Effect and mechanism of rare Earth and alkaline Earth metals on the high-temperature stability of activated alumina

Active alumina (Al 2 O 3 ) is one of the carrier materials used for the purification of automobile exhaust. The crystal transformation of active Al 2 O 3 is due to the high temperature of the automobile exhaust port, which greatly reduces the specific surface area and affects the catalytic efficiency. To improve the high-temperature stability of active Al 2 O 3 , this study synthesized Al 2 O 3 via the gel-sol method. The influence of rare Earth and alkaline Earth metal doping modification on the high-temperature stability of activated Al 2 O 3 was investigated. The specific surface areas were analyzed using Brunauer–Emmett–Teller, X-ray diffraction, Fourier-transform infrared spectroscopy, Scanning electron microscopy, and transmission electron microscopy to explore the effects and mechanism of different contents of La, Ce, and Ba on active Al 2 O 3 . The results showed that suitable single doping of La, Ce, and Ba inhibited the phase transition of Al 2 O 3 and improved the high-temperature stability of active Al 2 O 3 . When 1% of La and Ba were mixed and doped into active Al 2 O 3 , the specific surface area of the sample after aging at 1,100°C for 4 h was 119.2512 m 2 /g. X-ray diffraction analysis revealed the agglomeration of Ba atoms inside the alumina and that the incorporated La atoms accelerated the agglomeration and promoted the formation of BaAl 2 O 4 .