In this study, we propose a time- and energy-saving method using biodegradable gelatin as a green template and a low-toxicity inorganic aluminum salt (Al(NO3)3·9H2O) as a low-cost aluminum source for the preparation of mesoporous alumina (γ-Al2O3). The effects of pH (pH 8.0–10.0), gelatin to aluminum source ratio (0–1.9), and the hydrothermal treatment time (0–72 h) are thoroughly explored. The gelatin can assemble with the aluminum species γ-AlOOH via hydrogen bonding to prevent the self-condensation of the γ-AlOOH during the hydrothermal treatment. Distinctly, the mesoporous γ-Al2O3 was obtained from the calcination of the resulting gelatin–γ-AlOOH composites. Without gelatin, high-crystallinity γ-AlOOH formed after the hydrothermal treatment, which transformed into the nonporous γ-Al2O3 with a small surface area (20 m2/g). Finally, it was found that with a gelatin/aluminum ratio of 0.81, reaction pH value of 8.0, and hydrothermal treatment time of 24 h, high-surface-area mesoporous γ-Al2O3 (262 m2/g) with pore diameter of 6.3 nm could be synthesized.
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