氨水介质和氟处理对铝柱层柱粘土性质的影响

Effect of Aqueous Ammonia Medium and Fluorine Treatment on Properties of Alumina-Pillared Clays

分别在氨介质和钠介质中制备了层柱蒙脱土和层柱累托石 ,并用氟化铵、氟硅酸铵和氟铝酸铵对层柱粘土进行处理 ,考察了处理条件对层柱粘土结构和酸性的影响 .NH3 TPD和IR分析结果表明 ,氨介质中制备的层柱粘土比钠介质中制备的具有更强的酸性 ,经氟处理后层柱粘土的酸性有较大的提高 .氨介质中制备的层柱粘土的低钠含量是其酸性改善的主要原因 ,而氟处理对层柱粘土酸性的提高主要来自氟对铝柱的表面作用 .氟处理层柱粘土对异丙苯裂解具有很高的催化活性 .

Alumina-pillared clays were prepared by intercalation of [Al 13O 4(OH) 24(H 2O) 12] 7+, which was obtained by adding NaOH or NH 3·H 2O to an AlCl 3 solution, into the natural montmorillonite and rectorite, followed by calcination. Fluorine treatment of the above solid materials was carried out in NH 4F, (NH 4) 3AlF 6 or (NH 4) 2SiF 6 solution. The influence of treatment conditions on the structure of the pillared products was investigated by X-ray diffraction, NH 3-temperature-programmed desorption and infrared spectroscopy of adsorbed pyridine. The pillared clays obtained with ammonia exhibit higher acid strength than the clays prepared with NaOH due to the lower sodium content in the former samples. The unique electron-withdrawing property of fluorine plays a vital role in the enhancement of the acidity and the cumene cracking activity of the fluorine-treated alumina-pillared clays. Fluorine treatment mainly modifies the surface of alumina pillars though the fluorination of the layer host cannot be excluded when a high ratio of fluorine to clay was used in the treatment.