Mesoporous γ-alumina synthesized by hydro-carboxylic acid as structure-directing agent

A facile and non-surfactant-templating route is described for preparing mesoporous γ-aluminas with improved textural properties. In this synthesis, hydro-carboxylic acid (HCA) was used as the structure-directing agent and boehmite sol as the precursor. By drying the mixture of HCA and boehmite sol at a suitable temperature and then calcining at 773 K, the mesoporous γ-alumina with controllable pore structures could be obtained. The drying temperature of the initial boehmite–HCA mixture had an important effect on the pore structure of the final product. As the drying temperature increased successively from 303 K to 373 K and 423 K, the products changed correspondingly from a bimodal mesoporous structure to a uniform mesostructure and a micro–mesoporous structure. By means of various characterization techniques, including N2 physical adsorption, TEM, SEM, XRD, 27Al NMR, FTIR and TG–DTA, it was demonstrated that the coordination between HCA and aluminum became stronger with the increase of the drying temperature, so that the strong coordination interaction between the HCA and the boehmite colloid particulates could induce a kind of arrangement of rigid boehmite “building blocks”, thus giving rise to different pore structures.