A method for selectively reducing unsaturated compounds using hydrogen transfer

Abstract

The present invention relates to a method for selectively reducing unsaturated compounds by hydrogen transfer; unsaturated compounds are used as substrates and formaldehyde aqueous solution is used as hydrogen donors. The unsaturated compounds in a solvent are transferred and hydrogenated in a reactor containing a preactivated heterogeneous catalyst at 0-0.1 MPa, 60-120°C and in an inert atmosphere to obtain a reduced product; the method for selectively reducing unsaturated compounds by hydrogen transfer has mild reaction conditions, no high-pressure hydrogen danger, and is environmentally friendly; the hydrogen donor used is cheap and easy to obtain, has good selectivity for unsaturated compounds, and no toxic or harmful gas is produced after hydrogen supply. The catalyst used is cheap and easy to obtain, and is non-toxic and harmless.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen transfer, in particular to a method for selectively reducing unsaturated compounds by utilizing hydrogen transfer. Background Art

[0002] Selective hydrogenation reduction of unsaturated compounds is widely used in petrochemical industry, drug synthesis and other processes. At present, hydrogen is mainly used as the hydrogen source (reducing agent) for the reduction of unsaturated compounds under high pressure conditions. This traditional hydrogenation reduction often needs to be carried out under harsh (high temperature, high pressure) conditions, with high energy consumption, high pressure hydrogen gas has high requirements on equipment, and the production process is dangerous. In addition, high pressure selective hydrogenation catalysts composed of precious metals, toxic metals, toxic ligands (containing fluorine, chlorine, sulfur), etc. are often required.

[0003] Hydrogen transfer reaction refers to the reduction reaction of hydrogenation or hydrogenolysis of hydrogen acceptor using hydrogen donor as hydrogen source in the presence of catalyst. At present, the catalysts commonly used in hydrogen transfer reaction are divided into homogeneous catalysts and heterogeneous catalysts. Homogeneous catalysts are mainly salts or complexes of metals such as Ru, Rh, Pd, Ir, Mo and Ni. Homogeneous catalysts are not easy to recover and difficult to separate. Heterogeneous catalysts are easy to separate, reusable, and have many types. Ru, Rh, Pd, Ni, Cu, Mg, Al and lanthanide metals are widely used in heterogeneous hydrogen transfer reactions.

[0004] The most commonly used hydrogen donors for hydrogen transfer reactions are formic acid and formate salts, alcohols (methanol, ethanol, isopropanol), such as patent 109824630A, which uses formic acid to hydrogenate xylose to prepare furfuryl alcohol in one pot. Patent CN106928167A uses low-carbon alcohols as solvents and hydrogen donors, and zirconium compounds as catalysts to catalyze furfural to prepare furfuryl alcohol. Patent CN101348419A uses alcohols as hydrogen donors and supported ZrOx as catalysts to prepare cinnamyl alcohol; in addition, there are some other hydrogen donors, such as hydrazine, Mg / H2O, ammonia borane, hypophosphorous acid and its salts, cyclohexene, trialkylsilane and trialkylstannane. Formic acid and its salts as hydrogen donors have good selective reducibility and can reduce a variety of unsaturated compounds such as carbonyl, nitro, and carboxyl groups, but they are highly corrosive and easily corrode equipment. Low-carbon alcohols such as methanol, ethanol, ethanol and isopropanol are the most commonly used hydrogen donors of alcohols. Among them, methanol is easily generated as hydrogen donor, which is toxic and noxious gases such as CO and CH4. Ethanol is easily oxidized, and its oxidation product (aldehyde) may cause catalyst poisoning. Isopropanol is used more in hydrogen transfer reaction, and it is cheap and easy to separate, and is a more ideal hydrogen donor, but its hydrogen atom utilization rate is low, and a large amount of hydrogen donors are needed. Therefore, for the problems referred to above, the present invention provides a method for utilizing hydrogen transfer to selectively reduce unsaturated compounds. Summary of the invention

[0005] The object of the present invention is to provide a method for selectively reducing unsaturated compounds by hydrogen transfer. The method of the present invention has mild reaction conditions, no high-pressure hydrogen hazard, and is environmentally friendly. The hydrogen donor used is cheap and readily available, has good selectivity for unsaturated compounds, and no toxic or harmful gas is produced after hydrogen is supplied. The catalyst used is cheap and readily available, and is non-toxic and harmless.

