Preparation background and overview of 2-methyltetrahydrofuran
2-Methyltetrahydrofuran (hereinafter referred to as 2‑Me‑THF) is an important biogasoline fuel, high-end environmentally friendly solvent and chemical intermediate. When used as biogasoline fuel, it can be miscible with gasoline in any proportion and has excellent oxidation and vapor pressure properties. Research shows that its proportion in gasoline can exceed 60% by volume without any impact on engine performance or increase in vehicle fuel consumption. As a gasoline additive, it can have higher economic value. In addition, 2-methyltetrahydrofuran can also be used as a co-solvent for ethanol, which can reduce the gas pressure of ethanol and increase the mixing ratio. The exhaust emissions are 45 to 50% lower than existing fuel ethanol. It is an essential fuel group for new “hybrid fuel engines” point. As an environmentally friendly solvent, 2-methyltetrahydrofuran has a high boiling point and low water solubility. It is a universal solvent that can be used in a variety of organometallic reactions. It is superior to the current “universal solvent” tetrahydrofuran in many aspects.
Preparation and application of 2-methyltetrahydrofuran
2-Methyltetrahydrofuran (hereinafter referred to as 2-MeTHF) is an important organic synthesis intermediate and solvent, and is a fine chemical material in the field of new materials and applications. In organic synthesis, it is mainly used in the synthesis of chloroquine phosphate, primaquine phosphate, thiamine, etc. In terms of solvent application, it is mainly used for the organic synthesis of resins, natural rubber, ethyl cellulose and chloroacetic acid-vinyl acetate copolymers. As a cyclic ether and a Lewis base, 2-methyltetrahydrofuran is an environmentally friendly and unique solvent with excellent performance. In recent years, due to the excellent performance and environmentally friendly characteristics of 2-methyltetrahydrofuran, it has developed rapidly in the field of solvent replacement applications: ① Used to replace tetrahydrofuran, ether, etc. that have serious safety hazards, and used in Grignard reactions Solvent; ② Used to replace highly toxic halogenated hydrocarbons, benzene, etc. as reaction solvents or extraction solvents for organic synthesis; ③ Solvents used in organometallic reactions and two-phase reactions.
2-Methyltetrahydrofuran is a low-polarity cyclic ether with a high octane number and can be mixed with petroleum fuel in any proportion. It is a relatively ideal fuel and fuel additive. It is also an important intermediate in the synthesis of some drugs, such as chloroquine phosphate and bianquine phosphate. 2-Methyltetrahydrofuran has a suitable boiling point (80.2oC) and is similar in basicity to tetrahydrofuran. It is considered to be the most suitable substitute for tetrahydrofuran and can be used as a solvent for some organic synthesis and polymer polymerization.
2-Methyltetrahydrofuran
Preparation of 2-methyltetrahydrofuran
There are various synthesis methods for 2-methyltetrahydrofuran, which can be divided into glycol method, lactone method and furfural method according to different starting materials. The glycol method can be produced by dehydrating 2-methyl-1,4-butanediol using pentaethoxyphosphorus as a catalyst and methylene chloride as a solvent. This method has mild conditions, high yield, and relatively low equipment requirements. Low, but the raw materials are rare and can easily cause environmental pollution, making it difficult to promote. The lactone method can use hydrated zirconia as a catalyst and dissolve the lactone in an alcohol solution. This method has a short process and high yield, but the reaction conditions are harsh and a large amount of heavy metal pollution will be produced. The most significant feature of the furfural method is that it can be produced from furfural, an important agricultural and sideline product. This method has mature technology, stable technology and low cost, opening up broad prospects for the deep processing of agricultural and sideline products. However, using furfural as a raw material requires harsh reaction conditions, especially high pressure requirements and high equipment investment.
Specific method:
Preparation method 1 of 2-methyltetrahydrofuran:
Add copper nitrate and nickel nitrate into the silicon oxide aqueous solution in proportion (Cu: Ni: silicon oxide = 25:5:70, weight ratio), stir evenly at room temperature, and then adjust the pH to Cu and Ni ions by adding precipitant After precipitation is complete, continue stirring for 2 hours. The obtained solution is filtered, dried and roasted to obtain a catalyst precursor. The aminopyridine precursor is passed through hydrogen at a pressure of 0.3-0.5MPa. The volume ratio of hydrogen to catalyst is 350:1. The catalyst bed is heated to 300°C within 36 hours. The reduction is completed at a constant temperature of 8 hours to prepare Cu. System catalyst Cu-Ni/SiO2.
Add Cu-based catalyst Cu-Ni/SiO2 into the continuous fixed-bed reactor. At the reaction temperature of 160°C, the pressure of 2.8Mpa, the molar ratio of hydrogen to levulinate is 80, and the mass space velocity of levulinate is 1.0h-1, the conversion rate of levulinate is 100%, and the selectivity of 2-methyltetrahydrofuran is 97.8%.
Preparation method 2 of 2-methyltetrahydrofuran:
Prepare a catalyst in which ruthenium and a non-noble metal zinc are simultaneously loaded on an activated carbon carrier: 3% Ru.5% Zn/C. The operation steps are as follows: Weigh 0.62g RuCl3 and 1.05gZnCl2, add pure water to make 300mL Pour the aqueous solution into a 500mL 3-neck flask, then add 10.0g of activated carbon carrier, seal it and let it stand in a constant temperature water bath at 25°C for 12 hours, then raise the temperature to 50°C and stir for 2 hours. Then adjust the pH value of the solution to 9 with NaOH, reduce it with analytical pure formaldehyde, filter it, and wash the filter cake with deionized water until there is no chloride ion in the filtrate ammonium pyridine. After suction filtration, put the filter cake into a vacuum oven at 100 Dry at ℃ for 3 hours to obtain the composite catalyst.
Preparation of 2-MeTHF: In the pressure reactor, add 100g of MeF and 1g (1% of the mass of MeF) the composite catalyst prepared as above. The reaction temperature is 100°C.Under the condition that the stress pressure is 4.0MPa, a liquid phase hydrogenation reaction is carried out; after the hydrogen absorption is terminated, the reaction liquid is cooled to 20°C, the excess hydrogen is evacuated, and the reaction product is filtered to remove the catalyst after replacing it with nitrogen twice. The filtrate was sampled for gas phase analysis, and the 2-methyltetrahydrofuran content was 26.7%, and the 2-methyltetrahydrofuran content was 70.1%.
