生物还原法制备负载型钯催化剂

将微生物可在常温下还原贵金属离子的特性引入催化剂的制备过程中,利用对Pd2+具有较强还原能力的地衣芽孢杆菌(简称R08)制得负载型Pd催化剂(简称催化剂)。采用X射线光电子能谱(XPS)和透射电镜(TEM)对催化剂进行表征。XPS测定结果表明,室温下R08菌体可将γ-A l2O3载体表面上的Pd2+基本还原为Pd0;生物还原法制得的催化剂的Pd微粒的平均粒径约为5nm。将该催化剂用于2%CO-98%空气(体积分数)混合气的催化氧化反应,CO完全氧化的最低反应温度为60℃,在此温度下催化剂的活性可恒定150h,结果优于相同条件下化学浸渍法制得的催化剂。XPS表征和催化活性评价结果说明,用于CO催化氧化反应的催化剂中单原子Pd活性中心的价态为0~+2。

Preparation of Supported Palladium Catalyst by Bioreduction

Pd catalyst supported on γ-alumina(nanoparticles)with high dispersion was prepared by bioreduction with Bacillus lichenifoumis(strain R08),which was strong in reducing ability of Pd~(2+).Catalysts prepared by bioreduction and impregnation were characterized by means of XPS and TEM.XPS spectra indicated that strain R08 could almost completely reduce Pd~(2+) to Pd~0.TEM images showed that average sizes of Pd particles on catalysts prepared by bioreduction and by impregnation were 5nm and 18nm,respectively.When catalyst prepared by bioreduction was used in oxidization of carbon monoxide to carbon dioxide,the carbon monoxide could be completely oxidized at the lowest temperature of 60℃and activity of catalyst could be maintained at this temperature for 150h.The result was better than catalyst prepared by impregnation.Pd(Ph_2PCH_2PPh_2)_2 supported on γ-alumina was synthesized as catalyst for the oxidation.Results of XPS spectra and activity evaluation indicated that chemical valence state of Pd on active center of catalyst was between 0 and+2.