Heteropolymolybdates-Modified Zirconia as a Solid Catalyst for Ring-Open Polymerization of Tetrahydrofuran

Abstract

Heteropolymolybdates-modified zirconia solid acid catalysts were prepared by dispersing molybdophosphoric acid (MPA) on zirconium hydroxide (ZH) and calcining the MPA/ZH materials at 750 °C. The initial loadings of MPA on ZH were 5-25 wt%. The catalysts were characterized by N2adsorption, XRD, FTIR, Py-IR, and NH3-TPD analysis, and they were used as catalysts for the ring-open polymerization of tetrahydrofuran. The results show that, after calcination at 750 °C, the major molybdenum species are zirconia-anchored polymolybdate surface species and ZrMo2O8. The catalysts show both Brönsted and Lewis acidities, and the catalyst with 15% loading has the highest total acidity and catalytic activity because of the near-saturation coverage of the surface molybdenum species on support. Under the reaction conditions of 40 °C for 20 h, the catalyst sample, 15MPZ-750, gives a high polymer yield of 49% and a desirable number average molecular weight of 2262. A preliminary recycle study indicates a good reusability of these materials.