氨浓度对氨蒸发法制备Pd-Cu/凹凸棒土催化剂常温CO氧化性能的影响

以凹凸棒土(APT)作载体,采用氨蒸发法制备了Pd-Cu/APT催化剂,以CO氧化为探针反应,在连续流动微反应装置上,考察了初始氨浓度对催化剂CO常温催化氧化性能的影响。通过N₂-physisorption、XRD、FT-IR、TEM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,在较低或过高氨浓度条件下,制备的Pd-Cu/APT中Cu物种均主要以CuO为主,仅有少量Cu₂(OH)₃Cl;适宜的氨浓度有利于稳定Cu₂(OH)₃Cl物相的形成,其薄片状的形貌特征、良好的分散状态以及与Pd物种间较强的相互作用,显著提高了CO催化氧化性能。在空速6 000 h^-1、CO体积分数1.5%、水蒸气体积分数3.3%的反应条件下,Pd-Cu/APT催化剂表现出优异的CO室温催化氧化活性和稳定性。

Effect of ammonia concentration on the catalytic activity of Pd-Cu supported on attapulgite clay prepared by ammonia evaporation in CO oxidation at room temperature

With attapulgite clay (APT) as support, the Pd-Cu/APT catalysts were prepared by an ammonia evaporation method and characterized by N₂-physisorption, XRD, FT-IR, TEM and H₂-TPR. The effect of ammonia concentration on the catalytic performance of Pd-Cu/APT in CO oxidation at room temperature was investigated in a fixed-bed continuous flow microreactor. The results showed that CuO appears as the main Cu species in the Pd-Cu/APT catalysts prepared with over low or over high ammonia concentration, whereas the quantity of Cu₂(OH)₃Cl phase is much less. However, a proper concentration of ammonia is of benefits to forming stable Cu₂(OH)₃Cl species in Pd-Cu/APT; owing to its high dispersion, nano-platelet morphology and strong interaction with Pd species, the presence of stable Cu₂(OH)₃Cl can significantly promote the catalytic performance of Pd-Cu/APT in CO oxidation. Under a gas hourly space velocity (GHSV) of 6 000 h^-1 for a feed stream containing 1.5% CO and 3.3% water, the Pd-Cu/APT catalyst exhibits excellent activity and stability in CO oxidation even at room temperature.