Kinetics of carbon dioxide reforming of methane via nonequilibrium plasma reactions

Summary form only given. CO
₂
reforming of CH
₄
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 (T
_e
) 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 C
_A
/d t) = K
₁
middotC
_A
middotC
_B
, and the rate constant K
_c
is calculated by K
₁
= (8RT
_e
/pim
_e
)
^0.5
middotsigma
₀
middot(1+E
₁
/RT)middotexp(-E
₁
/RT) where T is the reaction temperature, sigma is the collision cross section, and E
₁
is the threshold energy. m
_AB
= (m
_A
+m
_B
)/(m
_A
middotm
_B
), m
_A
and m
_B
are the molar masses of A and B. We deduced the rate constant K
₂
of the dissociation reaction in non-equilibrium plasma which may be expressed as K
₂
= (8RT
_e
/pim
_e
)
^0.5
middotsigma
₀
middot(1+E
₀
/RT
_e
)middotexp(-E
₀
/RT
_e
). Due to T
_e
being far higher than T and the molar mass of electron m
_e
being far lower than m
_AB
, K
₂
is far larger than K
₁
even if sigma
₀
, the collision cross section for the dissociation reaction, is some less than sigma. So the dissociation reactions are very prompt, and the CO
₂
reforming via nonequilibrium can be rapid and may realize higher conversions. Using our experimental data resulted from CO
₂
reforming via AC corona plasma reactions, we drew a macroscopic kinetics model expressed as -d C
_CH4
/d t = 0.10 exp (-11.72/W)C
_CH4

^0.53
C
_CO2

^1.1
where the W is the input power during the plasma reactions