Process for the selective conversion of naphtha to aromatics and olefins
AssigneeMobil Oil Corporation
InventorsRalph M. Dessau, Mohsen N. Harandi
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Abstract
A staged process has been discovered for the selective conversion of paraffins in naphtha to aromatics and conversion of naphthenes in naphtha to olefins. In a first stage, n-paraffins in naphtha are converted to aromatics over modified non acidic zeolite catalyst particles with a low conversion of naphthenes in the feedstream. The effluent from the first stage is cascaded to a second stage reactor containing acidic zeolite catalyst wherein naphthenes are converted to light olefins. Advantageously, the process of the invention results in a reduction in the production of light C.sub.1 -C.sub.4 paraffins compared to the prior art. The preferred catalyst for the first stage is a platinum modified zeolite containing tin.
Claims21
A staged process for the selective conversion of C.sub.6 + naphtha hydrocarbon feedstream containing n-paraffins and naphthenes to C.sub.6 + aromatics and light olefins with a reduced production of C.sub.3 - paraffins, comprising:
- contacting said feedstream in an aromatization reaction zone with nonacidic zeolite catalyst particles containing metal from Group VIII of the Periodic Chart of the Elements under aromatization reaction conditions whereby a high selective conversion of said n-paraffins to said aromatics is achieved and said first reaction zone effluent is rich in unconverted naphthenes;
- passing said effluent without separation to a naphthenes cracking zone in contact with cracking catalyst comprising acidic zeolite catalyst particles under cracking conditions whereby conversion of said naphthenes to light olefins is achieve while said C.sub.3 - paraffins production is reduced;
- and
- separating effluent from said cracking zone by distillation to recover an overhead stream comprising hydrogen and C.sub.5 - olefinic hydrocarbons and a bottom stream comprising C.sub.6 + hydrocarbons rich in aromatics.
In the process for naphtha reforming comprising contacting C.sub.6 + naphtha feedstream containing n-paraffins and naphthenes with non-acidic medium pore shape selective zeolite catalyst particles containing metal from Group VIII of the Periodic Chart of the Elements under aromatization or dehydrocyclization reaction conditions in an aromatization reaction zone, the improvement comprising:
- passing substantially the entire effluent from said aromatization reaction zone to a cracking reaction zone in contact with cracking catalyst comprising medium pore shape selective zeolite catalyst particles under cracking conditions whereby said cracking reaction zone effluent is produced comprising at least an 80 weight % conversion of said n-paraffins to C.sub.6 + aromatics and at least 50 weight % conversion of said naphthenes to light olefins;
- separating effluent from said second zone by distillation to recover an overhead stream comprising hydrogen and C.sub.5 - olefinic hydrocarbons and a bottom stream comprising C.sub.6 + hydrocarbons rich in aromatics.
Dependencies are inferred from the claim text.