Acidity of montmorillonite pillared by alumina, zirconia and chromia

Acidic properties of Al-, Zr- and Cr- pillared montmorillonites prepared from Jelšovy Potok bentonite (Central Slovakia) have been investigated using temperature-programmed desorption of ammonia. The number of acid sites varied with different interlayer cations from 0.06 to 0.23 mmol g⁻¹. The character of acid sites was similar in the case of Al- and Zr- forms. It is obvious that the chromium analogue contains fewer acid sites, nevertheless, they seem to be stronger compared to Al- and Zr- pillared montmorillonites.     

含过渡金属离子的交联蒙托土交联柱中Keggin结构的作用

利用Keggin结构可以发生同晶取代的性质,合成了含过渡金属离子铬、镍的羟基铝交联蒙托土,并运用XRD、~(27)Al-NMR、UV-DRS、XPS、TPR等方法研究了Keggin结构的作用。结果表明,铬、镍都可以和铝生成具有Keggin骨架结构的羟基共聚体,并以此作柱子支撑着蒙托土的层间。铬的取代反应比镍容易发生。共聚法合成出的羟基镍铝交联蒙托土中镍存在两种状态;过量的金属离子对Keggin结构有较大地破坏;Keggin结构的存在增加了交联蒙托土的热稳定性。     

Comparative Studies of the Micropore Size Distributions of an Alumina Pillared Montmorillonite and a Molecular Sieve Carbon

The aim of this work is to applicate and to compare various analysis methods for the characterization of the microporous structure from nitrogen adsorption at 77 K of an alumina pillared montmorillonite and a molecular sieve carbon. The adsorption potential distribution (X(A)), the Horvath-Kawazoe (HK) method, the Jaroniec-Gadkare-Choma (JGC) one and a numerical algorithm for the reconstruction of the micropore size distribution (MPSD) from the adsorption equilibrium isotherm have been applied. Comparison of all distributions revealed that the molecular sieve carbon shows smaller micropores and smaller structural hetereogeneity than the alumina pillared montmorillonite.     

Synthesis and Characterizations of Hydroxy-aluminum Cross-Linked Montmorillonite

Cross-linked montmorillonite was prepared by reacting homoionic sodium form of bentonite (Na-M) from Istenmezeje (Hungary) with high molecular weight polyhydroxy-aluminum complex. The complex was prepared by controlled hydrolysis of alumina macrocation. The intercalated clay (Na-Al-M) was thermally treated to convert the hydroxy cations to oxide pillars. The pillared products were characterized by X-ray powder diffraction (XRD), Fourie transform infrared spectroscopy (FTIR), (thermogravimetry (TG), differential thermal analysis (DTA) and thermal analysis-mass spectrometry (TA-MS) methods. The specific surface area as well as pore size and pore structure distribution of samples were measured by nitrogen, water and carbon tetrachloride adsorption, and the heat of immersion was also determined. The pillared products were characterized by d(001) reflections of 19 Å, which is stable even at 500°C. The interaction of polymer alumina caused several changes in the obtained FTIR spectra due to the formation of different new bonds. The rate of dehydroxylation of the pillared product is very moderate, the water release occurred in different temperature ranges according to TA-MS results. Dehydration starts at interfaces and at the wall of pores, occurring nearly with uniform rate at 250-500°C. DTA curve indicates the formation of a new phase at 950°C. The obtained surface area of the pillared product by nitrogen adsorption becomes larger (208 m2 g-1) with respect to the non pillared clay, which decreases less than 10% upto 700°C. The pillared sample has a definite pore structure, the quantity of micropores (0-40 Å) decreased with increasing of macropores (>1000 Å). The obtained domestic pillared montmorillonite possesses a high degree of thermal stability and may be used as adsorbent.     

Emanation Thermal Analysis of Intercalated Montmorillonitic clay

Emanation Thermal Analysis (ETA), based on the measurement of the release of radon from previously labelled samples, has been used for 'in-situ’ characterisation of the morphology changes of intercalated montmorillonitic clay. The thermal behaviour of hydroxyaluminium intercalated montmorillonite was monitored in course of the preparation of alumina pillared montmorillonite, making possible to determine optimal temperature for the isothermal treatment of the intermediate product. Moreover, the thermal stability of alumina pillared montmorillonite porous structure was determined from the ETA data. A good agreement of ETA data and surface area, XRD patterns. DTA, and TG resulted was found. This revised version was published online in July 2006 with corrections to the Cover Date.     

