Volatile total oxidation

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. 

In selective gas-phase oxidation processes the conversion often does not reach 100%, in order to reduce total oxidation. This means that some starting material and/or intermediate products are present in the reaction mixture. Following separation, these may be recycled into the reaction to avoid yield losses. Although the above may seem obvious, an economical and efficient recycling procedure is not always simple, depending on the volatility of the components involved and the concentration of any unwanted by-products. In practice, a purge is included in the recycle to maintain an equilibrium concentration of by-products. 

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. 

Catalytic oxidation reactions on noble metal surfaces are sufficiently fast and exothermic that they can be operated at contact times on the order of one millisecond with nearly adiabatic temperatures of 1000°C. At short contact times and high temperatures complete reaction of the limiting feed is observed, and highly nonequilibrium products are obtained. We summarize experiments where these processes are used to produce syngas by partial oxidation of methane, olefins by partial oxidation of higher alkanes, and combustion products by total oxidation of alkanes. The former are used to produce chemicals, while the latter is used for high temperature catalytic incineration of volatile organic compounds. 

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

In order to avoid huge losses of volatile boron oxide compounds, the furnace is cooled externally such that the outer shell remains unreacted. The core contains low-impurity boron carbide blocks (total metal impurities <0.5 wt%) with a stoichiometry of B/C = 4.3 and residual carbon [25]. The blocks are crushed, milled to the desired final grain size, and purified by chemical leaching. 

A final example involves gas-phase aging chemistry. In Fig. 9 we show two pToF spectra firom semi-volatile diesel oxidation experiments described elsewhere [127-129]. In these experiments, diesel emissions were diluted to near ambient levels and then exposed to photol34ically generated OH radicals [128]. The pToF data are shown for two key ion fragments, mlz = 57 and 44, which are traditionally indicative of reduced ( hydrocarbon like ) POA and oxidized SOA [130]. In these experiments the total OA concentrations more than doubled in 5 h due to SOA formation. The figure reveals that the mlz = 44 marker characteristic of the SOA remained locked into the mode characteristic of the POA defined by mlz = 57, even as the mlz = 44 abundance increased due to condensation. Data are shown just... 

Scire, S. and Liotta, L.F. (2012) Supported gold catalysts for the total oxidation of volatile organic compounds. Appl Catal. B Environ., 125, 222-246. 

Stege, W.P., Cadiis, L.E., and Barbero, B.P. (2011) Lai Ca Mn03 perovskites as catalysts for total oxidation of volatile organic compounds. CataL Today,... 

O MaUey, A. and Hodnett, B.K. (1999) The influence of volatile organic compound structure on conditions required for total oxidation. Catal. Today, 54 (1),... 

Garcia, T., Solsona, B., Cazorlaamoros, D., Linaressolano, A., and Taylor, S. (2006) Total oxidation of volatile organic compounds by vanadium promoted palladium-titania catalysts comparison of aromatic and polyaromatic compounds. Appl Catal B Environ., 62 (1-2), 66-76. 

On the other hand, methanol is a toxic and pollutant volatile organic compound (VOC) which can be abated by catal5dic total oxidation. 

Different aspects of total oxidation processes are reviewed in the first part of the book hydrocarbon oxidation (Chapter 1) and soot oxidation (Chapter 2) for mobile appficafions while oxidation of volatile organic compounds (VOC) is treated in the next five chapters. Chapter 3 provides a general overview of VOC oxidation while chlorinated VOCs are specifically discussed in Chapter 4 and persistent VOC in Chapter 5. Plasma catalysis processes for VOC abatement are reviewed in Chapter 6. Finally, Chapter 7 gives the point of view of industry for the development and applications of catalysis for air depollution technologies. Total oxidation is also used for energy production by combustion processes exemplified in Chapter 8. The last two chapters are devoted to oxidation processes in liquid media by electrochemical techniques (Chapter 9) or more generally as "advanced oxidation processes" for water depollution (Chapter 10). 

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