A tungsten oxide supported carbon-coated nickel catalyst, a preparation method and application thereof

Abstract

This invention discloses a tungsten oxide-supported carbon-coated nickel catalyst, its preparation method, and its application. The catalyst includes a support and an active component supported on the support. The support is tungsten oxide containing both pentavalent and hexavalent tungsten ions, and the active component is nickel coated with a carbon layer. This catalyst can be applied to the catalytic conversion of cellulose to ethylene glycol. In an aqueous solvent, only an initial hydrogen atmosphere is required to achieve 100% conversion of cellulose, with an ethylene glycol monomer yield reaching 75%. This completes 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, showing broad prospects for industrial application.

Description

Technical Field

[0001] This invention relates to the field of biomass conversion catalyst technology, and in particular to a tungsten oxide-supported carbon-coated nickel catalyst, its preparation method, and its application. Background Technology

[0002] Biomass is a renewable carbon-neutral resource that can be used to produce liquid fuels and chemicals. Among them, lignocellulose, composed of cellulose, hemicellulose, and lignin, is an inedible biomass compared to lignin and hemicellulose. It is one of the most promising sustainable carbon resources, and its composition of glucose units makes it a promising feedstock for the production of platform chemicals.

[0003] Ethylene glycol is the simplest polyol, with a small relative molecular mass and highly reactive properties. It can undergo esterification, etherification, oxidation, and acetalization reactions, making it a crucial basic organic chemical raw material. Currently, global annual consumption of ethylene glycol exceeds 30 million tons, with my country, as a major producer and consumer, consuming over 20 million tons annually. However, traditional ethylene glycol production primarily relies on petroleum-based ethylene or coal as raw materials, which suffers from drawbacks such as non-renewable raw materials, high carbon dioxide emissions, and high energy consumption. Therefore, developing green production technologies using cellulose as a raw material is of great significance for achieving sustainable development.

[0004] Although catalysts play a crucial role in various reactions, exhibiting high activity and selectivity, their stability and the difficulty in separating and recovering them from the reaction mixture after catalytic reaction limit their industrial application. Developing and designing stable and efficient catalysts is key to the efficient conversion of cellulose, either wholly or directly, into valuable chemicals and target fuels. Summary of the Invention

[0005] The main objective of this invention is to provide a tungsten oxide-supported carbon-coated nickel catalyst with excellent catalytic activity and selectivity for the catalytic conversion of cellulose to ethylene glycol, as well as its preparation method and application.

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

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

[0008] Furthermore, the nickel content 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 nickel with carbon layer coating of active component

[0011] Nickel precursor salt and citric acid were added to an ethanol aqueous solution, heated and stirred until a gel was formed, then dried, and then calcined under a nitrogen atmosphere at ℃. Finally, after acid washing, water washing and drying, carbon-coated nickel was obtained.

[0012] (2) Preparation of tungsten oxide carrier

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

[0014] (3) Preparation of catalyst

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

[0016] Further, in step (1), the molar ratio of 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 heating and stirring temperature is 70℃; the drying temperature is 105℃; the specific process of calcination is as follows: the temperature is raised to 600℃ at a heating rate of 2℃ / min under a nitrogen atmosphere, and then calcined at this temperature for 3h.

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

[0018] Further, in step (3), the heating and stirring treatment is carried out at a temperature of 60-90℃ for 5 hours; the drying treatment is carried out at a temperature of 105℃ for 4 hours; the reduction and activation treatment is carried out at a gas flow rate of 100 mL / min of 10% H2 / 90% N2, at a temperature of 300℃ for 3 hours.

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

[0020] The present invention also provides a method for catalytic conversion of cellulose to prepare ethylene glycol, comprising the following steps: adding cellulose, water and the above-mentioned catalyst into a reactor, filling it with hydrogen gas and then carrying out a sealed reaction.

