| 摘要 |
Xylenes are produced by passing a charge of C8 acyclic hydrocarbons free from unsaturates and rich in 2,2,4-trimethyl pentane at 510-594 DEG C. and pressures up to atmospheric over a catalyst comprising eta-alumina and 15-25% of chromium oxide (see parent Specification), separating the effluent from the dehydrogenation zone into an aromatics fraction, a C8 hydrocarbon fraction rich in C8 acyclic hydrocarbons including 2,2,4-trimethyl pentane and C8 monoolefins, and a C4 fraction containing isobutylene, dimerizing the isobutylene to form diisobutylenes, hydrogenating the dimer and the C8 fraction to produce fresh charge free from unsaturates and rich in 2,2,4-trimethylpentane, and recovering from the aromatics fraction a C8 concentrate rich in p-xylene. The C4 fraction with or without a fresh C4 charge containing isobutylene may be extracted with cold sulphuric acid and the extract containing isobutylene may be dimerized with a sulphuric acid catalyst, e.g. at 24-38 DEG C. |
