A zinc-chromium-based catalyst, its preparation method and use

Abstract

The application relates to the technical field of catalysts for fine chemical products, and provides a zinc-chromium-based catalyst and a preparation method and application thereof.The method comprises the following steps: mixing a zinc salt, a chromium salt, an alkali metal salt and activated carbon, and carrying out a combustion reaction to obtain a zinc-chromium-based catalyst.Compared with a traditional preparation method, the application has the advantages of simple operation, cheap and easily-obtained raw materials, low requirement on equipment, easy batch production, no generation of a large amount of waste water in the reaction process, and wide industrialization prospect; the catalyst provided by the application does not need further reduction treatment when used, operation steps are reduced, and operation cost is reduced; the catalyst obtained by the application is applied to the synthesis of isobutanol, CO conversion rate reaches 31%, and the isobutanol selectivity in total alcohol reaches 41.4%.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysts for fine chemical products, in particular to a zinc-chromium-based catalyst and a preparation method and application thereof. BACKGROUND

[0002] Isobutanol is a basic organic chemical raw material, which is widely used in the synthesis of rubber, the manufacture of special chemicals such as medicines and fragrances; as a solvent, it can be used for rare earth purification; as a fuel additive, it can replace methyl tert-butyl ether (MTBE) as an oxidizing agent added to gasoline, or mixed with diesel to reduce PM2.5 values. In the route of directly preparing isobutanol from synthesis gas, the catalyst system mainly includes: alkali metal modified ZnCr-based high-temperature methanol catalyst, Cu-based low-temperature methanol catalyst and ZrO2-based catalyst, etc. The alkali metal modified ZnCr-based high-temperature catalyst has attracted widespread attention due to its high isobutanol selectivity and long catalyst life. At present, such catalysts usually adopt a coprecipitation method to obtain a basic catalyst, and then add an alkali metal additive through solution impregnation to obtain the final catalyst. This catalyst preparation method has the disadvantages of complicated process, large waste water and waste gas discharge, and long preparation time. Therefore, it is necessary to find an efficient and environmentally friendly isobutanol catalyst preparation method.

[0003] Among the many alternative methods, solution combustion method is a good one. The literature (Materials Letters, 1990, 10(1,2): 6-12) reported the preparation of La(Sr)CrO3 and La(Sr)MnO3 by combustion method with glycine-nitrate as precursor, and found that the regulation of the ratio of the precursor can get high specific surface area, highly uniform powder samples. The literature (Journal of Materials Processing Technology, 2008, 208: 415-422) respectively with urea, citric acid and glycine as combustion agent by flash combustion, citrate gel decomposition and glycine combustion method prepared high-purity Y2O3 and Yb-Y2O3 powder. The literature (J. Phys. Chem. C, 2013, 117: 24417-24427) reported the preparation of Ni nanocrystals by solution combustion method with nickel nitrate and glycine as precursor, and the reaction mechanism and the structure change of the combustion process were systematically studied, which provided theoretical guidance for expanding the application range of solution combustion method. The patent (CN108144597A) disclosed a method for preparing erbium-doped titanium dioxide / diatomite composite photocatalyst by solution combustion method. The patent (CN107486204A) disclosed a method for preparing palladium-rare earth perovskite automobile exhaust catalyst by combustion method and product application. It is found that although the use of organic acid, urea or amino acid as combustion agent simplifies the preparation process of the catalyst, the combustion agent is expensive, and the economy of the overall catalyst preparation process is not high. In addition, the sample obtained by combustion needs to be further calcined, so the catalyst preparation process is still complicated. Therefore, it is of great significance to provide a preparation method of isobutanol catalyst which is simple and low in cost. SUMMARY

[0004] The present application aims to overcome the problems in the prior art and provide a zinc-chromium-based catalyst, a preparation method and application thereof.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions.

[0006] The present application provides a preparation method of a zinc-chromium-based catalyst, comprising the following steps:

[0007] Mixing zinc salt, chromium salt, alkali metal salt and activated carbon, and carrying out combustion reaction to obtain the zinc-chromium-based catalyst.

[0008] Preferably, the zinc salt is one or more of zinc nitrate, zinc acetate and zinc oxide; and the chromium salt is one or more of chromium nitrate, chromium acetate and chromium trioxide.

