Amorphous titanium hydrogenphosphate?an inorganic sorbent and a catalyst

Abstract

Amorphous titanium hydrogenphosphate, originally prepared to act as an inorganic sorbent superior for K+ and other alkaline metal ions of certain size, proved to be also an active catalyst in alcohol dehydration. Its activity was tested in cyclohexanol, methanol, and pentanol conversions. The reactions were selective and thus cyclohexene was practically the only product of cyclohexanol dehydration, methanol gave dimethyl ether (DME) as the main product and pentanol yielded pentene isomers, the mutual ratios of which depended on temperature and contact times. Characteristically, the studied catalysts acquired their high activity only after a period of work at temperatures higher than 275 °C, the temperature of an endothermic transition observed in DTA. After the catalyst had been activated, it retained its activity even while working at lower temperatures, but lost it upon staying at room temperature for longer times. Most probably, these changes are related to the increase in the interlayer distance and the insertion of water and alcohol, making thus the inner acidic sites available for the reaction.