焙烧温度对Pd-Cu/凹凸棒土CO常温催化氧化性能的影响

以凹凸棒土(APT)作载体,采用等体积浸渍法制备了Pd-Cu/APT催化剂,以CO氧化为探针反应,在连续流动微反装置上,考察了焙烧温度对催化剂CO常温催化氧化性能的影响。通过N2-物理吸附、XRD、TG、FT-IR和H2-TPR等手段对催化剂的结构和性质进行了表征。结果表明,随焙烧温度升高,Pd-Cu/APT中载体逐步脱水,进而引起催化剂结构和织构变化,其中,Cu物种由Cu(OH)Cl逐渐向CuO转变,同时,高分散的Pd物种与Cu物种间相互作用先增强后减弱。经300℃焙烧的催化剂比表面积大,Cu物种以Cu(OH)Cl形式存在,且具有良好的分散状态,与Pd物种之间产生较强的相互作用,显著提高了其还原性能。在空速6 000 h-1、CO体积分数0.5%、水蒸气体积分数3.3%的反应条件下,常温可将CO完全转化800 min以上。焙烧温度高于或低于300℃均引起CO常温催化氧化性能的下降。

Effect of calcination temperature on catalytic performance of Pd-Cu/attapulgite clay catalyst for CO oxidation at room temperature

Using attapulgite clay(APT) as the support, the catalysts Pd-Cu/APT were prepared by wet impregnation method. The effect of calcination temperature on the catalytic performance for CO oxidation at room temperature was investigated in a fixed-bed continuous flow reactor. Structure and property of the catalysts were characterized by N₂-physisorption, XRD, TG, FT-IR and H₂-TPR. The results showed that as the calcination temperature increased, structure and texture of the catalysts changed due to the desorption of water in the support. Cu species changed from Cu(OH)Cl to CuO gradually, while interactions between highly dispersed Pd and Cu species increased firstly and then decreased. The catalyst calcined at 300 ℃ possessed the highest surface area, dispersed Cu(OH)Cl, and strong interaction between Pd and Cu species, which significantly improved the reducibility of the catalyst. At the reaction conditions of CO 0.5%, GHSV 6 000 h^-1, water content 3.3% and room temperature, the catalyst was able to maintain its activity for CO complete oxidation more than 800 min. Calcination temperatures higher or lower than 300 ℃ caused the lower catalytic activity.