Tungsten oxide loaded carbon coated nickel catalyst and preparation method and application thereof

Abstract

The invention discloses a tungsten oxide loaded carbon coated nickel catalyst and a preparation method and application thereof, the catalyst comprises a carrier and an active component loaded on the carrier, the carrier is tungsten oxide containing positive pentavalent tungsten ions and positive hexavalent tungsten ions at the same time, and the active component is carbon layer coated nickel. The catalyst can be applied to preparation of ethylene glycol through catalytic conversion of cellulose, 100% conversion of the cellulose can be achieved in a water solvent only in the initial hydrogen atmosphere, the yield of ethylene glycol monomers can reach 75%, one-step conversion of the cellulose to high-value fuel is completed, and the catalyst is suitable for industrial production. The preparation and reaction processes of the catalyst have the characteristics of high efficiency, greenness, economy and reproducibility, and the industrial application prospect is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of biomass conversion catalysts, and in particular to a tungsten oxide-supported carbon-coated nickel catalyst and a preparation method and application thereof. Background Art

[0002] Biomass is a renewable, carbon-neutral resource that can be used to prepare liquid fuels and chemicals. Among them, lignocellulose consists of cellulose, hemicellulose, and lignin. Compared with lignin and hemicellulose, cellulose is an inedible biomass and is one of the most promising sustainable carbon resources. It is composed of glucose units, making it a promising raw material for the production of platform chemicals.

[0003] Ethylene glycol is the simplest polyol with a small relative molecular weight and active properties. It can undergo esterification, etherification, oxidation, acetalization and other reactions. It is a very important basic organic chemical raw material. At present, the annual consumption of ethylene glycol in the world exceeds 30 million tons. As a major producer and consumer of ethylene glycol, my country's annual consumption exceeds 20 million tons. However, traditional ethylene glycol production mainly relies on petroleum ethylene or coal as raw materials, which has the disadvantages of non-renewable raw materials, large carbon dioxide emissions, and high energy consumption. Therefore, the development of green production technology using cellulose as raw material is of great significance to achieve sustainable development.

[0004] Although catalysts play a key role in various reactions and have high activity and selectivity, their industrial applications are limited by the stability of the catalysts and the difficulty in separating and recovering the catalysts from the reaction mixture after the catalytic reaction. In order to convert cellulose completely or directly into valuable chemicals and target component fuels, the development and design of stable and efficient catalysts is the key to efficient cellulose conversion. Summary of the invention

[0005] The main purpose of the present invention is to provide a tungsten oxide-supported carbon-coated nickel catalyst which can be used for catalytic conversion of cellulose to prepare ethylene glycol and has excellent catalytic activity and target product selectivity, as well as a preparation method and application thereof.

[0006] To achieve the above object, the present invention provides a tungsten oxide-supported carbon-coated nickel catalyst, comprising a carrier and an active component supported on the carrier, wherein the carrier is tungsten oxide containing both positive pentavalent tungsten ions and positive hexavalent tungsten ions, and the active component is nickel coated with a carbon layer.

[0007] Furthermore, the content of nickel is 10-40wt%, the content of the carbon layer is 10-30wt%, and the balance is tungsten oxide.

[0008] Furthermore, the content of nickel is 30 wt %.

[0009] The present invention also provides a method for preparing the above-mentioned tungsten oxide-supported carbon-coated nickel catalyst, comprising the following steps:

[0010] (1) Preparation of active component carbon layer coated nickel

[0011] The nickel precursor salt and citric acid are added to an ethanol aqueous solution, heated and stirred to form a gel, then dried, and then calcined at ℃ under a nitrogen atmosphere, and finally acid-washed, water-washed and dried to obtain a carbon layer-coated nickel;

[0012] (2) Preparation of carrier tungsten oxide

[0013] Tungsten hexachloride is added to ethanol, mixed evenly, then heated, filtered, washed and freeze-dried to obtain tungsten oxide containing both positive pentavalent tungsten ions and positive hexavalent tungsten ions;

[0014] (3) Preparation of Catalyst

[0015] Tungsten oxide and carbon layer coated nickel are added into ethanol, and then subjected to heating, stirring, drying and reduction activation treatment to obtain the tungsten oxide supported carbon coated nickel catalyst.

