Effect of precipitants on the catalytic performance of Pd–Cu/attapulgite clay catalyst for CO oxidation at room temperature and in humid circumstances

Abstract

The Pd–Cu/attapulgite clay catalysts were synthesized using a deposition–precipitation method with different precipitants. The as-synthesized catalysts were characterized by ICP-AES, N2-physisorption, XRD, FT-IR, TEM and TPR. Their catalytic activities for CO oxidation were tested by a fixed-bed continuous flow reactor at room temperature and in humid circumstances. The results illustrated that the activity of CO oxidation strongly depended on the precipitant. The best catalytic performance is achieved by using NH3·H2O (PC-AH) or NH4HCO3 (PC-AHC) as precipitants. The crystalline phase of PC-AH and PC-AHC comprised of Cu2Cl(OH)3 and CuO, while the catalysts prepared with NaOH (PC-SH) or NaHCO3 (PC-SHC) as precipitants were mainly CuO. Combined with FT-IR and TEM results, it could be found that Cu2Cl(OH)3 on PC-AH and PC-AHC possessed higher stability than that on PC-SH and PC-SHC due to the different formation process and morphology of Cu2Cl(OH)3 species. The TPR results showed that the Cu2Cl(OH)3 had a strong interaction with Pd species and enhanced reducibility. Moreover, the residual sodium ions on PC-SH and PC-SHC may have adverse effect on the catalytic activity. A suitable precipitant resulted in the most efficient CO oxidation catalyst at room temperature and in humid circumstances.