[0009] As preferred, the alkali metal salt is potassium salt and / or cesium salt; the potassium salt is anhydrous potassium carbonate or potassium nitrate; the cesium salt is cesium carbonate or cesium nitrate.

[0010] As preferred, the molar ratio of the zinc salt and the chromium salt is 0.8-1.5:1; the molar ratio of the alkali metal in the alkali metal salt to the zinc salt is 0.02-0.12:1.

[0011] As preferred, the mass ratio of the activated carbon to the zinc salt is 0.20-0.64:1.

[0012] As preferred, the temperature of the combustion reaction is 300-330℃, and the time of the combustion reaction is 20-100min.

[0013] The application further provides a zinc-chromium-based catalyst prepared by the preparation method.

[0014] The application further provides an application of the zinc-chromium-based catalyst in synthesis of isobutanol.

[0015] The application further provides a method for synthesizing isobutanol, comprising the following steps:

[0016] Hydrogen and carbon monoxide are subjected to a synthesis reaction under the action of the zinc-chromium-based catalyst to obtain isobutanol.

[0017] As preferred, the molar ratio of the hydrogen and the carbon monoxide is 1.5-3:1; the gas space velocity of the reaction is 2000-8000mL / (h.gcat), the temperature of the reaction is 380-420℃, and the pressure of the reaction is 8-11MPa.

[0018] The application has the following advantages:

[0019] (1) The application provides a preparation method of a zinc-chromium-based catalyst, comprising the following steps: mixing a zinc salt, a chromium salt, an alkali metal salt and activated carbon, and performing a combustion reaction to obtain a zinc-chromium-based catalyst. Compared with the traditional preparation method, the application has the advantages of simple operation, cheap and easily available raw materials, low requirement for equipment, easy batch production, no generation of a large amount of wastewater in the reaction process, and wide industrialization prospect, and is a very potential isobutanol catalyst preparation method.

[0020] (2) The catalyst provided by the application does not need further reduction treatment when used, which reduces the operation steps and the operation cost; the catalyst obtained by the application is applied to synthesis of isobutanol, the CO conversion rate reaches 31%, and the isobutanol selectivity in the total alcohol reaches 41.4%. DETAILED DESCRIPTION

[0021] The application provides a preparation method of a zinc-chromium-based catalyst, comprising the following steps:

[0022] The zinc salt, the chromium salt, the alkali metal salt and the activated carbon are mixed to carry out a combustion reaction to obtain the zinc-chromium-based catalyst.

[0023] In the present application, the zinc salt is preferably one or more of zinc nitrate, zinc acetate and zinc oxide; and the chromium salt is preferably one or more of chromium nitrate, chromium acetate and chromium trioxide.

[0024] In the present application, the alkali metal salt is preferably a potassium salt and / or a cesium salt; the potassium salt is preferably anhydrous potassium carbonate or potassium nitrate; and the cesium salt is preferably cesium carbonate or cesium nitrate.

[0025] In the present application, the molar ratio of the zinc salt to the chromium salt is preferably 0.8-1.5:1, further preferably 0.9-1.4:1, and more preferably 1.1-1.2:1; and the molar ratio of the alkali metal in the alkali metal salt to the zinc salt is preferably 0.02-0.12:1, further preferably 0.05-0.10:1, and more preferably 0.07-0.08:1.

[0026] In the present application, the mass ratio of the activated carbon to the zinc salt is preferably 0.20-0.64:1, further preferably 0.30-0.50:1, and more preferably 0.35-0.45:1.

[0027] In the present application, the mixing is preferably ball milling, the rotation speed of the ball milling is preferably 200-260 r / min, further preferably 210-240 r / min, and more preferably 220-230 r / min; and the ball milling time is preferably 15-120 min, further preferably 30-100 min, and more preferably 50-80 min.

[0028] In the present application, the temperature of the combustion reaction is preferably 300-330℃, further preferably 310-320℃, and more preferably 312-318℃; and the combustion reaction time is preferably 20-100 min, further preferably 30-90 min, and more preferably 40-80 min.

[0029] In the present application, after the combustion reaction, the obtained sample is sequentially ground, sieved and tablet-pressed to obtain the zinc-chromium-based catalyst.