[0006] The invention provides a method for selectively reducing unsaturated compounds by utilizing hydrogen transfer. The method uses unsaturated compounds as substrates and formaldehyde aqueous solution as hydrogen donor. The unsaturated compounds in a solvent are subjected to transfer hydrogenation in a reactor containing a preactivated heterogeneous catalyst at 0-0.1 MPa, 60-120° C. and in an inert atmosphere to obtain a reduced product.

[0007] Preferably, the heterogeneous catalyst is at least one of the heterogeneous catalysts containing Co, Cu, Ni, Fe, Pt, and Pd.

[0008] Preferably, the heterogeneous catalyst activation conditions are 0-0.5 MPa, 150-300° C., and a hydrogen-containing atmosphere.

[0009] Preferably, in the hydrogen donor, the molar ratio of formaldehyde to water is 1:n (1≤n<100).

[0010] Preferably, the molar ratio of formaldehyde to the unsaturated compound containing C=C, C≡C, C=O, C=N groups is (0.5-10):1.

[0011] Preferably, the hydrogen transfer reaction is carried out at 0-0.1 MPa, 60-120° C., and an inert atmosphere.

[0012] Preferably, the heterogeneous catalyst includes an active component, a promoter and a carrier; wherein the active component accounts for 1% to 66%, which is one or more of Co, Cu, Ni, Fe, Pt or Pd single substances or corresponding oxides; the promoter accounts for 5% to 40%, which is one or two of ZnO, MgO or Cs2O; the carrier accounts for 5% to 40%, which is one or more of Al2O3, SiO2, ZrO2, CeO2 or carbon molecular sieves.

[0013] Preferably, the reactor is a fixed bed or tank reactor.

[0014] Preferably, the solvent is one or more of methanol, ethanol, 1,3-dioxane, 1,4-dioxane, dichloromethane, dichloroethane, benzene, toluene or water.

[0015] Preferably, the inert atmosphere comprises one or more of nitrogen, argon or helium; the formaldehyde comprises one or more of paraformaldehyde, gaseous formaldehyde, trioxymethylene, and formaldehyde aqueous solution; and the heterogeneous catalyst is activated at 200-250°C.

[0016] The method for selectively reducing unsaturated compounds by hydrogen transfer provided by the present invention has the following improvements compared with the prior art:

[0017] 1. Compared with the existing technology of reducing unsaturated compounds using formic acid and alcohol as hydrogen donors, this method uses formaldehyde aqueous solution as hydrogen donor, which does not cause the problem of high-concentration formic acid corroding equipment. The products after hydrogen supply are only carbon dioxide and a small amount of hydrogen or only carbon dioxide, without toxic and harmful gases such as CO and CH4, which is green and environmentally friendly.

[0018] 2. The method of selectively reducing unsaturated compounds by hydrogen transfer of the present invention can reduce unsaturated groups at low pressure or normal pressure and 60-120°C. Compared with the existing technical scheme of reducing unsaturated compounds by hydrogen, the present invention has high selectivity, no risk of high-pressure hydrogen production, low equipment requirements, and reduced equipment investment. The reaction conditions are milder, energy consumption is reduced, and production costs can be reduced. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The invention provides a method for selectively reducing unsaturated compounds by utilizing hydrogen transfer. The method uses unsaturated compounds as substrates and formaldehyde aqueous solution as hydrogen donor. The unsaturated compounds in a solvent are subjected to transfer hydrogenation in a reactor containing a preactivated heterogeneous catalyst at 0-0.1 MPa, 60-120° C. and in an inert atmosphere to obtain a reduced product.

[0021] Specifically, the heterogeneous catalyst is at least one of the heterogeneous catalysts containing Co, Cu, Ni, Fe, Pt, and Pd.

[0022] Specifically, the heterogeneous catalyst activation conditions are 0-0.5 MPa, 150-300° C., and a hydrogen-containing atmosphere.

[0023] Specifically, in the hydrogen donor, the molar ratio of formaldehyde to water is 1:n (1≤n<100).

[0024] Specifically, the molar ratio of formaldehyde to the unsaturated compound containing C=C, C≡C, C=O, C=N groups is (0.5-10):1.

[0025] Specifically, the hydrogen transfer reaction is carried out at 0-0.1 MPa, 60-120° C., and an inert atmosphere.

