HYDROCONVERSION OF N-HEXANE OVER PLATINUM SUPPORTED ZEOLITE CATALYSTS PREPARED BY SUPERCRITICAL TECHNIQUE

 Two types of synthetic crystalline zeolites have been used as supports for noble-metal catalysts, namely HZSM-5 and H-Mordenite with SiO ratios of 90 and 40 respectively. The cations, Barium and Strontium zeolite forms were prepared by twice repeated ion-exchange with appropriate chloride solution of 3 normality at pH 7.2 and 50oC. The modified zeolites were dried at 110oC and calcined at 450o C by step wise temperature increase. The ion-exchange by strontium was more effective than by Barium cation. While the ability of H-replacement at HMOR was higher than in case of HZSM-5. The loading of noble metals on all considered zeolite forms were carried out in supercritical carbon dioxide as solvent. Mono-di- and trimetallic catalysts were prepared with Platinum, Ruthenium and Zirconium as acetylacetonate compounds. Platinum was loaded using PtMe COD for Mono metallic loading, whereas this compound are very soluble in supercritical carbon dioxide (scCO22), the other noble metal compounds contains acetylacetonate have low solubility in scCO, therefore 10% of methanol was added to increase the polarity of scCO22  This relatively modern technique is used in the present work for the first time, to load of noble metals on zeolite 2/Al2O3 catalysts for hydroconversion of hydrocarbons. The percent metal loading was affected by increasing the pressure,reaching to about 87 % at 300 bar and 100oC. High pressure increases the
polarity and density of scCO  and gives high ability for dissolving the substrate and penetration through the zeolite pores. Temperature increase has a little effect on loading ability and there has been no significant increase of loading values after 24 hr contact time.