Articoli di riviste: "Ruthenium-based catalysts"

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Singh, Keisham. "Recent Advances in C–H Bond Functionalization with Ruthenium-Based Catalysts". Catalysts 9, n. 2 (12 febbraio 2019): 173. http://dx.doi.org/10.3390/catal9020173.

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The past decades have witnessed rapid development in organic synthesis via catalysis, particularly the reactions through C–H bond functionalization. Transition metals such as Pd, Rh and Ru constitute a crucial catalyst in these C–H bond functionalization reactions. This process is highly attractive not only because it saves reaction time and reduces waste,but also, more importantly, it allows the reaction to be performed in a highly region specific manner. Indeed, several organic compounds could be readily accessed via C–H bond functionalization with transition metals. In the recent past, tremendous progress has been made on C–H bond functionalization via ruthenium catalysis, including less expensive but more stable ruthenium(II) catalysts. The ruthenium-catalysed C–H bond functionalization, viz. arylation, alkenylation, annulation, oxygenation, and halogenation involving C–C, C–O, C–N, and C–X bond forming reactions, has been described and presented in numerous reviews. This review discusses the recent development of C–H bond functionalization with various ruthenium-based catalysts. The first section of the review presents arylation reactions covering arylation directed by N–Heteroaryl groups, oxidative arylation, dehydrative arylation and arylation involving decarboxylative and sp3-C–H bond functionalization. Subsequently, the ruthenium-catalysed alkenylation, alkylation, allylation including oxidative alkenylation and meta-selective C–H bond alkylation has been presented. Finally, the oxidative annulation of various arenes with alkynes involving C–H/O–H or C–H/N–H bond cleavage reactions has been discussed.

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Nahra, Fady, e Catherine S. J. Cazin. "Sustainability in Ru- and Pd-based catalytic systems using N-heterocyclic carbenes as ligands". Chemical Society Reviews 50, n. 5 (2021): 3094–142. http://dx.doi.org/10.1039/c8cs00836a.

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This review is a critical presentation of catalysts based on palladium and ruthenium bearing N-heterocyclic carbene ligands that have enabled a more sustainable approach to catalysis and to catalyst uses.

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Weissenberger, Tobias, Ralf Zapf, Helmut Pennemann e Gunther Kolb. "Catalyst Coatings for Ammonia Decomposition in Microchannels at High Temperature and Elevated Pressure for Use in Decentralized and Mobile Hydrogen Generation". Catalysts 14, n. 2 (26 gennaio 2024): 104. http://dx.doi.org/10.3390/catal14020104.

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We report an investigation of catalyst performance for the decomposition of ammonia under industrially relevant conditions (high temperatures of up to 800 °C and an elevated pressure of 5 bar) with further emphasis on their stability at high reaction temperatures. The catalysts were applied and tested as coatings in 500 µm wide channels of microreactors. Nickel-based catalysts were studied and compared to a ruthenium-based catalyst supported on SiO2. The effect of the support on the catalytic performance was investigated, and CeO2-supported nickel catalysts were found to exhibit the highest activity. Promoters were applied to increase the NH3 decomposition activity of the Ni/CeO2 catalysts. The addition of cesium led to a slight reduction in activity, while lanthanum, calcium, and barium doping resulted in increased activity. In particular, the barium-doped Ni/CeO2 catalyst showed very high ammonia conversion and closed the activity gap with respect to ruthenium catalysts at reactor temperatures of 650 °C and higher. The hydrogen production rates achieved in this work were compared to values in the literature and were shown to exceed values found earlier for both nickel- and ruthenium-based catalysts. Furthermore, the ruthenium-based catalysts under investigation were rapidly deactivated at 700 °C, while the nickel-based catalysts did not show deactivation after 220 h on time on stream at 700 °C.

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Podolean, Iunia, Mara Dogaru, Nicolae Cristian Guzo, Oana Adriana Petcuta, Elisabeth E. Jacobsen, Adela Nicolaev, Bogdan Cojocaru, Madalina Tudorache, Vasile I. Parvulescu e Simona M. Coman. "Highly Efficient Ru-Based Catalysts for Lactic Acid Conversion to Alanine". Nanomaterials 14, n. 3 (29 gennaio 2024): 277. http://dx.doi.org/10.3390/nano14030277.

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The primary objective of this research was to develop efficient solid catalysts that can directly convert the lactic acid (LA) obtained from lignocellulosic biomass into alanine (AL) through a reductive amination process. To achieve this, various catalysts based on ruthenium were synthesized using different carriers such as multi-walled carbon nanotubes (MWCNTs), beta-zeolite, and magnetic nanoparticles (MNPs). Among these catalysts, Ru/MNP demonstrated a remarkable yield of 74.0% for alanine at a temperature of 200 °C. This yield was found to be superior not only to the Ru/CNT (55.7%) and Ru/BEA (6.6%) catalysts but also to most of the previously reported catalysts. The characterization of the catalysts and their catalytic results revealed that metallic ruthenium nanoparticles, which were highly dispersed on the external surface of the magnetic carrier, significantly enhanced the catalyst’s ability for dehydrogenation. Additionally, the -NH2 basic sites on the catalyst further facilitated the formation of alanine by promoting the adsorption of acidic reactants. Furthermore, the catalyst could be easily separated using an external magnetic field and exhibited the potential for multiple reuses without any significant loss in its catalytic performance. These practical advantages further enhance its appeal for applications in the reductive amination of lactic acid to alanine.

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Reany, Ofer, e N. Gabriel Lemcoff. "Light guided chemoselective olefin metathesis reactions". Pure and Applied Chemistry 89, n. 6 (27 giugno 2017): 829–40. http://dx.doi.org/10.1515/pac-2016-1221.

