Preparation method of NiCo / MCM-41 catalyst for conversion of lignin derivatives

Abstract

The application discloses a kind of preparation and application of NiCo / MCM-41 catalyst, with metal Ni as main metal, doped non-precious metal Co, using impregnation method to obtain MCM-41 molecular sieve supported bimetallic catalyst, compared with other catalysts, with more abundant pore structure and larger specific surface area, the Ni-Co structure formed can effectively promote the dispersion of metal particles, improve the hydrogenation activity of catalyst.In the optimal proportion catalyst of Ni / Co molar ratio 4:1, the catalyst material shows excellent catalytic performance in lignin derivative hydrogenation conversion reaction, under the same reaction conditions, the introduction of suitable acid greatly improves the reaction performance, saves the consumption of energy, and thus has potential application value for lignin derivative hydrogenation conversion to produce high-value chemicals.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy chemical industry, and particularly relates to the preparation of a NiCo / MCM-41 catalyst and its application in the hydrogenation conversion of lignin derivatives to produce high-value-added chemicals. Background Art

[0002] The dramatic increase in fossil fuel consumption, severe environmental pollution, and the emission of harmful gases have led to the increasing greenhouse effect and global warming. Furthermore, fossil fuels are non-renewable resources, and with the increasing demand for fuels in society, they will eventually be depleted. Therefore, renewable resources hold great promise as new energy sources and for the production of chemicals. Biomass offers valuable research opportunities in the production of renewable fuels and chemicals, particularly liquid fuels.

[0003] Lignin is a three-dimensional amorphous polymer composed of various methylphenylpropane structural units. It is rich in aromatic units and can be used as a potential raw material for the production of aromatic compounds. However, the complexity of lignin's chemical structure makes its chemical conversion extremely difficult. Its high carbon content easily leads to carbon accumulation on the surface of acidic catalysts, which in turn deactivates the catalyst. Furthermore, small lignin depolymerization products are highly susceptible to recombination reactions. Furthermore, universally applicable catalysts have not yet been developed, so lignin derivatives are generally selected for research.

[0004] Hydrogenation is one of the most popular strategies for converting lignin and its derivatives into high-value-added chemicals. However, the hydroconversion process has high requirements for reaction conditions, so catalysts are very important for hydroconversion. Common precious metal catalysts such as Pd, Pt, and Ru have been widely studied in the catalytic conversion of lignin and its derivatives. They have good hydroconversion activity, especially high selectivity for saturated alkanes (such as cyclohexane). However, their high price and limited resources limit their large-scale application in industrial production. Relatively speaking, Ni-based materials have catalytic activity similar to that of precious metal catalysts in the catalytic conversion process and are low in price. At the same time, they can effectively avoid the problem of excessive hydrogenation of benzene rings. In addition, as a carrier, MCM-41 molecular sieve is undoubtedly a good choice. MCM-41 molecular sieve has a uniform pore size, a high specific surface area and adsorption capacity, which is conducive to the diffusion of organic molecules, making it an excellent catalyst carrier. Zeng et al. (Chemical Engineering Journal, 2017, 320:55-62) studied the catalytic performance of Ru / MCM-41 for phenol. They showed that MCM-41 has advantages such as high specific surface area and ordered mesoporous structure, which can promote catalytic contact and mass transfer. The phenol conversion rate reached 73.9% and the deoxygenation degree was 72.2%.

[0005] CN112264084A discloses an MCM-41 / Pd / Ni catalyst, its preparation method, and application. MCM-41 is used as a carrier to load metal palladium and nickel. The MCM-41-loaded palladium-nickel bimetallic catalyst can improve the catalytic activity of the catalyst and can be repeatedly recycled. However, the catalyst involves the use of precious metals, which is too expensive and not suitable for large-scale use.

