The search for efficient and durable catalysts for volatile organic compounds oxidation is essential for environmental remediation. Herein, porous coral-like cobalt–manganese oxide (CoMnO x ) catalyst was synthesized through annealing Co–Mn–1,3-propanediol precursors at 300 °C in air and applied for the catalytic oxidation of benzene. The as-prepared CoMnO x exhibited uniform porous coral-like structure, with an improved benzene catalytic abatement performance as compared to those of Mn3O4 and Co3O4 samples prepared by the same method, respectively. According to BET, H2-TPR, O2-TPD, and XPS analysis, the as-obtained CoMnO x catalyst showed the highest BET surface area, better low-reducibility temperature, and high content of absorbed oxygen groups when compared to Mn3O4 and Co3O4, which makes significant contribution to its catalytic benzene oxidation activity. Moreover, a plausible surface reaction mechanism for benzene oxidation over CoMnO x catalyst was also proposed through the in situ DRIFTS study.
Shrimp waste (SW) was calcified to CaCO3 and CaO with variant morphologies by simple calcination in air and used as efficient support for Pd NPs (<7 nm) in benzene oxidation. A combination of in situ diffuse reflectance fourier transform (DRIFT), hydrogen temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were utilized to study the physicochemical properties and reveal the possible oxidation mechanism. The existence of both Pd2+ and Pd0 was essential for the oxidation activity. The 0.5-Pd/SW@600 catalyst with low activation energy (E a = 50 kJ/mol) presented the best activity among the calcified SW supports. The observed performances correlated with the high Pd metal dispersion, the nature and morphology of the support, and the synergistic effect between the small Pd NPs and the SW support. In addition, the catalyst showed desirable stability and exceptional reusability, being highly resistant to CO2 and H2O vapor. Considering their green, high efficiency, but cost-effective nature, the biogenic Pd/SW catalysts are promising catalysts, and a million tons of SW can find application as support in benzene abatement.
A lot of different chemical reactions take place in the biochemical process of biogas formation but the most important of them include the reaction of bonding carbon dioxide with hydrogen and the decomposition of acetic acid. Other factors, such as temperature, pH, etc., only limit the amount of methane or, in extreme cases, they even stop the process of methane formation. The paper presents an analysis of the influence of the amount of available carbon in the substrate and inoculum on biogas production, as well as of the validity of the relation between methane production and carbon/hydrogen ratio which is often mentioned in the literature. The analyses were made on the basis of the results of several dozen laboratory experiments on methane production for five groups of substrates: cultivated plants, animal faeces, plant waste, animal waste and municipal waste. This provided the basis for the formulation of the conclusion that there is no significant relation between the carbon/hydrogen ratio and methane production, and an alternative biogas calculator was suggested to estimate methane production with the known content of carbon in the substrate and inoculum. This calculator was also adapted to the conditions of agricultural biogas plants, and then it was tested in those conditions. It should also be mentioned that the innovative aspect of the study presented herein is the model developed for the estimation of methane production on the basis of carbon content only, providing estimates with a smaller error than in the case of the calculators!
Volatile organic compounds (VOCs) are a great threat to the health of human beings, and developing catalysts with prominent activity and stability to eliminate them are highly desired. In this work, carbon-based Pt catalysts toward lowtemperature benzene catalytic combustion were prepared through a photodeposition strategy using three-dimensional expanded graphite (EG), bulk graphite, and active carbon as supports. It was found that the Pt/EG catalyst demonstrated the best catalytic performance for benzene oxidation (T 100 = 180 °C) under a high flow rate of 120,000 h −1 . Brunauer−Emmett−Teller, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, and temperature-programmed decomposition techniques were applied to explore the structure−activity relationship. The results indicated that the adsorption capacity and the electron transfer property caused by the Pt nanoparticles and EG support led to a good catalytic performance. Moreover, the 0.5 Pt/EG catalyst also showed excellent stability, good water resistance properties, and high recyclability, which can be used as a promising candidate for practical VOC catalytic combustion.
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