GB858858A - Relating to treatment of platinum catalyst - Google Patents

Abstract

Platinum catalysts supported or dispersed on a carrier and containing absorbed and/or combined oxygen are reconditioned by treatment with a gaseous mixture containing hydrogen carried out at least initially in a zone maintained at a hydrogen partial pressure of 0.01 to 5 p.s.i.a. and at at least 400 DEG F. The treatment is particularly applicable to platinum catalysts which have been regenerated by treatment with a gaseous mixture containing oxygen at 400 to 1200 DEG F. to remove carbonaceous contaminants resulting from its use in hydrocarbon conversion processes such as hydroforming, dehydrogenation, isomerisation, desulhpurisation, hydrogenation and dehydrocyclisation. In such processes the hydrocarbon is contacted with the platinum catalyst at about 400 DEG to 1100 DEG F. and up to about 2500 p.s.i.g. with a weight space velocity of 0.01 to 40. In some processes hydrogen can be added at the rate of 500 to 20,000 s.c.f. (measured at 60 DEG F. and 760 mm. Hg)/bbb oil, e.g. in hydroforming naptha at 750 DEG to 1050 DEG F. and 25 to 1000 p.s.i.g. with a weight space velocity of 0.1 to 15 using 1000 to 10,000 s.c.f. H2/bbb oil. The catalyst may contain 0.05 to 20% wt. of platinum which is dispersed on a carrier, e.g. an inorganic oxide such as alumina, silica, silica-alumina, magnesia, kieselguhr, pumice or zinc aluminate spinel or activated charcoal. The catalyst is treated with hydrogen for 5 minutes to 5 hours at not more than 950 DEG C. The treatment may be carried out in two stages with the following conditions:-(a) a hydrogen partial pressure of 0.05 to 5 p.s.i.a., 400 to 825 DEG F., 10 minutes to 2 hours; (b) a hydrogen partial pressure of 6 to 50 p.s.i.a., a temperature 50 to 400 DEG F. higher than in (a) subject to a maximum of 950 DEG F., 15 minutes to 3 hours. The oxidative regeneration of catalyst preceding the reconditioning can be effected initially with nitrogen diluted air (0.5% mol O2) at 500 DEG F. and then increasing the proportion of air and also the temperature until undiluted air is used at 1000 DEG F. The regeneration may also be effected by a two stage process under the following conditions:-(a) 0.5 to 10 hours, 400 to 700 DEG F. and 0 to 50 p.s.i.g. with a gas containing 0.05 to 2% mol O2, and (b) 5 to 40 hours and 750 to 950 DEG F. with the same gas. In an example the efficiency of a catalyst regenerated by the first method and recondition at 500 DEG F. with a nitrogen/hydrogen mixture having a hydrogen partial pressure of 0.075 p.s.i.a. for 30 minutes is compared with a similar catalyst reconditioned with undiluted hydrogen (=14.7 p.s.i.a.) at 800 DEG F. for 1 hour with reference to the improvement in octane number of a 236-425 DEG F. petroleum fraction containing 9% vol. aromatics, 1% mol olefins and 0.05% wt. sulphur by hydrogenation at 940 DEG F., 200 p.s.i.g., an hourly weight ratio of oil/catalyst/hour of about 45 and about 3 mols H2/mol feed.