Polyethylene glycol-assisted synthesis of high specific surface area and pore volume γ-Al2O3 using sol-gel method

The effects of polyethylene glycol on the structural properties of gamma-alumina (γ-Al2O3) synthesized via a modified sol-gel process was investigated. For this purpose, polyethylene glycol (PEG) and aluminum isopropoxide (Al(OPri)) were used as the structure directing agent and aluminum precursor, respectively. Nitrogen adsorption-desorption analysis was performed to obtain the specific surface area, pore volume, and pore size distributions of the γ-Al2O3 samples synthesized with different mole ratios of PEG/Al(OPri). The maximum specific surface area (344 m2/g) and the pore volume (2.2 cm3/g) was obtained for the γ-Al2O3 prepared with a PEG/Al(OPri) mole ratio of 0.05. These surface area and pore volume are about 40 and 340% higher than the sample synthesized in the absence of PEG. It was also observed that increasing the mole ratio of PEG/Al(OPri) to more than 0.05, has no significant effect on the structure of γ-Al2O3. The best sample was further studied by scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses and the results were compared with the commercial γ-Al2O3 prepared from Merck Company with specific surface area and pore volume of 174 m2/g and 0.5 cm3/g, respectively. The crystallite sizes of the best synthesized sample and Merck product were calculated 7 and 13 nm, respectively.