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Bowden, Colin; McLellan, Richard J.; Macdonald, Ronald P.; Winterbottom, John M.
doi: 10.1002/jctb.5030320502pmid: N/A
A number of Nylon‐66 fibre‐supported platinum (Pt) catalysts were prepared by refluxing solutions of ammonium chloroplatinite with Nylon‐66 fibres. The resulting Pt‐Nylon‐66 catalysts were used for the hydrogenation of 1‐octyne in n‐propanol and n‐heptane at 70°C and 1 atm. total pressure. They, like their palladium (Pd) counterparts, exhibited solvent sensitivity in respect of their selectivity for 1‐octyne production. However, both activity and selectivity trends, as metal concentration increased, were different from those exhibited by Pd‐Nylon‐66 catalysts. Pd‐Nylon‐66 catalysts gave an activity maximum, whereas Pt‐Nylon‐66 catalysts did not, activity increasing with metal concentration. Both catalysts gave constant selectivity, independent of metal concentration in n‐heptane (Pd‐Nylon‐66 = 0.99–1.00; Pt‐Nylon‐66=0.75–0.76).
Červený, Libor; Kuncová, Marcela; Vodová, Barbora; Rüžička, Vlastimil
doi: 10.1002/jctb.5030320503pmid: N/A
The effect of the amount of platinum and the type of the carrier on the selectivity for competitive hydrogenation of 2‐methyl‐3‐butene‐2‐ol and hex‐l‐ene in methanol on platinum carrier catalysts has been studied. The effect of the type of the active component and carrier on the selectivity for competitive hydrogenation of 2‐methyl‐3‐butene‐2‐ol and 2‐phenylpropene in methanol and cyclohexane on various types of catalyst has also been investigated. Selectivity decreased with increasing amounts of platinum on the carrier and also with decreasing polarity of the carrier. The change in selectivity was greatest for a change in the active (metal) component of the catalysts; being in most cases several times higher in cyclohexane compared with methanol.
Lopez‐Gonzalez, Juan De Dios; Moreno‐Castilla, Carlos; Guerrero‐Ruiz, Antonio; Rodriguez‐Reinoso, Francisco
doi: 10.1002/jctb.5030320504pmid: N/A
Several activated carbons obtained from commercial sources have been tested for their ability to remove mercuric chloride (HgCl2) from aqueous solutions. The chemical nature of the surface of the activated carbons was changed by introducing carbon‐oxygen and carbon‐sulphur surface complexes. The influence of these types of complexes on the adsorption of HgCl2 by the activated carbons has been studied. It seems that the existence of hydroquinonic, phenolic and hydrosulphide groups on the surface of the carbon reduces Hg(II) to Hg(I). However, there was an increase in the adsorption of Hg(II) when sulphide or hydrosulphide groups were present on the surface of the carbon. The effect of the pH of the solutions on HgCl2 adsorption was also studied; when the pH was changed from 1 to 7 there was an enhancement of the adsorption of HgCl2 by the activated carbons.
doi: 10.1002/jctb.5030320505pmid: N/A
The preparation and properties of sodium‐copper cyanoferrate(II) for the removal of caesium from nitric acid solution are discussed. An optimum product has been obtained by reacting cupric nitrate and sodium cyanoferrate in a volume ratio of 2.1:1. The product was heated on a boiling‐water bath for 2 h before coagulation, aged for 48–72 h and then after filtration dried below 140°C for about 4 h. The maximum surface area, measured by ‘BET’ methods, was 65 m2 g−1. The maximum caesium capacity was 1.35 m‐equiv. g−1. Heating the precipitate increased the pore size to 14.5 nm and this explains the enhanced distribution coefficient (i.e. Kd∼ 900) obtained with solutions containing Cs+ (20 parts 10−6) and 4M‐sodium nitrate in 0.1M‐nitric acid.
