Preparation of rhodium–phyllosilicate catalysts without leaching in liquid-phase 1-hexene hydrogenation

Rhodium catalysts have been prepared on palygorskite and montmorillonite (clay) supports by reduction with hydrogen (1 atmosphere) at room temperature of a cationic organometallic rhodium compound anchored to the support. The activity of these catalysts for the hydrogenation of liquid-phase 1-hexene remains constant with increase of prehydrogenation time and with re-use for several runs. No rhodium leaching is observed.     

Combined effects of clay modifications and compatibilizers on the formation and physical properties of melt‐mixed polypropylene/clay nanocomposites

The melt mixing technique was used to prepare various polypropylene (PP)‐based (nano)composites. Two commercial organoclays (denoted 20A and 30B) served as the fillers for the PP matrix, and two different maleated (so‐called) compatibilizers (denoted PP‐MA and SMA) were employed as the third component. The results from X‐ray diffraction (XRD) and transmission electron microscope (TEM) experiments revealed that 190 °C was an adequate temperature for preparing the nanocomposites. Nanocomposites were achieved only if specific pairs of organoclay and compatibilizer were simultaneously incorporated in the PP matrix. For example, PP/20A(5 wt %)/PP‐MA(10 wt %) and PP/30B(5 wt %)/SMA(5 wt %) composites exhibited nanoscaled dispersion of 20A or 30B in the PP matrix. Differential scanning calorimetry (DSC) results indicated that the organoclays served as nucleation agents for the PP matrix. Generally, their nucleation effectiveness increased with the addition of compatibilizers. The thermal stability enhancement of PP after adding 20A was confirmed with thermogravimetric analysis (TGA). The enhancement became more evident as a suitable compatibilizer was further added. However, for the 30B‐included composites, thermal stability enhancement was not evident. The dynamic mechanical properties (i.e., storage modulus and loss modulus) of PP increased as the nanocomposites were formed; the properties increment corresponded to the organoclay dispersion status in the matrix. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4139–4150, 2004     

Brominated poly(isobutylene‐co‐para‐methylstyrene) (BIMS)‐clay nanocomposites: Synthesis and characterization

In this work, preparation and properties of different nanoclays modified by organic amines (octadecyl amine, a primary amine, and hexadecyltrimethylammonium bromide, a tertiary amine) and brominated polyisobutylene‐co‐paramethylstyrene (BIMS)‐clay nanocomposites are reported. The clays and the rubber nanocomposites have been characterized with the help of Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). The X‐ray diffraction peaks observed in the range of 3 °–10 ° for the modified clays disappear in the rubber nanocomposites. TEM photographs show predominantly exfoliation of the clays in the range of 12 ± 4 nm in the BIMS. In the FTIR spectra of the nanocomposites, there are common peaks of virgin rubber as well as those of the clays. Excellent improvement in mechanical properties like tensile strength, elongation at break, and modulus is observed on incorporation of the nanoclays in the BIMS. Structure‐property correlation in the above nanocomposites is attempted. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4489–4502, 2004     

Dehydration and dehydroxylation of reduced charge montmorillonite

Reduced charge montmorillonites (RCM) were prepared by the thermal treatment of lithiumsaturated montmorillonite. Samples prepared by mild thermal treatment with lithium contained more water sorbed than the original montmorrilonite. When RCMs were prepared, part of the lithium cations reacted with hydroxyl groups in the octahedral sheet and released protons, which reacted with the structure. Acid treatment probably enhanced the surface area. which was reflected in the amount of water sorbed. Deprotonation of hydroxyl groups was proved by the measurements of the ignition loss. The heating of lithium saturated montmorillonite at higher temperatures brough about the collapse of the interlayers and a decrease in the amount of water sorbed.     

Electrochemical characterization of composite membranes based on crown-ethers intercalated into montmorillonite

Oxyethylene macrocyclic compounds (crown-ethers) act as ligands of intracrystalline cations of certain layered silicates as montmorillonites. Stable intercalation materials are formed which are used to prepare organic-inorganic membranes by encapsulating these intercalation compounds with a poly-butadiene thin coating. Electrochemical Impedance Spectroscopy (EIS) is used to study the resulting composite membranes in contact with aqueous electrolytes. From the impedance plots, the ionic resistance of the membranes is obtained. The thickness of the polybutadiene coating is an important factor determining the ability of ions to pass across the membrane. Marked differences in the ionic resistance are observed as a function of the nature of the interlayer macrocyclic compound. For non-intercalated montmorillonite membranes, the ionic resistance is strongly reduced, whereas for some crown-ether intercalated materials such as 18-crown-6 and dibenzo 24-crown-8, iono-selective membranes are obtained. Concerning the nature of the electrolyte, cations exhibiting greater hydration energies show higher difficulties to pass through the membrane and, consequently, the ionic resistance increases.     

