Novel synthesis of high-surface-area alumina using toluene-dimethylformamide as synthetic media

Abstract

Alumina support with high surface area was synthesized with a simple mixed solvent system of toluene-dimethylformamide (DMF) as synthetic media and aluminum tri-sec-butoxide/aluminum isopropoxide as aluminum precursors at an optimal Toluene/DMF volume ratio of 0.4. The specific surface area (SBET) of the alumina support prepared was about 1000 m2/g after vacuum drying at 200 °C for 4 h. It was found that these alumina supports were converted into α-Al2O3 at 1100–1200 °C with surface areas ranging from 100 to 160 m2/g. Two consecutive changes in alumina texture were observed during the alumina phase transformations, 1) Small mesoporous alumina with a pore size < 8 nm at the calcination temperature of 200 °C (SBET =1000 m2/g) can be obtained, 2) Large mesoporous alumina support with uniform pore sizes of 10–20 nm at over 1000 °C can be formed using the same fresh starting material. Based on the results, the simultaneous hydrolysis and condensation of the alkoxides and careful slow drying of the alumina in the toluene-DMF system were largely contributed to the preparation of high surface areas of alumina by forming a uniform film without any crack. The supports were characterized using different methods, including Brunauer-Emmett-Teller (BET), and X-ray powder diffraction (XRD), and scanning electron microscope (SEM). Furthermore, the performance of prepared supports was investigated in the chemical looping combustion (CLC) process using CuO-based oxygen carrier (OC).