Fabrication of hierarchically porous MgFe2O4/N-doped carbon composites for oxidative dehydrogenation of isobutane

[Display omitted] •Using MgO as the template synthesize hierarchically porous MgFe2O4/N-C composites.•Acidic and basic sites are coexisted on the surface of MgFe2O4/N-C composites.•Competitive adsorption of CO2 and i-C4H10 happened in isobutane oxidative dehydrogenation.•The lower alkali and higher acid contents may be responsible for the higher catalytic activity. MgFe2O4/N-doped carbon (MgFe2O4/N-C) composites with a hierarchically porous structure were successfully synthesized by the one-pot method using MgO as the template and were investigated for the oxidative dehydrogenation of isobutane with CO2. The catalysts consisting of MgFe2O4 nanoparticles supported on the active carbon (MgFe2O4/AC) and pure MgFe2O4 phase were also prepared for comparison. A series of characterizations with XRD, TEM, XPS and Raman spectroscopy were performed for these materials in order to explore the relationship between the structure and catalytic performance. The high surface area with multiple types of pore structures showed up to 15% iron addition in MgFe2O4/N-C. Furthermore, the effects of acid and base properties on the catalysts were investigated by CO2-TPD and NH3-TPD analyses. Although the coexistence of basic and acidic sites in MgFe2O4/N-C and MgFe2O4/AC samples was observed, the amounts and distribution of the acid and base strengths were very different. The adsorption–desorption of isobutane or preadsorbed CO2 was utilized to examine the conversion of reactants. It was found that the lower alkali and higher acid contents may have been responsible for the increased catalytic activity. The isobutene formation rate on MgFe2O4/N-C exceeded that obtained when using the active carbon as a support and was 50%.