Preparation And Thermal Stability Properties Of Magadiite And Its Derivatives

Pillared material is a conception proposed recently.It is a new kind of compound materials with homogeneous pore structure.It is prepared by introduced some large ions, complexing ions or molecules into interlayers of some layer materials,where the ions,complexing ions and molecules are called pillaring agent(guest)and the layer materials are called precursor(host).Pillared material is widely used in many fields,such as the catalytic agent, catalytic agent carrier,adsorbent and so on.When layer silicates are used as host,the pillared materials are called pillared silicates.Now,smectite and kaolinite are the two main layer silicates,which are used as hosts.Magadiite(Na2Si14O29-xH2O) is a kind of layer silicates with uniform gallery height,so it a perfect host for the pillared material.In this experiment,we used magadiite as host to prepare organic and inorganic pillared materials by ion-exchange method.First,we used water glass(byproduct from industry) and NaOH as raw material to prepare magadiite by hydrothermal synthesis method.Further we discussed influencing factors in this process,including reaction time,reaction temperature and the kind of cations.The XRD analysis showes that the product is pure magdiite with good cristallinity when the reaction temperature is 160℃and the reaction time is 48h.The d-spacing of prepared magadiite is about 1.54nm.We got H-magadiite by exchanging Na+in interlayers with H+from HC1 solution. The XRD analysis showes that the d-spacing of H-magadiite is about 1.32nm when the concentration of H+is O.lmol/L and the reaction time is 24h.Secondly,we used hexadecyltrimethyl ammonium(C16TMA+) as gust to prepare organic pillared magadiite by ion-exchange method and characterized this organic pillared material with XRD,SEM and FT-IR methods.The XRD analysis showes that the d-spacing of C16TMA-magadiite varies with the amount of C16TMABr and the d-spacing has the largest value,(about 3.10nm),when the the amount of C16TMABr is 2.5CEC.By comparing the dimensions of C16TMA+ion and gallery height of pillared material,we could conclude the arrange of C16TMA+ions in gallrey.Thirdly, we used Al13Keggin ion as gust to prepare inorganic pillared magadiite with single-step method and multistep method.The XRD analysis showes that when the multistep method was adopted,we could got Al13-magadiite,whose d-spacing was about 4.258nm.Finally, we compared the thermal stability of magadiite and its derivatives.The results showed that the intercalation of C16TMA+would weaken the thermal stability of pillared magadiite,while the intercalation of Al13Keggin ion would enhance the thermal stability of pillared magadiite.The layer structure of C16TMA-magadiite could be kept until 380℃while the layer structure of Al13-magadiite could not be destroyed until 720℃.