Research efforts to find more sustainable pathways for the synthesis of adipic acid have led to the introduction of new catalytic processes for producing this commodity chemical from alternative resources. With a focus on the performance of oxygen and hydrogen peroxide as preferred oxidants, this minireview summarizes recent advances made in the selective oxidation of cyclohexene, cyclohexane, cyclohexanone and n-hexane to adipic acid. Special attention is paid to the exploration of catalytic pathways involving lignocellulosic biomass-derived chemicals such as 5-hydroxymethylfurfural, D-glucose, γ-valerolactone and compounds representative of lignin and lignin-derived bio-oils.

Emerging catalytic processes for the production of adipic acid

In many scientific communities, the definition of standardized experiments has enabled major progress in process understanding. The investigation of the spray-flame synthesis of nanoparticles at a well-defined standard burner by experiment and simulation makes it possible to produce a comprehensive data set with various established and novel measuring methods. In this work, we introduce the design of the SpraySyn burner as a new standard for a free-jet type burner that offers well-defined and simulation-friendly boundary conditions and geometries as well as accessibility for optical diagnostics. A combustible precursor solution is fed through a centrally located capillary and aerosolized with an oxygen dispersion gas flow. The spray flame is stabilized by a premixed flat methane/oxygen pilot flame fed via a porous bronze matrix surrounded by a stabilizing nitrogen coflow emanating through the same porous matrix, providing easy-to-calculate boundary conditions for simulations. This burner design enables the use of a wide choice of solvents, precursors, and precursor combinations. Best-practice operating instructions and parameters are given, and large-eddy simulations are performed demonstrating the suitability of the SpraySyn burner for computational fluid dynamics simulations. For ensuring reproducible operation across labs, we define a consumer-camera-based flame characterization scheme for the quantitative assessment of the flame geometry such as flame length, diameter, tilt angle, and photometric distribution of visible chemiluminescence along the center axis. These parameters can be used for benchmarking the pilot and spray flame by each user of the SpraySyn burner with the reference flames.

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SpraySyn-A standardized burner configuration for nanoparticle synthesis in spray flames.

A novel, Z-scheme ZnO@AC@FeO photocatalyst, suitable for the intensification of photo-mediated peroxymonosulfate activation: Performance, reactivity and bisphenol A degradation pathways.

Synthesis of Cu Single Atoms Supported on Mesoporous Graphitic Carbon Nitride and Their Application in Liquid-Phase Aerobic Oxidation of Cyclohexene

Lanthanum-Based Perovskites for Catalytic Oxygen Evolution Reaction

Noble-metal-free perovskite oxides are promising and well-known catalysts for high-temperature gas-phase oxidation reactions, but their application in selective oxidation reactions in the liquid phase has rarely been studied. We report the liquid-phase oxidation of cinnamyl alcohol over spray-flame synthesized LaCo1-x Fex O3 perovskite nanoparticles with tert-butyl hydroperoxide (TBHP) as the oxidizing agent under mild reaction conditions. The catalysts were characterized by XRD, BET, EDS and elemental analysis. LaCo0.8 Fe0.2 O3 showed the best catalytic properties indicating a synergistic effect between cobalt and iron. The catalysts were found to be stable against metal leaching as proven by hot filtration, and the observed slight deactivation is presumably due to segregation as determined by EDS. Kinetic studies revealed an apparent activation energy of 63.6 kJ mol-1 . Combining kinetic findings with TBHP decomposition as well as control experiments revealed a complex reaction network.

Towards Mechanistic Understanding of Liquid‐Phase Cinnamyl Alcohol Oxidation with tert‐Butyl Hydroperoxide over Noble‐Metal‐Free LaCo1–xFexO3 Perovskites

Baris Alkan

Papers

Towards Mechanistic Understanding of Liquid‐Phase Cinnamyl Alcohol Oxidation with tert‐Butyl Hydroperoxide over Noble‐Metal‐Free LaCo1–xFexO3 Perovskites

Spray-Flame-Synthesized LaCo1−xFexO3 Perovskite Nanoparticles as Electrocatalysts for Water and Ethanol Oxidation

Enhanced heterogeneous activation of peroxymonosulfate by Ruddlesden-Popper-type La2CoO4+δ nanoparticles for bisphenol A degradation

Selective cyclohexene oxidation with O2, H2O2 and tert-butyl hydroperoxide over spray-flame synthesized LaCo1−xFexO3 nanoparticles

Spray-Flame-Prepared LaCo1–xFexO3 Perovskite Nanoparticles as Active OER Catalysts: Influence of Fe Content and Low-Temperature Heating