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AbstractAn appealing concept in synthetic chemistry is photo-induced catalysis; where dormant complexes become catalytically active upon activation with light. The ruthenium-based olefin metathesis complexes founded on the original Grubbs catalyst have probably been one of the most widely studied families of catalysts for the past 25 years. Greater stability and versatility of these olefin-metathesis catalysts has been achieved by careful design of the ligand sphere, including latent catalysts which are activated by external stimuli. This article describes our recent developments towards light-induced olefin metathesis reactions based on photoactive sulfur-chelated ruthenium benzylidene catalysts. Alternative chemical reactions, be it photo-induced olefin metathesis or other direct photochemical processes, by using light of different frequencies were studied in chemoselective chromatic orthogonal pathways. The lessons learned during the development of these reactions have given birth to selective photo-deprotection sequences and novel pathways for stereolithographic applications.

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Chen, Hui, Runxu Deng, Shixin Gao e Feng Liu. "Preparation of porous iridium-ruthenium-based acidic water oxidation catalyst by ascorbic acid reduction and evaporation". Journal of Physics: Conference Series 2566, n. 1 (1 agosto 2023): 012017. http://dx.doi.org/10.1088/1742-6596/2566/1/012017.

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Abstract Green hydrogen is the ultimate direction for energy development technology. Hereon, the porous materials of promoted iridium-ruthenium-based catalyst were prepared by ascorbic acid reduction and evaporation drying methods. The unsupported iridium ruthenium-based catalysts were porous structures, characterized by scanning electron microscopes (SEM). In 0.5 mol·L−1 H2SO4, the electrochemical oxygen precipitation reaction overpotential was only 251 mV at 10 mA·cm2, compared to commercial 303 mV. The polarization overpotential was not significantly reduced, after 20 000 cycles of accelerated cyclic aging experiments. The porous structure of the iridium-ruthenium-based catalysts showed higher catalytic activity for oxygen precipitation than the commercial IrO2(ZrO2) catalysts. Porous materials could improve the activity of catalysts, which provides a good research idea for the synthesis of electrocatalysts.

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Truszkiewicz, Elżbieta, Wioletta Raróg-Pilecka, Magdalena Zybert, Malwina Wasilewska-Stefańska, Ewa Topolska e Kamila Michalska. "Effect of the ruthenium loading and barium addition on the activity of ruthenium/carbon catalysts in carbon monoxide methanation". Polish Journal of Chemical Technology 16, n. 4 (1 dicembre 2014): 106–10. http://dx.doi.org/10.2478/pjct-2014-0079.

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Abstract A group of supported ruthenium catalysts was prepared and tested in methanation of small CO amounts (7000 ppm) in hydrogen-rich streams. High surface area graphitized carbon (484 m2/g) was used as a support for ruthenium and RuCl3 was used as a Ru precursor. Some of the Ru/C systems were additionally doped with barium (Ba(NO3)2 was barium precursor). The catalysts were characterized by the chemisorption technique using CO as an adsorbate. To determine the resistance of the catalysts to undesired carbon support methanation, the TG-MS experiments were performed. They revealed that the barium addition inhibits support losses. The studies of CO methanation (fl ow reactor, atmospheric pressure) have shown that some of the supported ruthenium catalysts exhibit high activities referred to the metal mass. The catalytic properties of ruthenium proved to be dependent on metal dispersion. Some of the Ru/C and Ba-Ru/C systems exhibit higher activity in CO hydrogenation than the commercial nickel-based catalyst.

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Zhong, He Xiang, Hua Min Zhang e Mei Ri Wang. "Oxygen Reduction Reaction on Carbon Supported Ruthenium-Based Electrocatalysts in PEMFC". Materials Science Forum 675-677 (febbraio 2011): 97–100. http://dx.doi.org/10.4028/www.scientific.net/msf.675-677.97.

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The ruthenium-based electrocatalysts supported on carbon black were prepared by the decarbonylation of the transition metal carbonyl with the 1,6-hexanediol as the solvent. The catalysts were characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution TEM (HRTEM). The electrochemical behaviours of the catalysts were investigated by cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements in 0.5 M H2SO4 solution. The catalysts demonstrate attractive catalytic activity towards the ORR. The catalyst is expected to be promising alternative non-Pt electrocatalysts for PEMFC.

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Ma, Peng, Jiaren Zhang, Xiaqian Wu e Jianhui Wang. "Ruthenium Metathesis Catalysts with Imidazole Ligands". Catalysts 13, n. 2 (26 gennaio 2023): 276. http://dx.doi.org/10.3390/catal13020276.

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Phosphine-free ruthenium benzylidene complexes containing imidazole ligands are reported. These catalysts are effective for ring-closing metathesis (RCM) and cross-metathesis (CM) reactions at high temperatures, where the more widely used phosphine-containing N-heterocyclic carbene-based ruthenium catalysts show side reactions. This discovery opens up a pathway to develop more selective ruthenium metathesis catalysts for reactions requiring harsh conditions.

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Dunn, E., e J. Tunge. "Decarboxylative Allylation of Ketone Enolates with Rh, Ir, and Mo". Latvian Journal of Chemistry 51, n. 1-2 (1 gennaio 2012): 31–40. http://dx.doi.org/10.2478/v10161-012-0007-x.

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Decarboxylative Allylation of Ketone Enolates with Rh, Ir, and MoA variety of catalysts were investigated for their ability to impart branched regioselectivity in decarboxylative allylation reactions. While catalysts based on Mo, Rh, and Ir were active catalysts, their regio-selectivities were low and the reactions required an equivalent of base for efficient coupling. Alternatively, a ruthenium-based catalyst was identi-fied that operates under neutral conditions and gives high branched selectivity in decarboxylative allylations.

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Lovic, Jelena. "The kinetics and mechanism of methanol oxidation on Pt and PtRu catalysts in alkaline and acid media". Journal of the Serbian Chemical Society 72, n. 7 (2007): 709–12. http://dx.doi.org/10.2298/jsc0707709l.

