Catalytic Performance of Modified HMCM-22 Catalysts in Xylene Isomerization

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• 作者：Xiang Wu ; Chao Hu ; Guoqing Zhao ; Ying Yuan and Zhirong Zhu
• 刊名：Chinese Journal of Chemistry
• 出版年：2016
• 出版时间：December, 2016
• 年：2016
• 卷：34
• 期：12
• 页码：1291-1296
• 全文大小：487K
• ISSN：1614-7065

文摘

HMCM-22 catalysts modified with La₂O₃ (5% La) and MgO (≈0.87% Mg) were prepared respectively by impregnation method, and were characterized by scanning electron microscopy, X-ray diffraction, N₂ physical adsorption-desorption and temperature-programmed desorption of NH₃. The effect of supported metallic oxides (La₂O₃, MgO) on catalytic performance in xylene isomerization of C8 aromatics (ethylbenzene, m-xylene and o-xylene) was investigated in detail. The experimental results showed that 5% La/HMCM-22 catalyst had higher isomerization activity and stronger shape-selectivity than 0.87% Mg/HMCM-22 catalyst, owing to its more acid sites and smaller pore size. And the loading amount of La was optimized to be about 7%. Moreover, supporting metal over 7% La/HMCM-22, respectively with 0.3% Pt, 3% Ni and 3% Mo, was carried out to prepare bifunctional isomerization catalysts. In comparison, 3% Mo/7% La/HMCM-22 showed the best catalytic performance with both high activity and high selectivity, with the low hydrocracking of m-xylene and o-xylene. Besides, the optimal reaction conditions were found: 340°C, 1.5 MPa H₂, WHSV 4 h⁻¹ and H₂/C8 4 mol/mol. Under the above conditions, ethylbenzene conversion was up to 20%, para-selectivity was over 23% with low xylene loss of 2.9%.