Active species in chloroaluminate ionic liquids catalyzing low-temperature polyolefin deconstruction.

Chloroaluminate ionic liquids selectively transform (waste) polyolefins into gasoline-range alkanes through tandem cracking-alkylation at temperatures below 100 °C. Further improvement of this process necessitates a deep understanding of the nature of the catalytically active species and the correlated performance in the catalyzing critical reactions for the tandem polyolefin deconstruction with isoalkanes at low temperatures. Here, we address this requirement by determining the nuclearity of the chloroaluminate ions and their interactions with reaction intermediates, combining in situ Al magic-angle spinning nuclear magnetic resonance spectroscopy, in situ Raman spectroscopy, Al K-edge X-ray absorption near edge structure spectroscopy, and catalytic activity measurement.

Chloride and Hydride Transfer as Keys to Catalytic Upcycling of Polyethylene into Liquid Alkanes.

Transforming polyolefin waste into liquid alkanes through tandem cracking-alkylation reactions catalyzed by Lewis-acid chlorides offers an efficient route for single-step plastic upcycling. Lewis acids in dichloromethane establish a polar environment that stabilizes carbenium ion intermediates and catalyzes hydride transfer, enabling breaking of polyethylene C-C bonds and forming C-C bonds in alkylation. Here, we show that efficient and selective deconstruction of low-density polyethylene (LDPE) to liquid alkanes is achieved with anhydrous aluminum chloride (AlCl) and gallium chloride (GaCl).

Tuning hydrogenation chemistry of Pd-based heterogeneous catalysts by introducing homogeneous-like ligands.

Noble metals have been extensively employed in a variety of hydrotreating catalyst systems for their featured functionality of hydrogen activation but may also bring side reactions such as undesired deep hydrogenation. It is crucial to develop a viable approach to selectively inhibit side reactions while preserving beneficial functionalities. Herein, we present modifying Pd with alkenyl-type ligands that forms homogeneous-like Pd-alkene metallacycle structure on the heterogeneous Pd catalyst to achieve the selective hydrogenolysis and hydrogenation.

High-Performance CO Capture from Air by Harnessing the Power of CaO- and Superbase-Ionic-Liquid-Engineered Sorbents.

Direct air capture (DAC) of CO by solid porous materials represents an attractive "negative emission" technology. However, state-of-the-art sorbents based on supported amines still suffer from unsolved high energy consumption and stability issues. Herein, taking clues from the CO interaction with superbase-derived ionic liquids (SILs), high-performance and tunable sorbents in DAC of CO was developed by harnessing the power of CaO- and SIL-engineered sorbents.

Harnessing the Hybridization of a Metal-Organic Framework and Superbase-Derived Ionic Liquid for High-Performance Direct Air Capture of CO.

Direct air capture (DAC) of CO has emerged as the most promising "negative carbon emission" technologies. Despite being state-of-the-art, sorbents deploying alkali hydroxides/amine solutions or amine-modified materials still suffer from unsolved high energy consumption and stability issues. In this work, composite sorbents are crafted by hybridizing a robust metal-organic framework (Ni-MOF) with superbase-derived ionic liquid (SIL), possessing well maintained crystallinity and chemical structures.

Low-temperature upcycling of polyolefins into liquid alkanes via tandem cracking-alkylation.

Selective upcycling of polyolefin waste has been hampered by the relatively high temperatures that are required to cleave the carbon-carbon (C-C) bonds at reasonably high rates. We present a distinctive approach that uses a highly ionic reaction environment to increase the polymer reactivity and lower the energy of ionic transition states. Combining endothermic cleavage of the polymer C-C bonds with exothermic alkylation reactions of the cracking products enables full conversion of polyethylene and polypropylene to liquid isoalkanes (C to C) at temperatures below 100°C.

Elucidating the Cooperative Roles of Water and Lewis Acid-Base Pairs in Cascade C-C Coupling and Self-Deoxygenation Reactions.

Water plays pivotal roles in tailoring reaction pathways in many important reactions, including cascade C-C bond formation and oxygen elimination. Herein, a kinetic study combined with complementary analyses (DRIFTS, isotopic study, H solid-state magic angle spinning nuclear magnetic resonance) and density functional theory (DFT) calculations are performed to elucidate the roles of water in cascade acetone-to-isobutene reactions on a Zn Zr O mixed metal oxide with balanced Lewis acid-base pairs. Our results reveal that the reaction follows the acetone-diacetone alcohol-isobutene pathway.

Al Pulsed Field Gradient, Diffusion-NMR Spectroscopy of Solvation Dynamics and Ion Pairing in Alkaline Aluminate Solutions.

Pulsed field gradient nuclear magnetic resonance (PFG-NMR) measurements were successfully applied to the Al ( I = 5/2) nucleus in concentrated electrolytes to investigate the diffusion of aluminate ions [Al(OH)] in simulant high-level nuclear waste (3 M NaOH) between 25 and 85 °C. The temperature-dependent diffusion coefficients obtained from H, Na, and Al PFG-NMR were well fit by a Vogel-Fulcher-Tammann model and a power law equation. Comparison of Al diffusion coefficients of 0.

