The methane reforming reaction with carbon dioxide as the oxidant over alumina-supported nickel and gold-doped nickel catalysts is studied using a variety of techniques such as reaction testing, vibrational spectroscopy (inelastic neutron scattering (INS), Raman scattering and infrared absorption), temperature-programmed oxidation (TPO), transmission electron microscopy and X-ray powder diffraction. The quantities of retained carbon and hydrogen are determined by TPO and INS, respectively. Minimal hydrogen retention indicates these catalysts to be very efficient at cycling hydrogen. The relative partitioning of hydrogen within the reaction media is used to formulate a qualitative description of the reaction kinetics. The presence of the gold modifier does not appear to provide any improvement in catalyst performance under the specified reaction conditions.

International audienceThe preparation route has been shown to have a significant influence upon the catalytic behaviour of Ni2Mo3N samples for ambient pressure ammonia synthesis. Materials prepared from a NiMoO4 precursor necessarily contain a significant fraction of Ni impurity phase. Materials prepared from this precursor are relatively inactive for ammonia synthesis, whereas Ni2Mo3N of much greater phase purity and catalytic activity can be prepared from precursors employing a modified Pechini method with the use of citrate gels. Ni2Mo3N can be prepared by N-2/H-2 pre-treatment which represents a significant advantage over routes employing ammonolysis. Bulk lattice nitrogen appears to be relatively unreactive in Ni2Mo3N, although heterolytic nitrogen isotopic exchange studies indicate that a significant degree is exchangeable subject to pre-treatment conditions. The modified Pechini method based route has also been shown to be applicable to the preparation of CoNiMo3N of relatively high phase purity, thereby allowing access to the preparation of quaternary nitrides for catalytic screening

An iron based Fischer-Tropsch synthesis catalyst is evaluated using CO hydrogenation at ambient pressure as a test reaction and is characterised by a combination of inelastic neutron scattering (INS), powder X-ray diffraction, temperature-programmed oxidation, Raman scattering, and transmission electron microscopy. The INS spectrum of the as-prepared bulk iron oxide pre-catalyst (hematite, α-Fe2O3) is distinguished by a relatively intense band at 810 cm(-1), which has previously been tentatively assigned as a magnon (spinon) feature. An analysis of the neutron scattering intensity of this band as a function of momentum transfer unambiguously confirms this assignment. Post-reaction, the spinon feature disappears and the INS spectrum is characterised by the presence of a hydrocarbonaceous overlayer. A role for the application of INS in magnetic characterisation of iron based FTS catalysts is briefly considered.

A catalyst composed primarily of magnetite prepared from red mud via H2 reduction at 300 °C, simultaneously reduced acidity, allowed recovery of carbon, and generated upgradable intermediates from the aqueous fraction of fast pyrolysis oil in a “continuous” process.