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Catalytic oxidation of organic pollutants

100%

Parus W., Paterkowski W.

Polish Journal of Chemical Technology

2009

vol. 11

issue 4

30-37

The paper presents the results of the measurements of the catalytic activity of V2O5/TiO2 and MoO3/TiO2 catalysts (8,10,12 and 15 wt % of V2O5 or MoO3 on TiO2 - anatase, respectively), prepared in our laboratory, in the complete oxidation (combustion) process of chosen volatile organic pollutants of the air such as methanol and n-butyl acetate. The activity of these catalysts was compared with the activity of industrial catalysts: supported platinum - Pt-p (0.15 wt % of Pt on γ-Al2O3) and MCA (15 wt % of CuO and 6 wt % of ZnO on γ-Al2O3). The investigations were carried out in the kinetic region (powder of the catalysts with the diameter in the range of 1.02-1.2·10-4 m) and for the chosen catalysts also in the diffusion region (the grains of the catalysts having the diameter of 2.5·10-3 m). On the basis of the obtained results the analysis of the process was performed.It has been stated that reaction rate is well-described by the first order equation in relation to the methanol or n-butyl acetate concentration. On the basis of the obtained results in the kinetic region for all the applied catalysts the parameters of Arrhenius equation were determinated.The comparison of the results for the kinetic region with the results for the diffusion region for the chosen catalysts allowed the calculation of the effective coefficients of diffusion. The parameters of Arrhenius equations as well as the effective coefficients of diffusion show a good correlation with the values obtained for the catalytic combustion of other organic pollutants of the air.The measurements were carried out using a flow tubular reactor. The flow rate of the reaction mixture was kept constant 20 dm3/h (5.56·10-6 m3/s) in each test, using the space velocity of 20 s-1. It has been stated that the use of the applied catalysts led to the almost total oxidative destruction of both pollutants. Only H2O and CO2 were found as the final products of the reaction. The complete oxidation of the methanol process runs at the lower temperature than that of the complete oxidation process of n-butyl acetate. The most active at the combustion of methanol was the Pt-p catalyst. It demonstrates a comparable activity to molybdenum - titanium catalysts and the slightly lower activity than vanadium - titanium catalysts in the combustion of the n- butyl acetate process. The MCA catalyst was less active than the others in the oxidation of both compounds. The structures of the catalysts were tested using the X -ray analysis (XRD), infrared spectroscopy and scanning microscopy (SEM).The results of the investigations show that V2O5/TiO2 and MoO3/TiO2 catalysts, especially the most active of them the 8% V2O5/TiO2 catalyst can be used in industrial systems for the purification of the air and industrial waste gases with VOCs, replacing the more expensive noble metals supported catalysts.

Destructive oxidation of ethanol in the corona discharge reactor

81%

Paterkowski W., Parus W., Kalisiak S.

Polish Journal of Chemical Technology

2009

vol. 11

issue 4

57-62

The results of investigation of ethanol destructive oxidation (model aliphatic alcohol) in a corona discharge reactor are presented. The process was performed at the temperature of 303 K in the corona discharge generator - the reactor system manufactured in our laboratory. The process temperature was kept constant by cooling down the reactor with a stream of air. The measurements were carried out using the following process parameters: the inlet ethanol concentration in the stream of gases in the range of 0.0028 to 0.132 mol/m3 (0.128 ÷ 6.086 g/m3), the gas flow velocity in the range of 0.15-0.33 m3/h (space velocity in the range of 1220 ÷ 2680 m3/(m3R ·h)) and the power supply to the reactor ranged from 1.6 to 86.4 W. The active volume of the reactor was 1.23·10-4 m3. The phenomenological method was applied for the description of the process. It was based on the assumptions that the reaction rate can be described by the first order equation in relation to the ethanol concentration and the design equation of flow tubular reactor can be applied for the description of corona reactor. The usefulness of this model was estimated using statistical methods for the analysis of the experimental results. The Statistica 6.0 software was used for this application. The first stage of this analysis showed the dependencies between the considered variables, whereas the second stage was to find the equations describing the influence of the selected process parameters on the rate of ethanol destruction. The parameters of A and B of apparent constant rate equation given in the form of Z = A·exp(-B/P) were also determined.The results of the investigations indicated that the applied corona discharge generator - reactor system assures a high efficiency of purification of the air and industrial waste gases contaminated by ethanol. The ethanol destruction degree of αi = 0.9 was obtained at the power supply to the reactor amounting to 650 kW/m3R per unit of its active volume. The final products of the reaction were only the harmless carbon dioxide and water vapour. It has been stated that the rate of the destructive oxidation of ethanol reaction is well described by the first order equation in relation to the ethanol concentration. Under isothermal conditions, the reaction rate also depends on the power supply to the reactor. This dependence is well described by the empirical equation Z = 3,233·exp(-82,598/P).The obtained results also indicated that the method of destructive oxidation of ethanol in the corona discharge reactor can be useful for the removal of ethanol and probably other aliphatic alcohols from different gases. The described method of calculation of the real rate of the process can be successfully used in the design of corona discharge reactors applied for such processes.

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2 Polish Journal of Chemical Technology

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Catalytic oxidation of organic pollutants

Destructive oxidation of ethanol in the corona discharge reactor