Controllable preparation of γ-alumina nanoparticles with bimodal pore size distribution in membrane dispersion microreactor

Abstract

In this paper, we present a new method for preparing γ-alumina nanoparticles with a bimodal pore size distribution by using an efficiently mixing membrane dispersion microreactor. NH4HCO3 and Al2(SO4)3∙18H2O were reacted under vigorous mixing to give an ammonium aluminum carbonate hydroxide (AACH) precursor. γ-Alumina was obtained by calcination of AACH at 550°C for 6h. The effects of NH4HCO3 concentration, pH during aging, and reaction temperature were investigated. The mechanism of bimodal pore formation was clarified. The results showed that large pores (10–100nm) were mainly formed in the reactor and during aging, and small pores (0–10nm) were mainly formed during calcination. When the concentration of NH4HCO3 was 1.5mol/L, the aging pH was 9.2, and the reaction temperature was 80°C, γ-alumina with a specific surface area of 504.7m2/g and pore volume of 1.76mL/g was obtained. The average size of the large pores was about 30nm, and the average size of the small pores was about 4nm.