Catalytic Removal of Volatile Organic Compounds

The degradation of air quality by the release of volatile organic compounds (VOCs) into the air particularly harms human health and our environment. Regulation of outdoor VOC emissions is required to prevent the formation of ground-level ozone, which is principally responsible for photochemical smog. Indoor emissions of VOCs have been the subject of recent consideration for many governments around the world because of the adverse impact of VOCs on the health of people exposed to them. Because VOCs are numerous and varied, they include alkanes, aromatics, chlorinated hydrocarbons, alcohols, aldehydes, ketones, esters, etc., many technologies have been developed to control their emissions. Depending on their toxicity, concentration, presence or lack thereof in a mixture, and market value, the removal of VOCs from air can be achieved by recovery or destructive processes. Heterogeneous catalytic oxidation is regarded as the most promising technology to control VOC emissions with low energy consumption and with selective conversion into harmless molecules [1]. The high volume and low VOC concentrations in air could require the coupling of the catalytic oxidation process with other technologies such as adsorption and non-thermal plasma (NTP) in order to control the emissions while reduced operating costs [2]. This special issue covers promising recent research and novel trends in the fields of outdoor and indoor VOC abatement using different technological approaches and including recent developments in material chemistry to achieve more efficient processes. This special issue collects three reviews and nine articles. The review by Satu Ojala et al. [3] summarizes the commercially existing VOC utilization possibilities and presents utilization applications that are in the research phase. The authors introduce some novel ideas related to the catalytic utilization possibilities of the VOC emissions and underline that catalysis offers not only a way of VOC removal and reduction of their atmospheric reactivity and harms in the working environment but also provides excellent options for novel and sustainable products. Applications of carbon-supported catalysts for VOC catalytic oxidation are reviewed by Francisco José Maldonado-Hódar et al. [4]. The authors examine the extent to which carbon-based materials in association with noble metals (Pt and Pd) can be used as catalysts for benzene, toluene and xylenes elimination. In particular the authors point out the influence of the support of hydrophobicity and mesoporosity on the catalyst performances. The review by Sharmin Sultana et al. [5] identifies potential research applications of the abatement of VOCs as well as of the regeneration of adsorbents using a newly developed innovative technique, i.e., the cyclic operation of VOC adsorption and plasma-assisted regeneration. The authors clearly show the influence of critical process parameters on the adsorption and regeneration steps and highlight the direction of the future work on this topic which must be focused on for the feasibility and optimization of the duration of the sequential intervals. Two articles focus on the combination of NTP with catalysis as a feasible way to overcome the poor selectivity towards the target compounds and low energy efficiency of the use of NTP alone. Yoshiyuki Teramoto et al. [6] study the reaction mechanism of the zeolite-plasma hybrid system for toluene decomposition. Using different configurations of the zeolite hybrid reactor, the authors show that the main factor enhancing the reaction mechanism is ozone species produced by the plasma which