DEHYDRATION OF 2-PROPANOL OVER CU-TI METALLIC GLASSES - EFFECT OF PRETREATMENTS AND REACTION ON THE STRUCTURE AND SURFACE-PROPERTIES

Cu-Ti catalysts, prepared from metallic glass precursors, selectively dehydrate 2-propanol to propylene at 673 K, in contrast to Cu-Zr alloy s or Cu foil, with which mostly dehydrogenation to acetone occurs. The catalytic run at 673 K results in complete crystallization of the bul k of Cu-Ti alloys. A higher activity with a slightly lower selectivity is observed when an oxygen treatment is applied prior to the reaction . The morphology of the as-received Cu-Ti ribbons is substantially alt ered as a consequence of the reaction. The results of N2O titration in dicate that the Cu(0) surface area is very low either in the as-receiv ed state or after the reaction. X-ray photoelectron spectroscopy depth profile measurements demonstrate considerable Cu enrichment in the ne ar-surface region as a result of the reaction. However, on the topmost layer, only Cu(II) species exist. This is in contrast to the case of Cu-Zr alloys, where both Cu(0) and Cu(II) species coexist. The differe nt reaction paths we observe might be attributed to this finding.