Abstract
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 (Tig). 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 Tig. 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 Tig 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.
Highlights
Low-temperature carbon monoxide (CO) oxidation is considered a prototype reaction for heterogeneous catalysis
This study reports the experimental data on the catalytic activity, hysteresis, and thermal stability during the CO oxidation over the Pd/SiO2 catalyst, which is found to be intensely the metal-support interaction andand dispersion of parameters
Results obtained from the X-ray photoelectron spectroscopy (XPS) analysis show that the active sites and the state of Pd can provide valuable information on the metal-support interaction in the Pd/SiO2 catalyst through monitoring of the electronic modifications of the Pd surface before and after the CO oxidation
Summary
Low-temperature carbon monoxide (CO) oxidation is considered a prototype reaction for heterogeneous catalysis It has garnered attention in recent years due to its interesting catalytic behavior and the screening of new heterogeneous catalysts [1]. The properties of Pd catalysts are affected by types of support, preparation conditions, and the dispersion of the Pd particles [4]. Stabilization of the catalyst can be attained by anchoring Pd particles on the surface of the support to resist sintering at high temperatures and dispersion in metal oxides, such as silica (SiO2 ) [6]. The heat treatment under oxidation and reduction conditions is crucial for the preparation of supported Pd/SiO2 catalysts Such treatment can induce morphological changes and affect the dispersion of Pd particles resulting from the sintering of the
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