Noble-Metal-Based Catalytic Oxidation Technology Trends for Volatile Organic Compound (VOC) Removal

Volatile organic compounds (VOCs) are toxic and are considered the most important sources for the formation of photochemical smog, secondary organic aerosols (SOAs), and ozone. These can also greatly affect the environment and human health. For this reason, VOCs are removed by applying various technologies or reused after recovery. Catalytic oxidation for VOCs removal is widely applied in the industry and is regarded as an efficient and economical method compared to other VOCs removal technologies. Currently, a large amount of VOCs are generated in industries with solvent-based processes, and the ratio of aromatic compounds is high. This paper covers recent catalytic developments in VOC combustion over noble-metal-based catalysts. In addition, this report introduces recent trends in the development of the catalytic mechanisms of VOC combustion and the deactivation of catalysts, such as coke formation, poisoning, sintering, and catalyst regeneration. Since VOC oxidation by noble metal catalysts depends on the support of and mixing catalysts, an appropriate catalyst should be used according to reaction characteristics. Moreover, noble metal catalysts are used together with non-noble metals and play a role in the activity of other catalysts. Therefore, further elucidation of their function and catalytic mechanism in VOC removal is required.

A Uniform Heating Technique for Cavity in Volatile Organic Compound (VOC) Removal System Using Slotted Waveguide Array

In this study, two types of slotted waveguide are designed in the frequency of 2.45 GHz to improve the microwave heating uniformity of a quadrangular prism-shaped cavity in a volatile organic compound (VOC) removal system. Both types adopt the equivalent circuit approach used for a waveguide slot array antenna. The difference between the two types is the slot impedance extraction method of the waveguide slot array: one calculates the impedance taking the cavity structure into account and the other finds it in free space. Both methods show that the heating uniformity is improved by 52% compared with that of the conventional horn-type feeding structure system according to the simulation results. Even though there is no difference in the heating uniformity between the two models, it is confirmed that the slotted waveguide array feeding model designed by using the impedance data of the slot incorporating the cavity (SAWFM_cavity) has about 6.35 dB better impedance matching characteristics than the other model designed by extracting the impedance data of the slot in free space (SAWFM_free). Also, it is found that the SAWFM_cavity shows more stable impedance characteristics with respect to the loading condition than the SAWFM_free. Therefore, it is concluded that the impedance of the slot should be extracted taking the cavity into account for the design of the slotted waveguide feeding structure since it improves the reflection characteristic as well as the heating uniformity compared with the horn-type feeding structure.