摘要
笔者曾报导过TiO_2和CoO的协同效应使Mo-Co系HDS催化剂的内在活性增强,活性中心数目增加。为了进一步了解上述协同效应的作用本质,本文研究了反应物噻吩等在MoO_3/Al_2O_3、MoO_3-CoO/Al_2O_3和一系列MoO_3-CoO-TiO_2/Al_2O_3催化剂上的吸附行为。 1.实验 1.1 催化剂的制备及其活化条件 催化剂制备方法参阅文献[2]。将所得氧化态催化剂在氢气流下。
The gas chromatographic technique was used to study high-temperature adsorption of thiophene on Mo/Al2O3, Mo-Co/Al2O3 and Mo-Co -Ti/Al2O3 catalysts either by use of H2 or N2 as the carrier gas. The adsorption of thiophene was carried out in the range of 210-230℃ ( for H2 ) and 230-310℃ ( for N2 ) respectively. The following results are obtained and discussed.
1. The adsorption heat ( Q ) of thiophene for Mo/Al2O3 is identical to that for Mo-Co/Al2O3, but the retention volume (Vg) is larger for Mo-Co/Al2O3 than for Mo/Al2O3. This means that CoO may only affect the number of the adsorption sites, but not the adsorption properties of Mo catalyst.
2. The co-addition of CoO and TiO2 onto Mo catalyst greatly affects the number of its adsorption sites as well as adsorption properties. The Vg value of Mo-Co-Ti/Al2O3 is larger than that of Mo/Al2O3 or Mo-Co/Al2O3, and increases with the increase of TiO2 content.This indicates that the number of the adsorption sites of the catalyst is increased with the addition of TiO2. XPS and XRD determinations have shown that this is so because TiO2 may improve the dispersion of MoO3 on A12O3.
The Q value and true activation energy, Et of Mo-Co-Ti/Al2O3 are also larger than that of Mo/Al2O3 or Mo-Co/Al2O3. This suggests that the synergetic effect of CoO and TiO2 strengthens the adsorption properties of the Mo catalyst.
3. The determination of Vg and Q by use of H2 ( VgH, QH ) or N2 ( VgN, QN ) as the carrier gas shows that VgH= VgN and QH>QN. It is suggested that surface H on catalyst may take part in the absorption behavior of catalyst and strengthens its adsorption capability.
出处
《分子催化》
EI
CAS
CSCD
1991年第3期263-267,共5页
Journal of Molecular Catalysis(China)
