Method for synthesizing 2-methyltetrahydrofuran by using nickel / aluminum oxide catalyst

Abstract

The invention relates to a method for synthesizing 2-methyltetrahydrofuran, in particular to a method for synthesizing 2-methyltetrahydrofuran by using a nickel / aluminum oxide catalyst, which comprises the following steps: weighing Ni salt and Al salt, and adding deionized water to prepare a metal salt solution; mixing the salt solution and the alkaline solution, adding the mixture into a beaker containing distilled water in a parallel flow manner, and controlling the pH value to be 6-8; stirring and aging at 40 DEG C for 4 hours; the Ni / Al2O3 catalyst is obtained; the Ni / Al2O3 catalyst is applied to a 2-MF gas phase hydrogenation reaction, H2 / N2 mixed gas is used for reduction, the catalyst after reduction starts to react, the initial H2 / 2-MF ratio is 0.2-1, after feeding reaction is performed for 10-30 hours, then the H2 / 2-MF ratio is increased to 4-10, and gas phase catalytic hydrogenation reaction is performed. The mild gas-phase hydrogenation reaction conditions are adopted, and the catalyst is high in activity, high in selectivity and good in stability. The catalyst is low in cost, resources are saved, and the gas phase hydrogenation process is high in safety, so that better economic benefits are achieved.

Description

Technical Field

[0001] The invention relates to a method for synthesizing 2-methyltetrahydrofuran, in particular to a method for synthesizing 2-methyltetrahydrofuran using a nickel / aluminum oxide catalyst. Background Art

[0002] Biomass resources are widely distributed, environmentally friendly, and abundant in reserves. They are currently one of the most promising sources of organic chemical raw materials that can replace fossil resources. 2-Methylfuran and 2-methyltetrahydrofuran are both downstream derivatives of the biomass platform compound furfural and have a wide range of uses.

[0003] Methyltetrahydrofuran (hereinafter referred to as 2-MTHF) is an excellent organic solvent and organic intermediate with a moderate boiling point, low solubility in water, and easy separation from water. As an organic solvent, it can be used as a reagent for Grignard reaction, as a substitute for organic solvents such as halogenated hydrocarbons and benzene, as a reaction reagent or extractant for organic synthesis; it can also be used as a solvent for chemical raw materials such as rubber, cellulose, and resin. As an organic intermediate, it can also be used as a synthetic raw material for thiamine, chloroquine phosphate, and anti-hemorrhoid drug primaquine phosphate in organic synthesis. In addition, as a second-generation biomass fuel, it can also be miscible with gasoline in any ratio and can be used as a gasoline additive to replace part of gasoline. Studies have shown that 2-MTHF as an additive in gasoline, with a proportion of 60% in gasoline, will not affect the performance of the engine, and the fuel consumption will not increase.

[0004] Some of the technologies for synthesizing 2-methyltetrahydrofuran by catalytic hydrogenation of 2-methylfuran that have been reported are listed below. Chinese patent CN101492433B, "A green synthesis method of 2-methyltetrahydrofuran", in a reactor, 2-methylfuran and a composite catalyst are subjected to liquid phase hydrogenation reaction at 50-100°C and 1.0-4.0MPa until hydrogen absorption is complete, and the reaction liquid is separated to obtain 2-methyltetrahydrofuran. The composite catalyst used is a noble metal ruthenium and a non-noble metal zinc, copper or iron simultaneously supported on an activated carbon carrier. This invention has the advantages of low reaction pressure and moderate temperature, simple operation and high yield, but the noble metal ruthenium is used in the catalyst, the catalyst cost is relatively high, and the reaction process adopts a liquid phase hydrogenation process, the catalyst needs to be separated and recycled, the separation cost is high and there is catalyst loss.

