Enhanced Hydrothermal Stability obtained fvor in situ Synthesized Micro- and Mesoporous MFI / MCM-41 like Phases

摘要

Micro- and mesoporous MFI / MCM-41 like phases, synthesized using mixtures of C_6H_(13))(CH_3)_3NBr and C_(14)H_(29)(CH_3)_3NBr templates / surfactants, were tested in 100jpercent steam for 5 hours at temperatures of 650, 760 and 815 deg C, respectively. A generally improved hydrothermal stability was observed for the composite samples obtained using this mixture of surfactants in the synthesis gels. The most stable sample synthesized with a C_6H_(13)(CH_3)_3NBr / C_(14)H_(29)(CH_3)_3NBr ratio of 75percent/25percent at a temperature of 175 deg C, consisting of about 10percent MFI and 90percent MCM-41 structure, maintained a N_2-BET surface area (BET-SA) of 243 m~2/g after steaming at 815 deg C, corresponding with a retention of 62percent for this ample, which is very high for regular mesoporous phases. The XRDs and N_2 adsorption isotherms reveal that the typical features of the mesoporous materials (low angle peak in the XRD; inflection point in the N-2-siotherm) are partly maintained. Consequently, this material is an interesting candidate for catalytic cracking and other applications if properly modified.