PdV性分子筛催化苯与氢气氧气羟基化反应研究.docVIP

Pd-V改性分子筛催化苯与氢气氧气羟基化反应的研究 化学专业 2002级 陆庆祝 摘 要：在自行设计的一个气体内循环反应装置上，研究了Pd、Pd-V、Pd-Cu和Pd-Fe改性的Hβ和ZSM-5催化剂催化苯与氢氧直接羟基化反应。结果表明：单Pd系列催化剂均能催化苯和氢气、氧气的羟基化反应，但其活性较低。为了提高催化剂活性，我们采用浸渍法制备了Pd-V、Pd-Cu和Pd-Fe改性的Hβ, 以及Pd-V/ZSM-5系列双金属改性催化剂。我们发现对于以Hβ沸石为载体的这类双金属催化剂的催化活性较单钯负载催化剂提高了很多。这可能是因为Pd促进双氧水的生成，而V、Cu和Fe又能促进双氧水与苯的反应，然而以ZSM-5为载体的双金属改性催化剂其活性较单钯负载催化剂并没提高多少。我们还发现苯酚生成速率在单乙酸介质中较低，而添加适量水后则显著增加。这里我们提出了一个协同催化作用机理来解释有关过渡金属的改性作用和水的添加效应。 为了考察催化剂回收的使用活性，我们对0.5 wt%Pd/ZSM-5、Pd-V/ZSM-5、Pd-V/Hβ、Pd-Cu/Hβ和Pd-Fe/Hβ催化剂进行了回收，发现催化剂经过处理后普遍存在失活的现象，相对而言，Pd-Cu/Hβ有着较好的回收使用性能。 关键词: 苯酚; 苯羟基化; Pd-V/Hβ; Pd-V/ZSM-5; Pd/ZSM-5; 浸渍法 Studies on the Pd-V modified zeolite catalysts for the direct liquid hydroxylation of benzene with H2 and O2 under the atmosphere QingzhuLu,Grade2002,Chemical Education Abstract: A gas inner-circulated apparatus, which was designed by us was employed to carry out the direct hydroxylation of benzene with H2 and O2 over Hβ and ZSM-5 catalysts modified by Pd；Pd-V；Pd-Cu and Pd-Fe under the atmosphere. The results showed that all the only Pd supported catalysts could catalyze this reaction but their activities were demonstrated relatively low. To improve the activities of catalysts, we had prepared bimetal-modified catalysts such as Pd-V；Pd-Cu and Pd-Fe modified Hβ catalysts, and Pd-V/ZSM-5 by impregnation method. It was found that bimetal-modified Hβ catalysts showed much higher catalytic activity than single Pd modified ones. It can be interpreted that Pd was beneficial to the formation of H2O2 and at the same time V, Cu and Fe were helpful to the hydroxylation reaction between H2O2 and benzene. However, the activity of bimetal-modified catalysts did not be improved much compared to single Pd catalysts when ZSM-5 was used as support. Herein, we also found out that the rate of phenol formation using glacial acid as reaction medium was relatively low but it was significantly improved as the suitable amount of water was added to glacial acid. Therefore, we put forward a harmonious catalytic mecha