TEMPERATURE PROGRAMMED DECOMPOSITION, METHANATION, AND FISCHER-TROPSCH STUDIES WITH SUPPORTED RUTHENIUM CARBONYL CLUSTER COMPLEXES.

摘要

In order to determine if catalytic activity and selectivity is dependent on the structure of the compound used to prepare a catalyst, the interaction of various ruthenium carbonyl cluster complexes with a silica support and the resulting catalytic activity were determined by Temperature Programmed Decomposition (TPD), methanation, and Fischer-Tropsch studies.; Linearly programming the temperature of Cab-O-Sil supported ruthenium carbonyl cluster complexes under helium flow resulted in CO loss in the region 395-510 K with thermal stabilities following the order Ru(,3)(CO)(,12) > H(,4)Ru(,4)(CO)(,12) > {lcub}NEt(,4){rcub}{lcub}H(,3)Ru(,4)(CO)(,12){rcub}. The formation of a bridged oxygen species analagous to HOs(,3)(CO)(,10){lcub}OSi(C(,6)H(,5))(,3){rcub} was proposed as an intermediate during the TPD of Ru(,3)(CO)(,12). With H(,4)Ru(,4)(CO)(,12), H(,2) evolution slightly precedes CO evolution while partial conversion of {lcub}NEt(,4){rcub}{lcub}H(,3)Ru(,4)(CO)(,12){rcub} was observed. The ruthenium catalyzed the decomposition of {lcub}NEt(,4){rcub}('+) to C(,2)H(,4), CH(,3)CN, and traces of 1-ethylpyrrole and trans-1,2 - dicyanothylene.; Under hydrogen flow Ru(,3)(CO)(,12) was converted to H(,4)Ru(,4)(CO)(,12) and {lcub}NEt(,4){rcub}{lcub}H(,3)Ru(,4)(CO)(,12){rcub} was partially converted to H(,4)Ru(,4)(CO)(,12). The {lcub}NEt(,4){rcub}('+) was reduced to CH(,4), C(,2)H(,6), and NH(,3).; The desorption of CO was first order and activation energies calculated (107-140 kJ/mole) increase in the same order as the thermal stabilities. Hydrogen desorption from H(,4)Ru(,4) (CO)(,12) is second order and the calculated activation energy (126 kJ/mole) agrees with those calculated for CO desorption this suggesting competitive adsorption in CO/H(,2) catalytic studies.; The methanation turnover numbers for Ru(,3)(CO)(,12) and H(,4)Ru(,4)(CO)(,12) are similar ((TURN)50-70 x 10('-3)molecules CH(,4)/sec Ru site) while those for catalysts derived from the anionic ruthenium carbonyl clusters are much lower ((TURN)1-20 x 10('-3) molecules CH(,4)/sec Ru site). {lcub}NEt(,4){rcub}{lcub}H(,3)Ru(,4)(CO)(,12){rcub} supported on La(,2)O(,3) exhibited very low activity (0.01 x 10('-3) molecules Cg(,4)/sec(.)Ru site.; Fischer-Tropsch product selectivities were very similar for both neutral and anionic clusters supported on Cab-O-Sil but catalysts derived from {lcub}Ho(Cp)(,2){rcub}{lcub}H(,3)Ru(,4)(CO)(,12){rcub}/ Cab-O-Sil and {lcub}NEt(,4){rcub}{lcub}H(,3)Ru(,4)(CO)(,12){rcub}/La(,2)O(,3) resulted in selectivity shifts to higher molecular weight hydrocarbons with the La(,2)O(,3) catalyst being very selective for C(,2)-C(,4) 1-olefin formation.