[0016] Furthermore, in step (1), the molar ratio of the nickel precursor salt to citric acid is 1:1; the volume ratio of ethanol to water in the ethanol aqueous solution is 1:1; the temperature of the heating and stirring treatment is 70°C; the temperature of the drying treatment is 105°C; the specific process of the calcination treatment is: heating to 600°C at a heating rate of 2°C / min under a nitrogen atmosphere, and then calcining at this temperature for 3 hours.

[0017] Furthermore, in step (2), the mass volume ratio of tungsten hexachloride to ethanol is 3g:100mL; the temperature of the heating treatment is 160°C and the time is 36h; the temperature of the freeze-drying treatment is -48°C and the time is 7h.

[0018] Furthermore, in step (3), the temperature of the heating and stirring treatment is 60-90°C, and the time is 5 hours; the temperature of the drying treatment is 105°C, and the time is 4 hours; the air flow of the reduction activation treatment is 100 mL / min of 10% H2 / 90% N2 air flow, the temperature is 300°C, and the time is 3 hours.

[0019] The present invention also provides the use of the above-mentioned tungsten oxide-supported carbon-coated nickel catalyst in catalytic conversion of cellulose to prepare ethylene glycol.

[0020] The present invention also provides a method for preparing ethylene glycol by catalytic conversion of cellulose, comprising the following steps: putting cellulose, water and the above catalyst into a reactor, filling it with hydrogen and conducting a sealed reaction.

[0021] Furthermore, the amount of hydrogen charged is 2-5 MPa, and the reaction conditions are temperature 220-250° C. and time 2-5 h.

[0022] The catalyst of the present invention adopts tungsten oxide as a carrier and carbon-shell-wrapped nickel as an active component, which can enhance the ability of the catalyst to hydrogenolyze cellulose; the surface and interior of the tungsten oxide with positive pentavalent tungsten ions and positive hexavalent tungsten ions are rich in acid sites, large in surface area, and strong in adsorption capacity, and can fully disperse the active components, effectively realizing the C-C bond cleavage of cellulose by tungsten oxide; nickel metal and carbon-shell-wrapped nickel have unique electronic structures, and show good hydrogenation ability in the cellulose conversion process; after the carbon shell wraps the nickel metal, not only the hydrogenation ability of the catalyst is improved, but also the stability of the catalyst is significantly improved, and the sintering and loss of metal nickel are greatly reduced during the reaction process; thus, the catalyst of the present invention has a higher ethylene glycol yield for cellulose.

[0023] The beneficial effects of the present invention are embodied in:

[0024] The catalyst of the present invention can be applied to the catalytic conversion of cellulose to prepare ethylene glycol. In an aqueous solvent, only an initial hydrogen atmosphere is required to achieve 100% conversion of cellulose, and the ethylene glycol monomer yield can reach 75%, completing the one-step conversion of cellulose into a high-value fuel. The catalyst preparation and reaction process are characterized by high efficiency, greenness, economy and renewability, and have broad prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the TEM image of 1#Ni@C prepared in Example 1.

[0026] Figure 2 This is the XRD pattern of 1#Ni@C prepared in Example 1.

[0027] Figure 3 2#WO prepared in Examples 2 to 6 x And the XRD patterns of catalysts 3# to 6#.

[0028] Figure 4 The N2 adsorption-desorption isotherm diagram and pore size distribution diagram of the 3# catalyst prepared in Example 3.

[0029] Figure 5 The N2 adsorption-desorption isotherm diagram and pore size distribution diagram of catalyst #4 prepared in Example 4.

[0030] Figure 6 The N2 adsorption-desorption isotherm diagram and pore size distribution diagram of the 5# catalyst prepared in Example 5.

[0031] Figure 7 The N2 adsorption-desorption isotherm diagram and pore size distribution diagram of catalyst #6 prepared in Example 6.

[0032] Figure 8 TG and DTG graphs of 1#Ni@C prepared in Example 1.

[0033] Fig. 9 TG and DTG diagrams of catalyst #5 prepared in Example 5.

[0034] Fig.10 2#WO prepared in Example 2 x XPS graph.

[0035] Fig.11 XPS charts of catalysts #3 to #6 prepared in Examples 3 to 6. DETAILED DESCRIPTION

[0036] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0037] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or can be obtained by existing known methods; unless otherwise specified, the methods used in the examples of the present invention are methods known to those skilled in the art.

