Ammoxidation of C2 hydrocarbons over Mo–zeolite catalysts prepared by solid-state ion exchange: Nature of molybdenum species

International audienceSuccessful introduction of molybdenum (from MoCl3) into zeolites of different topologies was carried out using solid-state ion exchange. MOR like support extended the formation of Mo oxides due to its particular aperture/channel-shapes. However, BEA and MFI (ZSM-5) zeolites structures loaded small aggregates of Mo oxide. Exchanging MoCl3 with NH4+–BEA, H+–ZSM-5 (Si/Al = 15) and NH4+–ZSM-5 (Si/Al = 26) led to the consumption of Brönsted acid sites and silanol groups, while the lack of exchange sites in NH4+–MOR generated Mo–OH as revealed by DRIFTS and TPD of NH3. Polymeric Mo and MoO3 occupied the bulk of BEA and MOR issued solids. Nevertheless, NH4+–ZSM-5 (Si/Al = 26) support triggered the formation of dimeric species. For H+–ZSM-5 (Si/Al = 15) solid, monomeric species migrated throughout the channels of H+–ZSM-5, which condensed easily to form rather polymeric species. Small oxide crystallites and Mo moieties that weakly interact with NH4+–BEA and NH4+–ZSM-5 (Si/Al = 26) were easily reduced under hydrogen, while the negatively charged H+–ZSM-5 (Si/Al = 15) framework inhibited the reducibility

Bioethanol transformations over active surface sites generated on carbon nanotubes or carbon nanofibers materials

© Almohalla et al.; Licensee Bentham OpenCatalytic bioethanol transformations over carbon nanomaterials (nanofibers and nanotubes) have been evaluated at atmospheric pressure and in the temperature range of 473-773 K. The pristine carbon materials were compared with these samples after surface modification by introducing sulfonic groups. The specific activity for ethanol dehydrogenation, yielding acetaldehyde, increases with the surface graphitization degree for these materials. This suggests that some basic sites can be related with specific surface graphitic structures or with the conjugated basic sites produced after removing acidic oxygen surface groups. Concerning the dehydration reaction over sulfonated samples, it is observed that catalytic activities are related with the amount of incorporated sulfur species, as detected by the evolution of SO2 in the Temperature programmed Desorption (TPD) as well as by the analysis of sulfur by X-Ray Photoelectron Spectroscopy (XPS).The financial support of the Spanish government by Projects CTQ2011-29272-C04-01 and 03 is recognized.Peer Reviewe