[0006] CN108452822A discloses a microwave-assisted catalyst and catalytic process for preparing higher olefins using MCM-41 as a carrier. The method uses a nickel-molybdenum composite catalyst supported by MCM-41 and methane as a starting material to produce higher olefins. This method has the characteristics of high isooctene selectivity, environmental friendliness, energy conservation, and low cost. However, the equipment used is expensive, the operation is cumbersome, and there is a risk of uneven heating during heating, and excessive heating can lead to "thermal runaway." Summary of the Invention

[0007] Against this background, the present invention aims to construct a cost-effective, stable, and highly catalytically active NiCo / MCM-41 catalyst. In the hydrogenation conversion of lignin derivatives, the incorporation of bimetallic compounds can effectively promote the dispersion of the metals, exposing more active sites and thereby improving the catalytic performance of the catalyst. The introduction of suitable acidic sites greatly enhances the reaction effect and effectively reduces the reaction conditions. To achieve the above objectives, the present invention employs the following technical solutions:

[0008] The method for preparing the NiCo / MCM-41 catalyst for hydrogenation of lignin derivatives according to the present invention specifically comprises the following steps:

[0009] (1) Sodium silicate, sodium metaaluminate, hexadecyltrimethylammonium bromide and deionized water were weighed in a certain molar ratio and dissolved in deionized water, stirred evenly to form a mixed solution, and then sulfuric acid was slowly added dropwise to the mixed solution and continued to stir at room temperature for a certain period of time;

[0010] (2) placing the mixed solution stirred in step (1) into a hydrothermal kettle, taking it out after hydrothermal treatment for a certain period of time, washing, filtering, drying, and finally calcining to obtain the molecular sieve carrier MCM-41;

[0011] (3) dissolving a certain amount of nickel salt and cobalt salt in a molar ratio in deionized water, ultrasonicating until completely dissolved, and adding dropwise to the molecular sieve support MCM-41 in step (2), standing, drying, and calcining to obtain a catalyst precursor;

[0012] (4) In a hydrogen atmosphere, the catalyst precursor prepared in (3) was calcined and reduced to obtain a NiCo / MCM-41 catalyst.

[0013] Furthermore, in step (1), the molar ratio of sodium silicate, sodium metaaluminate, hexadecyltrimethylammonium bromide and deionized water is 1:0.0063-0.0125:0.2:100, and the concentration of sulfuric acid is 1 mol / L.

[0014] Furthermore, in step (2), the sample hydrothermal temperature is 110° C., the hydrothermal time is 48 h, the roasting temperature is 550° C., and the roasting time is 4 h.

[0015] Furthermore, the nickel salt in step (3) is one of nickel nitrate, nickel acetate, nickel sulfate, and nickel chloride, the cobalt salt is one of cobalt nitrate, cobalt sulfate, and cobalt chloride, the nickel salt and the cobalt salt are mixed in a molar ratio of 2:1 to 8:1, and the catalyst precursor is calcined at a temperature of 550°C and a calcination time of 4 hours.

[0016] Furthermore, the reduction condition in step (4) is calcined at 550° C. for 4 h at a heating rate of 2-5° C. / min, wherein the hydrogen gas flow rate is 40-100 ml / min, to obtain a NiCo / MCM-41 catalyst.

[0017] The NiCo / MCM-41 catalyst prepared by the above method is applied to the hydrogenation conversion reaction of lignin derivatives: the lignin derivative vanillin, the NiCo / MCM-41 catalyst and the reaction solvent are mixed and placed in a high-pressure batch reactor, the air in the reaction device is purged with N2, and then high-purity hydrogen is filled to react; after the reaction is completed, the reaction product is filtered, and the obtained liquid product is added with an internal standard for GC analysis to calculate the conversion rate and monomer selectivity; the reaction solvent is 60 ml, and methanol is selected as the solvent; the liquid product is a phenolic compound; the operating conditions of the reaction process are: reaction temperature of 120-200°C, reaction pressure of 1-2 MPa, reaction time of 2 h, stirring rate of 400-700 r / min, and the catalyst amount is 20 wt.% of the lignin derivative vanillin.

