Methanol synthesis from syngas over supported palladium catalysts prepared using water-in-oil microemulsion

The hydrogenation of carbon monoxide was carried out over palladium catalysts prepared by a novel preparation method using water-in-oil microemulsion. The catalytic performance of those catalysts was compared with that of the catalysis prepared by the conventional impregnation method. The catalysts prepared by the microemulsion method were found to exhibit a much higher activity for the hydrogenation of CO than those prepared by the impregnation method. The size distribution of the palladium particles of the catalysts prepared by the microemulsion method was remarkably narrow, and the average particle size was much smaller than that of the catalysts prepared by the impregnation method. It was found that palladium particle size of the catalyst was controlled by the preparation conditions of microemulsions, regardless of palladium content. The catalyst prepared at the palladium concentration of 1.0 mol/l had the smallest palladium particles, and exhibited the highest activity. In the case of the microemulsion method, some of the palladium particles were wholly or partially embedded in the support. Nevertheless, the catalysts have exhibited an extremely high activity, because the specific activity of palladium was much higher than that in the case of the impregnated method. Furthermore, the activity of the catalyst prepared by the microemulsion method increased with increasing the amount of palladium exposed to the surface of the support.