Study on Isobutane/1-Butene Alkylation Over Phosphorus-Modified HY Zeolite

The present work reports the excellent catalytic performance of phosphorus-modified HY zeolite in the alkylation of isobutane with 1-butene. A series of HY zeolites with different phosphorus-loading were prepared by wet impregnation with diammonium hydrogen phosphate solution and applied to catalyze isobutane/1-butene alkylation at 80 degrees C, 2 MPa, and 3 h(-1). The physicochemical properties of the zeolites were characterized by XRD, SEM, N-2 adsorption-desorption isotherms, ICP-OES, FTIR, NMR, NH3-TPD, and Py-IR. The mechanism of HY zeolite modified by phosphorus was investigated in depth. The results indicated that the phosphorus atoms were incorporated into the zeolite framework and involved in the formation of new Bronsted acid sites. The phosphorus-modified zeolites presented a dramatic rise in the amount of medium-strong Bronsted acid sites and the Bronsted/Lewis ratio. The initial selectivities of C-8 and trimethylpentane obtained on HY-1P (phosphorus-loading of 1 wt%) were up to 75.7 wt% and 53.9 wt% respectively, which were much higher than the values over non-modified HY zeolite. Moreover, the deactivation of the catalyst was appreciably delayed. It was verified that catalyst deactivation was caused by the blockage of pores and the coverage of active sites for the deposition of C-12-C-20 long-chain alkanes. [GRAPHICS] .