[0018] The gas was tested to contain no product, so only the liquid product was calculated. The liquid product conversion rate and monomer selectivity were calculated as follows:

[0019]

[0020]

[0021] Y: Vanillin conversion rate, n product : The molar amount of the product after the reaction, n befer : molar amount of vanillin before reaction, S: selectivity of product after reaction, n all product : The total molar amount of all products after the reaction.

[0022] The present application has the following advantages and beneficial effects

[0023] (1) The present application successfully synthesizes the molecular sieve MCM-41 carrier, and the carrier material with large specific surface area and pore structure effectively solves the mass transfer-diffusion limitation problem of the lignin derivative vanillin, and improves the lignin derivative vanillin hydrogenation conversion efficiency.

[0024] (2) The molecular sieve nickel-cobalt bimetallic catalyst provided by the present application is simple and economical in process, and the Ni-Co coupling structure in the catalyst promotes the high dispersion of metal particles, and significantly improves the catalytic activity.

[0025] (3) The molecular sieve nickel-cobalt bimetallic catalyst provided by the present application introduces appropriate acidity, which greatly improves the conversion rate of raw materials and the selectivity of target products under the same reaction conditions, so that the reaction can obtain higher conversion rate and selectivity under mild conditions, and effectively reduces the energy consumption. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is the XRD spectrum of the catalyst.

[0027] Figure 2 is the TEM spectrum of the catalyst. DETAILED DESCRIPTION

[0028] The present application will be further described in detail below in combination with examples and drawings, but the embodiments of the present application are not limited thereto.

[0029] The other reagents used in the examples can be commercially available unless otherwise specified.

[0030] Comparative example

[0031] Sodium silicate, hexadecyltrimethylammonium bromide, and deionized water in a molar ratio of 1:0.2:100 were dissolved in deionized water and stirred to form a mixed solution. 1 mol / L sulfuric acid was then slowly added dropwise to the mixed solution and stirred at room temperature for 2 hours. The mixed solution was then transferred to a hydrothermal reactor and maintained at 110°C for 48 hours. After the hydrothermal reaction, the solution mixture was removed, washed, dried in an 80°C oven for 24 hours, ground, and transferred to a muffle furnace for calcination at 550°C for 4 hours to obtain the molecular sieve support MCM-41. 0.8743 g of nickel nitrate hexahydrate was weighed and dissolved in 2 ml of deionized water. Once completely dissolved, it was added dropwise to 1 g of the prepared molecular sieve support MCM-41 and stirred to obtain a uniform solution. After being placed at room temperature overnight, it was dried in an oven at 80°C for 12 hours, and after grinding, it was moved into a muffle furnace and calcined at 550°C for 4 hours to obtain a catalyst precursor. The catalyst precursor was placed in a tubular furnace and reduced at 550°C in a H2 atmosphere for 4 hours to obtain a molecular sieve catalyst Ni / MCM-41, in which the mass percentage of Ni was 15wt.%.

[0032] 0.1g of Ni / MCM-41 catalyst, 0.5g of vanillin, and 60ml of methanol solvent were added to an autoclave. The air in the reactor was purged with N2, and then filled with 2.5MPa of high-purity hydrogen. The reaction temperature was 140°C, the stirring rate was set at 700 rpm, and the reaction time was 2h. After the reaction was completed, the reaction product was removed after cooling to room temperature, filtered, and the liquid product was qualitatively and quantitatively analyzed after adding an internal standard.

[0033] The results of the vanillin hydrogenation reaction are shown in Table 1.

