Method for preparing 2-methyltetrahydrofuran by taking furfural as raw material

Abstract

The invention relates to a method for preparing 2-methyltetrahydrofuran by taking furfural as a raw material. The method comprises the following steps: filling furfural and isopropanol into a reaction kettle loaded with a nanoscale bimetallic catalyst, introducing hydrogen into the reaction kettle, and reacting for 3-5 hours at the temperature of 160-190 DEG C and the hydrogen pressure of 0.5-1.3 MPa; the 2-methyl tetrahydrofuran is obtained; the catalyst comprises an active metal M and a carrier, the carrier is SiO2; the active metal M is Ni and Cu; in the preparation of the catalyst, the nanoscale catalyst is continuously prepared by using a high-pressure constant-flux pump and a membrane dispersion microreactor, so that the controllable nucleation and growth process of a metal salt solution and a precipitant solution is rapidly completed, the continuous preparation of the nanoscale catalyst is realized, and the preparation time of the catalyst is greatly shortened. According to the method, less three wastes are generated, the cost is low, the conversion rate of furfural can reach 100%, and green and sustainable production of 2-methyltetrahydrofuran is realized.

Description

Technical Field

[0001] This invention relates to a nanoscale catalyst for the hydrogenation of furfural to prepare 2-methyltetrahydrofuran, and particularly to a method and catalyst system for the hydrogenation of furfural to prepare 2-methyltetrahydrofuran using a multi-active component catalyst. Background Technology

[0002] The efficient catalytic conversion of biomass resources is a key technological pathway to reduce dependence on fossil fuels and build a low-carbon circular economy. Currently, various platform molecules, such as lactic acid, isosorbide, and furfural, can be efficiently obtained from biomass. These can replace fossil feedstocks for the production of fine chemicals and biofuels. Furfural can be converted into valuable downstream chemicals, such as furfuryl alcohol, tetrahydrofurfural, 2-methylfuran, furoic acid, 2-methyltetrahydrofuran, and other products, with the conversion of furfural to 2-methyltetrahydrofuran showing great promise.

[0003] 2-Methyltetrahydrofuran not only retains some characteristics of the furan ring, but also has higher stability and a wider range of applications due to its saturated structure, such as as a green solvent, fuel additive, and monomer for polymer materials. For example, Mo Yong's team (Fine Chemicals, 2013, 30(07):821-824.) proposed a sol-gel method to prepare an ultrafine mixed catalyst of Ni:Cu=1:1 for the direct hydrogenation of furfural to 2-methyltetrahydrofuran. The catalyst was reacted under reaction conditions of 8 MPa and 180℃, and the yield of 2-methyltetrahydrofuran was 64.5%. This catalyst has the problems of complex preparation and high equipment requirements. Yang Bin's team (CN117753472A) disclosed a method for preparing a catalyst for the production of 2-methyltetrahydrofuran. A co-impregnation method was used to impregnate palladium salt and copper salt on molecular sieves, which were then calcined in a muffle furnace before use. The yield of 2-methyltetrahydrofuran was 83.1%. The reaction temperature of this catalyst was 220℃. This catalyst uses precious metals as raw materials, which is costly. The above solutions or catalytic systems have disadvantages such as high catalyst costs and demanding reaction conditions.

[0004] Therefore, developing more efficient, stable, and low-cost non-precious metal catalysts, optimizing reaction conditions and processes, improving reaction selectivity and yield, and achieving the efficient preparation of 2-methyltetrahydrofuran from furfural via catalytic hydrogenation has significant application value. Summary of the Invention

[0005] The purpose of this invention is to overcome the limitations of existing technologies and propose a method for preparing 2-methyltetrahydrofuran from furfural. This method selects a Ni / Cu dual-active catalyst to catalyze the one-step hydrogenation and deoxygenation of furfural to prepare 2-methyltetrahydrofuran. In catalyst preparation, a nanoscale catalyst is continuously prepared using a high-pressure horizontal pump and a membrane dispersion microreactor, enabling rapid and controllable nucleation and growth of the metal salt solution and precipitant solution. This achieves continuous preparation of the nanoscale catalyst, significantly shortening the catalyst preparation time. This invention generates less waste, has low cost, and the catalyst used exhibits excellent catalytic activity and stability, achieving a furfural conversion rate of up to 100%, thus realizing the green and sustainable production of 2-methyltetrahydrofuran.

