https://nova.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:37281 2O over Fe-ferrierite (Fe-FER) catalyst prepared by solid-state ion-exchange method at moderate temperatures was studied using spectroscopic and solid characterization techniques including H₂ temperature-programmed reduction (H₂-TPR), N₂O temperature-programmed desorption (N₂O-TPD), and in situ Fourier transform infrared (FTIR). The utilization of active oxygen species for the direct conversion of methane to value-added products at moderate temperatures was investigated. The active oxygen sites for the selective conversion of methane were identified by a TPR feature at 220 °C. This site is also characterized by an infrared band observed at 1872 and 1892 cm^-1 upon adsorption of NO. These bands are NO stretching vibrations of NO adsorbed on iron oxygen monomeric species, present in the zeolite cages and responsible for selective oxidation. We show that these oxidized species react with methane to form oxygenates but at higher temperatures form molecular oxygen. IR bands of surface methoxy groups were observed in significant concentration in the FTIR spectra and are suggested to be intermediate species of the selective oxidation of methane. Studies using continuous reactors demonstrated that cofeeding of methane and N₂O-promoted generation of desired products from methane conversion by N₂O over Fe-FER catalyst can be enhanced by optimizing the feed ratio of CH₄/N₂O. Furthermore, N₂, O₂ and NO were detected as the products of N₂O decomposition over Fe-FER catalysts.]]> Wed 19 Jul 2023 10:27:37 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:42039 Wed 17 Aug 2022 12:13:19 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:45435 2O₃ catalyst for the hydrogenation of carbon oxides, in the presence of light hydrocarbons, was studied. Ni/Al₂O₃ displayed a high activity for the complete conversion of CO and CO₂ to methane and C₂₊ hydrocarbons. Moreover, over a discrete and relatively narrow temperature range, the net concentration of light C₂₊ hydrocarbons was elevated, with the exit stream containing a higher concentration of C₂₊ species than was present in the feed stream and the product stream being virtually free of carbon oxides. It is found that the addition of manganese can enhance the selectivity toward the production of light hydrocarbons. A series of Ni–Mn/Al₂O₃ catalysts, prepared with different Ni/Mn ratios, were studied. Various characterization techniques such as X-ray diffraction (XRD) analysis, CO and H₂ chemisorption, in situ nitric oxide adsorption Fourier transform infrared spectroscopy (NO-FTIR), and temperature-programmed reduction (TPR) were performed to gain an insight into how the addition of Mn to the primary catalyst enhances the yield of light hydrocarbons. The origin of Mn promotion was demonstrated through density functional theory (DFT) calculations, which revealed the favorable Mn substitution at the Ni(211) step edge sites under reducing conditions. The affinity of these Mn species toward oxidation stabilizes the CO dissociation product and thus provides a thermodynamic driving force that promotes C–O bond cleavage compared to the Mn-unmodified catalyst surface.]]> Wed 07 Feb 2024 15:34:43 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:45915 Tue 08 Nov 2022 09:32:07 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:24746 PhDPB^Ph)Ni. There are four typical H₂ activation modes for LA-TM bifunctional catalysts: (1) the cis homolytic mode, (2) the trans homolytic mode, (3) the synergetic heterolytic mode, and (4) the dissociative heterolytic mode. The feature of each activation mode has been characterized by key transition state structures and natural bond orbital analysis. Among these four typical modes, (^PhDPB^Ph)Ni catalyst most prefers the synergetic heterolytic mode (ΔG‡ = 29.7 kcal/mol); however the cis homolytic mode cannot be totally disregarded (ΔG‡ = 33.7 kcal/mol). In contrast, the trans homolytic mode and dissociative heterolytic mode are less feasible (ΔG‡ = ∼42 kcal/mol). The general mechanistic picture presented here is fundamentally important for the development and rational design of LA-TM catalysts in the future.]]> Sat 24 Mar 2018 07:11:02 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:40875 µmol/g·h, which is approximately 14 times higher than that of the bare am@TiO₂. Moreover, an apparent quantum yield (AQY) of 18.99% is obtained under LED-405 illumination. This work provides a direction for improving the photocatalytic performance and helps to gain a fundamental understanding of the water oxidation steps.]]> Mon 08 Aug 2022 15:49:38 AEST ]]>