活性炭表面性质对Pd/C常温氧化CO的影响

Effects of Surface Properties of Activated Carbon on Pd/C for CO Oxidation at Ambient Temperature

采用等体积浸渍法制备了活性炭负载Pd催化剂(Pd/C),通过正交实验研究了活性炭的种类、催化剂的制备条件等对活性炭负载钯催化剂上CO氧化性能的影响,得到了最优的制备条件。并通过N2吸附、程序升温脱附(TPD)、程序升温还原(H2-TPR)和透射电镜(TEM)等对催化剂进行了表征。正交实验极差分析表明制备各因素对催化剂氧化CO活性影响的次序为:还原剂>活性炭>还原剂用量>还原温度>还原溶pH值。催化剂表征结果表明活性炭的比表面积和孔径分布不是决定Pd/C催化剂性能的关键因素,活性炭的种类、表面组成和性质对催化剂的性能有显著的影响。其中椰壳炭(AC1)表面羧基的活性较高,同时具有较强的表面碱性,有利于活性金属Pd在载体表面的分散,并提高了Pd与载体之间的相互作用,从而使催化剂具有较高的CO氧化性能。提高Pd的担载量,可显著提高催化剂稳定性。以乙二醇作为还原剂,在pH=10,还原温度为60℃的条件下所制备的0.5%Pd/AC催化剂,在反应温度20℃时连续反应120 h仍可保持CO的全转化。

Supported palladium catalyst on activated carbon were prepared by incipient-wetness impregnation method.Orthogonal experiment was used to investigate the effects of the activated carbon source,preparation conditions on the activity of Pd/C for CO oxidation.The samples were characterized by nitrogen adsorption,temperature-programmed desorption（TPD）,H2 temperature-programmed reduction（H2-TPR） and TEM.The factor for catalyst preparation by range analysis was in the following order： reductantthe source of active carbonthe mole ration of reductant to Pdreduction temperaturepH of reducing solution.The results showed that the source,surface composition and properties behaved great influence on the activity of Pd/C,while the surface area and pore distribution of activated carbon did not.The high active of Pd supported on coconut based activated carbon due to the carboxy group and basic sits of support,which were suggested to be available for the improving Pd dispersion and enhancing the interaction between Pd and support.The stability of Pd/C increased with the increasing of Pd loading significantly.0.5%Pd/C prepared by using glycol as reductant,reductant solution pH of 10,reduction temperature of 60 ℃ showed high activity and stability.The CO could still be completely oxidized at ambient temperature after 120 h.