[0005] Chinese patent CN103977803B, "A method for preparing 2-methyltetrahydrofuran by gas phase hydrogenation of 2-methylfuran", discloses a catalyst NiO / SiO2 catalyst; wherein the mass percentage of NiO is 20%-40%, the mass percentage of carrier SiO2 is 60%-80%, and the mass percentage of alkali metal or alkaline earth metal oxide additive is 2%-10%; the reaction temperature is about 100-180 ° C, the pressure is less than 2 Mpa, the 2-methylfuran conversion rate is 100%, the selectivity of 2-methyltetrahydrofuran is above 95%, and the by-products are relatively small, mainly 2-pentanol.

[0006] The literature (Mo Yong, Journal of Central South Forestry University, 2013, 33(6) 140-144) reported a Ru.Zn.Cu / SiO2 composite catalyst for the liquid phase hydrogenation of 2-methylfuran to 2-MTHF. When the Ru content was 3%, the reaction temperature was 120℃, the reaction pressure was 4MPa, and the speed was 1200 r / min, the 2-MF conversion rate could reach 100% and the selectivity of 2-MTHF could reach 87.6% under the action of the Ru.Zn.Cu / SiO2 composite catalyst. The precious metal ruthenium was used in the catalyst, and the catalyst cost was relatively high. The reaction process adopted the liquid phase hydrogenation process, and the selectivity of 2-MTHF was not high enough.

[0007] The literature (Li Zengjie, Journal of Fuel Chemistry, 2018, 46 (1) 54-58) reported a Ni / Al2O3 catalyst prepared by an impregnation method for hydrogenation of 2-MF to 2-MTHF. It was found that when the reaction pressure was 3 MPa, the reaction temperature was 150 ℃, and the mechanical stirring rate was 1000 r / min, the Ni / Al2O3 catalyzed hydrogenation of 2-methylfuran to 2-methyltetrahydrofuran had a high selectivity. When the NiO loading was 25%, the selectivity of 2-methyltetrahydrofuran was as high as 97.1%, and the conversion rate of 2-methylfuran reached 99.4%. Summary of the invention

[0008] The purpose of the present invention is to provide a method for synthesizing 2-methyltetrahydrofuran using a nickel / alumina catalyst, the method is a method for preparing 2-methyltetrahydrofuran (2-MTHF) by gas phase hydrogenation of 2-methylfuran (2-MF) catalyst and the application of the catalyst in the reaction of synthesizing 2-methyltetrahydrofuran by gas phase hydrogenation of 2-methylfuran. The catalyst uses non-precious metal Ni as a catalyst active component, alumina as a carrier, a low Ni loading amount, and mild gas phase hydrogenation reaction conditions. The catalyst has high activity, high selectivity and good stability. The catalyst has low cost, saves resources, and has high safety in the gas phase hydrogenation process, thereby achieving better economic benefits.

[0009] The purpose of the present invention is achieved through the following technical solutions: A method for synthesizing 2-methyltetrahydrofuran using a nickel / alumina catalyst, the method comprising the following preparation process: (1) Weigh Ni salt and Al salt, add deionized water to prepare a metal salt solution, and stir at room temperature to completely dissolve them; (2) Mix the salt solution with the alkaline solution and add them into a beaker of distilled water, stirring while adding, and control the pH to 6-8; (3) Aging with stirring at 40°C for 4 h; washing the obtained precipitate with deionized water for multiple times, then washing with n-butanol for 1-2 times, and drying; calcining the dried material to obtain a Ni / Al2O3 catalyst; (4) Ni / Al2O3 catalyst is used in the gas phase hydrogenation reaction process of 2-MF. It is reduced with H2 / N2 mixed gas. After the reduction, the catalyst starts to react. The initial H2 / 2-MF ratio is 0.2-1. After the feed reaction runs for 10-30 hours, the H2 / 2-MF ratio is increased to 4-10 for gas phase catalytic hydrogenation reaction.

[0010] In the method for synthesizing 2-methyltetrahydrofuran using a nickel / aluminum oxide catalyst, the soluble Ni salt and Al salt are both nitrates; and the concentration of the metal salt solution is 0.5-1 mol / L.

[0011] In the method for synthesizing 2-methyltetrahydrofuran using a nickel / aluminum oxide catalyst, the alkaline solution is sodium carbonate or sodium hydroxide solution, and the concentrations thereof are both 0.8-1.1 mol / L; the alkaline solution or ammonia water can be used directly.

