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Ruthenium “Melt”-Catalyzed Oxonation of Terminal and Internal Olefins to Linear Aldehydes/Alcohols
Published in Dale W. Blackburn, Catalysis of Organic Reactions, 2020
While the quaternary phosphonium salts provide the unique reaction media for these oxo syntheses, their structure can also significantly impact both the catalytic activity and selectivity.10 Starting with internal C8 olefins, the highest nonanal/nonanol linearity is achieved with the ruthenium(IV) oxide-tetrabutylphosphonium acetate couple. In this case the linearity of the nonanol fraction is 68% (see Table 2; ex. 18). The spectra of the solutions also feature the vCO bands at 1954, 1989, and 2015 cm–1, characteristic of the ruthenium carbonyl cluster anion, [HRu3(CO)11]–. The presence of a pair of additional bands at 1710 and 1743 cm 1 in the bridging carbonyl region (Fig. 1B) may indicate, however, the importance of both solvent-separated and contact ion-paired species in this media.
Niobium Based Materials for Supercapacitors
Published in Inamuddin, Rajender Boddula, Mohd Imran Ahamed, Abdullah Mohamed Asiri, Inorganic Nanomaterials for Supercapacitor Design, 2019
Prasun Banerjee, Adolfo Franco Junior, D. Baba Basha, K. Chandra Babu Naidu, K. Srinivas
Ruthenium (IV) oxide is one of the most promising materials that have been studied extensively in the last decade as hybrid supercapacitor electrode because of its excellent cycle life, specific capacitance, and conductance [26]. The material application limitation as a supercapacitor was due to its expensive nature, but the study led by the Augustyn et al. indicates the fact that niobium-based inorganic materials have higher capacity at high rates, indicating a suitable material for the hybrid supercapacitor applications [27]. But the result also suggested that EC feature in niobium-based materials arises at the surface of the material rather than come as the bulk crystalline properties. The theoretical calculation of the Lubimtsev et al. [28] using the density functional theory method indicates that the nanoporous structure with niobium-based material can improve the performance of the pseudo capacitors by resulting high-rate pseudo capacitance. Hence a high-temperature synthesis of niobium-based materials with temperature more than 600°C can result in nanoclusters, which act as a deterrent factor between fast double-layer cathode and slow faradaic anode in the high-power electrode devices. Hence orthorhombic nanoparticles of niobium pentoxide (Nb2O5) can be considered one of the most suitable materials to improve the kinematics of the faradaic anode.
Oxidation and Reduction Approaches for Treatment of Perfluoroalkyl Substances
Published in David M. Kempisty, Yun Xing, LeeAnn Racz, Perfluoroalkyl Substances in the Environment, 2018
Blossom N. Nzeribe, Selma M. Thagard, Thomas M. Holsen, Gunnar Stratton, Michelle Crimi
Schaefer et al. (2015) demonstrated the treatment potential of electrochemical oxidation of PFOA and PFOS in AFFF-impacted groundwater using a ruthenium(IV) oxide–coated titanium electrode (Ti/RuO2). They found that increasing current density led to increased PFOA decomposition. For PFOS, decomposition slowed down after some time, suggesting the saturation of anode-reactive sites. However, no fluoride or shorter-chain-length PFAS were observed in solution. They further investigated the transformation products of PFAS using synthetic groundwater. Defluorination results showed that there was no fluoride loss in the membrane; rather, volatilization of HF or hypofluorous acid (HOF) occurred, with PFOS showing the highest fluoride recovery (98%), followed by PFOA (58%). Trace amounts of shorter-chain PFAS were measured in solution, which Schaefer et al. (2015) explained were formed by decomposition reactions of PFAS on the anode surface with limited release of shorter-chain PFAS from the electrode surface to the aqueous phase. Carter and Farrell (2008) reported a similar increase in PFOS decomposition using a Si/BDD anode with increasing current density. Complete decomposition of PFOS was observed at a current density of 20 mA/cm2 using sodium perchlorate (NaClO4) as an electrolyte in a parallel-plate flow-through reactor, while 50% removal was observed in a rotating disk electrode reactor. Liao and Farrell (2009) further investigated the degradation of PFBS using the same conditions as in Carter and Farrell (2008). They reported an almost complete removal and defluorination of PFBS, with TFA as the only identified intermediate.
Electrochemically activated persulfate and peroxymonosulfate for furfural removal: optimization using Box–Behnken design
Published in Environmental Technology, 2023
Emine Can-Güven, Fatih Ilhan, Kubra Ulucan-Altuntas, Senem Yazici Guvenc, Gamze Varank
Experimental studies were conducted in a laboratory-scale electrolytic reactor made of plexiglass material. The dimensions of the reactor were 6.5 cm width x 5 cm length and 9 cm height. Platinum coated Ti (Pt/Ti), ruthenium (IV) oxide coated Ti (RuO2/Ti), graphite, mixed metal oxide coated TiO2 (MMO/TiO2) electrodes as the anode, and titanium electrode as cathode was placed in of the reactor. The distance between the electrodes was 6 cm, and the dimensions of the electrodes were 6 cm width x 12 cm height and 0.1 cm thickness. Graphite anode was a plate electrode while other anodes were mesh electrodes. Potassium nitrate (40 mM) was added to the reactor as an electrolytic solution. 150 mL sample with 250 mg/L furfural concentration was used for each set of the experimental study. The concentration of persulfate and peroxymonosulfate to be added was determined in the preliminary trials. Experimental sets based on reaction time were carried out to select the most effective anode. Pt/Ti, RuO2/Ti, Graphite, MMO/TiO2 electrodes were used as the anode, and Ti was used as the cathode.
Physico-Chemical Processes for the Treatment of Per- And Polyfluoroalkyl Substances (PFAS): A review
Published in Critical Reviews in Environmental Science and Technology, 2019
Blossom Nwedo Nzeribe, Michelle Crimi, Selma Mededovic Thagard, Thomas M. Holsen
Schaefer et al. (2015) demonstrated the treatment potential of electrochemical oxidation of PFOA and PFOS in AFFF-impacted groundwater using a ruthenium (IV) oxide coated titanium electrode (Ti/RuO2). They found that increasing current density led to increased PFOA degradation. However, no fluoride or shorter chain length PFCAs were observed in solution. It is possible that as electrolysis proceeded, the short chain PFCAs that may have formed further decomposed to volatile PFCAs such as TFA and transferred into the gas phase (Carter and Farrell, 2008; Zhuo et al., 2012; Niu et al., 2016). For PFOS, degradation slowed down after some time suggesting the saturation of reactive anode sites. They further investigated the transformation products of PFAS using synthetic groundwater. Defluorination results showed that PFOS had the highest fluoride recovery followed by PFOA. Trace amounts of shorter chain PFAS were measured in solution, which Schaefer et al. (2015) indicated were formed by degradation reactions of PFAS on the anode surface with a limited release of shorter chain PFAS from the electrode surface to the aqueous phase. Carter and Farrell (2008) reported a similar increase in PFOS degradation using a Si/BDD anode with increasing current density. Complete degradation of PFOS was observed in a parallel plate flow-through reactor, relative to a rotating disk electrode reactor. Using the same conditions, Liao & Farrell (2009) further investigated the degradation of PFBS and reported an almost complete removal and defluorination of PFBS with TFA as the only identified intermediate.