采用紫外线光催化法、沉积-沉淀法、反相胶束法和浸渍法分别制备了催化剂Pd/TiO2-UV、Pd/TiO2-CD、Pd@TiO2、PdfTiO2-JZ,利用一氧化碳-脉冲、氮气吸附/脱附曲线、氢气程序升温还原(H2-TPR)、X射线衍射(XRD)对催化剂进行了表征分析,并测定了各催化剂对直接合成过氧化氢性能的影响.结果表明,Pd/TiO2-UV和Pd/TiO2-CD催化剂催化氢氧直接合成过氧化氢的活性明显高于Pd@TiO2和Pd/TiO2-JZ催化剂,反应0.5 h时单位质量钯合成过氧化氢的产率分别达到1 631.4 mmol/(g·h)和852.3 mmol/(g·h),这是由于催化剂上活性金属钯的颗粒尺寸较小、分散度较大、提供的活性位点较多,有利于更多的反应物分子在活性位上的吸附与活化,提高其合成过氧化氢的活性.其中Pd/TiO2-UV催化剂具有最高的催化活性,这是由于该催化剂上氧化钯含量较少,形成的钯-氧化钯界线较长,导致该催化剂上钯-氧化钯位点的数量更多,提供反应物氢气解离吸附和氧气非解离吸附的活性位点也就越多,催化活性也就越高.%The catalysts Pd/TiO2-UV,Pd/TiO2-CD,Pd@TiO2,and Pd/TiO2-JZ were prepared by Ultraviolet photochemical catalysis method,deposition precipitation method,reverse micelle method,and immersion method respectively,and characterized by CO-pulse,N2 adsorption/desorption isotherms,H2-TPR,and XRD.The data of the catalytic activity tests for the direct synthesis of hydrogen peroxide showed that the activities of Pd/TiO2-UV and Pd/TiO2-CD catalysts were significantly higher than that of Pd@TiO2 and Pd/TiO2-JZ.The yields of H2O2 reached 1 631.4 mmol/(g·h) and 852.3 mmol/(g·h) in the first 0.5 h.This was due to the particle size of Pd on the catalysts was small,and it can provide more active sites,which was beneficial to the adsorption and activation,and to the activity of H2O2.Among them,Pd/TiO2-UV had the highest activity of all because it had less content of PdO,so the Pd-PdO boundary was longer,that led to more Pd-PdO sites on the catalyst,and more active sites of H2 dissociative adsorption,and O2 non dissociative adsorption,therefore the activity of catalyst was higher.
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