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Guerbet alcohols, a class of β-branched terminal alcohols, find widespread application because of their low melting points and excellent fluidity. Because of the limitations in the activity and selectivity of existing Guerbet catalysts, Guerbet alcohols are not currently produced via the Guerbet reaction but via hydroformylation of oil-derived alkenes followed by aldol condensation. In pursuit of a one-step synthesis of Guerbet alcohols from simple linear alcohol precursors, we show that MOF-derived RuCo alloys achieve over a million turnovers in the Guerbet reaction of 1-propanol, 1-butanol, and 1-pentanol. The active catalyst is formed in situ from ruthenium-impregnated metal-organic framework MFU-1. XPS and XAS studies indicate that the precatalyst is composed of Ru precursor trapped inside the MOF pores with no change in the oxidation state or coordination environment of Ru upon MOF incorporation. The significantly higher reactivity of Ru-impregnated MOF versus a physical mixture of Ru precursor and MOF suggests that the MOF plays an important role in templating the formation of the active catalyst and/or its stabilization. XPS reveals partial reduction of both ruthenium and MOF-derived cobalt under the Guerbet reaction conditions, and TEM/EDX imaging shows that Ru is decorated on the edges of dense nanoparticles, as well as thin nanoplates of CoOx. The use of ethanol rather than higher alcohols as a substrate results in lower turnover frequencies, and RuCo recovered from ethanol upgrading lacks nanostructures with plate-like morphology and does not exhibit Ru-enrichment on the surface and edge sites. Notably, 1H and 31P NMR studies show that through use of K3PO4 as a base promoter in the RuCo-catalyzed alcohol upgrading, the formation of carboxylate salts, a common side product in the Guerbet reaction, was effectively eliminated.

RuNi nanoparticles supported on a metal-organic framework (RuNi@MOF) and formed in situ from a ruthenium complex enclosed inside a nickel-based MOF act as a highly active catalyst for the Guerbet reaction of ethanol to 1-butanol, providing turnover numbers up to 725 000 Ru

Linear octenes were produced in high (70–85%) selectivity from oligomerization of liquid 1-butene using carbon-supported cobalt oxide catalysts in a continuous flow reactor. The liquid products were characterized by two-dimensional gas chromatography–mass spectrometry. Above 95% of the oligomers were C8 olefins, with the other products primarily being branched C12 olefins. The linear octene products at a conversion of 9.77% decreased in selectivity according to 3-octene > trans-2-octene > cis-2-octene > 4-octene. Methyl-heptenes including trans/cis-5-methyl-2-heptene > trans/cis-5-methyl-3-heptene > trans-3-methyl-2-heptene (at the lowest conversion) were the other major products summing to 15.6%. The selectivity of linear octenes decreased from 84 to 78% as the conversion increased from 10% to 29%. The product distribution suggests the reaction pathway involves a head-to-head coupling of two 1-butene molecules to form internal linear octenes. Head-to-tail coupling of two 1-butene molecules or a coupling ...

Molybdenum disulfide promoted with alkali metals is one of the most studied catalysts for the conversion of synthesis gas to alcohols. In this work, MoS2 was promoted by adding potassium precursors by physical mixing (PM) and incipient wetness impregnation (IWI) and tested in a small scale reactor. The catalysts prepared by impregnation showed poorer performance compared to the sample prepared by physical mixing of K2CO3 and MoS2. The catalysts were characterized by means of X-ray diffraction, TGA–MS, SEM–EDS, TEM and XPS. The characterization results obtained by SEM–EDS and XRD analyses do not show major differences between the catalysts studied here. In contrast, the TGA results indicated that physical mixing leads to catalysts that lose sulfur at temperatures above 330 °C and TEM images showed that randomly oriented small MoS2 crystallites are obtained from PM preparation while IWI preparation gave long MoS2 crystallites.

Barrier integrity of Ta-films deposited using the enhanced coverage by re-sputtering (EnCoRe) barrier was investigated on untreated surfaces of blanket porous SiLK semiconductor dielectric (developmental version 7, hereinafter v7). Barrier integrity of a bi-layer EnCoRe Ta(N)/Ta film was studied on single damascene lines using v7 and porous SiLK semiconductor dielectric (developmental version 9, hereinafter v9). On blanket wafers more than 30 nm barrier thickness is necessary to achieve complete pore sealing. Analysis of the sheet resistance showed that when tantalum is deposited, a low resistivity α-phase is nucleated on the low-k surface. When deposited onto single damascene structures, EnCoRe Ta(N)/Ta is successful in providing a continuous metallic barrier layer over v7 and v9 semiconductor dielectric lines.

The microstructures of YBCO/N/YBCO ramp-edge junctions have been studied by transmission electron microscopy and related to supercurrent transport properties which depend on the barrier layer N, the interfacial structures and defect structures in the multilayer epitaxial devices. Three different types of junction materials were investigated: Metallic oxide barriers, CaRuO{sub 3} and SrRuO{sub 3}; barriers isostructural to YBCO, Co-doped YBCO and Co-doped PrBa{sub 2}Cu{sub 3}O{sub 7}; and 'interface engineered' barriers, formed by plasma treatment of the YBCO ramp-edge. Metallic oxide barriers are characterized by high steps and strong variations in local barrier width. The observed topologies are consistent with an island growth mode for both CaRuO{sub 3} and SrRuO{sub 3}. The metallic oxide barriers are associated with interfacial strain fields that are believed to be the cause for interfacial oxygen depletion in YBCO and the observed excess normal-state resistance. A number of structural defects and deviations from perfect epitaxy have been observed. Most disruptive to the integrity of the multilayer structures and transport properties is the nucleation of a-axis YBCO grains at steep barrier steps and within the YBCO layers. The barrier layers in isostructural junctions are well structured with a high degree of interfacial coherence and for the most part,more » Cu-O planes are continuous across the interfaces. In contrast to heterostructured metallic oxide barriers, isostructural junctions contain few extraneous defects, such as a-axis grains at the barrier layer, moreover, the second YBCO layer is of good quality due to the perfect epitaxy between the materials. Among the junctions investigated the interface engineered junctions have shown the best electromagnetic properties. Their structure is characterized by narrow (2-3 nm) barriers that are continuous and crystalline. No significant interfacial strains and structural disorder were observed. This and a constant barrier thickness appear responsible for obtaining good uniformity of electric transport properties. The narrow pinhole-free barrier, coupled with excellent epitaxy and few defects, yields good reproducibility and a range of properties suitable for practical applications.« less

We describe the growth of amorphous carbon nanofibers (CNFs) from iron-encapsulated dendrimer catalysts at ambient temperature and pressure conditions. Both fourth-generation poly (propyleneimine) (PPI) and poly(amidoamine) (PAMAM) dendrimers were suitable macromolecular hosts for the catalytic species. Average nanofiber diameters range from 10 - 15 nm, with lengths in excess of 20 microns.