Secondary cracking suppression over zeolite-based catalysts: A review

Secondary cracking reactions are critical challenge in the hydrocracking processes as they increase light distillates yield at the expense of middle distillates which is detrimental to process sustainability. This work provides a comprehensive overview of strategies employed to date to suppress secondary cracking reactions over zeolite-based catalysts for concomitant improvement of middle distillates yield and process sustainability. It also examines primary causes of secondary cracking reactions, explores and reports feasible route to synthesis of more hydrocracking catalysts that can completely suppress secondary cracking reactions at high conversions in three major hydrocracking processes: Fischer-Tropsch wax hydrocracking, plastic waste hydrocracking, and heavy petroleum fractions hydrocracking. By addressing this pivotal topic, the study aims to facilitate future research efforts towards improving the sustainability and efficiency of major hydrocracking processes. Key approaches discussed include the use of mesopore-containing zeolites, unconventional synthesis methods, zeolite composites, and novel zeolitic materials. The review also highlights reaction engineering in mitigating secondary cracking. Overall, this work offers detailed insights that can guide the development of more and advanced hydrocracking catalysts capable of maximizing middle distillates yield through effective suppression of secondary cracking reactions.