Comparison of wall-coated and packed-bed reactors for steam reforming of methanol

The kinetics of methanol steam reforming on a commercial CuO/ZnO/Al2O3 catalyst in packed-bed and wall-coated microreactors were compared experimentally. Different dimensions of both reactor configurations were tested and the transport limitations were analyzed using 2D reactor models. Packed-bed reactors of dimensions from 4.1 down to 1 mm i.d. were found to be heat transfer limited and temperature gradients of up to 40 K could exist in the bed. The reactor diameter required to eliminate temperature gradients was estimated to be 300(mu) m, which clearly is not practical. On the other hand, the wall-coated reactor was found to be free from any mass or heat transfer limitations in dimensions from 4.1 mm down to 200(mu) m i.d. Our modeling results showed that the reactor volumetric productivity increases with thicker catalyst wall-coatings for the same reactor diameter. We also show that the wall-coated reactor offers a better solution to achieve low pressure drop and high catalyst activity compared to a packed-bed microreactor.