Porous Alumina Prepared from Diethylaluminum Amide, Acetone, and Water

Abstract

A previously described synthetic method was modified to improve the porosity of the alumina product. The compound (Et2AlNH2)3 was prepared from ammonia and triethylaluminum (Et3Al) in toluene solvent. Addition of acetone to form a solution of ethylaluminoxane (EtAlO) and acetonine (2,2,4,4,6-pentamethyl-2,3,4,5-tetrahydropyrimidine) was followed by addition of two equivalents of water to give an alumina precursor. Alumina precursors also were prepared by the direct hydrolysis of (Et2AlNH2)3. Powder X-ray diffraction, 27Al MAS NMR, and N2 adsorption/desorption isotherms were used to analyze the aluminas after calcination of the precipitates. The aluminas exhibited high pore volume and surface area, and they were amorphous after calcination at 500 °C. One alumina showed a significant fraction of pentacoordinate aluminum after heating to 300 °C in air or 500 °C in steam atmosphere. The products crystallized as α-Al2O3 at the low temperature of 1000 °C, which reduces their applicability for catalysts. Synthesis variables and their effects on alumina properties are discussed.

Effects of Alkaline Earth Metal on Performance of ZrO₂-Al₂O₃ Support and Pd-Rh Close-Coupled Catalyst

“…Researches showed that introducing alkali metals, alkaline earth metals, and rare earth elements can increase the thermal stability and surface area of alumina. [5][6][7][8][9] The alkaline earth metals which can stabilize Al2O3 are Ba 2 + , Sr 2 + , and Ca 2 + . 10 Ba 2 + is the best.…”

Effect of Ce_0.45Zr_0.45Y_0.07La_0.03O_1.95/La-Ba-Al₂O₃ Mass Ratio on the Activity of Fe-Based Monolithic Catalysts for the Combustion of Thin Methane

“…However, doping γ-Al2O3 with alkali, alkalineearth, and rare-earth metals can increase the thermal stability and suppress the decrease in specific surface area of the catalysts. [14][15][16] Another common Fe2O3 catalyst support is CeO2-ZrO2 oxygen storage material, which is widely used in the three-way catalysts of gasoline vehicles. CeO2-ZrO2 solid solutions not only disperse the active components but also improve the catalytic activity, owing to their oxygen storage capability.…”

Supercritical preparation of hexagonal γ-alumina nanosheets and its electrocatalytic properties

“…One efficient way to minimize stress is the supercritical fluid drying [21,22]. In a typical sol-gel approach, aluminum alkoxides [23][24][25], such as aluminum isopropoxide or aluminum sec-butoxide [26][27][28][29], are usually sources of alumina aerogels [30][31][32][33]. However, these aluminum alkoxides are very reactive, which makes sol-gel formation hard to control.…”