Method for preparing guaiacol monomer product by catalyzing selective hydrogenolysis of lignin through aluminum oxide loaded nickel and nickel-tin alloy

Abstract

The invention discloses a method for preparing guaiacol monomer products by catalyzing selective hydrogenolysis of lignin through aluminum oxide loaded nickel and nickel-tin alloy. The catalyst simultaneously containing metal nickel and nickel-tin alloy active phases is prepared by adopting a urea precipitation method, organic soluble lignin is taken as a raw material, a mixture of alcohol substances and water is taken as a solvent, and the aluminum oxide loaded metal nickel and nickel-tin alloy catalyst prepared by adopting the urea precipitation method is added; and replacing air in the reaction kettle with inert gas, pressurizing to 1.0-3.0 MPa, and stirring at 210-270 DEG C for 1-6 hours to convert the organic soluble lignin into a compound mainly comprising guaiacol monomer products with high selectivity. The catalyst is simple in preparation process and low in cost, the lignin depolymerization reaction has the advantages of mild conditions, safe operation process and the like, and the obtained guaiacol product can be used for preparing chemicals such as food additives or medical intermediates.

Description

Technical Field

[0001] The invention relates to the depolymerization of agricultural and forestry wastes, and in particular to a method for preparing monophenol compounds by selective hydrogenolysis of lignin catalyzed by nickel metal and nickel-tin alloy supported by aluminum oxide, and belongs to the field of high-value utilization of renewable biomass. Background Art

[0002] Lignin, as an important component of biomass, contains a large number of aromatic ring structures in its structure. It is the only renewable aromatic polymer containing benzene ring structures that exists in large quantities in nature. At the same time, lignin also contains a variety of functional groups such as hydroxyl and aldehyde groups. Studies have shown that lignin can be depolymerized by various chemical methods to obtain high-value-added platform chemicals, which is conducive to the efficient utilization of all components of biomass. Pyrolysis, hydrolysis, oxidative depolymerization and hydrogenation depolymerization are widely used in the field of catalytic conversion of lignin. Thermochemical depolymerization of lignin usually needs to be carried out at a higher reaction temperature, resulting in high energy consumption of the entire reaction process. Hydrolysis requires the use of acid or alkaline catalysts, which will cause problems such as corrosion of reaction equipment and environmental unfriendliness. Oxidative depolymerization easily leads to deep oxidation of lignin substrates and reduces atom economy. Selective hydrogenation depolymerization can efficiently break specific chemical bonds in lignin, while not hydrogenating benzene rings and retaining the aromaticity of the product. The method of selective hydrogenation depolymerization of lignin has the advantages of low reaction energy consumption, environmental friendliness, and high product selectivity.

[0003] The hydrogenation and depolymerization of lignin is usually carried out under high-pressure hydrogen conditions, but the flammable and explosive properties of hydrogen can cause safety hazards during transportation and storage. In addition, hydrogen currently mainly comes from steam reforming of natural gas or methane, which inevitably releases carbon dioxide during the hydrogen production process, exacerbating the greenhouse effect. The catalytic reforming reaction of alcohols can provide hydrogen for lignin depolymerization in situ. This process avoids the use of external hydrogen and provides a new method for the high-value conversion of lignin.

[0004] Guaiacol is an important fine chemical intermediate with a wide range of applications. It can be used to produce spices such as vanillin, medicines such as potassium guaiacol sulfonate, guaiacol glycerol ether, isoproterenol and berberine, and plant growth regulators such as sodium 5-nitroguaiacol. At present, the industry mainly uses the diazotization hydrolysis method of o-anisidine to produce guaiacol, but this method inevitably uses acidic substances and diazonium salts, which has problems such as corrosion of reaction equipment and operational safety. There are also individual technologies in the prior art that involve the use of lignin depolymerization to prepare guaiacol products, but there are also problems such as the use of precious metal catalysts, high costs, the need for a high-pressure hydrogen atmosphere that brings safety hazards, and low yields of target products. The specific situation is as follows:

[0005] Chinese invention patent CN112608219B discloses a method for preparing 4-ethylphenol by depolymerizing lignin based on a liquid phase reforming system. The method uses Ru / C as a catalyst to catalyze the liquid phase reforming reaction of methanol and water to provide hydrogen for the depolymerization of organic soluble lignin, and 4-ethylphenol is obtained with high selectivity. The entire reaction process is mild and no external hydrogen is used. However, the above process uses a precious metal catalyst, which increases the cost of the method.

[0006] Chinese invention patent application CN115364862A discloses a method for preparing a nickel-based catalyst and its application in the depolymerization process of lignin. The method uses a mixed alkali co-precipitation method of NaOH and Na2CO3 to prepare a nickel-based layered hydroxide precursor, and then obtains a nickel-based catalyst by roasting and reducing operations. However, due to the problem of excessive local alkali concentration in the mixed alkali precipitation process, the distribution of species such as Ni and Sn is uneven, so that there is no Ni-Sn alloy in the catalyst. Figure 1 Only Ni metal is found in the reaction. However, the activity of Ni metal in catalyzing the production of hydrogen from alcohols is relatively low, which means that the catalyst needs to be in a 1.0MPaH2 atmosphere to catalyze the conversion of lignin to obtain phenolic monomer products. Due to the high hydrogen pressure, the entire reaction also poses a safety hazard. Summary of the invention

[0007] In order to overcome the shortcomings of the prior art and prepare guaiacol monomer substances with high added value, the present invention aims to provide a method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina without using precious metals and reducing the safety hazards caused by the use of external H2. The total yield of monophenol products from lignin depolymerization reaches 113.3-171.4 mg g -1 Among them, the selectivity of guaiacol monomer substances reached 40.2% to 46.1%.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] The invention discloses a method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloy, which is characterized in that: organic soluble lignin is used as raw material, a mixture of alcohol and water is used as solvent, metallic nickel and nickel-tin alloy catalysts supported by alumina prepared by urea precipitation method are added, the air in a reaction kettle is replaced by inert gas, and after being pressurized to 1.0-3.0 MPa, the reaction kettle is stirred at 210-270°C for 1-6 hours to highly selectively convert the organic soluble lignin into compounds mainly containing guaiacol monomer products; the nickel-tin alloy comprises Ni4Sn, Ni3Sn, NiSn and Ni3Sn2; and Sn accounts for 5.9%-50.6% of the mass of the entire alumina-supported metallic nickel and nickel-tin alloy catalysts.

[0010] To further achieve the purpose of the present invention, preferably, the alumina-loaded metallic nickel and nickel-tin alloy catalysts prepared by the urea precipitation method are prepared by mixing and stirring a urea solution and a mixed metal salt solution, and then undergoing hydrothermal, washing, drying, roasting, and reduction steps; the mixed metal salt solution is obtained by placing nickel salt, tin salt and aluminum salt in deionized water.

