Chemical Modification Of The Shape-selective Functionalization Of ZSM-5 Zeolite For The Catalytic Synthesis Of Para-xylene

The catalytic process for producing para-xylene has been paid much attention and become a quite competitive subject in petrochemical industry. This work is to investigate shape-selective modification of the acidity and structure of ZSM-5 by XRD, IR, NH₃-TPD, Physical adsorption, PGC-MS (pyrolysis gas chromatography-mass spectrometer), MAS NMR, UV-Raman, TGA, Constraint Index, and probe-reactions, with an aim to develop more active and selective catalysts for producing para-xylene via toluene disproportionation and toluene alkylation. Two shape-selective catalysts for toluene disproportionation and toluene alkylation with methanol (toluene methylation) to produce para-xylene were successfully developed by selecting modification methods and modifiers according to the different needs of acidity catalyzing for these reactions.ZSM-5 with SiO₂/Al₂O₃ ratio< 30 was selected for shape-selective catalyst for toluene disproportionation. The direct-method for ZSM-5 synthesis with ammonia was well improved by optimizing template and synthetic conditions. It is found that chemical liquid deposition of silica (SiO₂-CLD) makes ZSM-5 have the best catalytic performance for toluene disproportionation under the approximate selectivity.PGC-MS technology, combining with a high temperature capillary chromatography, was firstly developed to investigate the deposition process of polysiloxane to silica over ZSM-5 in SiO₂-CLD. The results reveal that the composition of decomposd products, including their molecular sizes,is a main factor to cause the modification difference in SiO₂-CLD with different...