[0034] Example 1

[0035] Sodium silicate, hexadecyltrimethylammonium bromide, and deionized water in a molar ratio of 1:0.2:100 were dissolved in deionized water and stirred to form a mixed solution. 1 mol / L sulfuric acid was then slowly added dropwise to the mixed solution and stirred at room temperature for 2 hours. The mixed solution was then transferred to a hydrothermal reactor and maintained at 110°C for 48 hours. After the hydrothermal reaction, the solution mixture was removed, washed, dried in an 80°C oven for 24 hours, ground, and transferred to a muffle furnace for calcination at 550°C for 4 hours to obtain the molecular sieve support MCM-41. 0.8743 g of nickel nitrate hexahydrate and 0.1094 g of cobalt nitrate hexahydrate were weighed and dissolved in 2 ml of deionized water. After complete dissolution, they were added dropwise to 1 g of the prepared support and stirred to obtain a uniform solution. After being placed at room temperature overnight, the product was dried in an oven at 80°C for 12 hours, ground and moved into a muffle furnace, and calcined at 550°C for 4 hours to obtain a catalyst precursor. The catalyst precursor was placed in a tubular furnace and reduced at 550°C in a H2 atmosphere for 4 hours to obtain a molecular sieve catalyst 8NiCo / MCM-41, in which the mass percentage of Ni is 15 wt.%, and the molar ratio of Ni to Co is 8:1.

[0036] 0.1g of 8NiCo / MCM-41 catalyst, 0.5g of vanillin, and 60ml of methanol solvent were added to an autoclave. The air in the reactor was purged with nitrogen and then filled with 2.5MPa of high-purity hydrogen. The reaction temperature was 140°C, the stirring rate was set at 700 rpm, and the reaction time was 2h. After the reaction was completed, the reaction product was removed after cooling to room temperature, filtered, and the liquid product was qualitatively and quantitatively analyzed after adding an internal standard.

[0037] The results of the vanillin hydrogenation reaction are shown in Table 1.

[0038] Example 2

[0039] Sodium silicate, hexadecyltrimethylammonium bromide, and deionized water in a molar ratio of 1:0.2:100 were dissolved in deionized water and stirred to form a mixed solution. 1 mol / L sulfuric acid was then slowly added dropwise to the mixed solution and stirred at room temperature for 2 hours. The mixed solution was then transferred to a hydrothermal reactor and maintained at 110°C for 48 hours. After the hydrothermal reaction, the solution mixture was removed, washed, dried in an 80°C oven for 24 hours, ground, and transferred to a muffle furnace for calcination at 550°C for 4 hours to obtain the molecular sieve support MCM-41. 0.8743 g of nickel nitrate hexahydrate and 0.1459 g of cobalt nitrate hexahydrate were weighed and dissolved in 2 ml of deionized water. After complete dissolution, they were added dropwise to 1 g of the prepared support and stirred to obtain a uniform solution. After being placed at room temperature overnight, the product was dried in an oven at 80°C for 12 hours, ground and moved into a muffle furnace, and calcined at 550°C for 4 hours to obtain a catalyst precursor. The catalyst precursor was placed in a tubular furnace and reduced at 550°C in a H2 atmosphere for 4 hours to obtain a molecular sieve catalyst 6NiCo / MCM-41, in which the mass percentage of Ni is 15 wt.%, and the molar ratio of Ni to Co is 6:1.

[0040] 0.1g of 6NiCo / MCM-41 catalyst, 0.5g of vanillin, and 60ml of methanol solvent were added to an autoclave. The air in the reactor was purged with nitrogen and then filled with 2.5MPa of high-purity hydrogen. The reaction temperature was 140°C, the stirring rate was set at 700 rpm, and the reaction time was 2h. After the reaction was completed, the reaction product was removed after cooling to room temperature, filtered, and the liquid product was qualitatively and quantitatively analyzed after adding an internal standard.

[0041] The results of the vanillin hydrogenation reaction are shown in Table 1.

[0042] Example 3

[0043] Sodium silicate, hexadecyltrimethylammonium bromide, and deionized water in a molar ratio of 1:0.2:100 were dissolved in deionized water and stirred to form a mixed solution. 1 mol / L sulfuric acid was then slowly added dropwise to the mixed solution and stirred at room temperature for 2 hours. The mixed solution was then transferred to a hydrothermal reactor and maintained at 110°C for 48 hours. After the hydrothermal reaction, the solution mixture was removed, washed, dried in an 80°C oven for 24 hours, ground, and transferred to a muffle furnace for calcination at 550°C for 4 hours to obtain the molecular sieve support MCM-41. 0.8743 g of nickel nitrate hexahydrate and 0.2188 g of cobalt nitrate hexahydrate were weighed and dissolved in 2 ml of deionized water. After complete dissolution, they were added dropwise to 1 g of the prepared support and stirred to obtain a uniform solution. After being placed at room temperature overnight, the product was dried in an oven at 80°C for 12 hours, ground and moved into a muffle furnace, and calcined at 550°C for 4 hours to obtain a catalyst precursor. The catalyst precursor was placed in a tubular furnace and reduced at 550°C in a H2 atmosphere for 4 hours to obtain a molecular sieve catalyst 4NiCo / MCM-41, in which the mass percentage of Ni is 15 wt.%, and the molar ratio of Ni to Co is 4:1.