[0011] Preferably, the ratio of the amount of nickel salt to the amount of tin salt in the mixed metal salt solution is 1:1 to 10:1, and the ratio of the sum of the amount of nickel salt and tin salt to the amount of aluminum salt is 6:1 to 3:1;

[0012] The concentration of urea in the urea solution is 0.5-2.0 mol L -1 ;

[0013] The hydrothermal condition is to maintain the temperature at 90°C for 12 to 24 hours;

[0014] The calcination is to heat the dried product in air at 5-10°C min -1 The heating rate is from room temperature to 450-650°C, and sintered at 450-650°C for 2-4h;

[0015] The reduction is to introduce H2 into the solid product obtained after calcination at 5-10℃min -1 The heating rate is from room temperature to 450-650°C, and the reduction is carried out at 450-650°C for 2-4h.

[0016] Preferably, the nickel salt is nickel nitrate; the aluminum salt is aluminum nitrate; and the tin salt is tin chloride;

[0017] The concentration of the mixed metal salt solution A is 0.5 to 1.0 mol L -1 ;

[0018] The washing comprises washing the slurry with deionized water until the pH value is 7.0;

[0019] The drying is carried out at 100-110°C.

[0020] Preferably, the pores of the alumina-supported metal nickel and nickel-tin alloy catalyst are mainly mesopores, and the pore diameters are concentrated in the range of 4 to 20 nm;

[0021] Ni accounts for 25.2% to 70.6% of the mass of the entire alumina-supported metallic nickel and nickel-tin alloy catalyst, Al accounts for 7.0% to 9.6%, and the remainder is the mass of O.

[0022] Preferably, the mass ratio of the alumina-supported metallic nickel and nickel-tin alloy catalyst to lignin is 1:1 to 1:2.

[0023] Preferably, the lignin is derived from agricultural and forestry wastes, and the agricultural and forestry wastes include bagasse, corn cobs or bamboo.

[0024] Preferably, the alcohol substance is one or more of methanol, ethanol and isopropanol; and the volume ratio of the alcohol substance to water in the mixture of the alcohol substance and water is 1:19 to 19:1.

[0025] Preferably, the inert gas is argon or nitrogen; the reactor is a batch reactor; the stirring speed is 600-800 r min -1 .

[0026] Preferably, the guaiacol monomer product mainly comprises 4-ethylguaiacol and 4-propylguaiacol.

[0027] Compared with the prior art, the present invention has the following advantages and effects:

[0028] 1) Compared with the existing organic synthesis preparation route, the method for preparing guaiacol monomer products by catalyzing the selective hydrogenolysis of lignin by alumina-supported nickel and nickel-tin alloy prepared by the present invention has cheap and renewable raw materials, a simple reaction process, and is environmentally friendly.

[0029] 2) Compared with other lignin depolymerization methods, the method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloy prepared by the present invention has relatively mild reaction conditions, and the total yield of monophenol products of lignin depolymerization reaches 113.3-171.4 mg g -1 Among them, the selectivity of guaiacol monomer substances reached 40.2% to 46.1%.

[0030] 3) The catalyst of the present invention exhibits a mesoporous structure, which is beneficial to the diffusion and adsorption of lignin macromolecules and intermediates during the hydrogenolysis process, and further beneficial to the depolymerization of lignin.

[0031] 4) The catalyst of the present invention contains two active phases, namely, nickel-tin alloy and nickel metal. The nickel-tin alloy accelerates the liquid phase reforming hydrogen production reaction of alcohol substances, while the metal nickel is beneficial to the breaking of the CO chemical bond in lignin. Both promote the conversion of lignin, thereby obtaining a high yield of guaiacol monomer products. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the XRD spectrum of the Ni-Sn / Al2O3-1 catalyst obtained in Example 1.

[0033] Figure 2 This is the TEM image of the Ni-Sn / Al2O3-1 catalyst obtained in Example 1.

[0034] Figure 3 This is the TEM image of the Ni-Sn / Al2O3-1 catalyst obtained in Example 1.

[0035] Figure 4 This is the N2 adsorption-desorption curve of the Ni-Sn / Al2O3-1 catalyst obtained in Example 1.

[0036] Figure 5 This is the pore size distribution diagram of the Ni-Sn / Al2O3-1 catalyst obtained in Example 1.

[0037] Figure 6 This is the GC-FID chart of the volatile product obtained in Example 1.

[0038] Figure 7 This is the XRD spectrum of the Ni / Al2O3 catalyst obtained in Comparative Example 2. DETAILED DESCRIPTION

[0039] In order to better understand the present invention, the present invention is further described below with reference to the accompanying drawings and embodiments, but it should be noted that the embodiments of the present invention are not limited thereto.

[0040] In view of the environmental pollution and other problems existing in the existing methods for producing guaiacol products, the present invention develops a method for preparing guaiacol monomers from lignin, which can significantly reduce the cost of raw materials and the dependence on petrochemical materials. In view of the use of precious metal catalysts and high-pressure hydrogen in the existing lignin hydrogenolysis technology, the present invention develops a non-precious metal Ni-based catalyst, which can realize the conversion of lignin without adding H2, thereby further broadening the application prospects of lignin.

[0041] Generally speaking, Ni-based catalysts can break the CO chemical bonds in the lignin structure to obtain monophenol products, and are widely used in the field of hydrogenation and depolymerization of lignin. However, in the liquid-phase reforming hydrogen production reaction of alcohols, Ni-based catalysts can crack the C-OH bonds in the alcohol structure and catalyze the methanation reaction to reduce the H2 yield of the entire process. The core feature of the present invention is that the catalyst is alumina-supported metallic nickel and nickel-tin alloy, and the catalyst contains two active sites, nickel metal and nickel-tin alloy, which catalyze the reforming of alcohols to produce hydrogen and break the CO chemical bonds in lignin, respectively, thereby achieving the purpose of preparing guaiacol monomer products by depolymerization of lignin.

[0042] The present invention adopts a urea precipitation method to prepare a catalyst containing both Ni metal and Ni-Sn alloy. Urea is neutral at low temperatures and can form a uniform solution with metal particles; when the solution temperature rises, urea decomposes and gradually increases the pH value of the solution, so this method avoids the phenomenon of excessive local alkali concentration in the mixed alkali method, and further can synthesize a precursor with high crystallinity and uniform distribution of metal ions, thereby promoting the formation of Ni-Sn alloy species. Therefore, the present invention adopts a urea precipitation method to prepare alumina-supported metal nickel and nickel-tin alloy catalysts, and utilizes the catalyst to highly selectively convert organic soluble lignin into compounds mainly composed of guaiacol monomer products; the nickel-tin alloy of the catalyst includes Ni4Sn, Ni3Sn, NiSn and Ni3Sn2; wherein Sn accounts for 5.9% to 50.6% of the mass of the entire alumina-supported metal nickel and nickel-tin alloy catalyst. Ni accounts for 25.2% to 70.6% of the mass of the entire alumina-supported metallic nickel and nickel-tin alloy catalyst, Al accounts for 7.0% to 9.6%, and the remainder is the mass of O.