[0030] In the present application, the mesh number of the grinding is preferably equal to or greater than 200 mesh, and further preferably equal to or greater than 300 mesh; and before use of the catalyst, crushing is required, and the mesh number of the crushing is preferably 30-60 mesh, further preferably 35-55 mesh, and more preferably 40-50 mesh.

[0031] In the present application, with the proceeding of the combustion reaction, the potassium salt reacts to generate potassium oxide, the cesium salt reacts to generate cesium oxide, the zinc salt reacts to generate zinc oxide, and the chromium salt reacts to generate chromium oxide.

[0032] The present application also provides the zinc-chromium-based catalyst prepared by the preparation method.

[0033] The present application also provides the application of the zinc-chromium-based catalyst in the synthesis of isobutanol.

[0034] The present application also provides a method for synthesizing isobutanol, comprising the following steps:

[0035] The hydrogen and carbon monoxide are subjected to a synthesis reaction under the action of the zinc-chromium-based catalyst to obtain isobutanol.

[0036] In the present application, the molar ratio of the hydrogen and carbon monoxide is preferably 1.5-3:1, further preferably 2-2.5:1, and more preferably 2.2-2.3:1; the gas space velocity of the reaction is preferably 2000-8000 mL / (h.gcat), further preferably 3000-7000 mL / (h.gcat), and more preferably 4000-6000 mL / (h.gcat); the temperature of the reaction is preferably 380-420℃, further preferably 390-410℃, and more preferably 395-405℃; and the pressure of the reaction is preferably 8-11 MPa, further preferably 9-10 MPa, and more preferably 9.2-9.8 MPa.

[0037] The technical solutions provided by the present application are described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application.

[0038] Example 1

[0039] 0.1 mol of zinc nitrate, 0.1 mol of chromium nitrate, 0.006 mol of anhydrous potassium carbonate and 7.77 g of activated carbon are mixed, ball-milled at a rotating speed of 230 r / min for 30 min, and subjected to a combustion reaction at 300℃ for 50 min, and then the obtained sample is ground to 300 mesh, pressed into a tablet after sieving, and broken to 55 mesh to obtain the zinc-chromium-based catalyst.

[0040] The zinc-chromium-based catalyst was loaded into a fixed bed reactor, and hydrogen and carbon monoxide were introduced (the molar ratio of hydrogen to carbon monoxide was 1.5:1), and the reaction was carried out at a gas space velocity of 5000 mL / (h-gcat), a temperature of 400°C, and a pressure of 10.0 MPa. It was found through testing that the conversion rate of CO (mol) was 28.00%, the total alcohol selectivity (Cmol(Cmol represents "carbon mole", i.e., the product composition is expressed in terms of the carbon mole percentage of each product)) was 48.06%, and the selectivity of isobutanol in the total alcohol (wt.) was 38.4%.

[0041] Example 2

[0042] The zinc-chromium-based catalyst was prepared by mixing 0.1 mol of zinc acetate, 0.077 mol of chromium acetate, 0.005 mol of anhydrous potassium carbonate, and 4.95 g of activated carbon, ball milling at a speed of 220 r / min for 30 min, and then performing a combustion reaction on the obtained mixture at 310°C for 30 min. The obtained sample was ground to 200 mesh, tableted after sieving, and broken to 50 mesh.

[0043] The zinc-chromium-based catalyst was loaded into a fixed bed reactor, and hydrogen and carbon monoxide were introduced (the molar ratio of hydrogen to carbon monoxide was 1.8:1), and the reaction was carried out at a gas space velocity of 4000 mL / (h-gcat), a temperature of 380°C, and a pressure of 10.0 MPa. It was found through testing that the conversion rate of CO (mol) was 25.00%, the total alcohol selectivity (Cmol(Cmol represents "carbon mole", i.e., the product composition is expressed in terms of the carbon mole percentage of each product)) was 55.06%, and the selectivity of isobutanol in the total alcohol (wt.) was 26.4%.

