Zeolite Rho Loaded with Methylamines. I. Monomethylamine Loadings

Samples of two differently prepared zeolite rho loaded with different amounts of monomethylamine (MMA) were studied in their hydrated and dehydrated forms by X-ray and neutron diffraction. Both zeolites are partially dealuminated, as indicated by nonframework alumina, which is assumed to be Al2O3 or AlOOH. Series I was prepared from dry-calcined NH4-rho at 873 K, series II from steam-calcined NH4-rho at 773 K. The samples were loaded with different amounts of deuterated MMA, Rietveld refinements yielded the following results for series I (dry): (1) H3.8(H-MMA)5Cs0.2Al9Si39O2.Al2O3.28H2O, X-ray data collection at room temperature, Im3̅m, a = 14.9991 (2) Å, Rwp = 0.095; (2) composition as in (1), anhydrous and deuterated, neutron data collected at 5 K, disproportionation into two phases in I4̄3m, with a = 14.8410 (7) and 14.5273 (11) Å, Rwp = 0.038; (3) (H-MMA)8.8Cs0.2Al9Si39O96.Al2O3.25H2O, X-ray data collection at room temperature, I4̄3m, a = 14.9771 (2) Å, Rwp = 0.090. Series II (steam): (4) H0.3(H-MMA)5Cs0.7Al6Si42O96.2.5Al2O3.23H2O, X-ray data collected at room temperature, Im3̅m, a = 15.0323 (2) Å, Rwp = 0.124; (5) composition as in (4), anhydrous and deuterated, neutron data collected at 5 K, disproportionation into two phases in I4̄3m with a = 14.9151 (2) and 14.6475(8) Å, Rwp = 0.031. In the hydrated samples MMA resides on the center axis in the α-cage with the N atoms pointing to the single eight-ring; upon dehydration it migrates into the double eight-rings

Electronic Structure of the Complex Hydride NaAlH4

Density functional calculations of the electronic structure of the complex hydride NaAlH4 and the reference systems NaH and AlH3 are reported. We find a substantially ionic electronic structure for NaAlH4, which emphasizes the importance of solid state effects in this material. The relaxed hydrogen positions in NaAlH4 are in good agreement with recent experiment. The electronic structure of AlH3 is also ionic. Implications for the binding of complex hydrides are discussed.Comment: 4 pages, 5 figure

Selective Hydrogenation of Benzofurans Using Ruthenium Nanoparticles in Lewis Acid-Modified Ruthenium-Supported Ionic Liquid Phases

Ruthenium nanoparticles immobilized on a Lewis-acid-functionalized supported ionic liquid phase (Ru@SILP-LA) act as effective catalysts for the selective hydrogenation of benzofuran derivatives to dihydrobenzofurans. The individual components (nanoparticles, chlorozincate-based Lewis-acid, ionic liquid, support) of the catalytic system are assembled using a molecular approach to bring metal and acid sites in close contact on the support material, allowing the hydrogenation of O-containing heteroaromatic rings while keeping the aromaticity of C6-rings intact. The chlorozincate species were identified to be predominantly [ZnCl4]2– anions using X-ray photoelectron spectroscopy and are in close interaction with the metal nanoparticles. The Ru@SILP-[ZnCl4]2– catalyst exhibited high activity, selectivity, and stability for the catalytic hydrogenation of a variety of substituted benzofurans, providing easy access to biologically relevant dihydrobenzofuran motifs under continuous flow conditions

Zeolite Rho Loaded with Methylamines. II. Dimethylamine Loadings

Samples of two differently prepared zeolite rho loaded with different amounts of dimethylamine (DMA) were studied in their hydrated forms by X-ray diffraction. Both zeolites are partially dealuminated, as indicated by nonframework A1 which is assumed to be Al2O3 or AlOOH. Series I was prepared from dry-calcined NHn-rho at 873 K, series II from steam-calcined NHn-rho at 773 K. The samples were loaded with different amounts of DMA. Rietveld refinements yielded the following results for series I: (1) H3.8(H-DMA)5Cs0.2Al9Si39O96.Al2O3.21H2O, X-ray data collection at room temperature, Im3̅m, a = 15.0590 (2) Å, Rwp = 0.089; (2) (H-DMA)8.8Cs0.2Al9Si39O96.Al2O3.18H2O, X-ray data collection at room temperature, Im3̅m, a = 15.0680 (2) Å, Rwp = 0.091. Series II: (3) H0.3(H-DMA)5Cs0.7Al6Si42O96.2.5Al2O3.24H2O, X-ray data collection at room temperature, Im3̅m, a = 15.0596 (2) Å, Rwp = 0.120. DMA resides on the center axis through the α-cage with the N atoms pointing to the single eight-ring and the two methyl groups oriented towards the center of the α-cage

Oxidation of Bioethanol using Zeolite-Encapsulated Gold Nanoparticles

With the ongoing developments in biomass conversion, the oxidation of bioethanol to acetaldehyde may become a favorable and green alternative to the preparation from ethylene. Here, a simple and effective method to encapsulate gold nanoparticles in zeolite silicalite‐1 is reported and their high activity and selectivity for the catalytic gas‐phase oxidation of ethanol are demonstrated. The zeolites are modified by a recrystallization process, which creates intraparticle voids and mesopores that facilitate the formation of small and disperse nanoparticles upon simple impregnation. The individual zeolite crystals comprise a broad range of mesopores and contain up to several hundred gold nanoparticles with a diameter of 2–3 nm that are distributed inside the zeolites rather than on the outer surface. The encapsulated nanoparticles have good stability and result in 50 % conversion of ethanol with 98 % selectivity toward acetaldehyde at 200 °C, which (under the given reaction conditions) corresponds to 606 mol acetaldehyde/mol Au hour−1

Hydrogen storage in liquid hydrogen carriers: recent activities and new trends

Efficient storage of hydrogen is one of the biggest challenges towards a potential hydrogen economy. Hydrogen storage in liquid carriers is an attractive alternative to compression or liquefaction at low temperatures. Liquid carriers can be stored cost-effectively and transportation and distribution can be integrated into existing infrastructures. The development of efficient liquid carriers is part of the work of the International Energy Agency Task 40: Hydrogen-Based Energy Storage. Here, we report the state-of-the-art for ammonia and closed CO2-cycle methanol-based storage options as well for liquid organic hydrogen carriers

Materials for hydrogen-based energy storage - past, recent progress and future outlook

Globally, the accelerating use of renewable energy sources, enabled by increased efficiencies and reduced costs, and driven by the need to mitigate the effects of climate change, has significantly increased research in the areas of renewable energy production, storage, distribution and end-use. Central to this discussion is the use of hydrogen, as a clean, efficient energy vector for energy storage. This review, by experts of Task 32, “Hydrogen-based Energy Storage” of the International Energy Agency, Hydrogen TCP, reports on the development over the last 6 years of hydrogen storage materials, methods and techniques, including electrochemical and thermal storage systems. An overview is given on the background to the various methods, the current state of development and the future prospects. The following areas are covered; porous materials, liquid hydrogen carriers, complex hydrides, intermetallic hydrides, electrochemical storage of energy, thermal energy storage, hydrogen energy systems and an outlook is presented for future prospects and research on hydrogen-based energy storage