HYDROISOMERIZATION OF n-PARAFFINS OVER METAL LOADED MESOPOROUS MOLECULAR SIEVES

Abstract

Microporous zeolites are widely used commercial catalysts, but their applications are intrinsically limited by their small channel diameters. Recent progress in overcoming this limitation has led to the exploitation of the ordered mesoporous materials. These mesoporous materials have pore diameters of 20-60 A° and exhibit catalytic properties for the catalytic conversion of bulky reactants, but unfortunately, when compared with microporous zeolites, the catalytic activity and hydrothermal stability are relatively lower. This severely hinders their practical applications. In the present work, highly ordered hexagonal mesoporous aluminosilicates (MAS-5) with uniform pore sizes have been successfully synthesized from assembly of preformed aluminosilicate precursors with cetyltrimethylammonium bromide (CTAB) surfactant. Mesoporous MAS-5 shows extraordinary stability. The prepared MAS-5 has high surface area of 756 m2/g with a pore size of 20 A. Temperature-programmed desorption of ammonia shows good acidic strength of MAS-5. The properties of MAS-5 have been studied for the n-decane hydroisomerization-hydrocracking reaction. The hydrogenation-dehydrogenation function has been provided by supporting platinum on the MAS-5 surface. A study of the product distribution based on different criteria used in the n-decane reaction test allowed exclusion of the presence of ZSM-5 domains in the structure of the precursor mesoporous material. The kinetic tests show an apparent activation energy value of 115 KJ/mol which is in conformity with those reported in literature