Carbon oxidation activity of complex oxides (Part 3)—Low temperature carbon combustion characteristics of (Bi₂O₃)_0.97(RE₂O₃)_0.03 (RE: rare earth)—

Abstract

The utilization of Bi₂O₃ heat-treated at 700 °C lowered the combustion temperature of 660 °C for carbon alone to 414 °C in the tight contact state. Owing its exceptional carbon combustion capacities, the carbon combustion properties of (Bi₂O₃)_1−x(RE₂O₃)_x, a solid solution of rare earth oxides in Bi₂O₃ heat treated at 700 °C, (Bi₂O₃)_1−x(Y₂O₃)_x, and (Bi₂O₃)_1−x(La₂O₃)_x, exhibited lower carbon combustion temperatures than Bi₂O₃ below x = 0.10. Lower carbon combustion temperatures were observed for Y₂O₃ solid solution at 380 °C for x = 0.01 and 0.02 and for La₂O₃ solid solution at 383 °C for x = 0.02 and 0.03. In addition, (Bi₂O₃)_0.97(RE₂O₃)_0.03 (RE = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Tm, Yb, Lu, and Sc) exhibited lower carbon combustion temperature than Bi₂O₃ in solid solution. The carbon combustion temperatures of (Bi₂O₃)_0.97(RE₂O₃)_0.03 decreased with an increase in the ionic radius of RE³⁺. In the loose contact state, the carbon combustion temperature of Bi₂O₃ was 558 °C, and the carbon combustion temperature of (Bi₂O₃)_0.97(RE₂O₃)_0.03 was higher than that in the tight contact state.