Thermal analysis of montmorillonites modified with quaternary phosphonium and ammonium surfactants
Thermal analysis of montmorillonites modified with quaternary phosphonium and ammonium surfactants
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DOI：
10.1016/j.clay.2006.09.005
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发表时间：
2007-02-01
影响因子：
5.6
通讯作者：
Theng, B. K. G.
中科院分区：
文献类型：
--
作者：
Hedley, C. B.;Yuan, G.;Theng, B. K. G.
7有机改性蒙脱石（“有机粘土”）的热稳定性进行了研究，使用差热分析，差示扫描量热法，热重结合X-射线衍射。六个有机粘土合成取代层间无机阳离子，最初存在的，季鏻和铵表面活性剂阳离子。用四丁基鏻（TBP）和丁基三苯基鏻（BTPP）离子改性的样品具有比十八烷基三甲基铵（ODTMA）改性的粘土明显更高的热稳定性。因此，在TBP和BTPP改性的蒙脱石的情况下，分解的起始温度接近300 ℃。用十六烷基三丁基鏻（HDTBP）离子改性的样品具有225摄氏度的较低分解起始温度。相比之下，ODTMA-蒙脱石（在不同浓度的ODTMA-溴化物下获得）的起始温度范围为158至222 ° C，在插层表面活性剂的浓度最低时最高。商业烷基硅烷处理的季铵改性的有机粘土（S-BEN N-400 FP）的起始温度为207 ℃。TBP-和BTPP-改性粘土的基底间距为1.7-1.8 nm，表明季鏻离子在层间空间中的单层排列，而HDTBP-蒙脱土的2.5 nm的值表明更开放的结构。ODMA改性的样品具有范围从1.9至2.1 nm的基底间距，指示双层至伪三层布置。S-BEN N-400 FP有机粘土的3.4nm的异常高的基底间距可能是由于合成期间有机硅烷水解产物的层间渗透。有机粘土的热性能与表面活性剂的性质及其在蒙脱土层间的排列方式有关。(C)2006 Elsevier B. V.保留所有权利。
The thermal stability of seven organically modified montmorillonites ('organoclays') has been investigated using differential thermal analysis, differential scanning calorimetry, and thermogravimetry in conjunction with X-ray diffractometry. Six organoclays were synthesised by replacing the interlayer inorganic cations, initially present, with quaternary phosphonium and ammonium surfactant cations. The samples modified with tetrabutylphosphonium (TBP), and butyltriphenylphosphonium (BTPP) ions have an appreciably higher thermal stability than the octadecyltrimethylammonium (ODTMA)-modified clays. Thus, in the case of TBP- and BTPP-modified montmorillonites, the onset temperature of decomposition is close to 300 degrees C. Samples modified with hexadecyltributylphosphonium (HDTBP) ions have a lower onset temperature of decomposition of 225 degrees C. In comparison, the onset temperature for ODTMA-montmorillonites (obtained at different concentrations of ODTMA-bromide) ranges from 158 to 222 degrees C, being highest where the concentration of intercalated surfactant is lowest. The onset temperature for a commercial alkylsilane-treated quaternary ammonium-modified organoclay (S-BEN N-400FP) is 207 degrees C. The basal spacing of the TBP- and BTPP-modified clays is 1.7-1.8 nm, indicating a monolayer arrangement of quaternary phosphonium ions in the interlayer space, while the value of 2.5 nm for HDTBP-montmorillonite indicates a more open structure. The ODTMA-modified samples have basal spacings ranging from 1.9 to 2.1 nm, indicative of a bilayer to pseudo-trilayer arrangement. The exceptionally high basal spacing of 3.4 nm for the S-BEN N-400FP organoclay might be due to interlayer penetration of organosilane hydrolysis products during synthesis. The thermal properties of organoclays are apparently related to the nature of the surfactants and their arrangement in the interlayer space of montmorillonite. (C) 2006 Elsevier B.V. All rights reserved.