Cr掺杂ZSM-5双功能催化剂的制备及其催化裂解正丁烷  

Incorporation of Cr in ZSM-5 zeolite framework as bifunctional catalysts for n-butane catalytic cracking

作　　者：赵丹[1] 袁美华[1] 张耀远 姜桂元[1] 赵震[1] 刘佳[1] 韩善磊 孙华倩 

机构地区：[1]中国石油大学重质油国家重点实验室,北京102249

出　　处：《化工学报》2016年第8期3400-3407,共8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：采用原位合成的方法制备了Cr掺杂的ZSM-5分子筛,研究了Cr含量对于正丁烷催化裂解性能的影响。利用X射线衍射(XRD)、N2吸附脱附、紫外可见漫反射光谱(UV-Vis)、拉曼光谱(Raman)、氨程序升温脱附技术(NH3-TPD)和吡啶红外(Py-FTIR)等表征手段研究了分子筛的结构、Cr物种的存在状态以及分子筛的酸性。研究结果表明,部分Cr进入分子筛的骨架,以单分散的形式存在,当Cr含量较低时,Cr的引入对于分子筛的弱酸性没有太大的影响。少量Cr的引入会极大提高正丁烷的转化率和乙烯、丙烯的收率,当Cr/Al摩尔比为0.04,反应温度为650℃时,正丁烷的转化率达到99.2%,乙烯、丙烯的收率达到53.8%,分别比未改性的ZSM-5高15.5%和5.0%。这可能是由于Cr活性组分的脱氢性能和分子筛的酸性形成协同作用,促进了正丁烷的高效转化。The Cr-doped ZSM-5 zeolites were synthesized by in-situ hydrothermal method and were used in studying Cr effect on catalytic cracking of n-butane to produce light olefins. Zeolite structure, chemical state of Cr species and acidity of zeolites were characterized by several techniques, including X-ray diffraction, nitrogen adsorption and desorption, ultraviolet visible diffuse reflectance spectroscopy, Raman spectroscopy, ammonia temperature-programmed desorption and pyrrolidine（Py）-FTIR. Cr species were found to partially incorporate in the ZSM-5 framework and present in the form of monodispersion. No significant difference in the weak acidity of zeolites at low Cr content. However, a small amount of Cr species in zeolites could significantly enhance conversion of n-butane and improve yield of ethylene and propylene. When the molar ratio of Cr/Al was 0.04, the conversion of n-butane was 99.6% and the yield of ethylene and propylene was 53.8% at reaction temperature of 650℃, which was 15.5% and 5.0% higher than those of unmodified ZSM-5, respectively. The superior catalytic performance could be attributed to synergistic effects of dehydrogenation of active Cr species and cracking function of the acidic zeolite, which promoted highly efficient conversion of n-butane.

关 键 词：CR掺杂 ZSM-5分子筛 双功能 催化裂解 低碳烯烃 

分 类 号：O643.3[理学—物理化学]