Tetrahydrofuran production process has the following five kinds.
(1) Furfural method
Furan is decarbonylated to furan and then hydrogenated.
This is one of the first methods for industrial production of tetrahydrofuran. Furfural is mainly produced by hydrolysis of corncob and other agricultural and sideline products. The law has serious pollution and is not conducive to large-scale production. It has gradually been eliminated.
(2) Maleic Anhydride Catalytic Hydrogenation
The maleic anhydride and hydrogen are fed into the reactor containing the nickel catalyst from the bottom. The ratio of tetrahydrofuran to gamma-butyrolactone in the product can be controlled by adjusting the operating parameters. The reaction product and the raw hydrogen are cooled to about 50°C and enter the bottom of the scrubber to separate the unreacted hydrogen and gaseous and liquid products. The unreacted hydrogen and gaseous products are washed and recycled to the reactor. The liquid product is distilled to obtain the tetrahydrofuran product. .
The process can be used to adjust the ratio of γ-butyrolactone to tetrahydrofuran within the range of 0 to 5:1. The single-pass conversion of maleic anhydride reaches 100%, the selectivity to tetrahydrofuran ranges from 85% to 95%, and the product content reaches 99.97%. . The process has the advantages of good catalyst performance, simple process, and low investment.
(3) Dehydration of 1,4-butanediol
The process is as follows: 1087 kg of 22% aqueous sulfuric acid solution is added to the reactor, and 1,4-butanediol is added at a rate of 110 kg/h at 100° C. The temperature at the top of the tower is maintained at 80° C. at a rate of about 110 kg/h. An aqueous solution containing 80% tetrahydrofuran was obtained from the top of the column. After adding 50t of 1,4-butanediol, about 70 kg of coke was removed from the reactor. The coke is filtered and the resulting aqueous solution of sulfuric acid can be reused. The yield of tetrahydrofuran can reach over 99%.
Sulfuric acid is the earliest catalyst used in the industrial production of tetrahydrofuran, and it is also a catalyst that is widely used in production today. This technology is mature, the process is relatively simple, the reaction temperature is lower, the yield of tetrahydrofuran is higher, but the sulfuric acid is apt to corrode the equipment and pollute the environment.
(4) Dichlorobutene method
1,4-Dichlorobutene is used as a raw material to produce butenediol by hydrolysis and then obtained by catalytic hydrogenation.
1,4-dichlorobutene is hydrolyzed in sodium hydroxide solution, butenediol is generated at 110° C., sodium chloride is removed by centrifugation, and the filtrate is concentrated in an evaporation crystallizer to separate the alkali metal carboxylate salt. The distillation column removes high boilers. The refined butenediol is sent to a reactor, nickel is used as a catalyst, and butylene glycol is hydrogenated to generate butylene glycol at 80-120° C. and a certain pressure, and after being distilled, a human cyclization reactor is introduced at atmospheric pressure. The crude tetrahydrofuran is produced in an acid medium at 120-140° C., dehydrated by distillation and degassed, and finally high-purity tetrahydrofuran is obtained by distillation.
This method is simple, mild conditions, high yield, small amount of catalyst can be used continuously.
(5) Butadiene Oxidation
To butadiene as raw material, the furan obtained by oxidation, and then hydrogen derived. This law has been industrialized abroad.