Effect of gas composition

In order to obtain reasonable concentrations of CHj- radicals in the low pressure studies, reactions were carried out at temperatures > 700 C whereas, the conventional catalytic studies of Vannice and co-workers have been carried out at temperatures 700 °C. Therefore, for comparison with our low pressure results, the effect of temperature on the rate of Nj formation at a total pressure of 760 Torr has been investigated up to 875 °C for three gas compositions (i) 1 % NO, (ii) 1 % NO + 0.25 % CH4 and (iii) 1 % NO + 0.25% CH4 -f- 0.5% Oj. The results are summarized in Figure 7. At 700 °C, the trends with respect to the effect of gas composition are qualitatively the same as those reported by Vannice i.e., the addition of CH enhanced the rate of Nj formation, and the addition of O2 enhanced the rate even more. At 700 C the effect of adding CH4 was to increase the rate two-fold, while the effect of adding CH4 O2 was to increase the rate five-fold. 

Roos, J. A., S. J. Korf, J. J. P. Bicrmann, J. G. van Ommen and J. R. H. Ross. 1989. Oxidative coupling of methane, the effect of gas composition and process conditions. Proc. 2nd Europ. Workshop Meeting, New Developments in Selective Oxidation. Rimini, Italy. 

Figure 8.6 The difference between selectivities calculated from pure gas measurements and selectivities measured with gas mixtures can be large. Data of Lee et al. [13] for carbon dioxide/methane with cellulose acetate films. Reprinted from S.Y. Lee, B.S. Minhas and M.D. Donohue, Effect of Gas Composition and Pressure on Permeation through Cellulose Acetate Membranes, in New Membrane Materials and Processes for Separation, K.K. Sirkar and D.R. Lloyd (eds), AIChE Symposium Series Number 261, Vol. 84, p. 93 (1988). Reproduced with permission of the American Institute of Chemical Engineers. Copyright 1988 AIChE. All rights reserved...

The effect of gas composition and pressure on the temperature range over which the decomposition reaction occurs can be seen by comparing the above results with a TGA study under vacuum.19 The first stage of the decomposition, corresponding to... 

Figure 20.4. Effect of gas composition (proportions of nitrogen and carbon dioxide) in the headspace atmosphere during mixing on the aeration of the dough. (From Campbell, G.M. (2003). Bread aeration. In Bread Making Improving Quality, Cauvain, S.P., ed., Woodhead Publishing, Cambridge, Figure 17.2, p. 360.)...

Fig. 2 Effect of gas composition on hydrocarbon light-off temperature at 50 . conversion.

Fig. 4. Effect of gas composition and temperature of sintering on Pt/Rh crystallite size and alloy formation.

THE EFFECTS OF GAS COMPOSITION AND PROCESS CONDITIONS ON THE OXIDATIVE COUPLING OF METHANE OVER Li/MgO CATALYST... 

Cal,. M.P., Strickler, B.W., and Lizzio, A.A. (2000). High temperature hydrogen sulfide adsorption on activated carbon. I. Effect of gas composition and metal addition. Carbon, 38, 1757-65. 

Effect of gas composition on fracture toughness for carbon steels [29]. 

If external mass transfer is the controlling step or is slow enough to have some effect on the overall rate, steps 1 and 5 should be considered together, since product diffuses outward through the same boundary layer that forms the resistance to reactant diffusion. When the reactant concentration at the surface is much lower than in the bulk gas, the product concentration at the surface will be much higher, and the effect of gas composition on diffusivity may have to be accounted for. There may also be a net flux of molecules to or away from the surface, which must be considered when external mass transfer controls. 

Figure 2.12 Effect of gas composition on the reiative rate of C2H40 formation at 220°C (a) changing ethyiene pressures (b) changing oxygen pressure. (From Ref. 11.) Reproduced with permission of the American Institute of Chemicai Engineers. Copyright 1971 AlChE. Aii rights reserved.

Forero, C.R., Gayan, P., Garcfa-Labiano, F. et al. (2010) Effect of gas composition in Chemical-Looping Combustion with copper-based oxygen carriers Fate of sulphur. International Journal of Greenhouse Gas Control, 4, 762-770. 

Neglecting the effect of gas composition on molecular diffusion. Coefficients of key component in gas mixtures is estimated based on gas composition at external surface of catalyst, and its Knudsen diffusion coefficient and effective diffusion coefficient are calculated based on average pore radius. 

Lerouge S, Wertheimer MR, Marchand R, Tabrizian M, Yahia L. Effect of gas composition on spore mortality and etching during low-pressure plasma sterilization. J Biomed Mater... 

K. Piotrowshi, Effect of Gas Composition on the Kinetics of Iron Oxide Reduction in a Hydrogen Production Process, International Journal of Hydrogen Energy, 30(2005),1543-1554. 

Effect of gas composition and contaminants on the lifetime of surface-treated FeCrAIRE... 

Under isothermal oxidation conditions, the effects of gas composition on the oxidation rates for both iron and the 0.065C-0.29Mn steel were found to be more significant at higher temperatures, with very small differences observed at 700-800°C. 

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