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

[0022] The catalyst of this invention uses tungsten oxide as a support and nickel encapsulated in a carbon shell as the active component, which enhances the catalyst's ability to hydrogenate cellulose. The tungsten oxide, containing both pentavalent and hexavalent tungsten ions, has abundant acidic sites on its surface and inside, a large surface area, and strong adsorption capacity, which can fully disperse the active component and effectively achieve the cleavage of the C-C bonds in cellulose by tungsten oxide. Nickel metal and the nickel encapsulated in the carbon shell have unique electronic structures, exhibiting excellent hydrogenation capacity during cellulose conversion. The carbon shell encapsulation of nickel metal not only improves the catalyst's hydrogenation capacity but also significantly enhances its stability, greatly reducing the sintering and loss of metallic nickel during the reaction. Therefore, the catalyst of this invention achieves a high ethylene glycol yield from cellulose.

[0023] The beneficial effects of this invention are reflected in:

[0024] The catalyst of this invention can be applied to the catalytic conversion of cellulose to 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%. This completes 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. Attached Figure Description

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

[0026] Figure 2 The image shows the XRD pattern of 1#Ni@C obtained in Example 1.

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

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

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

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

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

[0032] Figure 8 The image shows the TG and DTG diagrams of 1#Ni@C obtained in Example 1.

[0033] Figure 9 The images show the TG and DTG values ​​of catalyst #5 prepared in Example 5.

[0034] Figure 10 WO2# prepared in Example 2 x XPS graph.

[0035] Figure 11 XPS images of catalysts #3 to #6 prepared in Examples 3 to 6. Detailed Implementation

[0036] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

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

[0038] Example 1

[0039] Preparation of nickel coated with carbon layer as active component

[0040] The specific preparation method is as follows:

[0041] 8.7237 g Ni(NO3)2·6H2O and 5.76 g citric acid were added to an ethanol-water solution consisting of 5 mL deionized water and 5 mL ethanol. The solution was stirred and dissolved to form a homogeneous solution. The solution was then stirred at 70 °C and 250 r / min until a gel was formed. The gel was then dried at 105 °C for 72 h and ground into a solid powder. The solid powder was placed in a tube furnace and calcined at 600 °C for 3 h under a nitrogen atmosphere at a heating rate of 2 °C / min. After naturally cooling to room temperature, the powder was placed in a 1 mol / L sulfuric acid solution and stirred at 500 r / min for 12 h. Finally, the powder was washed with deionized water until neutral and dried at 105 °C for 12 h to obtain a carbon-coated nickel, denoted as Ni@C and numbered 1#. ICP (inductively coupled plasma) analysis showed that the nickel content was 69.00 wt%, with the remainder being a carbon layer.

[0042] Example 2

[0043] Preparation of tungsten oxide on support

[0044] The specific preparation method is as follows:

[0045] 3g of tungsten hexachloride was added to 100mL of ethanol and sonicated for 10min. Then, it was transferred to a hydrothermal synthesis reactor and treated at 160℃ for 36h. After filtration, the filter cake was washed with deionized water and dried at -48℃ for 7h to obtain tungsten oxide containing both pentavalent and hexavalent tungsten ions, denoted as WO₃. x The number is 2#.

[0046] Example 3

[0047] Preparation of tungsten oxide supported carbon-coated nickel catalyst

[0048] The specific preparation method is as follows:

[0049] 0.145g of Ni@C prepared in Example 1 and 1g of WO3 prepared in Example 2 were used. x The catalyst was added to 60 mL of ethanol and stirred for 5 h at 300 r / min and 60 °C. It was then dried at 105 °C for 4 h, and finally reduced and activated for 3 h at 300 °C with a 100 mL / min stream of 10% H₂ / 90% N₂. This yielded a tungsten oxide-supported carbon-coated nickel catalyst with a nickel content of 10 wt%, denoted as 10Ni@C / WO₃. x The sample, numbered 3#, had a nickel content of 10.36 wt% 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] 0.290g of Ni@C prepared in Example 1 and 1g of WO2 prepared in Example 2 were used. x The catalyst was added to 60 mL of ethanol and stirred for 5 h at 300 r / min and 70 °C. It was then dried at 105 °C for 4 h, and finally reduced and activated for 3 h at 300 °C with a 100 mL / min stream of 10% H₂ / 90% N₂. This yielded a tungsten oxide-supported carbon-coated nickel catalyst with a nickel content of 20 wt%, denoted as 20Ni@C / WO₃. x The sample, numbered 4#, had a nickel content of 20.09 wt% 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] 0.435g of Ni@C prepared in Example 1 and 1g of WO2 prepared in Example 2 were used. x The catalyst was added to 60 mL of ethanol and stirred for 5 h at 300 r / min and 80 °C. It was then dried at 105 °C for 4 h, and finally reduced and activated for 3 h at 300 °C with a 10% H₂ / 90% N₂ gas flow rate of 100 mL / min. This yielded a tungsten oxide-supported carbon-coated nickel catalyst with a nickel content of 30 wt%, denoted as 30Ni@C / WO₃. x The sample, numbered 5#, has a nickel content of 30.74 wt% 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] 0.58g of Ni@C prepared in Example 1 and 1g of WO3 prepared in Example 2 were used. x The catalyst was added to 60 mL of ethanol and stirred for 5 h at 300 r / min and 90 °C. It was then dried at 105 °C for 4 h, and finally reduced and activated for 3 h at 300 °C with a 10% H₂ / 90% N₂ gas flow rate of 100 mL / min. This yielded a tungsten oxide-supported carbon-coated nickel catalyst with a nickel content of 40 wt%, denoted as 40Ni@C / WO₃. x The sample, numbered 6#, had a nickel content of 38.86 wt% according to ICP analysis.

