Hydrogenation of olefins and polymerization of ethene over chromium oxide/silica catalystsI. Preparation and structure of the catalyst

“…Baltanas et al [ 191 suggested that water might affect the total amount of coordinatively unsaturated sites. Furthermore, water can hydrolyse the Al-0-Mn bonds at 573 K; the hydrolysis of the metal oxide-support bond was also observed on CrO,/SiOz systems [20], resulting in clustering of the metal oxide phase. According to Kanungo [ 211 unsupported MnO, looses all physically adsorbed water below 473 K and all chemically adsorbed water and surface hydroxyls at 673 K.…”

mentioning

confidence: 97%

Inhibiting and deactivating effects of water on the selective catalytic reduction of nitric oxide with ammonia over MnO /Al2O3

Kijlstra

Daamen

Graaf

et al. 1996

Applied Catalysis B: Environmental

114

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Inhibiting and deactivating effects of water on the selective catalytic reduction (SCR) of NO with NH3 over MnOx/Al2O3 Kijlstra, W.S.; Daamen, J.C.M.L.; van de Graaf, J.M.; van der Linden, B.; Poels, E.K.; Bliek, A. Published in:Applied Catalysis B-Environmental DOI:10.1016/0926-3373(95) Link to publication Citation for published version (APA):Kijlstra, W. S., Daamen, J. C. M. L., van de Graaf, J. M., van der Linden, B., Poels, E. K., & Bliek, A. (1995). Inhibiting and deactivating effects of water on the selective catalytic reduction (SCR) of NO with NH3 over MnOx/Al2O3. Applied Catalysis B-Environmental, 7(3/4), 337-357. DOI: 10.1016/0926-3373(95)00052-6 General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. AbstractThe effect of water on the selective catalytic reduction (SCR) of nitric oxide with ammonia over alumina supported with 2-l 5 wt.-% manganese oxide was investigated in the temperature range 385-600 K, with the emphasis on the low side of this temperature window. Studies on the effect of l-5 vol.-% water vapour on the SCR reaction rate and selectivity were combined with TPD experiments to reveal the influence of water on the adsorption of the single SCR reactants. It turned out that the activity decrease due to water addition can be divided into a reversible inhibition and an irreversible deactivation. Inhibition is caused by molecular adsorption of water. TPD studies showed that water can adsorb competitively with both ammonia and nitric oxide. Additional kinetic experiments revealed that adsorbed ammonia is present in excess on the catalyst surface, even in the presence of water. Reduced nitric oxide adsorption is responsible for the observed reversible decrease in the reaction rate; the fractional reaction order changes from 0.79 in the absence of water to 1.07 in its presence. Deactivation is probably due to the dissociative adsorption of water, resulting in the formation of additional surface hydroxyls. As the amount of surface hydroxyls formed is limited to a saturation level, the deactivating effect on the catalyst is limited too. The additional hydroxyls condense and desorb in the temperature range 525-775 K, resulting in a lower degree of deactivation at higher temperature. A high temperature treatment at 775 K results in a complete regeneration....

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“…[15,16] TG-DTA analyses of CrO 3 /SiO 2 catalyst precursor (PCT110). Figures 5 and 6 show the effect of calcination temperature on the colors of these two kinds (PCA and PCT) of catalyst precursors.…”

Section: Tg-dta Characterizationmentioning

confidence: 99%

Supporting mechanism of non‐toxic chromium (III) acetate on silica for preparation of Phillips ethylene polymerization catalysts

Qiu

Zhang

et al. 2009

Asia-Pacific J Chem Eng

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Phillips catalyst is an important kind of industrial polyethylene catalyst. As early as in the late 1970s, CrO 3 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 CrO 3 on SiO 2 . 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 Cr 3 (OH) 2 (Ac) 7 /SiO 2 catalyst precursor, which would be firstly transferred into CrO 3 followed by supporting on silica surface as chromate species. The further weight loss came from thermal inductive reduction of chromate species into Cr 2 O 3 , which was also supported by the results of colors of catalysts. Moreover, with the increase of chromium loading of Cr 3 (OH) 2 (Ac) 7 /SiO 2 , such thermal inductive reduction became more severe. ESR spectra of Cr 3 (OH) 2 (Ac) 7 /SiO 2 and CrO 3 /SiO 2 catalyst precursors showed that a small amount of supported Cr 5+ can exist stably on silica gel surface at temperatures higher than 200

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Hydrogenation of olefins and polymerization of ethene over chromium oxide/silica catalystsI. Preparation and structure of the catalyst

Cited by 88 publications

References 12 publications

Olefin polymerization over supported chromium oxide catalysts

Olefin polymerization over supported chromium oxide catalysts

Inhibiting and deactivating effects of water on the selective catalytic reduction of nitric oxide with ammonia over MnO /Al2O3

Supporting mechanism of non‐toxic chromium (III) acetate on silica for preparation of Phillips ethylene polymerization catalysts

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