CO Oxidation Efficiency and Hysteresis Behavior over Mesoporous Pd/SiO₂ Catalyst

• Main Authors: Rola Mohammad Al Soubaihi, Khaled Mohammad Saoud, Myo Tay Zar Myint, Mats A. Göthelid, Joydeep Dutta
• Format: Article
• Language: English
• Published: MDPI AG 2021-01-01
• Series: Catalysts
• Subjects: CO oxidation; hysteresis; thermal stability; pretreatment; structure-activity
• Online Access: https://www.mdpi.com/2073-4344/11/1/131

Carbon monoxide (CO) oxidation is considered an important reaction in heterogeneous industrial catalysis and has been extensively studied. Pd supported on SiO₂ aerogel catalysts exhibit good catalytic activity toward this reaction owing to their CO bond activation capability and thermal stability. Pd/SiO₂ catalysts were investigated using carbon monoxide (CO) oxidation as a model reaction. The catalyst becomes active, and the conversion increases after the temperature reaches the ignition temperature (T_ig). A normal hysteresis in carbon monoxide (CO) oxidation has been observed, where the catalysts continue to exhibit high catalytic activity (CO conversion remains at 100%) during the extinction even at temperatures lower than T_ig. The catalyst was characterized using BET, TEM, XPS, TGA-DSC, and FTIR. In this work, the influence of pretreatment conditions and stability of the active sites on the catalytic activity and hysteresis is presented. The CO oxidation on the Pd/SiO₂ catalyst has been attributed to the dissociative adsorption of molecular oxygen and the activation of the C-O bond, followed by diffusion of adsorbates at T_ig to form CO₂. Whereas, the hysteresis has been explained by the enhanced stability of the active site caused by thermal effects, pretreatment conditions, Pd-SiO₂ support interaction, and PdO formation and decomposition.