| 摘要 |
Aromatic hydrocarbons are produced by passing vapours of a normally liquid hydrocarbon feed stock consisting of paraffins or naphthenes having at least 6 carbon atoms in an unbranched chain or in a ring respectively or mixtures thereof, together with a water-free diluent consisting of paraffins containing not more than 4 carbon atoms, the molar ratio of diluent to feed stock being about 0.5-20 : 1, over an aromatizing catalyst under aromatizing conditions. A by-product gas enriched in hydrogen useful as a fuel or for oxidation to CO + H2 mixtures and, where butanes are present in the diluent, containing n and isobutenes formed by dehydrogenation and isomerization, is also obtained. The diluent may be natural gas, off-gas from polymerization, alkylation or alcohol processes of C1-C3 with or without some C4 and from which olefins have been removed, or refinery gas having low olefin content. An n-hexane fraction from naphtha is suitable for benzene production; a heptane and methylcyclohexane fraction for toluene. Aromatizing catalysts include moblydena or chromia with various carriers and promoters. Temperature is about 850-1150 DEG F. and pressure atmospheric or up to 50 p.s.i. Fixed, moving or fluidized catalyst may be used with regeneration and stripping of adsorbed water and oxygen before recycling. The reaction products may be fractionated to recover aromatics or an aromatized naphtha, a hydrogen-rich gas, and gaseous hydrocarbons which may be recycled as diluent. Examples describe the aromatization of n-hexane over a chromia-alumina catalyst using no diluent, various hydrogen ratios, and a 3 : 1 molar ratio of methane; the aromatization under the same conditions of a feed containing n-hexane and cyclohexane together with methyl pentanes and methyl cyclopentane when coking is materially increased; the production of toluene from n-heptane, methyl cyclohexane concentrates with methane or hydrogen or no diluent; and the production of benzene and butenes using a hexane-rich fraction and a 10 : 1 molar ratio of butane or isobutane as diluent. |
