Microstructural and Dynamical Heterogeneities in Ionic Liquids

Ionic liquids (ILs) are a special category of molten salts solely composed of ions with varied molecular symmetry and charge delocalization. The versatility in combining varied cation-anion moieties and in functionalizing ions with different atoms and molecular groups contributes to their peculiar interactions ranging from weak isotropic associations to strong, specific, and anisotropic forces. A delicate interplay among intra- and intermolecular interactions facilitates the formation of heterogeneous microstructures and liquid morphologies, which further contributes to their striking dynamical properties. Microstructural and dynamical heterogeneities of ILs lead to their multifaceted properties described by an inherent designer feature, which makes ILs important candidates for novel solvents, electrolytes, and functional materials in academia and industrial applications. Due to a massive number of combinations of ion pairs with ion species having distinct molecular structures and IL mixtures containing varied molecular solvents, a comprehensive understanding of their hierarchical structural and dynamical quantities is of great significance for a rational selection of ILs with appropriate properties and thereafter advancing their macroscopic functionalities in applications. In this review, we comprehensively trace recent advances in understanding delicate interplay of strong and weak interactions that underpin their complex phase behaviors with a particular emphasis on understanding heterogeneous microstructures and dynamics of ILs in bulk liquids, in mixtures with cosolvents, and in interfacial regions.

Ni-Based Nanoparticles on Mesoporous Silica Supports for Single-Stage Arsenic and Chlorine Removal during Diesel Fraction Hydrotreating

As- and Cl-containing impurities are highly detrimental to sulfided catalysts in hydrotreating processes. To prevent the irreversible loss of activity of the main sulfide catalysts by As and Cl contaminants, a protective double-layered guard bed catalyst is applied. Two types of mesoporous silica supports (SBA-15 and MCF) were used to obtain sorption-catalytic materials. The high specific surface area of the supports allowed for a significant increase in access to the active catalyst centers. The NiMo/SBA-15/Al₂O₃ and NiMg/MCF/Al₂O₃ sorption-catalytic materials demonstrated high activity and stability over 48 h for the simultaneous removal of As and Cl. The catalytic materials allowed for reducing the concentrations of As and Cl to less than 0.1 ppm in the diesel fraction under the following conditions: 5.0 MPa pressure, 2.0 h^-1 LHSV, 300 L/L H₂-to-substrate volume ratio, and 360 °C.

Hf(OTf)4 as a Highly Potent Catalyst for the Synthesis of Mannich Bases under Solvent-Free Conditions

Hf(OTf)4 was identified as a highly potent catalyst (0.1-0.5 mol%) for three-component Mannich reaction under solvent-free conditions. Hf(OTf)4-catalyzed Mannich reaction exhibited excellent regioselectivity and diastereoselectivity when alkyl ketones were employed as substrates. 1H NMR tracing of the H/D exchange reaction of ketones in MeOH-d4 indicated that Hf(OTf)4 could significantly promote the keto-enol tautomerization, thereby contributing to the acceleration of reaction rate.

Tunable Aryl Imidazolium Recyclable Ionic Liquid with Dual Brønsted-Lewis Acid as Green Catalyst for Friedel-Crafts Acylation and Thioesterification

Unique tunable aryl imidazolium ionic liquids successfully catalyzed Friedel-Crafts acylation and thioesterification in sealed tubes. These reactions can form a C-C bond and a C-S bond with high atom economy. Ionic liquids exhibited high activity and catalyzed essential reactions with good to excellent yields while retaining their catalytic activities for recycling.

Brønsted acidic ionic liquid-promoted direct C3-acylation of N-unsubstituted indoles with acid anhydrides under microwave irradiation

A green and efficient method for the synthesis of 3-acylindoles using a Brønsted acidic ionic liquid under microwave irradiation has been developed.