[0026] Specifically, the heterogeneous catalyst includes an active component, an auxiliary agent and a carrier; wherein the active component accounts for 1% to 66%, which is one or more of Co, Cu, Ni, Fe, Pt or Pd single substances or corresponding oxides; the auxiliary agent accounts for 5% to 40%, which is one or two of ZnO, MgO or Cs2O; the carrier accounts for 5% to 40%, which is one or more of Al2O3, SiO2, ZrO2, CeO2 or carbon molecular sieves.

[0027] Specifically, the reactor is a fixed bed or a tank reactor.

[0028] Specifically, the solvent is one or more of methanol, ethanol, 1,3-dioxolane, 1,4-dioxane, dichloromethane, dichloroethane, benzene, toluene or water.

[0029] Specifically, the inert atmosphere includes one or more of nitrogen, argon or helium; the formaldehyde includes one or more of paraformaldehyde, gaseous formaldehyde, trioxymethylene, and formaldehyde aqueous solution; and the heterogeneous catalyst is activated at 200-250°C.

[0030] Compared with the existing technology of reducing unsaturated compounds using formic acid and alcohol as hydrogen donors, the present invention uses formaldehyde aqueous solution as hydrogen donor, which avoids the problem of high-concentration formic acid corroding equipment, and the products after hydrogen supply are only carbon dioxide and a small amount of hydrogen or only carbon dioxide, without toxic and harmful gases such as CO and CH4, which is green and environmentally friendly.

[0031] The method of selectively reducing unsaturated compounds by hydrogen transfer of the present invention can reduce unsaturated groups at low pressure or normal pressure and 60-120° C. Compared with the existing technical solution of reducing unsaturated compounds by hydrogen, the present invention has high selectivity, no risk of high-pressure hydrogen production, low equipment requirements, and reduced equipment investment. The reaction conditions are milder, energy consumption is reduced, and production costs can be reduced.

[0032] Embodiment 1

[0033] Transfer hydrogenation reduction of furfural to furfuryl alcohol:

[0034] 101) 20 ml of CuO / MgO / Al2O3 heterogeneous catalyst was placed in a fixed bed, and maintained at 0.1 MPa, 150°C, and 5% H2 / N2 atmosphere for 6 h to obtain an activated heterogeneous catalyst;

[0035] 102) The temperature of the reactor is lowered to 100° C., and the hydrogen in the reactor is replaced with nitrogen gas. After the hydrogen is completely replaced, an ethanol solution containing formaldehyde, water, and furfural (wherein the molar ratio of formaldehyde, water, and furfural is 1:2:2) is pumped into the reactor at 0.5 ml / min under normal pressure to obtain a mixture containing the reduction product furfuryl alcohol.

[0036] GC-MS and liquid chromatography were used to detect the structure and composition of the reduction product and to obtain the conversion rate. The test results are shown in Table 1.

[0037] Embodiment 2

[0038] Transfer hydrogenation reduction of cinnamaldehyde to cinnamyl alcohol:

[0039] 201) 20 ml of CuO / C heterogeneous catalyst was loaded into a fixed bed, and maintained at 0.1 MPa, 250° C., in a 5% H2 / N2 atmosphere for 4 h to obtain an activated heterogeneous catalyst;

[0040] 202) The temperature of the reactor is lowered to 60°C, and the hydrogen in the reactor is replaced by argon gas. After the hydrogen is completely replaced, a 1,3-dioxolane solution containing formaldehyde, water and cinnamaldehyde (wherein the molar ratio of formaldehyde, water and cinnamaldehyde is 1:3:1) is pumped into the reactor at 0.5 ml / min under normal pressure to obtain a mixture containing the reduction product cinnamyl alcohol.

[0041] GC-MS and liquid chromatography were used to detect the structure and composition of the reduction product and to obtain the conversion rate. The test results are shown in Table 1.

[0042] Embodiment 3

[0043] Transfer hydrogenation reduction of crotonaldehyde to crotyl alcohol:

[0044] 301) 20 ml of Cu-Pd / C heterogeneous catalyst was loaded into a fixed bed and maintained at 0.1 MPa, 180°C, and 5% H2 / N2 atmosphere for 4 h to obtain an activated heterogeneous catalyst;

[0045] 302) The temperature of the reactor was lowered to 95°C, and the hydrogen in the reactor was replaced by argon gas. After the hydrogen was completely replaced, a 1,4-dioxane solution containing formaldehyde, water and crotonaldehyde (wherein the molar ratio of formaldehyde, water and crotonaldehyde was 1:3:1.5) was pumped into the reactor at 0.6 ml / min under normal pressure to obtain a mixture containing the reduction product crotyl alcohol.

