Hydroalkylation process
In a process for producing phenol, benzene is hydroalkylated with hydrogen in the presence of a catalyst under conditions effective to produce a hydroalkylation reaction product comprising cyclohexylbenzene and cyclohexane. At least a portion of the cyclohexane from said hydroalkylation reaction product is then dehydrogenated to produce a dehydrogenation effluent comprising benzene, toluene and hydrogen. At least a portion of the dehydrogenation effluent is washed with a benzene-containing stream to transfer at least a portion of the toluene from the dehydrogenation effluent to the benzene-containing stream.
1. A hydroalkylation process comprising:
(a) hydroalkylating benzene with hydrogen in the presence of a catalyst under conditions effective to produce a hydroalkylation reaction product comprising cyclohexylbenzene and cyclohexane;
(b) contacting at least a portion of the hydroalkylation reaction product with a dehydrogenation catalyst to produce a dehydrogenation effluent having at least a portion of the cyclohexane converted to benzene and hydrogen, wherein the dehydrogenation effluent further comprises toluene; and
(c) washing at least a portion of the dehydrogenation effluent with a benzene-containing stream to produce a toluene-depleted dehydrogenation effluent and a wash stream containing at least a portion of the toluene from the dehydrogenation effluent, wherein the at least a portion of the dehydrogenation effluent is in the vapor phase and the benzene-containing stream is in the liquid phase.
2. The process of claim 1 , wherein the at least a portion of the dehydrogenation effluent contains at least 50 wt % hydrogen, the wt % based upon the weight of the at least a portion of the dehydrogenation effluent.
3. The process of claim 1 , wherein at least a portion of the toluene in the dehydrogenation effluent is formed from the decomposition of the cyclohexylbenzene.
4. The process of claim 1 , wherein the wash stream contains at least 80 wt % of the toluene from the dehydrogenation effluent, the wt % based upon the weight of the dehydrogenation effluent.
5. A hydroalkylation process comprising:
(a) hydroalkylating benzene with hydrogen in the presence of a catalyst under conditions effective to produce a hydroalkylation reaction product comprising cyclohexylbenzene and cyclohexane;
(b) contacting at least a portion of the hydroalkylation reaction product with a dehydrogenation catalyst to produce a dehydrogenation effluent having at least a portion of the cyclohexane converted to benzene and hydrogen, wherein the dehydrogenation effluent further comprises toluene;
(c) separating said dehydrogenation effluent into a liquid stream containing benzene and toluene from said dehydrogenation effluent and a gas stream containing hydrogen and toluene from said dehydrogenation effluent;
(d) fractionating said liquid stream to produce a toluene-depleted and benzene-enriched overhead stream; and
(e) washing the gas stream with a portion of said overhead stream to produce a toluene-depleted hydrogen stream and a wash stream containing benzene and toluene.
6. The process of claim 5 , wherein the liquid stream contains at least 60 wt % of the benzene and at least 60 wt % of the toluene from said dehydrogenation effluent, the wt % based upon the weight of the dehydrogenation effluent.
7. The process of claim 5 , wherein the gas stream contains at least 80 wt % of the hydrogen from the dehydrogenation effluent, the wt % based upon the weight of the dehydrogenation effluent.
8. The process of claim 5 , wherein the overhead stream contains less than 40 wt % of the toluene from the liquid stream, the wt % based upon the weight of the liquid stream.
9. The process of claim 5 , wherein the overhead stream contains greater than 60 wt % of the benzene from the liquid stream, the wt % based upon the weight of the liquid stream.
10. The process of claim 5 , wherein the wash stream contains at least 80 wt % of the toluene from the gas stream, the wt % based upon the weight of the gas stream.
11. The process of claim 5 , wherein the gas stream flows countercurrent to said overhead stream in the washing (e).
12. The process of claim 5 , wherein the washing (e) is conducted at a temperature between about 10° C. and about 160° C.
13. The process of claim 5 , wherein the washing (e) is conducted at a temperature between about 40° C. and about 140° C.
14. The process of claim 5 , wherein the ratio of benzene in the overhead stream to the benzene entrained in the gas stream is at least 1.
15. The process of claim 5 , wherein the ratio of benzene in the overhead stream to the benzene entrained in the gas stream is about 1.2 to about 1.4.
16. The process of claim 5 , wherein the toluene content of the gas stream is at least 5 ppmw and the toluene content of the toluene-depleted hydrogen stream is less than 5 ppmw.
17. The process of claim 5 , wherein the toluene content of the gas stream is at least 10 ppmw and the toluene content of the toluene-depleted hydrogen stream is less than 1 ppmw.
18. The process of claim 5 , wherein at least a portion of the toluene-depleted hydrogen stream is recycled to (a).
19. The process of claim 5 , wherein at least a portion of the toluene-depleted hydrogen stream is compressed before being recycled to the hydroalkylating (a).
20. The process of claim 5 , wherein at least a portion of the wash stream is recycled to (d) to remove at least a portion of the toluene and recycled to hydroalkylating (a).
21. The process of claim 5 , and further comprising:
(i) providing a benzene feed containing toluene as an impurity to said fractionating (d); and
(ii) supplying a portion of the overhead stream to (a).
22. The process of claim 5 , wherein the dehydrogenation catalyst comprises: (i) 0.05 wt % to 5 wt % of a metal selected from Group 14 of the Periodic Table of Elements; and (ii) 0.1 wt % to 10 wt % of a metal selected from Groups 6 to 10 of the Periodic Table of Elements, the wt %s based upon total weight of the dehydrogenation catalyst.
23. The process of claim 22 , wherein the metal selected from Group 14 of the Periodic Table of Elements is tin and the metal selected from Groups 6 to 10 of the Periodic Table of Elements is platinum or palladium.
24. The process of claim 5 , wherein the contacting (b) is conducted under dehydrogenation conditions comprising a temperature between 200° C. and 550° C. and a pressure between 100 kPa and 7,000 kPa.
25. The process of claim 5 , and further comprising:
(f) recovering at least a portion of the cyclohexylbenzene from said hydroalkylation reaction product;
(g) oxidizing at least a portion of the cyclohexylbenzene recovered in (f) to cyclohexylbenzene hydroperoxide; and
(h) cleaving at least a portion of the cyclohexylbenzene hydroperoxide produced in (g) to produce phenol and cyclohexanone.