Therefore, in this review article, we have conducted a comprehensive and critical discussion on how steric hindrance and electronic coupling at metal-acid interfaces affect catalytic activation of internal À OH group in glycerol molecule. Selected highlights on the mechanistic investigation for ex-situ and insitu formed Brønsted acidity over Pt-WO x and IrÀ ReO x catalysts, have been discussed with experimental and computational details. The outcome of this review will provide important insights on controllable manipulation of spatial and electronic structures for selective hydrogenation reactions with broader industrial applications.[a] D.

The mesopores formation in zeolite crystals has long been considered to occur through the stochastic hydrolysis and removal of framework atoms. Here, we investigate the NH 4 F etching of representative small, medium, and large pore zeolites and show that the zeolite dissolution behavior, therefore the mesopore formation probability, is dominated by zeolite architecture at both nano-and subnano scales. At the nano-scale, the hidden mosaics of zeolite structure predetermine the spatio-temporal dissolution of the framework, hence the size, shape, location, and orientation of the mesopores. At the sub-nano scale, the intrinsic micropore size and connectivity jointly determine the diffusivity of reactant and dissolved products. As a result, the dissolution propensity varies from removing small framework fragments to consuming nanodomains and up to full digestion of the outmost part of zeolite crystals. The new knowledge will lead to new understanding of zeolite dissolution behavior and new adapted strategies for tailoring hierarchical zeolites.

With increasing interest in developing biodegradable polymers to replace fossil-based products globally, lactic acid (LA) has been paid extensive attention due to the high environment-compatibility of its downstream products. The mainstream efforts have been put in developing energy-efficient conversion technologies through biological and chemical routes to synthesize LA. However, to our best knowledge, there is a lack of sufficient attention in developing effective separation technologies with high atom economics for purifying LA and derivatives. In this review, the most recent advances in purifying LA using precipitation, reactive extraction, emulsion liquid membrane, reactive distillation, molecular distillation, and membrane techniques will be discussed critically with respect to the fundamentals, flow scheme, energy efficiency, and equipment. The outcome of this article is to offer insights into implementing more atomic and energy-efficient technologies for upgrading LA.

No abstract

Aqueous oxidation of bio-derived ethylene glycol to glycolic acid represents a sustainable route to polyglycolic acid. However, a strong acidic/basic oxidative medium often causes structural evolution and metal sintering of supported metal catalysts. We reported an unusual self-activation of Pt/NaY catalysts for enhanced oxidation of ethylene glycol in a base-free medium. Owing to a dealuminization-induced shortened Si−OH bond and formulation of a Pt−acid interface caused by glycolic acid, the activity of self-activated Pt/NaY catalysts displays a 2-fold enhancement compared with fresh ones. As the key finding in this work, dealuminization is found to cause an electronic coupling effect through shortened Si−OH bonds and formulating the (Si−OH)−Pt interface. Such a coupling effect leads to electron-rich nature of Pt sites for oxidation reactions, and thus, the self-activated Pt/NaY catalysts display leading performances in terms of activity and durability as seen in literature reports. Various characterization techniques, including transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, provide consistent and supporting evidence for such unique interfacial behaviors. Catalyst characterization further reveals that metallic Pt 0 species is the intrinsically active phase for σ-activation rather than π-activation of ethylene glycol molecules. Isotopic tests and kinetic modeling further confirm the reaction mechanism on the surface of fresh and spent Pt/NaY catalyst samples. The special activity enhancement of spent catalysts can be applied to investigate the plausible mechanism of various other oxidation reactions.