Authors:Ling Tao, Gui-Sheng Li, Shuang-Feng Yin, Qiang Ou-Yang, Sheng-Lian Luo, Xiao-Ping Zhou and Chak-Tong Au
Described in this paper are the synthesis, characterization and catalytic application of H-ZSM-5 zeolites for the conversion of CH3Br into aromatics. The H-ZSM-5 zeolites were fabricated by hydrothermal crystallization using n-butylamine (BTA) as a template and characterized by XRD, SEM and NH3-TPD techniques. The effects of batch SiO2/Al2O3 ratio, alkalinity, NaCl/Al2O3 ratio, seed crystals, and crystallization time on the yield, structure/texture and catalytic performance were systematically studied. Adopting the optimum sol (SiO2/Al2O3 = 70, BTA/SiO2 = 0.2847, Na2O/SiO2 = 0.1237, H2O/SiO2 = 37.4, NaCl/Al2O3 = 60, and seed/SiO2 = 5 wt%) and under the most preferable crystallization conditions of 100 °C/24 h–170 °C/24 h, H-ZSM-5 zeolites of high crystallinity and small size (300–700 nm) were obtained. Good catalytic performance was observed over the H-ZSM-5 zeolites (aromatic yield up to 44.2%). However, unlike the modification of large commercial HZSM-5, the use of MoO3 or PbO as modifying agents for the small-size H-ZSM-5 zeolites results in a decline of catalytic performance. The relationship between the structure and the catalytic efficiency of as-synthesized H-ZSM-5 samples were investigated. It was found that with crystallinity enhancement and/or decline in crystal size, there is improvement of catalytic performance.