Simple Synthesis and Characterization of Hexagonal and Ordered Al–MCM–41 from Natural Perlite

Hongyun Chen,Siyao Fu,Liangjie Fu,Deliang Chen,Huaming Yang

doi:10.3390/min9050264

Abstract

Silica reagents are expensive and toxic for use in the synthesis of mesoporous silica materials. It is imperative to take an interest in green silicon sources. In this paper, we report the synthesis of hexagonal and ordered aluminum-containing mesoporous silica materials (Al–MCM–41) from natural perlite mineral without addition of silica or aluminum reagents. A pretreatment process involving acid leaching, alkali leaching, and strongly acidic cation exchange resins treatment was critical to obtain silicon and aluminum sources from natural perlite mineral. The Al–MCM–41 material was synthesized via a hydrothermal reaction with hexadecyl trimethyl ammonium bromide (CTAB) as the template and subsequent calcination. The resulting mesophase had a hexagonal and ordered mesoporous structure, confirmed by small-angle X-ray diffraction (SAXRD) and transmission electron microscopy (TEM). Al–MCM–41 material had a high Brunauer–Emmet–Teller (BET) surface area of 1024 m2/g, pore volume of 0.72 cm3/g and an average pore diameter of 2.8 nm with a pore size distribution centered at 2.5 nm. The thermal behavior of the as-synthesized samples during calcination was investigated by thermogravimetry (TG) and differential thermogravimetry (DTG) analysis. The Al–MCM–41 material showed a negative surface charge in aqueous solution with the pH value ranging from 2 to 13. The variations of chemical structures from natural perlite to Al–MCM–41 were traced by wide-angle X-ray diffraction (WAXRD) and Fourier-transform infrared spectroscopy (FTIR). A proposed mechanism for the synthesis of hexagonal and ordered mesoporous silica materials from natural perlite is discussed.

Highlights

MCM–41, one of the members of M41S reported by scientists at the Mobil Research &Development Corporation in 1992, is a hexagonal and ordered mesoporous silica material, with uniform mesopores [1,2]
Our work focuses on the production of silicon and aluminum sources from natural perlite mineral instead of silica or aluminum reagents and the synthesis of aluminum-containing mesoporous silica materials (Al–MCM–41) via hydrothermal treatment and subsequent calcination
Mesoporous silica materials have been successfully synthesized via hydrothermal treatment using natural perlite as silicon and aluminum sources, without the addition of silica or aluminum reagents

Summary

Introduction

MCM–41, one of the members of M41S reported by scientists at the Mobil Research &Development Corporation in 1992, is a hexagonal and ordered mesoporous silica material, with uniform mesopores [1,2]. Traditional mesoporous silica materials were synthesized with sodium silicate, tetraethyl orthosilicate, or tetramethyl orthosilicate as silicon sources. These commercial silicon sources were expensive and toxic, potentially introducing pollution during preparation. Silicate minerals had been considered as green silicon sources to synthesize mesoporous silica materials. Ali-dahmane et al reported the successful synthesis of MCM–41 from bentonite with a Brunauer–Emmet–Teller (BET) surface area of 494 m2 /g [20]; their work resolved the problem that laboratory reagents were expensive and toxic for the large-scale production of MCM–41 and revealed the relationship between the structural properties of MCM–41 and the mineral phase contents of Algerian bentonite [20]. Yu et al [21] used diatomite as silicon and aluminum sources to successfully synthesize MCM–41 with ionic liquid

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Results

Conclusion