Pt/TiO_2/ZSM-5催化剂的制备及其催化转化正丁烷  

Preparation of Pt/TiO_2/ZSM-5 catalyst for catalytic conversion of n-butane

作　　者：刘佳[1] 姜桂元[1] 赵震[1] 韩善磊 张耀远 杨庆鑫[1] 孙乾耀[1] 王雅君[1] 

机构地区：[1]中国石油大学(北京)重质油国家重点实验室,北京102249

出　　处：《化工学报》2016年第8期3363-3373,共11页CIESC Journal

基　　金：国家重点基础研究发展计划项目(2012CB215001);国家自然科学基金石油化工联合基金项目(U1162117);北京高等学校青年英才计划项目(YETP0696);教育部新世纪优秀人才计划项目(NCET-11-0732);中国石油大学(北京)前瞻导向项目(QZDX-2014-02)~~

摘　　要：采用溶胶-凝胶法和等体积浸渍法,分别对ZSM-5分子筛进行Ti O2改性和Pt负载,获得了具有脱氢-裂解双功能的Pt/Ti O2/ZSM-5催化剂,采用XRD、N2吸附-脱附、TEM、XPS和NH3-TPD对样品的晶体结构,孔结构、形貌、活性金属价态和酸性质等进行了表征,并研究了正丁烷在此催化剂上催化转化制备低碳烯烃的反应规律。研究结果表明,Ti O2的引入,一方面使得改性后的ZSM-5分子筛获得了额外的酸性中心,特别是强酸性位含量的增加,有助于促进正丁烷的活化;另一方面Pt与Ti O2之间存在＂金属-载体＂强相互作用（SMSI）,在H2还原气氛下,Pt能够促进Ti O2的还原,生成Ti3＋物种,而Ti3＋的存在增加了Pt周围的电荷密度,降低了Pt对低碳烯烃（2C^=-3C^=）的吸附能力,抑制了深度脱氢和生焦反应,从而提高双功能催化剂对烯烃的选择性。当H2还原温度为450℃时,Pt/10Ti O2/ZSM-5催化剂在625℃下的正丁烷转化率为76.1%,低碳烯烃（2C^=-3C^=）收率为50.9%,分别比Pt/ZSM-5催化剂提高了16.7%和12.6%。Pt/Ti O2/ZSM-5 catalyst with dehydrogenation-cracking bifunctionality catalytic activity was prepared by modifying ZSM-5 zeolite with titanium dioxide（Ti O2） via sol-gel method and then loading Pt to the titanium modified ZSM-5 zeolite by incipient impregnation method. The as-prepared catalyst was characterized by means of XRD, N2 adsorption-desorption, TEM, XPS and NH3-TPD to analyze crystal structure, pore properties, morphology, valence states of active metal and acid properties of the catalyst, and the catalytic performance for the cracking of n-butane into light olefins was investigated. The results showed that the introduction of titanium dioxide provided additional acid sites to ZSM-5 zeolite, especially increasing the strong acid centers and enhancing the activation of n-butane. In addition, after reduction in hydrogen atmosphere, the partially reduced Ti3＋ species was generated which was catalyzed by platinum due to the strong metal-support interaction（SMSI） between Pt and Ti O2. The formation of appropriate amount of Ti3＋ species enhanced the electron density around Pt, and thus weakened the adsorption of ethene and propene on Pt atoms. After reduction by hydrogen at 450℃,n-butane conversion of 76.1% and yield of light olefins（2C^=—3C^=） of 50.9% were achieved at the reaction temperature of 625℃ over Pt/10 Ti O2/ZSM-5 catalyst, which was 16.7% and 12.6% higher than those of Pt/ZSM-5 catalyst, respectively.

关 键 词：Pt/TiO2/ZSM-5 催化剂 “金属-载体”强相互作用 分子筛 低碳烯烃 

分 类 号：O643.3[理学—物理化学]