高岭石-硬脂酸插层复合物的制备及结构模型的提出

以张家口高岭土为原料,通过直接插层与取代相结合的方法制备高岭石-硬脂酸插层复合物。利用X射线粉末衍射、红外光谱、热重及透射电子显微镜对制备产物进行表征。结果表明:硬脂酸插入到高岭石层间,高岭石层间距d001值由0.72 nm增加到4.05~4.37 nm,插层率达到86.9%;反应时间和溶液p H值会对高岭石-硬脂酸插层复合物的层间距及插层率产生影响;甲氧基嫁接在高岭石表面,与硬脂酸分子同时存在于高岭石层间。高岭石经甲醇改性后脱羟基温度明显降低,高岭石羟基活性提高;高岭石-硬脂酸插层复合物的稳定温度在160℃以下。经过硬脂酸插层改性后的高岭石片层,从边缘开始出现卷曲现象,并且部分长条状片层形成类似埃洛石相的纳米卷;对硬脂酸插层高岭石的作用机理进行分析,结合结构计算,提出高岭石-硬脂酸插层复合物的结构模型,该模型可以解释高岭石-硬脂酸插层复合物在不同条件制备产物层间距变化的原因。     

高岭石-硬脂酸插层复合物的制备及结构模型的提出

以张家口高岭土为原料,通过直接插层与取代相结合的方法制备高岭石-硬脂酸插层复合物.利用 X射线粉末衍射、红外光谱、热重及透射电子显微镜对制备产物进行表征.结果表明:硬脂酸插入到高岭石层间,高岭石层间距d₀₀₁值由0.72 nm增加到4.05~4.37 nm,插层率达到86.9%;反应时间和溶液pH值会对高岭石-硬脂酸插层复合物的层间距及插层率产生影响;甲氧基嫁接在高岭石表面,与硬脂酸分子同时存在于高岭石层间.高岭石经甲醇改性后脱羟基温度明显降低,高岭石羟基活性提高;高岭石-硬脂酸插层复合物的稳定温度在160 ℃以下.经过硬脂酸插层改性后的高岭石片层,从边缘开始出现卷曲现象,并且部分长条状片层形成类似埃洛石相的纳米卷;对硬脂酸插层高岭石的作用机理进行分析,结合结构计算,提出高岭石-硬脂酸插层复合物的结构模型,该模型可以解释高岭石-硬脂酸插层复合物在不同条件制备产物层间距变化的原因.     

直接置换插层法0.85 nm水合高岭石的制备

以高岭石/尿素插层复合物作为中间相,利用简单的直接置换插层法制备了d001=0.85 nm的水合高岭石。利用X射线衍射、红外光谱、扫描电镜表征处理前后高岭石结构与形貌的变化。结果表明:尿素插层后的高岭石层间距从d001=0.72 nm增大到d001=1.08 nm,经不同温度酸洗或水洗后,插层复合物转变成层间有水分子的水合高岭石(d001=0.85 nm),且高岭石晶粒厚度明显从约25 nm减小到约10 nm。在高温条件下形成的水合高岭石含量最高,90℃水洗时d001=0.85 nm水合高岭石的转化率接近70%,这种水合高岭石具有进一步的置换插层能力,是一种制备其他高岭石插层复合物很好的前驱体。与乙二醇形成d001=1.10nm乙二醇/高岭石插层复合物,其置换率达到100%。     

高岭石纳米卷的制备与表征

本文以层状茂名高岭石为原材料,利用二甲亚砜、甲醇、十六烷基三甲基氯化铵(CTAC)插层处理成功制备了高岭石纳米卷。利用X射线衍射、红外光谱、扫描电镜、透射电镜、N2吸附-脱附、29Si CP/MAS NMR表征插层前后高岭石结构与形貌的变化。分析表明,高岭石片层的卷曲和剥离同时进行,随着CTAC甲醇溶液浓度的增加以及反应时间的延长,高岭石纳米卷的外径增加,而内径基本保持不变。高岭石纳米卷形成机理与CTAC分子的插层减弱了高岭石层与层之间作用以及表面活性剂的模板效应有关。     

