MoO3/ZrO2固体酸催化合成二甲基硅油

Synthesis and properties of MoO3/ZrO2 solid acid catalysts for the preparation of polydimethylsiloxane

采用浸渍法制备了系列MoO3/ZrO2固体酸催化剂,利用XRD、BET和NH3-TPD测定其晶型结构、表面性质及酸性。结果表明,适量的MoO3可以使ZrO2单斜相向四方相转变,增加样品的比表面积,提高酸强度。把MoO3/ZrO2酸催化剂应用于二甲基硅油的合成反应,结果显示w(MoO3)及煅烧温度对催化剂的催化性能有很大的影响。反应过程存在反咬反应,增加反应时间和反应温度都会导致产物数均分子量(Mn)减小、分子量分布变宽,二甲基硅油的最佳合成条件为m(催化剂)∶m(反应物)=1.0%,反应时间2h,反应温度70℃。

A series of MoO3/ZrO2 catalysts were prepared by impregnation method,and characterized by X-ray diffraction(XRD),specific surface area (BET) and temperature-programmed desorption of NH 3 (NH 3-TPD).The results revealed that an appropriate amount of MoO 3 in MoO3/ZrO2 can transform ZrO2 from monoclinic to tetragonal phase,increase the specific surface area and the acid intensity of the samples.It was found that MoO 3 loading and calcination temperature had an important impact on the catalyst performance when MoO3/ZrO2 was applied to the synthesis of polydimethylsiloxane.The number-average molecular decreased and the molecular weight distribution broadened with the enhancement of the reaction temperature and time due to the backbiting reactions.The optimum synthesis conditions were as follows:the mass ratio of catalyst and reactant is 1.0%,reacting time is 2 h,reaction temperature is 70 ℃.