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Synthesis of phase pure Co3Mo3N and Fe3Mo3N by temperature programmed ammonolysis has been established by XRD and elemental analysis. The ternary nitrides are characterised by a η-6 structure and low surface area (4–9 m2 g−1). Pseudomorphic transformation of cobalt molybdate prepared using cobalt nitrate generated rod-shaped crystals while the use of iron chloride resulted in Fe3Mo3N aggregates with irregular morphology and wide size distribution. XPS measurements have revealed surface N enrichment relative to the bulk where the passivated samples show a range of oxidation states; Co3Mo3N exhibited Mo2+ and Con+ (0 ≤ n ≤ 3) whereas Fe3Mo3N was characterised by higher oxidation states (Fe3+ and Mo3+). Temperature programmed reduction (TPR) to 823 K served to remove the passivation layer where subsequent H2 chemisorption and temperature programmed desorption (TPD) has demonstrated greater uptake on Fe3Mo3N relative to Co3Mo3N, resulting in a higher nitrobenzene hydrogenation rate (to aniline). Fe3Mo3N promoted selective reduction of –NO2 in p-chloronitrobenzene to generate p-chloroaniline as sole product whereas Co3Mo3N favoured C-Cl scission with the formation of nitrobenzene (in addition to p-chloroaniline). Hydrodechlorination properties were further established for Co3Mo3N in the conversion of chlorobenzene (to benzene) under conditions where Fe3Mo3N was inactive. A temporal deactivation of both nitrides is associated with Cl poisoning of Co3Mo3N and structural changes to Fe3Mo3N.

The gas-phase hydrogenation of benzoic acid was studied over Au supported on CeO 2 and Ce 0.62 Zr 0.38 O 2 (CZ). HAADF-STEM has established formation of nanoscale (mean = 1.5–2 nm) Au particles, which is consistent with CO adsorption measurements. Incorporation of Au facilitated partial support reduction during TPR to 573 K where the presence of Zr increased oxygen mobility, resulting in a greater degree of Ce 4+ reduction (to Ce 3+ ) in Au/CZ, as demonstrated by oxygen storage capacity and XPS measurements. Hydrogenation of an aqueous benzoic acid feed generated benzaldehyde and benzyl alcohol with a higher rate over Au/CZ that is attributed to the action of oxygen vacancies, which activate the carboxyl function for hydrogen attack. A parallel/consecutive kinetic model has been applied to quantify catalytic selectivity. A concerted (single step) conversion is proposed for Au/CeO 2 that involves bridging interaction of the benzoate with Ce cations and Au nanoparticles with hydrogen addition. A stepwise conversion on Au/CZ is achieved via a Mars and van Krevelen mechanism with benzoic acid activation at an oxygen vacancy and reaction with surface hydrogen to generate benzaldehyde as a reactive intermediate that is converted to benzyl alcohol via nucleophilic C O attack. Switching from an aqueous to ethanolic feed increased rate due to greater oxygen vacancy availability with higher selectivity to benzaldehyde and appreciable toluene formation over Au/CZ.

Exclusive hydrogenation of benzaldehyde to benzyl alcohol in gas phase continuous operation (393–413 K, 1 atm) was achieved over Au/Al2O3, Au/TiO2 and Au/ZrO2. Synthesis of Au/Al2O3 by deposition–precipitation generated a narrower distribution (2–8 nm) of smaller (mean = 4.3 nm) Au particles relative to impregnation (1–21 nm, mean = 7.9 nm) with increased H2 uptake under reaction conditions and higher benzaldehyde turnover. Switching reactant carrier from ethanol to water resulted in a significant enhancement of selective hydrogenation rate over Au/Al2O3 with 100% benzyl alcohol yield, attributed to increased available reactive hydrogen. This response extends to reaction over Au/TiO2 and Au/ZrO2.

We report the first continuous (gas phase) hydrogenation of nitrocyclohexane over oxide (Al2O3, TiO2, CeO2 and ZrO2) supported Au catalysts. Thermochemical analysis has established possible thermodynamic constraints and product distribution at equilibrium. The catalysts have been characterised by temperature-programmed reduction (TPR), H2/O2 chemisorption/temperature-programmed desorption (TPD), BET surface area/porosity, X-ray diffraction (XRD) and scanning/transmission electron microscopy (STEM/TEM) measurements. The effects of space velocity (2–6 × 104 h−1), temperature (353 and 473 K) and H2 partial pressure (8 × 10−4–0.93 atm) on catalyst performance have been examined. Selectivity to the target cyclohexanone oxime is sensitive to H2 pressure, where an increase in temperature favours cyclohexanone with amine/ketone condensation and subsequent reduction to dicyclohexylamine. An increase in turnover frequency was observed with decreasing (surface area weighted) mean Au size (from 7.0 to 4.3 nm) but a lower value was obtained for 3.0 nm Au (on CeO2) that is linked to suppressed H2 chemisorption (under reaction conditions) resulting from strong interaction with the partially reduced support. We establish a critical surface interplay between imine, H and –OH that governs selectivity. Au/Al2O3 exhibited the highest activity and oxime selectivity (maximum = 95%), Au/CeO2 promoted near exclusive production of cyclohexanone whereas Au/TiO2 and Au/ZrO2 generated a cyclohexylamine/cyclohexanone mixture.

We provide the first evidence of exclusive benzyl alcohol production in the continuous gas phase hydrogenation of benzaldehyde (T = 393 K; P = 1 atm) over Au/Al2O3, where activity was largely maintained for up to 15 h on-stream. XRD and DRS UV–vis have established the presence of metallic Au post temperature programmed reduction to 473 K, with a surface area weighted mean Au particle size (from TEM analysis) of 7.9 nm. Under the same reaction conditions, Ni/Al2O3 and Pd/Al2O3 were non-selective, generating toluene as the principal product via hydrogenolysis of benzaldehyde and exhibiting an appreciable temporal loss of activity. The results establish Au/Al2O3 as a promising catalyst for the production of benzyl alcohol.

The use of renewable biomass, such as ethylene glycol (EG), for hydrogen production offers a more sustainable system compared to natural gas and petroleum reforming. For the first time, the reaction thermodynamics of steam reforming and sorption enhanced steam reforming of EG have been investigated. Gibbs free energy minimization method was used to study the effect of pressure (1–5 atm), temperature (500–1100 K) and water to EG ratio (WER 0–8) on the production of hydrogen and the formation of associated by-products (CH4, CO2, CO, C). The results suggest that hydrogen production is optimum when steam reforming occurs at atmospheric pressure, 925 K and with a WER of 8. Moreover, working at high temperature (>900 K) and with a WER above 6 inhibits almost entirely the production of methane and carbon. The main source of hydrogen in the system is found to be steam reforming of methane and water gas shift reaction by the analysis of the response reactions (RERs). Hydrogen production is governed by the former reaction at low temperatures while the latter one comes into prominence as temperature increases. By coupling with in situ CO2 capture using CaO, the formation of CO2 and CO can be avoided and high purity of hydrogen (>99%) can be achieved.