[0062] Comparative Example 1

[0063] Preparation of comparative catalysts

[0064] This comparative example prepared the catalyst according to the same method as in Example 3, except that 0.145g Ni@C was replaced with 0.4955g Ni(NO3)2·6H2O, ultimately obtaining WO3 with a nickel content of 10wt%. 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 according to the same method as in Example 4, except that 0.145 g Ni@C was replaced with 0.9910 g Ni(NO3)2·6H2O, ultimately obtaining WO3 with a nickel content of 20 wt%. x Supported nickel catalyst, denoted as 20Ni / WO x The number is 2&.

[0068] Comparative Example 3

[0069] Preparation of comparative catalysts

[0070] This comparative example prepared the catalyst according to the same method as in Example 5, except that 0.145g Ni@C was replaced with 1.4865g Ni(NO3)2·6H2O, ultimately obtaining WO3 with a nickel content of 30wt%. x Supported nickel catalyst, denoted as 30Ni / WO x The number is 3&.

[0071] Comparative Example 4

[0072] Preparation of comparative catalysts

[0073] This comparative example prepared the catalyst according to the same method as in Example 6, except that 0.145 g Ni@C was replaced with 1.9820 g Ni(NO3)2·6H2O, ultimately obtaining WO3 with a nickel content of 40 wt%. x Supported nickel catalyst, denoted as 40Ni / WO x The number is 4&.

[0074] Comparative Example 5

[0075] Preparation of comparative catalysts

[0076] This comparative example prepared the catalyst according to the same method as in Example 5, the only difference being 1g WO x The catalyst was replaced with 1g WO3, and the final catalyst was denoted as 30Ni@C / WO3 and numbered 5&.

[0077] Experimental Example 1

[0078] Structural determination of tungsten oxide supported carbon-coated nickel catalyst

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

[0080] See Figure 1 and Figure 2 The TEM image of Ni@C shows a distinct carbon layer surrounding the metallic nickel, and no nickel oxide peaks were found in its XRD pattern, both indicating the successful preparation of nickel coated with a carbon layer.

[0081] See Figure 3 In the XRD patterns of the support and catalyst, corresponding WO3 was detected at 2θ = 23.6°, 34.2°, and 55.8°.x The characteristic diffraction peaks of WO prove that x Successful preparation of the support; in the XRD pattern 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 onto the support, and the low peak intensity indicates good metal dispersion.

[0082] See 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 the various embodiments of the present invention have type IV isotherms, and their hysteresis loops all belong to type H3, indicating that the catalysts are all mesoporous ordered channels.

[0083] See Figure 8 and 9 It can be seen that the weight loss processes of the precursor Ni@C and the catalyst 30Ni@C / WOx are similar. The loss at 180℃ may be due to moisture loss; the increasing curve from 180-300℃ may be due to the oxidation of metallic nickel to form metal oxides, leading to an increase in weight. This also indicates that the citric acid pyrolysis process promotes metal reduction, and further demonstrates the significant reduction effect of the catalyst.

