Methane activation on supported transition metal catalysts

At present, there is considerable interest in utilizing methane more efficiently as both a fuel source and as a starting material for the production of other, more valuable products. However, methane is a very stable molecule with strong C-H bonds that are difficult to break. This makes methane combustion or the formation of carbon-carbon bonds quite difficult. The present work focuses on the use of supported transition metal catalysts as a means of activating methane (i.e. breaking C-H bonds) at low temperatures to produce valuable products or energy.; The conversion of methane into higher hydrocarbons. A low temperature ({dollar}<{dollar}750 K), direct process to effectively convert methane into higher hydrocarbons would be quite desirable. Such a process is thermodynamically feasible if the reaction is broken up into two separate steps. The first step is the adsorption of methane onto a transition metal catalyst at temperatures above about 600 K to produce a surface carbon species. The second step is a low temperature ({dollar}<{dollar}373 K) hydrogenation to convert the carbon species into higher hydrocarbons.; T. Koerts et al. have pursued this approach by dissociatively absorbing methane onto silica supported transition metal catalysts at temperatures ranging between 573 K and 773 K. The result was a surface carbonaceous species and hydrogen. In the second step, the carbonaceous intermediates produced small alkanes upon hydrogenation around 373 K. A maximum yield to higher hydrocarbons of 13% was obtained on a ruthenium catalyst.; The present study was conducted to further investigate the nature of the carbonaceous species reported by Koerts.; Methane combustion. This investigation was conducted in an effort to better understand the mechanism of methane combustion on Pd catalysts.; In the first part of this study, temperature programmed reduction (TPR) was used to investigate the oxidation and reduction dynamics of a 10 wt% Pd/ZrO{dollar}sb2{dollar} catalyst used for methane combustion. TPR experiments indicate that partial reduction of PdO with methane leads to a catalyst that is able to activate methane more readily than a catalyst that has been partially reduced with hydrogen. This suggests that reduced metal is important in activating methane.; In the second part of the study, the methane combustion activity of the catalyst was examined on partially oxidized and partially reduced catalysts. Observations suggest that the presence of Pd may enhance methane combustion activity, but only until the Pd is oxidized. (Abstract shortened by UMI.)...