The Synthesis Of Hexagonal Mesoporous Silica(HMS) And Its Performance For Desulfurization

With the worldwide concern for the environment, environmental regulations ondiesel sulfide content requirements become more demanding. It is crucial to developefficient desulfurization method. Mesoporous molecular sieve HMS, due to itsexcellent properties has become a hotpot in the field of catalysis, also exhibits bettercatalytic performance in the catalytic oxidative desulfurization of diesel oil. We usethiophene to simulate sulfur compounds in diesel oil in this paper and the researchobject is a simulated oil with n-octane as solvent.We have synthesizedTi-HMS andZn-HMS molecular sieves by using hydrothermal synthesis method and examines theinfluence of the synthetic conditions on the structure of molecular sieve and theinfluence of synthesis conditions and reaction conditions on desulfurizationefficiency.Main content of this thesis are summarized as follows:ⅠThe preparation of Ti-HMS molecular sievesTi-HMS mesoporous molecular sieves were prepared with using neutraldodecylamine（DDA） as template and tetraethyl orthosilicate（TEOS） as Si source byhydrothermal synthesis,analyzing the change of structure caused by differentsynthesis conditions.The results indicate that:The samples are spherical with size of0.02-0.04μm, the interal structure of which are wormhole-like mesoporous channels.Primely crystallinty can be obtained with only six hour crystallization. The bestsynthetic pH is between10-11.The thermal stability of these samples are good, in theroasting process, the heating rate should be keep to3.5K/min,otherwise the mesoporous structure of the samples would be destroyed.ⅡResearch of thiophene remove rate through oxidation reaction with Ti-HMSmolecular sievesThe effects of n（SiO₂）/n（TiO₂）,crystallization time and roasting temperature oncatalytic performance of Ti-HMS and the influences of reaction time,reaction temper-ature on thiophene remove rate were studied.The results indicate that the catalyticperformance of Ti-HMS on thiophene oxidation reaction are not only realted with Tiactive centers in the framework of Ti-HMS but also realted with channel diameter.The highest desulfurization rate was attained while n（SiO₂）/n（TiO₂） is20;And thebest reation temperature and reaction time are40℃and4h.Ⅲ Study on the structure and Catalysic performance of Zn-HMS molecularsievesZn-HMS was successfully prepared by direct synthesis with the transition metalZn doped into the HMS molecular sieves skeleton. All samples were characterizedusing a variety of techniques including XRD, TEM, SEM, and FT-IR. In addition,theeffect on the structure of molecular sieves of the different ratio of Zn/Si, crystallizat-ion time and the amount of template as well as the influence on the removal rate ofthiophene using different ratio of Zn/Si, zinc source and reaction time were investing-ated. The results show that the obtained sample were irregular crystal,it is the reunionof oval ball whose size is about100nm, and its internal short-range order of the worm-like pore structure. When the amount of Zn-doped SiO₂/ZnO up to30, orderedmolecular sieve is poor, and when the SiO₂/ZnO is10, the pore structure hadcollapsed. When we chosed the Zn（NO3）2as the zinc source, the effect of embeddedskeleton was best. When the SiO₂/ZnO=70,we got the highest removal rate in thereaction of catalytic oxidative desulfurization of thiophene.