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The kinetic of methanol electrochemical oxidation for a series of platinum and platinum-ruthenium catalysts was investigated. A correlation between the beginning of OHad adsorption and methanol oxidation was demonstrated on Pt single crystals and Pt nanocatalyst. The activity of the nano-structured Pt catalyst was compared with single crystal platinum electrodes assuming the Kinoshita model of nanoparticles. The ruthenium-containing catalysts shifted the onset of methanol oxidation to more negative potentials. The effect was more pronounced in acid than in alkaline media. Based on the established diagnostic criteria, the reaction between COad and OHad species according to the Langmuir-Hinshelwood mechanism was proposed as the rate determining step in alkaline and acid media on Pt and PtRu catalysts. .

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Müller, Daniel S., Olivier Baslé e Marc Mauduit. "A tutorial review of stereoretentive olefin metathesis based on ruthenium dithiolate catalysts". Beilstein Journal of Organic Chemistry 14 (7 dicembre 2018): 2999–3010. http://dx.doi.org/10.3762/bjoc.14.279.

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Stereoretentive olefin metathesis based on ruthenium dithiolate complexes has become a very active field of research within the past years. This unique catalyst class is able to kinetically produce both Z- and E-alkenes in high stereochemical purity (typically >95:5) starting from stereochemically pure Z- or E-alkenes. The aim of this tutorial review is to organize the reported information concerning ruthenium dithiolate catalysts in a logic manner, thus providing an "operators handbook" for chemists who wish to apply this methodology in synthesis.

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Jawiczuk, Magdalena, Anna Marczyk e Bartosz Trzaskowski. "Decomposition of Ruthenium Olefin Metathesis Catalyst". Catalysts 10, n. 8 (5 agosto 2020): 887. http://dx.doi.org/10.3390/catal10080887.

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Ruthenium olefin metathesis catalysts are one of the most commonly used class of catalysts. There are multiple reviews on their uses in various branches of chemistry and other sciences but a detailed review of their decomposition is missing, despite a large number of recent and important advances in this field. In particular, in the last five years several new mechanism of decomposition, both olefin-driven as well as induced by external agents, have been suggested and used to explain differences in the decomposition rates and the metathesis activities of both standard, N-heterocyclic carbene-based systems and the recently developed cyclic alkyl amino carbene-containing complexes. Here we present a review which explores the last 30 years of the decomposition studied on ruthenium olefin metathesis catalyst driven by both intrinsic features of such catalysts as well as external chemicals.

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Bazhenova, Maria A., Leonid A. Kulikov, Daria A. Makeeva, Anton L. Maximov e Eduard A. Karakhanov. "Hydrodeoxygenation of Lignin-Based Compounds over Ruthenium Catalysts Based on Sulfonated Porous Aromatic Frameworks". Polymers 15, n. 23 (4 dicembre 2023): 4618. http://dx.doi.org/10.3390/polym15234618.

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Bifunctional catalysts are a major type of heterogeneous catalytic systems that have been widely investigated for biomass upgrading. In this work, Ru-catalysts based on sulfonated porous aromatic frameworks (PAFs) were used in the hydrodeoxygenation (HDO) of lignin-derived compounds: guaiacol, veratrole, and catechol. The relationship between the activity of metal nanoparticles and the content of acid sites in synthesized catalysts was studied. Herein, their synergy was demonstrated in the Ru-PAF-30-SO3H/5-COD catalyst. The results revealed that this catalytic system promoted partial hydrogenation of lignin-based compounds to ketones without any further transformations. The design of the Ru-PAF-30-SO3H/5-COD catalytic system opens a promising route to the selective conversion of lignin model compounds to cyclohexanone.

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Daniel, Quentin, Lei Wang, Lele Duan, Fusheng Li e Licheng Sun. "Tailored design of ruthenium molecular catalysts with 2,2′-bypyridine-6,6′-dicarboxylate and pyrazole based ligands for water oxidation". Dalton Transactions 45, n. 37 (2016): 14689–96. http://dx.doi.org/10.1039/c6dt01287f.

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A series of tailor-designed Ruthenium based water oxidation catalysts have been synthesized. By fine tuning of the catalyst structure, the turnover frequency was increased up to 500 s⁻¹and the stability over 6000 turnovers.

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Vieri, Hizkia Manuel, Arash Badakhsh e Sun Hee Choi. "Comparative Study of Ba, Cs, K, and Li as Promoters for Ru/La2Ce2O7-Based Catalyst for Ammonia Synthesis". International Journal of Energy Research 2023 (13 maggio 2023): 1–11. http://dx.doi.org/10.1155/2023/2072245.

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Ammonia is one of the promising carriers for hydrogen and a critical ingredient in many industries including fertilizers and pharmaceuticals. In the KAAP process, ruthenium- (Ru-) based catalysts showed 10-20 more activity compared with iron- (Fe-) based catalysts. The modifications that are applied to Ru-based catalysts revolve around changing the material of its support and/or promoters. This study compares the performance of a Ru-based catalyst for ammonia synthesis supported by La2Ce2O7 using barium (Ba), cesium (Cs), potassium (K), and lithium (Li) as promoters. Based on structural, physicochemical, adsorption, and electronic state analysis, the Cs-promoted catalyst is expected to perform best among all the promoted catalysts, while our findings suggest that the K-promoted catalyst performed the best in the actual catalytic reaction. This result will affect the development of Ru/La2Ce2O7-based catalysts, especially in ammonia synthesis at different temperatures and pressures.

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Gutiérrez-Flores, Selena, Lidia García-Barrera, Daniel Zárate-Saldaña e Jorge A. Cruz-Morales. "Synthesis of heterogeneous metathesis catalysts for the development of sustainable processes". Renewable Energy, Biomass & Sustainability 3, n. 1 (12 luglio 2022): 75–85. http://dx.doi.org/10.56845/rebs.v3i1.40.