[0044] Example 3

[0045] The zinc-chromium-based catalyst was prepared by mixing 0.07 mol of zinc nitrate, 0.03 mol of zinc acetate, 0.088 mol of chromium nitrate, 0.002 mol of anhydrous potassium carbonate, 0.0015 mol of cesium carbonate, and 6.28 g of activated carbon, ball milling at a speed of 210 r / min for 15 min, and then performing a combustion reaction on the obtained mixture at 300°C for 80 min. The obtained sample was ground to 300 mesh, tableted after sieving, and broken to 35 mesh.

[0046] The zinc-chromium-based catalyst was loaded into a fixed bed reactor, and hydrogen and carbon monoxide were introduced (the molar ratio of hydrogen to carbon monoxide was 2.1:1), and the reaction was carried out at a gas space velocity of 3000 mL / (h-gcat), a temperature of 410°C, and a pressure of 9.5 MPa. It was found through testing that the conversion rate of CO (mol) was 27.50%, the total alcohol selectivity (Cmol(Cmol represents "carbon mole", i.e., the product composition is expressed in terms of the carbon mole percentage of each product)) was 52.06%, and the selectivity of isobutanol in the total alcohol (wt.) was 25.8%.

[0047] Example 4

[0048] The zinc-chromium-based catalyst was prepared by mixing 0.1 mol of zinc nitrate, 0.07 mol of chromium nitrate, 0.029 mol of chromium acetate, 0.01 mol of potassium nitrate, and 4.36 g of activated carbon, ball milling at a speed of 220 r / min for 60 min, and then performing a combustion reaction on the obtained mixture at 300°C for 60 min. The obtained sample was ground to 200 mesh, tableted after sieving, and broken to 35 mesh.

[0049] The zinc-chromium-based catalyst was loaded into a fixed bed reactor, and hydrogen and carbon monoxide were introduced (the molar ratio of hydrogen to carbon monoxide was 2.3:1), and the reaction was carried out at a gas space velocity of 2000 mL / (h-gcat), a temperature of 390°C, and a pressure of 11.0 MPa. It was found through testing that the conversion rate of CO (mol) was 31.00%, the total alcohol selectivity (Cmol(Cmol represents "carbon mole", i.e., the product composition is expressed in terms of the carbon mole percentage of each product)) was 51.05%, and the selectivity of isobutanol in the total alcohol (wt.) was 41.4%.

[0050] Example 5

[0051] The zinc-chromium-based catalyst was prepared by mixing 0.1 mol of zinc oxide, 0.084 mol of chromium oxide, 0.005 mol of anhydrous potassium carbonate, and 5.20 g of activated carbon, ball milling at a speed of 200 r / min for 120 min, and then performing a combustion reaction on the obtained mixture at 310°C for 100 min. The obtained sample was ground to 300 mesh, tableted after sieving, and broken to 60 mesh.

[0052] The zinc-chromium-based catalyst was loaded into a fixed bed reactor, and hydrogen and carbon monoxide were introduced (the molar ratio of hydrogen to carbon monoxide was 3.0:1), and the reaction was carried out at a gas space velocity of 6000 mL / (h-gcat), a temperature of 400°C, and a pressure of 10.0 MPa. It was found through testing that the conversion rate of CO (mol) was 24.00%, the total alcohol selectivity (Cmol(Cmol represents "carbon mole", i.e., the product composition is expressed in terms of the carbon mole percentage of each product)) was 72.06%, and the selectivity of isobutanol in the total alcohol (wt.) was 24.6%.

[0053] Example 6

[0054] The zinc-chromium-based catalyst was prepared by mixing 0.05 mol of zinc nitrate, 0.05 mol of zinc oxide, 0.092 mol of chromium acetate, 0.004 mol of anhydrous potassium carbonate, 0.003 mol of cesium nitrate, and 4.33 g of activated carbon, ball-milling at a speed of 230 r / min for 60 min, carrying out a combustion reaction on the obtained mixture at 300°C for 90 min, grinding the obtained sample to 200 mesh, tabletting after sieving, and breaking to 50 mesh.

