Recent Development of Catalysts for Removal of Volatile Organic Compounds in Flue Gas by Combustion: A Review

Abstract

Volatile organic compounds (VOCs) emitted from anthropogenic sources pose direct and indirect hazards to both atmospheric environment and human health due to their contribution to the formation of photochemical smog and potential toxicity including carcinogenicity. Therefore, to abate VOCs emission, the catalytic oxidation process has been extensively studied in laboratories and widely applied in various industries. This report is mainly focused on the benzene, toluene, ethylbenzene, and xylene (BTEX) with additional discussion about chlorinated VOCs. This review covers the recent developments in catalytic combustion of VOCs over noble metal catalysts, nonnoble metal catalysts, perovskite catalysts, spinel catalysts, and dual functional adsorbent-catalysts. In addition, the effects of supports, coke formation, and water effects have also been discussed. To develop efficient and cost-effective catalysts for VOCs removal, further research in catalytic oxidation might need to be carried out to strengthen the understanding of catalytic mechanisms involved.

Cobalt-containing BEA zeolite for catalytic combustion of toluene

“…The most commonly studied metal oxide catalysts include Co- [5,[22][23][24][25], Cu- [5,22,26], Mn- [5,22,25], Ce- [5,12,16,26], and Fe-containing materials [21,22]. It has been found that a suitable chosen support with controlled porosity favors high dispersion of active phase and enhanced activity in the total oxidation of VOCs [27][28]. From this point of view, zeolites can be expected as interesting supports of metal oxide species for the abatement of relatively small organic molecules, which can enter and migrate through channels present in the structure of these materials [13-15, 21-22, 29-30].…”

A Comparative Study of Mn/Co Binary Metal Catalysts Supported on Two Commercial Diatomaceous Earths for Oxidation of Benzene

“…These results indicate that the internal structure of the natural diatomite was partially hollow, with internal voids of irregular shapes and broad size distribution. A significant decrease in the quantity of N 2 adsorbed by the samples with the increase of the deposited metal load was also observed (Figure 3a), which was associated with the formation of metal particles in the support's porous structure, causing the complete or partial occlusion of some of the pores [9]. A typical isotherm of pure silica (type II isotherm) was observed during the N 2 physisorption analysis of food-grade diatomite (Figure 3b) [46].…”

“…Aggregates of similar morphology but larger size were also observed on Mn 10 Co 15 /F, as shown in Figure 2l. The formation of larger aggregates observed on Mn 10 Co 15 /F might be related to the lower specific surface area of this support as the higher density of metal particles on the support surface might promote the formation of larger aggregates [9,63]. Figure 9.…”

“…Given the similarities of diatomaceous earths and zeolites, the potential formation of coke on diatomite-supported catalysts was also examined. Transition metals such as Mn and Co in either single or binary metal catalysts have been widely studied for their decomposition activity towards BTEX and, comparatively, the binary active phases generally outperformed the single one [1,9,12,13,38]. Hence, the binary metal catalysts containing Mn and Co were selected in this study, and were prepared by incipient wetness deposition.…”

Air Regeneration of Ethanol-Laden Pellet NaY-SiO2 and Pt/NaY-SiO2: Effects of Air Flow Rate on Pt Morphology and Regeneration Efficiency

“…To improve the process, catalytic components can be added to promote both adsorption and incineration, and the process steps are integrated into a single reactor. In the integrated catalytic/adsorption process, fixed bed reactors containing catalytic adsorbents are employed to continuously adsorb VOCs from the effluents in one bed and convert VOCs on the catalytic adsorbent into benign carbon dioxide and water in the other [5][6][7]. Compared with the conventional adsorber-incinerator, the system is relatively simple, high in VOC removal efficiency, and low in operation and maintenance cost.…”