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In recent decades, it has been tried to develop processes that involve the use of catalysts that can be recovered from the reaction medium, to make them green and sustainable. Approximately, 90 % of all processes in chemistry and petrochemicals use heterogeneous catalysts. In this sense, the supported heterogeneous catalysts present advantages in the purification of the products and the reduction of costs. In the present work, the synthesis of a new heterogeneous supported catalyst, highly active in the metathesis reaction, based on a ruthenium-alkylidene complex, was carried out. The new catalyst was obtained by anchoring of dichloro[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene](benzylidene)(tricyclohexylphosphine)ruthenium (II) (second generation Grubbs) in various silylated polymeric gels, based on 2-norbornene-5,6-dicarboxylic anhydride (NDA) and cis-cyclooctene (CO) cross-linked with various percentages of 3-aminopropyltriethoxysilane (APTES) (5%, 15%, 100%). The new heterogeneous catalyst was successfully used in the depolymerization reaction via metathesis of natural rubber from Oaxaca (HNO), using 1-octene as CTA; observing the formation of liquid oligomers, achieving a decrease in molecular weight from 137.941 g/mol to 297 g/mol; proving, in this way, its high effectiveness.

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Thongboon, Surached, Pacharaporn Rittiron, Danusorn Kiatsaengthong, Thanaphat Chukeaw e Anusorn Seubsai. "Propylene Epoxidation to Propylene Oxide Over RuO2, CuO, TeO2, and TiO2 Supported on Modified Mesoporous Silicas". Journal of Nanoscience and Nanotechnology 20, n. 6 (1 giugno 2020): 3466–77. http://dx.doi.org/10.1166/jnn.2020.17408.

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Direct gas phase epoxidation of propylene to propylene oxide (PO) using O2 is a challenging problem in catalysis research. Silica-supported ruthenium-copper-based catalysts have been recently reported to be promising for propylene epoxidation. In this work, mesoporous silica supports modified with RuO2, CuO, and TeO2 with and without TiO2 were investigated for propylene epoxidation to PO. The prepared catalysts were divided into two groups. The first group consisted of mesoporous silica supports modified with RuO2, CuO, and TeO2, and the second group consisted of the same components as the first group but adding TiO2. The prepared supports and catalysts were characterized using BET surface area analysis and other advanced instrument techniques. It was found that the catalyst made with RuO2 and TeO2 impregnated onto porous silica modified with CuO and TiO2 (denoted as RuTe/CuTiSi) exhibited an excellent PO formation of 344 gPO h−1 kg−1cat, which was superior to that of the other prepared catalysts. Moreover, the addition of TiO2 into the catalyst greatly improved the PO formation rate and the arrangement of active components in the catalyst and strongly influenced catalytic performance.

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Drummond, Samuel M., Jennifer Naglic, Thossaporn Onsree, Santosh K. Balijepalli, Alexis Allegro, Stephanie N. Orraca Albino, Katherine M. O’Connell e Jochen Lauterbach. "Promoted Ru/PrOx Catalysts for Mild Ammonia Synthesis". Catalysts 14, n. 9 (29 agosto 2024): 572. http://dx.doi.org/10.3390/catal14090572.

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Ammonia synthesis is one of the most important chemical reactions. Due to thermodynamic restrictions and the reaction requirements of the current commercial iron catalysts, it is also one of the worst reactions for carbon dioxide emissions and energy usage. Ruthenium-based catalysts can substantially improve the environmental impact as they operate at lower pressures and temperatures. In this work, we provide a screening of more than 40 metals as possible promoter options based on a Ru/Pr2O3 catalyst. Cesium was the best alkali promoter and was held constant for the series of double-promoted catalysts. Ten formulations outperformed the Ru-Cs/PrOx benchmark, with barium being the best second promoter studied and the most cost-effective option. Designs of experiments were utilized to optimize both the pretreatment conditions and the promoter weight loadings of the doubly promoted catalyst. As a result, optimization led to a more than five-fold increase in activity compared to the unpromoted catalyst, therefore creating the possibility for low-ruthenium ammonia synthesis catalysts to be used at scale. Further, we have explored the roles of promoters using kinetic analysis, X-ray Photoelectron Spectroscopy (XPS), and in situ infrared spectroscopy. Here, we have shown that the role of barium is to act as a hydrogen scavenger and donor, which may permit new active sites for the catalyst, and have demonstrated that the associative reaction mechanism is likely used for the unpromoted Ru/PrOx catalyst with hydrogenation of the triple bond of the dinitrogen occurring before any dinitrogen bond breakage.

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Pye, Scott J., Justin M. Chalker e Colin L. Raston. "Vortex Fluidic Ethenolysis, Integrating a Rapid Quench of Ruthenium Olefin Metathesis Catalysts". Australian Journal of Chemistry 73, n. 12 (2020): 1138. http://dx.doi.org/10.1071/ch20005.

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Ruthenium-catalysed ethenolysis occurs in a vortex fluidic device (VFD) – a scalable, thin-film microfluidic continuous flow process. This process takes advantage of the efficient mass transfer of gaseous reagents into the dynamic thin film of liquid. Also reported is the rapid quenching of the ruthenium-based olefin metathesis catalyst by the addition of a saturated solution of N-acetyl-l-cysteine in MeCN, as a convenient alternative to previously reported quenching methods.

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Sun, Xiandi, Zhiyuan Cheng, Hang Liu, Siyu Chen e Ya-Rong Zheng. "Porous Ruthenium–Tungsten–Zinc Nanocages for Efficient Electrocatalytic Hydrogen Oxidation Reaction in Alkali". Nanomaterials 14, n. 9 (6 maggio 2024): 808. http://dx.doi.org/10.3390/nano14090808.

