丙烯环氧化反应溶剂效应和酸碱效应研究

以用四丙基溴化铵（TPABr）为模板剂合成的钛硅分子筛TS－1为催化剂，H2O2为氧化剂，研究了丙烯环氧化反应中的溶剂效应和酸碱效应。结果表明，采用甲醇－水混合溶剂，随着溶剂中含量的增加，环氧丙烷（PO）选择性下降，丙二醇（PG）选择性升高。少量水对H2O2转化率影响不大，但水量超过50％时，H2O2转化率明显降低。与甲醇相比，采用乙醇、异丙醇或丙酮为党课时，反应效果均较差。反应介质的pH值对环氧化产物分布影响显著。碱性物质的加入可以明显地提高PO选择性，抑制O和溶剂发生副反应。过量碱性物质易造成催化剂失活，这种失活是可逆的。控制碱性添加物的用量，催化剂重复使用21次仍具有较好的催化性能。实验结果证实了钛硅分子筛－醇类溶剂－H2O2共存的体系中反应按五元环过渡态的机理进行。

EFFECTS OF THE SOLVENT, ACID AND BASE ON THE PROPYLENE EPOXIDATION

The titanium silicalite synthesized by using tetrapropylammonium bromide (TPABr) as template was used to catalyze the synthesis of propylene oxide (PO) from propylene and hydrogen peroxide Effects of the solvent and pH value of the medium on propylene epoxidation were investigated The results indicated that as the content of water in the mixed solvent of methanol and water increased, PO selectivity decreased and propylene glycol selectivity increased A small amount of water showed no effect on H 2O 2 conversion, but as the content of water reached a half in the mixed solvent, H 2O 2 conversion decreased Compared with methanol, inferior results were obtained if ethanol, n propylalcohol, i propylalcohol or acetone were used as the solvents The pH value of the medium influences the composition of the product remarkably PO selectivity increased significantly when a small amount of base was added in the medium, but larger amount of base inhibited the activity of the catalyst In this work, TS 1 catalyst have been used for 21 times with better performance in propylene epoxidation