Catalytic cracking of C5 raffinate to light olefins over lanthanum-containing phosphorous-modified porous ZSM-5: Effect of lanthanum content

Lanthanum-containing phosphorous-modified porous ZSM-5 catalysts (LaX-P/C-ZSM5) were prepared with a variation of La/Al atomic ratio (X=0.3, 0.7, 0.9, and 1.2) for use in the production of light olefins (ethylene and propylene) through catalytic cracking of C-5 raffinate. The effect of lanthanum content of LaX-P/C-ZSM5 catalysts on their physicochemical properties and catalytic activities for the cracking of C-5 raffinate was investigated. It was found that acidity of LaX-P/C-ZSM5 catalysts decreased with increasing lanthanum content, while basicity of LaX-P/C-ZSM5 catalysts increased with increasing lanthanum content. In the catalytic cracking of C-5 raffinate, acid and base properties of LaX-P/C-ZSM5 catalysts were closely related to the conversion of C-5 raffinate and selectivity for light olefins, respectively. Conversion of C-5 raffinate decreased with decreasing acidity of the catalyst and selectivity for light olefins increased with increasing basicity of the catalyst. Among the catalysts tested, La0.7-P/C-ZSM5 catalyst with moderate acidity and basicity exhibited the best catalytic performance in terms of yield for light olefins. It is concluded that an optimal lanthanum content of LaX-P/C-ZSM5 catalysts was required for maximum light olefin production in the catalytic cracking of C-5 raffinate. (C) 2012 Elsevier B.V. All rights reserved.