Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Visible Light-Switchable Lattice Oxygen Sites for Selective C-H and C(O)-C Bond Electrooxidation
No full textLattice-oxygen is highly oxidizable, ideal for electrocatalytic C-H oxidation but insufficient alone for C(O)-C bond cleavage due to the non-removable nature of lattice sites. Here, we present a visible light-assisted electrochemical method of in situ formulating removable lattice-oxygen sites in a nickel-oxyhydroxide (ESE-NiOOH) electrocatalyst. This catalyst efficiently converts aromatic alcohols and carbonyls with C(O)-C fragments from lignin and plastics into benzoic acids (BAs) with high yields (83-99 %). Without light irradiation, ESE-NiOOH's intrinsic lattice-oxygen is non-removable and inert for C(O)-C bond cleavage. In situ characterizations show light-induced lattice-oxygen removal and regeneration via OH- refilling. Theoretical calculations identify the nucleophilic oxygen attack on ketone-derived carbanion as a rate-determining step, which can be remarkably facilitated by removable lattice-oxygen to activate alpha-C-H bonds. As a proof-of-concept, an "electrochemical funnel" strategy is developed for high-efficiency upgrading aromatic mixtures with C(O)-C moieties into BA with up to 94 % yield. This in situ removal-regeneration approach for lattice sites opens an avenue for the tailored design of interfacial electrocatalysts to selectively upcycle waste carbon sources into valuable products
Green aromatic aldehyde production from biomass <i>via</i> catalytic fractionation and ozonolysis
No full textHerein, we propose a catalytic fractionation-ozonolysis strategy for producing aromatic aldehydes from biomass. Native lignin is selectively depolymerized into similar to 30 wt% 4-methoxypropenyl-guaiacol/syringol over MoO2 at 160-180 degrees C, followed by ozonolysis yielding 20 wt% vanillin and syringaldehyde. This strategy is free of base and well preserves carbohydrate pulp
Influence of secondary air blade angle and oxygen-rich combustion characteristics of an improved Babcock swirl burner
No full textInnovations in research methods and stable combustion technologies were urgent to enhance flexibility in faulty coal-fired boiler. Focusing boiler start-stop processes was vital for effective peak shaving in power plants. The integration of enriched oxygen stable combustion with swirling techniques showed promise in improving low-load performance. In the cold single-phase experiment, the influence of secondary blade angle on the flow field of an improved Babcock burner was observed. Industrial experiments were conducted on a 700 MW boiler, exclusively implementing the improved burners in the lower layer of the boiler front wall. Stable annular recirculation zones were observed at the burner outlet with blade angles of 30 degrees, 45 degrees, 60 degrees, and 75 degrees for the secondary air. Increasing the blade angle expanded the recirculation zone length and decreased the gas net flow ratio. The angle, between 45 degrees and 60 degrees, facilitated air mixing and protected against outlet slagging and high-temperature corrosion. During cold start-up process of the boiler, supplying 0 kgs(-1) of pure oxygen to a single improved burner increased the flue gas temperature by about 50 degrees C within 0.4 m of the primary air duct outlet. Increasing the oxygen flow rate to 0.2456 kgs(-1) steadily raised the flue gas temperature at 405 MW. The gas temperature in the burner central region was generally lower than the secondary air zone, resulting in a longer ignition distance for the pulverized coal. Higher oxygen levels intensified the heating rate and reduced the ignition distance in the central region
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