Phosphorus-doped Y zeolites for increasing mesopore and Lewis acid in high-efficiency denitrogenation

Micro-mesoporous zeolite shows great potential in the field of fuel denitrogenation. However, the current preparation method of zeolite with composite pores still has the problems of high cost and low denitrification rate. Herein, we prepared a low-cost phosphorus doped zeolite by directly impregnated Y zeolite in phosphoric acid and calcinated at 400 °C firstly. Experimental results showed that phosphorus doped 10 wt.% PA/MY provided optimum denitrogenation performance with denitrogenation rate as high as 97% compared to unmodified MY zeolite (21.11%) and ion exchanged 1.0 MHY zeolite (91.38%). What's more, it was found that the introduction of phosphorus led to the formation of P–O tetrahedra and Al–O–P bonds in zeolite, which increased the amount of mesopore and the Lewis acid in zeolite. Meanwhile, the comparative study found that ion exchanged MHY zeolite depended on the limited pore matching effect of micropores and nitrogen-containing molecules and the chemisorption reaction of non-regenerable Brøsted acid to achieve denitrogenation performance. However, phosphorus doped zeolite PA/MY not only had a better size matching effect between the mesopore and the size of nitrogen-containing molecules, but also had more Lewis acid to play a major role in denitrogenation. The Lewis acid on PA/MY zeolite also had the advantage of being easy to regenerate by desorption of the nitrogen-containing molecules absorbed. This study showed good prospects for the industrial application of the doped zeolite.