Oil foams stabilized by POSS/organosilica particle assemblies: application for aerobic oxidation of aromatic alcohols

A novel amphiphilic polyhedral oligomeric silsesquioxane (POSS) with surfactant-like behavior was synthesized. By combining this new POSS, used as a frother, with surface-active catalytic organosilica particles, used as a stabilizer, we designed a dual particle system able to generate foams in pure organic solvents. Tunable foamability and foam stability were achieved in a variety of organic solvents by simply adjusting the POSS concentration. As a result, the catalytic activity was drastically boosted in the aerobic oxidation of pure aromatic alcohols under 1 bar O2 pressure. Particles were conveniently recycled with high foamability and the catalytic efficiency was maintained for at least 7 consecutive runs

Ethanol foams stabilized by isobutyl-based POSS–organosilica dual-particle assemblies

Nonaqueous foams in low-surface tension solvents (<25 mN·m–1) are highly desired for applications in fire extinguishers and detoxification gels. However, their formation is a Holy Grail of the chemical industry due to the need for stabilizers with low surface energy and high recyclability. Herein, we disclose a new strategy to generate abundant foams in ethanol and a variety of low-surface tension solvents relying on the interfacial coadsorption of two different particles. The particles consist of surface-active fluorinated silica particles, used as a stabilizer, and a novel amphiphilic polyhedral oligomeric silsesquioxane (POSS) decorated with isobutyl cage substituents, used as a frother. The interaction between POSS and fluorinated particles at the ethanol–air interface was thoroughly investigated by combining physicochemical methods (contact angle, dynamic surface tension, and dynamic light scattering methods) and catalytic tests using the model aerobic oxidation reaction of benzyl alcohol. Both particles could be conveniently recycled for at least 5 consecutive runs with high foamability and catalytic activity

Microfluidic device for monitoring catalytic events on armored bubbles

Abstract: A polydimethylsiloxane‐based microfluidic device allows monitoring local oxidation events in organic solvents at the level of an individual air bubble armored with surface‐active low‐surface energy catalytic particles. This new technique permits tunable design of microreactors for gas‐liquid‐solid reactions

Influence of Pore Size in Benzoin Condensation of Furfural Using Heterogenized Benzimidazole Organocatalysts

A designed N-heterocyclic carbene (NHC) catalyst was covalently anchored on a range of mesoporous and hierarchical supports, to study the influence of pore size in the benzoin condensation of furfural. The structural and spectroscopic characteristics of the anchored catalysts were investigated, also with the help of molecular dynamics simulations, in order to rationalize the degree of stability and recyclability of the heterogenized organocatalysts. Quantitative yields (99 %) and complete recyclability were maintained after several cycles, vindicating the design rationale

Liquid-phase permethylation of diethylenetriamine using methanol over robust composite copper catalysts

Pentamethyldiethylenetriamine is a permethylated polyamine that is widely used to prepare foam polyurethane. The current technology for its synthesis relies on diethylenetriamine methylation with formaldehyde under H2. This route is selective, but the use of formaldehyde raises safety and environmental concerns. Herein we present an alternative non-toxic route using methanol as greener and cheaper methylating reagent. The reaction proceeds fast and selectively over composite copper catalysts with a pentamethyldiethylenetriamine yield of 75% and resistance to sintering

