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Offline marshalrj1986

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Rate constant
« on: April 30, 2015, 07:10:28 AM »
I am doing my PG project in reforming methane with carbon dioxide to produce hydrogen and carbon monoxide.
CH4+CO2 :rarrow: 2CO+2H2
I am doing the project using matlab. The catalyst used is activated carbon. the order of methane is 0.5 and carbon dioxide is 0 in the presence of activated carbon. I understand the reaction is a adsorption isotherm reaction. for adsorption the rate constant equation i got is
kads = e(-Ea/RT) P /(2πmkT)0.5
and the rate constant equation for desorption
kdes =A e(-Ea/RT)
the equation to find A the pre-eponential factor while calculated experimentally or Z collision frequency. I am using
Z = NavoσAB(8kBT/(πμ))0.5
the experimental conditions I consider are
Ea for adsorption = 4.55 kJ/mol
Ea for desorption = 14.5 kJ/mol
T = 1273K
P = 1 bar
by calculation the values i got are

kads = 1.5 * 1012

the kdes is calculated considering the hydrogen molecule will desorb the activated carbon.

kdes = 5.34 * 105

I calculated the active sites per m2 of carbon is 2.65 * 1018

the thing worrying in me is i found in a journal paper that the conversion percentage of methane over the activated carbon is 90% at 1273K and what i get is too high.

the rate of surface reaction of CH4 is calculated with the equation found from the web. is

R = kdes * Θn

that is same as the desorption rate of the hydrogen from the surface. is it correct.
I am in a need to know if the equations being used and value of Ea are correct.
if there is an equation to find the activation energy from ΔHr.


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