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.
Arakawa, H, Aresta, M, Armor, JN, Barteau, MA, Beckman, EJ, Bell, AT, Bercaw, JE, Creutz, C, Dinjus, E, Dixon, DA, Domen, K, DuBois, DL, Eckert, J, Fujita, E, Gibson, DH, Goddard, WA, Goodman, DW, Keller, J, Kubas, GJ, Kung, HH, Lyons, JE, Manzer, LE, Marks, TJ, Morokuma, K, Nicholas, KM, Periana, R, Que, L, Rostrup-Nielson, J, Sachtler, WMH, Schmidt, LD, Sen, A, Somorjai, GA, Stair, PC, Stults, BR, Tumas, W (2001) Chem Rev. 101:953.