[0038] Example 1

[0039] Preparation of active component carbon layer coated nickel

[0040] The specific preparation method is as follows:

[0041] 8.7237g Ni(NO3)2·6H2O and 5.76g citric acid were added to an ethanol aqueous solution consisting of 5mL deionized water and 5mL ethanol, stirred to dissolve into a uniform solution, and then stirred at a temperature of 70°C and a rotation speed of 250r / min until a gel was formed. The formed gel was then dried at a temperature of 105°C for 72h and then ground into a solid powder. The solid powder was placed in a tubular furnace and calcined at a constant temperature of 600°C from room temperature for 3h at a heating rate of 2°C / min under a nitrogen atmosphere. After naturally cooling to room temperature, it was placed in a 1moL / L sulfuric acid solution and stirred at a speed of 500r / min for 12h. Finally, it was washed with deionized water until neutral and dried at 105°C for 12h to obtain carbon-coated nickel, recorded as Ni@C, numbered 1#, and analyzed by ICP (inductively coupled plasma test). The nickel content was 69.00wt%, and the rest was carbon layer.

[0042] Example 2

[0043] Preparation of Tungsten Oxide Support

[0044] The specific preparation method is as follows:

[0045] 3 g of tungsten hexachloride was added to 100 mL of ethanol, ultrasonically treated for 10 min, then transferred to a hydrothermal synthesis reactor and treated at 160 ° C for 36 h, then filtered, the filter cake was washed with deionized water, and dried at -48 ° C for 7 h to obtain tungsten oxide containing both positive pentavalent tungsten ions and positive hexavalent tungsten ions, recorded as WO x , numbered 2#.

[0046] Example 3

[0047] Preparation of Tungsten Oxide Supported Carbon Coated Nickel Catalyst

[0048] The specific preparation method is as follows:

[0049] 0.145 g of Ni@C prepared in Example 1 and 1 g of WO prepared in Example 2 were added. x The mixture was added to 60 mL of ethanol and stirred at a stirring speed of 300 r / min and a temperature of 60°C for 5 h, then dried at 105°C for 4 h, and finally reduced and activated at 100 mL / min of 10% H2 / 90% N2 gas flow and 300°C for 3 h to obtain a tungsten oxide-supported carbon-coated nickel catalyst with a nickel content of 10 wt%, which was recorded as 10Ni@C / WO x , numbered 3#, and its nickel content was 10.36wt% according to ICP analysis.

[0050] Example 4

[0051] Preparation of Tungsten Oxide Supported Carbon Coated Nickel Catalyst

[0052] The specific preparation method is as follows:

[0053] 0.290 g of Ni@C prepared in Example 1 and 1 g of WO prepared in Example 2 were added. x The mixture was added to 60 mL of ethanol and stirred at a stirring speed of 300 r / min and a temperature of 70°C for 5 h, then dried at 105°C for 4 h, and finally reduced and activated at 100 mL / min of 10% H2 / 90% N2 gas flow and 300°C for 3 h to obtain a tungsten oxide-supported carbon-coated nickel catalyst with a nickel content of 20 wt%, which was recorded as 20Ni@C / WO x , numbered 4#, and its nickel content was 20.09wt% according to ICP analysis.

[0054] Example 5

[0055] Preparation of Tungsten Oxide Supported Carbon Coated Nickel Catalyst

[0056] The specific preparation method is as follows:

[0057] 0.435 g of Ni@C prepared in Example 1 and 1 g of WO prepared in Example 2 were added. x Add to 60 mL of ethanol, stir at a stirring speed of 300 r / min and a temperature of 80°C for 5 h, then dry at 105°C for 4 h, and finally reduce and activate at 100 mL / min of 10% H2 / 90% N2 gas flow and 300°C for 3 h to obtain a tungsten oxide-supported carbon-coated nickel catalyst with a nickel content of 30 wt%, denoted as 30Ni@C / WO x , numbered 5#, and its nickel content was 30.74wt% according to ICP analysis.

[0058] Example 6

[0059] Preparation of Tungsten Oxide Supported Carbon Coated Nickel Catalyst

[0060] The specific preparation method is as follows:

[0061] 0.58 g of Ni@C prepared in Example 1 and 1 g of WO prepared in Example 2 were added. x Add to 60 mL of ethanol, stir at a stirring speed of 300 r / min and a temperature of 90°C for 5 h, then dry at 105°C for 4 h, and finally reduce and activate at 100 mL / min of 10% H2 / 90% N2 gas flow and 300°C for 3 h to obtain a tungsten oxide-supported carbon-coated nickel catalyst with a nickel content of 40 wt%, denoted as 40Ni@C / WO x , numbered 6#, and its nickel content was 38.86wt% according to ICP analysis.

