The kinetics of methanol decomposition: a part of autothermal partial oxidation to produce hydrogen for fuel cells

Methanol is considered as a renewable energy source for fuel processor-fuel cell systems. The determination of the kinetics of methanol autothermal pa rtial oxidation can be simplified if the problem is divided into subproblem s. As a first step, the kinetics of methanol decomposition (Me) are studied . To describe this subproblem, a reaction system consisting of four reactio ns is assumed. The reactions are: Me, dimethyl ether (DME) formation, steam reforming, and water gas shift (WGS) which are studied on a commercial cop per containing catalyst (5 wt.% copper on alumina). The dehydration of meth anol to DME is a second order reaction and essentially provides an excess o f water over the whole reactor allowing first order kinetic assumptions for steam reforming and WGS. The WGS reaction proves to be slow, compared to t he other reactions, and equilibrium limited. The activation energies (kJ/mo l) are estimated: Me 76 (+/-4%), DME formation 117 (+/-2%), steam reforming 81 (+/-7%), WGS 50 (+/- 25%). Turnover frequencies for Me are estimated ba sed on copper surface areas determined by the nitrous oxide pulse reduction method. At 220 degreesC, values of 0.05 s(-1) are estimated compared to a literature value of 0.019 s(-1) at 200 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.