Preparation of copper catalyst washcoats for methanol steam reforming in microchannels based on nanoparticles

The demand of fast load alternations for hydrogen generation by methanol steam reforming for automotive fuel cell application may be met in an excellent manner by microstructured reactors. However, catalyst incorporation is difficult in the micrometer size. By the use of dispersed nanoparticles a washcoating procedure was developed and is explained on the basis of a copper catalyst system. The mixing of CuO particles with other necessary materials like ZnO was examined during high energy ball milling (dry mixing) or dispersing the powders in a solution of cellulose derivatives (wet mixing). For the latter technique the shearing of agglomerates and re-agglomeration were investigated for the pure substances using laser diffraction. The influence of ball milling on particle sizes was determined by adsorption experiments and X-ray diffraction. All mixtures were characterized by temperature programmed reduction (TPR) followed by the measurement of the Cu(0) particle size (X-ray diffraction). A special method based upon X-ray structure analysis was applied for determination of the mixing quality. The relationship between these catalyst properties and additional measurements of the catalyst activity/degradation done was obvious.