密度泛函理論對金屬氧化物系統之催化特性探討：硫酸化氧化鋯之酸性

Abstract

藉由密度泛函理論模擬含重金屬系統之物理化學特性，此論文研究不同模型下硫酸化氧化鋯表面之酸性。 由先前研究得知，硫酸化氧化鋯可在低溫下催化正丁烷成異丁烷的異構化反應，並且可藉由鋁的促進得到較高的催化活性和穩定度。以正方晶相氧化鋯為出發，研究在不同位置上，利用不同模型、不同函數、不同基底討論純的、水合的、加入硫酸與加入鋁的氧化鋯結構與能量。在可能的模型下分析振動頻律、電荷分佈、脫氫與氨氣或?啶（pyridine）吸附的能量來探討硫酸與鋁對氧化鋯表面路易士與布忍斯特酸的強弱。利用Kohn-Sham軌域的計算討論X光電子能質譜對?啶吸附表面後N1s軌域的化學位移。計算結果顯示硫酸根對於布忍斯特酸性強弱的增加扮演了重要的角色，而鋁的加入可以調控表面酸性的強弱。

Density functional theory (DFT) calculations have been performed to investigate chem- ical and physical properties of mixed metal oxide systems including acidities with sev- eral models for the sulfated zirconia (SZ) system. It has been proposed that aluminum promoted SZ have higher catalytic activity and stability on n-butane to iso-butane iso- merization reaction. The structures and energies of pure, hydroxylated, sulfate adsorbed and aluminum promoted zirconium oxide were examined based on tetragonal phase using periodic plane wave and cluster model method, respectively, through di(R)erent models, sites, functionals and basis sets. The Br?nsted acidities as well as Lewis acidities on dif- ferent zirconium oxide surfaces were estimated from the vibrational frequencies, charge distributions, deprotonation energies and ammonia or pyridine adsorption energies to evaluate the e(R)ects of sulfur and aluminum species. In pyridine adsorptions, the XPS core-level shifts of N1s were calculated from Kohn-Sham orbital energy di(R)erences. It was found that the sulfate species plays an important role in elevating Br?nsted acidities and the aluminum species is used to modify the acid strengths.