[0006] The technical solution of this invention is as follows: A method for preparing 2-methyltetrahydrofuran from furfural as a raw material, the method comprising the following steps: Furfural and isopropanol were loaded into a reactor containing a nanoscale bimetallic catalyst. The air in the reactor was replaced with hydrogen three times. After replacement, the reactor was sealed. After sealing, hydrogen was introduced into the reactor and reacted at 160 ℃-190 ℃ and hydrogen pressure of 0.5-1.3 MPa for 3-5 h to obtain 2-methyltetrahydrofuran. The mass ratio of furfural to catalyst is 4-10:1; the solvent is isopropanol, and the mass ratio of isopropanol to furfural is 10-25:1. The catalyst comprises an active metal M and a support; the support is SiO2; the active metal M is Ni and Cu; the molar ratio of Ni / Cu is 4-19; and the molar ratio of SiO2 to the metal is 0.3-0.7. The catalyst has a particle size of 3.5-10 nm; A continuous preparation method for a nanoscale bimetallic catalyst includes the following steps: At a constant temperature of 50-80 ℃, metal salt solution A and Na2CO3 solution B are pumped to the first membrane dispersion microreactor using a high-pressure horizontal flow pump to obtain a mixed solution. The outflowing turbid liquid is connected to the left port of a three-way valve through a pipeline. Na2SiO3 solution C is pumped from the right port of the three-way valve using a high-pressure horizontal flow pump. After the two are mixed, they flow out from the upper port of the three-way valve and are connected to the upper port of the second membrane dispersion microreactor. Then, H2SO4 solution D is pumped to the left port of the second membrane dispersion microreactor using a high-pressure horizontal flow pump. After mixing in the membrane dispersion microreactor, the pH of the outflowing turbid liquid is adjusted to 7-9. After the turbid liquid is held in a residence tube for 10-30 min, the suspension in the reaction system is collected and treated: centrifuged, washed, dried at 80-100 ℃ for 3-5 h, and then reduced in a tube furnace at 400-600 ℃ for 3-5 h under a hydrogen atmosphere to obtain the catalyst. Among them, the metal salts are nickel salts and copper salts, and the molar ratio of Ni / Cu is 4-19; The nickel salt is specifically Ni(NO3)2·6H2O; the copper salt is specifically Cu(NO3)2·3H2O; The ratio of the molar amount of Na2CO3 to the sum of the molar amounts of the metal in the metal salt solution is 2:1. The ratio of the molar amount of sodium silicate to the sum of the molar amounts of the metal in the metal salt solution is 0.3-0.7; The concentration of Na2CO3 solution B is 0.3-0.6 mol / L; The flow rate of metal salt solution A is 2.5-12.5 ml / min, the flow rate of Na2CO3 solution B is 1:1 with that of metal salt solution A; the flow rate of Na2SiO3 solution C is 5 ml / min, and the flow rate of H2SO4 solution D is 2.5-12.5 ml / min. The concentration of H2SO4 solution D in the reaction solution is 0.06-0.14 mol / L.

[0007] The essential features of this invention are: This invention utilizes furfural as a raw material and isopropanol as a solvent to efficiently prepare 2-methyltetrahydrofuran via a hydrodeoxygenation reaction using an inexpensive, nanoscale, non-precious metal catalyst. The selected catalyst possesses the following characteristics: The nano-scale Ni-Cu catalyst used in this invention has the advantage of Cu in dispersing catalyst particles, avoiding the severe agglomeration phenomenon of single metal catalysts. In addition, its SiO2 shell has a good anchoring effect, which can disperse and protect the core active components, avoid the phenomenon of high-temperature sintering of active components, and achieve the best catalytic performance.

