In the present paper, comprehensive temperature-programmed reduction and X-ray diffraction studies were conducted, with particular emphasis on the effect of calcination temperature on the interactions between rhodium oxide and support. The formation of a compound between rhodium and support oxide is strongly dependent an the nature of the support and the calcination temperature. No such compounds were formed over gamma-Al2O3 and SiO2 supported Rh catalysts even after a calcination at a temperature as high as 950 degrees C. However, LaRhO3, MgRh2O4, YRhO3, and RhTaO4 could be formed over La2O3, MgO, Y2O3, and Ta2O5 supported catalysts after their calcination at suitable temperatures. The ease of formation of these compounds decreased in the sequence MgO > La2O3 much greater than Y2O3 greater than or equal to Ta2O5. The lower reducibilities of these compounds compared to that of Rh2O3 brought evidence of increased Rh-O bond strength. In other words, the formation of these compounds after calcination is an indication of strong interactions between rhodium and support. At a reaction temperature of 750 degrees C, La2O3 and MgO provided stable catalytic activities and selectivities during 100 h of reaction, whereas deactivation was observed over the Y2O3 and Ta2O5 supported catalysts. However, because compounds between the latter two supports and Rh2O3 could be formed at higher temperatures, reactions at higher temperatures have also been carried out. It was found that the stability of the 1 wt% Rh/Ta2O5 could be notably improved at a reaction temperature of 900 degrees C, and that the stability of the 1 wt% Rh/Y2O3 could be improved at a reaction temperature of 850 degrees C. (C) 2000 Academic Press.