The Influence of Chlorine on the Performance of Pt/Al2O3/Zeolite Y Bifunctional Catalysts

Abstract

Bifunctional metal-acid catalysts are widely applied in the petrochemical industry for the conversion of various hydrocarbon feedstocks into high quality liquid fuels. In a previous study, Pt/Al2O3/Zeolite Y catalysts with a so-called ‘nanoscale’ intimacy between platinum sites and zeolite acid sites were found to be optimal for the selectivity towards desired isomer products. However, the ‘nanoscale’ catalyst was prepared with H2PtCl6 as metal precursor and it is known that the presence of chlorine results in highly acidic Al2O3. Therefore, in this study the influence of chlorine on the catalytic performance of Pt/Al2O3 and Pt/Al2O3/Zeolite Y bifunctional catalysts with ranging intimacies is investigated. Via incipient wetness impregnation and strong electrostatic adsorption, zeolite based bifunctional catalysts were prepared with a mili-, micro- and nanoscale intimacy and varying chlorine content. Furthermore a wide variety of Pt/Al2O3 references were prepared and analyzed with NH3-TPD and pyridine-IR in order to examine the influence of chlorine on the surface acidity. In a flowrence 16 parallel fixed bed reactor set-up, the catalytic performance of the bifunctional catalysts and reference samples was examined in the conversion of n-heptane. The obtained results indicate that chlorine does not have significant effect on the catalytic performance of the zeolite based microscale and nanoscale bifunctional catalysts. Furthermore, observed differences in catalytic performance of the Pt/Al2O3 references were, besides the chlorine content, mainly caused by a variety in the average platinum nanoparticle size.