[0008] The beneficial effects of this invention are as follows: The hydrodeoxygenation reaction of this invention is a low-pressure reaction, which does not require sophisticated reaction equipment and improves the economic feasibility of the reaction. The catalytic process is pollution-free and produces minimal waste. The conversion rate of furfural can reach 100%, and the selectivity for 2-methyltetrahydrofuran is 68%.

[0009] This invention employs a high-pressure horizontal flow pump and a micro-turbulence reactor for the continuous preparation of nanoscale metal catalysts. The prepared catalysts have smaller particle sizes, larger specific surface areas, and better reaction performance. The entire process can be operated continuously with a high degree of automation, shortening the catalyst preparation time. Furthermore, all raw materials are inexpensive, making it suitable for industrial production. Attached Figure Description

[0010] Figure 1 TEM images of the catalysts obtained in Examples 6, 7 and 8; Figure 2The pore size distribution diagrams are for the (9Ni-Cu)-SiO2-0.3, (9Ni-Cu)-SiO2-0.5, and (9Ni-Cu)-SiO2-0.7 catalysts obtained in Examples 6, 7, and 8.

[0011] Figure 3 This is a TEM image of the core-shell structure of the catalyst obtained in Example 7. Detailed Implementation

[0012] The synthetic route of this invention is shown in the reaction formula below:

[0013] The technical features of the present invention are further illustrated below through examples: The membrane dispersion microreactor involved in this invention specifically comprises a stainless steel microfiltration membrane with a pore size of 0.5-5 μm, a diameter of 6.5-100 mm, and a thickness of 1.3-20 mm; the residence tube is made of polytetrafluoroethylene with an inner diameter of 1.5-2.5 mm and a length of 0.5-25 m. However, it is not limited to these.

[0014] The catalyst is represented by (aNi-bCu)-SiO2-z, where Ni and Cu are the active metal components of the catalyst, a / b is the molar ratio of the active metal components, and z represents the molar ratio of silicon to metal M in the catalyst. The molar ratio of Ni / Cu is 4-19.

[0015] Example 1: Preparation of nanoscale catalyst (19Ni-Cu)-SiO2-0.4 Prepare metal solution A (0.2 mol / L) by adding 11.05 g Ni(NO3)2·6H2O (0.038 mol) and 0.4832 g Cu(NO3)2·3H2O (0.002 mol) to 200 g water. Prepare precipitant solution B (0.4 mol / L) by adding 8.48 g Na2CO3 (0.08 mol) to 200 g water. Prepare solution C (0.08 mol / L) by adding 4.55 g Na2SiO3·9H2O (0.016 mol) to 200 g water. Prepare solution D (0.065 mol / L) by adding 1.274 g (0.013 mol) concentrated sulfuric acid to 200 g water. Metal salt solution A and Na2CO3 solution B were pumped separately at 5 ml / min using a high-pressure horizontal flow pump and mixed in a membrane dispersion microreactor (at a constant temperature of 60 °C). The outflowing turbid liquid was then piped to the left port of a tee. Na2SiO3 solution C was pumped from the right port of the tee at 5 ml / min using a high-pressure horizontal flow pump. After mixing, the two solutions flowed out from the top port of the tee and into the top port of the second membrane dispersion microreactor. H2SO4 solution D was then pumped to the left port of the second membrane dispersion microreactor using a high-pressure horizontal flow pump at 5 ml / min. After mixing in the membrane dispersion microreactor, the pH of the outflowing turbid liquid was adjusted to 8, and the flow time in the residence tube was 20 min. The suspension in the reaction system was then collected and treated.

[0016] The catalyst was separated from the mixed phase by centrifugation. The mixture was washed with deionized water until the pH reached 7, and then washed twice with anhydrous ethanol. Finally, the washed catalyst was placed in a constant temperature drying oven and dried at 80 °C for 4 h, followed by reduction in a tube furnace at 500 °C for 3 h under a hydrogen atmosphere to obtain the catalyst (19Ni-Cu)-SiO2-0.4.

[0017] The catalyst has a particle size of 6.5 nm.

