锐钛相介孔SO_4^(2-)/TiO_2的声化学制备及结构和催化酯化性能

Sonochemical Preparation, Structures and Catalytic Esterification of Mesoporous Anatase SO_4^(2-)/TiO_2

不使用有机模板剂,采用超声化学法一步水解制得吸附硫酸根的介孔偏钛酸,500℃焙烧得到介孔SO42-/TiO2固体超强酸。用XRD、TEM、FTIR、低温氮吸附-脱附等手段对催化剂结构进行了表征。结果表明,硫酸根在焙烧过程中与前驱体介孔偏钛酸孔壁上自由羟基的键合起到了孔结构导向及支撑作用,500℃焙烧后样品具有161m2·g-1的比表面积及4.1nm的平均孔径,酸强度H0介于-14.52与-16.02之间,硫含量为2.8%,晶型全部为锐钛矿相,介孔SO42-/TiO2具有较大比表面、强酸特性和稳定性。催化合成富马酸二甲酯的最佳条件为:n(甲醇)∶n(富马酸)=6∶1,催化剂用量为1.0%(反应物总质量),带水剂苯用量为10mL,反应时间为3h,催化剂重复使用7次,酯化率大于90%。

Mesoporous metatitanic acid with plentiful SO4^2- absorbed was one-step synthesized by an ultrasonic chemistry and hydrolysis method without organic templates. Mesoporous solid superacid catalyst SO4^2-/TiO2 was obtained by calcination at 500 ℃. The catalyst was characterized by XRD, TEM, FTIR, N2 absorption/desorption. SO4^2- bonded to free -OH on pore walls of metatitanic acid during the calcinations acts as the pore structuredirecting agent and pore structure support. After calcination at 500 ℃, the mesoporous SO4^2-/TiO2 in anatase phase has a specific surface area of 161 m^2·g^-1, an average pore diameter of 4.1 nm, sulfur mass fraction of 2.8% and acid strength（H0） between -14.52 and -16.02. The catalyst has larger specific surface area, higher superacid strength and better thermal stability. Based on the orthogonal experiment, the optimum synthetic conditions for dimethyl fumarate were as follows： the molar ratio of earbinol to fumaric acid was 6：1, mass of the catalyst was 1.0%（reactant total mass ratio）, the volume of the water removing reagent benzene was 10 mL, and the reaction time was 3 h. The catalyst exhibited good stability and the conversion of acetic acid still amounted to 90% after 7 runs.