[0012] In the method for synthesizing 2-methyltetrahydrofuran using a nickel / aluminum oxide catalyst, the mass percentage of NiO is 3-18%, and the mass percentage of Al2O3 is 97%-82%.

[0013] In the method for synthesizing 2-methyltetrahydrofuran with a nickel / aluminum oxide catalyst, the washing method is vacuum filtration.

[0014] The method for synthesizing 2-methyltetrahydrofuran using a nickel / aluminum oxide catalyst comprises the following steps: drying in air; the drying temperature is 90-150° C.; and the drying time is 10-15 h.

[0015] The method for synthesizing 2-methyltetrahydrofuran using a nickel / aluminum oxide catalyst comprises the following steps: calcining in air; the calcining temperature is 400-700° C.; and the calcining time is 2-6 h.

[0016] The method for synthesizing 2-methyltetrahydrofuran using a nickel / aluminum oxide catalyst, wherein the H2 / N2 mixed gas is a 20-80% N2 / H2 mixed gas.

[0017] In the method for synthesizing 2-methyltetrahydrofuran using a nickel / aluminum oxide catalyst, the initial reaction temperature is 70-130° C. and the reaction pressure is 1-3 MPa.

[0018] In the method for synthesizing 2-methyltetrahydrofuran using a nickel / aluminum oxide catalyst, the reduction temperature is 400-700° C. and the reduction time is 3-6 h.

[0019] The advantages and effects of the present invention are: 1. The preparation process of the present invention is simple to operate, can be prepared in large quantities, and the catalyst loss during the preparation process is small.

[0020] 2. The present invention uses non-precious metal Ni as the active component, the Ni loading amount is relatively low, and the reaction conditions are mild.

[0021] 3. The catalyst of the present invention has high activity, with a 2-MF conversion rate greater than 99.5%, a 2-MTHF selectivity greater than 98.5%, and a catalyst that can operate stably for 2500 hours. The main byproducts in the product are 2-pentanol and pentanol, and other products are very few. DETAILED DESCRIPTION

[0022] The present invention is described in detail below with reference to the embodiments.

[0023] The catalyst preparation method of the present invention comprises preparing Ni salt and Al salt into a metal salt solution, and using a concentrated precipitant solution (Na2CO3 solution, NaOH solution, NH3·H2O or urea, etc.) to precipitate with the solution. The obtained precipitate is washed with deionized water for multiple times, and then washed with n-butanol for 1-2 times, and then dried and calcined to obtain NiO / Al2O3 catalysts with different loading amounts. The NiO content in the catalyst is 3%-18%, and the carrier Al2O3 content is about 97%-82%. When the catalyst is applied to the 2-MF gas phase hydrogenation reaction process, it needs to be reduced with H2 / N2 mixed gas at a certain temperature. After the reduction is completed, a small H2 / 2-MF ratio is first fed for a period of time, and then the H2 / 2-MF is increased to carry out a gas phase catalytic hydrogenation reaction. In addition to 2-MTHF, the product also contains a small amount of 2-pentanol, pentanol, and a very small amount of other substances.

[0024] The preparation method of 2-MTHF catalyst by gas phase hydrogenation of 2-MF comprises the following preparation process: Weigh Ni salt and Al salt, add deionized water to prepare a metal salt solution, and completely dissolve them by ultrasonication and stirring at room temperature.

[0025] Then, the mixed metal salt solution and alkaline solution are added to a beaker containing distilled water in parallel, stirring while adding, and the pH is controlled at 5-8.

[0026] The resulting solution was then stirred and aged for 4 h at room temperature and washed with deionized water for several times and then dried.

[0027] The dried material is calcined to finally obtain a Ni / Al2O3 catalyst.

[0028] Before use, the catalyst is reduced in a 10-80% N2 / H2 mixed gas at 400-700°C for 3-6 h; the reaction temperature is 60-120°C; and the reaction pressure is 1-3MPa.