[0018] The catalyst is represented by (aM1-bM2)-SiO2-z, where M1 and M2 represent the active metal components, a / b is the molar ratio of the active metal components, and z represents the molar ratio of silicon to metal M in the catalyst.

[0019] In the membrane dispersion microreactor, the stainless steel microfiltration membrane has a pore size of 1 μm and a diameter of 7.5 mm.

[0020] Example 2: Preparation of nanoscale catalyst (10Ni-Cu)-SiO2-0.4 Metal solution A (0.2 mol / L) was prepared by adding 10.58 g Ni(NO3)2·6H2O (0.0364 mol) and 0.8794 g Cu(NO3)2·3H2O (0.00364 mol) to 200 g of water. Precipitant solution B (0.4 mol / L) was prepared by adding 8.48 g Na2CO3 (0.08 mol) to 200 g of water. Solution C (0.08 mol / L) was prepared by adding 4.55 g Na2SiO3·9H2O (0.016 mol) to 200 g of water. Solution D (0.065 mol / L) was prepared by adding 1.274 g (0.013 mol) concentrated sulfuric acid to 200 g of water. Subsequent steps were the same as in Example 1 to obtain catalyst (10Ni-Cu)-SiO2-0.4.

[0021] Example 3: Preparation of nanoscale catalyst (9Ni-Cu)-SiO2-0.4 Metal solution A (0.2 mol / L) was prepared by adding 10.468 g Ni(NO3)2·6H2O (0.036 mol) and 0.9664 g Cu(NO3)2·3H2O (0.004 mol) to 200 g water. Precipitant solution B (0.4 mol / L) was prepared by adding 8.48 g Na2CO3 (0.08 mol) to 200 g water. Solution C (0.08 mol / L) was prepared by adding 4.55 g Na2SiO3·9H2O (0.016 mol) to 200 g water. Solution D (0.065 mol / L) was prepared by adding 1.274 g concentrated sulfuric acid to 200 g water. Subsequent steps were the same as in Example 1 to obtain catalyst (9Ni-Cu)-SiO2-0.4.

[0022] Example 4: Preparation of nanoscale catalyst (17Ni-3Cu)-SiO2-0.4 Metal solution A (0.2 mol / L) was prepared by adding 9.887 g Ni(NO3)2·6H2O (0.034 mol) and 1.450 g Cu(NO3)2·3H2O (0.006 mol) to 200 g water. Precipitant solution B (0.4 mol / L) was prepared by adding 8.48 g Na2CO3 (0.08 mol) to 200 g water. Solution C (0.08 mol / L) was prepared by adding 4.55 g Na2SiO3·9H2O (0.016 mol) to 200 g water. Solution D (0.065 mol / L) was prepared by adding 1.274 g (0.013 mol) concentrated sulfuric acid to 200 g water. Subsequent steps were the same as in Example 1 to obtain catalyst (17Ni-3Cu)-SiO2-0.4.

[0023] Example 5: Preparation of nanoscale catalyst (4Ni-Cu)-SiO2-0.4 Metal solution A (0.2 mol / L) was prepared by adding 9.305 g Ni(NO3)2·6H2O (0.032 mol) and 1.933 g Cu(NO3)2·3H2O (0.008 mol) to 200 g of water. Precipitant solution B (0.4 mol / L) was prepared by adding 8.48 g Na2CO3 (0.08 mol) to 200 g of water. Solution C (0.08 mol / L) was prepared by adding 4.55 g Na2SiO3·9H2O (0.016 mol) to 200 g of water. Solution D (0.065 mol / L) was prepared by adding 1.274 g (0.013 mol) concentrated sulfuric acid to 200 g of water. Subsequent steps were the same as in Example 1 to obtain catalyst (4Ni-Cu)-SiO2-0.4.

