The chemical state and acidity of ceria incorporated in hierarchical zeolites have been successfully tuned due to the presence of hierarchical structures of zeolite nanosheets and interaction between ceria and...

The sustainable conversion of biomass-derived compounds into high added-value products is a very important contemporary scientific challenge. In this context, we report here the simultaneous electro-oxidation/-reduction of a biomass-derived compound...

Coumarin is an important chemical in agricultural and pharmaceutical industries. This work studied the synthesis of 7hydroxy-4-methylcoumarin via the Pechmann condensation reaction catalyzed by H-Beta zeolite catalyst using a combination of experimental and theoretical means. Adsorptions and reactions taking place inside the 34T cluster (T = Si or Al atoms) of H-Beta zeolite were examined by using density functional theory with the M06-2X functional. The coumarin synthesis reaction was proposed to be a three-step mechanism: the transesterification, the intramolecular hydroxyalkylation and the dehydration. The total activation energies for each step were calculated to be 17.8, 3.5 and 13.5 kcal⋅mol À 1 , respectively.The zeolite framework stabilized the adsorption complexes and decreased the activation barriers for the Pechmann condensation reaction. The synthesis of 7-hydroxy-4-methylcoumarin from resorcinol and ethyl acetoacetate on H-Beta zeolite was experimentally examined without solvent at various conditions. The adsorption of 7-hydroxy-4-methylcoumarin on H-Beta zeolite was detected by the FT-IR spectroscopy technique. The experimental activation energy of 6.7 kcal⋅mol À 1 agreed very well with the calculated apparent value of 10.6 kcal⋅mol À 1 . The H-Beta zeolite can be reused at least four times with persistently high percent yield.

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Achieving high and stable ethylene yield from (bio)ethanol dehydration over highly active acidic zeolite remains challenging due to undesired side‐reactions. To overcome this issue, the fine‐tuned textural property of the HZSM‐5 catalyst with a hierarchical structure is crucial to overcome diffusion restrictions and limit undesired side‐reactions. Herein, the texture of high acid catalysts obtained via hydrothermal synthesis was simply tuned in the presence of tetrabutylammonium hydroxide as a meso‐ and micropore directing agent and the controlled molar ratio of NaF‐to‐Al2O3. The hierarchically designed HZSM‐5 with the small nanosheet size of 6.5 nm exhibits a high external surface area and mesopores, largely enhancing the catalytic performance of ethanol dehydration up to 95 % ethylene yield as well as preventing the formation of heavy hydrocarbons. To gain insights into the mechanistic points of view, the in situ DRIFTS study revealed that ethylene could form through ethoxy‐mediated mechanism or decomposition of diethyl ether (DEE). The catalyst deactivation caused by polyaromatics obtained from side‐reactions is the reason for low ethanol conversion and high DEE selectivity. Reducing the crystal size of highly acidic zeolite to ultra‐thin nanosheet can shorten the residence time of ethanol, intermediates, and products in porous structures, substantially suppressing the transformation of coke precursors into heavy hydrocarbons to achieve high and stable ethylene yield.