Abstracto‐Xylene combustion in air over a Pt/γ‐Al2O3 catalyst was investigated in a laboratory reactor at low concentrations typical for depollution applications. The results evidenced a slightly negative influence of o‐xylene concentration on combustion rate. A kinetic model of the combustion process was developed by using the Langmuir‐Hinshelwood mechanism, assuming the surface reaction between adsorbed oxygen atoms and adsorbed o‐xylene molecules as controlling step. The rate expression includes the influences of o‐xylene and water adsorption on the active centers of the catalyst. The estimation of rate expression parameters is based on o‐xylene conversion measurements obtained under conditions free of influences of physical steps.
Catalytic combustion of methyl isobutyl ketone (MIBK) in diluted air mixtures over a commercial Pt/Al 2 O 3 catalyst was experimentally investigated in a continuous laboratory setup. The experimental data were used to develop a kinetic model of the MIBK combustion over the Pt/Al 2 O 3 catalyst. Among the available kinetic theories, the Langmuir-Hinshelwood one proved to be the most appropriate for the obtained data. The kinetic parameters of the formulated rate expression were estimated using both differential and integral methods. The adequacy of the proposed kinetic model and the estimated parameter values were tested by statistical criteria and thermodynamic consistency. The computation results indicate that the integral method, based on a heterogeneous reactor model, is the recommended approach in the estimation of the kinetic parameters for catalytic combustion processes involving volatile organic compounds.
The objective of the work is to investigate the catalytic combustion of white spirit solvent vapors at low concentration in air, typical for depollution applications, on a commercial catalyst, Pt/c-Al 2 O 3 (0.5 wt-% Pt). To study the influence of the main variables on the process kinetics, experiments were performed under various operating conditions (temperature domain: 150-350°C; flow rates: 125-250 mL min -1 ; white spirit concentrations: 220-260 ppmv). The stoichiometry and kinetics of the vapor combustion was described globally by using a pseudo-compound, representing the average molecular weight and the carbon/hydrogen ratio of the mixture. Experimental data were reasonably well correlated by a first order rate expression with respect to the apparent concentration of the lumping pseudocomponent.
The combustion of methyl methacrylate (MMA) over a commercial Pt/γ-alumina catalyst was investigated, in the lean air mixtures specific for the depollution applications. The experiments were performed at temperatures between 150 and 360 °C, with MMA concentrations of 460 to 800 ppmv and the gas flow rates between 200 and 300 mL min-1. The results evidenced a negative influence of MMA concentration on the combustion kinetics. A kinetic model of the combustion process was developed, based on the Langmuir-Hinshelwood mechanism, assuming the surface reaction between adsorbed oxygen atoms and adsorbed MMA molecules as the controlling step. The rate expression included the inhibition effects of MMA and water adsorption on the process kinetics. The MMA combustion process simulations evidenced the significant influences of the bulk gas to catalyst particle mass transfer, on the overall kinetics.
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