[0024] Example 6: Preparation of nanoscale catalyst (9Ni-Cu)-SiO2-0.3 Metal solution A (0.2 mol / L) was prepared by adding 10.468 g Ni(NO3)2·6H2O (0.036 mol) and 0.9664 g Cu(NO3)2·3H2O (0.004 mol) to 200 g water. Precipitant solution B (0.4 mol / L) was prepared by adding 8.48 g Na2CO3 (0.08 mol) to 200 g water. Solution C (0.06 mol / L) was prepared by adding 3.41 g Na2SiO3·9H2O (0.012 mol) to 200 g water. Solution D (0.06 mol / L) was prepared by adding 1.176 g (0.012 mol) concentrated sulfuric acid to 200 g water. Subsequent steps were the same as in Example 1 to obtain catalyst (9Ni-Cu)-SiO2-0.3.

[0025] Example 7: Preparation of nanoscale catalyst (9Ni-Cu)-SiO2-0.5 Metal solution A (0.2 mol / L) was prepared by adding 10.468 g Ni(NO3)2·6H2O (0.036 mol) and 0.9664 g Cu(NO3)2·3H2O (0.004 mol) to 200 g of water. Precipitant solution B (0.4 mol / L) was prepared by adding 8.48 g Na2CO3 (0.08 mol) to 200 g of water. Solution C (0.1 mol / L) was prepared by adding 5.684 g Na2SiO3·9H2O (0.02 mol) to 200 g of water. Solution D (0.07 mol / L) was prepared by adding 1.372 g (0.014 mol) concentrated sulfuric acid to 200 g of water. Subsequent steps were the same as in Example 1 to obtain catalyst (9Ni-Cu)-SiO2-0.5.

[0026] Example 8: Preparation of nanoscale catalyst (9Ni-Cu)-SiO2-0.7 Metal solution A (0.2 mol / L) was prepared by adding 10.468 g Ni(NO3)2·6H2O (0.036 mol) and 0.9664 g Cu(NO3)2·3H2O (0.004 mol) to 200 g water. Precipitant solution B (0.4 mol / L) was prepared by adding 8.48 g Na2CO3 (0.08 mol) to 200 g water. Solution C (0.14 mol / L) was prepared by adding 7.958 g Na2SiO3·9H2O (0.028 mol) to 200 g water. Solution D (0.12 mol / L) was prepared by adding 2.352 g (0.024 mol) concentrated sulfuric acid to 200 g water. Subsequent steps were the same as in Example 1 to obtain catalyst (9Ni-Cu)-SiO2-0.7.

[0027] Example 9: Preparation of nanoscale catalyst (9Ni-Cu)-SiO2-0.5 (precipitation pH=7) To prepare metal solution A (0.2 mol / L), add 10.468 g Ni(NO3)2·6H2O (0.036 mol) and 0.9664 g Cu(NO3)2·3H2O (0.004 mol) to 200 g of water. To prepare precipitant solution B (0.4 mol / L), add 8.48 g Na2CO3 (0.08 mol) to 200 g of water. To prepare precipitant solution C (0.1 mol / L), add 5.684 g Na2SiO3·9H2O (0.02 mol) to 200 g of water. To prepare solution D (0.075 mol / L), add 1.470 g (0.014 mol) concentrated sulfuric acid to 200 g of water. Metal salt solution A and Na₂CO₃ solution B were pumped at 5 ml / min using a high-pressure horizontal flow pump and mixed in a membrane dispersion microreactor (at a constant temperature of 60 °C). The outflowing turbid liquid was then piped to the left port of a tee. Na₂SiO₃ solution C was pumped at 5 ml / min from the right port of the tee. After mixing, the two solutions flowed out from the top port of the tee and into the top port of the second membrane dispersion microreactor. H₂SO₄ solution D was then pumped at 5 ml / min to the left port of the second membrane dispersion microreactor. After mixing in the membrane dispersion microreactor, the pH of the outflowing turbid liquid was adjusted to 7, and the suspension in the reaction system was collected. The catalyst was separated from the mixed phase by centrifugation. The mixture was washed 15 times with deionized water, and the catalyst was washed twice with anhydrous ethanol. Finally, the washed catalyst was placed in a constant temperature drying oven and dried at 80 °C for 4 h. Then, it was reduced in a tube furnace at 500 °C for 3 h under a hydrogen atmosphere to obtain the catalyst (19Ni-Cu)-SiO2-0.4 (pH=7).

