Oxidation of Volatile Organic Compounds

Volatile organic compounds (VOCs) are emitted from chemical plants, vehicles, electroplating, spray-painting, laundries and so forth. They are not only hazardous to 

A comparative study of Ti02-supported noble metal catalysts, which were prepared by impregnation, was carried out for the oxidation of a low concentration of HCHO (100 ppm) by Zhang and He [102], As far as impregnation method is concerned, Au/ Ti02 is less active than Pt/Ti02, giving 90% HCHO conversion at 393 K and 100% conversion at room temperature, respectively. 

As for the complete oxidation of propene, propane and methane, Nieuwenhuys and coworkers studied the influence of metal oxides additives on the catalytic activity of Au/Al203 [109-115], The addition of 3d transition metal oxides (MnOx, CoOx or FeOx), which were active by themselves, or ceria that was poorly active by itself promoted the catalytic activity of Au/Al203 in the total oxidation of propene [112]. The most active catalyst was Au/Ce0x/Al203, with a T95 at 497 K and with a high stability. In these cases, ceria and the transition metal oxides may act as co-catalysts and the role is twofold it stabilizes the Au NPs against sintering (ceria) 

94 3 Unique Catalytic Performance of Supported Gold Nanoparticles in Oxidation 

To study the possibility of application in the reduction of cold start emission, Pitchon et al. tested the reaction of total oxidation of a mixture of light hydrocarbons 

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Ojala, S. (2005) Catalytic oxidation of volatile organic compounds. Doctoral Thesis. Oulu University Press, Finland. 

Holzer, F., Roland, U. and Kopinke, F.-D. (2002) Combination of non-thermal plasma and heterogeneous catalysis for oxidation of volatile organic compounds Part 1. Accessibility of the intra-particle volume, Appl. Cat. B Env. 38, 163-81. 

Environmental applications Oxidation of volatile organic compounds (VOCs) [114] Decomposition of organic dyes [115] Removal of aqueous phenol [116] Superwetting nanowire membranes for selective absorption [117]... 

Luo, J., Zhang, Q., Huang, A. and Suib, S.L. (2000) Total oxidation of volatile organic compounds with hydrophobic cryptomelane-type octahedral molecular sieves. Microporous and Mesoporous Materials, 35-36, 209-217. 

Biofiltration is the removal and oxidation of volatile organic compounds (VOC) from contaminated air by fixed beds of compost, soil, or peat. Biofiltration involves microbial populations immobilized on suitable support media to degrade or transform contaminants using biofilms. 

Fromment and Bishoff (1990) presented the possible expression of each of these terms in various cases, whereas Poulopoulos el al. (2001) have presented various rate laws for the catalytic oxidation of volatile organic compounds, as shown in Table 5.3. 

It is fair to state that by and large the most important application of structured reactors is in environmental catalysis. The major applications are in automotive emission reduction. For diesel exhaust gases a complication is that it is overall oxidizing and contains soot. The three-way catalyst does not work under the conditions of the diesel exhaust gas. The cleaning of exhaust gas from stationary sources is also done in structured catalytic reactors. Important areas are reduction of NOv from power plants and the oxidation of volatile organic compounds (VOCs). Structured reactors also suggest themselves in synthesis gas production, for instance, in catalytic partial oxidation (CPO) of methane. 

Catalyst deactivation in the oxidation of volatile organic compounds by some metal oxides... 

Case histories for the deactivation of commercial Hopcalite and chhromia/alumina catalysts in the oxidation of volatile organic compounds (V0C) are presented. Feeds of pure hydrocarbons, chloro-carbons, and mixtures of the two are considered. Both fixed- and fluid-bed configurations have been studied. Deactivation with mixed feeds is a severe test of V0C catalyst capabilities. There seems here no clear distinction between between the type of reactor, but significant differences between activity and selectivity do exist. A simple model for predicting fixed-bed operation is presented. 

Three commercial processes, namely the oxidation of volatile organic compounds (VOC) for purification of industrial exhaust gases, SO2 oxidation for sulfuric acid production, and NO reduction by ammonia, have employed the periodic flow reversal concept. 

Since natural sunlight can only penetrate a few microns depth, the use of thin films of titania applied to ceramic or metallic supports as maintenance free decontamination catalysts for the photocatalytic oxidation of volatile organic compounds is of interest for the abatement or control of these emissions. The sol-gel technology can be readily incorporated as a washcoating step of the catalyst supports that may be subsequently heat-treated to fix the titania to the support. The surface area, porosity and crystalline phases present in these gels is important in controlling their catalytic activity. Furthermore, the thermal stability and development of porosity with heat-treatment was important if the sol-gel route is to be used as a washcoating step to produce thin films. 

