Synthesis of Well-Ordered Mesoporous Aluminosilicates with High Aluminum Contents: The Challenge and the Promise

Abstract

has recently emerged as a potential material for the catalytic conversion of large molecules. Usually, SBA-15 has a low content of aluminum due to the conventional acidic synthesis medium. Although a few approaches have been adopted to prepare Al−SBA-15 with a high alumina content, it is still challenging to prepare well-ordered Al−SBA-15 with a high alumina content. Here, we demonstrate a facile synthesis process in neutral mediums for the grafting of Al into the framework of SBA-15. This approach relies mainly on the dissociation of Si−O−Si bonds and the polymerization of Si−O−Si/Al bonds promoted by sodium persulfate (SPS) in neutral mediums. In this way, well-ordered Al−SBA-15 with a high aluminum content and enhanced acidity was obtained. Results of X-ray fluorescence spectroscopy (XRF) showed an n(SiO 2 )/n(Al 2 O 3 ) ratio of 13.7, much lower than that of the conventional sample (21.7) obtained in acidic medium. The characterization results indicated the presence of a wellordered Al-containing mesophase with high hydrothermal stability. Notably, the Al content and the acidity of Al−SBA-15 can be tuned by changing the SPS amount.

Synthesis of Mesoporous Aluminosilicates with Moderate Acidity and High Hydrothermal Stability by Acid-Free Method

“…This was consistent with the results of previous literatures. 20,22,23 Physicochemical properties of samples are listed in Table 2. As seen in Table 2, a gradual increase of the unit-cell parameter (a 0 ) was observed with the decrease of the Si/Al ratio in raw materials.…”

“…To investigate the catalytic cracking performance of final products, we selected MMS-PS, Al-SBA-10 (synthesized according to our previous literature), 20 and Al-MMS-3 to prepare FCC catalysts and studied their properties.…”

“…In spite of these advances, the synthesis of Al-SBA-15 by ·OH-assisted strategy remains an untouched area. In our previous works, ·OH-assisted method was adopted for the synthesis of Al-SBA-15 with high content of Al species by using P123 as template . However, this process still suffers from the use of mineral acid and weak acidity of MAs products.…”

“…In our previous works, •OHassisted method was adopted for the synthesis of Al-SBA-15 with high content of Al species by using P123 as template. 20 However, this process still suffers from the use of mineral acid and weak acidity of MAs products. Inspired by the above investigations, obtaining Al-SBA-15 with superior hydrothermal stability and moderate acidity via a •OH-assisted procedure is demonstrated in this investigation.…”

A Review of High-Efficient Synthetic Methods for Zeolite Membranes and Challenges of Their Directional Growth Control

“…Relying on the free radical initiator sodium persulfate to promote the dissociation of Si-O-Si bonds and the polymerization of Si-O-Si/Al bonds in neutral medium, mesoporous aluminosilicate with high aluminum content is obtained, and the content of Al can be adjusted by changing the amount of sodium persulfate. [12] Moreover, according to supplementary reference [2] and [3], it is found that the structure-directing effect and nuclei source effect of crystal seeds bring higher relative crystallinity and a lower waste discharge. When Liu et al used the seed method to assist in the synthesis of zeolites, the crystal seeds could also improve the synthesis rate and crystallinity of zeolites and significantly reduce the amount of water and template agent.…”