Enhanced propane dehydrogenation to propylene over zinc-promoted chromium catalysts

Direct propane dehydrogenation (PDH) is an attractive technology for propylene production. We show here that propane conversion is significantly enhanced by the addition of ZnO to Cr2O3. Furthermore, its activity is strongly dependent on the Zn/Cr molar ratio and one with Zn/Cr = 0.3 gives the highest propane conversion and propylene selectivity among the studied ZnxCr catalysts (x denoting the molar ratio, 0-0.5). Characterization with X-ray diffraction, nitrogen physisorption, X-ray fluorescence spectroscopy, temperature-programmed reduction, temperature-programmed desorption, transmission electron microscopy, and X-ray photoelectron spectroscopy indicates that addition of zinc to Cr2O3 leads to formation of a spinel phase and reduction of the particle size, and hence forms more defect sites. The Arrhenius plots suggest that the apparent activation energy of the PDH reaction is significantly lowered over Zn0.3Cr.