Method for producing tetrahydrofuran

1. A method for producing tetrahydrofuran, comprising:

feeding a raw material liquid in a reactor, wherein the raw material liquid comprises 1,4-butanediol, from 0.01 to 0.35% by weight of 2-(4-hydroxybutoxy) -tetrahydrofuran, and 1 ppm by weight or more and not more than 1,000 ppm by weight of at least one of an amine and an amide in terms of a concentration as converted into a nitrogen atom; and

carrying out a dehydration cyclization reaction of 1,4-butanediol in the reactor in the presence of an acid catalyst having a pKa value of not more than 4.

2. A method for producing tetrahydrofuran, comprising:

carrying out a dehydration cyclization reaction of 1,4-butanediol in a reactor in the presence of an acid catalyst having a pKa value of not more than 4,

wherein a reaction liquid within the reactor comprises 1 ppm by weight or more and not more than 10,000 ppm by weight of at least one of an amine and an amide in terms of a concentration as converted into a nitrogen atom.

3. The method according to claim 1 ,

wherein a reaction liquid within the reactor comprises 1 ppm by weight or more and not more than 10,000 ppm by weight of the at least one of an amine and an amide in terms of a concentration as converted into a nitrogen atom.

4. The method according to claim 1 ,

wherein a reaction liquid within the reactor comprises 0.1% by weight or more and not more than 10% by weight of water.

5. The method according to claim 1 , further comprising:

extracting a gas comprising tetrahydrofuran and water present in a gas phase within the reactor to outside of the reactor.

6. The method according to claim 1 ,

wherein a temperature of a reaction liquid within the reactor is 80° C. or higher and not higher than 250° C.

7. The method according to claim 1 , further comprising:

heating crude 1,4-butanediol at 80° C. or higher in the presence of the at least one of an amine and an amide to reduce a content of 2-(4-hydroxybutoxy)-tetrahydrofuran in the crude 1,4-butanediol, prior to the feeding.

8. The method according to claim 2 ,

wherein the reaction liquid within the reactor comprises 0.1% by weight or more and not more than 10% by weight of water.

9. The method according to claim 2 , further comprising:

extracting a gas comprising tetrahydrofuran and water present in a gas phase within the reactor to outside of the reactor.

10. The method according to claim 2 ,

wherein a temperature of the reaction liquid within the reactor is 80° C. or higher and not higher than 250° C.

11. The method according to claim 2 , further comprising:

heating crude 1,4-butanediol at 80° C. or higher in the presence of the at least one of an amine and an amide to reduce a content of 2-(4-hydroxybutoxy)-tetrahydrofuran in the crude 1,4-butanediol, prior to the carrying out of the dehydration cyclization reaction of 1,4-butanediol.

12. The method according to claim 1 , wherein the acid catalyst is organic sulfonic acid.

13. The method according to claim 2 , wherein the acid catalyst is organic sulfonic acid.

14. The method according to claim 1 ,

wherein the amine is at least one selected from the group consisting of octlyamine, nonylamine, 1-aminodecane, aniline, phenethylamine, dipentylamine, dihexylamine, diheptylamine, dicyclohexylamine, N-methylaniline, tributylamine, tripentylamine, N,N-dimethylaniline, 1,3-propanediamine, N,N-dimethyl-1,6-hexanediamine, N-butylpyrrole, N-butyl-2,3-dihydropyrrole, N-butylpyrrolidine, 2,3-dihydro-1H-indole, 4-aminomethylpiperidine, 4-dimethylaminopyridine, 1,2,3,4-tetrahydroquinoline, 4-amino-5,6-dihydro-2-methylpyrimidine, 2,3,5,6-tetramethylpyrazine, 3,6-dimethylpyridazine, 4-aminobutanol, 2-aminobutanol, 2-ethylmorpholine, N-methoxycarbonylmorpholine, prolinol, 3-hydroxypiperidine, 4-hydroxypiperidine, tetrahydrofurfurylamine, and 3-aminotetrahydropyran, and

the amide is at least one selected from the group consisting of acetamide, N-methylacetamide, N-ethylacetamide, N,N-dimethylacetamide, benzamide, 2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, 2-piperidone, and N-methylpiperidone.

15. The method according to claim 2 ,

wherein the amine is at least one selected from the group consisting of octylamine, nonylamine, 1-aminodecane, aniline, phenethylamine, dipentylamine, dihexylamine, diheptylamine, dicyclohexylamine, N-methylaniline, tributylamine, tripentylamine, N,N-dimethylaniline, 1,3-propanediamine, N,N-dimethyl-1,6-hexanediamine, N-butylpyrrole, N-butyl-2,3-dihydropyrrole, N-butylpyrrolidine, 2,3-dihydro-1H-indole, 4- aminomethylpiperidine, 4-dimethylaminopyridine, 1,2,3,4-tetrahydroquinoline, 4-amino-5,6- dihydro-2-methylpyrimidine, 2,3,5,6-tetramethylpyrazine, 3,6-dimethylpyridazine, 4- aminobutanol, 2-aminobutanol, 2-ethylmorpholine, N-methoxycarbonylmorpholine, prolinol, 3-hydroxypiperidine, 4-hydroxypiperidine, tetrahydrofurfurylamine, and 3-aminotetrahydropyran, and

the amide is at least one selected from the group consisting of acetamide, N-methylacetamide, N-ethylacetamide, N,N-dimethylacetamide, benzamide, 2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, 2-piperidone, and N-methylpiperidone.

16. The method according to claim 7 , wherein the heating of the crude 1,4-butanediol is carried out such that the raw material liquid comprises from 0.01 to 0.35% by weight of 2-(4-hydroxybutoxy)-tetrahydrofuran.

17. The method according to claim 7 , wherein the crude 1,4-butanediol has a pH value of from 7 to 12.

18. The method according to claim 1 , wherein the acid catalyst is a metal-free organic acid or a metal-free phosphoric acid.

19. The method according to claim 2 , wherein the acid catalyst is a metal-free organic acid or a metal-free phosphoric acid.