[0029] The reduced catalyst started to react with an initial H2 / 2-MF ratio of 0.2-1. After the reaction ran for 10-30 hours, the H2 / 2-MF ratio was increased to 4-10 and the catalyst performance was stable.

[0030] According to the mass ratio of different components of the catalyst, the Ni salt and the Al salt are weighed to prepare a solution, and then a precipitant is added and added into a beaker, stirred while adding, and the pH is kept at 7, and stirred and aged at 40°C for 4 hours. The obtained solution is then washed with deionized water for multiple times, and then washed with n-butanol 1-2 times, and then dried at 120°C, and calcined at 450°C for 4 hours to obtain the catalyst. Before use, it needs to be tableted and sieved, and then reduced at 450°C for 4 hours at a gas flow ratio of H2 / N2 of 20-80%.

[0031] Here are some examples: Example 1 Weigh 1.2 g of hydrated nickel nitrate and 35.5 g of hydrated aluminum nitrate respectively and dissolve them in 100 ml of deionized water. Then prepare a certain concentration of Na2CO3 solution as a precipitant. Add the obtained solution and the precipitant into a beaker in parallel while stirring, and keep the solution pH at about 7. After stirring and aging at 40°C for 4 hours, wash the obtained solution with deionized water several times, then wash it with n-butanol 1-2 times, dry it at 120°C for 12 hours, and calcine it at 450°C for 4 hours to obtain Ni / Al2O3 catalyst.

[0032] Example 2 Weigh 1.4 g of hydrated nickel nitrate and 35.5 g of hydrated aluminum nitrate respectively and dissolve them in 100 ml of deionized water. Then prepare a certain concentration of Na2CO3 solution as a precipitant. Add the obtained solution and the precipitant into a beaker in parallel while stirring, and keep the solution pH at about 7. After stirring and aging at 40°C for 4 hours, wash the obtained solution with deionized water several times, then wash it with n-butanol 1-2 times, dry it at 120°C for 12 hours, and calcine it at 450°C for 4 hours to obtain Ni / Al2O3 catalyst.

[0033] Example 3 Weigh 1.6 g of hydrated nickel nitrate and 35.5 g of hydrated aluminum nitrate respectively and dissolve them in 100 ml of deionized water. Then prepare a certain concentration of Na2CO3 solution as a precipitant. Add the obtained solution and the precipitant into a beaker in parallel while stirring, and keep the solution pH at about 7. After stirring and aging at 40°C for 4 hours, wash the obtained solution with deionized water several times, then wash it with n-butanol 1-2 times, dry it at 120°C for 12 hours, and calcine it at 450°C for 4 hours to obtain Ni / Al2O3 catalyst.

[0034] Example 4 Weigh 2.4g of hydrated nickel nitrate and 34.5g of hydrated aluminum nitrate respectively and dissolve them in 100ml of deionized water. Then prepare a certain concentration of Na2CO3 solution as a precipitant. Add the obtained solution and the precipitant into a beaker in parallel while stirring, and keep the solution pH at about 7. After stirring and aging at 40℃ for 4h, wash the obtained solution with deionized water several times, then wash it with n-butanol 1-2 times, dry it at 120℃ for 12h, and calcine it at 450℃ for 4h to obtain Ni / Al2O3 catalyst.

[0035] Example 5 Weigh 4.7g of hydrated nickel nitrate and 32g of hydrated aluminum nitrate respectively and dissolve them in 100ml of deionized water. Then prepare a certain concentration of Na2CO3 solution as a precipitant. Add the obtained solution and the precipitant into a beaker in parallel while stirring, and keep the solution pH at about 7. After stirring and aging at 40℃ for 4h, wash the obtained solution with deionized water several times, then wash it with n-butanol 1-2 times, dry it at 120℃ for 12h, and calcine it at 450℃ for 4h to obtain Ni / Al2O3 catalyst.

