CONVERSION OF LIGHT PARAFFINS FOR PREPARING SMALL OLEFINS OVER ZSM-5 ZEOLITES

The conversion of C-3-C-9 paraffins to small olefins over ZSM-5 zeolit e is investigated. The small olefins are primary products and are usua lly converted into other more stable secondary products such as aromat ics on the ZSM-5 zeolites. Thermally treated HZSM-5, K/HZSM-5 and Ba/H ZSM-5 catalysts were developed and favourable oxidative conditions wer e introduced for the conversion process to maximize selective conversi on of light paraffins to small olefins at the relatively low temperatu re of 873 K. The role of K and Pa is to minimize bimolecular hydrogen transfer reactions and enhance the dehydrogenation activity of the cat alysts. Meanwhile, the oxygen in the gas phase is effective to improve the olefin selectivity and yield. C-2-C-4 olefin selectivities of 70. 4 and 66.8% have been obtained for propane and n-hexane feedstocks, re spectively, at a temperature of 873 K.