Influence of Calcination Temperature on the Stability of Fluorinated Nanosized HZSM-5 in the Methylation of Biphenyl

Author： Wang Yanan Guo Xinwen Zhang Chen Song Fengling Wang Xiangsheng Liu Hai-ou Xu Xiaochun Song Chunshan Zhang Weiping Liu Xiumei Han Xiuwen Bao Xinhe

Publisher： Springer Publishing Company

ISSN： 1011-372X

Source： Catalysis Letters, Vol.107, Iss.3-4, 2006-03, pp. : 209-214

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Abstract

A series of fluorinated nanosized HZSM-5 catalysts were prepared by impregnating the zeolite with NH₄F solution. The samples were characterized by XRD, XRF, FTIR-Py, TPD, ²⁷Al and ²⁹Si MAS-NMR. The effect of calcination temperature on the structure and acidity was studied in the range of 400–500 °C. When the calcination temperature increases, more framework aluminum atoms are removed due to the fluorination. As a result, the number of acid sites and the acid strength decrease, but the ratio of the total Brönsted acid sites to the total Lewis acid sites (B_T/L_T) increases. The fluorinated nanosized HZSM-5 catalysts exhibit better stability in the methylation of biphenyl (BP) with methanol. Moreover, the stability increases with the increase of the calcination temperature. When the fluorinated nanosized HZSM-5 is calcined at 500 °C, the conversion of BP can keep at about 10% for 50 h. The enhancement of stability may be due to the decrease of the acid strength and the increase of the ratio of B_T/L_T.