[0046] GC-MS and liquid chromatography were used to detect the structure and composition of the reduction product and to obtain the conversion rate. The test results are shown in Table 1.

[0047] Embodiment 4

[0048] Transfer hydrogenation reduction of chalcone to dihydrochalcone:

[0049] 401) 20 ml of Cu-Pt / Al2O3 heterogeneous catalyst was loaded into a fixed bed, and maintained at 0.1 MPa, 250°C, and 5% H2 / N2 atmosphere for 4 h to obtain an activated heterogeneous catalyst;

[0050] 402) The temperature of the reactor was lowered to 120°C, and the hydrogen in the reactor was replaced with argon gas. After the hydrogen was completely replaced, a benzene solution containing formaldehyde, water and chalcone (wherein the molar ratio of formaldehyde, water and chalcone was 0.5:6:1) was pumped into the reactor at 0.45 ml / min under normal pressure to obtain a mixture containing the reduction product dihydrochalcone.

[0051] GC-MS and liquid chromatography were used to detect the structure and composition of the reduction product and to obtain the conversion rate. The test results are shown in Table 1.

[0052] Embodiment 5

[0053] Transfer hydrogenation reduction of benzaldehyde to benzyl alcohol:

[0054] 501) 20 ml of Ni-ZnO / Al2O3 heterogeneous catalyst was placed in a fixed bed and maintained at 0.1 MPa, 300°C, in a 5% H2 / N2 atmosphere for 8 h to obtain an activated heterogeneous catalyst;

[0055] 502) The temperature of the reactor is lowered to 100° C., and the hydrogen in the reactor is replaced with argon and helium. After the hydrogen is completely replaced, a solution containing formaldehyde, benzaldehyde and water (wherein the molar ratio of formaldehyde, benzaldehyde and water is 10:1:50) is pumped into the reactor at 0.3 ml / min under normal pressure to obtain a mixture containing the reduction product benzyl alcohol.

[0056] GC-MS and liquid chromatography were used to detect the structure and composition of the reduction product and to obtain the conversion rate. The test results are shown in Table 1.

[0057] Embodiment 6

[0058] Transfer hydrogenation reduction of styrene to ethylbenzene:

[0059] 601) 20 ml of CuCo / SiO2 heterogeneous catalyst was loaded into a fixed bed and maintained at 0.1 MPa, 250°C, in a 5% H2 / N2 atmosphere for 6 h to obtain an activated heterogeneous catalyst;

[0060] 602) The temperature of the reactor was lowered to 100°C, and the hydrogen in the reactor was replaced by helium gas. After the hydrogen was completely replaced, an ethanol solution containing formaldehyde, water and styrene (wherein the molar ratio of formaldehyde, water and styrene was 1:1:0.5) was pumped into the reactor at 0.7 ml / min under normal pressure to obtain a mixture containing the reduction product ethyl benzene.

[0061] GC-MS and liquid chromatography were used to detect the structure and composition of the reduction product and to obtain the conversion rate. The test results are shown in Table 1.

[0062] Embodiment 7

[0063] Transfer hydrogenation reduction of phenylacetylene to ethylbenzene:

[0064] 701) 20 ml of Cu / SiO2 heterogeneous catalyst was loaded into a fixed bed, and maintained at 0.1 MPa, 250°C, in a 5% H2 / N2 atmosphere for 6 h to obtain an activated heterogeneous catalyst;

[0065] 702) The temperature of the reactor is lowered to 110°C, and the hydrogen in the reactor is replaced by helium gas. After the hydrogen is completely replaced, an ethanol solution containing formaldehyde, water, and phenylacetylene (wherein the molar ratio of formaldehyde, water, and phenylacetylene is 1:1:0.5) is pumped into the reactor at 0.5 ml / min under normal pressure to obtain a mixture containing the reduction product phenylethane.

[0066] GC-MS and liquid chromatography were used to detect the structure and composition of the reduction product and to obtain the conversion rate. The test results are shown in Table 1.

