TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred composition: The zeolite is L-zeolite. The group VIII metal or metal oxide consists of platinum, platinum oxides or mixture, and the group IVA metal or metal oxide consists of tin, tin oxides or mixture. The L-zeolite is impregnated with platinum and tin. The weight ratio of promoter to L-zeolite is 0.001:1 - 0.1:1, preferably 0.001:1 - 0.1:1. The wt.% of promoter in composition is 0.01 - 50%, preferably 0.1 - 10%.Preferred materials: Group IVA compound is preferably a group consisting of tri-n-butyltin acetate, n-butyltin trichloride, di-n-butyldiphenyltin, di-n-butyltin diacetate, di-n-butyltin dichloride, di-t-butyltin dichloride, di-n-butyltin dilaurate,dimethyldiphenyltin, diphenyltin dichloride, hexa-n-butylditin, hexamethylditin, hexaphenylditin, methyltintrichloride, phenyltintrichloride, tetra-n-butyltin, tetraethyltin, tetramethyltin, tetraphenyltin, tetra-i-propyltin,tetra-n-propyltin, tin acetate, tin bromide, tin chloride, tin oxalate, tin sulphate, or tin sulphide.Group VIII compound is preferably a group consisting of chloroplatinic acid, platinum chloride (platinic chloride), platinum bromide, platinum iodine, tetramine platinum chloride. tetramine platinum nitrate, tetramine platinum hydroxide, or tetrachlorodiamine platinum. EXAMPLE - (1) 10.91 g of the zeolite was mixed at 25degreesC with 4.67 g of an acetone solution which contained 1.0 wt.% chloroplatinic acid and 1 wt.% tri-n-butyltin acetate to impregnate both tin and platinum onto the zeolite. The resulting mixture was extruded to 1/16 inch extrudates and then calcined at 538degreesC for 6 hours in a muffle furnace (air) to produce 10.36 g of a calcined    platinum-tin-promoted zeolite or Pt-Sn/zeolite containing 0.171 wt.% platinum and 0.153 wt.% tin by calculation (catalyst A).    (2) 21.0 g of the L-zeolite was treated with 11.11 g of a solution containing 1 wt.% CPA, 0.5 wt.% SnCI22H2O, 9.85 wt.% HCI, and 88.65 wt.% H2O under incipient wetness condition to impregnate CPA and tin chloride onto the zeolite followed by calcination at 538degreesC for 6 hours to produce 19.97 g of a platinum-tin-promoted zeolite (catalyst B) containing 0.21 1 wt.% of platinum and 0.146 wt.% tin by calculation.    (3) 5 g of the L-zeolite was well mixed with 1.95 g of a 1.0 wt.% tri-n-butyltin acetate solution (in cyclohexane) in a jar at 25degreesC to impregnate tri-n-butyltin acetate onto the zeolite followed by air drying at 25degreesC to no apparent excess moisture. The resulting mixture in a U-tube was treated with steam at 650degreesC for 6 hours to produce 4.72 g of steamed product which was subsequently treated with 2.89 g of a 1.0 wt.% CPA solution in 1 wt.% HCI to impregnated CPA onto the zeolite. After being calcined at 538degreesC for 1 hour, 4.47 g of platinum and tin-incorporated zeolite containing 0.140 wt.% tin and 0.246 wt.% platinum by calculation (catalyst C) was produced. Catalyst C had a Sn:Pt atomic ratio of 0.935.    In a separate run, 5 g of the L-zeolite was well mixed with 1.95 g of the 1 wt.% tri-n-butyltin acetate solution (in cyclohexane) to impregnate tin onto the zeolite followed by calcination for 6 hours at 538degreesC to produce a calcined product which was subsequently treated with 2.83 g of CPA solution described above for catalyst C production to produce 4.57 g of platinum and tin-promoted zeolite (catalyst D). Catalyst D contained 0.137 wt.% tin and 0.235 wt.% platinum by calculation (Sn/Pt=0.958).    Catalyst E was a catalyst produced by the process (1) except that the platinum and tin content of catalyst E were: 0.6 wt.% platinum and 1.2 wt.% tin.    These zeolite compositions were then employed, in a hydrocarbon conversion process for converting a hydrocarbon feed to an olefin. The feed in these runs was n-butane.    A stainless-steel reactor tube (inner diameter 0.75 inch; length 20 inches) was filled with a 20 ml bottom layer of Alundum(RTM) zeolite (inert, low surface area zeolite), one of the catalysts (in 1/16 inch extrudates) in the center position 5 ml, and a 20 ml top layer of Alundum(RTM) zeolite. The catalysts were pretreated with hydrogen (33 min.) at 550degreesC (starting at 25degreesC then ramping at 10degreesC./min.) for one hour. The feed was then introduced into the reactor at a rate of about 6 litres/hour. Hydrogen was introduced into the runs with catalysts A, C. and D resulting in the mole ratio of H2/n-butane of 2.787, 0.223, and 0.203 for catalyst A. catalyst C, and catalyst D, respectively. No hydrogen was employed in the run with catalyst B. The reaction temperature was 545 - 552degreesC and the reaction pressure was 15 psig. The reactor effluent was cooled and analysed with an on-line gas chromatograph at intervals of about 1 hour. The results at 5.92 hours (catalyst A), 6.23 hours (catalyst B) 6.12 hours (catalyst C), and 5.65 hours (catalyst D).