Structures of H3PO4/SiO2 catalysts and catalytic performance in the hydration of ethene

The hydration of ethene was carried out over H3PO4/SiO2 having various amounts of H3PO4. The rate of the ethanol formation increased markedly with the increasing H3PO4 loadings, in particular above 60-70 wt%. By X-ray diffraction (XRD), and P-31 and Si-29 MAS NMR methods, it was revealed that various silicon phosphates were produced in the preparation of the catalysts. The structures of the phosphates depended on the H3PO4 loadings. It was suggested that Si(HPO4)(2) . H2O species which formed at higher H3PO4 loadings were hydrolyzed to H3PO4 and SiO2 during the course of the reaction, yielding the catalysts with high performance. The bulk phase of the H3PO4 was involved in the reaction. (C) 1998 Elsevier Science B.V. All rights reserved.