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Catalyst Properties (catalyst + property)
Selected AbstractsImproved Suzuki,Miyaura Reactions of Aryldiazonium Salts with Boronic Acids by Tuning Palladium on Charcoal Catalyst PropertiesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009François-Xavier Felpin Abstract An improved Suzuki,Miyaura cross-coupling reaction of aryldiazonium tetrafluoroborates with boronic acids catalyzed by a highly active palladium catalyst supported on charcoal is described as an extremely practical and efficient protocol. A properties-activity study of various catalysts clearly established that the optimal catalytic activity was obtained with palladium nanoparticles having a low oxidation degree and uniformly dispersed on the charcoal. The optimized reaction conditions allow the cross-coupling to proceed at room temperature without any base and ligand in technical grade methanol. Although the catalyst could not be recycled, the low palladium contamination of the solvent and product after a simple filtration of the palladium on charcoal (Pd/C) renders the present protocol competitive and safer for the environment compared to more conventional homogeneous conditions. We have highlighted the efficiency of this novel protocol by a short synthesis of the fungicide Boscalid®. [source] Statistical analysis of catalyst degradation in a semi-continuous chemical production processJOURNAL OF CHEMOMETRICS, Issue 8 2001Eleftherios Kaskavelis Abstract The effect of decaying catalyst efficacy in a commercial-scale, semi-continuous petrochemical process was investigated. The objective was to gain a better understanding of process behaviour and its effect on production rate. The process includes a three-stage reaction performed in fixed bed reactors. Each of the three reaction stages consists of a number of catalyst beds that are changed periodically to regenerate the catalyst. Product separation and reactant recycling are then performed in a series of distillation columns. In the absence of specific measurements of the catalyst properties, process operational data are used to assess catalyst decay. A number of statistical techniques were used to model production rate as a function of process operation, including information on short- and long-term catalyst decay. It was found that ridge regression, partial least squares and stepwise selection multiple linear regression yielded similar predictive models. No additional benefit was found from the application of non-linear partial least squares or Curds and Whey. Finally, through time series profiles of total daily production volume, corresponding to individual in-service cycles of the different reaction stages, short-term catalyst degradation was assessed. It was shown that by successively modelling the process as a sequence of batches corresponding to cycles of each reaction stage, considerable economic benefit could be realized by reducing the maximum cycle length in the third reaction stage. Copyright © 2001 John Wiley & Sons, Ltd. [source] Catalysis in polymeric membrane reactors: the membrane roleASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010M.G. Buonomenna Abstract Polymeric catalytic membrane reactors (PCMRs) combine a polymeric membrane that controls transfers and a catalyst that provides conversion. This review focuses on the polymeric membrane. Depending on the application, the micro-environment of the catalyst in the PCMR may be quite different from that existing in conventional reactors. This could originate different performances of the catalyst properties compared to its use without membrane. In some cases, catalysts for use in PCMR might require a specific design. In particular, the study of PCMR is a multidisciplinary activity, including material science, chemistry, and chemical engineering. Membrane based reactive separation processes, which combine two distinct functions, i.e. reaction and separation, have been around as a concept since the early stages of the membrane field itself, but have only attracted substantial technical interest during the last decade or so. Liquid phase catalytic oxidations are involved in numerous industrial processes ranging from fine to bulk chemical synthesis. PCMR polymeric membranes may also play a significant role in this field. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Supporting mechanism of non-toxic chromium (III) acetate on silica for preparation of Phillips ethylene polymerization catalystsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Pengyuan Qiu Abstract Phillips catalyst is an important kind of industrial polyethylene catalyst. As early as in the late 1970s, CrO3 was substituted by chromium (III) acetate for the preparation of Phillips catalyst on the industrial scale owing to health and environmental considerations. There is still considerable research focusing on the relations between the preparation process and catalyst properties in academics. In this work, the supporting mechanism of chromium (III) acetate on silica has been studied by Thermogravimetry,Differential Thermal Analysis (TG-DTA), and Electron Spin Resonance (ESR), in comparison with that of supporting CrO3 on SiO2. The basic chromium (III) acetate supported on high surface area silica gel decomposed differently from that for bulk basic chromium acetate when decomposition temperature was decreased by 15 °C. The decomposition temperature was 299 °C for Cr3(OH)2(Ac)7/SiO2 catalyst precursor, which would be firstly transferred into CrO3 followed by supporting on silica surface as chromate species. The further weight loss came from thermal inductive reduction of chromate species into Cr2O3, which was also supported by the results of colors of catalysts. Moreover, with the increase of chromium loading of Cr3(OH)2(Ac)7/SiO2, such thermal inductive reduction became more severe. ESR spectra of Cr3(OH)2(Ac)7/SiO2 and CrO3/SiO2 catalyst precursors showed that a small amount of supported Cr5+ can exist stably on silica gel surface at temperatures higher than 200 °C. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||