Aquivion-Based Spray Freeze-Dried Composite Materials for the Cascade Production of γ-Valerolactone.

The development of multifunctional catalysts is a necessary step to effectively carry out one-pot cascade reactions, such as that from furfural to γ-valerolactone. This research effort faces the challenge posed by the intrinsic limit of how many kinds of catalytic sites a single material can bear. In this work, the application of Spray-Freeze Drying (SFD) as a synthetic technique for the preparation of a wide range of innovative composite multi-functional catalysts is reported. Herein we show that by the proper combination of Aquivion as a highly active Brønsted acid catalyst and metal oxides as both support materials and Lewis acids (LAS) enable to achieve highly unique efficient and effective dual acid composite catalysts that are able to carry out the cascade reaction from furfural to γ-valerolactone. The dual catalytic system comprised of Aq/ZrO2 with 30 % polymer content prepared via spray-freeze drying exhibited GVL yields of 25 % after only 2 h at 180 °C and a remarkably high productivity of 4470 µmolGVL gCat -1 h-1, one of the highest reported results. Mechanistic studies based on experimental and advanced characterisation and spectroscopic techniques, such as, SEM, TEM, 15N MAS NMR and 19F MAS NMR indicate that activity arises from the proper tuning of BAS/LAS (Brønsted Acid Site/Lewis Acid Site) acidic properties.

Ce-radical Scavenger-Based Perfluorosulfonic Acid Aquivion® Membrane for Pressurised PEM Electrolysers.

A Ce-radical scavenger-based perfluorosulfonic acid (PFSA) Aquivion® membrane (C98 05S-RSP) was developed and assessed for polymer electrolyte membrane (PEM) electrolyser applications. The membrane, produced by Solvay Specialty Polymers, had an equivalent weight (EW) of 980 g/eq and a thickness of 50 µm to reduce ohmic losses at a high current density. The electrochemical properties and gas crossover through the membrane were evaluated upon the formation of a membrane-electrode assembly (MEA) in a range of temperatures between 30 and 90 °C and at various differential pressures (ambient, 10 and 20 bars). Bare extruded (E98 05S) and reinforced (R98 05S) PFSA Aquivion® membranes with similar EWs and thicknesses were assessed for comparison in terms of their performance, stability and hydrogen crossover under the same operating conditions. The method used for the membrane manufacturing significantly influenced the interfacial properties, with the electrodes affecting the polarisation resistance and H2 permeation in the oxygen stream, as well as the degradation rate, as observed in the durability studies.

Influence of Ionomer Content in the Catalytic Layer of MEAs Based on Aquivion® Ionomer.

Perfluorinated sulfonic acid (PFSA) polymers such as Nafion® are widely used for both electrolyte membranes and ionomers in the catalytic layer of membrane-electrode assemblies (MEAs) because of their high protonic conductivity, σH, as well as chemical and thermal stability. The use of PFSA polymers with shorter side chains and lower equivalent weight (EW) than Nafion®, such as Aquivion® PFSA ionomers, is a valid approach to improve fuel cell performance and stability under drastic operative conditions such as those related to automotive applications. In this context, it is necessary to optimize the composition of the catalytic ink, according to the different ionomer characteristics. In this work, the influence of the ionomer amount in the catalytic layer was studied, considering the dispersing agent used to prepare the electrode (water or ethanol). Electrochemical studies were carried out in a single cell in the presence of H2-air, at intermediate temperatures (80-95 °C), low pressure, and reduced humidity ((50% RH). %). The best fuel cell performance was found for 26 wt.% Aquivion® at the electrodes using ethanol for the ink preparation, associated to a maximum catalyst utilization.

Mechanocatalytic Depolymerization of Cellulose With Perfluorinated Sulfonic Acid Ionomers.

Here, we investigated that the mechanocatalytic depolymerization of cellulose in the presence of Aquivion, a sulfonated perfluorinated ionomer. Under optimized conditions, yields of water soluble sugars of 90-97% were obtained using Aquivion PW98 and PW66, respectively, as a solid acid catalyst. The detailed characterization of the water soluble fraction revealed (i) the selective formation of oligosaccharides with a DP up to 11 and (ii) that depolymerization and reversion reactions concomitantly occurred during the mechanocatalytic process, although the first largely predominated. More importantly, we discussed on the critical role of water contained in Aquivion and cellulose on the efficiency of the mechanocatalytic process.

Conversion of Cellulose into Amphiphilic Alkyl Glycosides Catalyzed by Aquivion, a Perfluorosulfonic Acid Polymer.

The perfluorosulfonic acid (PFSA) Aquivion PW98 is an amphiphilic solid superacid which is shown to catalyze the conversion of cellulose into amphiphilic alkyl glycosides (AAGs) in 85 % yield (with 97 % selectivity). The process involves a mechanocatalytic depolymerization of cellulose followed by a direct glycosylation with n-dodecanol. In comparison to H2 SO4 and solid acid catalysts commonly employed in cellulose processing, Aquivion PFSA PW98 is not only recyclable but also exhibits superior catalytic performances in terms of yield, selectivity, and reactor productivity.

Quantitative in Situ Analysis of Ionomer Structure in Fuel Cell Catalytic Layers.

A quantitative in situ investigation of the structure of the catalytic layer of polymer electrolyte membrane fuel cells using material-sensitive and conductive atomic force microscopy is reported. The distribution and size of the ionomer phase at the surface of the catalytic layer is retrieved from adhesion force mappings, measured at high humidity and up to 75 °C. The average ionomer layer thickness varies between 7 and 13 nm for three differently prepared samples, as concluded from the histograms. Evidence of a lamellar structure of the thinner ionomer layers is presented. A significant thinning of the ionomer layers after long-term fuel cell operation is observed.

Advances in parallel screening of drug candidates.

In the hit to lead process, a drug candidate is selected from a set of potential leads by screening its binding with potential targets. This review focuses on the lead identification assays that employ a bio-chemical or bio-physical test to detect molecular recognition events between proteins and small molecules in a parallel format. These tests require either the lead or the target immobilization followed by incubation with the set of potential interaction partners and detection of a signal related to the target-ligand binding. In the first part of the review the different detection strategies amenable for drug screening are discussed. In the second part, a review of immobilization approaches for leads or targets, allowing the parallel screening of arrays of molecules, is presented.

Advanced polymers for molecular recognition and sensing at the interface.

In the few last years, the need of reliable, fast and inexpensive methods for selective analysis of specific substances in complex mixtures has grown exponentially. In particular, the detection of biomolecules, such as oligonucleotides, proteins, peptides and carbohydrates is of outstanding importance in gene expression, drug design and medicine studies. To these purposes, molecular recognition on microarray-configured devices is one of the most promising tools. This technology uses a number of different substrates such as glass, silicon, alumina or gold-coated slides. The use of polymers is a very effective way to tailor surface properties introducing functional groups able to bind biomolecules and prevent denaturation and non-specific binding. Furthermore, advanced polymers, thanks to their particular physico-chemical properties, can be used to improve selectivity and sensitivity during assays. This review will provide very recent examples of polymer-mediated molecular recognition between guest molecules in solution and host molecules located at the solid phase.