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Volatile organic compounds (VOCs) are poisonous and regarded as the paramount source for the formation of secondary organic aerosols, ozone, and photochemical smog, greatly affecting human health and environment quality. In order to abate VOC emission, catalytic oxidation is widely applied in industries and is believed to be an efficient and economically feasible way for the elimination of VOCs. This review is primarily concentrated on summarizing the recent progress and developments in the catalytic oxidation of various VOCs over Pd-supported catalysts. Despite their high catalytic performances at much lower temperatures, the wide use of Pd-supported catalysts in the industry has been limited by their high cost, low thermal stability, and incomplete oxidation of VOCs. Hence, the intrinsic properties of the active sites and supports, the reaction conditions, the deactivation mechanism, and the strategy to reveal the catalytic oxidation pathway are also systematically summarized. This review aims to give a deep comprehension and guidance for the development of efficient and cost-effective Pd-supported catalysts in the near future.

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The present study aims to further understanding of the principal reactions that occur during coal oxidation at moderate temperatures. Mass change and heat evolution of a sample were monitored by thermo-gravimetric analysis coupled with differential thermal analysis (TGA/DTA). Gaseous and solid products were traced using online or in situ Fourier transform infrared spectroscopy (FTIR). Measurements were conducted by heating the samples up to 400˚C, with the O 2 concentration in the reaction medium set at 0, 10, 21, and 40 vol%, respectively. It was observed that the mass increase of a sample between 150˚C and ~275˚C was a result of the accumulation of C=O containing species in the coal structure, whereas substantial mass loss and heat evolution of a sample at ~400˚C can be attributed to the significant involvement of the direct "burn-off" reaction. Enrichment of O 2 in the reaction medium leads to the acceleration in oxygen chemisorption, formation and decomposition of the solid oxygenated complexes, as well as the "burn-off" reaction. With the temperature increasing, the oxidation process governed by oxygen chemisorption gradually shifts to that by significant decomposition reactions, and eventually to that by the direct "burn-off" reaction. Temperature boundaries of these stages can be determined using parameters defined based on a set of TG/DTA data. Shift in the governing reactions is essentially due to the diverse requirements of reactants of the reactions and their energy barriers to be overcome. In engineering practice, the phenomena of self-heating and spontaneous combustion of coal correspond to chemisorption and the direct "burn-off" reaction, respectively.

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The development of atomic dispersed Pd site catalyst is attractive for maximizing metal utilization and reducing the dosage of Pd in the catalytic combustion of atmospheric volatile organic compounds (VOCs)....