氯掺杂二氧化钛柱撑蒙脱土的合成及光催化性能

采用溶胶 凝胶法制备了氯掺杂二氧化钛柱撑蒙脱土催化剂。 利用XRD、SEM、UV-Vis-DRS、光致发光谱(PLS)、N2吸附-脱附和XPS等测试技术对其进行了表征。 结果表明,该催化剂具有明显的锐钛矿相结构,且氯掺杂与二氧化钛柱撑后,蒙脱土的层间结构没有完全被破坏;氯掺杂拓宽了其光吸收范围,在可见光区吸收增强;其带隙能由3.19 eV减小至3.14 eV;氯以阴离子形式存在于TiO2晶格中。 对硝基苯胺降解实验表明,氯掺杂可显著提高二氧化钛柱撑蒙脱土的光催化活性,氯掺杂量为6%(与钛的摩尔比)的催化剂具有较好光催化活性。     

Vanadia impregnated iron-pillared montmorillonite for aniline methylation

Vanadia impregnated iron-pillared montmorillonites with different weight percentages of vanadia have been prepared. Subsequent characterization by XRD, FT-IR, surface area and pore volume measurements was carried out. Acidity was determined by three independent techniques namely thermogravimetric desorption of 2,6-dimethylpyridine, spectrophotometric monitoring of adsorption of perylene and temperature-programmed desorption of ammonia. Conversion of cumene in the vapor phase has been performed as a test reaction of acidity. Aniline methylation was carried out to check the catalytic efficiency of the solids. This revised version was published online in August 2006 with corrections to the Cover Date.     

铝柱撑蒙脱石负载纳米金催化剂的结构表征及其CO催化活性研究

以铝柱撑蒙脱石为载体,用沉积沉淀法在其表面负载金属Au后制备了Au负载铝柱撑蒙脱石高效负载型催化剂。以XRD,TEM,XPS等手段对催化剂的结构进行了表征,并研究了铝柱撑蒙脱石负载前后CO催化氧化活性的变化规律。结果证明,Au是以高度分散的状态均匀分布在铝柱撑蒙脱石载体表面,且以Au0和Au3+的混合价态形式存在。CO催化氧化活性表征结果表明,负载后催化剂的催化活性有了显著提高,且其催化活性随着负载量的增加而不断增强,但当负载量增大到一定程度后,其催化活性不再继续增加,且有所下降。     

锆钇柱撑蒙脱土负载Pd催化剂的催化性能研究

合成了锆钇柱撑蒙脱土(Zr-Y-MMT)载体,并用于丙酮、甲苯和乙酸乙酯的催化氧化。通过XRD、TEM及N₂吸附-脱附技术对Zr-Y-MMT载体和负载Pd催化剂(Pd/Zr-Y-MMT)进行了表征。XRD结果显示,经锆钇柱撑后蒙脱土的层间距由1.27 nm增大至1.78 nm;N₂吸脱附结果表明,经锆钇柱撑后,其比表面积有了很大的增加,由62 m²·g^-1增大至395 m²·g^-1。活性评价结果发现,Zr-Y-MMT载体比Na-MMT有更好的催化活性,其完全氧化丙酮、甲苯和乙酸乙酯的温度分别为320 ℃、350 ℃和290 ℃。此外,当此载体上负载0.1wt%Pd时,其用于完全氧化甲苯的活性有了明显的改进。     

Pillared montmorillonites modified with silver

Alumina, zirconia and titania pillared montmorillonites additionally modified with silver were tested as catalysts of NO reduction with NH₃ or C₂H₄. Ammonia was much more effective reducer of NO than ethylene. The silver containing TiO₂-pillared clay has been found to be the most active catalyst for NO reduction both with NH₃ or C₂H₄. Oxidation of the reducing agents by oxygen limited the NO conversion in the high temperature region. The ammonia and nitric oxide adsorption sites were studied by the temperature programmed desorption methods (TPD). This revised version was published online in July 2006 with corrections to the Cover Date.     