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With the rapid development of anion exchange membrane technology and the availability of high-performance non-noble metal cathode catalysts in alkaline media, the commercialization of anion exchange membrane fuel cells has become feasible. Currently, anode materials for alkaline anion-exchange membrane fuel cells still rely on platinum-based catalysts, posing a challenge to the development of efficient low-Pt or Pt-free catalysts. Low-cost ruthenium-based anodes are being considered as alternatives to platinum. However, they still suffer from stability issues and strong oxophilicity. Here, we employ a metal–organic framework compound as a template to construct three-dimensional porous ruthenium–tungsten–zinc nanocages via solvothermal and high-temperature pyrolysis methods. The experimental results demonstrate that this porous ruthenium–tungsten–zinc nanocage with an electrochemical surface area of 116 m2 g−1 exhibits excellent catalytic activity for hydrogen oxidation reaction in alkali, with a kinetic density 1.82 times and a mass activity 8.18 times higher than that of commercial Pt/C, and a good catalytic stability, showing no obvious degradation of the current density after continuous operation for 10,000 s. These findings suggest that the developed catalyst holds promise for use in alkaline anion-exchange membrane fuel cells.

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Sanford, Melanie S, Lawrence M Henling, Michael W Day e Robert H Grubbs. "Ruthenium-Based Four-Coordinate Olefin Metathesis Catalysts". Angewandte Chemie 112, n. 19 (2 ottobre 2000): 3593–95. http://dx.doi.org/10.1002/1521-3757(20001002)112:19<3593::aid-ange3593>3.0.co;2-m.

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Sanford, Melanie S, Lawrence M Henling, Michael W Day e Robert H Grubbs. "Ruthenium-Based Four-Coordinate Olefin Metathesis Catalysts". Angewandte Chemie 39, n. 19 (2 ottobre 2000): 3451–53. http://dx.doi.org/10.1002/1521-3773(20001002)39:19<3451::aid-anie3451>3.0.co;2-u.

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Villani, Kenneth, Christine E. A. Kirschhock, Duoduo Liang, Gustaaf Van Tendeloo e Johan A. Martens. "Catalytic Carbon Oxidation Over Ruthenium-Based Catalysts". Angewandte Chemie 118, n. 19 (5 maggio 2006): 3178–81. http://dx.doi.org/10.1002/ange.200503799.

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Villani, Kenneth, Christine E. A. Kirschhock, Duoduo Liang, Gustaaf Van Tendeloo e Johan A. Martens. "Catalytic Carbon Oxidation Over Ruthenium-Based Catalysts". Angewandte Chemie International Edition 45, n. 19 (5 maggio 2006): 3106–9. http://dx.doi.org/10.1002/anie.200503799.

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Lei, Y. J., X. B. Wang, C. Song, F. H. Li e X. R. Wang. "A study on ruthenium-based catalysts for pharmaceutical wastewater treatment". Water Science and Technology 64, n. 1 (1 luglio 2011): 117–21. http://dx.doi.org/10.2166/wst.2011.585.

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Ruthenium-based catalysts were prepared by a saturation-dip method. Their catalytic activity was evaluated by a catalytic wet oxidation (CWO) process. The ruthenium-based catalysts were used to purify organic pharmaceutical wastewater with high concentration pyridine and pyridine derivatives that have high chemical oxygen demand (COD). In the CWO process, organic pharmaceutical wastewater was continuously pumped into fixed-bed reactors filled with Ru-based catalysts, while the organic components in wastewater were catalytically degraded by oxygen at high temperatures and pressures (temperature, 170–300 °C; pressure, 1.0–10 MPa). The experimental results showed that the prepared catalysts could effectively purify pharmaceutical wastewater with high concentration organic components, which are difficult to degrade biochemically, and that the removal rates of both COD and total nitrogen were over 99%.

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Simonneaux, Gérard, e Pietro Tagliatesta. "Metalloporphyrin catalysts for organic synthesis". Journal of Porphyrins and Phthalocyanines 08, n. 09 (settembre 2004): 1166–71. http://dx.doi.org/10.1142/s1088424604000507.

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Novel chiral systems for the catalytic asymmetric oxidation and cyclopropanation of olefins based on metalloporphyrins containing iron, ruthenium and manganese, have been recently introduced. High catalyst turnover numbers and sometimes high enantiomeric excess were observed. New catalytic reactions with metalloporphyrins have recently been reported; these are the olefination of aldehydes and cyclotrimerization of terminal alkynes. Dendrimers and polymers containing metalloporphyrins, have also been found to be efficient catalysts for oxidation and carbene transfer.

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Melián-Rodríguez, Saravanamurugan, Meier, Kegnæs e Riisager. "Ru-Catalyzed Oxidative Cleavage of Guaiacyl Glycerol--Guaiacyl Ether-a Representative -O-4 Lignin Model Compound". Catalysts 9, n. 10 (3 ottobre 2019): 832. http://dx.doi.org/10.3390/catal9100832.

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The introduction of efficient and selective catalytic methods for aerobic oxidation of lignin and lignin model compounds to aromatics can extend the role of lignin applications in biorefineries. The current study focussed on the catalytic oxidative transformation of guaiacyl glycerol--guaiacyl ether (GGGE)–a -O-4 lignin model compound to produce basic aromatic compounds (guaiacol, vanillin and vanillic acid) using metal-supported catalysts. Ru/Al2O3, prepared with ruthenium(IV) oxide hydrate, showed the highest yields of the desired products (60%) in acetonitrile in a batch reactor at 160 C and 5-bar of 20% oxygen in argon. Alternative catalysts containing other transition metals (Ag, Fe, Mn, Co and Cu) supported on alumina, and ruthenium catalysts based on alternative supports (silica, spinel, HY zeolite and zirconia) gave significantly lower activities compared to Ru/Al2O3 at identical reaction conditions. Moreover, the Ru/Al2O3 catalyst was successfully reused in five consecutive reaction runs with only a minor decrease in catalytic performance.

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Michrowska, Anna, e Karol Grela. "Quest for the ideal olefin metathesis catalyst". Pure and Applied Chemistry 80, n. 1 (1 gennaio 2008): 31–43. http://dx.doi.org/10.1351/pac200880010031.

