Total Oxidation of Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons refer to a group of over 200 chemicals (made up of varying numbers of carbon and hydrogen atoms connected in ring-like forms) that have been cited as carcinogenic and environmentally hazardous substances. They result predominantly from the incomplete combustion of organic compounds and materials (http //envirocancer.cornell.edu) [41,42]. Naphthalene is the most volatile member of this class of pollutants and is typically considered as a model compound of these molecules. 

Literature reports provided arguments demonstrating that the performance of catalysts for the total combustion of alkanes and monoaromatic compounds cannot be directly extrapolated to predict their efficacy for the total oxidation of polycyclic aromatic hydrocarbons [43]. Therefore, the total oxidation of these molecules should consider specific catalytic systems. 

The performance of the oxides in total oxidation of naphthalene is also influenced by the catalysts morphology. Experiments using different shapes showed that the catalytic activity normalized by unit of surface area varied in the order nanorods nanocubes nanoparticles, which was also directly related to the concentration of surface oxygen vacancies as a result of the exposure of (110) and (100) preferential planes [52]. 

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Ntainjua, N.E., Carley, A.F., and Taylor, S.H. (2008) The role of support on the performance of platinum-based catalysts for the total oxidation of polycyclic aromatic hydrocarbons. Catal Today, 137 (2-4), 362-366. 

Torrente-Murciano, L., Gilbank, A., Puertolas, B., Garcia, T., Solsona, B., and Chadwick, D. (2013) Shape-dependency activity of nanostructured Ce02 in the total oxidation of polycyclic aromatic hydrocarbons. Appl Catal B Environ., 132-133, 116-122. 

The development of noble metal catalysts and transition metal oxides for catalytic oxidation of VOCs has been widely reported in the literature. " The review paper published in 1987 by Spivey presents a good overview of catalytic combustion of VOCs. More recent reviews, focusing on the catalytic combustion of a wide range of VOCs by a wide variety of catalysts and on chlorinated VOCs, were published in 2004. In the last two years, two more reviews have been published. These reviews focused on the development of non-noble metal oxide catalysts for catalytic combustion of VOCs and on catalytic combustion catalysts for the removal of polycyclic aromatic hydrocarbons. This review is not intended to be an exhaustive account, but should provide an overview of the current state of research for catalysts used for alkane and aromatic total oxidation. The aim is also to identify the types of catalysts that are likely to be of use in the future, and the obstacles that must be overcome to produce viable catalysts. The development of a catalyst that may be used for the combustion of all classes of compounds under the general term VOC presents a major challenge for future research, as this has not yet been achieved. 

Sparingly soluble (hydrophobic) organic compounds have a high affinity for the NOM component of geosolids. Recent studies of sorption to metal oxides of weakly polar compounds, such as chlorinated benzenes and polycyclic aromatic hydrocarbons (PAHs), suggests that sorption to mineral surfaces in soil is insignificant when the fraction of organic carbon is above -0.01% of total solids (7). Hence, an... 

Ndifor, E., Garcia, T., Solsona, B., et al. (2007). Influence of preparation conditions of nanocrystalline ceria catalysts on the total oxidation of naphthalene, a model polycyclic aromatic hydrocarbon, Appl. Catal. B Environmental, 76, pp. 248-256. 

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