Supported ionic liquid phase (SILP) catalysis enables a highly efficient, Ru‐based, homogeneously catalyzed water‐gas shift reaction (WGSR) between 100 °C and 150 °C. The active Ru‐complexes have been found to exist in imidazolium chloride melts under operating conditions in a dynamic equilibrium, which is dominated by the [Ru(CO)3Cl3]− complex. Herein we present state‐of‐the‐art theoretical calculations to elucidate the reaction mechanism in more detail. We show that the mechanism includes the intermediate formation and degradation of hydrogen chloride, which effectively reduces the high barrier for the formation of the requisite dihydrogen complex. The hypothesis that the rate‐limiting step involves water is supported by using D2O in continuous catalytic WGSR experiments. The resulting mechanism constitutes a highly competitive alternative to earlier reported generic routes involving nucleophilic addition of hydroxide in the gas phase and in solution.
Comparison between phosphine and NHC-modified Pd catalysts in the telomerization of butadiene with methanol ndash a kinetic study combined with model-based experimental analysis, Chemical Engineering and Processing http://dx.doi.org/10. 1016/j.cep.2015.07.007 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Comparison between phosphine and NHC-modified Pd catalysts in the telomerization of butadiene with methanol -a kinetic study combined with model-based experimental analysis The telomerization of butadiene with methanol was investigated in the presence of different palladium catalysts modified either with triphenylphosphine (TPP) or 1,3-dimesityl-imidazol-2-ylidene (IMes) ligand. When pure butadiene was used as substrate, a moderate selectivity for the Pd-TPP catalyst toward the desired product 1-methoxy-2,7-octadiene (1-Mode) of around 87 % was obtained, while the IMes carbene ligand almost exclusively formed 1-Mode with 97.5 % selectivity. The selectivity remained unchanged when the pure butadiene feed was replaced by synthetic crack-C 4 (sCC 4 ), a technical feed of 45 mol % butadiene and 55 mol % inerts (butenes and butanes). The TPP-modified catalyst showed a lower reaction rate, which was attributed to the expected dilution effect caused by the inerts. Surprisingly, the IMes-modified catalyst showed a higher rate with sCC 4 compared to the pure feed. By means of a model-based experimental analysis, kinetic rate equations could be derived. The kinetic modeling supports the assumption that the two catalyst systems follow different kinetic rate equations. For the Pd-TPP catalyst, the reaction kinetics were related to the Jolly mechanism. In contrast, the Jolly mechanism had to be adapted for the Pd-IMes catalyst as the impact of the base seems to differ strongly from that for the Pd-TPP catalyst. The Pd-IMes system was found to be zero order in butadiene at moderate to high butadiene concentrations and first order in base while the nucleophilicity of the base is influenced by the methanol amount resulting in a negative reaction order for methanol.
Supported ionic liquid phase (SILP) catalysis enables a highly efficient, Ru‐based, homogeneously catalyzed water‐gas shift reaction (WGSR) between 100 °C and 150 °C. The active Ru‐complexes have been found to exist in imidazolium chloride melts under operating conditions in a dynamic equilibrium, which is dominated by the [Ru(CO)3Cl3]− complex. Herein we present state‐of‐the‐art theoretical calculations to elucidate the reaction mechanism in more detail. We show that the mechanism includes the intermediate formation and degradation of hydrogen chloride, which effectively reduces the high barrier for the formation of the requisite dihydrogen complex. The hypothesis that the rate‐limiting step involves water is supported by using D2O in continuous catalytic WGSR experiments. The resulting mechanism constitutes a highly competitive alternative to earlier reported generic routes involving nucleophilic addition of hydroxide in the gas phase and in solution.
Supported ionic liquid phase (SILP) catalysis enables ahighly efficient, Ru-based, homogeneously catalyzed water-gas shift reaction (WGSR) between 100 8 8Ca nd 150 8 8C. The active Ru-complexes have been found to exist in imidazolium chloride melts under operating conditions in adynamic equilibrium, whichi sd ominated by the [Ru(CO) 3 Cl 3 ] À complex. Herein we present state-of-the-art theoretical calculations to elucidate the reaction mechanism in more detail. We show that the mechanism includes the intermediate formation and degradation of hydrogen chloride,w hich effectively reduces the high barrier for the formation of the requisite dihydrogen complex. The hypothesis that the rate-limiting step involves water is supported by using D 2 Oincontinuous catalytic WGSR experiments.T he resulting mechanism constitutes ah ighly competitive alternative to earlier reported generic routes involving nucleophilic addition of hydroxide in the gas phase and in solution.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.
The production of H2 gas can be achieved at low temperatures using ruthenium‐based catalysts for the water–gas shift reaction (WGSR). Using a combined theoretical and experimental approach, D. M. Smith and co‐workers present in their Communication on page 741 ff. a new mechanism for the WGSR, involving anionic, Cl‐rich, Ru carbonyl complexes. The new understanding, which is supported by kinetic isotope effects, is a step towards large‐scale industrial production of H2 at low temperatures.
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