丙烷选择氧化制丙烯醛催化剂中Ce的作用

考察了一系列助剂如:Cu、Zn、Mn、W、Ce、Pr、Nd等对Ag-Mo-P-O催化剂丙烷选择氧化制丙烯醛的影响.其中添加助剂Ce的Ag-Mo-P-O催化性能较好.添加Ce降低了丙烷氧化反应的活化能并有利于中间产物丙烯转化为丙烯醛.采用BET、XRD、H2-TPR、O2-TPD、C3H8-TPD和EPR等方法,研究了含Ce催化剂的结构和性质.结果表明,助剂Ce改善了催化剂的可还原性,并调变了催化剂中Mo5＋/Mo6＋比例,有利于催化剂上丙烷选择氧化生成丙烯醛,这可能归因于催化剂中形成Ce3＋＋Mo6＋Ce4＋＋Mo5＋氧化-还原循环的缘故.

Role of Ce on Selective Oxidation of Propane to Acrolein over Ce-Ag-Mo-P-O Catalysts

Role of Ce on the catalytic performance of Ce-Ag-Mo-P-O catalyst in selective oxidation of propane to acrolein was investigated.In order to establish the relationship between the catalytic performance and properties,the properties of Ag0.3Mo0.5P0.3Ox and Ce-doped Ag0.3Mo0.5P0.3Ox catalysts have been comparatively characterized by BET,XRD,H2-TPR,O2-TPD,C3H8-TPD and EPR.The addition of Ce to Ag0.3Mo0.5P0.3Ox catalyst distinctly improved the conversion of propane and the selectivity of acrolein.Ce0.1 Ag0.3Mo0.5P0.3Oy catalyst exhibited the highest selectivity and yield of acrolein in this reaction.The activation energy of propane oxidation was lower on the Ce0.1 Ag0.3Mo0.5P0.3Oy than on the Ag0.3Mo0.5P0.3Ox catalyst.Propene was a possible intermediate for the formation of acrolein in selective oxidation of propane on these catalysts.The proper addition of Ce enhanced the conversion of intermediate propene to acrolein.On the other hand,the addition of Ce improved the reducibility and Mo5＋/Mo6＋ ratio,furthermore,it caused a stronger adsorption of propane on the catalysts.The addition of Ce to the catalysts modified the properties by the formation of redox cycle “Ce3＋＋Mo6＋Ce4＋＋Mo5＋” in the catalysts.Such modification determined the catalytic performance of the catalysts in selective oxidation of propane to acrolein.