7 research outputs found
SEPARATE STORAGE OF PROTON–ELECTRON PAIRS AT BARIUM OXIDE–RUTHENIUM INTERFACES FOR ENHANCING AMMONIA SYNTHESIS UNDER MILD CONDITIONS
No full textUnderstanding Coke Formation Mechanism in MFI Zeolites during Methanol-to-Hydrocarbons Conversion
No full textEffects of Framework Structures of Zeolite-Templated Carbons on Their Thermal Structural Transformations
No full textZeolite-templated carbons (ZTCs) are ordered microporous carbons synthesized by replicating the microporous structure of zeolites with carbon. Due to carbon growth within the confined spaces of zeolite micropores, ZTCs are composed of interconnected, buckybowl-like carbon moieties with abundant edge sites terminated by hydrogen (H) atoms. The amount of H-terminated edge sites and the local framework structure of ZTCs depend on their synthesis conditions. In this study, we investigated the effects of the initial framework structures of ZTCs on their thermal structural transformations. Our results demonstrate that ZTC frameworks primarily built with nanoribbon-like carbon moieties containing abundant H-terminated edge sites undergo significant dehydrogenation (removal of H2) and concomitant formation of new C-C bonds upon thermal treatment, leading to increased carbon surface curvature, reduced micropore diameter and volume, and enhanced ultramicroporosity. These structural changes also lead to substantial modifications in macroscopic properties, such as oxidative stability, work function, and ppb-level chloroform adsorption capability in water. The findings highlight the unique potential of synthesizing microporous carbons with tailored structures and physicochemical properties through post-synthesis thermal transformation of ZTCs.
Hydrophobic zeolites as efficient adsorbents for removing chloroform in drinking water
No full textChloroform is one of the most prevalent disinfection byproducts found in drinking water, posing significant risks to human health and aquatic ecosystems due to its carcinogenic properties. Since chloroform is present at very low concentrations (tens to hundreds of ppb), it is crucial to develop effective adsorbents capable of strong interactions with chloroform even in a water-dominant environment. In this study, we investigated the effects of different chemical compositions (Si/Al ratios), silanol defects, and pore topologies (CHA, MFI, and BEA) of zeolites on their chloroform adsorption behavior. The results showed that zeolites with higher Si/Al ratios and fewer silanol defects exhibit greater surface hydrophobicity, leading to effective chloroform uptake properties in aqueous solutions. Adsorption experiments using hydrophobic pure-silica zeolites with different pore topologies revealed that a micropore aperture size of >= 10-membered rings (MFI and BEA) is required for efficient chloroform adsorption, as small-pore zeolites with 8-membered ring apertures (CHA) impose significant diffusion limitations for chloroform. The hydrophobic zeolites demonstrated excellent reusability compared to conventionally used activated carbon and also showed good adsorption performance for other trihalomethanes. These findings highlight the potential of hydrophobic zeolites as efficient adsorbents for removing extremely low concentrations of toxic trihalomethanes from drinking water.
Artificial Neural Network enabling Clinically Meaningful Biological Image Data Generation
No full textHierarchical LTL Zeolite as an Efficient and Sustainable Solid Acid Catalyst for Replacing HCl in the Production of Polyurethane Intermediates
No full textIn many industrially important reactions, caustic mineral acid catalysts have been successfully replaced with green solid acids such as zeolites. In this context, extensive efforts have been devoted to replacing HCl to produce methylenedianiline (MDA), a key intermediate in polyurethane production. Unfortunately, limited success has been achieved thus far due to low activity, selectivity towards the desired 4,4′-MDA, and rapid catalyst deactivation. Here we report that meso-/microporous hierarchical LTL zeolite exhibits unprecedentedly high activity, selectivity, and stability. The one-dimensional cage-like micropores of LTL promote the bimolecular reaction between two para-aminobenzylaniline intermediates to selectively produce 4,4′-MDA and inhibit the formation of undesired isomers and heavy oligomers. Meanwhile, the secondary mesopores alleviate mass transfer limitations, resulting in a 7.8-fold higher MDA formation rate compared to solely microporous LTL zeolite. Due to suppressed oligomer formation and fast mass transfer, the catalyst exhibits inappreciable deactivation in an industrially relevant continuous flow reactor. © 2023 Wiley-VCH GmbH.11Nsciescopu
Splitting of Hydrogen Atoms into Proton–Electron Pairs at BaO–Ru Interfaces for Promoting Ammonia Synthesis under Mild Conditions
No full textRu catalysts promoted with alkali and alkaline earth
have shown
superior ammonia (NH3) synthesis activities under mild
conditions. Although these promoters play a vital role in enhancing
catalytic activity, their function has not been clearly understood.
Here, we synthesize a series of Ba-Ru/MgO catalysts with an optimal
Ru particle size (∼2.3 nm) and tailored BaO–Ru interfacial
structures. We discover that the promoting effect is created through
the separate storage of H+/e– pairs at
the BaO–Ru interface. Chemisorbed H atoms on Ru dissociate
into H+/e– pairs at the BaO–Ru
interface, where strongly basic, nonreducible BaO selectively captures
H+ while leaving e– on Ru. The resulting
electron accumulation in Ru facilitates N2 activation via
enhanced π-backdonation and inhibits hydrogen poisoning during
NH3 synthesis. Consequently, the formation of intimate
BaO–Ru interface without an excessive loss of accessible Ru
sites enables the synthesis of highly active catalysts for NH3 synthesis
