TPR and FT-IR studies on carbonyl cluster derived Co [sbnd]Rh/SiO 2 catalysts

Abstract

The decarbonylation of Co 4−nRh n(CO) 12/SiO 2 and (Co 4(CO) 12 +Rh 4(CO) 12)/SiO 2 catalysts was studied by temperature programmed reduction (TPR) and in-situ diffuse reflectance FT-IR techniques. Special attention was paid to the effect of the decomposition atmosphere on the supported catalysts. The temperature of decarbonylation depended on the precursor, and the CO desorption peak maxima during the TPR were as follows: Co 2Rh 2(CO) 12 = 123°C, Co 3Rh(CO) 12 = 125°C, (Co 4(CO) 12 + Rh 4(CO) 12) = 135°C, Co 4(CO) 12 = 137°C and Rh 4(CO) 12 = 178°C. The CO desorption was greatest for Co 4(CO) 12, and less and similar for other catalysts. Thus, from rhodium containing catalysts less CO was desorbed at elevated temperatures indicating a stronger interaction of rhodium than of cobalt with the support. Correspondingly, according to FT-IR measurements, the stability of the tetranuclear carbonyls supported on silica decreased in the order Co 4(CO) 12 > bimetallic carbonyls > Rh 4(CO) 12 at room temperature.