Hydrocracking with Chlorinated Platinum-Alumina Catalysts for Liquefied Petroleum Gas Production Joseph P. Giannetti, Howard G. Mcllvried, and Raynor T. Sebulsky Process Research Division, Gulf Research & Development Co., P. 0. Drawer 2038, Pittsburgh, Pa. 15230 Specially chlorinated platinum-alumina catalysts are active for hydrocracking light hydrocarbons at temperatures well below those required with conventional hydrocracking catalysts. These highly active catalysts are prepared by reaction of platinum-alumina first with hydrogen chloride, then with a sulfur chloride or a mixture of sulfur dioxide and chlorine, and finally by giving the catalyst another hydrogen chloride treatment. Pentane, hexane, and a pretreated light naphtha have been hydrocracked between about 400" and 550°F. Single-pass LPG yields of 76, 84, and 102 volume Yo were obtained at the upper end of the temperature range for the pentane, hexane, and naphtha feeds, respectively. Conventional hydrocracking catalysts require temperatures of about 900" F. for equivalent results.
PROPANE
and butane are being used in ever-increasing quantities by the petroleum and petrochemical industries. As liquefied petroleum gas (LPG), they provide a fuel of high heating value which finds wide use as bottled gas, as an additive for town gas, and a motor fuel in farm and commercial vehicles (Collins, 1968; Henke et al., 1967; Scott and Paterson, 1968). I n addition, LPG is the starting material in the manufacture of a large array of petrochemicals. Because of the growing importance of LPG and because existing supplies may be inadequate in some areas, it is desirable to have a process for converting heavier hydrocarbons to LPG. In fact, catalytic hydrocracking is utilized in Japan for LPG production (Gould et al., 1967; Henke et al., 1967; Mathews et al., 1967; Scott and Paterson, 1968). However, with conventional catalysts high temperatures are required, especially when pentane and hexane are hydrocracked. This difficulty was partially overcome by workers at Texaco (Estes, 1966) and British Petroleum (Goble and Fletcher, 1966), who showed that much lower temperatures are possible when chlorinated platinumalumina catalysts are employed. Chlorine is introduced into these catalysts by reaction with carbon chlorides, carbon tetrachloride being particularly effective. Our studies have shown that the manner in which the catalyst is chlorinated has a very significant effect on its activity. By using the proper technique, it is possible to produce a catalyst exhibiting cracking activity considerably greater than that reported by previous investigators. A number of chloriding agents in addition to those previously reported are effective-for example, sulfur chlorides or a mixture of sulfur dioxide and chlorine produce very active catalysts.
Experimental
Materials. Sulfur monochloride (SpClp) and carbon tetrachloride (CCL) were obtained from the Eastman Kodak Co. and used as received. Sulfur dioxide, hydrogen chloride, and chlorine were obtained from the Matheson Chemical Co. and also used as received. Pentane and hexane were Phillips Petroleum Co. technical grade. The pentane contained 3.0 weight % isopentane (2-methylbutane) and 0.3 weight YO cyclopentane, while the hexane contained 3.0 weight 72 methylcyclopentane and 0.7 weight % ' 3-methylpentane. Both were dried and desulfurized over Linde 1 3 molecular ~ sieves. The naphtha was a CS to Cs cut from Kuwait crude oil. The fraction was pretreated over a sulfided nickel-tungsten-on-alumina catalyst a t 650" F., 1800 p.s.i.g., 2 LHSV (liquid hourly space velocity defined as milliliters of hydrocarbon feed per milliliter of catalyst per hour), and 5000 standard cubic feet of hydrogen per barrel. The analyses of this treated fraction are shown in Table I. Hydrogen supplied by the Air Reduction Co. was deoxygenated and dried over Linde 13x molecular sieves. The platinum-alumina used in the catalyst preparation was Sinclair-Baker RD-150 reforming catalyst containing 0.58 weight % platinum. Before use, this material was broken to 12- to 20-mesh (U.S. sieve series) and conditioned by calcining in air a t 550" F. overnight, and then a t 900°F. for 2 hours. This was followed by a reduction for 2 hours a t atmospheric pressure in flowing hydrogen a t 900" F., employing 1.6 standard cubic feet of hydrogen per hour per 100 grams of platinum-alumina. Catalyst Preparations. Three catalysts were made from the above platinum-alumina. The preparations were Ind. Eng. Chem. Process Des. Develop., Vol. 9,No. 3, 1970 473
Table I. Inspections of Hydrofined CSto Cs Kuwait Naphtha Fraction Sulfur, wt. % Nitrogen, p.p.m. Hydrocarbon analysis, wt. % Isobutane n-Butane Isopentane n-Pentane
cs-cs
Hydrocarbon group type analysis, vol. % Paraffins Cycloparaffins Benzene