PEG在微波诱导下对高岭石插层及剥片的研究

利用微波能量，快速制备了高岭石/DMSO插层复合物，并以其为前驱体，在熔融状态，微波诱导聚乙二醇(PEG)置换出高岭石层间的DMSO，微波继续协同PEG作用，可以实现其对高岭石的剥片。同时提出了微波作用机理和微波条件下插层物对高岭石的剥片机理。采用X-射线衍射、FTIR光谱、TG-DTA、TEM等技术对插层复合物进行了表征。     

高岭石插层效率评价

用基于X射线衍射分析(XRD)的插层率、基于热重分析(TGA)的热失重率和基于红外光谱分析(FTIR)的3 600 cm^-1谱带与3 700 cm^-1谱带强度比值对高岭石/二甲基亚砜(DMSO)插层复合物和高岭石/N-甲基甲酰胺(NMF)插层复合物的插层效率进行了综合评价。结果表明,当插层反应进行到1、6和25 d,高岭石/DMSO的插层率分别为5%、52%和89%;而高岭石/NMF的插层率则分别为93%、94%和95%。与此同时,高岭石/DMSO的热失重率分别为1.06%、8.06%和17.46%;而高岭石/NMF的失重率分别为6%、6.5%和14.2%。在红外光谱图中,高岭石/DMSO复合物的3 600与3 700 cm^-1带强度比分别为1.03,1.141和1.628,而高岭石/NMF复合物分别为1.403,1.433和1.612。3种评价方法显示很好的一致性,相对而言,在插层作用的初期,XRD方法比较灵敏,而在插层作用的后期,TGA和FTIR方法则显得更为灵敏和有效。     

高岭石/苯甲酰胺插层复合物的热分解行为及脱嵌反应动力学

以高岭石/二甲基亚砜为前驱体,利用置换法制备了高岭石/苯甲酰胺插层复合物。XRD和FTIR分析表明苯甲酰胺进入高岭石层间并与其形成新的氢键。采用TG、DSC研究了插层复合物的热分解行为。结果表明复合物在加热过程中发生两步分解,第一步是插层复合物的分解,即插层剂分子于231℃发生脱嵌,第二步为高岭石脱羟基的过程。针对第一阶段的脱嵌反应,采用等转化率法改进后的迭代法、Malek法以及Dollimore法等动力学方法计算得到了完整的动力学三因子:活化能Ea=75.4kJ.mol-1,指前因子A的范围为4.9×1010~8.8×1010s-1,动力学方程为:G(α)=[1-(1-α)1-n]/(1-n),f(α)=(1-α)n。     

水分子在高岭石中插层行为的量子化学研究

采用密度泛函理论B3LYP方法,在B3LYP/6-31G(d)理论水平上,构建高岭石的层间团簇模型Si6Al6O42H42(层间距为0.844 0和1.000 0nm),并对高岭石层间及其与n(n=1～3)个水分子相互作用的团簇的各种性质进行研究,如优化的几何构型、电子密度、氢键、能量、NBO电荷分布、振动频率等.结果表明,随着水分子个数n(n=1～3)的增加,体系的能量逐渐降低.水分子通过多种类型的氢键插层于高岭石层间,其中水分子间的氢键强度最强,其次是水分子与铝氧层之间形成的氢键,再次是水分子与硅氧层之间的氢键;层间距随着插层分子的增多而增大,但高岭石层间的活性位点依然存在,且位置较插层前没有明显变化.     

高岭石/APTES插层复合物的表征及其脱嵌反应动力学

以高岭石/甲醇(K/M)复合物为前驱体,利用置换法制备出了高岭石/γ-氨丙基三乙氧基硅烷插层复合物(K/APTES),并应用XRD、FTIR、TEM、TG-DSC分析等表征手段对复合物进行了分析。结果表明:APTES分子的氨基与前驱体K/M的四面体硅氧烷基、嫁接在铝氧八面体表面上的甲氧基均发生键合作用形成氢键,APTES分子为两层倾斜排列于高岭石层间,倾角大小与温度有关。插层剂APTES破坏了高岭石层间的氢键,加剧了高岭石自身结构中硅氧四面体片层与铝氧八面体片层之间存在的错位,使得K/APTES插层复合物的部分片层卷曲变形。还针对复合物的插层剂APTES的脱嵌反应,采用Satava积分法和AcharBrindley-Sharp-Wendworth微分法相结合的动力学方法计算得到了完整的动力学三因子:活化能E=197.8 k J·mol-1,指前因子的对数lg(A/s-1)=14.60,最概然机理函数为:f(α)=[-ln(1-α)]-1,G(α)=α+(1-α)ln(1-α)。     