AlFe-pillared clay catalyst for phenol oxidation in water solution

Catalytic wet peroxide oxidation of phenol over AlFe-pillared montmorillonites, with different iron contents, was carried out at room temperature, in a glass batch reactor, under constant airflow and halogen lamp light. At lower concentration (0.5 mg phenol/100 cm³ water) a phenol conversion of 100% was achieved independently of the iron content in pillared clay catalyst. However, at higher phenol concentration (5.0 mg phenol/100 cm³ water) retardation of the catalyst activity was observed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Dehalogenation of Aryl Halides Catalyzed by Montmorillonite Immobilized Bimetal Catalyst in Aqueous System

A novel bisupported bimetal catalyst PVP-PdCl2-FeSO4/Al-Mont-PEG600 was prepared by immobilization of PVP (poly (N-vinyl-2-pyrrolidone)) supported bimetallic catalyst using alumina pillared inartificial montmorillonite as the carrier. This catalyst has good dehalogenation activity and selectivity to aryl halides-o-chlorotoluene in aqueous system in the presence of phase transfer catalyst (PEG) and sodium formate as hydrogen source. The catalyst also shows good reusability.     

Kinetics of 2‐Propanol Dehydration over Montmorillonite Clays and Pillared Montmorillonites

Metal ion exchanged montmorillonites (AlM & CrM) and metal oxide pillared montmorillonite (AlPM & CrPM) were prepared and characterized with XRD, FT‐IR, nitrogen adsorption and TPD of ammonia. The pillaring process results in a remarkable increase of interlayer distance, surface area and acid amount of the catalyst. However, increasing the calcined temperature causes reverse effects for the CrPM catalyst. The acid amount decreases in the order of CrPM200 < CrPM300 < AlPM500 < CrM < CrPM400 ≥ CrPM500 ≥ AlM. In the dehydration of 2‐propanol to propene, the reaction follows first order kinetics and the apparent rate constant is related to the catalyst acid amount. Compensation effect occurs in this reaction over the series of catalysts.     

高热稳定性的铝支撑蒙脱土的制备和表征

通过对传统制备方法的改进，用来自不同的原土，成功地合成了一处高热稳定性的铝支撑蒙脱土，用ＸＲＤ、化学分析、脱吸附分析、ＦＴＩＲ等手段表征了样品。结果表明，这种铝支撑蒙脱土在８００℃下要耐热４ｈ，并有高的比表面积及Ｌ和Ｂ固体酸。     

聚乳酸/氧化锌柱撑皂石纳米复合材料制备与性能及结构表征

通过微波水解法制备了ZnO柱撑皂石,并以其为加工助剂制备了聚乳酸(PLA)/ZnO柱撑皂石纳米复合材料.通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、对ZnO柱撑皂石及PLA/ZnO柱撑皂石纳米复合材料的结构进行了表征,并对其力学性能和热稳定性能进行了测试.微观结构分析表明,ZnO柱撑皂石呈现剥离状,并均匀分散在PLA基质中.力学性能研究表明0.3%ZnO柱撑皂石的加入有助于改善PLA复合材料的断裂伸长率.SEM分析表明PLA复合材料的断面发生明显改变,表现良好韧性;DSC结果显示纳米ZnO柱撑皂石可以降低复合材料的玻璃化转变温度、结晶温度,有助于提高PLA复合材料的结晶度,与XRD分析相吻合;热重分析表明ZnO柱撑皂石可以提高PLA复合材料的热稳定性.测试结果表明,ZnO柱撑皂石在PLA基质中起到了异相成核的作用,促进了PLA基质的结晶.     

Investigation of structure and thermal stability of surfactant-modified Al-pillared montmorillonite

For combining the properties of organoclays and pillared clays, inorganic–organic clays have attracted much attention in recent years. In this study, Al Keggin cation pillared montmorillonites (Al-Mts) were first prepared and parts of Al-Mts were calcined at different temperatures (C-Al-Mts). The inorganic–organic montmorillonites were synthesized by intercalating Al-Mts and C-Al-Mts with the cationic surfactant, hexadecyltrimethyl ammonium bromide (HDTMAB). The products were characterized by X-ray diffraction, X-ray fluorescence, and simultaneous thermogravimetric analysis. For HDTMAB-modified uncalcined Al Keggin cation pillared montmorillonites (H-Al-Mts), the basal spacing increased with the increment of surfactant loading level, but the Al content of H-Al-Mts decreased simultaneously, indicating that the intercalated surfactant replaced some Al Keggin cations in the interlayer space. However, in the case of C-Al-Mts, the interlayer spaces could not be further expanded after surfactant modification, implying that the neighboring montmorillonite layers were “locked” by the aluminum pillars which were formed by dehydroxylation of Al Keggin cation pillars during thermal treatment. The thermal stability of HDTMAB-modified C-Al-Mts (H-C-Al-Mts) was much better than that of H-Al-Mts. The major mass loss of H-C-Al-Mts occurred at ca. 410 °C, corresponding to decomposition of intercalated surfactant cations. In contrast, H-Al-Mts displayed two mass loss temperatures at ca. 270 and 410 °C, corresponding to the evaporation of surfactant molecules and the decomposition of surfactant cations in the interlayer space, respectively.     