[0044] 0.1g of 4NiCo / MCM-41 catalyst, 0.5g of vanillin, and 60ml of methanol solvent were added to an autoclave. The air in the reactor was purged with nitrogen and then filled with 2.5MPa of high-purity hydrogen. The reaction temperature was 140°C, the stirring rate was set at 700 rpm, and the reaction time was 2h. After the reaction was completed, the reaction product was removed after cooling to room temperature, filtered, and the liquid product was qualitatively and quantitatively analyzed after adding an internal standard.

[0045] The results of the vanillin hydrogenation reaction are shown in Table 1.

[0046] Example 4

[0047] Sodium silicate, hexadecyltrimethylammonium bromide, and deionized water in a molar ratio of 1:0.2:100 were dissolved in deionized water and stirred to form a mixed solution. 1 mol / L sulfuric acid was then slowly added dropwise to the mixed solution and stirred at room temperature for 2 hours. The mixed solution was then transferred to a hydrothermal reactor and maintained at 110°C for 48 hours. After the hydrothermal reaction, the solution mixture was removed, washed, dried in an 80°C oven for 24 hours, ground, and transferred to a muffle furnace for calcination at 550°C for 4 hours to obtain the molecular sieve support MCM-41. 0.8743 g of nickel nitrate hexahydrate and 0.43764 g of cobalt nitrate hexahydrate were weighed and dissolved in 2 ml of deionized water. After complete dissolution, they were added dropwise to 1 g of the prepared support and stirred to obtain a uniform solution. After being placed at room temperature overnight, the product was dried in an oven at 80°C for 12 hours, ground and moved into a muffle furnace, and calcined at 550°C for 4 hours to obtain a catalyst precursor. The catalyst precursor was placed in a tubular furnace and reduced at 550°C in a H2 atmosphere for 4 hours to obtain a molecular sieve catalyst 2NiCo / MCM-41, in which the mass percentage of Ni is 15 wt.%, and the molar ratio of Ni to Co is 2:1.

[0048] 0.1g of 2NiCo / MCM-41 catalyst, 0.5g of vanillin, and 60ml of methanol solvent were added to an autoclave. The air in the reactor was purged with nitrogen and then filled with 2.5MPa of high-purity hydrogen. The reaction temperature was 140°C, the stirring rate was set at 700 rpm, and the reaction time was 2h. After the reaction was completed, the reaction product was removed after cooling to room temperature, filtered, and the liquid product was qualitatively and quantitatively analyzed after adding an internal standard.

[0049] The results of the vanillin hydrogenation reaction are shown in Table 1.