[0028] Example 10: Preparation of nanoscale catalyst (9Ni-Cu)-SiO2-0.5 (precipitation pH=9) To prepare metal solution A (0.2 mol / L), add 10.468 g Ni(NO3)2·6H2O (0.036 mol) and 0.9664 g Cu(NO3)2·3H2O (0.004 mol) to 200 g water. To prepare precipitant solution B (0.4 mol / L), add 8.48 g Na2CO3 (0.08 mol) to 200 g water. To prepare solution C (0.1 mol / L), add 5.684 g Na2SiO3·9H2O (0.02 mol) to 200 g water. To prepare solution D (0.06 mol / L), add 1.176 g (0.012 mol) concentrated sulfuric acid to 200 g water. Metal salt solution A and Na₂CO₃ solution B were pumped at 5 ml / min using a high-pressure horizontal flow pump and mixed in a membrane dispersion microreactor (at a constant temperature of 60 °C). The outflowing turbid liquid was then piped to the left port of a tee. Na₂SiO₃ solution C was pumped at 5 ml / min from the right port of the tee. After mixing, the two solutions flowed out from the top port of the tee and into the top port of the second membrane dispersion microreactor. H₂SO₄ solution D was then pumped at 5 ml / min to the left port of the second membrane dispersion microreactor. After mixing in the membrane dispersion microreactor, the pH of the outflowing turbid liquid was adjusted to 9, and the suspension in the reaction system was collected. The catalyst was separated from the mixed phase by centrifugation. The mixture was washed with deionized water to achieve a pH of 7, and the catalyst was washed twice with anhydrous ethanol. Finally, the washed catalyst was placed in a constant temperature drying oven and dried at 80 °C for 4 h. Then, it was reduced in a tube furnace at 500 °C for 3 h under a hydrogen atmosphere to obtain the catalyst (19Ni-Cu)-SiO2-0.4 (pH=9).

[0029] Example 11: Preparation of nanoscale catalyst (9Ni-Cu)-SiO2-0.5 (reduction at 400 °C) To prepare metal solution A (0.2 mol / L), add 10.468 g Ni(NO3)2·6H2O (0.036 mol) and 0.9664 g Cu(NO3)2·3H2O (0.004 mol) to 200 g water. To prepare precipitant solution B (0.4 mol / L), add 8.48 g Na2CO3 (0.08 mol) to 200 g water. To prepare precipitant solution C (0.1 mol / L), add 5.684 g Na2SiO3·9H2O (0.02 mol) to 200 g water. To prepare solution D (0.07 mol / L), add 1.372 g (0.014 mol) concentrated sulfuric acid to 200 g water. Metal salt solution A and Na₂CO₃ solution B were pumped at 5 ml / min using a high-pressure horizontal flow pump and mixed in a membrane dispersion microreactor (at a constant temperature of 60 °C). The outflowing turbid liquid was then piped to the left port of a tee. Na₂SiO₃ solution C was pumped at 5 ml / min from the right port of the tee. After mixing, the two solutions flowed out from the top port of the tee and into the top port of the second membrane dispersion microreactor. H₂SO₄ solution D was then pumped at 5 ml / min to the left port of the second membrane dispersion microreactor. After mixing in the membrane dispersion microreactor, the pH of the outflowing turbid liquid was adjusted to 8, and the suspension in the reaction system was collected. The catalyst was separated from the mixed phase by centrifugation. The mixture was washed 15 times with deionized water, and the catalyst was washed twice with anhydrous ethanol. Finally, the washed catalyst was placed in a constant temperature drying oven and dried at 80 °C for 4 h. Then, it was reduced in a tube furnace at 500 °C for 3 h under a hydrogen atmosphere to obtain the catalyst (19Ni-Cu)-SiO2-0.4 (pH=8).