柱撑杂多阴离子粘土的合成及表征

采用水热合成及离子交换法将Keggin结构三铁九钨镓酸盐杂多阴离子GaW9Fe3（H2O）3嵌入Zn2Al型阴离子粘土层间，得到了新型层柱状微孔材料Zn2Al－GaW9Fe3．用元素分析、XRD、IR、XPS等手段对产物的组成和结构进行了表征．结果表明，杂多阴离子嵌入Zn2Al型阴离子粘土层间，使柱撑杂多阴离子粘土具有1．0nm的通道高度．     

Influence of Drying and Calcination on Remaining Amount and Immobile Character of Titanium on Titanium‐pillared Montmorillonite

Remove of titanium (Ti) from titanium‐pillared montmorillont (TIPM) is not expected during its application as adsorbent and photocatalyst, etc. But studies on immobilization of Ti on TIPM are seldom reported. In this work, TIPM was synthesized from TiCl₄ and Na⁺‐montmorillont (Na⁺‐MMT). Then the prepared TIPM was heated at different temperatures (100, 240 and 450°C) to yield three TIPM samples (TIPM1, TIPM2, and TIPM3). Inductively coupled plasma optical emission spectrometer (ICP‐OES) was used to determine the effect of heating temperature on the remaining amount of Ti on TIPMs. A two‐step treatment method which is often used in the pretreatment and application of TIPM was developed to investigate the immobile character of Ti on TIPMs. X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), N₂ adsorption/desorption isotherm, thermogravimetric analysis and differential scanning calorimetry (TG‐DSC) were also used to characterize TIPMs before and after the treatment. The results show that with an increase in heating temperature, the amount of Ti species remained on TIPM decreases gradually and Ti immobilization is strengthened on TIPM. For TIPM3, less than 2% Ti is removed from TIPM3 after the treatment required to simulate the practical conditions of TIPM in its application, while those of TIPM1 and TIPM2 are 6.6% and 8.4%, respectively. The reason may be that when TIPM is heated, Ti species intercalated into MMT become chemically bonded with the framework of MMT and partially migrate into the layer structure, which make Ti immobile on TIPM firmly during the treatment process.     

Ni^2—交换蒙脱石中的镍物种及焙烧温度影响研究

对一组自制Ｎｉ＾２＋交换蒙脱石样品中镍物种的存在在形及焙烧温度影响进行了ＴＰＲ和ＸＲＤ考察结果表明，样品中镍负载量等于或小于Ｎｉ＾２＋的交换量时，镍主要以难还原听可交换性阳离子Ｎｉ（ＯＨ）＾ｑ＋ｘ和易还原的自由态镍Ｎｉ（ＯＨ）２或ＮｉＯ两种形式存在。     

Synthesis and Characterization of New Material——La/Zr/MMT Employed in Acetone Oxidation

A new material of zirconium pillared montmorillonite added with lanthanum （denoted as La/Zr/MMT） was prepared for acetone oxidation. Surface properties of the catalysts were investigated by means of XRD, TEM, TG-DTA and BET methods. The XRD result indicated that the interlayer space of the montmorillonite was enlarged from 1.57 to 4.85 um after the treatment with zirconium pillaring and the addition of lanthanum. N2 adsorption-desorption result showed that by the process of zirconium pillaring, the specific surface area of the sample was increased to 128.0 m^2/g, which was two times almost as large as pure montmorillonite. Simultaneously, the thermal stability was also enhanced. The activity of the new material on the total oxidation of acetone was investigated, and the results indicated that the catalytic activity of the montmorillonite was greatly improved. Over the sample of La/Zr/MMT, the T98 of acetone was obtained at 350 ℃, while it needs 400 ℃ over the pure montmorillonite. After 0.1% Pd was supported on the sample of La/Zr/MMT, the T98 decreased from 350 to 280 ℃, indicating the montmorillonite is a promising material for the control of some types of the volatile organic compounds such as acetone.