Patent GB-714061-A (GB)
Title: Improvements in or relating to the hydroforming of naphthas
IPC: B01J23/28
Filed: 1951-04-20
Abstract: Virgin naphtha is hydroformed by first contacting a mixture of the naphtha and hydrogen with a hydroforming catalyst (e.g. molybdenum or chromium oxide supported upon activated alumina or zinc aluminate spinel) at a temperature in the range 750 DEG -1050 DEG F., a pressure from atmospheric to 1000 p.s.i., and for a period sufficient to convert a substantial portion of the naphtha into aromatics, and then contacting the aromatic product and hydrogen with a hydroforming catalyst in a second reaction stage at a temperature from 750 DEG  to 1150 DEG F. and a pressure from atmospheric to 3000 p.s.i., the second stage catalyst comprising an oxide or sulphide of a Group VI metal upon an alumina-containing support and having incorporated therein from 0.5 to 3.0 weight per cent. of a fluoride calculated as HF and based on the total weight of the catalyst.  The process is effective for obtaining anti-knock gasoline.  There is no nett consumption of hydrogen, and accordingly recycle of normally gaseous components separated from the products should provide a sufficient partial pressure of hydrogen in the reaction zone.  The catalyst used in the first stage may contain up to about 5 per cent. of a Group II metal oxide as stabilizer or promoter. Contact of the naphtha with the catalyst in both stages may be effected in fixed, moving or fluidized beds.  In addition to the Group VI metal oxide or sulphide, the catalyst used in the second stage may also contain calcium oxide, zinc oxide or magnesium oxide.  Stabilizing components such as zirconia and silica may be present.  The catalyst to be used in the second stage is preferably treated with hydrogen fluoride, ammonium fluoride or hydrofluosilicic acid, in order to incorporate fluoride therein. In a preferred embodiment a dilute aqueous solution of hydrofluoric acid, in sufficient amount to add 1 weight per cent. HF to the catalyst, is slurried with the wet alumina base prior to impregnation with the Group VI metal oxide or sulphide.  The fluoride activation can, however, be carried out on the finished catalyst; if desired in situ after charging to the reaction vessel, in which case moist hydrogen fluoride gas is used as the activating agent.  In an example, a solution of aluminium chloride hexahydrate was added, with stirring, to a solution of ammonium hydroxide.  The slurry was filtered, washed with water, adjusted to a pH between 8.5 and 10 with ammonium hydroxide, and re-filtered.  The gel was then mulled for three hours with acetic acid.  Part of the gel was then stirred for 1 hour with a solution of 20 grm. of 48 per cent. hydrofluoric acid diluted with 200 cc. of water.  The resulting material was impregnated with an aqueous solution of chromium trioxide, having a cencentration of 132 grm. p  CrO3 in 200 cc. of water.  This mixture was dried at 240 DEG F., and calcined 3 hours at 1100 DEG F.  It was then pilled.  The nominal composition was 80 Al2O3-20 Cr2O3, on a fluoride-free basis.  The fluoride-free catalyst was prepared similarly from the remainder of the gel, treatment with hydrogen fluoride being omitted.  The two catalysts were charged to a reactor, the untreated catalyst (250 c.c.) being on top and the fluoride-treated catalyst (250 c.c.) being at the bottom (i.e. outlet) part of the reactor.  A light virgin naphtha with an octane number of 64 was passed, together with 2.5 mols. of hydrogen, through the reactor at 950 DEG F.  An 87 volume per cent. yield of debutanized gasoline was obtained having an octane number of 77. Other examples relate to the use of catalysts containing molybdenum oxide for the hydroforming of naphthas.