Bennett, B. A.; Shahbandeh, M. R.; Streat, M.
doi: 10.1002/jctb.5030320506pmid: N/A
X‐Ray diffraction patterns and Mössbauer spectra of sodium‐copper cyanoferrate(II) (NaCuFC) before and after incorporation of caesium atoms have been studied. The positions of the X‐ray reflections and the symmetry of the Mössbauer spectra suggest that NaCuFC has a cubic lattice structure which remains cubic as caesium atoms are introduced. Calculations based on the assumption that the lattice is face‐centred cubic, with high‐symmetry space group Fm3m, enable the distribution of atoms and vacancies to be estimated. In the case of iron atoms, 33 % of the corner sites are vacant in the sodium compound. The isomer shift data obtained by Mössbauer spectroscopy suggest that the sorption of caesium is not a simple ion‐exchange process. It may be regarded as ‘pseudochemisorption’ resulting from augmentation of 3d orbitals and/or the contribution from 4s bonding.
Bigot, Yves Le; Ayedi, Hacine Ferid; Delmas, Michel; Gorrichon, Jean‐Pierre; Gaset, Antoine
doi: 10.1002/jctb.5030320507pmid: N/A
The use of ion‐exchange resins for the esterification of furoic acid and 5‐nitrofuroic acid was characterised by an excellent yield and the absence of side reactions, particularly when the reaction was carried out in cyclohexane in the presence of the resin, SPC 118. The use of this solvent for such a reaction in a biphasic medium is thus reported for the first time. This procedure might therefore be considered on a larger scale.
Beretka, Julius; Crook, Douglas N.; King, George A.
doi: 10.1002/jctb.5030320508pmid: N/A
The effect of adding increasing amounts of calcium oxide (CaO) in the pH range 3–11 on the rate of hydration and physical properties of calcined by‐product gypsums from four Australian locations was examined. The results were interpreted in terms of the Ridge equation. It was found that, as pH increased by the addition of small quantities of CaO, the kinetic parameters changed greatly. In particular, the velocity constant k gradually decreased, while α0, the measure of heterogeneous nucleation, increased. In general, increases in pH resulted in longer setting times but little change in water requirement. The mechanical strength of cast by‐product gypsum increased with the addition of CaO up to about pH 7–8, then decreased in the alkaline region. Below about pH 7 the kinetics of hydration of the hemihydrates were in close accordance with the model developed by Ridge, but differed from it above pH 7–8. This may be due to poisoning of the gypsum nuclei by habit modifiers, which are present in small quantities in by‐product gypsum.
doi: 10.1002/jctb.5030320509pmid: N/A
A study has been made of the effects of calcium oxide and phosphoric acid on the hydration of calcium sulphate hemihydrate. The reaction was studied with weight ratios of CaO/P2O5 increasing from 0 to 5, and with two levels of P2O5 concentrations, 0.1 and 0.2%. At the CaO/P2O5 weight ratio of 1–2, the velocity constant (k) of the reaction was reduced significantly; α0, a measure of heterogeneous nucleation in the system increased 10 to 20‐fold and the period of induction (θ) was increased substantially. The presence of phosphoric acid alone, and secondary calcium orthosphate hydrate (CaHPO4.2H2O), formed in situ, strongly retarded the hydration of calcium sulphate hemihydrate. The implications of these findings on the hydration of calcined by‐product gypsum (phosphogypsum) are discussed.
doi: 10.1002/jctb.5030320510pmid: N/A
Quantitative 13C‐nuclear magnetic resonance has been applied to the determination of the percentage of aromatic carbon atoms (% CA) of Nahorkatia, Ankleshwar (both Indian) and Basrah (Middle‐Eastern) crude oils. From the analysis of these results it has been demonstrated that a combination of the instrumental and chemical methods (gated decoupling with a relaxation reagent added) is the only satisfactory method for the precise determination of % CA The maximum deviation in % CA due to nuclear Overhauser effect has also been estimated.
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