[0050] Example 5

[0051] Sodium silicate, sodium metaaluminate, hexadecyltrimethylammonium bromide, and deionized water in a molar ratio of 1:0.0125:0.2:100 were dissolved in deionized water and stirred to form a mixed solution. 1 mol / L sulfuric acid was then slowly added dropwise to the mixed solution and stirred at room temperature for 2 hours. The mixed solution was then transferred to a hydrothermal reactor and maintained at 110°C for 48 hours. After the hydrothermal reaction, the solution mixture was removed, washed, dried in an 80°C oven for 24 hours, ground, and transferred to a muffle furnace for calcination at 550°C for 4 hours to obtain the molecular sieve carrier MCM-41-40. 0.8743 g of nickel nitrate hexahydrate and 0.2188 g of cobalt nitrate hexahydrate were weighed and dissolved in 2 ml of deionized water. After complete dissolution, they were added dropwise to 1 g of the prepared molecular sieve carrier MCM-41-40 and stirred to obtain a uniform solution. After being placed at room temperature overnight, it was dried in an oven at 80°C for 12 hours, ground and moved into a muffle furnace, and calcined at 550°C for 4 hours to obtain a catalyst precursor. The catalyst precursor was placed in a tubular furnace and reduced at 550°C in a H2 atmosphere for 4 hours to obtain a molecular sieve catalyst 4NiCo / MCM-41-40, in which the mass percentage of Ni is 15 wt.%, the molar ratio of metal Ni to Co is 4:1, and the silicon-aluminum ratio of the molecular sieve carrier MCM-41-40 is 40.

[0052] 0.1g of 4NiCo / MCM-41-40 catalyst, 0.5g of vanillin, and 60ml of methanol solvent were added to an autoclave. The air in the reactor was purged with nitrogen and then filled with 2.5MPa of high-purity hydrogen. The reaction temperature was 140°C, the stirring rate was set at 700 rpm, and the reaction time was 2 hours. After the reaction was completed, the reaction product was removed after cooling to room temperature, filtered, and the liquid product was qualitatively and quantitatively analyzed after adding an internal standard.

[0053] The results of the vanillin hydrogenation reaction are shown in Table 1.

[0054] Example 6

[0055] Sodium silicate, sodium metaaluminate, hexadecyltrimethylammonium bromide, and deionized water in a molar ratio of 1:0.0083:0.2:100 were dissolved in deionized water and stirred to form a mixed solution. 1 mol / L sulfuric acid was then slowly added dropwise to the mixed solution and stirred at room temperature for 2 hours. The mixed solution was then transferred to a hydrothermal reactor and maintained at 110°C for 48 hours. After the hydrothermal reaction, the solution mixture was removed, washed, dried in an 80°C oven for 24 hours, ground, and transferred to a muffle furnace for calcination at 550°C for 4 hours to obtain the molecular sieve carrier MCM-41-60. 0.8743 g of nickel nitrate hexahydrate and 0.2188 g of cobalt nitrate hexahydrate were weighed and dissolved in 2 ml of deionized water. After complete dissolution, they were added dropwise to 1 g of the prepared molecular sieve carrier MCM-41-60 and stirred to obtain a uniform solution. After being placed at room temperature overnight, it was dried in an oven at 80°C for 12 hours, ground and moved into a muffle furnace, and calcined at 550°C for 4 hours to obtain a catalyst precursor. The catalyst precursor was placed in a tubular furnace and reduced at 550°C in a H2 atmosphere for 4 hours to obtain a molecular sieve catalyst 4NiCo / MCM-41-60, in which the mass percentage of Ni is 15wt.%, the molar ratio of metal Ni to Co is 4:1, and the silicon-aluminum ratio of the molecular sieve carrier MCM-41-60 is 60.

[0056] 0.1g of 4NiCo / MCM-41-60 catalyst, 0.5g of vanillin, and 60ml of methanol solvent were added to an autoclave. The air in the reactor was purged with nitrogen and then filled with 2.5MPa of high-purity hydrogen. The reaction temperature was 140°C, the stirring rate was set at 700 rpm, and the reaction time was 2 hours. After the reaction was completed, the reaction product was removed after cooling to room temperature, filtered, and the liquid product was qualitatively and quantitatively analyzed after adding an internal standard.

[0057] The results of the vanillin hydrogenation reaction are shown in Table 1.

