本文選題：高嶺石　切入點(diǎn)：分子動力學(xué)模擬　出處：《中國礦業(yè)大學(xué)(北京)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：高嶺石是應(yīng)用比較廣泛的黏土礦物之一。在我國高嶺土資源儲量豐富,質(zhì)地優(yōu)良,廣泛應(yīng)用在橡膠、塑料、涂料、造紙、陶瓷及環(huán)保等領(lǐng)域。粒度和表面性質(zhì)是衡量高嶺石產(chǎn)品的重要指標(biāo),尤其在高新技術(shù)領(lǐng)域,高嶺石的粒度和表面特性直接影響產(chǎn)品的諸多性能。對高嶺石進(jìn)行插層,剝片及表面改性是實現(xiàn)高嶺石顆粒納米化及表面修飾等精細(xì)化加工的必要手段,可顯著提高高嶺石產(chǎn)品的附加值。到目前為止,實驗研究發(fā)現(xiàn)只有有限的幾種有機(jī)小分子可直接進(jìn)入高嶺石層間域。而有機(jī)大分子表面改性劑則需要通過間接插層法實現(xiàn)高嶺石層間域改性。雖然高嶺石/有機(jī)物復(fù)合體已經(jīng)通過X射線衍射、紅外光譜、拉曼光譜和核磁共振等方法得到廣泛研究,但高嶺石/有機(jī)物層間域在原子尺度范圍內(nèi)的界面結(jié)構(gòu)和界面作用尚無定論,有機(jī)化合物進(jìn)入高嶺石層間域的驅(qū)動因素尚不明晰。利用有代表性的有機(jī)化合物尿素,二甲基亞砜(DMSO),和大分子表面改性劑十二胺對純化的高嶺石進(jìn)行了液相插層,制備了高嶺石/尿素,高嶺石/DMSO和高嶺石/十二胺插層復(fù)合物。在XRD和熱重實驗分析的基礎(chǔ)上構(gòu)建了高嶺石/有機(jī)化合物復(fù)合分子模型,并對其進(jìn)行了分子動力學(xué)模擬,計算了高嶺石層間域表面與有機(jī)化合物之間的界面結(jié)構(gòu)和界面作用。采用自適應(yīng)偏置力(Adaptive Biasing Force)分子動力學(xué)模擬計算了表面改性劑對高嶺石/甲醇前驅(qū)體的插層自由能。通過對自由能的分解計算了表面改性劑與高嶺石/甲醇復(fù)合體層間域的相互作用能。從理論層面深入剖析了有機(jī)化合物在高嶺石層間域的界面結(jié)構(gòu)和界面作用機(jī)理,闡明了有機(jī)化合物對高嶺石插層的主要驅(qū)動力來源。在高嶺石層間域中,尿素分子呈單層結(jié)構(gòu)分布,其C=O官能團(tuán)作為氫鍵受體與高嶺石鋁氧面羥基形成較強(qiáng)的氫鍵,其NH2官能團(tuán)作為氫鍵給體與高嶺石鋁氧面羥基和硅氧面基面氧原子同時形成氫鍵。尿素與鋁氧面形成的氫鍵作用大于硅氧面。而且尿素與鋁氧面的相互作用能也大于硅氧面,因此鋁氧面對誘導(dǎo)尿素進(jìn)入高嶺石層間域起到關(guān)鍵作用。DMSO在高嶺石層間域也呈單層結(jié)構(gòu)分布,其S=O官能團(tuán)與高嶺石鋁氧面羥基形成較強(qiáng)的氫鍵作用,甲基則與硅氧面以疏水作用鍵合在一起。高嶺石硅氧面上的復(fù)三方孔和鋁氧面上的鋁氧八面體空穴都是局部高吸附位點(diǎn),分別對DMSO的甲基和S=O官能團(tuán)具有較強(qiáng)的吸附作用。高嶺石鋁氧面和硅氧面都對DMSO分子表現(xiàn)出親和性,但鋁氧面與DMSO的相互作用能高于硅氧面,加之鋁氧面羥基與DMSO S=O官能團(tuán)形成較強(qiáng)的氫鍵作用,因此對DMSO的插層起到關(guān)鍵作用。自適應(yīng)偏置力分子動力學(xué)模擬計算的改性劑對高嶺石/甲醇前驅(qū)體插層自由能表明高嶺石/甲醇復(fù)合體層間域?qū)y帶正電荷離子官能團(tuán)的十六烷基三甲基氯化銨(CTAC)具有較強(qiáng)的親和性。改性劑對高嶺石層間域插層的驅(qū)動力主要來源于與層間域鋁氧面、硅氧面和層間甲醇相互作用而獲得的焓變能量。其焓變能量主要來源于靜電勢能和范德華能,其中靜電勢能起主導(dǎo)作用。攜帶離子官能團(tuán)的CTAC和硬脂酸鈉可通過與高嶺石層間域的靜電引力作用獲得更多的焓變能量,相比于電中性的十二胺更容易實現(xiàn)高嶺石插層和改性。高嶺石的層間甲醇可使層間域更具疏水性可通過疏水作用、靜電引力作用和范德華能作用促進(jìn)大分子改性劑進(jìn)入高嶺石層間域。大分子表面改性劑十二胺可以高嶺石/甲醇插層復(fù)合物為前驅(qū)體進(jìn)入高嶺石層間域,使高嶺石層間距從7.2?擴(kuò)大到42.9?。分子動力學(xué)模擬表明十二胺分子的烷烴鏈并非呈有序的全反式結(jié)構(gòu)分布于高嶺石層間域,而是以類似于石蠟型和無序結(jié)構(gòu)分布于高嶺石層間域中心區(qū)域和有序的雙層結(jié)構(gòu)平行分布于高嶺石硅氧面和鋁氧面。本論文采用分子動力學(xué)模擬與實驗相結(jié)合的方法闡明了高嶺石/有機(jī)化合物層間域的界面結(jié)構(gòu)和界面作用,以及有機(jī)化合物進(jìn)入高嶺石層間域的驅(qū)動機(jī)理,為高嶺石插層與有機(jī)改性的實驗設(shè)計和制備高附加值高嶺石產(chǎn)品提供了理論依據(jù)。
