Preparation of Uniform γ-Alumina Microspheres with Large Pore Volumes in a Coaxial Microchannel

A novel and effective method is proposed to prepare uniform γ-alumina microspheres with large pore volumes using a coaxial microchannel. In this process, the so-called “temperature/pH-induced gelation” method, in which methylcellulose (MC) and hexamethylenetetramine (HMTA) are added to accelerate gelation of Al(OH)3 sol, is combined with microfluidics technology to ensure sphericity and dimensional homogeneity of the prepared microspheres. The influences of the sol concentration, the properties of pseudoboehmite (PB) used to obtain the sol, and the two-phase flow rates were investigated. By controlling the sol concentration at 10 wt % and the continuous to dispersed phase flow ratio at 14–50, 750–380-μm-diameter γ-alumina microspheres with uniform pore structures were synthesized using an Al(OH)3 sol obtained from PB3. The pore volume was 1.20 mL/g, and the crushing strengths were 8.19–16.67 N/mm2. Prepared at the maximum two-phase flow ratio, sample S9 exhibited the most uniform particle size of about 380 μm.