GB825268A - A process for the preparation of liquid hydrocarbon mixtures having a high octane number - Google Patents

Abstract

High octane gasolines are prepared by catalytically reforming a gasoline or fraction thereof in the presence of hydrogen followed by thermally reforming the reaction mixture without previous complete or partial separation of hydrogen or any other component and at the same pressure as the catalytic reforming. The starting gasoline should boil within the range 30 DEG to 205-235 DEG C. and is preferably a straightrun naphtha boiling in the range 93-190 DEG C. Gasolines obtained by thermal or catalytic cracking may be used but olefinic components should be hydrogenated before use. Paraffins such as normal butane, pentane or hexane may be added. The feed may be freed of sulphur and nitrogen if necessary. Reforming catalysts include one or more metals of Group VI and/or VIII as metals, sulphides or oxides and may be supported on alumina. Preferred are molybdena and/or chromia supported on alumina or 0.1-2% platinum supported on an acidic alumina support, e.g. containing silica, boron oxide, phosphoric acid or 0.1-2% fluorine and/or chlorine. Conditions generally are 420-560 DEG C. and a hydrogen partial pressure of 6-50 atmospheres gauge. Fixed, moving or fluidized beds of catalyst can be used in a heated vessel or in a series of unheated reactors with intermediate heating. The thermal reforming may be carried out at 500-700 DEG C. Residence time depends on the temperature and degree of conversion required but may be, for example, 8 seconds at 600 DEG C. or 3 seconds at 615 DEG C. for 80% cracking of octanes present. Gases are separated from the liquid product and recycled but olefinic constituents are preferably first hydrogenated, e.g. over a cobalt oxide-molybdena-alumina catalyst; this may be done before or after the gas is mixed with p the gasoline feed. High-boiling components and those boiling below butene or pentane may be removed from the product by distillation. It may be blended with other gasolines such as straightrun, cracked or thermally or catalytically reformed gasolines or fractions thereof, polymerizate or alkylate gasolines, isomerized light hydrocarbon fractions, isopentane or butane. It may be improved by adding tetraethyl lead and antioxidants. Specifications 600,471, 665,618, 742,769 and U.S.A. Specifications 2,143,472 and 2,490,287 are referred to.