[0058] Example 7

[0059] Sodium silicate, sodium metaaluminate, hexadecyltrimethylammonium bromide, and deionized water in a molar ratio of 1:0.0063:0.2:100 were dissolved in deionized water and stirred to form a mixed solution. 1 mol / L sulfuric acid was then slowly added dropwise to the mixed solution and stirred at room temperature for 2 hours. The mixed solution was then transferred to a hydrothermal reactor and maintained at 110°C for 48 hours. After the hydrothermal reaction, the solution mixture was removed, washed, dried in an 80°C oven for 24 hours, ground, and transferred to a muffle furnace for calcination at 550°C for 4 hours to obtain the molecular sieve carrier MCM-41-80. 0.8743 g of nickel nitrate hexahydrate and 0.2188 g of cobalt nitrate hexahydrate were weighed and dissolved in 2 ml of deionized water. After complete dissolution, they were added dropwise to 1 g of the prepared molecular sieve carrier MCM-41-80 and stirred to obtain a uniform solution. After being placed at room temperature overnight, it was dried in an oven at 80°C for 12 hours, ground and moved into a muffle furnace, and calcined at 550°C for 4 hours to obtain a catalyst precursor. The catalyst precursor was placed in a tubular furnace and reduced at 550°C in a H2 atmosphere for 4 hours to obtain a molecular sieve catalyst 4NiCo / MCM-41-80, in which the mass percentage of Ni is 15wt.%, the molar ratio of metal Ni to Co is 4:1, and the silicon-aluminum ratio of the molecular sieve carrier MCM-41-80 is 80.

[0060] 0.1g of 4NiCo / MCM-41-80 catalyst, 0.5g of vanillin, and 60ml of methanol solvent were added to an autoclave. The air in the reactor was purged with nitrogen and then filled with 2.5MPa of high-purity hydrogen. The reaction temperature was 140°C, the stirring rate was set at 700 rpm, and the reaction time was 2 hours. After the reaction was completed, the reaction product was removed after cooling to room temperature, filtered, and the liquid product was qualitatively and quantitatively analyzed after adding an internal standard.

[0061] The results of the vanillin hydrogenation reaction are shown in Table 1.

[0062] The yields of the reaction products obtained in the above comparative examples and examples are shown in Table 1.

[0063] Table 1 Evaluation results of vanillin hydrogenolysis reaction

[0064]

[0065] Note: Conv. (%) represents conversion rate, Select. (%) represents product selectivity.

[0066] As can be seen from Table 1, compared with the comparative example (Ni / MCM-41), the conversion rate of the embodiment (NiCo / MCM-41) is significantly improved. As the content of the second metal Co increases from low to high (Examples 1 to 4), the conversion rate of vanillin first increases and then decreases. When the Ni / Co molar ratio is 4:1, the conversion rate reaches the maximum, and the selectivity of the target product reaches 72.96%. This indicates that the doping of an appropriate amount of metal Co enhances the interaction between the metal particles and the support, and promotes the dispersion of the metal active components in the nickel-based catalyst. Subsequently, the effect of adding acid on the product yield was investigated. With the increase of the silicon-aluminum ratio, the conversion rate of vanillin and the selectivity of the target product dimethoxytetramethylphenol (MMP) first increased and then decreased. When the silicon-aluminum ratio was 60 and the reaction conditions were the same (Example 6), the catalytic effect of the catalyst reached the maximum value, the conversion rate of vanillin was 91.85%, and the selectivity of the target product MMP was 93.49%. Compared with the catalyst without adding acid, the conversion rate and selectivity were both increased by more than 20%, indicating that the addition of acid further increased the conversion rate of vanillin and the selectivity of the target product. When the silicon-aluminum ratio was increased to 80, the conversion rate of vanillin and the selectivity of MMP began to decline.

[0067] Figure 1 The XRD spectrum of the catalyst is shown in Figure 1. As can be seen from the figure, the series of catalysts synthesized all show characteristic diffraction peaks of elemental Ni at 2θ = 44.3°, 51.7°, and 76.6°, which are consistent with the Ni standard card (PDF#04-0850), corresponding to the (111), (200), and (220) crystal planes of elemental Ni, respectively. No obvious characteristic diffraction peaks of metallic Co were found, which may be due to the good dispersion of Co. Compared with the Ni / MCM-41 catalyst, after the introduction of metallic Co, the diffraction peak of metallic Ni in the NiCo / MCM-41 catalyst shifted slightly to the left, which may be due to the change in the structure of the active component Ni in the catalyst. At the same time, it was found that the characteristic diffraction peak of Ni became broadened, which indicates that the introduction of Co promoted the high dispersion of metallic Ni particles.

