Phosphorus modified small-pore zeolites and their catalytic performances in ethanol conversion and NH3-SCR reactions

Abstract

Small-pore zeolites, composed of 8-membered ring windows, exhibit high catalytic performances in the selective catalytic reduction of NOx with ammonia (NH3-SCR) and the light olefin production from methanol or ethanol (MTO or ETO). As these processes are performed at high reaction temperatures in the presence of steam, the enhancement of the thermal and hydrothermal resistances of zeolites is essential for the development of high-performance catalysts that retain their high catalytic activity and selectivity. This paper reports on the syntheses of phosphorus-modified small-pore zeolites with high thermal/hydrothermal stabilities, prepared by the hydrothermal conversion of FAU zeolite in the presence tetraalkylphosphonium cations as both organic structure directing agents and phosphorus modifying agents. Several phosphorus-modified small-pore zeolites with different framework structures and a controlled phosphorus modification degree were synthesized. Moreover, it was found that the phosphorus-modified small-pore zeolites exhibit a good catalytic activity and durability in the NH3-SCR and ETO processes even after severe thermal or hydrothermal treatment.