Mo influence on the kinetics of jatropha oil cracking over Mo/HZSM-5 catalysts

Abstract

The aim of this work is to study the influence of Mo on the kinetics of jatropha oil cracking on HZSM-5 catalysts, in order to select catalytic materials for the production of renewable fuels and hydrocarbons as raw chemicals for the petrochemical industry. Jatropha oil was selected as a model compound of an acidic non edible vegetable oil unsuitable for biodiesel production by conventional transesterification technology. Jatropha oil was used either pure or adsorbed on Mo/HZSM-5 surfaces. A model free kinetics was developed from non-isothermal thermogravimetric experiments of vegetable oil cracking. Fast cracking experiments were performed in a micro-pyrolysis set up, at 650°C, under helium flow, with on line products analysis (GC/MS). Results show that the increase in the Mo content of HZSM-5 induced a decrease of both specific surface area and acidity. Mo also changed the amount and distribution of hydrocarbons obtained during cracking reactions, increasing monoaromatics and decreasing polyaromatics. TG and DTG profiles during decomposition followed by thermogravimetry indicate that the jatropha oil/catalyst mixture led to a sharp decrease in the temperature at which the main mass loss events occurred. The different values obtained for the apparent activation energy of jatropha oil decomposition suggest a different route of reaction in the presence of Mo by comparison with cracking of pure oil.