[0055] The zinc-chromium-based catalyst was loaded into a fixed bed reactor, and hydrogen and carbon monoxide were introduced (the molar ratio of hydrogen to carbon monoxide was 1.9:1), and the reaction was carried out at a gas space velocity of 3500 mL / (h-gcat), a temperature of 410°C, and a pressure of 8.0 MPa. It was found through testing that the conversion rate of CO (mol) was 29.00%, the total alcohol selectivity (Cmol(Cmol represents "carbon mole", i.e., the product composition is expressed in terms of the carbon mole percentage of each product)) was 54.06%, and the selectivity of isobutanol in the total alcohol (wt.) was 34.2%.

[0056] Example 7

[0057] The zinc-chromium-based catalyst was prepared by mixing 0.05 mol of zinc nitrate, 0.05 mol of zinc oxide, 0.092 mol of chromium acetate, 0.004 mol of anhydrous potassium carbonate, 0.003 mol of cesium nitrate, and 4.33 g of activated carbon, ball-milling at a speed of 230 r / min for 60 min, carrying out a combustion reaction on the obtained mixture at 300°C for 90 min, grinding the obtained sample to 200 mesh, tabletting after sieving, and breaking to 50 mesh.

[0058] The zinc-chromium-based catalyst was loaded into a fixed bed reactor, and hydrogen and carbon monoxide were introduced (the molar ratio of hydrogen to carbon monoxide was 2.3:1), and the reaction was carried out at a gas space velocity of 5000 mL / (h-gcat), a temperature of 400°C, and a pressure of 10.0 MPa. It was found through testing that the conversion rate of CO (mol) was 16.00%, the total alcohol selectivity (Cmol(Cmol represents "carbon mole", i.e., the product composition is expressed in terms of the carbon mole percentage of each product)) was 40.06%, and the selectivity of isobutanol in the total alcohol (wt.) was 22.2%.

[0059] Example 8

[0060] The zinc-chromium-based catalyst was prepared by mixing 0.1 mol of zinc nitrate, 0.077 mol of chromium nitrate, 0.021 mol of chromium oxide, 0.006 mol of anhydrous potassium carbonate, and 3.98 g of activated carbon, ball milling at a speed of 225 r / min for 60 min, and then performing a combustion reaction on the obtained mixture at 320°C for 20 min. The obtained sample was ground to 200 mesh, tableted after sieving, and broken to 35 mesh.

[0061] The zinc-chromium-based catalyst was loaded into a fixed bed reactor, and hydrogen and carbon monoxide were introduced (the molar ratio of hydrogen to carbon monoxide was 2.1:1), and the reaction was carried out at a gas space velocity of 7500 mL / (h-gcat), a temperature of 420°C, and a pressure of 11.0 MPa. It was found through testing that the conversion rate of CO (mol) was 18.00%, the total alcohol selectivity (Cmol(Cmol represents "carbon mole", i.e., the product composition is expressed in terms of the carbon mole percentage of each product)) was 79.05%, and the selectivity of isobutanol in the total alcohol (wt.) was 24.6%.

[0062] Example 9

[0063] The zinc-chromium-based catalyst was prepared by mixing 0.1 mol of zinc nitrate, 0.11 mol of chromium nitrate, 0.002 mol of cesium nitrate, and 8.14 g of activated carbon, ball milling at a speed of 215 r / min for 90 min, and then performing a combustion reaction on the obtained mixture at 330°C for 80 min. The obtained sample was ground to 200 mesh, tableted after sieving, and broken to 50 mesh.

[0064] The zinc-chromium-based catalyst was loaded into a fixed bed reactor, and hydrogen and carbon monoxide were introduced (the molar ratio of hydrogen to carbon monoxide was 2.4:1), and the reaction was carried out at a gas space velocity of 8000 mL / (h.gcat), a temperature of 420°C, and a pressure of 11.0 MPa. It was found through testing that the CO conversion rate (mol) was 17.60%, the total alcohol selectivity (Cmol (Cmol represents "carbon mole", that is, the product composition is expressed in terms of carbon mole percentage of each product)) was 81.02%, and the isobutanol selectivity (wt.) in the total alcohol was 22.32%.

