n-Butane oxidative dehydrogenation over VOX-HMS catalyst

The demand for olefins increases in recent years. Oxidative dehydrogenation (ODH) of n-butane is possible alternative to classical dehydrogenation, steam cracking and fluid catalytic cracking processes. The role of particular VOX species supported on hexagonal mesoporous silica (HMS) in oxidative dehydrogenation (ODH) of n-butane was investigated on two sets of VOX-HMS catalysts prepared by wet impregnation and direct synthesis differing in amount and distribution of VOX species. The materials were characterized by XRF, N2-BET isotherms, XRD, SEM, H2-TPR, O2-TPO and DR UV–vis spectroscopy and tested in ODH of n-butane in the range of temperature from 460 to 540 °C. The highest activity and selectivity to olefins were reached on materials with high content of isolated monomeric VOX units with tetrahedral coordination which are generated up to 4–5 wt.% of vanadium. The species with high degree of polymerization participate mainly on total oxidation reactions and those species are formed especially by wet impregnation.

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► VOX units on mesoporous HMS were studied by means of analytic techniques.
► Monomeric VOX units play role of most active and selective site in ODH of n-butane.
► Amount of monomeric units is comparable for synthesized and impregnated samples.
► Presence of Oh-oligomeric units causes decreasing of selectivity to C4-ODH products.
► Higher selectivity to C4-ODH products exhibit samples prepared by direct synthesis.