(544fr) Structure/Redox/Reactivity Properties of Dispersed Vanadium Species on TiO2 for the Oxidative Dehydrogenation of Propane with CO2

Authors: 
Wang, H., Rutgers University
Tsilomelekis, G., Rutgers, The State University of New Jersey
Propylene is unambiguously one of the prominent feedstock in a wide range of applications in chemical industry. Since the recent shale gas revolution1, there is large demand of propylene which in turn expedites academic and industrial research interest to develop technologies for ‘on-purpose' production. Direct (DH) and oxidative (ODH) dehydrogenation of propane are currently utilized with the former to be the main source of propylene at the industrial level. Due to the energy consumption under DH conditions, the ODH provides a better alternative due to its exothermicity. However the presence of O2 limits olefin selectivity due to further combustion reactions. Meanwhile, CO2 proves to be a mild and effective oxidant in the reaction process2. Although the choice of CO2 as oxidant has proven to be beneficial on the overall olefin selectivity, questions regarding the mechanism over supported metal oxides (which are the dominant catalytic materials) remain unsettled.

In this work, we aim at developing a model system based on vanadium supported catalysts in order to reveal structural-activity relationships via in-situ Raman spectroscopy for the ODH of light alkanes using CO2. In the first step, we investigate the temperature – dependent evolution of dispersed vanadium species on different metal oxide supports with the ultimate goal to unravel the temperature range that different sites exist on the catalyst surface. We show that above 573K, the vanadium species maintain a mono-oxo configuration in monomeric units. At higher loadings, small crystals of V2O5 observed which are probably getting redispersed upon air treatment at elevated temperatures. The redox behavior of these materials at different temperature ranges as revealed by coupling Raman spectroscopic measurements with labeled C18O2 will be also discussed to pin down the reoxidation mechanisms of V2O5/MexOy in ODH. Relevant catalytic performance data will be presented as an attempt to close the structural-activity relationship loop.

Reference:

  1. Bruijnincx, P. C.; Weckhuysen, B. M., Angew Chem Int Ed Engl 2013, 52 (46), 11980-7.
  2. Zhaorigetu, B.; Kieffer, R.; Hindermann, J. P., Surf. Sci. Catal. 1996, 101, 1049-1058.
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