Catalysts — controlling reactivity for making solids with elaborate architecture

Heterogeneous catalysts have a central role in the petroleum and chemical industries. The complexity of their structure and texture, and the fine scale of the details of their architecture, place them among the most elaborate man-made solids. We try and suggest the reactivity problems involved in their preparation, activation, ageing and regeneration. Three typical examples are taken : control of active phase profile inside catalyst pellets, activation of hydrodesulfurization catalysts, and synthesis of a still experimental catalyst, namely contamination free tungsten carbide. Those examples, as well as many novel approaches to preparation mentioned in literature, show how multidisciplinary the science of reactivity of solids is. They emphasize the need carefully to take into account coupling effects when controlling reactivity in transformations involving solids