[0062] Comparative Example 1

[0063] Preparation of comparative catalysts

[0064] This comparative example prepared the catalyst in the same manner as in Example 3, except that 0.145 g of Ni@C was replaced with 0.4955 g of Ni(NO3)2·6H2O, and finally WO with a nickel content of 10 wt% was obtained. x Supported nickel catalyst, denoted as 10Ni / WO x , numbered 1&.

[0065] Comparative Example 2

[0066] Preparation of comparative catalysts

[0067] This comparative example prepared the catalyst in the same manner as in Example 4, except that 0.145 g of Ni@C was replaced with 0.9910 g of Ni(NO3)2·6H2O, and finally WO with a nickel content of 20 wt% was obtained. x Supported nickel catalyst, denoted as 20Ni / WO x , numbered 2&.

[0068] Comparative Example 3

[0069] Preparation of comparative catalysts

[0070] This comparative example prepared the catalyst in the same manner as in Example 5, except that 0.145 g of Ni@C was replaced with 1.4865 g of Ni(NO3)2·6H2O, and finally WO with a nickel content of 30 wt% was obtained. x Supported nickel catalyst, denoted as 30Ni / WO x , numbered 3&.

[0071] Comparative Example 4

[0072] Preparation of comparative catalysts

[0073] This comparative example prepared the catalyst in the same manner as in Example 6, except that 0.145 g of Ni@C was replaced with 1.9820 g of Ni(NO3)2·6H2O, and finally WO with a nickel content of 40 wt% was obtained. x Supported nickel catalyst, denoted as 40Ni / WO x , numbered 4&.

[0074] Comparative Example 5

[0075] Preparation of comparative catalysts

[0076] This comparative example prepared the catalyst in the same manner as in Example 5, except that 1 g WO x It was replaced with 1gWO3, and the final catalyst was recorded as 30Ni@C / WO3 and numbered 5&.

[0077] Experimental Example 1

[0078] Structure Determination of Tungsten Oxide Supported Carbon-Coated Nickel Catalyst

[0079] The 1#Ni@C prepared in Example 1 and the 2#carrier WO prepared in Example 2 x The structural analysis of the catalysts 3#, 4#, 5#, and 6# prepared in Examples 3, 4, 5, and 6 was performed, and the results were as follows: Figures 1 to 11 As shown:

[0080] See also Figure 1 and Figure 2 In the TEM image of Ni@C, it can be seen that there is an obvious carbon layer around the metallic nickel. In addition, no nickel oxide peak was found in its XRD image, indicating the successful preparation of carbon-layer-coated nickel.

[0081] See also Figure 3 In the XRD spectra of the support and catalyst, the corresponding WOx The characteristic diffraction peaks of WO x The carrier was successfully prepared; in the XRD spectrum of the catalyst, peaks corresponding to metallic nickel were detected at 2θ=44.6°, 52.0° and 76.3°, indicating that metallic nickel was successfully loaded on the carrier, and the peak intensity was low, indicating that the metal dispersion was good.

[0082] See also Figures 4 to 7 According to the IUPAC classification, it can be seen that all the tungsten oxide-supported carbon-coated nickel catalysts prepared in various embodiments of the present invention have type IV isotherms, and their hysteresis loops all belong to the H3 type, indicating that the catalysts are all mesoporous ordered channels.

[0083] See also Figure 8 and 9 It can be seen that the weight loss process of the precursor Ni@C and the catalyst 30Ni@C / WOx is similar. The loss of water may occur at 180℃; the rising curve at 180-300℃ may be due to the oxidation of metal nickel to form metal oxides, which leads to an increase in weight. This also shows that the pyrolysis of citric acid promotes the reduction of metals, and also shows that the reduction effect of the catalyst is significant.

[0084] See also Fig.10 , W of carrier WOx 5+ , W 6+ Similar proportions, see Fig.11 , after loading the active components W 5+ The double peaks at 38.7eV and 36.6eV are attributed to W 6+ 4f 5 / 2 and 4f 7 / 2 , while the double peaks at 37.9 eV and 35.7 eV correspond to W 5+ 4f 5 / 2 and 4f 7 / 2 The increase of Ni content leads to the 5+ However, when the Ni content increases from 30% to 40%, W 5+ The content of was slightly decreased, which was consistent with the changing trend of the catalytic results.