[0043] The alumina-supported metal nickel and nickel-tin alloy catalyst prepared by the urea precipitation method of the present invention is prepared by mixing a urea solution and a mixed metal salt solution, and then undergoing hydrothermal, washing, drying, roasting, and reduction steps. The urea precipitation method has certain similarities with the mixed alkali co-precipitation method of Chinese invention patent application CN115364862A, and the core feature is that the NaOH and Na2CO3 mixed alkali solution are replaced by a urea solution. The key catalyst contains two types of active sites, nickel metal and nickel-tin alloy, and realizes the conversion of lignin to prepare guaiacol monomer products without the addition of H2, and the total yield of monophenol products of lignin depolymerization reaches 113.3-171.4 mg g -1 , wherein the selectivity of guaiacol monomer substances reaches 40.2% to 46.1%. The catalyst preparation process of the present invention is simple and the price is low. The catalyst catalyzes the hydrogenation and depolymerization of lignin under mild conditions, has high operating safety and good industrialization. In the preparation of the catalyst, the selection and dosage of nickel salt, tin salt and aluminum salt in the mixed metal salt solution, the concentration of urea in the urea solution, the specific conditions such as hydrothermal, washing, drying, roasting and reduction can be obtained through experiments according to the purpose of the present invention. The pores of the alumina-loaded metal nickel and nickel-tin alloy catalysts obtained by the present invention are mainly mesopores, and the pore diameters are concentrated in 4 to 20 nm.

[0044] The focus of the present invention is that the catalyst contains two types of active sites, nickel metal and nickel-tin alloy; there is no similar approach in the prior art; as for the specific preparation based on the clear characteristics of the catalyst combined with the existing technology, it can be achieved, especially the raw materials and dosage ratios and process conditions can be achieved on the basis of the existing technology and according to the characteristics of the catalyst.

[0045] Example 1

[0046] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported on alumina.

[0047] The preparation of the catalyst comprises the following steps:

[0048] (1) Weigh 19.83 g Ni(NO3)2·6H2O, 1.54 g SnCl2·2H2O and 9.38 g Al(NO3)3·9H2O, add them to 100 mL deionized water, and stir vigorously to obtain a mixed metal salt solution A. Weigh 60.0 g urea and dissolve it in 30 mL deionized water, and stir the obtained urea solution. Add the mixed metal salt solution A and the urea solution to a hydrothermal kettle, then place the hydrothermal kettle in an oil bath, heat to 90°C and maintain for 24 hours, and stir vigorously. After the reaction is completed, wash the slurry with deionized water to pH = 7. Dry the above solid at 100°C to obtain a catalyst precursor.

[0049] (2) After the catalyst precursor is dried, place it in a muffle furnace and heat it at 5°C min in an air atmosphere. -1 The temperature was raised from room temperature to 550°C at a rate of 1.5 °C and calcined at this temperature for 4 h. The calcined solid was placed in a quartz tube and H2 was introduced at 5 °C min -1 The heating rate was increased from room temperature to 550°C and reduced at this temperature for 4 hours to obtain alumina-supported metallic nickel and nickel-tin alloy catalysts, which were recorded as Ni-Sn / Al2O3-1.

[0050] from Figure 1 It can be seen that the diffraction peaks belonging to Ni metal and Ni3Sn alloy can be clearly observed in the Ni-Sn / Al2O3-1 catalyst. Figure 2 and 3 TEM analysis of the Ni-Sn / Al2O3-1 catalyst revealed two lattice fringe spacings of 0.20 nm and 0.27 nm, which were attributed to the (111) crystal plane of Ni metal (JCPDS: 04-0850) and the (110) crystal plane spacing of Ni3Sn alloy (JCPDS: 35-1362), respectively. Figure 4 As shown, the Ni-Sn / Al2O3-1 catalyst exhibits a type IV isotherm, indicating that the catalyst has a mesoporous structure and the pore size is mostly concentrated between 4 and 20 nm ( Figure 5 ). The Ni-Sn / Al2O3-1 catalyst prepared in this example has a mesoporous structure, which is conducive to the diffusion of lignin macromolecules and intermediates during hydrogenolysis, thereby promoting the conversion of lignin.

[0051] The specific operation of Ni-Sn / Al2O3-1 catalyzed selective hydrogenolysis of lignin is as follows: the conversion experiment of lignin is carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-1, 10mL methanol and 10mL water are added to the above-mentioned reactor, and the air in the reactor body is replaced with high-purity argon, and then 1.0MPa of argon is filled. Under mechanical stirring, the reactor is heated to 250°C and maintained for 4h. After the reaction is completed, the gaseous products obtained after the reaction are collected and analyzed by gas chromatography. The liquid product is filtered, the solid component obtained is washed with methanol, and 0.08g internal standard solution (dimethyl phthalate is an internal standard, 1.0g dimethyl phthalate is added to 19.0g n-propanol to obtain 5wt.% internal standard solution) is added to the obtained liquid. Methanol is used to be fixed to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0052] The test results of this embodiment are as follows Figure 6 As shown in Table 1, Figure 6 The GC-FID diagram of the volatile product obtained in Example 1; product peaks at different retention times were obtained by analysis and detection, and the product distribution is shown in Table 1, wherein the guaiacol monomer products are mainly 4-ethylguaiacol and 4-propylguaiacol.

[0053] After quantitative analysis, 8.27 mmol H2 was detected after the reaction, and 171.4 mg g of lignin was obtained by conversion. -1 of monophenol products, among which the selectivity of guaiacol monomer products was 46.1%.

[0054] Table 1 Distribution and yield of products obtained from lignin hydrogenolysis in methanol and water reforming system

[0055]

[0056]

[0057] Example 2

[0058] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported on alumina.

[0059] The preparation of the catalyst comprises the following steps:

[0060] (1) Weigh 19.83 g Ni(NO3)2·6H2O, 15.40 g SnCl2·2H2O and 17.05 g Al(NO3)3·9H2O and add them to 360 mL deionized water, stir vigorously, and obtain a mixed metal salt solution A. Weigh 60.0 g urea and dissolve it in 120 mL deionized water, and stir the obtained urea solution. Add the mixed metal salt solution A and the urea solution to a hydrothermal kettle, then place the hydrothermal kettle in an oil bath, heat to 90°C and keep for 24 hours, and stir vigorously. After the reaction is completed, wash the slurry with deionized water until the pH is 7. Dry the above solid at 100°C to obtain a catalyst precursor.

