Controlling catalytic and reaction factors for regulating the distribution of aromatic products in n-butane aromatization over Ga/HZSM-5

Abstract

The selective production of benzene, toluene, and xylene (BTX) has the potential to enhance the overall economics of aromatic production and subsequent processes, owing to their differing applications in the petroleum industry. Despite the economic significance of selective BTX production, the individual selectivity of BTX and the corresponding generation mechanisms have not been thoroughly investigated. Therefore, this study aims to explore the factors that affect the distribution of BTX and their respective trends of variation during n-butane aromatization over Ga/HZSM-5. This study demonstrates that selective production can be achieved by controlling the conditions that significantly influence product distribution, including the reaction temperature, extent of catalyst deactivation, and distribution of acid sites. The selectivity for benzene relative to toluene increased with increasing reaction temperature but decreased with increasing catalyst aging time. In addition, Ga/HZSM-5, which had a low Si/Al ratio, exhibited a pronounced preference for benzene. Consequently, it is possible to control benzene to toluene selectivity ratio within a range of 0.5–1.1 while maintaining over 85 % of n-butane conversion by adjusting these key factors. Further results proposed that the distinct role of protolytic cracking over Brønsted acid sites may contribute to the shift in aromatics distribution toward benzene during the series reaction, whereas the dehydrogenation over Ga Lewis acid sites plays a promotional role in the shift toward toluene.