[0030] Example 12: Preparation of nanoscale catalyst (9Ni-Cu)-SiO2-0.5 (reduction at 600 °C) To prepare metal solution A (0.2 mol / L), add 10.468 g Ni(NO3)2·6H2O (0.036 mol) and 0.967 g Cu(NO3)2·3H2O (0.004 mol) to 200 g water. To prepare precipitant solution B (0.4 mol / L), add 8.48 g Na2CO3 (0.08 mol) to 200 g water. To prepare precipitant solution C (0.1 mol / L), add 5.684 g Na2SiO3·9H2O (0.02 mol) to 200 g water. To prepare solution D (0.07 mol / L), add 1.372 g (0.014 mol) concentrated sulfuric acid to 200 g water. Metal salt solution A and Na₂CO₃ solution B were pumped at 5 ml / min using a high-pressure horizontal flow pump and mixed in a membrane dispersion microreactor (at a constant temperature of 60 °C). The outflowing turbid liquid was then piped to the left port of a tee. Na₂SiO₃ solution C was pumped at 5 ml / min from the right port of the tee. After mixing, the two solutions flowed out from the top port of the tee and into the top port of the second membrane dispersion microreactor. H₂SO₄ solution D was then pumped at 5 ml / min to the left port of the second membrane dispersion microreactor. After mixing in the membrane dispersion microreactor, the pH of the outflowing turbid liquid was adjusted to 8, and the suspension in the reaction system was collected. The catalyst was separated from the mixed phase by centrifugation. The mixture was washed 15 times with deionized water, and the catalyst was washed twice with anhydrous ethanol. Finally, the washed catalyst was placed in a constant temperature drying oven and dried at 80 °C for 4 h. Then, it was reduced in a tube furnace at 500 °C for 3 h under a hydrogen atmosphere to obtain the catalyst (19Ni-Cu)-SiO2-0.4 (pH=8).

[0031] Example 13: Furfural is synthesized into 2-methyltetrahydrofuran via hydrogenation and deoxygenation. The reaction was carried out in a 50 ml stainless steel reactor, with the addition of (19Ni-Cu)-SiO2-0.4 catalyst (100 mg), furfural (0.5 g), and isopropanol (7.5 g) obtained in Example 1. Before the reaction, the reactor was purged three times with H2 to replace residual air. Hydrogenation was then carried out at a constant H2 pressure (1 MPa) and temperature (190 °C) with a stirring rate of 1500 rpm. After 5 h of reaction, the liquid product was separated from the catalyst and further analyzed by gas chromatography with internal standard. The conversion rate of furfural was 100%, the selectivity for 2-methyltetrahydrofuran was 35%, and the selectivity for tetrahydrofurfuryl alcohol was 12%.

[0032] Other specific catalyst implementation examples are shown in the table below:

[0033] The catalysts of Examples 6, 7, and 8 were characterized by TEM and analyzed by N2 adsorption-desorption. Figure 1 , Figure 2 And Table 2: Table 2. Pore diameter and specific surface area of ​​Examples 6, 7, and 8

[0034] pass Figure 1 ( Figure 1 The image on the left is a TEM image of the (9Ni-Cu)-SiO2-0.3 catalyst obtained in Example 6. Figure 1 The image in the middle is a TEM image of the (9Ni-Cu)-SiO2-0.5 catalyst obtained in Example 7. Figure 1 The image on the right shows the (9Ni-Cu)-SiO2-0.7 catalyst obtained in Example 8. Combined with the results of previous catalyst performance tests, it can be seen that as the SiO2 content gradually increases, the metal particle dispersion improves, and the catalyst shell thickness gradually increases. However, an excessively thick SiO2 shell hinders sufficient contact between the active component and the reactants, thus impeding the reaction. This was achieved through N2 adsorption-desorption testing. Figure 2 And Table 2, by Figure 2 As shown in Table 2, with the ratio of sodium silicate to the metal active component increasing from 0.3 to 0.7 (molar ratio), the specific surface area of ​​the catalyst tends to increase, while the pore size tends to decrease. The specific surface area increases from 205.47 m². 2 / g increased to 328.59m 2 / g, the average pore size decreased from 8.58nm to 7.60nm; a larger specific surface area means more active sites come into contact with the reactants, but the size of the pores also affects the mass transfer process of the reaction. Figure 3 The image shows a TEM image of the (9Ni-Cu)-SiO2-0.5 core-shell structure obtained in Example 7. The image shows that the SiO2 shell is uniformly coated on the surface of the metal particles, which can disperse and protect the core active components, avoid the phenomenon of high-temperature sintering of the active components, and achieve the best catalytic performance. Therefore, Example 7 was selected as the optimal catalyst.

