GB709929A - Improved reforming catalysts - Google Patents

Abstract

Reforming catalysts for the treatment of hydrocarbons comprising molybdenum oxide or sulphide on an alumina containing support such as activated alumina or zinc aluminate spinel have incorporated therein 0.45 to 2.7 per cent. by weight of a fluoride, calculated as HF, based on the total weight of the catalyst. The catalyst which may have 5-30 per cent. molybdena can additionally contain Group 2 metal compounds such as CaO, ZnO or MgO, preferably 0.5-5 weight per cent., together with zirconia or silica. The fluoride activation with for example hydrofluoric acid, ammonium fluoride or hydrofluosilicic acid, above its decomposition temperature, may be effected by impregnation at temperatures up to 200 DEG F. during the formation of the base before impregnating with molybdena or to the whole catalyst before or after calcination. It may also be effected in the reactor in which case gaseous fluoride at temperatures up to 950 DEG F. may be added to the feed at any point in the reforming cycle, preferably in the presence of water or water vapour. A fixed bed is preferably activated by passing the fluoride in a direction opposite to the direction of the hydrocarbon feed. The catalyst may be formed into pills or pellets before or after calcining, with or without graphite, starch, solid vegetable oil or fat. If used in a fluidized bed the particles should be below 500 microns, preferably 10-200 microns with a major proportion in the 20-80 micron range. The catalysts may be employed at 0.300 p.s.i.g. pressure at temperatures from 750-1150 DEG F. in catalytic reforming either where hydrogen or refining light gases are added or where process gases are recycled. If hydrogen is added the hydrogen/hydrocarbon mol ratio may be from zero to 10/1 preably 1/1 to 4/1. Examples, which each give comparative data in a reforming operation on virgin naphthas at 215 p.s.i.g., 900 DEG F., 1.2 liquid V/V/Hr., and 2/1H2/naphtha mol ratio between the catalyst of the invention and a similar one without fluoride activation include (1) alumina gel precipitated from iron-free aluminium sulphate with ammonium hydroxide at a final pH of 9.5-10, washed and mulled with acetic acid, was treated with aqueous hydrofluoric acid, dried, and calcined a 750 DEG F. It was then powdered, treated with ammonium molybdate, dried, calcined and filled with graphite. The final composition was 89.8 Al2O3, 10.2 MoO3, 1.8 HF. (10) The alumina gel was prepared as in Specification 663,128 by dissolving aluminium in amyl alcohol and hydrolyzing, then treated after the manner of (1) above. (13) A fixed bed was treated in situ by a stream of nitrogen which had been passed at 210 DEG F. through a 48 per cent. aqueous HF solution to give a 1.25 weight per cent. HF content in the catalyst. (15) Zinc hydroxide prepared from zinc sulphate and ammonium hydroxide was mulled with alumina prepared as in 10 above and treated as in 1 above to give a composition of 87.6 ZnN.Al3O3-12.4MoO3,-1.75 HF. Further examples compare the effects of substituting ammonium fluoride for hydrofluoric acid in the fluoride range claimed and of incorporating 4.5 per cent. HF. A comparitive example indicates that similar treatment applied instead to chromium containing catalysts is detrimental. The catalysts may be reactivated in situ when the effects of the initial fluoride activation has been lost. Specifications 452,095, 452,158, 528,780, and 616,375, also are referred to.