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

In this paper, we present a new method for preparing gamma-alumina nanoparticles with a bimodal pore size distribution by using an efficiently mixing membrane dispersion microreactor. NF4HCO3 and Al-2(SO4)(3 center dot)18H(2)O were reacted under vigorous mixing to give an ammonium aluminum carbonate hydroxide (AACH) precursor. gamma-Alumina was obtained by calcination of AACH at 550 degrees C for 6 h. 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 (10-100 nm) were mainly formed in the reactor and during aging, and small pores (0-10 nm) were mainly formed during calcination. When the concentration of NH4HCO3 was 1.5 mol/L, the aging pH was 9.2, and the reaction temperature was 80 degrees C, gamma-alumina with a specific surface area of 504.7 m(2)/g and pore volume of 1.76 mL/g was obtained. The average size of the large pores was about 30 nm, and the average size of the small pores was about 4 nm. (C) 2018 Published by Elsevier B.V. on behalf of Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences.