H-1, P-31 NMR MAS, INFRARED AND CATALYTIC STUDIES OF HETEROPOLYACID H3PW12O40 SUPPORTED ON MGF2

H-1 and P-31 NMR MAS spectra of heteropolyacid H3PW12O40 (HPA) support ed on high dispersed MgF2 suggest the change of the structure of HPA c ompared with crystal HPA due to interaction with the support. H-1 NMR spectra at HPA content below 3 wt% do not reveal the H-1 NMR line from protons attached to HPA. In the samples with HPA content larger than 3 wt% the H-1 NMR line with delta approximate to 5 ppm was attributed to protons in isolated heteropolyanions bonded with support surface. A t HPA contents larger than 20 wt% the crystals of HPA on MgF2 surface are formed; this follows from appearance in H-1 NMR spectra of a line at delta = 9.3 ppm typical for crystalline HPA. P-31 NMR and IR spectr a suggest the destruction of HPA structure at low (less than 3 wt%) lo ading, and its preservation at larger HPA contents. The F-19 NMR signa ls were found in methanol after dissolving of HPA supported on MgF2. C atalytic measurements show the drastic increase of activity of HPA/MgF 2 catalysts in reaction of isobutylene oligomerization on increase of HPA content.