水合肼在高岭石层间插层行为的量子化学研究

水合肼以其碱性及吸附性受到越来越多的关注,同时它在粘土中的污染问题也越来越受到重视.本工作构建了高岭石团簇模型为Al6Si6O42H42并在B3LYP/6-31G(d,p),MP2/6-31G(d,p)//B3LYP/6-31G(d,p)和MP2/6-31++G(d,p)//B3LYP/6-31G(d,p)水平下对一水合肼以及二水合肼在高岭石层间的插层性质(如:优化构型、结构参数、结合能、电荷分布、振动光谱、静电势等)进行探究.计算表明,当一水合肼进入层间后,水分子和肼分子之间的相互作用发生了改变.即水与肼分子分别以氢键的形式插层于高岭石层间,且肼与高岭石之间的相互作用要强于肼与水之间的相互作用,同时插层位点多位于高岭石四面体层和八面体层的重叠区域内,这些都是水合肼易进入高岭石层间而难以脱去的重要因素.当二水合肼进入层间后,随着层间距的不断扩大,肼分子与高岭石铝氧层之间的相互作用仍强于肼分子与水分子间的作用.但当层间距超过1.05 nm时,水分子与肼分子之间的作用则强于肼分子与高岭石的作用,这也印证了若要将肼脱附,需将层间距增大以减弱肼分子与高岭石的作用,再用溶剂将其脱附的可行性.     

Effect of water on the formamide-intercalation of kaolinite

The molecular structures of low defect kaolinite completely intercalated with formamide and formamide-water mixtures have been determined using a combination of X-ray diffraction, thermoanalytical techniques, DRIFT and Raman spectroscopy. Expansion of the kaolinite to 10.09 A was observed with subtle differences whether the kaolinite was expanded with formamide or formamide-water mixtures. Thermal analysis showed that greater amounts of formamide could be intercalated into the kaolinite in the presence of water. New infrared bands were observed for the formamide intercalated kaolinites at 3648, 3630 and 3606 cm(-1). These bands are attributed to the hydroxyl stretching frequencies of the inner surface hydroxyls hydrogen bonded to formamide with water, formamide and interlamellar water. Bands were observed at similar positions in the Raman spectrum. At liquid nitrogen temperature, the 3630 cm(-1) Raman band separated into two bands at 3633 and 3625 cm(-1). DRIFT spectra showed the hydroxyl deformation mode at 905 cm(-1). Changes in the molecular structure of the formamide are observed through both the NH stretching vibrations and the amide 1 and 2 bands. Upon intercalation of kaolinite with formamide, bands are observed at 3460, 3344, 3248 and 3167 cm(-1) attributed to the NH stretching vibration of the NH involved with hydrogen bonded to the oxygens of the kaolinite siloxane surface. In the DRIFT spectra of the formamide intercalated kaolinites bands are observed at 1700 and 1671 cm(-1) and are attributed to the amide 1 and amide 2 vibrations.     

The Modification of Hydroxyl Surfaces of Formamide-Intercalated Kaolinites Synthesized by Controlled Rate Thermal Analysis

Controlled rate thermal analysis (CRTA) technology made possible the separation of adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites. X-ray diffraction shows that the CRTA-treated formamide-intercalated kaolinites remain expanded after CRTA treatment. The Raman spectra of the CRTA-treated formamide-intercalated kaolinites are significantly different from those of the intercalated kaolinites with both intercalated and adsorbed formamide. An intense band is observed at 3629 cm(-1), attributed to the inner surface hydroxyls hydrogen bonded to the formamide. Broad bands are observed at 3600 and 3639 cm(-1) and are attributed to the inner surface hydroxyls, which are hydrogen bonded to the adsorbed water molecules. The hydroxyl stretching band of the inner hydroxyl is readily observed at 3621 cm(-1) in the Raman spectra of the CRTA-treated formamide-intercalated kaolinites. The results of thermal analysis show that the amount of intercalated formamide between the kaolinite layers is independent of the presence of water. The Raman bands of the formamide in the CRTA-treated intercalated kaolinites are readily observed. Copyright 2001 Academic Press.     