[0061] (2) After the catalyst precursor is dried, place it in a muffle furnace and heat it at 5°C min in an air atmosphere. -1 The temperature was raised from room temperature to 550°C at a rate of 1.5 °C and calcined at this temperature for 4 h. The calcined solid was placed in a quartz tube and H2 was introduced at 5 °C min -1 The heating rate was increased from room temperature to 550°C and reduced at this temperature for 4 hours to obtain alumina-supported metallic nickel and nickel-tin alloy catalysts, which were recorded as Ni-Sn / Al2O3-2.

[0062] The specific operation of Ni-Sn / Al2O3-2 catalyzed selective hydrogenolysis of lignin is as follows: the conversion experiment of lignin is carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-2, 10mL methanol and 10mL water are added to the above-mentioned reactor, and the air in the reactor body is replaced with high-purity nitrogen, and then 1.0MPa of nitrogen is filled. Under mechanical stirring, the reactor is heated to 250°C and maintained for 4h. After the reaction is completed, the gaseous products obtained after the reaction are collected and analyzed by gas chromatography. The liquid product is filtered, the solid component obtained is washed with methanol, and 0.08g internal standard solution (dimethyl phthalate is an internal standard, 1.0g dimethyl phthalate is added to 19.0g n-propanol to obtain 5wt.% internal standard solution) is added to the obtained liquid. Methanol is used to be fixed to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0063] After quantitative analysis, 7.07 mmol H2 was detected after the reaction, and 160.2 mg g of lignin was obtained by conversion. -1 The selectivity of guaiacol monomer products is 40.3%.

[0064] Example 3

[0065] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported on alumina.

[0066] The preparation of the catalyst comprises the following steps:

[0067] (1) Weigh 19.83 g Ni(NO3)2·6H2O, 1.54 g SnCl2·2H2O and 4.69 g Al(NO3)3·9H2O, add them to 100 mL deionized water, and stir vigorously to obtain a mixed metal salt solution A. Weigh 60.0 g urea and dissolve it in 30 mL deionized water, and stir the obtained urea solution. Add the mixed metal salt solution A and the urea solution to a hydrothermal kettle, then place the hydrothermal kettle in an oil bath, heat to 90°C and keep for 24 hours, and stir vigorously. After the reaction is completed, wash the slurry with deionized water to pH = 7. Dry the above solid at 100°C to obtain a catalyst precursor.

[0068] (2) After the catalyst precursor is dried, place it in a muffle furnace and heat it at 5°C min in an air atmosphere. -1 The temperature was raised from room temperature to 550°C at a rate of 1.5 °C and calcined at this temperature for 4 h. The calcined solid was placed in a quartz tube and H2 was introduced at 5 °C min -1 The heating rate was increased from room temperature to 550°C and reduced at this temperature for 4 hours to obtain alumina-supported metallic nickel and nickel-tin alloy catalysts, recorded as Ni-Sn / Al2O3-3.

[0069] The specific operation of Ni-Sn / Al2O3-3 catalyzed selective hydrogenolysis of lignin is as follows: the conversion experiment of lignin is carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-3, 10mL methanol and 10mL water are added to the above-mentioned reactor, and the air in the reactor body is replaced with high-purity nitrogen, and then 1.0MPa of nitrogen is filled. Under mechanical stirring, the reactor is heated to 250°C and maintained for 4h. After the reaction is completed, the gaseous products obtained after the reaction are collected and analyzed by gas chromatography. The liquid product is filtered, the solid component obtained is washed with methanol, and 0.08g internal standard solution (dimethyl phthalate is an internal standard, 1.0g dimethyl phthalate is added to 19.0g n-propanol to obtain 5wt.% internal standard solution) is added to the obtained liquid. Methanol is used to be fixed to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0070] After quantitative analysis, 6.68 mmol H2 was detected after the reaction, and 158.2 mg g of lignin was obtained by conversion. -1of monophenol products, among which the selectivity of guaiacol monomer products was 41.6%.

[0071] Example 4

[0072] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported on alumina.

[0073] The preparation process of the catalyst was the same as that of Example 1, except that the oil bath time was adjusted to 12 h to prepare a Ni-Sn / Al2O3-4 catalyst.

[0074] The specific operation of Ni-Sn / Al2O3-4 catalyzed selective hydrogenolysis of lignin is as follows: the conversion experiment of lignin is carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-4, 10mL methanol and 10mL water are added to the above-mentioned reactor, and the air in the reactor body is replaced with high-purity argon, and then 1.0MPa of argon is filled. Under mechanical stirring, the reactor is heated to 250°C and maintained for 4h. After the reaction is completed, the gaseous products obtained after the reaction are collected and analyzed by gas chromatography. The liquid product is filtered, the solid component obtained is washed with methanol, and 0.08g internal standard solution (dimethyl phthalate is an internal standard, 1.0g dimethyl phthalate is added to 19.0g n-propanol to obtain 5wt.% internal standard solution) is added to the obtained liquid. Methanol is used to be fixed to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0075] After quantitative analysis, 8.01 mmol H2 was detected after the reaction, and 168.5 mg g of lignin was obtained by conversion. -1 of monophenol products, among which the selectivity of guaiacol monomer products was 43.2%.

[0076] Example 5

[0077] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported on alumina.

[0078] The preparation process of the catalyst is the same as that of Example 1, except that the calcination temperature of the catalyst is adjusted to 650° C. to prepare a Ni—Sn / Al 2 O 3 -5 catalyst.

[0079] The specific operation of Ni-Sn / Al2O3-5 catalyzed selective hydrogenolysis of lignin is as follows: the conversion experiment of lignin is carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-5, 10mL methanol and 10mL water are added to the above reactor, and the air in the reactor body is replaced with high-purity nitrogen, and then 1.0MPa of nitrogen is filled. Under mechanical stirring, the reactor is heated to 250°C and maintained for 4h. After the reaction is completed, the gaseous products obtained after the reaction are collected and analyzed by gas chromatography. The liquid product is filtered, the solid component obtained is washed with methanol, and 0.08g internal standard solution (dimethyl phthalate is an internal standard, 1.0g dimethyl phthalate is added to 19.0g n-propanol to obtain 5wt.% internal standard solution) is added to the obtained liquid. Methanol is used to make the volume to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0080] After quantitative analysis, 7.12 mmol H2 was detected after the reaction, and 140.3 mg g of lignin was obtained by conversion. -1 The selectivity of guaiacol monomer products is 41.7%.

[0081] Example 6

[0082] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported on alumina.

