The Preparation And Characterization Of Al-Pillared Montmorillonite

Al-pillared montmorillonites is a new catalytic material with large surface area, high thermal stability and surface activity. In this work, montmorillonite ore from Xinyang, Henan provice was been purified and sodium-modified, Al₁₃-pillared montmorillonite and Al₂₄-pillared montmorillonite was prepared and characterized.Montmorillonite has been beneficiated by sedimentation separation process with sodium hexametaphosphate as dispersant, producing an ultra-pure montmorillonite, which the content of montmorillonite was 93.89%. Then sodium percarbonate was chose as modification agent to produce Na-montmorillonite.AlCl₃ solution was hydrolysed by NaOH to gain Al₁₃-pillaring agent. Al₁₃-pillared montmorillonite was prepared by Na-montnorillonite as stroma and Al₁₃ as pillaring agent. The spacing distance d₍₀₀₁₎ value of Na-montmorinollite was 1.2726 nm, but that of Al₁₃-pillared montmorillonite was 1.8948 nm. After Al₁₃-pillared montmorillonite being calcined at 500℃, its product was quit stable, which the basal interlayer spacing d₍₀₀₁₎ was stabilized at 1.8036 nm.Al₂₄-pillared montmorillonite was prepared using Al₂₄-pillaring agent, which was gained by a method of adding aluminum foil into the AlCl₃ solution. The formation conditions and properties of pillared interlayer montmorillonite were determined. The experimental results showed that aging time 55h under 97.5℃, the suspending liquid concentration of Na-montmorillonite 1%, Al/montmorillonite 10mmol/g and pillared reaction time 48h. Al₂₄-pillared montmorillonite with a large basal spacing, d₍₀₀₁₎=2.0533 nm, has been produced. After Al₂₄-pillared mont- morillonite being calcined at 700℃, its product was quit stable, which the basal interlayer spacing d₍₀₀₁₎ was stabilized at 1.7873nm.The IR results of montmorillonite being calcined at different temperatures showed that the IR spectra of Al₂₄-pillared montmorillonite were almost agreed with Na-montmorillonite. The structure of octahedron sheet of Al₂₄-pillared montmorillonite that were heated two hours at 500℃has been changed. The pillared agent after heated treatment might react with OH groups of octahedron sheet and formed stable covalent bond of Al^â…£-O-Al^â…¥.With the help of X-ray diffraction(XRD), infrared absorption Spectrum(IR), nuclear magnetic resonance (NMR), Thermal Analysis (TG/DSC), and chemical analysis, the characteristics of the Al₁₃-pillared montmorillonite and Al₂₄-pillared montmorillonite have been revealed. The crystal structures of Al₁₃ polyhydroxy cation and Al₂₄ polyhydroxy cation have been discussed respectively.