First principle investigation into the acid properties of Pd modified ZSM-12 zeolite
作者单位：Institue of Applied ChemistryCollege of ChemistryNanchang University National Supercomputing Center in Shenzhen
会议名称：《第十三届全国量子化学会议》
会议日期：2017年
学科分类：081704[工学-应用化学] 07[理学] 070304[理学-物理化学(含∶化学物理)] 08[工学] 0817[工学-化学工程与技术] 0703[理学-化学]
关 键 词：ZSM-12 acid property NH3 adsorption density functional theory
摘 要：The ZSM-12 zeolite has 12-membered ring, which belongs to the MTW-type1. Due to its exceptional pore structure and acid property, the ZSM-12 zeolite is considered to have g reat potential for industry applications. The synthesized zeolites are usually modified by a certain metal ions using ion exchange or impregnation methods to adjust the catalytic property of the catalysts. Aims at understanding the real condition of the Pd modified zeolites in catalytic reactions, this work investigates the structures, energies, acidity as well as the activity for H adsorption of Pd modified HAl-ZSM-12 zeolites using dispersion corrected periodic density functional theory2,3. It is found that the Pd could insert into the-OH groups to form the spillover structure of-O-Pd-H. The Br?nsted acid H site of the zeolite reduced by Pd monomer to produce H is thermodynamically favorable, while unfavorable for Pd dimmer. The Pd mod ification leads to weaker Lewis acidity of Al and Br?nsted acidity of-OH. However, the Pd atoms could work as strong Lewis sites in the zeolites. Pd modif ication also improves the H activation/adsorption properties of HAl-ZSM-12. The acid properties of the Pd modified zeolites could be inevitably influenced by H atmosphere, since the dissociatively adsorbed H could work as new Br?nsted acid H and also influences the charge of Pd atoms. The calculated NH3 adsorption energy reveals that H adsorbs in Pd modified HAl-ZSM-12 results in weaker Lewis acidity of Pd sites. The new formed Br?nsted acid sites after H adsorption are weaker than the original HAl-ZSM-12.