Thick and porous aluminum oxide coatings on the inner walls of a microchannel reactor have been developed as a support for catalytically active metals serving for on-board hydrogen production. These coatings must withstand extremely severe conditions in terms of temperature and mechanical shock. The developed suspension coating method uses alumina prepared from commercial powders. Optimizing the slurry preparation parameters such as particle size, viscosity, solid loading and/or binder content in tight relationship with coating properties allowed us to attain films at a desired thickness of 25 mu m, with a good adhesion and reasonable uniformity. An ongoing investigation in our laboratory confirms that these coatings impregnated with an active phase can be successfully employed for hydrogen production by steam reforming of isooctane. (c) 2007 Elsevier B.V. All rights reserved.