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Attempts were made to create a catalyst that approaches Gladysz's vision of an "ideal catalyst". Modifications of the Hoveyda-Grubbs catalyst were carried out with the aim to increase its activity and broaden the scope of its applicability to challenging metathesis reactions. This was done by introduction of an electron-withdrawing substituent on the isopropoxybenzylidene group in order to diminish the donor properties of the oxygen atom. The resulting stable and easily accessible nitro-substituted Hoveyda-Grubbs catalyst has found a number of successful applications in various research and industrial laboratories. Also, a new concept for noncovalent immobilization of a ruthenium olefin metathesis catalyst is presented. The 2-isopropoxybenzylidene ligand of Hoveyda-Grubbs carbene is further modified by an additional amino group, and immobilization is achieved by treatment with sulfonated polystyrene, forming the corresponding ammonium salt. In this novel strategy for the immobilization of ruthenium-based metathesis catalysts, the amino group plays a dual role, being first an active anchor for immobilization and secondly, after protonation, activating the catalysts by electron-donating to -withdrawing switch. The same concept has been used in the preparation of a quaternary ammonium catalyst for aqueous olefin metathesis.

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Pieczykolan, Michał, Justyna Czaban-Jóźwiak, Maura Malinska, Krzysztof Woźniak, Reto Dorta, Anna Rybicka, Anna Kajetanowicz e Karol Grela. "The Influence of Various N-Heterocyclic Carbene Ligands on Activity of Nitro-Activated Olefin Metathesis Catalysts". Molecules 25, n. 10 (12 maggio 2020): 2282. http://dx.doi.org/10.3390/molecules25102282.

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A set of nitro-activated ruthenium-based Hoveyda-Grubbs type olefin metathesis catalysts bearing sterically modified N-hetero-cyclic carbene (NHC) ligands have been obtained, characterised and studied in a set of model metathesis reactions. It was found that catalysts bearing standard SIMes and SIPr ligands (4a and 4b) gave the best results in metathesis of substrates with more accessible C–C double bonds. At the same time, catalysts bearing engineered naphthyl-substituted NHC ligands (4d–e) exhibited high activity towards formation of tetrasubstituted C–C double bonds, the reaction which was traditionally Achilles’ heel of the nitro-activated Hoveyda–Grubbs catalyst.

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Echeverri, David Alexander, Luis Alberto Rios e Juan Miguel Marín. "Synthesising unsaturated fatty alcohols from fatty methyl esters using catalysts based on ruthenium and tin supported on alumina". Ingeniería e Investigación 31, n. 1 (1 gennaio 2011): 74–82. http://dx.doi.org/10.15446/ing.investig.v31n1.20528.

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Most promising catalysts for synthesising unsaturated fatty alcohols are based on group 8 metals with a promoter like tin, because the process can be carried out in moderate conditions, and these metals are less toxic than chromium. There have been no reports about the use of this catalyst to date using raw materials like methyl ester blends or evaluation reusing catalysts. This paper presents the hydrogenation of methyl esters from palm oil and commercial methyl oleate with Ru-Sn/Al2O3 catalysts prepared by impregnation, at moderate pressure and temperature (5 MPa and 270°C). Greater selectivity to unsaturated alcohol and the less selectivity to methyl stearate was found for an optimal Sn:Ru=2 ratio. Hydrogenation of palm oil methyl esters with this catalyst produced a mixture of oleyl alcohol, saturated alcohols having 16-18 carbon atoms and heavy esters. Raw material had no great effect on catalyst activity. However, the catalyst showed deactivation through several uses due to decreased catalytic area.

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Yim, Kyungmin, Yoomo Koo, Sung Jong Yoo e Jinsoo Kim. "Facile Spray Pyrolysis Synthesis of Ruthenium Single-Atomic Catalyst with High Activity and Stability for Hydrogen Evolution Reactions over a Wide pH Range". ECS Meeting Abstracts MA2022-01, n. 34 (7 luglio 2022): 1394. http://dx.doi.org/10.1149/ma2022-01341394mtgabs.

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Electrochemical water splitting is an economic, green and sustainable route to produce hydrogen through the hydrogen evolution reaction (HER). Nowadays, ruthenium is an efficient catalyst with a desirable cost for HER. Doping Ru with a transition metal oxide was recently shown to greatly boost the activity and durability of the HER, even with small amounts of ruthenium based electrocatalysts. It also reduced total amount of Ru. Recent literature reported that Ru-O-Mo sites have better HER than Ru single atom due to significantly improved H2O adsorption. Among the various synthetic method, spray pyrolysis methods can produce rapidly large-scale production of uniformly mixed elements in spherical particles at one-step. In this study, we synthesized ruthenium doped MoO2 spheres (200~300nm) using ultrasonic spray pyrolysis method in various temperature from 500 oC to 800 oC. The synthesized catalysts were analyzed by XRD, FE-SEM, Raman, XPS and electrochemical analyzer. This research can provide a new strategy to synthesize highly active catalysts for HER over a wide pH range.

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Telleria, A., P. W. N. M. van Leeuwen e Z. Freixa. "Azobenzene-based ruthenium(ii) catalysts for light-controlled hydrogen generation". Dalton Transactions 46, n. 11 (2017): 3569–78. http://dx.doi.org/10.1039/c7dt00542c.

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34

Zhang, Yajing, Qian Wang, Zongsheng Yan, Donglai Ma e Yuguang Zheng. "Visible-light-mediated copper photocatalysis for organic syntheses". Beilstein Journal of Organic Chemistry 17 (12 ottobre 2021): 2520–42. http://dx.doi.org/10.3762/bjoc.17.169.

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Photoredox catalysis has been applied to renewable energy and green chemistry for many years. Ruthenium and iridium, which can be used as photoredox catalysts, are expensive and scarce in nature. Thus, the further development of catalysts based on these transition metals is discouraged. Alternative photocatalysts based on copper complexes are widely investigated, because they are abundant and less expensive. This review discusses the scope and application of photoinduced copper-based catalysis along with recent progress in this field. The special features and mechanisms of copper photocatalysis and highlights of the applications of the copper complexes to photocatalysis are reported. Copper-photocatalyzed reactions, including alkene and alkyne functionalization, organic halide functionalization, and alkyl C–H functionalization that have been reported over the past 5 years, are included.

