The selective oxidation of methane to methanol, using H2O2, under mild reaction conditions was studied using bimetallic 1 wt. % AuPd/TiO2 prepared by stabiliser-free sol-immobilisation.The as-prepared catalysts exhibited low, unselective oxidation activity and deleterious H2O2 decomposition, which was ascribed to the small mean particle size of the supported AuPd nanoparticles. Heat treatments were employed to facilitate particle size growth, yielding an improvement in the catalyst turn-over-frequency and decreasing the H2O2 decomposition rate. The effect of support phase was studied by preparing a range of AuPd catalysts supported on rutile TiO2. The low surface area rutile TiO2 yielded catalysts with effective oxygenate production, but poor H2O2 utilisation. The influence of the rutile-TiO2 support was investigated further by producing catalysts with a lower metal loading to maintain a consistent metal loading per m 2 to the 1 wt.% AuPd/ P25 TiO2 catalyst. When calcined at 800 °C the 0.13 wt.% AuPd catalyst demonstrated significantly improved turn-over frequency of 103 h -1 . In contrast, the turn-over frequency was found to be ca. 2 h -1 for the rutile-supported 1 wt. % AuPd catalyst calcined at 800 °C. The catalysts were probed by electron microscopy and XPS to understand the influence of particle size and oxidation state on the utilisation of H2O2 and oxygenate productivity. This work shows that the key to highly active catalysts involves the prevention of deleterious H2O2 decomposition and this can be achieved through carefully controlling the nanoparticle size, metal loading and metal oxidation state.

Methane oxidation using N2O was carried out with Fe-MFI zeolite catalysts at 300 °C. Methane conversion over Fe-ZSM-5, Fe-silicalite-1 and Fe-TS-1 indicates that Brønsted acidity is required to support the Fe-based alpha-oxygen active site for the important initial hydrogen abstraction step. Increasing the calcination temperature of Fe-ZSM-5 from 550 to 950 °C showed that the catalyst retained the MFI structure. However, at 950 °C the Brønsted and Lewis acid sites were altered significantly due to the migration of aluminium, which led to a significant decrease in catalytic performance. Over Fe-ZSM-5 the desired partial oxidation product, methanol was observed to undergo a reaction path similar to the methanol to olefin (MTO) process, which predominately produced ethene and subsequently produced coke.Methanol control experiments over Fe-silicalite-1, Fe-ZSM-5, Fe-TS-1 and H-ZSM-5 indicated that with the presence of Brønsted acidity the catalyst were more effective at forming ethene and subsequent aromatic species from DME, which resulted in an increased level of catalyst fouling. The implication of these observations are that the desorption of methanol is crucial to afford high mass balances and selectivity, however, Brønsted acid sites appear to slow this rate. These sites appear to effectively retain methanol and DME under reaction conditions, leading to low mass balances being observed. Our results confirm that to afford efficient and continuous methane oxidation by N2O, the catalytic active site must be extra-framework Fe coordinated to Al.

Catalytic methane oxidation using N O was investigated at 300 °C over Fe-ZSM-5. This reaction rapidly produces coke (retained organic species), and causes catalyst fouling. The introduction of water into the feed-stream resulted in a significant decrease in the coke selectivity and an increase in the selectivity to the desired product, methanol, from ca. 1 % up to 16 %. A detailed investigation was carried out to determine the fundamental effect of water on the reaction pathway and catalyst stability. The delplot technique was utilised to identify primary and secondary reaction products. This kinetic study suggests that observed gas phase products (CO, CO , CH OH, C H and C H ) form as primary products whilst coke is a secondary product. Dimethyl ether was not detected, however we consider that the formation of C products are likely to be due to an initial condensation of methanol within the pores of the zeolite and hence considered pseudo-primary products. According to a second order delplot analysis, coke is considered a secondary product and its formation correlates with CH OH formation. Control experiments in the absence of methane revealed that the rate of N O decomposition is similar to that of the full reaction mixture, indicating that the loss of active alpha-oxygen sites is the likely cause of the decrease in activity observed and water does not inhibit this process.

Ce 0.5 M 0.5 O 2 (M = Ti, Zr, Hf) nanoparticles have been successfully synthesized by microwave irradiation in the ionic liquid [C 4 mim][Tf 2 N] (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide). The morphology, crystallinity, and chemical composition of the obtained materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and N 2 -adsorption measurements. XRD and Raman spectroscopy analyses confirmed the formation of solid solutions with cubic fluorite structure. The catalytic activities of the Ce 0.5 M 0.5 O 2 (M = Ti, Zr, Hf) nanoparticles were investigated in the low-temperature oxidation of CO. Ce 0.5 Zr 0.5 O 2 nanospheres exhibit the best performance (100% conversion at 350 1C), followed by Ce 0.5 Hf 0.5 O 2 (55% conversion at 360 1C) and Ce 0.5 Ti 0.5 O 2 (11% conversion at 350 1C). Heating the as-prepared Ce 0.5 Zr 0.5 O 2 to 600 1C for extended time leads to a decrease in surface area and, as expected decreased catalytic activity. Depending on the ionic liquid the obtained Ce 0.5 Zr 0.5 O 2 exhibits different morphologies, varying from nano-spheres in [C 4 mim][Tf 2 N] and [P 66614 ][Tf 2 N] (P 66614 = trishexyltetradecylphosphonium) to sheet-like assemblies in [C 3 mimOH][Tf 2 N] (C 3 mimOH = 1-(3-hydroxypropyl)-3methylimidazolium). The microwave synthesis superiority to other heating methods like sonochemical synthesis and conventional heating was proven by comparative experiments where the catalytic activity of Ce 0.5 Zr 0.5 O 2 obtained by alternate methods such as conventional heating was found to be poorer than that of the microwave-synthesised material.