Progress of catalytic oxidation of typical chlorined volatile organic compounds (CVOCs): A review

Chlorinated volatile organic compounds (CVOCs) are still a part of the current atmospheric environmental problems that cannot be ignored, but unlike conventional VOCs, the presence of Cl causes various catalyst deactivations in the catalytic process. In this paper, we focus on six common CVOCs and discuss various behavioral mechanisms of the whole catalytic process from six aspects: catalyst selection, factors affecting the catalytic effect, changes in catalytic behavior in the presence of different gases, catalyst poisoning deactivation behavior, degradation products and degradation mechanisms to provide guidance for further development of low-temperature and efficient CVOCs catalysts.

Catalytic ozonation with vanadium oxide-doped TiO2 nanoparticles for the removal of di-2-ethylhexyl phthalate

Among various plastic additives, di-2-ethylhexyl phthalate (DEHP) has been a great concern due to its high leaching potential and harmful effects on both human and the ecosystem. For the effective oxidation and mineralization of DEHP by ozone in the existing TiO₂ catalytic processes, the heterogeneous catalyst, vanadium oxide (V₂O₅)-incorporated TiO₂ (V₂O₅/TiO₂), was synthesized. The generation of hydroxyl radicals was promoted by cyclic redox reactions of vanadium atoms in V₂O₅/TiO₂ via the increase of surface oxygen vacancies by the replacement of V⁵⁺ species in the lattice of TiO₂. The catalytic ozonation in the presence of V₂O₅/TiO₂ exhibited the significantly higher degradation of DEHP with the pseudo-second-order kinetic constant of 1.7 × 10⁵ mM^-1min^-1 and the removal efficiency of 58.7% after 60 s in 2 mg/L of ozone. The degradation of DEHP was initiated by the shortening of the alkyl-side chain followed by the opening of esterified benzene moieties.

Influence of zirconia addition in TiO2 and TiO2-CeO2 aerogels on the textural, structural and catalytic properties of supported vanadia in chlorobenzene oxidation

This paper studies the effect of the direct incorporation of ZrO₂ in TiO₂ and TiO₂-CeO₂ aerogel supports prepared by sol-gel route on the physico-chemical and catalytic properties of supported vanadia catalysts in the total oxidation of chlorobenzene. The obtained catalysts have been characterized by means of ICP-AES, N₂ adsorption-desorption at 77 K, XRD, XPS, H₂-TPR and NH₃-TPD. The results revealed that Zr-doped V₂O₅ based catalyst is beneficial for the improvement of catalytic properties in chlorobenzene total oxidation. In particular, in the absence of cerium groups, this beneficial effect is correlated with the better acidic properties or/and the stabilization of the V₂O₅ active phase in a higher oxidation state. However, in the case of cerium rich catalyst, this positive effect is much stronger thanks to the enhanced redox properties of V₂O₅/TiO₂-CeO₂-ZrO₂.

How Chemoresistive Sensors Can Learn from Heterogeneous Catalysis. Hints, Issues, and Perspectives

The connection between heterogeneous catalysis and chemoresistive sensors is emerging more and more clearly, as concerns the well-known case of supported noble metals nanoparticles. On the other hand, it appears that a clear connection has not been set up yet for metal oxide catalysts. In particular, the catalytic properties of several different oxides hold the promise for specifically designed gas sensors in terms of selectivity towards given classes of analytes. In this review, several well-known metal oxide catalysts will be considered by first exposing solidly established catalytic properties that emerge from related literature perusal. On this basis, existing gas-sensing applications will be discussed and related, when possible, with the obtained catalysis results. Then, further potential sensing applications will be proposed based on the affinity of the catalytic pathways and possible sensing pathways. It will appear that dialogue with heterogeneous catalysis may help workers in chemoresistive sensors to design new systems and to gain remarkable insight into the existing sensing properties, in particular by applying the approaches and techniques typical of catalysis. However, several divergence points will appear between metal oxide catalysis and gas-sensing. Nevertheless, it will be pointed out how such divergences just push to a closer exchange between the two fields by using the catalysis knowledge as a toolbox for investigating the sensing mechanisms.

Comparative Investigation on Chlorobenzene Oxidation by Oxygen and Ozone over a MnOx/Al2O3 Catalyst in the Presence of SO2

Catalytic oxidation of volatile organic compounds (VOCs) usually encounters complicated components in flue gas causing severe deactivation that restrict its application in specific conditions. The Cl substitution in chlorobenzene further increases poisoning risks. Ozone assistance has unique superiority that can overcome these bottleneck problems. Herein, this study performs a comparative investigation of CB oxidation by oxygen and ozone over a simple Mn/Al₂O₃ catalyst. CB conversion suffered from slight deactivation in oxygen atmosphere (from 90 to 70%) and more severe deactivation in the presence of SO₂ (from 90 to 45%) at 480 °C. Introduction of ozone successfully attained high CB conversion at low temperature (120 °C) with excellent stability and less byproducts. Especially, CB oxidation by ozone maintained its original conversion in the presence of SO₂. The deactivation process was simulated by synthesizing several sulfated catalysts. Direct sulfation on Mn/Al₂O₃ attained more severe deactivation in CB conversion and CO₂ formation than sulfation on the Al₂O₃ support. Ozone with a strong oxidation property promoted the CB oxidation cycle, facilitated desorption of carbonaceous intermediates, and protected MnO_x species from severe erosion, thus exhibiting high and stable performance in CB oxidation.

Mesoporous Ce-doped ZnO hollow microspheres for oxidation of 1,2-dichlorobenzene

ZnCe5 microspheres exhibited excellent activity in o-DCB oxidation due to the enhanced reducibility and high concentration of surface active oxygen.