摘要
本文使用付立叶变换红外研究了甲烷在ＭｎＯ_２／ＳｉＯ_２催化剂表面的吸附，催化剂经高温（７７３Ｋ）抽空处理后，冷却至１７３Ｋ，进２４６６Ｐａ甲烷，在３００８，２９０４和１３０４ｃｍ￣（－１）处观察到三个红外吸收峰．其中２９０４ｃｍ￣（－１）的吸收峰归属为Ｃ－Ｈ键的对称伸缩振动，这一红外吸收峰的出现说明了甲烷分子的Ｔｄ点群发生畸变，对称性降低。因为红外惰性的２９１７ｃｍ￣（－１）红外峰显示出红外活性并位移至２９０４ｃｍ￣（－１）甲烷吸附于ＭｎＯ_２／ＳｉＯ_２表面后，由表面羟基产生的红外峰从３７００ｃｍ￣（－１）位移至３６７５ｃｍ￣（－１）．共吸附的ＣＯ影响甲烷的吸附，说明ＣＨ_４与催化剂表面阳离子的作用较弱。甲烷在ＭｎＯ_２／ＳｉＯ_２催化剂表面的吸附可能是通过甲烷的氢原子与表面羟基的氧和表面配位不饱和的氧离子间的氢键作用而形成的．
Methane adsorption on MnO_2/SiO_2 catalyst was investigated by FT-IR spectroscopy at 173 K.Adsorbed methane gives three IR bands at 3008,2904 and 1304 cm￣(-1)which could be attributed to V_1(2904 cm￣(-1)),V_3(3009 cm￣(-1)) and V_4(1304 cm￣(-1))modes of methane, respectively. The appearance of V1 mode indicates that Td symmetry of methane is distorted by the adsorption. A hydroxyl with IR band at 3700 cm￣(-1) perturbed evidently by the adsorbed CH_4 therefore resulting in a red-shifted band at 3675 cm￣(-1).Coadsorbed CO affects the adsorbed CH4 indicating the only weak interaction between CH4 and surface cations of the catalyst. It is proposed that the adsorbed CH4 on the catalyst is formed mainly via the interaction of its hydrogen atom with both oxygen anion of surface hydroxyl and surface c.u.s.(coordinated unsaturated sites)oxygen anion.
出处
《分子催化》
EI
CAS
CSCD
1995年第1期59-64,共6页
Journal of Molecular Catalysis(China)
基金
国家自然科学基金
