A strategy to improve the para-selectivity in toluene methylation on P2O5-ZSM-5 modified by the para-xylene placeholder method

This paper reports a new method of modifying selectively the external surface of ZSM-5 nanoparticles with phosphide, which does not affect the microchannels and the acid centers inside the channels, resulting in a high activity. With H-ZSM-5 as the matrix, the modified catalysts can be obtained in six consecutive steps, where the most critical issues are the selection of placeholder molecules and the temperature for selective removal of the molecules. The results show that the catalysts made by the selective modification method have higher para-selectivity and better activity in comparison to the ones made by the other methods.