Fast, Large-Scale, and Stable Preparation of η-Al2O3 Microspheres by Fully Utilizing N,N-Dimethylformamide at Room Temperature

A fast, large-scale, and stable preparation method was successfully developed to obtain η-Al2O3 microspheres with particle sizes of 3–10 μm from cheap and widely sourced NaAlO2 solution using N,N-dimethylformamide (DMF) as a morphological modifier and a precipitant simultaneously at room temperature. The yield of alumina increases from 33.3 to 77.3% by increasing the dose of DMF from 100 to 400 mL. The utilization efficiency of DMF significantly increased by adding fresh NaAlO2 into the reused filtrate after separating the bayerite precipitate (precursor of η-Al2O3). Importantly, the η-Al2O3 microspheres obtained from the filtrate-reuse experiments show the stable phase structures, morphologies, and pore structure properties. Furthermore, the typical η-Al2O3 microspheres supported Pd catalyst presents a higher catalytic activity of 10.6 g/L for the hydrogenation of anthraquinone than that of the commercial γ-Al2O3-supported Pd catalyst (8.5 g/L), suggesting that the as-prepared η-Al2O3 microspheres have good application prospects for catalytic hydrogenation and related fields.