ligand is grafted on the surface of the carrier, and the other end of the organic ligand is coordinated with the transition metal single atom.

2. A thermal catalytic CO2 hydrogenation catalyst for preparing formic acid according to claim 1, characterized in that: The organic ligand includes a silane coupling agent, and its molecular formula contains at least one electron-donating group; preferably, the silane coupling agent includes one or more of 3-aminopropyltrimethoxysilane, N-methyl-3-aminopropyltrimethoxysilane, (N,N-dimethyl-3-aminopropyl)trimethoxysilane, N,N-diethyl-3-aminopropyltrimethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, diethylenetriaminopropyltrimethoxysilane, aminophenyltrimethoxysilane, and 2-(diphenylphosphino)ethyltriethoxysilane.

3. A thermal catalytic CO2 hydrogenation catalyst for preparing formic acid according to claim 1 or 2, characterized in that: The carrier includes carbon material, SBA-15, or at least one of oxides of silicon, aluminum, indium, cerium, zirconium, zinc, manganese, tin, titanium, tungsten, and molybdenum; preferably, the carbon material is mesoporous carbon; the molar ratio of the organic ligand to the carrier is 0.2 to 10:1; preferably, the molar ratio of the organic ligand to the carrier is 2:

1.

4. A catalyst for preparing formic acid by thermal catalytic CO2 hydrogenation according to any one of claims 1 to 3, characterized in that: Calculated on the weight of the carrier, the content of the active component is 0.1-7.0 wt%.

5. A catalyst for preparing formic acid by thermal catalytic CO2 hydrogenation according to any one of claims 1 to 4, characterized in that: The transition metal atom is selected from ruthenium or palladium metal; preferably, the transition metal atom is selected from ruthenium metal.

6. A method for preparing a catalyst for preparing formic acid by thermal catalytic CO2 hydrogenation according to any one of claims 1 to 5, characterized in that: The steps include: (1) preparing a carrier modified with an organic ligand; (2) dispersing the organic ligand-modified carrier prepared in step (1) into a mixed solution of a transition metal precursor and triphenylphosphine, reacting for a certain period of time, filtering, washing, and drying to obtain the product.

7. The method for preparing a thermal catalytic CO2 hydrogenation catalyst for preparing formic acid according to claim 6, characterized in that: The preparation method of the organic ligand modified carrier in step (1) is: ultra-dispersing the carrier in toluene, adding the organic ligand thereto, and refluxing to obtain the organic ligand modified carrier; preferably, the reflux temperature is 70-100°C, and the reflux time is 4-12h; further preferably, the molar ratio of the organic ligand to the transition metal in the transition metal precursor is 10-200:

1.

8. The method for preparing a catalyst for preparing formic acid by thermal catalytic CO2 hydrogenation according to claim 6, characterized in that: The transition metal precursor includes at least one of tris(acetylacetonate)ruthenium(III), ammonium hexachlororuthenate, ruthenium trichloride, sodium chloroiridate, iridium acetate, hydrated iridium trichloride, and chloroiridic acid hexahydrate; and / or, the molar ratio of the triphenylphosphine to the transition metal in the transition metal precursor is 2-30:1; more preferably, the molar ratio of the two is 4-10:

1.

9. Use of the catalyst according to any one of claims 1 to 5 in the thermal catalytic CO2 hydrogenation reaction to produce formic acid.

10. A method for preparing formic acid by thermal catalytic CO2 hydrogenation, characterized in that: The hydrogenation reaction of CO2 is carried out with or without alkali, with the addition of a catalyst, using deionized water as a solvent and H2 as a reducing agent; preferably, the reaction temperature is 60-150°C, the reaction time is 4-24h, the total gas pressure is 3-10MPa, and the pressure ratio of CO2 and H2 is 0.2-5:1; preferably, the reaction temperature is 80-105°C, the reaction time is 4-12h; the total reaction gas pressure is 4-7MPa, and the pressure ratio of CO2 and H2 is 37:63.

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