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35

Ogba, O. M., N. C. Warner, D. J. O’Leary e R. H. Grubbs. "Recent advances in ruthenium-based olefin metathesis". Chemical Society Reviews 47, n. 12 (2018): 4510–44. http://dx.doi.org/10.1039/c8cs00027a.

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Abstract (sommario):

Ruthenium-based olefin metathesis catalysts, known for their functional group tolerance and broad applicability in organic synthesis and polymer science, continue to evolve as an enabling technology in these areas.

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Borisov, Vadim A., Zaliya A. Fedorova, Victor L. Temerev, Mikhail V. Trenikhin, Dmitry A. Svintsitskiy, Ivan V. Muromtsev, Alexey B. Arbuzov, Alexey B. Shigarov, Pavel V. Snytnikov e Dmitry A. Shlyapin. "Ceria–Zirconia-Supported Ruthenium Catalysts for Hydrogen Production by Ammonia Decomposition". Energies 16, n. 4 (9 febbraio 2023): 1743. http://dx.doi.org/10.3390/en16041743.

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Сommercial cerium–zirconium oxide supports (Ce0.5Zr0.5O2, Ce0.75Zr0.25O2, and Ce0.4Zr0.5Y0.05La0.05O2) were used to prepare Ru/CeZrOx catalysts. According to the XRD and IR spectroscopy data, the supports consist of ceria-based substitutional solid solutions. The specific surface areas of supports and catalysts are similar and range from 71–89 m2/g. As shown by TEM and XRD methods, the size of support particles equals 6–11 nm. According to the TEM data, the size of ruthenium particles does not exceed 1.3 nm. The catalyst activity in the ammonia decomposition process was studied. The Ru/Ce0.75Zr0.25O2 catalyst at temperature 500 °C and GHSV 120,000 h−1 demonstrated the highest hydrogen productivity of 53.3 mmol H2/(gcat·min) and compares well with the best results reported in the literature. The kinetics of ammonia decomposition reaction were calculated using the Temkin–Pyzhov exponential expression. The developed mathematical model well described the experimental data. The studied catalysts demonstrated high activity for the ammonia decomposition reaction.

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37

Martins, Joana A., A. Catarina Faria, Miguel A. Soria, Carlos V. Miguel, Alírio E. Rodrigues e Luís M. Madeira. "CO2 Methanation over Hydrotalcite-Derived Nickel/Ruthenium and Supported Ruthenium Catalysts". Catalysts 9, n. 12 (1 dicembre 2019): 1008. http://dx.doi.org/10.3390/catal9121008.

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In this work, in-house synthesized NiMgAl, Ru/NiMgAl, and Ru/SiO2 catalysts and a commercial ruthenium-containing material (Ru/Al2O3com.) were tested for CO2 methanation at 250, 300, and 350 °C (weight hourly space velocity, WHSV, of 2400 mLN,CO2·g−1·h−1). Materials were compared in terms of CO2 conversion and CH4 selectivity. Still, their performances were assessed in a short stability test (24 h) performed at 350 °C. All catalysts were characterized by temperature programmed reduction (TPR), X-ray diffraction (XRD), N2 physisorption at −196 °C, inductively coupled plasma optical emission spectrometry (ICP-OES), and H2/CO chemisorption. The catalysts with the best performance (i.e., the hydrotalcite-derived NiMgAl and Ru/NiMgAl) seem to be quite promising, even when compared with other methanation catalysts reported in the literature. Extended stability experiments (240 h of time-on-stream) were performed only over NiMgAl, which was selected based on catalytic performance and estimated price criteria. This catalyst showed some deactivation under conditions that favor CO formation (high temperature and high WHSV, i.e., 350 °C and 24,000 mLN,CO2·g−1·h−1, respectively), but at 300 °C and low WHSV, excellent activity (ca. 90% of CO2 conversion) and stability, with nearly complete selectivity towards methane, were obtained.

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38

Shi, Wenbo, Xiaolong Liu, Junlin Zeng, Jian Wang, Yaodong Wei e Tingyu Zhu. "Gas-solid catalytic reactions over ruthenium-based catalysts". Chinese Journal of Catalysis 37, n. 8 (agosto 2016): 1181–92. http://dx.doi.org/10.1016/s1872-2067(15)61124-x.

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39

Smit, Wietse, Vitali Koudriavtsev, Giovanni Occhipinti, Karl W. Törnroos e Vidar R. Jensen. "Phosphine-Based Z-Selective Ruthenium Olefin Metathesis Catalysts". Organometallics 35, n. 11 (18 maggio 2016): 1825–37. http://dx.doi.org/10.1021/acs.organomet.6b00214.

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40

Lozano-Vila, Ana M., Stijn Monsaert, Agata Bajek e Francis Verpoort. "Ruthenium-Based Olefin Metathesis Catalysts Derived from Alkynes". Chemical Reviews 110, n. 8 (11 agosto 2010): 4865–909. http://dx.doi.org/10.1021/cr900346r.

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41

Vougioukalakis, Georgios C., e Robert H. Grubbs. "Ruthenium-Based Heterocyclic Carbene-Coordinated Olefin Metathesis Catalysts†". Chemical Reviews 110, n. 3 (10 marzo 2010): 1746–87. http://dx.doi.org/10.1021/cr9002424.

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42

Tijani, Amina, Bernard Coq e François Figueras. "Hydrogenation ofpara-chloronitrobenzene over supported ruthenium-based catalysts". Applied Catalysis 76, n. 2 (settembre 1991): 255–66. http://dx.doi.org/10.1016/0166-9834(91)80051-w.

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43

KHAN, F., e N. SAHU. "Highly efficient and recyclable ruthenium-based supported catalysts". Journal of Catalysis 231, n. 2 (25 aprile 2005): 438–42. http://dx.doi.org/10.1016/j.jcat.2005.02.001.

