Nanosized alumina powders were prepared from Al(NO3)3·9H2O and (NH4)2CO3 through the synthesis of ammonium aluminium carbonate hydroxide (AACH) and followed by calcination. TG DTA, XRD, TEM and BET were employed ...Nanosized alumina powders were prepared from Al(NO3)3·9H2O and (NH4)2CO3 through the synthesis of ammonium aluminium carbonate hydroxide (AACH) and followed by calcination. TG DTA, XRD, TEM and BET were employed to study the process of AACH thermal decomposition and to characterize the products obtained. The results show that high purity (99.97%) and nanosized spherical α Al2O3 powders with the diameter of 40～50nm and BET surface area 32.5m2·g-1 can be obtained by calcining AACH at 1150℃for 1.5h, the sequence of phase transformation during calcination was AACH →amorphous Al2O3 →γ Al2O3 →α Al2O3, and the activation energy of AACH decomposition is (115±5)kJ·mol-1.展开更多
Aluminas were prepared by precipitation of aqueous aluminum nitrate solution using ammonium carbonate and ammonium hydroxide as precipitation agent respectively. The prepared samples were characterized by TG/DTA, XRD,...Aluminas were prepared by precipitation of aqueous aluminum nitrate solution using ammonium carbonate and ammonium hydroxide as precipitation agent respectively. The prepared samples were characterized by TG/DTA, XRD, surface area, pore volume and average pore diameter and the results were compared. The activity and stability of the close-coupled catalysts supported by aluminas prepared by different precipitating agent were compated. The alumina formed by ammonium carbonate showed larger surface area, pore volume, average pore diameter, higher thermal stability and better support property than that formed by ammonium hydroxide. The precusor of NH4Al(OH)2CO3 in the ammonium cabonate process was responsible for the difference.展开更多
文摘Nanosized alumina powders were prepared from Al(NO3)3·9H2O and (NH4)2CO3 through the synthesis of ammonium aluminium carbonate hydroxide (AACH) and followed by calcination. TG DTA, XRD, TEM and BET were employed to study the process of AACH thermal decomposition and to characterize the products obtained. The results show that high purity (99.97%) and nanosized spherical α Al2O3 powders with the diameter of 40～50nm and BET surface area 32.5m2·g-1 can be obtained by calcining AACH at 1150℃for 1.5h, the sequence of phase transformation during calcination was AACH →amorphous Al2O3 →γ Al2O3 →α Al2O3, and the activation energy of AACH decomposition is (115±5)kJ·mol-1.
文摘Aluminas were prepared by precipitation of aqueous aluminum nitrate solution using ammonium carbonate and ammonium hydroxide as precipitation agent respectively. The prepared samples were characterized by TG/DTA, XRD, surface area, pore volume and average pore diameter and the results were compared. The activity and stability of the close-coupled catalysts supported by aluminas prepared by different precipitating agent were compated. The alumina formed by ammonium carbonate showed larger surface area, pore volume, average pore diameter, higher thermal stability and better support property than that formed by ammonium hydroxide. The precusor of NH4Al(OH)2CO3 in the ammonium cabonate process was responsible for the difference.