[0036] Catalyst performance test 1.0 g of the prepared catalyst particles were loaded into the reactor and reduced in a mixture of N2:H2=3:1 at 450°C for 4 h. After the temperature of the reactor dropped to the reaction temperature, N2 was turned off and the H2 flow rate was adjusted to 80 mL / min. The raw material 2-MF was transported to the evaporator through an infusion pump and entered the reactor together with H2 for reaction. The obtained product was analyzed by gas chromatography.

[0037] At a reaction pressure of 1.6 MPa, a reaction temperature of 70 °C and a liquid hourly space velocity of 4.4 h -1 Under the conditions, the H2 / 2-methylfuran ratio was 0.2, the feed was continued for 3 hours, and then the H2 / 2-methylfuran ratio was increased to 10. The performance evaluation results of the catalyst are listed in Table 1.

[0038] Table 1 Catalyst performance evaluation results Examples 2-Methyltetrahydrofuran conversion rate (100%) 2-Methyltetrahydrofuran selectivity (100%) 1 99.5 99 2 100 99 3 100 98.9 4 100 98.8 5 100 98.5 .

Claims

1. A method for synthesizing 2-methyltetrahydrofuran using a nickel / alumina catalyst, characterized in that: The method comprises the following preparation process: (1) Weigh Ni salt and Al salt, add deionized water to prepare a metal salt solution, and stir at room temperature to completely dissolve them; (2) Mix the salt solution with the alkaline solution and add them into a beaker of distilled water, stirring while adding, and control the pH to 6-8; (3) Aging with stirring at 40°C for 4 h; washing the obtained precipitate with deionized water for multiple times, then washing it with n-butanol for 1-2 times, and drying it; calcining the dried material to obtain a Ni / Al2O3 catalyst; (4) Ni / Al2O3 catalyst is used for 2-MF gas phase hydrogenation reaction. It is reduced with H2 / N2 mixed gas. After the reduction, the catalyst starts to react. The initial H2 / 2-MF ratio is 0.2-1. After the feed reaction runs for 10-30 hours, the H2 / 2-MF ratio is increased to 4-10 for gas phase catalytic hydrogenation reaction.

2. The method for synthesizing 2-methyltetrahydrofuran using a nickel / alumina catalyst according to claim 1, characterized in that: The soluble Ni salt and Al salt are both nitrates; the concentration of the metal salt solution is 0.5-1 mol / L.

3. The method for synthesizing 2-methyltetrahydrofuran using a nickel / alumina catalyst according to claim 1, characterized in that: The alkaline solution is sodium carbonate or sodium hydroxide solution, and the concentration of the alkaline solution is 0.8-1.1 mol / L; or ammonia water can be used directly.

4. The method for synthesizing 2-methyltetrahydrofuran using a nickel / alumina catalyst according to claim 1, characterized in that: The mass percentage of NiO is 3-18%, and the mass percentage of Al2O3 is 97%-82%.

5. The method for synthesizing 2-methyltetrahydrofuran using a nickel / alumina catalyst according to claim 1, characterized in that: The washing methods described are all vacuum filtration.

6. The method for synthesizing 2-methyltetrahydrofuran using a nickel / alumina catalyst according to claim 1, characterized in that: The drying method is air drying; the drying temperature is 90-150°C; and the drying time is 10-15 hours.

7. The method for synthesizing 2-methyltetrahydrofuran using a nickel / alumina catalyst according to claim 1, characterized in that: The calcination method is air calcination; the calcination temperature is 400-700°C; and the calcination time is 2-6 hours.

8. The method for synthesizing 2-methyltetrahydrofuran using a nickel / alumina catalyst according to claim 1, characterized in that: The H2 / N2 mixed gas is 20-80% N2 / H2 mixed gas.

9. The method for synthesizing 2-methyltetrahydrofuran using a nickel / alumina catalyst according to claim 1, characterized in that: The initial reaction temperature is 70-130° C.; the reaction pressure is 1-3 MPa.

10. The method for synthesizing 2-methyltetrahydrofuran using a nickel / alumina catalyst according to claim 1, characterized in that: The reduction temperature is 400-700° C., and the reduction time is 3-6 h.