基于FeO23／TiO2催化剂的H2S选择性催化氧化反应研究
Selective catalytic oxidation of H2S over Fe2O3 /TiO2 catalysts
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摘要: 采用溶胶凝胶法制备了 Fe2 O3 / TiO2 催化剂，通过 BET，XRD，XPS 和 XRF 等对催化剂 物化性质进行表征，并利用固定床反应系统考察了该催化剂对 H2 S 选择性催化氧化反应的活 性。 结果表明，当 Fe2 O3 负载量低于 15%时，随着负载量增大，催化剂比表面积逐渐增大，Fe2O3 以高度分散态或非晶体形态均匀存在于催化剂体相中;而继续增大 Fe2 O3 负载量到 20%，催化剂比表面积下降，催化剂内 Fe2 O3 以晶体形式存在并会堵塞催化剂表面的孔结构。 随着负载量的增加，Fe2 O3 / TiO2 的 H2 S 转化率和产硫率先增加后减小，而硫选择性不断减小， 15% Fe2 O3 / TiO2 催化剂具有最佳的催化活性，在反应温度 180 °C 、O2 / H2 S 物质的量比为 0. 5 的条件下，催化剂的 H2 S 转化率，硫选择性和产硫率分别为 96. 57%，95. 88%和 92. 60%。 反 应温度和 O2 /H2S 物质的量比对催化剂催化活性有较大影响。 随着反应温度升高，催化剂 的 H2 S 转化率先增大后减小，硫选择性和产硫率则不断减小;O2 / H2 S 物质的量比增加，H2 S 转化率不断升高，硫选择性则逐渐下降，产硫率具有先增加后降低的趋势，在 O2 / H2 S 物质的 量比为 0. 5 时产硫率最大。 反应后催化剂表征分析表明，Fe2 O3 / TiO2 催化剂 H2 S 催化氧化的 主要产物是单质硫和硫酸铁。 此外，提出了 Fe2 O3 / TiO2 催化剂可能的 H2 S 选择性催化氧化机 理，其中 Fe3+ 是主要的活性组分，在 H2 S 选择性催化氧化反应中起主要作用，硫酸铁的生成和 单质硫的沉积为催化剂失活的主要原因。Abstract: Fe2 O3 / TiO2 catalysts were prepared by sol⁃gel method. The physicochemical properties of catalysts were characterized by BET，XRD and XRF，and the activity of catalysts for the selective catalytic oxidation of H2 S was investigated by the fixed⁃bed reaction system. The results show that the specific surface area of the catalyst gradually increases with the increase of loading，and the Fe2 O3 exists uniformly in the catalyst phase in highly dispersed or amor⁃ phous form when the Fe2O3 loading is less than 15%. When the Fe2O3 loading continues to increase to 20%，the spe⁃ cific surface area of the catalysts decreases，the Fe2 O3 exists in the form of crystal and blocks the pore structure of the catalyst surface. With the increase of loading，the H2 S conversion and sulfur yield of Fe2 O3 / TiO2 increase at first and then decrease，while the sulfur selectivity decreases，the 15 % Fe2 O3 / TiO2 catalysts perform well under the condi⁃ tions of reaction temperature 180 °C and the O2 / H2 S molar ratio 0. 5. The H2 S conversion rate，sulfur selectivity and sulfur yield are 96. 57%， 95. 88% and 92. 60%， respectively. The reaction temperature and the molar ratio of O2 / H2 S have great influence on the activity of the catalysts. With the increase of reaction temperature，the H2 S conver⁃ sion rate increases at first and then decreases， while the sulfur selectivity and sulfur yield decrease continuously. With the increase of O2 / H2 S molar ratio，the H2 S conversion rate increases and the sulfur selectivity de⁃ creases gradually，and the sulfur yield increases at first and then decreases，and the sulfur yield is the highest when the O2 / H2 S molar ratio is 0. 5. The analysis of spent catalysts show that elemental sulfur and sulfate are the main product of the catalytic oxidation of H2 S. In addition，the possible catalytic oxidation mechanism of H2 S on the Fe2 O3 / TiO2 catalysts is proposed，in which Fe3+ is the main active component and plays a major role in the selective catalytic oxidation of H2 S. The formation of ferric sulfate and deposition of elemental sulfur are the main reasons for the deacti⁃ vation of the catalysts.
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