CATALYTIC PROPERTIES OF METAL-CONTAINING POLYMETHYLSILOXANES

Aluminium-, iron-, titanium- and zirconium-containing polymethylsiloxa nes were studied as catalysts for acid-catalysed reactions; their surf ace acidity and the strengths of their acid centres were determined. T hey appeared to be active for 2-propanol dehydration; the best sample was almost as active as alumina, which is known for its high activity for alcohol dehydration. All metal-containing polymethylsiloxanes (MPS ) catalysed double-bond migration and cis-trans isomerization of 2-but ene. Some of them also catalysed the synthesis of methyl t-butyl ether , but their activity for this reaction was inferior to that of the res in Amberlyst-15 and some of sulphate-ion modified metal oxides. No cum ene conversion occurred on the catalysts studied and no pyridinium ion formation was observed by IR spectroscopy, which points to the absenc e of strong Bronsted acid sites. The MPS are distinguished by quite la rge surface areas (86-299 m(2) g(-1)) and are capable of chemisorbing pyridine (0.014-0.047 mmol g(-1)) on their Lewis acid centres.