Synthesis and determination of the properties of the bifunctional beta zeolite catalysts for n-heptane hydroisomerization

Abstract

In this study, two types of beta zeolites with different Si/Al ratios (11.7 and 24.5) were synthesized hydrothermally using tetraethylammonium hydroxide (TEAOH) as the template. Different amounts of Platinum (0.2%, 0.5% and 1.2%) were loaded on the protonated form of zeolite by incipient wet impregnation method with hexachloroplatinic acid in 0.2N Cl″ progressive ion solutions. Catalytic reactions were carried out at atmospheric pressure in a fixed bed reactor with vertical placing and downward flow at three different temperatures, various WHS V (weight hourly space velocity) and n-H2/n-HC (molar hydrogen / hydrocarbon) ratio (230, 250, 280°C, 1.64, 2.48, 3.28 hr 1 and 6, 10, 14 respectively). Increasing the Si/Al ratio from 11.7 to 24.5 promoted the selectivity and yield. It was found that optimum platinum content depends on the Si/Al ratio (zeolite acidity) present in the zeolite catalyst. The monobranched to dibranched isomers ratio were correlated with a linear function of n-heptane conversion. Such a correlation was found to be valid for various Si/Al ratios, metal content, processing temperature and pressure, WHSV and hydrogen to hydrocarbon ratio. This observation may indicate that in isomerization reactions, the mono-branched isomers are first produced but subsequently transformed into multi-branched isomers. © 2008 Sociedad Chilena de Química.