The nature of active sites on TiO 2 and TiO 2SiO 2 for the isomerization of butenes : II. Tracer study on the variation of active sites with pretreatments

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The coisomerization of light and perdeuterated cis -2-butene was carried out over TiO 2 and TiO 2 SiO 2 catalysts pretreated under different conditions. The reaction involved an intermolecular hydrogen transfer over the catalysts evacuated at 250 °C, while an intramolecular hydrogen transfer became involved over the catalysts evacuated at 600 °C. Oxygen treatment on the catalysts previously evacuated at 600 °C resulted in the intermolecular hydrogen transfer on TiO 2 SiO 2 , but did not change the intramolecular hydrogen transfer on TiO 2 . These results confirm the variations of the nature of active sites with pretreatment conditions that were suggested in the previous paper.