Vibrational spectroscopy of formamide-intercalated kaolinites

The vibrational spectroscopy of low and high defect kaolinites fully and partially intercalated with formamide have been determined using a combination of X-ray diffraction, DRIFT and Raman spectroscopy. Expansion of the high defect kaolinite to 10.09 A resulted in a decrease in the peak width of the d(001) peak attributed to a decrease in defect structures upon intercalation. Changes in the defect structures of the low defect kaolinite were observed. Additional infrared bands were observed for the formamide intercalated kaolinites at 3629 and 3606 cm(-1). The 3629 cm(-1) band is attributed to the hydroxyl stretching frequency of the inner surface hydroxyl group hydrogen bonded to the carboxyl group of the formamide. The 3606 cm(-1) band is ascribed to water in the interlayer. Concomitant changes are observed in both the hydroxyl deformation modes and in the carboxyl bands.     

The effect of mechanochemical activation upon the intercalation of a high-defect kaolinite with formamide

The effect of mechanochemical activation upon the intercalation of formamide into a high-defect kaolinite has been studied using a combination of X-ray diffraction, thermal analysis, and DRIFT spectroscopy. X-ray diffraction shows that the intensity of the d(001) spacing decreases with grinding time and that the intercalated high-defect kaolinite expands to 10.2 A. The intensity of the peak of the expanded phase of the formamide-intercalated kaolinite decreases with grinding time. Thermal analysis reveals that the evolution temperature of the adsorbed formamide and loss of the inserting molecule increases with increased grinding time. The temperature of the dehydroxylation of the formamide-intercalated high-defect kaolinite decreases from 495 to 470 degrees C with mechanochemical activation. Changes in the surface structure of the mechanochemically activated formamide-intercalated high-defect kaolinite were followed by DRIFT spectroscopy. Fundamentally the intensity of the high-defect kaolinite hydroxyl stretching bands decreases exponentially with grinding time and simultaneously the intensity of the bands attributed to the OH stretching vibrations of water increased. It is proposed that the mechanochemical activation of the high-defect kaolinite caused the conversion of the hydroxyls to water which coordinates the kaolinite surface. Significant changes in the infrared bands assigned to the hydroxyl deformation and amide stretching and bending modes were observed. The intensity decrease of these bands was exponentially related to the grinding time. The position of the amide C=O vibrational mode was found to be sensitive to grinding time. The effect of mechanochemical activation of the high-defect kaolinite reduces the capacity of the kaolinite to be intercalated with formamide.     

高岭石结构缺陷的 1H MAS NMR和Raman研究

The structure default of kaolinites was characterized with ¹H MAS NMR and Raman spectra. Although the HI indexes of Suzhou and Maoming kaolinite are similar, their ¹H MAS NMR and Raman spectra are very different. ¹H MAS NMR showed that the hydroxyl proton chemical shifts of Suzhou kaolinite are in the higher field and with larger different between the inner surface hydroxyls protons and inner hydroxyls proton chemical shifts than Maoming kaolinite. Raman spectra showed that the surface hydroxyls stretching vibration bands of Suzhou kaolinite are in the high frequency region, and the half height widths of the bands are 7.0～14 cm^-1. The area ratio S_z/(S_z+S_A), where S_Z and S_A are the areas of bands 3685 cm^-1 and 3695 cm^-1 respectively, is 0.23. But the surface hydroxyls stretching vibration bands of Maoming kaolinite are in the low frequency region, and the half height widths of the bands are 8.9～15.1 cm^-1. The area ratio S_z/(S_z+S_A) is 0.77. Those data proved that Suzhou kaolinite has lower structure default than Maoming kaolinite and ¹H MAS NMR and Raman spectra are effective method for study of kaolinite structure default.     

