A quantitative and highly selective hydrogenolysis of glycerol to 1,2-propanediol was achieved under mild conditions over bifunctional Ru/WOx catalysts.
Herein we investigate a lowly flammable electrolyte formed by dissolving sodium trifuoromethansulfonate (NaCF3SO3) salt in triethylene glycol dimethyl ether (TREGDME) solvent as suitable medium for application in Na-ion and Na-S cells. The study, performed by using various electrochemical techniques, including impedance spectroscopy, voltammetry, and galvanostatic cycling, indicates for the solution high ionic conductivity and sodium transference number (t +), suitable stability window, very low electrode/electrolyte interphase resistance and sodium stripping/deposition overvoltage. Direct exposition to flame reveals the remarkable safety of the solution due to missing fire evolution under the adopted experimental setup. The solution is further investigated in sodium cells using various electrodes, i.e., mesocarbon microbeads (MCMB), tin-carbon (Sn-C), and sulfur-multiwalled carbon nanotubes (S-MWCNTs). The results show suitable cycling performances, with stable capacity ranging from 90 mAh g −1 for MCMB to 140 mAh g −1 for Sn-C, and to 250 mAh g −1 for S-MWCNTs, as an important additional bonus for enhancing the battery safety level [29-31]. A room-temperature rechargeable sodium-ion battery was formed by coupling the layered P2-Na0.7CoO2 cathode with the graphite anode in an electrolyte formed by NaClO4 salt in tetraethylene glycol dimethyl (TEGDME) [32]. This rocking chair cell, operating though sodium intercalation/de-intercalation processes within the cathode and anode layers, has shown suitable electrode/electrolyte interphase, and excellent performance in terms of cycle life, efficiency, and power capability [32]. A rechargeable sodium-oxygen cell has been reported to efficiently operate at room temperature employing a cathode formed by multiwalled carbon nanotubes (MWCNTs) cast on a gas diffusion layer in a TEGDME-NaCF3SO3 electrolyte solution [33]. The above Na/O2 cell has shown charge-discharge polarization as low as 400 mV, a capacity of 500 mAh g −1 and an energy efficiency of 83% for several cycles [33]. Diethylene glycol dimethyl ether (DEGDME) dissolving NaCF3SO3 has been used as the electrolyte in a room temperature sodium-sulfur cell using a S-MWCNTs composite, revealing average working voltage of about 1.8 V and a specific capacity of the order of 500 mAh g −1 [17], while a sodium-ion cell combining nanostructured Sn-C anode and hollow carbon spheres-sulfur (HCS-S) cathode in a TEGDME-NaCF3SO3 electrolyte revealed remarkable capacity of 550 mAh g −1 and theoretical energy density of 550 Wh kg −1 [34]. These encouraging results have suggested the use of glyme-based electrolytes as the preferred electrolyte media for a series of very attracting energy storage systems based on sodium, including Na-ion, Na/S and Na/O2 batteries. Therefore, in this work we investigate a solution formed by dissolving NaCF3SO3 in triethylene glycol dimethyl ether (TREGDME) as suitable electrolyte for sodium battery. The solution is studied by various electrochemical techniques in order to determine its ionic conductivi...