[Abstract]:Kaolinite clay minerals is one of the widely used in kaolin resources in China is abundant, fine texture, widely used in rubber, plastic, paint, paper, ceramics and environmental protection. The field size and surface properties of kaolinite is an important indicator of products, especially in the high-tech fields, many properties of particle size and surface characteristics of kaolinite directly affect the products. On kaolinite intercalation and exfoliation and surface modification is a necessary means to realize nano kaolinite particles and surface modification of fine processing, can significantly improve the added value of kaolinite products. So far, the study found that only a limited number of small organic molecules directly into the interlayer of kaolinite while the organic macromolecular surface modifier is required by indirect intercalation method of kaolinite interlayer modified. Although kaolinite / organic complexes has been through X ray Diffraction, infrared spectroscopy, Raman spectroscopy and NMR methods has been widely studied, but the kaolinite / organic interlayer on the atomic scale interface structure and interface effect is inconclusive, driving factors of organic compounds into kaolinite interlayer is not clear yet. The representative organic compound urea, two dimethyl sulfoxide sulfone (DMSO), and the macromolecular surface modifier twelve amine on the purification of liquid phase kaolinite intercalation of kaolinite / urea were prepared, kaolinite and kaolinite / /DMSO twelve amine intercalation compound. XRD and thermogravimetry was established on the basis of kaolinite / organic compound molecular model. And has carried on the molecular dynamics simulation, interfacial structure and interfacial interaction between kaolinite interlayer surface and organic compounds were calculated. The adaptive biasing force (Adaptive Biasing Force) molecular dynamics model The surface modification of kaolinite / methanol precursor intercalation free energy were calculated. The surface modification agent and kaolinite / methanol complex interaction of interlayer energy calculated by decomposition of the free energy. From the theoretical level, in-depth analysis of the interface structure and interface mechanism of organic compounds in the kaolinite interlayer the main driving force, illustrates the sources of organic compounds on kaolinite intercalation. The kaolinite interlayer, urea molecule monolayer distribution structure, the C=O groups form strong hydrogen bond as a hydrogen bond acceptor and surface hydroxyl of kaolinite alumina, the NH2 functional groups as hydrogen bond donor and surface hydroxyl of kaolinite and silica alumina base surface oxygen at the same time the formation of hydrogen bonds. Atomic hydrogen bonding of urea and alumina surface to form larger than silicon oxygen. But the interaction between urea and alumina can also larger than the silica surface, so the face of urea induced into alumina 鍏ラ珮宀煶灞傞棿鍩熻搗鍒板叧閿綔鐢，

本文編號：1572809