Study Of Catalytic Activity, Characterization And Preparation Of Aluminum- And Titanium-Pillared Clay

The clays with double-layer structure pillared with Al, Ti and/or other metallic cations have been proved to be one of the most interesting materials at home and abroad. Pillared interlayer clay(PILC) possesses several interesting properties, such as large surface area, high thermal stability, strong surface acidity etc. They are widely used in the fields such as catalysis, catalytic supports, selective sorbent, molecular screen and film for their good properties.In this article, the information about pillared clays and their application is reported detailedly. In this work, two serious of aluminum-PILC and titanium-PILC have been prepared by hydrolysis technique , have been characterized by chemical analysis, small angle X-ray diffraction, differential thermal analysis, BET surface area measurement, FTIR spectroscopy, 29Si MAS NMR spectra and 27Al MAS NMR spectra, scanning electron microscope and high-resolution transmission electron microscope, have been tested in the selective catalytic reduction of activity by H2 temperature-programmed reduction.Using potentiometric titration method, FTIR spectroscopy and nuclear magnetic resonance, after heating the hydrolyzed solution at 50℃, with OH-/Al3+=2.4 and aged 5d, the quantity of Al3+ polymeric cation which has Keggin structure in AlCl3 solution is more.Chemical analysis shows that Al3+ polymeric cation is Keggin ion and Ti polymeric cation is aberrant Keggin ion. The d(001) value of aluminum-PILC is 1.98vnm and the d(001) value of titanium-PILC is 1.83nm. 29Si MAS NMR and 27Al MAS NMR show that clay sheet is affected on Si-O tetrahedron and Al-O octahedron by Al3+ polymeric cation.It is found that smectite dehydrate absorbing water and interlayer water when the temperature is 182.5℃, this process is reversible. When the thermal treatment temperature reach 500℃, the hydroxyl in octahedral sheet begin dehydrating, but the layer structure id maintaining. DTA-TG shows TiO2-PILC thermal stability up to 800℃. It is the highest thermal stability among the tested pillared clays. The langmuir surface area of aluminum-PILC and titanium-PILC is 170m2/g and 283m2/g, respectively. Micropore surface area is 33 and 54 times larger than one of Na-smectite, respectively. The results of FTIR analysis show TiO2-PILC surface acidity is the strongest. The effect of Al polycation on the shifts of reflecting Si-O vibration in samples is the same with that of Ti polycation. Among the tested catalysts pillared clays based on titanium are most active for the H2 temperature-programmed reduction reaction.