In Situ Al NMR Spectroscopy of Aluminate in Sodium Hydroxide Solutions above and below Saturation with Respect to Gibbsite.

Aluminum hydroxide (Al(OH), gibbsite) dissolution and precipitation processes in alkaline environments play a commanding role in aluminum refining and nuclear waste processing, yet mechanistic aspects underlying sluggish kinetics during crystallization have remained obscured due to a lack of in situ probes capable of isolating incipient ion pairs. At a molecular level Al is cycling between tetrahedral ( T ) coordination in solution to octahedral ( O ) in the solid. We explored dissolution of Al(OH) that was used to produce variably saturated aluminate (Al(OH))-containing solutions under alkaline conditions (pH >13) with in situ Al magic angle spinning (MAS)-nuclear magnetic resonance (NMR) spectroscopy, and interrogated the results with ab initio molecular dynamics (AIMD) simulations complemented with chemical shift calculations.

A fundamental study on the [(μ-Cl)3Mg2(THF)6]+ dimer electrolytes for rechargeable Mg batteries.

The long sought solvated [MgCl](+) species in the Mg-dimer electrolytes was characterized by soft mass spectrometry. The presented study provides an insightful understanding on the electrolyte chemistry of rechargeable Mg batteries.

Energetics of defects on graphene through fluorination.

Functionalized graphene sheets (FGSs) comprise a unique member of the carbon family, demonstrating excellent electrical conductivity and mechanical strength. However, the detailed chemical composition of this material is still unclear. Herein, we take advantage of the fluorination process to semiquantitatively probe the defects and functional groups on graphene surface.

Structure and stability of hexa-aqua V(III) cations in vanadium redox flow battery electrolytes.

The vanadium(III) cation structure in mixed acid based electrolyte solution from vanadium redox flow batteries is studied by (17)O and (35/37)Cl nuclear magnetic resonance (NMR) spectroscopy, electronic spectroscopy and density functional theory (DFT) based computational modelling. Both computational and experimental results reveal that the V(III) species can complex with counter anions (sulfate/chlorine) depending on the composition of its solvation sphere. By analyzing the powder precipitate it was found that the formation of sulfate complexed V(III) species is the crucial process in the precipitation reaction.

In situ molecular spectroscopic evidence for CO2 intercalation into montmorillonite in supercritical carbon dioxide.

The interaction of anhydrous supercritical CO(2) (scCO(2)) with both kaolinite and ~1W (i.e., close to but less than one layer of hydration) calcium-saturated montmorillonite was investigated under conditions relevant to geologic carbon sequestration (50 °C and 90 bar).

Investigation of local environments in Nafion-SiO(2) composite membranes used in vanadium redox flow batteries.

Proton conducting polymer composite membranes are of technological interest in many energy devices such as fuel cells and redox flow batteries. In particular, polymer composite membranes, such as SiO(2) incorporated Nafion membranes, are recently reported as highly promising for the use in redox flow batteries. However, there is conflicting reports regarding the performance of this type of Nafion-SiO(2) composite membrane in the redox flow cell.

Chloride supporting electrolytes for all-vanadium redox flow batteries.

This paper examines vanadium chloride solutions as electrolytes for an all-vanadium redox flow battery. The chloride solutions were capable of dissolving more than 2.3 M vanadium at varied valence states and remained stable at 0-50 °C.

Coordinatively unsaturated Al3+ centers as binding sites for active catalyst phases of platinum on gamma-Al2O3.

In many heterogeneous catalysts, the interaction of metal particles with their oxide support can alter the electronic properties of the metal and can play a critical role in determining particle morphology and maintaining dispersion. We used a combination of ultrahigh magnetic field, solid-state magic-angle spinning nuclear magnetic resonance spectroscopy, and high-angle annular dark-field scanning transmission electron microscopy coupled with density functional theory calculations to reveal the nature of anchoring sites of a catalytically active phase of platinum on the surface of a gamma-Al2O3 catalyst support material. The results obtained show that coordinatively unsaturated pentacoordinate Al3+ (Al3+penta) centers present on the (100) facets of the gamma-Al2O3 surface are anchoring Pt.

Characterization of dispersed heteropoly Acid on mesoporous zeolite using solid-state 31P NMR spin-lattice relaxation.

Dispersion and quantitative characterization of supported catalysts is a grand challenge in catalytic science. In this paper, heteropoly acid H(3)PW(12)O(40) (HPA) is dispersed on mesoporous zeolite silicalite-1 derived from hydrothermal synthesis using carbon black nanoparticle templates, and the catalytic activity is studied for 1-butene isomerization. The HPAs supported on conventional zeolite and on mesoporous zeolite exhibit very different activities and thus provide good model systems to investigate the structure dependence of the catalytic properties.