十二烷基三甲基氯化铵与四甲基氯化铵改性钠基蒙脱石的性质研究

Study on the properties of dodecyltrimethyl ammonium chloride and tetramethyl ammonium chloride modified sodium montmorillonite

利用十二烷基三甲基氯化铵(DTAC)和四甲基氯化铵(TTAC)分别对钠基蒙脱石(Na-MMT)进行有机改性,合成了DTA-MMT和TTA-MMT两种蒙脱石复合材料.采用热重分析(TGA)、X射线衍射(XRD)等实验表征技术,以及蒙特卡洛(MC)模拟理论计算手段,对两种改性蒙脱石体系进行比较研究,探索了季铵盐添加量以及季铵盐烷基链长的变化对改性蒙脱石的片层空间结构与热力学性质的影响.研究表明,改性后的两种蒙脱石层间距均有一定程度的增大,当插层量增大时,具有长链烷基季铵盐的DTA-MMT体系对蒙脱石片层空间的撑大作用明显好于TTA-MMT体系;与自由相的季铵盐相比,插层季铵盐热分解温度显著提高,表明改性蒙脱石有利于其热稳定性的提升;此外,蒙特卡洛模拟得到的蒙脱石层间距数值与实验XRD表征结果具有很好的一致性,为进一步合理解释TGA与XRD等实验表征结果奠定了基础.

Dodecyltrimethyl ammonium chloride(DTAC)and tetramethyl ammonium chloride(TTAC)were used to organically modify sodium montmorillonite(Na-MMT)to synthesize DTA-MMT and TAC-MMT complexes.Using thermogravimetric analysis(TGA),X-ray diffraction(XRD),and Monte Carlo(MC)simulation methods,a comparative study of the two modified montmorillonite was conducted.The effects of quaternary ammonium salt(QAS)concentration and its alkyl chain length on the interlayer spacing and thermodynamic properties of the modified montmorillonite were explored.The research shows that for the two modified montmorillonite complexes,QAS intercalation can increase the interlayer distance of montmorillonite complex,and DTAC with long alkyl chain has a better expansion effect on the interlayer spacing at larger concentration.The thermal decomposition temperature of intercalated quaternary ammonium cations increases significantly,indicating that organic modif cation of montmorillonite can enhance its thermal stability.In addition,the value of interlayer spacing of the modified montmorillonite obtained by Monte Carlo simulations is in good agreement with the one from the XRD characterization,which lays the foundation for further interpretation of experimental results such as TGA and XRD by using the simulated results.