Abstract
This study focuses on the modification of ZSM-5 in order to enhance the catalytic cracking of refinery naphtha to produce light olefins. ZSM-5 was metal modified using different loadings (0.5–5 wt%) of Fe and Cr via the impregnation method. The metal modified ZSM-5 samples are compared and the effect of metal loading on the physicochemical properties and catalytic performance is investigated. Fe and Cr modification had an effect on both the physicochemical properties of the catalysts as well as catalytic activity and selectivity. Metal loading caused a decrease in the specific surface area which decreased further with increased metal loading. Fe had a greater effect on the total acidity in particular strong acid sites when compared to Cr. The optimum Fe loading was established which promoted selectivity to olefins, in particular propylene. Fe also had a dominant effect on the P/E ratio of which a remarkable ratio of five was achieved as well as enhanced the stability of the catalyst. Cr was found to be a good promoter for selectivity to BTX products with a two-fold increase observed when compared to Fe-modified catalysts.
Highlights
Production of light olefins such as ethylene and propylene vital to many petrochemical processes has been achieved through steam cracking of hydrocarbons for almost half a century [1]
In this study we examined the use of Fe and Cr modified ZSM-5 as catalysts for the catalytic cracking of naptha obtained from the Chevron refinery to enhance light olefin selectivity
Metal modification with Fe and Cr had an effect on both the physicochemical properties of the catalysts as well as the catalytic performance
Summary
Production of light olefins such as ethylene and propylene vital to many petrochemical processes has been achieved through steam cracking of hydrocarbons for almost half a century [1]. Catalytic cracking of various types of hydrocarbons including naphtha range hydrocarbons has been investigated over ZSM-5 zeolites to produce light olefins. In particular ZSM-5 are active catalysts and/or supports for a range of reactions such as cracking, alkylation, aromatization and isomerization of hydrocarbons, due to their activity, shape selectivity [4, 5], ion-exchanging properties, special three dimensional micropore structure and large specific surface area in ZSM-5 [6, 7] They play a significant part in the olefin industry and in current processes that are under development and modification in order to commercialize these technologies. In this study we examined the use of Fe and Cr modified ZSM-5 as catalysts for the catalytic cracking of naptha obtained from the Chevron refinery to enhance light olefin selectivity.
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