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44

Harvey, Timothy G., Trevor W. Matheson, Kerry C. Pratt e Mark S. Stanborought. "Hydroprocessing of shale oil using ruthenium-based catalysts". Fuel 66, n. 6 (giugno 1987): 766–70. http://dx.doi.org/10.1016/0016-2361(87)90121-9.

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45

Dinger, Maarten B, e Johannes C Mol. "High Turnover Numbers with Ruthenium-Based Metathesis Catalysts". Advanced Synthesis & Catalysis 344, n. 6-7 (agosto 2002): 671. http://dx.doi.org/10.1002/1615-4169(200208)344:6/7<671::aid-adsc671>3.0.co;2-g.

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46

Gil-Sepulcre, Marcos, Michael Böhler, Mauro Schilling, Fernando Bozoglian, Cyril Bachmann, Dominik Scherrer, Thomas Fox et al. "Ruthenium Water Oxidation Catalysts based on Pentapyridyl Ligands". ChemSusChem 10, n. 22 (14 novembre 2017): 4517–25. http://dx.doi.org/10.1002/cssc.201701747.

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47

Shultz, Lorianne R., Corbin Feit, Jordan Stanberry, Zhengning Gao, Shaohua Xie, Vasileios A. Anagnostopoulos, Fudong Liu, Parag Banerjee e Titel Jurca. "Ultralow Loading Ruthenium on Alumina Monoliths for Facile, Highly Recyclable Reduction of p-Nitrophenol". Catalysts 11, n. 2 (25 gennaio 2021): 165. http://dx.doi.org/10.3390/catal11020165.

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The pervasive use of toxic nitroaromatics in industrial processes and their prevalence in industrial effluent has motivated the development of remediation strategies, among which is their catalytic reduction to the less toxic and synthetically useful aniline derivatives. While this area of research has a rich history with innumerable examples of active catalysts, the majority of systems rely on expensive precious metals and are submicron- or even a few-nanometer-sized colloidal particles. Such systems provide invaluable academic insight but are unsuitable for practical application. Herein, we report the fabrication of catalysts based on ultralow loading of the semiprecious metal ruthenium on 2–4 mm diameter spherical alumina monoliths. Ruthenium loading is achieved by atomic layer deposition (ALD) and catalytic activity is benchmarked using the ubiquitous para-nitrophenol, NaBH4 aqueous reduction protocol. Recyclability testing points to a very robust catalyst system with intrinsic ease of handling.

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48

Orlando, Antonio, Fiorella Lucarini, Elisabetta Benazzi, Federico Droghetti, Albert Ruggi e Mirco Natali. "Rethinking Electronic Effects in Photochemical Hydrogen Evolution Using CuInS2@ZnS Quantum Dots Sensitizers". Molecules 27, n. 23 (27 novembre 2022): 8277. http://dx.doi.org/10.3390/molecules27238277.

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Molecular catalysts based on coordination complexes for the generation of hydrogen via photochemical water splitting exhibit a large versatility and tunability of the catalytic properties through chemical functionalization. In the present work, we report on light-driven hydrogen production in an aqueous solution using a series of cobalt polypyridine complexes as hydrogen evolving catalysts (HECs) in combination with CuInS2@ZnS quantum dots (QDs) as sensitizers, and ascorbate as the electron donor. A peculiar trend in activity has been observed depending on the substituents present on the polypyridine ligand. This trend markedly differs from that previously recorded using [Ru(bpy)3]2+ (where bpy = 2,2’-bipyridine) as the sensitizer and can be ascribed to different kinetically limiting pathways in the photochemical reaction (viz. protonation kinetics with the ruthenium chromophore, catalyst activation via electron transfer from the QDs in the present system). Hence, this work shows how the electronic effects on light-triggered molecular catalysis are not exclusive features of the catalyst unit but depend on the whole photochemical system.

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Solodenko, Wladimir, Angelino Doppiu, René Frankfurter, Carla Vogt e Andreas Kirschning. "Silica Immobilized Hoveyda Type Pre-Catalysts: Convenient and Reusable Heterogeneous Catalysts for Batch and Flow Olefin Metathesis". Australian Journal of Chemistry 66, n. 2 (2013): 183. http://dx.doi.org/10.1071/ch12434.

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Abstract (sommario):

Two Hoveyda type ruthenium metathesis precatalysts, Umicore M51 and Umicore M71 SIMES, were immobilized on commercial silica in a simple and fast procedure through direct interaction with the support surface. These precatalysts exhibited good activity in ring-closing, cross, and enyne metathesis reactions and were stable in terms of reusability to be used for consecutive runs under both batch and flow conditions. In non-polar media, the catalytic activity of the precatalysts is truly based on a heterogeneous species, and the contamination of the products with ruthenium was very low with respect to starting catalyst (0.003–0.01 %; 0.13–0.44 ppm). If necessary, such as in solvents like toluene, the ruthenium content can easily be reduced to levels below 0.5 ppm by treatment of the crude metathesis products with the commercial scavenger QuadraSil AP or by use of an additional QuadraSil AP scavenger cartridge under flow conditions.

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Balcar, Hynek, e Jiří Čejka. "SBA-15 as a Support for Effective Olefin Metathesis Catalysts". Catalysts 9, n. 9 (2 settembre 2019): 743. http://dx.doi.org/10.3390/catal9090743.

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Abstract (sommario):

Olefin metathesis is the catalytic transformation of olefinic substrates, finding a wide range of applications in organic synthesis. The mesoporous molecular sieve Santa Barbara Amorphous (SBA-15) has proven to be an excellent support for metathesis catalysts thanks to its regular mesoporous structure, high BET area, and large pore volume. A survey of catalysts consisting of (i) molybdenum and tungsten oxides on SBA-15, and (ii) molybdenum and ruthenium organometallic complexes (Schrock and Grubbs-type carbenes) on SBA-15 is provided together with their characterization and catalytic performance in various metathesis reactions. The comparison with catalysts based on other supports demonstrates the high quality of the mesoporous molecular sieve SBA-15 as an advanced catalyst support.

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