Preparation Of Modified Mesoporous SBA - 15 Catalyst And Study On Catalytic Synthesis Of Non - Toxic Plasticizer

Esterification of carboxylic acids with alcohols is one of the most importantreactions in organic synthesis. The plasticizers, such as trioctyl citrate or trioctyltrimellitate, found wide use in commodity and engineering appliances as well as inmedical applications. Strong acids like concentrated sulfuric acid are used as catalyststo synthesize esters by most of manufacturers up to now. Unfortunately, theseprocesses will cause equipment corrosion, difficult separation procedures and thepollution of by-products. The periodically ordered pores at the micrometric scale,narrow pore size distribution, thick pore wall, high pore volume and high specificsurface area make SBA-15as a very suitable support for the preparationofmesoporous solid acid catalysts to attract extensive attention. In this paper thesynthesis of modified SBA-15samples with different properties by grafting differentactive components and catalytic properties of the SBA-15mesoporous solid acidcatalysts in the esterification of trioctyl citrate or trioctyl trimellitate were mainlyinvestigated.1. Al-SBA-15mesoporous molecular sieve was synthesized with aluminiumisopropoxide as raw material through impregnation method. After impregnation withsulfuric acid, mesoporous solid superacid SO42-/Al-SBA-15was prepared. Thecatalysts were throughly characterized by N2adsorption-desorption, means of powderX-ray diffraction, transmission electron micrographs and thermogravimetric analysis.The catalyst was applied in the synthesis of trioctyl trimellitate. The experimentshows that the esterification yield is96.66%under the following conditions: the molarratio of trimellitic anhydride to2-ethyl hexylalcohol is1:4, the mass of catalyst is4%of total mass, the reaction is6h and the oil bath temperature is210℃.2. Three types of sulfonic acid functionalized hybrid mesoporous solid acidmaterials R-SBA-15-SO3H containing different hydrophobic alkyl (methyl, n-octyl ordodecyl) were synthesized by hydrothermal treatment. The results catalysts werecharacterized via a range of analytical techniques, including transmission electronmicrographs, thermogravimetric analysis, powder X-ray diffraction and N2adsorption-desorption. The results revealed that the catalytic activity increased withthe hydrophobicity of the materials and the hydrophobicity of the prepared materials increased with the increase of alkyl number. The esterification experiment shows thatthe esterification yield is96.66%under the following conditions: the molar ratio oftrimellitic anhydride to2-ethyl hexylalcohol is1:4, the catalyst is C12H25-SBA-15SO3H, the mass of catalyst is4%of total mass, the reaction is6h and the oil bathtemperature is210℃.3. Four types of sulfonic acid functionalized mesoporous solid acid materialsSBA-15-SO3H, Al-SBA-15-SO3H, Nb-SBA-15-SO3H (d) and Nb-SBA-15-SO3H (p)were synthesized by hydrothermal treatment. The catalysts which were applied in thesynthesis of trioctyl citrate have been characterized by various sophisticatedtechniques, including powder X-ray diffraction, transmission electron Micrographsand N2adsorption-desorption. They are very similar evidencing that the impregnationmethod for incorporation of niobium atoms and sulfonic acid groups in mesoporoussilica does not affect its pore structure. The optimal parameters of trioctyl citrateesterification using Nb-SBA-15-SO3H (p) obtained within the experimental rangesstudied are as follows: Catalyst Nb-SBA-15-SO3H (p) at4wt.%, a n-caprylic alcoholto citric acid molar ratio of4:1, temperature of150°C and the reaction of6h. Underthese conditions, a maximum esterification yield of93.65%could be obtained. Thecatalyst shows good catalytic activity, cost effectiveness, recyclability andenvironmental friendliness and the applications of the catalyst can also be extended toother acid-catalyzed reactions.