Catalytic Performance of Modified HMCM‐22 Catalysts in Xylene Isomerization

Abstract HMCM‐22 catalysts modified with La 2 O 3 (5% La) and MgO (≈0.87% Mg) were prepared respectively by impregnation method, and were characterized by scanning electron microscopy, X‐ray diffraction, N 2 physical adsorption‐desorption and temperature‐programmed desorption of NH 3 . The effect of supported metallic oxides (La 2 O 3 , 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 H 2 , WHSV 4 h −1 and H 2 /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%.