Synthesis of amine derivatives from furoin and furil over Ru/Al2O3 catalyst

The direct/reductive amination of carbohydrate-based furoin and furil with NH3/H2 was investigated to access amine derivatives. In the sole presence of NH3, cyclic amines, i.e. 2,3,5,6-tetra(furan-2-yl)pyrazine and 2,2’-bipyridine-3,3’-diol, were generated as main products from furoin and furil, respectively. Over Ru/Al2O3 under NH3/H2, 2-amino-1,2-di(furan-2-yl)ethan-1-ol (i.e. alcohol-amine) was generated as main product with 47% yield at 140 °C for 2 h starting from furoin. The catalyst could be recycled for at least three consecutive runs. An alcohol-imine was the main intermediate that undewent tautomerization to alcohol-enamine/keto-amine leading to cyclic by-products by self-condensation. Supported by DFT calculations, the reactivity of the alcohol-imine intermediate was rationalized by its preferential adsorption on Ru centers via the NH group with the OH group pointing away from the surface, resulting in the formation of alcohol-amine as main product. By combining Ru/Al2O3 and a silica-anchored N-heterocyclic carbene (NHC) catalyst, 2-amino-1,2-di(furan-2-yl)ethan-1-ol could be accessed with 42% overall yield in a single reactor

First‐principles microkinetic study of the catalytic hydrodeoxygenation of guaiacol on transition metal surfaces

The mechanism behind the hydrodeoxygenation (HDO) of guaiacol on Co(0001), Ni(111), Cu(111), Pd(111), and Pt(111) was investigated by constructing a first‐principles microkinetic model from density functional theory (DFT) models for 68 possible intermediates over each surface. We report that the most energetically favorable pathway for this process is the demethylation of guaiacol to catechol over Ni(111), which exhibits highly desirable deoxygenation and hydrogenation kinetics at industrial temperatures. Guaiacol readily undergoes hydrogenation over Pt(111) and Pd(111), but the products exhibit slow desorption from the surfaces at standard operation temperatures. Furthermore, the deoxygenation pathway is hindered by the high energy barrier associated with the scission of the Calkyl−O bond

Cyclic glyceryl sulfate: a simple and versatile bio-based synthon for the facile and convergent synthesis of novel surface-active agents

In the frame of biomass valorization, a novel and simple cyclic glyceryl sulfate was efficiently prepared in two steps from glycerol. It was shown to react efficiently with primary, secondary as well as tertiary amines to afford either the corresponding anionic or zwitterionic surface-active agents

Foams stabilized by Aquivion TM PFSA: Application to interfacial catalysis for cascade reactions

Foams are attractive platforms for engineering gas–liquid–solid catalytic microreactors with enhanced triphasic contact. In this study, the foaming properties of surface‐active AquivionTM perfluorosulfonic acid resin (AquivionTM PFSA) are unraveled. Stable aqueous and non‐aqueous foams are prepared driven by hydrogen bond interactions between AquivionTM PFSA and protic solvents (e.g., benzyl alcohol, aniline, water). In light of these unique properties, a catalytic foam system for one‐pot cascade deacetalization–hydrogenation reactions is designed. As proof of concept, benzaldehyde dimethyl acetal is converted into benzyl alcohol with 84% overall yield at room temperature in a foam system in the presence of AquivionTM PFSA and Pd/SiO2 catalysts, whereas the yield is halved in a non‐foam system. The enhanced reaction efficiency is attributed to a marked increase in interfacial area of the foam system and preferential location of catalytic acid centers at the gas–liquid interface

Metal‐free selective synthesis of α,β‐unsaturated aldehydes from alkenes and formaldehyde catalyzed by dimethylamine

α,β‐Unsaturated aldehydes are important building blocks for the synthesis of a wide range of chemicals, including polymers. The synthesis of these molecules from cheap feedstocks such as alkenes remains a scientific challenge, mainly due to the low reactivity of alkenes. Here we report a selective and metal‐free access to α,β‐unsaturated aldehydes from alkenes with formaldehyde. This reaction is catalyzed by dimethylamine and affords α,β‐unsaturated aldehydes in yields of up to 80 %. By combining Density Functional Theory (DFT) calculations and experiments, we elucidate the reaction mechanism which is based on a cascade of hydride transfer, hydrolysis and aldolization reactions. The reaction can be performed under very mild conditions (30–50 °C), in a theoretically 100 % carbon‐economical fashion, with water as the only by‐product. The reaction was successfully applied to non‐activated linear 1‐alkenes, thus opening an access to industrially relevant α,β‐unsaturated aldehydes from cheap and widely abundant chemicals at large scale