1,721,014 research outputs found
Single step, solvent-free processes: examples and prospects
No full textAn outline is given of some of the options now available — and likely to be of growing importance — for various of ways in which inorganic catalysts may be developed to effect industrially important chemical reactions in environmentally more acceptable means. One major goal is to devise ways of producing in situ (within the sphere of reaction) aggressive oxidants especially those that are environmentally hazardous. Two specific examples are cited: 1) one involves hydroxylamine, generated in a benign fashion, so as to effect the ammoximation of cyclohexanone to its oxime and -caprolactam; 2) the other involves the Baeyer—Villiger reaction (for converting cyclic ketones to lactones) via perbenzoic acid. The role of supported bimetallic catalysts in solvent-free hydrogenations (especially of polyenes) is also highlighted
Mixed-metal clusters as precursors for nanoparticle bimetallic catalysts embedded in mesoporous silica MCM-41
No full textHigh-resolution scanning transmission electron tomography and elemental analysis of zeptogram quantities of heterogeneous catalyst
No full textThe ability to visualize the three-dimensional structure of an object is of central importance in many branches of science and engineering. Recording an angular series of two-dimensional projections (images) and subsequently applying tomographic reconstruction methods has proven to be extremely successful at many lengthscales. Using scanning transmission electron microscopy (STEM) high angle annular dark field (HAADF) imaging, we describe how the three-dimensional distribution of bimetallic nanocatalysts (such as Ru10Pt2, diameter ~1 nm, mass 10-21 g) within mesoporous hosts may be precisely determined. Moreover, the simultaneous retrieval of the elemental composition (from electron-stimulated X-ray emission spectra) of individual catalytic nanoparticles was achieved
Single-step conversion of dimethyl terephthalate into cyclohexanedimethanol with Ru5PtSn, a trimetallic nanoparticle catalyst
No full textHigh-performance nanocatalysts for single-step hydrogenations
No full textThis article discusses the usage of nanoporous silica support for anchoring bimetallic nanoparticle catalysts, which display high activity and selectivity in single-step hydrogenation reactions. Research reveals that the methodology is applicable to other solids possessing nanopores in the range of 3-30 nanometers, such as carbon nanoporous arrays for dispersing platinum nanoparticle
Single-step, highly active, and highly selective nanoparticle catalysts for the hydrogenation of key organic compounds
No full textPores for cluster catalysts: Nanoparticles of both Ru5Pt and Ru10Pt2, uniformly distributed along the inner walls of mesoporous silica, exhibit high catalytic performance in the single-step hydrogenation of dimethyl terephthalate (DMT, to 1,4-cyclohexanedimethanol (CHDM); see scheme), of benzoic acid (to cyclohexane carboxylic acid), and of naphthalene (in the presence of sulfur) to cisdecalin
Synthesis of Ru-M cluster compounds and their use as precursors for nanoparticle catalysts supported on mesoporous silica
No full textBimetallic catalysts and their relevance to the hydrogen economy
No full textThe need to develop powerful new catalysts capable of effecting reductions with molecular hydrogen under mild conditions is a pressing one, particularly with the looming importance of the hydrogen economy. We show that nanoparticle (1-1.5-nm diameter) supported bimetallic catalysts, such as Ru-Pd, Ru-Pt, and Ru-Sn, prepared by decarbonylation without skeletal disintegration of precursor, mixed-metal carbonylates, exhibit high performances in a number of reactions likely to be of considerable future industrial relevance. We also show that certain types of anchored, chiral organometallic moieties, constrained within the cavities of mesoporous silica, function as good enantioselective hydrogenation catalysts for the generation of industrially important organic products such as adipic acid and cyclohexane carboxylic acid
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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