[0067] Embodiment 8

[0068] Transfer hydrogenation reduction of furfural to furfuryl alcohol:

[0069] 801) 1 g of CuO / ZnO / Al2O3 heterogeneous catalyst was added into a heated reactor, and maintained at 0.1 MPa, 200°C, in a 5% H2 / N2 atmosphere for 2 h to obtain an activated heterogeneous catalyst;

[0070] 802) The reactor temperature is lowered to 110°C, and the hydrogen in the reactor is replaced with nitrogen gas. After the hydrogen is completely replaced, 10 g of an ethanol solution containing formaldehyde, water, and furfural (wherein the molar ratio of formaldehyde, water, and furfural is 1:2:2) is added to the reactor under normal pressure. After reacting for 4 hours, the temperature is lowered to room temperature, and the reactants are taken out and filtered to obtain a furfuryl alcohol product.

[0071] GC-MS and liquid chromatography were used to detect the structure and composition of the reduction product and to obtain the conversion rate. The test results are shown in Table 1.

[0072] In the above embodiment, the molar ratio of formaldehyde to water is 1:n (1≤n<100). Under this condition, the ratio of formaldehyde to water can be any ratio. However, under the premise that the formaldehyde and water contents satisfy the above relationship, a lower water content is more beneficial to the catalyst life.

[0073] Embodiments 1 to 8 effectively reduce unsaturated compounds. The present invention only uses water containing formaldehyde as a hydrogen source. Unsaturated groups can be reduced at 60 to 120° C., and the equipment requirements are relatively low, which can reduce production costs. The catalyst can be repeatedly used and has the advantages of being non-toxic, harmless, and environmentally friendly.

[0074] Table 1 Structure, conversion rate and selectivity of unsaturated compounds and reduction products in the examples

[0075]

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for selectively reducing unsaturated compounds using hydrogen transfer, characterized in that: Using unsaturated compounds as substrates and formaldehyde aqueous solution as hydrogen donor, the unsaturated compounds in the solvent are transferred and hydrogenated in a reactor containing a preactivated heterogeneous catalyst at normal pressure, 60-120°C, and in an inert atmosphere to obtain a reduction product; The unsaturated compound includes at least one of furfural, cinnamaldehyde, crotonaldehyde, chalcone, and phenylacetylene; In the hydrogen donor, the molar ratio of formaldehyde to water is 1:n, wherein 1≤n<100.

2. The method for selectively reducing unsaturated compounds by hydrogen transfer according to claim 1, characterized in that: The heterogeneous catalyst is at least one of the heterogeneous catalysts containing Co, Cu, Ni, Fe, Pt, and Pd.

3. The method for selectively reducing unsaturated compounds by hydrogen transfer according to claim 1, characterized in that: The activation conditions of the heterogeneous catalyst are 0-0.5 MPa, 150-300° C., and a hydrogen-containing atmosphere.

4. The method for selectively reducing unsaturated compounds by hydrogen transfer according to claim 1, characterized in that: The molar ratio of formaldehyde to the unsaturated compound is (0.5-10):

1.

5. The method for selectively reducing unsaturated compounds by hydrogen transfer according to claim 1, characterized in that: The heterogeneous catalyst includes an active component, an auxiliary agent and a carrier; wherein the active component accounts for 1% to 66% and is one or more of Cu, Ni, Pt or Pd single substances or corresponding oxides; the auxiliary agent accounts for 5% to 40% and is one or two of ZnO, MgO or Cs2O; the carrier accounts for 5% to 40% and is one or more of Al2O3, SiO2, ZrO2, CeO2 or carbon molecular sieves.

6. The method for selectively reducing unsaturated compounds by hydrogen transfer according to claim 1, characterized in that: The reactor is a fixed bed or tank reactor.

7. The method for selectively reducing unsaturated compounds by hydrogen transfer according to claim 1, characterized in that: The solvent is one or more of methanol, ethanol, 1,3-dioxolane, 1,4-dioxane, dichloromethane, dichloroethane, benzene, toluene or water.

8. The method for selectively reducing unsaturated compounds by hydrogen transfer according to claim 1, characterized in that: The inert atmosphere includes one or more of nitrogen, argon or helium; the formaldehyde contained in the formaldehyde aqueous solution includes one or more of paraformaldehyde, gaseous formaldehyde and trioxymethylene; and the heterogeneous catalyst is activated at 200-250°C.

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