[0083] The preparation process of the catalyst is the same as that of Example 1, except that the calcination temperature of the catalyst is adjusted to 450° C. to prepare a Ni—Sn / Al 2 O 3 -7 catalyst.

[0084] The specific operation of Ni-Sn / Al2O3-7 catalyzed selective hydrogenolysis of lignin is as follows: the conversion experiment of lignin is carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-7, 10mL methanol and 10mL water are added to the above-mentioned reactor, and the air in the reactor body is replaced with high-purity argon, and then 1.0MPa of argon is filled. Under mechanical stirring, the reactor is heated to 250°C and maintained for 4h. After the reaction is completed, the gaseous products obtained after the reaction are collected and analyzed by gas chromatography. The liquid product is filtered, the solid component obtained is washed with methanol, and 0.08g internal standard solution (dimethyl phthalate is an internal standard, 1.0g dimethyl phthalate is added to 19.0g n-propanol to obtain 5wt.% internal standard solution) is added to the obtained liquid. Methanol is used to be fixed to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0085] After quantitative analysis, 7.01 mmol H2 was detected after the reaction, and 144.5 mg g of lignin was obtained by conversion. -1 of monophenol products, among which the selectivity of guaiacol monomer products was 43.2%.

[0086] Example 7

[0087] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported on alumina.

[0088] The preparation process of the catalyst is the same as that of Example 1, except that the reduction temperature of the catalyst is adjusted to 650° C. to prepare a Ni—Sn / Al 2 O 3 -6 catalyst.

[0089] The specific operation of Ni-Sn / Al2O3-6 catalyzed selective hydrogenolysis of lignin is as follows: the conversion experiment of lignin is carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-6, 10mL methanol and 10mL water are added to the above-mentioned reactor, and the air in the reactor body is replaced with high-purity argon, and then 1.0MPa of argon is filled. Under mechanical stirring, the reactor is heated to 250°C and maintained for 4h. After the reaction is completed, the gaseous products obtained after the reaction are collected and analyzed by gas chromatography. The liquid product is filtered, the solid component obtained is washed with methanol, and 0.08g internal standard solution (dimethyl phthalate is an internal standard, 1.0g dimethyl phthalate is added to 19.0g n-propanol to obtain 5wt.% internal standard solution) is added to the obtained liquid. Methanol is used to be fixed to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0090] After quantitative analysis, 7.39 mmol H2 was detected after the reaction, and 156.9 mg g of lignin was obtained by conversion. -1 The selectivity of guaiacol monomer products is 41.8%.

[0091] Example 8

[0092] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina, wherein the specific operation is as follows:

[0093] The lignin was converted by catalysis of Ni-Sn / Al2O3-1, and the specific steps were as follows. The conversion experiment of lignin was carried out in a 50mL stainless steel reactor. First, 0.2g bagasse lignin, 0.1g Ni-Sn / Al2O3-1, 10mL methanol and 10mL water were added to the above reactor, and the air in the reactor was replaced by high-purity argon, and then 1.0MPa of argon was filled. Under mechanical stirring, the reactor was heated to 250°C and maintained for 4h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the solid component obtained was washed with methanol, and 0.08g internal standard solution (dimethyl phthalate was an internal standard, and 1.0g dimethyl phthalate was added to 19.0g n-propanol to obtain 5wt.% internal standard solution) was added to the obtained liquid. Methanol was used to make the volume to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0094] After quantitative analysis, 5.29 mmol H2 was detected after the reaction, and 141.8 mg g of lignin was obtained by conversion. -1 The selectivity of monophenol products and guaiacol monomer products was 42.4%.

[0095] Example 9

[0096] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina, wherein the specific operation is as follows:

[0097] The lignin was converted using Ni-Sn / Al2O3-1 catalysis, and the specific steps were as follows. The conversion experiment of lignin was carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-1, 10mL methanol and 10mL water were added to the above reactor, and the air in the reactor was replaced with high-purity nitrogen, and then 1.0MPa of nitrogen was filled. Under mechanical stirring, the reactor was heated to 210°C and maintained for 4h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the solid component obtained was washed with methanol, and 0.08g of internal standard solution (dimethyl phthalate was an internal standard, and 1.0g of dimethyl phthalate was added to 19.0g of n-propanol to obtain 5wt.% of internal standard solution) was added to the obtained liquid. Methanol was used to make the volume to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0098] After quantitative analysis, 3.34 mmol H2 was detected after the reaction, and 118.6 mg g of lignin was obtained by conversion. -1 The selectivity of monophenol products and guaiacol monomer products was 43.6%.

[0099] Example 10

[0100] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina, wherein the specific operation is as follows:

[0101] The lignin was converted using Ni-Sn / Al2O3-1 catalytic conversion, and the specific steps were as follows. The conversion experiment of lignin was carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-1, 10mL methanol and 10mL water were added to the above reactor, and the air in the reactor was replaced with high-purity argon, and then 1.0MPa of argon was filled. Under mechanical stirring, the reactor was heated to 270°C and maintained for 4h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the solid component obtained was washed with methanol, and 0.08g of internal standard solution (dimethyl phthalate was an internal standard, and 1.0g of dimethyl phthalate was added to 19.0g of n-propanol to obtain an internal standard solution of 5wt.%) was added to the obtained liquid. Methanol was used to make the volume to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0102] After quantitative analysis, 8.96 mmol H2 was detected after the reaction, and 165.3 mg g of lignin was obtained by conversion. -1 The selectivity of monophenol products and guaiacol monomer products was 40.9%.

[0103] Embodiment 11

[0104] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina, wherein the specific operation is as follows:

[0105] The lignin was converted by catalysis of Ni-Sn / Al2O3-1, and the specific steps were as follows. The conversion experiment of lignin was carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-1, 10mL methanol and 10mL water were added to the above reactor, and the air in the reactor was replaced by high-purity argon, and then 1.0MPa of argon was filled. Under mechanical stirring, the reactor was heated to 250°C and maintained for 1h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the solid component obtained was washed with methanol, and 0.08g of internal standard solution (dimethyl phthalate was an internal standard, and 1.0g of dimethyl phthalate was added to 19.0g of n-propanol to obtain an internal standard solution of 5wt.%) was added to the obtained liquid. Methanol was used to make the volume to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0106] After quantitative analysis, 2.09 mmol H2 was detected after the reaction, and 88.4 mg g of lignin was obtained by conversion. -1 The selectivity of monophenol products and guaiacol monomer products was 43.1%.