[0085] Example 2

[0086] Performance test of tungsten oxide supported carbon coated nickel catalyst for catalytic conversion of cellulose to ethylene glycol

[0087] Test method: Weigh 0.2g cellulose, 0.2g catalyst, and 20mL deionized water into a high-pressure reactor, fill with 2-5MPa initial hydrogen pressure, and then seal and react for 2-5h at 220-250℃ and stirring rate of 500r / min, then filter the reaction product to obtain a liquid product, and finally perform quantitative analysis on the product. Specific reaction conditions and results are shown in Table 1.

[0088] Table 1

[0089]

[0090] From the above results, it can be concluded that the catalyst of the present invention can achieve full conversion of cellulose in a water solvent system by only providing an initial hydrogen source, achieving a 100% cellulose conversion rate and a 75% ethylene glycol monomer yield. However, the cellulose conversion rate of the comparative example cannot reach 100%, and the ethylene glycol yield is less than 50%.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A tungsten oxide supported carbon coated nickel catalyst, characterized in that: The invention comprises a carrier and an active component loaded on the carrier, wherein the carrier is tungsten oxide containing both positive pentavalent tungsten ions and positive hexavalent tungsten ions, and the active component is nickel coated with a carbon layer.

2. The tungsten oxide-supported carbon-coated nickel catalyst according to claim 1, characterized in that: The content of nickel is 10-40wt%, the content of the carbon layer is 10-30wt%, and the balance is tungsten oxide.

3. The tungsten oxide-supported carbon-coated nickel catalyst according to claim 2, characterized in that: The nickel content is 30 wt%.

4. The method for preparing a tungsten oxide-supported carbon-coated nickel catalyst according to claim 1, 2 or 3, characterized in that: The following steps are involved: (1) Preparation of active component carbon layer coated nickel The nickel precursor salt and citric acid are added to an ethanol aqueous solution, heated and stirred to form a gel, then dried, and then calcined at ℃ under a nitrogen atmosphere, and finally acid-washed, water-washed and dried to obtain a carbon layer-coated nickel; (2) Preparation of carrier tungsten oxide Tungsten hexachloride is added to ethanol, mixed evenly, then heated, filtered, washed and freeze-dried to obtain tungsten oxide containing both positive pentavalent tungsten ions and positive hexavalent tungsten ions; (3) Preparation of Catalyst Tungsten oxide and carbon layer coated nickel are added into ethanol, and then subjected to heating, stirring, drying and reduction activation treatment to obtain the tungsten oxide supported carbon coated nickel catalyst.

5. The method for preparing the tungsten oxide supported carbon coated nickel catalyst according to claim 4, characterized in that: In step (1), the molar ratio of the nickel precursor salt to citric acid is 1:1; the volume ratio of ethanol to water in the ethanol aqueous solution is 1:1; the temperature of the heating and stirring treatment is 70°C; the temperature of the drying treatment is 105°C; the specific process of the calcination treatment is: heating to 600°C at a heating rate of 2°C / min under a nitrogen atmosphere, and then calcining at this temperature for 3 hours.

6. The method for preparing the tungsten oxide supported carbon coated nickel catalyst according to claim 4, characterized in that: In step (2), the mass volume ratio of tungsten hexachloride to ethanol is 3g:100mL; the temperature of the heating treatment is 160°C and the time is 36h; the temperature of the freeze-drying treatment is -48°C and the time is 7h.

7. The method for preparing the tungsten oxide supported carbon coated nickel catalyst according to claim 4, characterized in that: In step (3), the temperature of the heating and stirring treatment is 60-90°C, and the time is 5 hours; the temperature of the drying treatment is 105°C, and the time is 4 hours; the gas flow of the reduction activation treatment is 100 mL / min of 10% H2 / 90% N2 gas flow, the temperature is 300°C, and the time is 3 hours.

8. Use of the tungsten oxide-supported carbon-coated nickel catalyst as claimed in claim 1, 2 or 3 in catalytic conversion of cellulose to produce ethylene glycol.

9. A method for preparing ethylene glycol by catalytic conversion of cellulose, characterized in that: The method comprises the following steps: putting cellulose, water and the catalyst as claimed in claim 1, 2 or 3 into a reactor, filling with hydrogen and then conducting a sealed reaction.

10. The method for preparing ethylene glycol by catalytic conversion of cellulose according to claim 9, characterized in that: The amount of hydrogen charged is 2-5 MPa, and the reaction conditions are temperature 220-250°C and time 2-5 hours.

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