A new alumina catalyst support with high thermal stability was synthesized. The high thermal stability was achieved through the synergetic effect of silica addition and the ultra-low bulk density (aerogel). The amount of silica was varied from 2.5 to 10 wt% and 5 wt% was found to be most effective for suppressing phase transformation; the theta phase remained even after heating at 1400 degrees C for 1 h. The surface areas of the present alumina with 5 wt% silica were 86 and 36 m(2)/g after heating at 1300 and at 1400 degrees C, respectively.