The role of water in the catalysis on solid heteropolyacids

Heteropolyacids (HPAs) are used as catalysts for many acid reactions in both homogeneous and heterogeneous systems. For Such systems water, as a vapour and/or the crystallization water, plays an essential role. The review surveys the structure of HPA hydrates and the physicochemical properties of HPA-water system. Especially. tendency to the formation of protonated water clusters in the bulk of the solid, together with acid strength and sorption properties are described. The catalytic part of the paper includes following topics: the role of water as a substrate (hydration of olefins), product (dehydration of alcohols) and as water formally not participating in the catalytic reaction (etherification). (C) 2009 Elsevier B.V. All rights reserved.