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Title:Heterogeneous catalytic studies with rhenium cluster-based precursors
Author(s):Lane, Philip Douglas
Doctoral Committee Chair(s):Shapley, John R.
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Inorganic
Abstract:When (Re(CO)$\sb3$OH) $\sb4$ was supported on Al$\sb2$O$\sb3$ followed by heating in H$\sb2$ no decomposition gas products, CO and CH$\sb4$, were observed below 650 K. Following the activation by infrared spectroscopy showed the formation of Re(CO)$\rm\sb3\{O$-$\rm Al\}\{HO$-Al$\}\sb2$ at 480 K. The activated sample, (Re$\sb4$) /Al$\sb2$O$\sb3$, when exposed to CO/H$\sb2$ at 298 K, produced CH$\sb4$ near 500 K with a shoulder near 600 K in the temperature programmed reaction (TPR) profile. Elevating the CO/H$\sb2$ treatment temperature to 500 K resulted in the formation of CH$\sb4$ at 560 K. The adsorption of CH$\sb3$OH or CH$\sb3$I to the sample produced CH$\sb4$ at 580 K. When (Re(CO)$\sb3$OH) $\sb4$ activated on SiO$\sb2$, only one CH$\sb4$ peak at 490 K was observed for CO/H$\sb2$ adsorption. When TiO$\sb2$ was used as a support, a spillover species was also observed from CO and H$\sb2$ exposure at 500 K. The spillover rate appeared to be slower on TiO$\sb2$ than was observed on Al$\sb2$O$\sb3$.
When both the PPN$\sp+$ and Et$\sb4$N$\sp+$ forms of (Re$\sb7$IrC(CO)$\sb{23}\rbrack\sp{2-}$ and (Re$\sb5$IrC(CO)$\sb{17}\{$Re(CO)$\sb3\}\sb2\rbrack\sp{2-}$ were supported on Al$\sb2$O$\sb3$, their decompositions were followed by TPDE and infrared spectroscopy. For the hydrogenolysis of ethane, the most and least active catalyst samples were (Re$\sb7$Ir(Et$\sb4$N)) /Al$\sb2$O$\sb3$, and (ReIr$\sb7$(PPN)) /Al$\sb2$O$\sb3$, respectively. The other two samples, (Re$\sb5$IrRe$\sb2$(Et$\sb4$N)) /Al$\sb2$O$\sb3$ and (Re$\sb5$IrRe$\sb2$(PPN)) /Al$\sb2$O$\sb3$, showed comparable activity. All samples appeared, by infrared spectroscopy, to form Re(CO)$\sb3\{$O-Al$\}\{$HO-Al$\}\sb2$ and smaller nuclearity clusters on the surface during decomposition. The amount of Re(CO)$\sb3\{$O-Al$\}\{$HO-Al$\}\sb2$ formed at 573 K correlated with the ethane hydrogenolysis activity of the resulting catalyst. The sample most active for ethane hydrogenolysis, (Re$\sb7$Ir(Et$\sb4$N)) /Al$\sb2$O$\sb3$, produced the largest amount of Re(CO)$\sb3\{$O-Al$\}\{$HO-Al$\}\sb2$during activation by 573 K, 60% of the available rhenium, and the sample least active, (Re$\sb7$IrC(CO)$\sb{23}$(PPN)) /Al$\sb2$O$\sb3$, resulted in the smallest amount, 40%. All samples produced CH$\sb4$ in the TPR profiles from the adsorption of CO in H$\sb2$.
Issue Date:1995
Rights Information:Copyright 1995 Lane, Philip Douglas
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9624405
OCLC Identifier:(UMI)AAI9624405

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