[0035] Matters not covered in this invention are common knowledge.

Claims

1. A method for preparing 2-methyltetrahydrofuran from furfural, characterized in that, The method includes the following steps: Furfural and isopropanol were loaded into a reactor containing a nanoscale bimetallic catalyst. The air in the reactor was replaced with hydrogen three times. After replacement, the reactor was sealed. After sealing, hydrogen was introduced into the reactor and reacted at 160 ℃-190 ℃ and hydrogen pressure of 0.5-1.3 MPa for 3-5 h to obtain 2-methyltetrahydrofuran. The mass ratio of furfural to catalyst is 4-10:1; the solvent is isopropanol, and the mass ratio of isopropanol to furfural is 10-25:

1. The catalyst comprises an active metal M and a support; the support is SiO2; the active metal M is Ni and Cu; the molar ratio of Ni / Cu is 4-19:1; and the molar ratio of SiO2 to the metal is 0.3-0.7:

1.

2. The method for preparing 2-methyltetrahydrofuran from furfural as described in claim 1, characterized in that, The particle size of the catalyst is 3.5-10 nm.

3. The method for preparing 2-methyltetrahydrofuran from furfural as described in claim 1, characterized in that, The nanoscale bimetallic catalyst was prepared continuously using a high-pressure horizontal flow pump and a membrane dispersion microreactor.

4. A continuous preparation method for a nanoscale bimetallic catalyst, characterized in that, Includes the following steps: At a constant temperature of 50-80 ℃, metal salt solution A and Na2CO3 solution B are pumped to the first membrane dispersion microreactor using a high-pressure horizontal flow pump to obtain a mixed solution. The outflowing turbid liquid is connected to the left port of a tee through a pipeline. Na2SiO3 solution C is pumped from the right port of the tee using a high-pressure horizontal flow pump. After the two are mixed, they flow out from the upper port of the tee and are connected to the upper port of the second membrane dispersion microreactor. Then, H2SO4 solution D is pumped to the left port of the second membrane dispersion microreactor using a high-pressure horizontal flow pump. After mixing in the membrane dispersion microreactor, the pH of the outflowing turbid liquid is adjusted to 7-9. After the turbid liquid is held in a residence tube for 10-30 min, the suspension in the reaction system is collected and treated: centrifuged, washed, dried at 80-100 ℃ for 3-5 h, and then reduced in a tube furnace at 400-600 ℃ for 3-5 h under a hydrogen atmosphere to obtain the catalyst. Among them, the metal salts are nickel salts and copper salts, and the molar ratio of Ni / Cu is 4-19; The nickel salt is specifically Ni(NO3)2·6H2O; the copper salt is specifically Cu(NO3)2·3H2O; The ratio of the molar amount of Na2CO3 to the sum of the molar amounts of the metal in the metal salt solution is 2:

1. The ratio of the molar amount of sodium silicate to the sum of the molar amounts of the metal in the metal salt solution is 0.3-0.7; The concentration of Na2CO3 solution B is 0.3-0.6 mol / L.

5. The continuous preparation method of the nanoscale bimetallic catalyst as described in claim 4, characterized in that, The flow rate of metal salt solution A is 2.5-12.5 ml / min, the flow rate of Na2CO3 solution B is 1:1 with that of metal salt solution A, the flow rate of Na2SiO3 solution C is 5 ml / min, and the flow rate of H2SO4 solution D is 2.5-12.5 ml / min.

6. The continuous preparation method of the nanoscale bimetallic catalyst as described in claim 4, characterized in that, The concentration of H2SO4 solution D in the reaction solution is 0.06-0.14 mol / L.

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