日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Small-pore zeolites composed of 8-memberd ring windows are one of the most attractive structure series of zeolites. They exhibit high catalytic performance in the selective catalytic reduction of NOx with ammonia for purification of diesel emission and the light olefin production from methanol. As these processes are performed at high reaction temperatures in the presence of steam, however, an improvement in the thermal and hydrothermal resistance of zeolites is a critical issue for developing high-performance zeolite catalysts with high catalytic activity and selectivity. Here we report syntheses of phosphorus-modified small-pore zeolites with high thermal/hydrothermal stability by hydrothermal conversion of FAU zeolite in the presence tetraalkylphosphonium cations as both organic structure directing and phosphorus modifying agents. We succeeded in synthesizing various phosphorus-modified small-pore zeolites with different framework structures and the phosphorus modification degree could be controlled. It was also found that the phosphorus-modified small-pore zeolite catalysts exhibited good catalytic durability and hydrothermal stability on NH₃-SCR process.