铈锆固溶体CexZr1-xO2上H2S的选择性催化氧化性能

采用共沉淀法合成一系列具有不同Ce/Zr物质的量比的铈锆固溶体Ce_xZr_1-xO₂,考察Ce/Zr比例对H₂S选择氧化反应催化活性的影响。通过XRD、BET、Raman、XPS、CO₂-TPD、O₂-TPD、H₂-TPR等手段对铈锆固溶体的晶体结构、表面性质、碱性位以及氧化还原性等进行表征。结果表明,所有的铈锆固溶体催化剂均可以在化学计量比的氧气下具有优良的低温催化活性,催化活性随着Ce/Zr比例的提高而增加,其中Ce_0.9Zr_0.1O₂活性最高,(160~260) ℃转化率均保持在95%以上,在180 ℃时硫收率可达到97%,这主要是因为Ce_0.9Zr_0.1O₂具有最多的中度碱性位、活性位数量和强的氧化还原性。同时推测Ce⁴⁺为催化反应的活性位,并遵循氧化还原机理。此外,催化剂的失活主要是由于催化剂表面生成硫酸盐物种,消耗了活性组分Ce⁴⁺。

Selective catalytic oxidation of H2S over cerium-zirconium solid solutions CexZr1-xO2

A series of cerium zirconium solid solutions Ce_xZr_1-xO₂ with different Ce/Zr molar ratios (x=0.9,0.7,0.5,0.3,0.1) were synthesized by co-precipitation method.The effects of the Ce/Zr molar ratio on the catalytic activity of H₂S selective catalytic oxidation were investigated.XRD,BET,Raman,XPS,CO₂-TPD,O₂-TPD,H₂-TPR were used to characterize the crystal structure,surface properties,basic sites and redox properties of cerium zirconium solid solutions.The cerium zirconium solid solution catalysts have excellent low-temperature catalytic activities under stoichiometric oxygen.The catalytic activity grows with the increase of Ce/Zr ratio where Ce_0.9Zr_0.1O₂ has the highest catalytic activity.H₂S conversion at (160-260) ℃ is kept above 95% and the sulfur yield can reach 97% at 180 ℃.The reason is that Ce_0.9Zr_0.1O₂ has the largest amount of moderate basic sites and active sites,at the same time,the strongest redox properties.Moreover,Ce⁴⁺ is speculated as the active site of the catalytic reaction and follows the redox mechanism.Additionally,the deactivation of the catalyst is mainly due to the formation of sulfate species on the catalyst surface,consuming the active site Ce⁴⁺.