不同沉淀剂制备的Ag／TS－1催化丙烯直接气相氧化合成环氧丙烷

 在423K、常压固定床石英反应器中，以丙烯直接气相氧化为探针反应，考察了催化剂制备方法、沉淀剂的种类和浓度对制备的Ag／TS－1催化剂催化性能的影响，采用TEM，XRD和UV－Vis等表征手段对Ag／TS－1催化剂进行了分析．结果表明，沉积－沉淀法是最佳的催化剂制备方法，但浸渍法也可制得具有环氧丙烷选择性的催化剂．K2CO3是一种良好的沉淀剂．以K2CO3为沉淀剂，硅钛比为64的TS－1为载体制备的Ag／TS－1催化剂上的丙烯转化率为1．72％，环氧丙烷选择性为98．2％．少量单质银的存在有利于环氧丙烷的生成，除银粒子的分散状态外，银粒子与载体TS－1间的相互作用对提高催化剂的选择性具有决定性作用．

Synthesis of Propylene Oxide by Gas-Phase Propylene Epoxidation over Ag/TS-1 Prepared with Different Precipitators

The effects of preparation method and precipitator for TS 1 support on the gas phase propylene epoxidation over the Ag/TS 1 catalyst were investigated in a fixed bed quartz reactor at 423 K and ambient pressure. The Ag/TS 1 catalyst was characterized by TEM, XRD and UV Vis spectroscopy. The results show that the deposition precipitation method is optimum, but Ag/TS 1 prepared by the impregnation method also shows moderate selectivity for propylene oxide (PO). Alkaline metal carbonate such as K 2CO 3 is a suitable precipitator for the preparation of the Ag/TS 1 catalyst. The existence of K + can improve both the propylene conversion and the PO selectivity. A propylene conversion of 1 72% and a PO selectivity of 98 2% are obtained over Ag/TS 1( n (Si) / n (Ti) =64) prepared using 0 07 mol/L K 2CO 3 as the precipitator. The characterization indicates that a small quantity of metal silver favors the formation of PO. The dispersion of silver species and the interaction between silver species and TS 1 play important roles in improving the catalyst selectivity.