Maira AJ, Lau WN, Lee CY, Yue PL, Chan CK, and Yeung KL. Performance of a membrane-catalyst for photocatal3ftic oxidation of volatile organic compounds. Chem Eng Sci 2003 58 959-962. 

Harris RH, Boyd VJ, Hutchings GJ, Taylor SH (2002) Water as a promoter of the complete oxidation of volatile organic compounds over uranium oxide catalysts. Catal Lett 78 369... 

The reverse-flow chemical reactor (RFR) has been shown to be a potentially effective technique for many industrial chemical processes, including oxidation of volatile organic compounds such as propane, propylene, and carbon monoxide removal of nitrogen oxides sulfur dioxide oxidation or reduction production of synthesis gas methanol formation and ethylbenzene dehydration into styrene. An excellent introductory article in the topic is given by Eigenberger and Nieken on the effect of the kinetic reaction parameters, reactor size, and operating parameters on RFR performance. A detailed review that summarizes the applications and theory of RFR operation is given by Matros and Bunimovich. 

Catalytic total oxidation of volatile organic compounds (VOC) is widely used to reduce emissions of air pollutants. Besides supported noble metals supported transition metal oxides (V, W, Cr, Mn, Cu, Fe) and oxidic compounds (perovskites) have been reported as suitable catalysts [1,2]. However, chlorinated hydrocarbons (CHC) in industrial exhaust gases lead to poisoning and deactivation of the catalysts [3]. Otherwise, catalysts for the catalytic combustion of VOCs and methane in natural gas burning turbines to avoid NO emissions should be stable at higher reaction temperatures and resists to thermal shocks [3]. Therefore, the development of chemically and thermally stable, low cost materials is of potential interest for the application as total oxidation catalysts. 

Spivey [3] reviewed the catalytic oxidation of volatile organic compounds. A number of reported applications of catalytic oxidation are included. 

Catalysts for the oxidation of volatile organic compounds (VOC) are generally supported platinum or palladium catalysts. Copper oxide, vanadium oxide and chromium oxide are suitable for the oxidation of halogenated compounds. 

A knitted silica-fiber was produced and employed as a catalyst support. Different Pt, Pd and Ni/knitted silica-fiber catalysts were prepared. The activity of the catalysts was investigated in oxidation of volatile organic compounds, gas-phase hydrogenation of o-xylene, liquid-phase hydrogenation of citral and liquid phase enantioselective hydrogenation of 1-phenyl- 1,2-propanedione. 

P-23 - Total oxidation of volatile organic compounds - catalytic oxidation of toluene over CuY zeolites... 

In the final chapter Dr Spivey reviews the heterogeneous catalytic oxidation of volatile organic compounds in the context of environmental pollution control. This area of application is much more poorly documented than that of vehicle exhaust control, and, his review is therefore most timely. 

Other secondary chlorine species (atomic Cl, CIO, ClOOCl etc.) have been made responsible for Arctic ozone depletion, whereas the sources of the chlorine atoms are poorly understood (Keil and Shepson 2006). The Cl atom reacts similarly to OH (e. g. in oxidation of volatile organic compounds Cai and Griffin 2006). However, the photolysis of HCl is too slow (even in the stratosphere) to provide atomic Cl. Thus, the only direct Cl source from HCl is due to its reaction with OH, but with a fairly low reaction rate constant (Rossi 2003). There are several chemical means of production of elemental Cl (and other halogens) from heterogeneous chemistry (see Chapter 5.8.2) in the troposphere the photolysis of chloroorganic is not very important, with a few exceptions (see Chapter 5.8.1). 

Methyl halides with > 3 halogens react too slowly k < 10 cm molecule" s ) to give measurable decomposition in the troposphere. As seen from this pathway, the halogen atoms (F, Cl, Br and I) first appear in air. The Cl atom (and other halogens with decreasing rates from F over Cl to Br no reactions with I are described) reacts similar to OH (e. g. in the oxidation of volatile organic compounds Cai and Griffin 2006). 

The objective of present research was to provide a better understanding of the chemical processes involved in production and loss of ozone in the troposphere. This was achieved by providing kinetic and mechanistic data for several reactions of peroxy radicals involved in the photo-oxidation of volatile organic compounds (VOC). Additional aims were to determine the product quantum yields in the photolysis of carbonyl compounds, and to investigate the mechanism in the ozonolysis of alkenes, especially in the presence of water vapour. 

The major aims of the research are the establishment of quantitative mechanisms of atmospheric oxidation of volatile organic compounds. 

Oxidation of volatile organic compounds under low NOx conditions Reactions of peroxy radicals,... 

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