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Preparation Of Ti/SBA-15by Chemical Vapor Deposition And The Catalytic Performance For Epoxidation Of Allyl Chloride

Posted on:2014-06-13Degree:MasterType:Thesis
Country:ChinaCandidate:Y H HuangFull Text:PDF
GTID:2251330401490713Subject:Chemical Engineering and Technology
Abstract/Summary:PDF Full Text Request
Epichlorohydrin(ECH) is an important organic intermediate with wide application andgreat demand. At present, epichlorohydrin is produced by high temperature chlorinationof propene and allyl acetate method in industry. But the two methods have somedisadvantages, such as long technological process, large energy consumption and seriouspollution, In this thesis, Ti/SBA-15was prepared by the method of Chemical VapourDeposition (CVD), which was used as catalyst in the direct epoxidation of allyl chloridewith the tert-butyl hydroperoxide(TBHP) as oxidant.Firstly, SBA-15carries was prepared with triblock copolymer P123as template agentand ethyl silicate(TEOS)as silicon source by hydrothermal synthesis method. Thesamples were characterized by the techniques of N2physical adsorption, UV-Vis, FT-IR,SEM. Effects of silicon mold ratio, acid concentration, reaction temperature,crystallization time and crystallization temperature, calcinations temperature on the porestructure of SBA-15were investigated. The results showed that specific surface area ofcarrier in200-800m2/g and the pore volume in0.5-1.1cc/g and the pore diameter in3.8-18nm can be adjusted by changing the preparation conditions of SBA-15. Thesuitable conditions for preparation of SBA-15are as follows: silicon mold ratio60,hydrochloric acid concentration2mol/L, reaction temperature40°C, the crystallizationtemperature100°C, crystallization time24h, calcinations temperature550°C。Secondly, Ti/SBA-15were synthesized by CVD method. The samples arecharacterized by N2physical adsorption techniques, UV-Vis, FT-IR, ICP, XRD. Effects ofconditions such as titanium sources, solvent, titanium source concentration, carrier,deposition time and deposition temperature were discussed. The better characterizationresults Ti/SBA-15chosen for performance evaluation in the allyl chloride epoxidationreaction. The results showed that the suitable titanium sources for CVD preparation ofTi/SBA-15was TiCl4and the effect of the TiCl4dissolved in methylene chloride wasbetter than the one in methanol or toluene solution. suitable concentration was80%,Titanium content increased with the increasing of specific surface area of the carries. Theproper deposition time is1.5h and the deposition temperature is700°C, under theconditon titanium doping amount as high was as2.38%. the samples in allyl chlorideepoxidation reaction exhibit excellent catalytic activity, TBHP conversion reached60.4%,the selectivity of ECH to TBHP reached50.65%.Finally, Ti/SBA-15was prepared by direct hydrothermal method in order to compare the method of CVD. The results showed that the method of CVD could provide muchamounts of active tetravalent Titanium than the method of direct hydrothermal, whichrepresented better catalytic performance. The following modification of catalyst wereinvestigated Hydrothermal pretreatment process for SBA-15carrier can improve thenumber of surface silicon hydroxyl resulted in the increasing of doping titanium from1.40%to2.41%.The silylation modification for Ti/SBA-15used hexamethyldisilazaneas silylating reagent can improve the hydrophobic performance, which led to the obviouseffect on catalytic performance. TBHP conversion was improved to80.57%, and theselectivity of ECH based on TBHP was up to79.72%.
Keywords/Search Tags:CVD method, Ti/SBA-15, Silylation, Allyl chloride, Epoxidation
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