Alcohol coupling to unsymmetrical ethers over solid acid catalysts

A tungstena-zirconia (WZ) catalyst has been investigated for coupling alcohols to ethers and compared with earlier studied sulfated-zirconia (SZ) and Nafion-H catalysts. In all cases, the ether synthesis mechanism is a dual site S N 2 process involving competitive adsorption of reactants on proximal acid sites. The surface acid sites were diagnosed by high resolution X-ray photoelectron spectroscopy (XPS) on N 1s shifts after adsorption of amines. Theoretical study located the transition state and accounted well for XPS core-level shifts upon surface acid-base interactions.