Catalyst discrimination for olefin production by coupled methanol/n-butane cracking

Abstract

The joint transformation of n-butane and methanol has been studied on catalysts prepared based on HZSM-5 zeolites (with different SiO 2/Al 2O 3 ratios and doped with Ni) and SAPO-18. A methanol/n-butane molar ratio of 3 has been used, which corresponds to an energy-neutral integrated process. The kinetic behaviour of the catalysts has been compared based on C 2–C 4 olefin yield, deactivation by coke deposition for 5 h time on stream and hydrothermal stability by operating in reaction–regeneration cycles. The results show a good performance of the catalyst prepared based on HZSM-5 with SiO 2/Al 2O 3 = 30, which has high levels of acidity and acid strength (≥120 kJ mol NH 3 −1). This catalyst allows obtaining 24.4% of C 2–C 4 olefin yield (11.5% of propene), with a selectivity of 43% at 575 °C and a space time of 1.1 g cat h mo l C H 2 − 1 . The catalyst fully recovers its initial kinetic behaviour after 10 reaction–regeneration cycles.