Hydrothermal Synthesis Of Highly Dispersed Beta Zeolite Nanocrystals With Silylated Seeds

In the field of supercritical cracking for endothermic hydrocarbon fuels，the zeolitecatalyst coating significantly increases heat transfer resistance, and easily leads tocoke deactivation. However, dispersing the zeolite in hydrocarbon fuels to form auniform system, the―quasi-homogeneous‖catalytic cracking occurs in the reactiontube, without increasing the heat transfer resistance. After the reaction, the catalystdischarged with fuels, which improved the conversion rate. In this paper, nano-Betazeolite was synthesized from organofunctionalized seeds, and the optimal conditionof the synthesis, the effect of grafting reagents and extraction in template removalwas studied.The optimal condition of the preparation of nano-Beta zeolite was determined bychanging temperature, time and the amount of SDA. Temperature at too high or toolow is not conducive to the formation of the nano-Beta zeolite, and the optimumtemperature is of135℃to150℃. Increase the amount of SDA can shorten the timeof the formation of zeolite nucleus, improve crystallinity of the zeolite, and reducethe size of the particles and aggregates which leads to better dispersion ability.Taking PHAPTMS as grafting reagent, the regulation to the size of the particlesand dispersion ability was investigated. Furthermore, the influence of the chainlength of the alkyl groups and the amount of the reagent added in was examined. Thesize was decreased, and the crystallinity, specific surface area and dispersion abilitywere increased, when compared funtionalized zeolite with zeolite without grafting.And with the growth of the chain length of the reagent, its regulation to the particlesize is increased, resulting in smaller particles and higher crystallinity, but thegrafting rate is reduced and the surface area decreased, which is caused by hindranceof the long chain. The dispersion property of the particles is co-regulated by thegrafting rate and chain length, higher grafting rate and longer chain leading to abetter dispersion. Moreover, the addition of the alkyl reagent has a suitable amount,too much will reducing the grafting ratio, so as to the crystallinity, specific surfacearea and dispersion ability.Taking acetate as the extraction agent, the extraction temperature and theconcentration of the extraction agent were studied, and by comparison withcalcinations the advantage and disadvantage of the two methods was investigated.Both of the extraction temperature and the concentration of the extract agent bothhas a suitable value, too high will causing the destruction of the structure of thezeolite and too low reducing the extraction rate, and the optimum extractioncondition is extracting with50wt%aqueous acetic acid under60-80℃. Comparedwith calcinations, extraction doesn’t affect the crystallinity and avoids irreversibleaggregates of the particles caused by calcinations, which is significant for dispersingthe zeolite particles into an organic phase. However, the effect of SDA removing forextraction is far lower than that of calcinations.