[0107] Example 12

[0108] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina, wherein the specific operation is as follows:

[0109] The lignin was converted by catalysis of Ni-Sn / Al2O3-1, and the specific steps were as follows. The conversion experiment of lignin was carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-1, 10mL methanol and 10mL water were added to the above reactor, and the air in the reactor was replaced by high-purity argon, and then 1.0MPa of argon was filled. Under mechanical stirring, the reactor was heated to 250°C and maintained for 6h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the solid component obtained was washed with methanol, and 0.08g internal standard solution (dimethyl phthalate was an internal standard, and 1.0g dimethyl phthalate was added to 19.0g n-propanol to obtain 5wt.% internal standard solution) was added to the obtained liquid. Methanol was used to make the volume to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0110] After quantitative analysis, 8.46 mmol H2 was detected after the reaction, and 167.9 mg g of lignin was obtained by conversion. -1 The selectivity of guaiacol monomer products is 45.0%.

[0111] Embodiment 13

[0112] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina, wherein the specific operation is as follows:

[0113] Use Ni-Sn / Al2O3-1 to catalyze the conversion of lignin, and the specific steps are as follows. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-1, 18mL methanol and 2mL water are added to the above-mentioned reactor, and the air in the reactor body is replaced with high-purity argon, and then 1.0MPa of argon is filled. Under mechanical stirring, the reactor is heated to 250°C and maintained for 4h. After the reaction is completed, the gaseous products obtained after the reaction are collected and analyzed by gas chromatography. The liquid product is filtered, the solid component obtained is cleaned with methanol, and 0.08g internal standard solution (dimethyl phthalate is an internal standard, and 1.0g dimethyl phthalate is added to 19.0g n-propanol to obtain 5wt.% of internal standard solution) is added to the obtained liquid. Methanol is used to be fixed to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0114] After quantitative analysis, 7.52 mmol H2 was detected after the reaction, and 156.6 mg g of lignin was obtained by conversion. -1 The selectivity of monophenol products and guaiacol monomer products was 42.0%.

[0115] Embodiment 14

[0116] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina, wherein the specific operation is as follows:

[0117] Use Ni-Sn / Al2O3-1 to catalyze the conversion of lignin, and the specific steps are as follows. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-1, 2mL methanol and 18mL water are added to the above-mentioned reactor, and the air in the reactor body is replaced with high-purity argon, and then 1.0MPa of argon is filled. Under mechanical stirring, the reactor is heated to 250°C and maintained for 4h. After the reaction is completed, the gaseous products obtained after the reaction are collected and analyzed by gas chromatography. The liquid product is filtered, the solid component obtained is cleaned with methanol, and 0.08g internal standard solution (dimethyl phthalate is an internal standard, and 1.0g dimethyl phthalate is added to 19.0g n-propanol to obtain 5wt.% of internal standard solution) is added to the obtained liquid. Methanol is used to be fixed to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0118] After quantitative analysis, 3.65 mmol H2 was detected after the reaction, and 113.3 mg g of lignin was obtained by conversion. -1The selectivity of monophenol products and guaiacol monomer products was 41.6%.

[0119] Embodiment 15

[0120] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina, wherein the specific operation is as follows:

[0121] The lignin was converted by catalysis of Ni-Sn / Al2O3-1, and the specific steps were as follows. The conversion experiment of lignin was carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-1, 10mL ethanol and 10mL water were added to the above reactor, and the air in the reactor was replaced by high-purity argon, and then 1.0MPa of argon was filled. Under mechanical stirring, the reactor was heated to 250°C and maintained for 4h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the solid component obtained was washed with methanol, and 0.08g of internal standard solution (dimethyl phthalate was an internal standard, and 1.0g of dimethyl phthalate was added to 19.0g of n-propanol to obtain an internal standard solution of 5wt.%) was added to the obtained liquid. Methanol was used to make the volume to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0122] After quantitative analysis, 7.69 mmol H2 was detected after the reaction, and 155.1 mg g of lignin was obtained by conversion. -1 The selectivity of monophenol products and guaiacol monomer products was 40.4%.

[0123] Example 16

[0124] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina, wherein the specific operation is as follows:

[0125] The lignin was catalytically converted using Ni-Sn / Al2O3-1, and the specific steps were as follows. The conversion experiment of lignin was carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni-Sn / Al2O3-1, 10mL isopropanol and 10mL water were added to the above reactor, and the air in the reactor was replaced with high-purity argon, and then 1.0MPa of argon was filled. Under mechanical stirring, the reactor was heated to 250°C and maintained for 4h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the solid component obtained was washed with methanol, and 0.08g of internal standard solution (dimethyl phthalate was an internal standard, and 1.0g of dimethyl phthalate was added to 19.0g of n-propanol to obtain an internal standard solution of 5wt.%) was added to the obtained liquid. Methanol was used to make the volume to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0126] After quantitative analysis, 7.16 mmol H2 was detected after the reaction, and 138.4 mg g -1 The selectivity of monophenol products and guaiacol monomer products was 40.2%.

[0127] Embodiment 17

[0128] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina, wherein the specific operation is as follows:

[0129] The lignin was converted using Ni-Sn / Al2O3-1 catalysis, and the specific steps were as follows. The conversion experiment of lignin was carried out in a 50mL stainless steel reactor. First, 0.1g corncob lignin, 0.1g Ni-Sn / Al2O3-1, 10mL methanol and 10mL water were added to the above reactor, and the air in the reactor was replaced with high-purity argon, and then 1.0MPa of argon was filled. Under mechanical stirring, the reactor was heated to 250°C and maintained for 4h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the solid component obtained was washed with methanol, and 0.08g of internal standard solution (dimethyl phthalate was an internal standard, 1.0g of dimethyl phthalate was added to 19.0g of n-propanol to obtain 5wt.% of internal standard solution) was added to the obtained liquid. Methanol was used to make the volume to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0130] After quantitative analysis, 8.04 mmol H2 was detected after the reaction, and 158.7 mg g -1 The selectivity of monophenol products and guaiacol monomer products was 41.3%.

[0131] Embodiment 18

[0132] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina, wherein the specific operation is as follows:

[0133] The lignin was converted by catalysis of Ni-Sn / Al2O3-1, and the specific steps were as follows. The conversion experiment of lignin was carried out in a 50mL stainless steel reactor. First, 0.1g bamboo lignin, 0.1g Ni-Sn / Al2O3-1, 10mL methanol and 10mL water were added to the above reactor, and the air in the reactor was replaced by high-purity argon, and then 1.0MPa of argon was filled. Under mechanical stirring, the reactor was heated to 250°C and maintained for 4h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the solid component obtained was washed with methanol, and 0.08g of internal standard solution (dimethyl phthalate was an internal standard, and 1.0g of dimethyl phthalate was added to 19.0g of n-propanol to obtain 5wt.% of internal standard solution) was added to the obtained liquid. Methanol was used to make the volume to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0134] After quantitative analysis, 7.85 mmol H2 was detected after the reaction, and 155.2 mg g -1 The selectivity of monophenol products and guaiacol monomer products was 40.5%.

