【作者】 王金雪；

【导师】 郭新闻；

【作者基本信息】 大连理工大学 ， 工业催化， 2011， 博士

【摘要】 由于环境保护的压力,越来越多的研究者正致力于环氧丙烷绿色合成工艺的开发。氧气为原料直接一步生产环氧丙烷是目前最具有挑战性的工艺之一。采用Ag催化剂直接催化乙烯气相环氧化生产环氧乙烷的工艺已经实现工业化,但是氧气直接氧化丙烯制环氧丙烷仍处于探索阶段。乙烯环氧化的Ag催化剂用于丙烯气相环氧化时选择性低,近年来开发的Au-Ti共同体系可以有效地解决催化剂选择性低的问题。但是,催化剂仍存在转化率不高,H2利用率低和容易失活的问题。因此,对于丙烯直接气相环氧化催化剂的开发和反应过程的研究十分必要。本论文重点探讨了Ag/TS-1催化剂沉淀剂的作用、TS.1载体的影响、催化剂新制备方法等对丙烯气相环氧化反应性能的影响。主要内容和成果包括：(1)以沉积沉淀法制备Ag/TS-1催化剂,考察了KOH, NaOH, K2CO3和Na2CO3等沉淀剂对催化剂丙烯气相环氧化性能的影响,发现KOH具有良好的控制活性金属Ag分布和粒径的性能。K+的存在可以改善催化剂的稳定性,催化剂在600 min内转化率不低于1%,选择性不低于90%。(2)以不同的钛源和碱源合成了一系列微米TS-1载体,负载Ag后进行环氧化反应,研究了TS-1中不同Ti物种对丙烯环氧化活性及环氧丙烷选择性的影响,发现四配位的骨架钛具有环氧化的性能,无定形的TiOx物种导致副反应发生并使催化剂失活；TS-1中的锐钛矿TiO2物种也具有气相环氧化活性。(3)采用等离子体溅射法成功制备不同Ag含量和粒径的Ag/TS-1催化剂,应用于丙烯环氧化反应。等离子体溅射可以保证Ag颗粒与TS-1充分接触。与沉积沉淀法相比,反应产物比较复杂。催化剂转化率为0.5-1.6%,选择性为76-95%。(4)针对反应热效应和Ag颗粒的尺寸效应进行研究,发现Ag的尺寸不是决定环氧丙烷选择性的关键,8-40 nn范围内的Ag都有环氧化活性,且环氧丙烷选择性都高于90%。活性Ti物种含量以及有效的Ag-Ti接触面积对反应活性影响较大。反应中的热量传递直接影响催化剂的环氧丙烷收率和催化剂寿命。更多还原

【Abstract】 Since environmental problems have been severe nowadays, a lot of efforts have been made to develop an alternative direct epoxidation processes for the production of propene oxide (PO). PO production using oxygen is now the most promising process, and also one of the top tough projects, which is suffering from low conversion or low PO selectivity. It’s important to figure out the factors which are affecting the PO production on gas-phase propene epoxidation.Therefore, this work is focus on support and promoter effort on Ag/TS-1 for gas-phase epoxidation, also a new preparing Ag/TS-1 catalyst approach is investigated. The major parts include:(1) Alkali precipitator KOH, NaOH, K2CO3 and Na2CO3 are used to prepare Ag/TS-1 catalyst by deposition-precipitation (DP) method. KOH shows good ability on controlling Ag dispersity and size distribution. It was found that K+ is good promoter for Ag/TS-1 catalyst. The catalyst maintains activity above 1%, and selectivity above 90% in at least 600 min.(2) In order to observe Ti species on propene epoxidation, different Ti and alkali sources are used to prepare a serial of micro TS-1. The results show that tetrahedral Ti sites are active for PO formation, non-framework TiOx results in by-reaction of propene, leading to deactivation of catalyst. Anatase also could be beneficial for propene epoxidation.(3) Plasma sputtering process is found to be useful approach for preparing Ag/TS-1, which can produce different size Ag embedding onto TS-1. Compared with DP method, the plasma sputtering made Ag/TS-1 catalyst has more by-products. The propene conversion is 0.5-1.6%, and propene oxide selectivity is 76-95%.(4) Ag size and thermal effect are also discussed in this paper. The results indicate that PO selectivity was not sensetive to Ag particle size. In an Ag size range of 8-40 nm, All Ag/TS-1 catalysts show propene oxide selectivity above 90%. Ag-Ti balance is important on catalyst activity for PO production. Thermal effect severely affects PO selectivity and the life of catalyst.更多还原