Harold E. Swift
Bio: Harold E. Swift is an academic researcher. The author has contributed to research in topics: Catalysis & Electron nuclear double resonance. The author has an hindex of 10, co-authored 19 publications receiving 199 citations.
TL;DR: In this article, a nickel-to-tin molar ratio of 2.5:1 was obtained for cyclohexanone with a catalytic phase supported by a supported nickel-tin phase.
Abstract: Addition of tin to a nickel-silica catalyst greatly promotes the activity and gives a longer catalyst life for the dehydrogenation of cyclohexanone and/or cyclohexanol to phenol. Outstanding results are obtained with a catalyst having a nickel-to-tin molar ratio of 2.5:1. Reduction of the nickel-to-tin molar ratio to 0.9:1 gives very little dehydrogenation of cyclohexanone; however, a new reaction takes place, which is the aldolization of cyclohexanone to 2-(1-cyclohexenyl)cyclohexanone. An explanation of the promoting effect of tin and the change in reaction selectivity with nickel-to-tin ratio is given. An investigation of the reduced nickel-tin-silica catalysts by X-ray diffraction has revealed the presence of a supported nickel-tin alloy phase.
TL;DR: In this paper, it was shown that at low viscosities the linewidth was proportional to the viscosity times the cube of the molecular radius, and it was believed that the dominant relaxation mechanism is quadrupolar relaxation through molecular rotation.
Abstract: The compounds triethylaluminum, tri‐n‐propylaluminum, tri‐n‐butylaluminum, and tri‐n‐hexylaluminum were studied by nuclear magnetic resonance both in the pure state and in the solvents isopentane, n‐hexane, cyclohexane, and hexadecane. At low viscosities the linewidth was proportional to the viscosity times the cube of the molecular radius, and it is believed that the dominant relaxation mechanism is quadrupolar relaxation through molecular rotation. In high‐viscosity solvents this mechanism becomes unimportant. A mixture of aluminum alkyls produces a single Lorentzian shaped resonance which arises from rapid alkyl interchange.
TL;DR: In this paper, the number of surface atoms at the surface of a metal crystal can be differentiated according to the number (j) and arrangement of their nearest neighbours in the crystal.
Abstract: The atoms at the surface of a metal crystal can be differentiated according to the number (j) and arrangement of their nearest neighbours. We have determined how, in (different) crystals with f.c.c., b.c.c. and h.c.p. structures, the total number of surface atoms (Ns) and the proportions of the various types of surface atoms N(C j ) N s depend on the crystallite size. In some cases we have also determined how the number of Bni,j,k,… sites varies with the crystallite size, a Bni,j,k,… site being defined as an ensemble of n surface metal atoms in a certain specified arrangement where the n surface metal atoms have i,j,k etc. nearest neighbours. On the basis of the results we have considered the influence of crystallite size on the sorptive and catalytic behaviour of metal catalysts.
TL;DR: In this paper, a study of the chemistry involved in preparation, pretreatment, and reduction of Ni Al 2 O 3 catalysts was carried out using hydrogen chemisorption, thermal gravimetric analysis, and chromatographic analysis.
Abstract: A study of the chemistry involved in preparation, pretreatment, and reduction of Ni Al 2 O 3 catalysts was carried out using hydrogen chemisorption, thermal gravimetric analysis, and chromatographic analysis. Data showing effects on nickel surface area of calcination, heating rate during reduction, nickel loading, and passivation are presented and discussed. The results indicate that controlled decomposition of alumina-supported nickel nitrate in hydrogen atmosphere (without prior calcination) tends to maximize nickel surface area, dispersion, and reduction to nickel metal. Nickel surface area and the fraction of nickel reduced to the metallic state both increase as the hydrogen space velocity during reduction is increased. Upon increasing the reduction temperature from 300 to 500 °C, the percentage reduction to nickel metal is increased from 40 to 100% whereas nickel surface area changes relatively little.
TL;DR: In this paper, the reduction characteristics of various copper, nickel, and copper-nickel-on-silica catalysts have been examined using a temperature-programmed technique, which involves a continuous and quantitative monitoring of the hydrogen uptake due to the reduction of a particular species on the catalyst surface.
Abstract: As part of a study of bimetallic alloying on a support, the reduction characteristics of various copper-, nickel-, and copper-nickel-on-silica catalysts have been examined. The method used for this study, a temperature-programmed technique, involves a continuous and quantitative monitoring of the hydrogen uptake due to the reduction of a particular species on the catalyst surface. Irrespective of whether the bimetallic catalysts (in nitrate form) are or are not precalcined, both copper and nickel exist in the zero-valent metal state and are engaged in alloying after a hydrogen treatment at 500 °C. The precalcination history of the bimetallic catalysts and the relative metal loadings of such preparations have a marked influence on the manner in which the two metals are reduced. Some possible causes for these findings and the potentialities of the temperature-programmed reduction technique are discussed.