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 C5 raffinate. The effect of lanthanum content of LaX-P/C-ZSM5 catalysts on their physicochemical properties and catalytic activities for the cracking of C5 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 C5 raffinate, acid and base properties of LaX-P/C-ZSM5 catalysts were closely related to the conversion of C5 raffinate and selectivity for light olefins, respectively. Conversion of C5 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 C5 raffinate.

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► Phosphorous-modified porous ZSM-5 (P/C-ZSM5) catalyst was prepared.
► La-containing P/C-ZSM5 (LaX-P/C-ZSM5) with different La/Al ratio was then prepared.
► Catalytic cracking of C5 raffinate to light olefins (ethylene + propylene) was conducted.
► Yield for light olefins showed a volcano-shaped trend with respect to La/Al ratio.
► Optimal La content was required for maximum production of light olefins.