[0135] Comparative Example 1

[0136] The depolymerization of lignin without catalyst is as follows:

[0137] The conversion experiment of lignin was carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 10mL methanol and 10mL water were added to the above reactor, and the air in the reactor was replaced with high-purity argon, and then 1.0MPa of argon was filled. Under mechanical stirring, the reactor was heated to 250°C and maintained for 4h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the solid component obtained was washed with methanol, and 0.08g of internal standard solution (dimethyl phthalate was an internal standard, and 1.0g of dimethyl phthalate was added to 19.0g of n-propanol to obtain an internal standard solution of 5wt.%) was added to the obtained liquid. Methanol was used to make the volume to 25mL to obtain a liquid product. 1.0mL of the above mixture was taken out with a syringe and added to a sample injection bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0138] After quantitative analysis, no H2 was detected after the reaction, and 20.8 mg g -1 The selectivity of monophenol products and guaiacol monomer products was 30.2%.

[0139] Comparative Example 2

[0140] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by metal nickel supported on alumina.

[0141] The preparation of the catalyst comprises the following steps:

[0142] (1) Weigh 21.81 g Ni(NO3)2·6H2O and 9.38 g Al(NO3)3·9H2O and add them to 100 mL of deionized water, stir vigorously, and obtain a mixed metal salt solution A. Weigh 60.0 g urea and dissolve it in 30 mL of deionized water, stir for 12 h, and obtain a urea solution. Add the mixed metal salt solution A and the urea solution to a hydrothermal reactor, and place it in an oil bath at 90°C and heat for 24 h, stirring vigorously. After the reaction is completed, wash the slurry with deionized water until the pH is 7. Dry the above solid at 100°C to obtain a catalyst precursor.

[0143] (2) Place the dried catalyst precursor in a muffle furnace under air atmosphere at 5°C min -1 The temperature was raised from room temperature to 550°C at a rate of 1.5 °C and calcined at this temperature for 4 h. The calcined solid was placed in a quartz tube and H2 was introduced at a rate of 5 °C min -1 The heating rate was increased from room temperature to 550°C and reduced at this temperature for 4 hours to obtain an alumina-supported metal nickel catalyst, which was recorded as Ni / Al2O3.

[0144] from Figure 7It can be seen that only the diffraction peaks attributed to metal Ni are observed in the Ni / Al2O3 catalyst.

[0145] The specific operation of Ni / Al2O3 catalyzed selective hydrogenolysis of lignin is as follows: the conversion experiment of lignin is carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni / Al2O3, 10mL methanol and 10mL water are added to the above-mentioned reactor, and the air in the reactor body is replaced with high-purity argon, and then 1.0MPa of argon is filled. Under mechanical stirring, the reactor is heated to 250°C and maintained for 4h. After the reaction is completed, the gaseous products obtained after the reaction are collected and analyzed by gas chromatography. The liquid product is filtered, the solid component obtained is cleaned with methanol, and 0.08g internal standard solution (dimethyl phthalate is an internal standard, and 1.0g dimethyl phthalate is added to 19.0g n-propanol to obtain 5wt.% internal standard solution) is added to the obtained liquid. Methanol is used to be fixed to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0146] After the reaction, quantitative analysis showed that 96.9 mg g of lignin was converted in the Ni / Al2O3 catalytic system. -1 The monophenol product was obtained, the selectivity of guaiacol monomer was 34.3%, and 5.57 mmol H2 was detected.

[0147] Comparative Example 3

[0148] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by metal tin supported on alumina.

[0149] The preparation of the catalyst comprises the following steps:

[0150] (1) Weigh 1.54 g SnCl2·2H2O and 9.38 g Al(NO3)3·9H2O and add them to deionized water to obtain solution A. Weigh 60.0 g urea and dissolve it in deionized water to obtain a urea solution. Add the mixed metal salt solution A and the urea solution to a hydrothermal reactor, and place it in an oil bath at 90°C and heat it for 24 hours with vigorous stirring. After the reaction is completed, wash the slurry with deionized water until the pH is 7. Dry the above solid at 100°C to obtain a catalyst precursor.

[0151] (2) Place the dried catalyst precursor in a muffle furnace under air atmosphere at 5°C min -1 The temperature was raised from room temperature to 550°C at a rate of 1.5 °C and calcined at this temperature for 4 h. The calcined solid was placed in a quartz tube and H2 was introduced at a rate of 5 °C min -1The heating rate was increased from room temperature to 550°C and reduced at this temperature for 4 h to obtain an alumina-supported tin catalyst, recorded as Sn / Al2O3.

[0152] The specific operation of Sn / Al2O3 catalyzed selective hydrogenolysis of lignin is as follows: the conversion experiment of lignin is carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Sn / Al2O3, 10mL methanol and 10mL water are added to the above-mentioned reactor, and the air in the reactor body is replaced with high-purity argon, and then 1.0MPa of argon is filled. Under mechanical stirring, the reactor is heated to 250°C and maintained for 4h. After the reaction is completed, the gaseous products obtained after the reaction are collected and analyzed by gas chromatography. The liquid product is filtered, the solid component obtained is cleaned with methanol, and 0.08g internal standard solution (dimethyl phthalate is an internal standard, and 1.0g dimethyl phthalate is added to 19.0g n-propanol to obtain 5wt.% internal standard solution) is added to the obtained liquid. Methanol is used to be fixed to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0153] After the reaction, quantitative analysis showed that 31.3 mg g of lignin was converted in the Sn / Al2O3 catalytic system. -1 The selectivity of monophenol products and guaiacol monomer products was 29.6%, and the generation of H2 was not detected.

[0154] Comparative Example 4

[0155] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by a mixed catalyst of Ni / Al2O3 and Sn / Al2O3, wherein the specific operation is as follows:

[0156] The conversion experiment of lignin was carried out in a 50mL stainless steel reactor. First, 0.1g bagasse lignin, 0.1g Ni / Al2O3, 0.1g Sn / Al2O3, 10mL methanol and 10mL water were added to the above-mentioned reactor, and the air in the reactor was replaced with high-purity argon, and then 1.0MPa of H2 was charged. Under mechanical stirring, the reactor was heated to 250°C and maintained for 4h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the solid component obtained was cleaned with methanol, and 0.08g internal standard solution (dimethyl phthalate was an internal standard, and 1.0g dimethyl phthalate was added to 19.0g n-propanol to obtain an internal standard solution of 5wt.%) was added to the obtained liquid. Methanol was used to be settled to 25mL to obtain a liquid product. 1.0 mL of the above mixture was taken out with a syringe and added into a sampling bottle, and the volatile products obtained by hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometer.