A multiphase (MP) system composed of two immiscible liquids, water and isooctane, and commercial 5% Ru/C as a catalyst, both with and without an additional organic liquid (OL: tetrahydrofuran (THF), 2-methyl-THF, methyl isobutyl carbinol, and cyclopentyl methyl ether) was designed and investigated for the chemoselective catalytic hydrogenation of four model examples of biobased sugars and amino/amido-sugars. At 110 °C and 40 bar of H2, d-glucosamine hydrochloride and N-acetyl-d-glucosamine were converted selectively into their corresponding hydrogenated derivatives, 2-amino-d-sorbitol and 2-acetamide-d-sorbitol, respectively, isolated in >99% yields. Both the reagents and the products were converted and formed in the aqueous phase, respectively, while, by tuning the relative proportions of water, isooctane, and the third added liquid (particularly THF), the catalyst (Ru/C) was perfectly segregated in the organic layer, where it could be recycled and reused up to nine times without any loss of activity and selectivity, in a semicontinuous mode. Under such conditions, the reaction was implemented on a gram scale with a productivity up to 0.89 mmol 2-amino-d-sorbitol/(gcat h). The same hydrogenation efficiency and reagent/product/catalyst separation were achieved during the MP reactions of d-glucose and d-maltose. In this case, however, results were independent of the MP composition: at 120 °C and 20–40 bar of H2, using either H2O/isooctane or H2O/isooctane/OL systems, a quantitative conversion of d-glucose and d-maltose was reached with a selectivity up to 78 and >99% toward sorbitol and maltitol, respectively. Ru/C was perfectly separated out of the aqueous phase in both MP mixtures, with a negligible metal leaching, below 0.01 wt %. The multiphase approach for all the tested substrates proved not only to be an original and robust protocol to improve the product isolation and catalyst recycling, but also effective in preventing metal contamination in the synthesis of final derivatives.
High anthropogenic CO2 emissions are among the main causes of climate change. Herein, we investigate the use of CO2 for the synthesis of organic cyclic carbonates on metal-free nitrogen-doped carbon catalysts obtained from chitosan, chitin, and shrimp shell wastes, both in batch and in continuous flow (CF). The catalysts were characterized by N2 physisorption, CO2-temperature-programmed desorption, X-ray photoelectron spectroscopy, scanning electron microscopy, and CNHS elemental analysis, and all reactivity tests were run in the absence of solvents. Under batch conditions, the catalyst obtained by calcination of chitin exhibited excellent performance in the conversion of epichlorohydrin (selected as a model epoxide), resulting in the corresponding cyclic carbonate with 96% selectivity at complete conversion, at 150 °C and 30 bar CO2, for 4 h. On the other hand, in a CF regime, a quantitative conversion and a carbonate selectivity >99% were achieved at 150 °C, by using the catalyst obtained from shrimp waste. Remarkably, the material displayed an outstanding stability over a reaction run time of 180 min. The robustness of the synthetized catalysts was confirmed by their good operational stability and reusability: ca. (75 ± 3)% of the initial conversion was achieved/retained by all systems, after six recycles. Also, additional batch experiments proved that the catalysts were successful on different terminal and internal epoxides.
Three different multiphase systems (MP 1–3) comprised of two immiscible liquids, with or without an ionic liquid (IL: methyltrioctyl ammonium chloride), were investigated for the oxidation of 5‐hydroxymethyl‐furfural (HMF) over 5 % Ru/C as a catalyst and air (8 bar) as an oxidant. These conditions proved versatile for an excellent control of the reaction selectivity to 4 distinct products derived from full or partial oxidation of the carbonyl and alcohol functions of HMF, and each one achieved in 87–96 % isolated yield at complete conversion. MP1 based on water and isooctane, yielded 2,5‐furandicarboxylic acid (FDCA, 91 % yield). In MP2, obtained by adding the IL to MP1, the oxidation proceeded towards the formation of 5‐formyl‐2‐furancarboxylic acid (FFCA, 87–89 % yield). MP2 also proved successful in the design of a one pot–two step oxidation/reduction sequence to prepare 5‐hydroxymethyl‐2‐furancarboxylic acid (HMFCA, 85 % yield). In MP3, the use of an acetonitrile/cyclooctane biphase yielded 2,5‐diformylfuran (DFF, 96 % yield). All the multiphase systems MP 1–3 allowed a perfect segregation of the catalyst in a single phase (either the hydrocarbon or the IL) distinct from the one containing HMF and its oxidation products. This was crucial not only for the catalyst/product separation but also for the recycle of Ru/C that was possible under all the tested conditions. Accordingly, MP‐reaction were run in a semicontinuous mode without removing the catalyst from the reactor nor resorting to conventional separation and activation techniques. Negligible Ru leaching, less than 0.96 ppb, was measured in all cases.
A series of catalysts based on non-noble metal nanoparticles supported on chitin-derived N-doped carbons was prepared through a one-step protocol in the presence of EDTA as a ligand. Both the...
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