Raman spectroscopy of urea and urea-intercalated kaolinites at 77 K

The Raman spectra of urea and urea-intercalated kaolinites have been recorded at 77 K using a Renishaw Raman microprobe equipped with liquid nitrogen cooled microscope stage. The NH2 stretching modes of urea were observed as four bands at 3250, 3321, 3355 and 3425 cm(-1) at 77 K. These four bands are attributed to a change in conformation upon cooling to liquid nitrogen temperature. Upon intercalation of urea into both low and high defect kaolinites, only two bands were observed near 3390 and 3410 cm(-1). This is explained by hydrogen bonding between the amine groups of urea and oxygen atoms of the siloxane layer of kaolinite with only one urea conformation. When the intercalated low defect kaolinite was cooled to 77 K, the bands near 3700 cm(-1) attributed to the stretching modes of the inner surface hydroxyls disappeared and a new band was observed at 3615 cm(-1). This is explained by the breaking of hydrogen bonds involving OH groups of the gibbsite-like layer and formation of new bonds to the C=O group of the intercalated urea. Thus it is suggested that at low temperatures two kinds of hydrogen bonds are formed by urea molecules in urea-intercalated kaolinite.     

IR study of dickite-formamide intercalate, Al2Si2O5(OH)4-H2NCOH

Direct intercalation of formamide (FAM) in dickite occurs spontaneously when samples are treated by ultrason. The X-ray diffraction patterns show that this intercalation increases the d001 spacing from 7.19 to 10.77 A. It is concluded from infrared studies that hydrogen bonds are formed between C=O groups of formamide and inner surface hydroxyls of dickite, indicated by the shift of the hydroxyl bands from 3708, 3654 cm(-1) and 3622 for natural dickite to 3575, 3520, 3450 and 3612 cm(-1) for FAM-intercalated dickite.     

Raman spectroscopy of potassium acetate-intercalated kaolinites at liquid nitrogen temperature

Raman microscopy has been used to study low and high defect kaolinites and their potassium acetate intercalated complexes at 298 and 77 K. Raman spectroscopy shows significant differences in the spectra of the hydroxyl-stretching region of the two types of kaolinites, which is also reflected in the spectroscopy of the hydroxyl-stretching region of the intercalation complexes. Additional bands to the normally observed kaolinite hydroxyl stretching frequencies are observed for the low and high defect kaolinites at 3605 and 3602 cm(-1) at 298 K. Upon cooling to liquid nitrogen temperature, these bands are observed at 3607 and 3604 cm(-1), thus indicating a weakening of the hydrogen bond formed between the inner surface hydroxyls and the acetate ion. Upon cooling to liquid nitrogen temperature, the frequency of the inner hydroxyls shifted to lower frequencies. Collection of Raman spectra at liquid nitrogen temperature did not give better band separation compared to the room temperature spectra as the bands increased in width and shifted closer together.     

Vibrational study of hydrogen bonding and structural disorder in Na2H(SO4)2, K3H(SO4)2 and (NH4)3H(SO4)2 crystals

Infrared and Raman spectra on Na₃H(SO₄)₂, K₃ H(SO₄)₂ and (NH₄)₃ H(SO₄)₂ crystals have been investigated at 300 and 100 K in the 4000 to 30 cm⁻¹ region. An assignment of bands in terms of OH group frequencies and more or less distorted tetrahedra of ammonium and sulphate ions is given. The crystallographic and spectroscopic symmetry and/or dissymetry of OHO hydrogen bonds linking sulphate ions into dimers is discussed using OH group frequencies and the splitting of the v₁ (SO₄) Raman bands as criteria. In the particular case of (NH₄)₃H(SO₄)₁ compound containing several solid phases it can be shown that the room temperature phase (II) is strongly disordered, principally because of an orientational disorder of ammonium ions, and that a progressive ordering takes place with temperature lowering.     

Metal–metal bonding in metal–string complexes M3(dpa)4X2 (M = Ni, Co, dpa = di(2-pyridyl)amido, and X = Cl, NCS) from resonance Raman and infrared spectroscopy

Infrared and Raman spectra for metal–string complexes M₃(dpa)₄X₂ (M = Ni, Co, dpa = di(2-pyridyl)amido, and X = Cl, NCS) are studied. We assign the Ni₃ asymmetric stretching vibration to infrared lines at 304 and 311 cm⁻¹ for Ni₃(dpa)₂Cl₂ and Ni₃(dpa)₂(NCS)₂, respectively. A Raman shift at 242 cm⁻¹ is assigned to the Ni₃ symmetric stretching mode. For Co₃ complexes a line for the Co₃ asymmetric stretching mode appears at 313 and 331 cm⁻¹ for Co₃(dpa)₂Cl₂ and Co₃(dpa)₂(NCS)₂, respectively.