[0068] Figure 2 This is the HR-TEM spectrum of the catalyst. It can be seen from the figure that the metal particles are evenly distributed on the surface of the carrier. The average grain size of the comparative example is 36.42nm, and the average grain size of Example 3 is 17.88nm. This shows that the doping of metal Co can effectively inhibit the agglomeration of metal particles, promote the dispersion of metal particles Ni in the catalyst, and expose more active components to improve its catalytic activity.

[0069] The present invention can also be implemented in other types of embodiments. Those familiar with the art can make corresponding changes based on the present invention, but these changes should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a NiCo / MCM-41 catalyst for converting lignin derivatives, characterized in that: The following steps are involved: (1) Sodium silicate, sodium metaaluminate, hexadecyltrimethylammonium bromide and deionized water were weighed in a certain molar ratio and dissolved in deionized water, stirred evenly to form a mixed solution, and then sulfuric acid was slowly added dropwise to the mixed solution and continued to stir at room temperature for a certain period of time; (2) The stirred mixed solution is placed in a hydrothermal kettle, and after a certain period of hydrothermal time, it is taken out for washing, filtering, drying, and finally calcining to obtain the molecular sieve carrier MCM-41; (3) nickel salt and cobalt salt in a certain molar ratio are dissolved in deionized water, ultrasonicated until completely dissolved, and then added dropwise to the molecular sieve support MCM-41. After standing and drying, a catalyst precursor is obtained; (4) After calcining the catalyst precursor, it is reduced in a hydrogen atmosphere to obtain a NiCo / MCM-41 catalyst; The silicon-aluminum ratio of the molecular sieve carrier MCM-41 is 60; the molar ratio of the nickel salt and the cobalt salt is 4:

1.

2. The method for preparing the NiCo / MCM-41 catalyst according to claim 1, wherein: In step (1), the molar ratio of sodium silicate, sodium metaaluminate, hexadecyltrimethylammonium bromide and deionized water is 1:0.0063~0.0125:0.2:100, and the concentration of sulfuric acid is 1 mol / L.

3. The method for preparing the NiCo / MCM-41 catalyst according to claim 1, wherein: In step (2), the sample hydrothermal temperature is 110° C., the hydrothermal time is 48 h, the roasting temperature is 550° C., and the roasting time is 4 h.

4. The method for preparing the NiCo / MCM-41 catalyst according to claim 1, wherein: The nickel salt in step (3) is one of nickel nitrate, nickel acetate, nickel sulfate and nickel chloride, and the cobalt salt is one of cobalt nitrate, cobalt sulfate and cobalt chloride.

5. The method for preparing the NiCo / MCM-41 catalyst according to claim 1, wherein: In step (4), the catalyst precursor is calcined at a temperature of 550° C. for 4 h, and the reduction condition is calcined at 550° C. for 4 h at a heating rate of 2–5° C. / min, wherein the hydrogen gas flow rate is 40–100 ml / min.

6. The NiCo / MCM-41 catalyst prepared according to the preparation method according to any one of claims 1 to 5.

7. Use of the NiCo / MCM-41 catalyst according to claim 6 in the hydrogenation conversion of lignin derivatives.

8. The use according to claim 7, characterized in that: The lignin derivative vanillin, NiCo / MCM-41 catalyst and reaction solvent are mixed and placed in a high-pressure batch reactor. The air in the reaction device is purged with N2, and then high-purity hydrogen is filled in to react. After the reaction is completed, the reaction product is filtered to obtain aromatic phenol chemicals.

9. The use according to claim 8, characterized in that: The reaction temperature is 120~200℃; the reaction pressure is 1~2.5MPa; the reaction time is 2h; the stirring rate is 400~700r / min; the amount of NiCo / MCM-41 catalyst is 20wt% of the lignin derivative; and the reaction solvent is methanol solvent.

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