Kinetics of carbon dioxide reforming of methane via nonequilibrium plasma reactions

Abstract

Summary form only given. CO2 reforming of CH4 not only eliminates two greenhouse gases but also yields syngas which is preferable feedback for synthetic fuel. The conversions of reactants realized via corona plasma reactions were obviously higher than the equilibrium conversions at atmospheric pressure, and the plasma reactions were always rapid. Experimental results reflect the unique kinetics of nonequilibrium plasma reactions. Within nonequilibrium plasma, the temperature of energetic electrons (Te) is far higher than the temperature of other particles (T). The dissociation reactions of energetic electrons with molecules, e + A rarr products, play an important role, so the kinetics of nonequilibrium plasma reactions should be different with that of gas reactions usually explained by the classical collision theory. According to the collision theory, the rate for gas reaction, A + B rarr products, is given by (-d CA/d t) = K1middotCAmiddotCB, and the rate constant Kc is calculated by K1 = (8RTe/pime)0.5middotsigma0 middot(1+E1/RT)middotexp(-E1/RT) where T is the reaction temperature, sigma is the collision cross section, and E1 is the threshold energy. mAB = (mA+m B)/(mAmiddotmB), mA and m B are the molar masses of A and B. We deduced the rate constant K2 of the dissociation reaction in non-equilibrium plasma which may be expressed as K2 = (8RTe/pim e)0.5middotsigma0middot(1+E0 /RTe)middotexp(-E0/RTe). Due to Te being far higher than T and the molar mass of electron m e being far lower than mAB, K2 is far larger than K1 even if sigma0, the collision cross section for the dissociation reaction, is some less than sigma. So the dissociation reactions are very prompt, and the CO2 reforming via nonequilibrium can be rapid and may realize higher conversions. Using our experimental data resulted from CO2 reforming via AC corona plasma reactions, we drew a macroscopic kinetics model expressed as -d CCH4/d t = 0.10 exp (-11.72/W)CCH4 0.53CCO2 1.1 where the W is the input power during the plasma reactions