[0084] See Figure 10 W of the carrier WOx 5+ W 6+ Similar proportions, see also Figure 11 After loading the active component, W 5+ The content increased significantly, and the double peaks at 38.7 eV and 36.6 eV were attributed to W. 6+ 4f 5 / 2 and 4f 7 / 2 The double peaks at 37.9 eV and 35.7 eV correspond to W, respectively. 5+ 4f 5 / 2 and 4f 7 / 2 The increase in Ni content leads to W 5+ The proportion is higher, but when the Ni content increases from 30% to 40%, W 5+ The content decreased slightly, which is consistent with the trend of catalytic results.

[0085] Example 2

[0086] Performance Testing of Tungsten Oxide-Supported Carbon-Coated Nickel Catalyst for the 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, pressurize with an initial hydrogen pressure of 2-5MPa, and then seal and react at 220-250℃ and a stirring rate of 500r / min for 2-5h. Afterward, filter the reaction product to obtain the liquid phase product, and finally perform quantitative analysis on the product. The specific reaction conditions and results are shown in Table 1.

[0088] Table 1

[0089]

[0090] The results above show that the catalyst of this invention, in an aqueous solvent system, only requires an initial hydrogen source to achieve complete cellulose conversion, achieving a 100% cellulose conversion rate and a 75% ethylene glycol monomer yield. In contrast, the comparative cellulose conversion rate 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 principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tungsten oxide-supported carbon-coated nickel catalyst for the catalytic conversion of cellulose to ethylene glycol, characterized in that, It includes a support and an active component loaded on the support, wherein the support is tungsten oxide containing both pentavalent and hexavalent tungsten ions, and the active component is nickel coated with a carbon layer; The preparation method of the tungsten oxide-supported carbon-coated nickel catalyst includes the following steps: (1) Preparation of nickel coated with carbon layer of active component Nickel precursor salt and citric acid were added to an ethanol aqueous solution, heated and stirred until a gel was formed, then dried, and then calcined under a nitrogen atmosphere at ℃. Finally, after acid washing, water washing and drying, carbon-coated nickel was obtained. (2) Preparation of tungsten oxide carrier Tungsten hexachloride was added to ethanol, mixed evenly, then heated, and finally filtered, washed and freeze-dried to obtain tungsten oxide containing both pentavalent and hexavalent tungsten ions. (3) Preparation of catalyst Tungsten oxide and carbon-coated nickel were added to ethanol, and then subjected to heating, stirring, drying and reduction activation treatment to obtain the tungsten oxide-supported carbon-coated nickel catalyst.

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

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

4. The tungsten oxide-supported carbon-coated nickel catalyst as described in claim 1, characterized in that, In step (1), the molar ratio of 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 heating and stirring temperature is 70℃; the drying temperature is 105℃; the specific process of calcination is as follows: the temperature is raised to 600℃ at a heating rate of 2℃ / min under a nitrogen atmosphere, and then calcined at this temperature for 3 hours.

5. The tungsten oxide-supported carbon-coated nickel catalyst as described in claim 1, characterized in that, In step (2), the mass-to-volume ratio of tungsten hexachloride to ethanol is 3g:100mL; the heating temperature is 160℃ and the time is 36h; the freeze-drying temperature is -48℃ and the time is 7h.

6. The tungsten oxide-supported carbon-coated nickel catalyst as described in claim 1, characterized in that, In step (3), the heating and stirring treatment is carried out at a temperature of 60-90℃ for 5 hours; the drying treatment is carried out at a temperature of 105℃ for 4 hours; the reduction and activation treatment is carried out at a gas flow rate of 100 mL / min of 10% H2 / 90% N2, at a temperature of 300℃ for 3 hours.

7. The application of the tungsten oxide-supported carbon-coated nickel catalyst as described in any one of claims 1 to 6 in the catalytic conversion of cellulose to ethylene glycol.

8. A method for catalytic conversion of cellulose to prepare ethylene glycol, characterized in that, The process includes the following steps: adding cellulose, water, and the catalyst as described in any one of claims 1 to 6 into a reactor, purging with hydrogen, and then conducting a sealed reaction.

9. The method for catalytic conversion of cellulose to ethylene glycol as described in claim 8, characterized in that, The hydrogen charge is 2-5 MPa, and the reaction conditions are 220-250℃ and 2-5 h.

Images