Ti-MWW分子筛吸附H2O和NH3的结构和振动光谱的
密度泛函理论计算
乔溢铭;范志琳;蒋艳娇;李娜;董浩;贺宁;周丹红
【期刊名称】《催化学报》 【年(卷),期】2015(000)010
【摘要】The structures and vibrational spectroscopic features of framework Ti(IV) species in Ti-MWW zeo-lite upon adsorption of H2O and NH3 were investigated by density functional theory. The calcula-tions were carried out on cluster models up to 36 tetrahedra at the B3LYP/6-31G(d,p) level of the-ory. The calculated results indicate that both Ti(OSi)4 and Ti(OSi)3OH species can interact with H2O or NH3 molecules to form five-coordinated complexes. The Ti(OSi)3OH species has higher Lewis acidity and adsorbs the ligands more easily than Ti(OSi)4. The Ti-specific band is attributed to the collective vibration of the antisymmetric stretching of Ti–O–Si bonds. The vibrational frequencies of coordinated Ti species can be divided into two regions: the Ti-specific vibration region and the hydroxyl group vibration region. After adsorption of H2O, the Ti-specific band of the Ti(OSi)4 species shifted from 960 to 970 cm?1, and the Ti-specific bands of the Ti(OSi)3OH species shifted from 990 cm?1 (T1 site) and 970 cm?1 (T3 site) to 980 cm?1. The frequencies of the corresponding NH3 adducts were about 5 cm?1 higher. The Ti(OSi)3OH species can also form
Ti-MWW分子筛吸附H2O和NH3的结构和振动光谱的密度泛函理论计算
