氨和有机胺对羰基硫与α-Fe2O3非均相反应的影响

利用原位漫反射傅里叶红外光谱(DRIFTS), 考察了室温下羰基硫(COS)在经氨气和有机胺预吸附的α-Fe₂O₃上的非均相反应, 并同时比较了氨气和不同有机胺(甲胺、三甲胺、三乙胺、苯胺、吡啶和吡咯)对反应活性的影响及其反应动力学. 结果表明, 经碱性物质预吸附后, COS可在α-Fe₂O₃表面发生氧化反应, 主要产物为气态CO₂、表面HCO₃^-、表面CO₃^2-和表面SO₄^2-, 且α-Fe₂O₃表面预吸附的碱性物质大大提高了COS在α-Fe₂O₃上的反应能力, 在碱性物质的影响中, 甲胺对反应的促进能力最大, 相比纯α-Fe₂O₃反应的反应活性提高了约4.5倍, 然而苯胺和吡咯对COS的反应影响不是很明显.观察到的不同碱性物质对COS的转化能力依次为: 甲胺>三甲胺>氨气>三乙胺>吡啶>吡咯>苯胺≈纯样品, 受碱性物质的影响, COS的反应级数由一级转变为二级. 此外, 研究也发现碱性物质的覆盖度和表面吸附水对COS转化能力存在一定的影响. 这些实验结果表明在碱性物质存在下,表面M―O^-是COS在α-Fe₂O₃发生氧化反应的关键活性位点, 对反应活性的贡献较大, 并在此基础上探讨碱性条件下COS的反应转化机制.

Effects of Ammonia and Amines on Heterogeneous Oxidation of Carbonyl Sulfide on Hematite

The heterogeneous oxidation of carbonyl sulfide (COS) on hematite pre-adsorbed with ammonia and methylamine, trimethylamine, triethylamine, phenylamine, pyridine, and pyrrole was investigated using in situ diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFTS) at room temperature. The products and kinetics of the heterogeneous reaction were investigated. The results showed that adsorbed COS could be oxidized on the surface of hematite pre-adsorbed with these basic substances, forming gaseous carbon dioxide (CO₂), surface bicarbonate (HCO₃^-), surface carbonate (CO₃^2-), and surface SO₄^2-. Ammonia and amines pre-adsorbed on hematite significantly enhanced the reactivity of COS. Hematite with pre-adsorbed methylamine exhibited the highest reactivity, about 4.5 times higher than that of pure hematite, whereas the effects of phenylamine and pyrrole were not obvious. The reaction rates with the basic substances were in the order of methylamine>trimethylamine>ammonia>triethylamine>pyridine> pyrrole> phenylamine≈pure hematite. The basic substances changed the reaction order from first to second. Coverage by the basic substances and surface water also played important roles in the heterogeneous reaction of COS. These experimental results indicated that surface oxygen species (M―O^-) were the key factor contributing to oxidizing activities in the presence of basic substances. The heterogeneous oxidation mechanism of COS on hematite with pre-adsorbed basic substances is discussed on the basis of the experimental results.