Influence of Adding Molybdenum on Structure and Performance of Fe x O y /SBA‐15 Catalysts in Selective Oxidation of Propene

摘要

Mixed iron and molybdenum oxide catalysts supported on nanostructured silica, SBA‐15, were synthesized with various Mo/Fe atomic ratios ranging from 0.07/1.0 to 0.57/1.0. Structural characterization of as‐prepared Mo x O y _Fe x O y /SBA‐15 samples was performed by nitrogen physisorption, X‐ray diffraction, and DR‐UV‐Vis spectroscopy. Adding molybdenum resulted in a pronounced dispersion effect on supported iron oxidic species. Increasing atomic ratio up to 0.21Mo/1.0Fe was accompanied by decreasing species sizes. Strong interactions between iron and molybdenum during the synthesis resulted in the formation of Fe?O?Mo structure units, possibly Fe 2 (MoO 4 ) 3 ‐like species. Reducibility of Mo x O y _Fe x O y /SBA‐15 catalysts was investigated by temperature‐programmed reduction experiments with hydrogen as reducing agent. The lower reducibility obtained when adding molybdenum was ascribed to both dispersion and electronic effect of molybdenum. Catalytic performance of Mo x O y _Fe x O y /SBA‐15 samples was studied in selective gas‐phase oxidation of propene with O 2 as oxidant. Adding molybdenum resulted in an increased acrolein selectivity and a decreased selectivity towards total oxidation products. Adding molybdenum to green Fe x O y /SBA‐15 catalysts induced a pronounced dispersion and electronic effect on supported iron oxidic species. This resulted in both a decreased reducibility and an increased acrolein selectivity during selective oxidation of propene.