Insertion of benzothiazolium compounds into montmorillonite interlayers

Benzothiazolium compounds exhibit pronounced antimicrobial activities and stimulation effects on plant growth. When applied to fields they can pollute soil colloids. In contact with the soil they can potentially interact with a clay fraction giving rise to clay organocomplexes. Model intercalation complexes were prepared using monoionic montmorillonite and a variety of water-soluble benzothia zolium salts. It was found that the adsorption into the silicate interlayer space proceeds via a cation exchange process. Substantial differences were observed in the extent of the reaction between non-substituted andN-substituted species. The sulphur atoms present in the benzothiazolium molecules repel the surface oxygen atom: this is considered to be the factor responsible for prevention of insertion of the guest cations perpendicular to the layers.     

On the effect of montmorillonite in the curing reaction of epoxy nanocomposites

The procedure for the fabrication of epoxy-based polymer layered silicate nanocomposites is important in respect of the nanostructure that is developed. To further our understanding of this, the influence of an organically modified clay (montmorillonite, MMT) on the curing kinetics of an epoxy resin has been studied by differential scanning calorimetry. Clay loadings of 10 and 20 mass% are used, and isothermal as well as dynamic cures have been investigated. For both cure schedules the effect of the MMT is to advance the reaction. Kinetic analysis yields values for the activation energy, but shows that the reaction cannot be described simply by the usual autocatalytic equation. The glass transition of the cured nanocomposites is lower than that for the cured neat resin, a result that is attributed to homopolymerisation taking place in addition to the epoxy–amine reaction.     

含锆层柱蒙脱石对1,2,4三甲基苯歧化反应的催化作用

用离子共聚法合成了硅锆层柱蒙脱石（ＳｉＺｒＰＩＬＭ）和铁锆层柱蒙脱石（ＦｅＺｒＰＩＬＭ），考察了它们对１，２，４三甲基苯（１，２，４ＴｒＭＢ）歧化反应的催化性能．１，２，４ＴｒＭＢ在催化剂样品上可发生歧化反应和异构化反应，歧化反应选择性达８０％以上．随着催化剂预处理温度的提高，１，２，４ＴｒＭＢ转化率下降，歧化反应选择性和四甲基苯（ＴｅＭＢ）中１，２，４，５ＴｅＭＢ含量则升高．催化剂对１，２，４ＴｒＭＢ歧化反应有择形催化作用，１，２，４，５ＴｅＭＢ和间二甲苯、邻二甲苯为主要产物，并且其含量偏离其热力学平衡组成，ＴｅＭＢ中１，２，４，５ＴｅＭＢ的含量在８５％以上．     

载铂铝交联蒙脱土的烷烃芳构化特性──Ⅰ．载铂铝交联蒙脱土对烷烃的择形芳构化作用

对比考察了Ｐｔ／ＫＬ沸石，Ｐｔ／Ａｌ２Ｏ３和载铂铝交联蒙脱土（Ｐｔ／Ａｌ－ＣＬＭ）催化剂对不同碳原子数烷烃的芳构化特性．脉冲微反的评价结果表明：Ｐｔ／Ａｌ－ＣＬＭ比Ｐｔ／Ａｌ２Ｏ３和Ｐｔ／ＫＬ具有较高的转化ｎ－Ｃ８，ｎ－Ｃ９为其对应芳烃的选择性，在转化ｎ－Ｃ８时，产物中的间、对位二甲苯收率很高，而转化ｎ－Ｃ９时有高的正丙苯收率．采用１２９Ｘｅ－ＮＭＲ、ＸＲＤ和孔分布测定考察了Ｐｔ／Ａｌ－ＣＬＭ和Ｐｔ／ＫＬ、Ｐｔ／Ａｌ２Ｏ３之间孔结构的差异．结果表明：由于ｎ－Ｃ８，ｎ－Ｃ９在反应过程中其过渡态的极限尺寸与Ｐｔ／Ａｌ－ＣＬＭ０．９ｎｍ左右的层间域相匹配，因而它对ｎ－Ｃ８，ｎ－Ｃ９具有择形芳构化作用．