Spatial control over features within multifunctional catalysts can unlock efficient one-pot cascade reactions, which are themselves a pathway to aviation biofuels via hydrodeoxygenation. A synthesis strategy that encompasses spatial orthogonality, i.e., one in which different catalytic species are deposited exclusively within discrete locations of a support architecture, is one solution that permits control over potential interactions between different sites and the cascade process. Here, we report a Pd doped hierarchical zeolite, in which Pd nanoparticles are selectively deposited within the mesopores, while acidity is retained solely within the micropores of ZSM-5. This spatial segregation facilitates hydrodeoxygenation while suppressing undesirable decarboxylation and decarbonation, yielding significant enhancements in activity (30.6 vs 3.6 mol_dodecane mol_Pd⁻¹ h⁻¹) and selectivity (C₁₂:C₁₁ 5.2 vs 1.9) relative to a conventionally prepared counterpart (via wet impregnation). Herein, multifunctional material design can realise efficient fatty acid hydrodeoxygenation, thus advancing the field and inspiring future developments in rationalised catalyst design.

Catalytic wastewater treatment has rarely been applied to treat high-ionic-strength wastewater (HISWW) as it contains large amounts of catalyst poisons (e.g., Cl^-). This work investigates the catalytic wet oxidation (CWO) of phenol over a MnCeO _x catalyst in the presence of high NaCl concentrations where the combination of MnCeO _x and NaCl promoted the CWO of phenol. Specifically, in the presence of NaCl at a concentration of 200 g L^-1 and MnCeO _x at a concentration of 1.0 g L^-1, phenol (initially 1.0 g L^-1) and total organic carbon (TOC) conversions were ∼98 and 85%, respectively, after a 24 h reaction. Conversely, under the same reaction conditions without NaCl, the catalytic system only achieved phenol and TOC conversions of ∼41 and 27%, respectively. In situ Attenuated Total Reflection infrared spectroscopy identified the nature of the strongly adsorbed carbon deposits with quinone/acid species found on Ce sites and phenolate species on Mn sites in the single oxides and on MnCeO _x . The presence of high concentrations of NaCl reduced the carbon deposition over the catalyst, promoting surface oxidation of the hydrocarbon and reoxidation of the catalyst, resulting in enhanced mineralization. Moreover, the used MnCeO _x catalyst in the salt water system was efficiently regenerated via a salt water wash under the reaction conditions, showing the great potential of MnCeO _x in practical HISWW treatment.

Water scarcity and the consequent increase of freshwater prices are a cause for concern in regions where shale gas is being extracted via hydraulic fracturing. Wastewater treatment methods aimed at reuse/recycle of fracking wastewater can help reduce water stress of the fracking process. Accordingly, this study assessed the catalytic performance and life cycle environmental impacts of cerium-based mixed oxide catalysts for catalytic wet oxidation (CWO) of organic contaminants, in order to investigate their potential as catalysts for fracking wastewater treatment. For these purposes, MnCeO_x and CuCeO_x were tested for phenol removal in the presence of concentrated NaCl (200 g L^-1), which represented a synthetic fracking wastewater. Removal of phenol in pure ("phenolic") water without NaCl was also considered for comparison. Complete (100 %) phenol and a 94 % total organic carbon (TOC) removal were achieved in both the phenolic and fracking wastewaters by utilising MnCeO_x (5 g L^-1) and insignificant metal leaching was observed. However, a much lower activity was observed when the same amount of CuCeO_x was utilised: 23.3 % and 20.5 % for phenol and TOC removals, respectively, in the phenolic, and 69.1 % and 63 % in the fracking wastewater. Furthermore, severe copper leaching from CuCeO_x was observed during stability tests conducted in the fracking wastewater. A life cycle assessment (LCA) study carried out as part of this work showed that the production of MnCeO_x had 12-98 % lower impacts than CuCeO_x due to the higher impacts of copper than manganese precursors. Furthermore, the environmental impacts of CWO were found to be 94-99 % lower than those of ozonation due to lower energy and material requirements. Overall, the results of this study suggest that the adoption of catalytic treatment would improve both the efficiency and the environmental sustainability of both the fracking wastewater treatment and the fracking process as a whole.