Die Reduktion von C6H5)3PAuCl mit B2H6 in Benzol ergibt Au9,2[P(C6H5)3]2Cl, das mittels Molmassebestimmungen als Au55[P(C6H5)3]12Cl6 charakterisiert wurde. Ein einfaches Modell, beruhend auf einer Anordnung dichtest gepackter Goldatome, führt zu einem Goldcluster, dessen Aufbau mit der ungewöhnlichen chemischen Zusammensetzung in guter Übereinstimmung ist. Das Mößbauer‐Spektrum der Verbindung zeigt vier Sorten von Goldatomen: einen metallischen Anteil (Au13‐Kern), durch P(C6H5)3‐bzw. Cl‐Liganden Koordinierte Au‐Atome, sowie unkoordi‐niertes Oberflächengold. Mit Brom und lod läß sich der Komplex zu (C6H5)3PAuCl, (C6H5)3 PAuBr(I) und metallischem Gold abbauen. Die Thermolyse bei 50°C führt quantitativ zu [(C6H5)3P]2AuCl und Gold.
The conversion of ethanol over H-ZSM-5 was studied as a function of ethanol partial pressure, reaction temperature, weight hourly space velocity and %/A1 ratio. The results obtained were in qualitative agreement with most of those in the literature. Combination with all published results to give a significant regression model was not possible due to the large scatter of the data from various scientific groups. In mechanistic investigations, temperature programmed reaction measurements of ethanol, diethyl ether and ethene were performed. The formation of ethene from ethanol via direct elimination or from diethyl ether as intermediate could be confirmed. In the conversion of ethanol/water mixtures, the product distribution did not change significantly up to a water content of 60 wt%. Then, a pronounced increase of ethene formation and a considerable decrease of the yields of, aromatics was observed. When several reaction mixtures from syngas conversion to ethanol were converted over H-ZSM-5, the coking rate depended on the product distribution in the feed. Product mixtures from processes with higher amounts of compounds having an unfavourable C/H ratio led to rapid deactivation of the zeolite.
RHF/3-21G ab initio, density functional theory (B3LYP/3-21G), and single-point calculations
using an effective core potential (B3LYP/6-31G*-ECP(S)//3-21G) are performed for different mechanisms
of polymerization of acrylic acid and methyl acrylate by dicyclopentadienyl−zirconocene enolate complexes.
Polymerization is considered involving a cationic zirconocene complex and a neutral zirconocene complex,
respectively. In addition, a mechanism proposed by Collins is treated which involves a neutral and a
cationic zirconocene complex in the CC bond-forming step at the same time. Catalytic cycles can be devised
in all cases which suggest that all three mechanisms may be realizable under suitable conditions. However,
the “bimetallic” mechanism proposed by Collins shows the lowest energy of activation for the propagation
step. It is shown that bridging of the cyclopentadienyl rings should be important not only with respect to
reactivity but also with respect to the possible catalytic cycle. Methyl methacrylate is not included in the
treatment; i.e., the problem of tacticity in these polymerizations is not addressed.
The conversion of a number of alcohols, ethers, ketones, aldehydes, carboxylic acids, esters, and cyclic compounds and their mixtures on H‐ZSM‐5 at 673 K was investigated. These compounds can be easily converted to aromatic hydrocarbons if the C/H ratio of the molecule fragment, remaining after elimination of oxygen as water, is less than 0.62. At higher C/H ratios, coking of the catalyst increases, thus reducing its lifetime, a difficulty which can be overcome by hydrogenation of these compounds prior to their conversion over H‐ZSM‐5. A procedure is proposed for converting at least a part of organic waste chemicals to valuable products instead of burning them.
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