Preparation of Large-Pore-Volume γ-Alumina Nanofibers with a Narrow Pore Size Distribution in a Membrane Dispersion Microreactor

Abstract

A coprecipitation method was developed to synthesize fibrous γ-Al 2 O 3 with a large pore volume using a membrane dispersion microreactor with NaAlO 2 and Al 2 (SO 4 ) 3 as reactants. The pore size distribution was controlled because of the high mixing intensity and relatively homogeneous saturation in the membrane dispersion microreactor. The influences of the pH and concentration of the NaAlO 2 aqueous solution and of the two-phase flow rates were investigated. By controlling the pH to be around 9 and the concentration of NaAlO 2 aqueous solution to be 0.50−1.25 mol/L, we obtained γ-Al 2 O 3 nanofibers with pore volume of 0.95−1.52 mL/g. Under the maximal pore volume (1.52 mL/g), the specific surface area was 403.8 m 2 /g and the pore size distribution was 3−50 nm with a distribution variance of 0.2020. The length and diameter of the nanofibers were about 27.3 and 3.4 nm, respectively. This study provides a simple, economical method for preparing fibrous γ-Al 2 O 3 with both a large pore volume and a narrow pore size distribution, which could be used as an excellent catalyst support for the petroleum-refining industry.

Synthesis of Mesoporous γ-Al2O3 with Spongy Structure: In-Situ Conversion of Metal-Organic Frameworks and Improved Performance as Catalyst Support in Hydrodesulfurization

“…The type of isotherm and hysteresis loop agrees well with the TEM observations and the spongy-like structure with uniform slit-like pores in Al 2 O 3 -Spongy. The BET surface area of Al 2 O 3 -Spongy is 350 m 2 g −1 , and the pore volume is 0.63 cm 3 g − 1 , both higher than reported alumina materials synthesized by boehmite precursor and other Al-MOFs [ 18 , 19 , 20 , 25 , 26 ]. The N 2 sorption isotherms of Al 2 O 3 -PB are also Type IV ( Figure 3 a), suggesting the mesoporous structure of this alumina.…”

Biogas Upgrading via Cyclic CO2 Adsorption: Application of Highly Regenerable PEI@nano-Al2O3 Adsorbents with Anti-Urea Properties

“…During the CO 2 -assisted precipitation process, the pseudoboehmite (AlOOH) precursor was first obtained for the subsequent calcination of nano-Al 2 O 3 supports. The pseudoboehmite was composed of O–Al–OH molecular clusters, which were formed from the Al 3+ trimer ([Al 3 (OH) 4 (OH 2 ) 9 ] 5+ ) screw dislocation growth . According to the nucleation-growth theory, the NaAlO 2 solution saturation plays a crucial role in AlOOH crystal nucleation and growth.…”

“…According to the nucleation-growth theory, the NaAlO 2 solution saturation plays a crucial role in AlOOH crystal nucleation and growth. A relatively low NaAlO 2 solution saturation leads to slight nucleation, which causes a tendency for screw dislocation growth from the Al 3+ trimer, while a considerably high saturation leads to explosive crystal grain nucleation and isotropic growth . As a result, these two crystal growth patterns tend to form two different morphologies, namely, porous clusters and spherical nanoparticles.…”

“…The pseudoboehmite was composed of O−Al−OH molecular clusters, which were formed from the Al 3+ trimer ([Al 3 (OH) 4 (OH 2 ) 9 ] 5+ ) screw dislocation growth. 40 According to the nucleation-growth theory, the NaAlO 2 solution saturation plays a crucial role in AlOOH crystal nucleation and growth. A relatively low NaAlO 2 solution saturation leads to slight nucleation, which causes a tendency for screw dislocation growth from the Al 3+ trimer, while a considerably high saturation leads to explosive crystal grain nucleation and isotropic growth.…”

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

“…In this work, a novel and effective method to prepare uniform γ-alumina microspheres with large pore volumes is proposed. The Al­(OH) 3 sol is prepared by dissolving the large-pore-volume pseudoboehmite (PB) powders synthesized in our previous work with nitric acid. Subsequently, a coaxial microchannel is utilized to shape the sol into microdroplets by the shear force of the continuous phase against the dispersed phase.…”