[0065] Example 10

[0066] 0.05 mol of zinc nitrate, 0.03 mol of zinc acetate, 0.02 mol of zinc oxide, 0.04 mol of chromium nitrate, 0.026 mol of chromium acetate, 0.02 mol of chromium oxide, 0.0015 mol of cesium carbonate, and 4.48 g of activated carbon were mixed, ball-milled at a speed of 235 r / min for 15 min, and then the obtained mixture was subjected to a combustion reaction at 300°C for 100 min. The obtained sample was ground to 300 mesh, and then tablet-shaped after sieving and crushing to 35 mesh to obtain the zinc-chromium-based catalyst.

[0067] The zinc-chromium-based catalyst was loaded into a fixed bed reactor, and hydrogen and carbon monoxide were introduced (the molar ratio of hydrogen to carbon monoxide was 1.9:1), and the reaction was carried out at a gas space velocity of 8000 mL / (h.gcat), a temperature of 420°C, and a pressure of 11.0 MPa. It was found through testing that the CO conversion rate (mol) was 21.50%, the total alcohol selectivity (Cmol (Cmol represents "carbon mole", that is, the product composition is expressed in terms of carbon mole percentage of each product)) was 83.06%, and the isobutanol selectivity (wt.) in the total alcohol was 27.36%.

[0068] It can be seen from the above examples that the preparation method provided by the present application has the advantages of simple operation, low cost and easy availability of raw materials, low requirement for equipment, easy batch production, no generation of a large amount of wastewater during the reaction process, and wide industrialization prospect. The catalyst obtained by the present application is applied to the synthesis of isobutanol, and the CO conversion rate reaches 31%, and the isobutanol selectivity in the alcohol reaches 41.4%.

[0069] In the present application, the catalyst for synthesizing isobutanol from synthesis gas is zinc-chromium oxide. The structure is mainly composed of zinc oxide and non-stoichiometric spinel. The formation of non-stoichiometric spinel structure is closely related to temperature (Fuel Chemistry, 2013, 41(6): 703-709), and the interaction between zinc oxide phase and non-stoichiometric spinel phase can regulate the adsorption and activation mode of synthesis gas, thereby affecting the selectivity of isobutanol (Fuel, 2018, 217: 21-30; Fuel, 2019, 253: 1570-1577). In the present application, the cheap and easily available activated carbon is used as a burning agent, and the redox reaction between the activated carbon and metal nitrate is utilized. By adjusting the ratio of the burning agent and the metal nitrate, the temperature of the combustion reaction is regulated to promote the formation of non-stoichiometric spinel structure and regulate the interaction between non-stoichiometric spinel structure and zinc oxide, thereby preparing a zinc-chromium-based catalyst with good performance.

[0070] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled persons in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A process for the preparation of a zinc-chromium based catalyst, characterized in that, The preparation method comprises the following steps: mixing zinc salt, chromium salt, alkali metal salt and activated carbon to obtain the zinc-chromium-based catalyst through combustion reaction; the zinc salt is one or both of zinc nitrate and zinc acetate; the chromium salt is one or both of chromium nitrate and chromium acetate; the alkali metal salt is potassium salt and / or cesium salt; the potassium salt is potassium carbonate or potassium nitrate; the cesium salt is cesium carbonate or cesium nitrate; the mass ratio of the activated carbon to the zinc salt is 0.20-0.64:1; the mixing is ball milling mixing, the rotation speed of the ball milling is 220-230 r / min, and the ball milling time is 50-80 min; the temperature of the combustion reaction is 300-330 ℃, and the combustion reaction time is 20-100 min.

2. The production method according to claim 1, wherein the molar ratio of the zinc salt to the chromium salt is 0.8-1.5:1; the molar ratio of the alkali metal in the alkali metal salt to the zinc salt is 0.02-0.12:

1.

3. The zinc-chromium-based catalyst prepared by the preparation method in any one of claims 1-2.

4. The application of the zinc-chromium-based catalyst in claim 3 in the synthesis of isobutanol.

5. A method of synthesizing isobutanol, characterized by, The preparation method comprises the following steps: synthesis reaction of hydrogen and carbon monoxide under the action of the zinc-chromium-based catalyst in claim 3 to obtain isobutanol.

6. The method of claim 5, wherein, the molar ratio of the hydrogen to the carbon monoxide is 1.5-3:1; the gas space velocity of the reaction is 2000-8000 mL / (h.gcat), the reaction temperature is 380-420 ℃, and the reaction pressure is 8-11 MPa.