Synthesis And Application Of The Mesoporous Molecular Sieve

Mesoporous molecular sieve is an important kind of ordered mesoporous materials, ithas many excellent features: large specific surface area and pore volume, pore structureorderliness and can be adjusted and controlled between2-50nm; And by optimizing reactionconditions or after post-processing can improve the thermal stability and hydrothermalstability of molecular sieves; Rules of particle shape and structure of ordered pore in themicron range. Therefore, it has the very good ion exchange performance, adsorptionseparation performance and good catalytic performance, in catalytic cracking, It has potentialapplications in many fields, such as catalytic cracking, fine chemical, membrane separationtechnology and so on.In this paper, with ethyl silicate (TEOS) as silica source, hexadecyl trimethyl ammoniumbromide (CTAB) and P123as the template, the MCM-41, Al-MCM-41, SBA-15mesoporousmolecular sieve were synthesize by sol-gel method and hydrothermal synthesis method andcharacterized. The influence on the pore morphology and the aperture size by addingpolymers (PEG, PVP) to mesoporous molecular sieve was studied. Then as catalyst carrier toload Fe2O3, they were applied in the reaction of ethyl benzene catalytic dehydrogenation tostyrene. The influence of different load catalyst on ethylbenzene dehydrogenation reaction,cocatalyst K addition on the reaction of ethylbenzene dehydrogenation, and the influence ofreaction temperature on catalyst performance were studied. Last, the activity keeping time ofcatalysts was discussed.Experimental results were showed as follows:(1) after the molecular sieves werecharacterized by XRD and N2-stripping absorption, they were proved to be typicalmesoporous materials and the degree of crystallinity was better.(2) PEG and PVP couldimprove Al-MCM-41mesoporous molecular sieve dispersion, increase the pore volume andspecific surface area; the degree of order of mesoporous structure was improved by added theamount of polymer.(3) Mesoporous molecular sieve as catalyst support to load Fe2O3, whenthe load is60%, ethylbenzene conversion rate and selectivity of styrene were the highest. Atthe same time, to add Al to help improve the catalytic performance of Fe2O3/MCM-41, whennSi/nAl is60, catalytic performance was best. After added potassium, pure Fe2O3catalyticperformance was increased, and the performance of catalyst with molecular sieve as thecarrier was decreased. Fe2O3/SBA-15could keep longest activity time in the three kinds ofcatalysts. When the temperature was630oC, the catalysts had the optimal performance.