[0157] After quantitative analysis, 5.48 mmol H2 was detected after the reaction, and 96.0 mg g -1 The selectivity of monophenol products and guaiacol monomer products was 36.8%.

[0158] It can be seen from Example 1, Comparative Example 2 and Comparative Example 3 that the single metal Ni / Al2O3 and Sn / Al2O3 catalyst systems have lower monophenol yields and lower selectivity for guaiacol monomer products than the Ni-Sn / Al2O3-1 catalyst system. And it can be seen from Comparative Example 4 that the single metal Ni / Al2O3 and Sn / Al2O3 catalysts are simply physically mixed, and the monophenol yield and selectivity for guaiacol monomer products in the mixed system of lignin depolymerization are also lower than those of the Ni-Sn / Al2O3-1 catalyst system, and the selectivity for guaiacol monomer products in all embodiments of the present invention exceeds 40%, which is difficult to achieve in the prior art.

[0159] By comparing Example 1 with Comparative Example 2, it can be found that the introduction of Sn species into the Ni / Al2O3 catalyst can improve the activity of hydrogen production from liquid phase reforming of alcohols, and the hydrogen production is increased from 5.57 mmol to 8.27 mmol. Higher hydrogen production promotes the hydrogenolysis reaction of lignin, thereby obtaining a higher yield of monophenol products (96.9 mg g -1 vs 171.4 mg g -1 ) and higher selectivity for guaiacol monomer products (46.1% vs 34.3%).

[0160] It can be seen from Examples 17 and 18 that the Ni-Sn / Al2O3-1 catalyst of the present invention can also efficiently convert corncob and bamboo lignin, showing good substrate applicability.

[0161] Compared with Chinese invention patent CN112608219B, the present invention uses non-precious metal Ni-based catalysts to achieve efficient depolymerization of lignin to prepare guaiacol monomer products, avoiding the use of precious metals and reducing the cost of catalyst preparation. The present invention uses catalysts to catalyze alcohol reforming to produce hydrogen, providing H2 for lignin depolymerization in situ. Compared with Chinese invention patent application CN115364862A, the present invention uses a urea precipitant method to avoid the phenomenon of excessive local alkali concentration in the mixed alkali method, and further synthesizes a precursor with high crystallinity and uniform distribution of metal ions, thereby promoting the formation of Ni-Sn alloy species.

[0162] Through XRD, TEM and other characterizations of the catalyst, it was found that the Ni-Sn / Al2O3-1 catalyst of the present invention contains both Ni metal and Ni-Sn alloy species. Among them, the Ni-Sn alloy promotes the hydrogen production reaction of alcohol liquid phase reforming, and the Ni metal strengthens the breakage of CO chemical bonds in lignin, thereby improving the depolymerization efficiency of lignin and the yield of guaiacol products. Therefore, the mesoporous structure of the Ni-Sn / Al2O3-1 catalyst of the present invention and the characteristics of the simultaneous presence of Ni-Sn alloy and Ni metal on the surface enhance the depolymerization efficiency of lignin, thereby promoting the generation of guaiacol monomer products.

[0163] The implementation methods of the present invention are not limited to the above-mentioned embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina, characterized in that: The method uses organic soluble lignin as a raw material, a mixture of alcohols and water as a solvent, and an alumina-loaded metal nickel and nickel-tin alloy catalyst prepared by a urea precipitation method. The air in the reactor is replaced by an inert gas and the reactor is pressurized to 1.0-3.0 MPa. The reactor is stirred at a temperature of 210-270° C. for 1-6 hours to highly selectively convert the organic soluble lignin into a compound mainly composed of guaiacol monomer products. The nickel-tin alloy includes Ni4Sn, Ni3Sn, NiSn and Ni3Sn2. Sn accounts for 5.9%-50.6% of the mass of the entire alumina-loaded metal nickel and nickel-tin alloy catalyst.

2. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina according to claim 1, characterized in that: The alumina-loaded metallic nickel and nickel-tin alloy catalysts prepared by the urea precipitation method are prepared by mixing and stirring a urea solution and a mixed metal salt solution, and then undergoing hydrothermal, washing, drying, roasting, and reduction steps; the mixed metal salt solution is obtained by placing nickel salt, tin salt, and aluminum salt in deionized water.

3. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina according to claim 2, characterized in that: The ratio of the amount of nickel salt to the amount of tin salt in the mixed metal salt solution is 1:1 to 10:1, and the ratio of the sum of the amount of nickel salt and the amount of tin salt to the amount of aluminum salt is 6:1 to 3:1; The concentration of urea in the urea solution is 0.5-2.0 mol L -1 ; The hydrothermal condition is to maintain the temperature at 90°C for 12 to 24 hours; The calcination is to heat the dried product in air at 5-10°C min -1 The heating rate is from room temperature to 450-650°C, and sintered at 450-650°C for 2-4h; The reduction is to introduce H2 into the solid product obtained after calcination at 5-10℃min -1 The heating rate is from room temperature to 450-650°C, and the reduction is carried out at 450-650°C for 2-4h.

4. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina according to claim 2, characterized in that: The nickel salt is nickel nitrate; the aluminum salt is aluminum nitrate; and the tin salt is tin chloride; The concentration of the mixed metal salt solution A is 0.5 to 1.0 mol L -1 ; The washing comprises washing the slurry with deionized water until the pH value is 7.0; The drying is carried out at 100-110°C.

5. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina according to claim 1, characterized in that: The pores of the alumina-supported metal nickel and nickel-tin alloy catalyst are mainly mesopores, and the pore diameters are concentrated in the range of 4 to 20 nm; Ni accounts for 25.2% to 70.6% of the mass of the entire alumina-supported metallic nickel and nickel-tin alloy catalyst, Al accounts for 7.0% to 9.6%, and the remainder is the mass of O.

6. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina according to claim 1, characterized in that: The mass ratio of the alumina-supported metal nickel and nickel-tin alloy catalyst to lignin is 1:1 to 1:

2.

7. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina according to claim 1, characterized in that: The lignin is derived from agricultural and forestry wastes, which include bagasse, corn cobs or bamboo.

8. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported metallic nickel and nickel-tin alloy according to claim 1, characterized in that: The alcohol substance is one or more of methanol, ethanol and isopropanol; the volume ratio of the alcohol substance to water in the mixture of the alcohol substance and water is 1:19 to 19:

1.

9. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina according to claim 1, characterized in that: The inert gas is argon or nitrogen; the reactor is a batch reactor; the stirring speed is 600-800 r min -1 .

10. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by nickel and nickel-tin alloy supported by alumina according to claim 1, characterized in that: The guaiacol monomer products are mainly 4-ethylguaiacol and 4-propylguaiacol.

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