Preparation and characterization of manganese- and samarium-manganese-alumina pillared montmorillonites

A Na-montmorillonite was intercalated with manganese- and samarium-manganese-aluminium solutions. The pillared montmorillonites were characterized by X-ray diffraction and nitrogen adsorption. The presence of manganese and samarium-manganese citrates in the intercalation process modify the distance between the clay sheets and the microporous structure of the pillared montmorillonites.     

Catalytic activity and acidity of Al pillared clays and zeolites in different hydrocarbon reactions

In comparison with zeolites, a variety of Al pillared clays did not prove as promising cracking catalysts, possibly because their Br?nsted sites are hidden. In the less demanding double bond shift isomerization, both catalyst types were comparable probably due to the presence of Lewis sites on both catalysts.     

Catalytic characterization of pillared clays through toluene methylation reaction

Pillared clays (PILCs) with Al and Zr oxide pillars were studied in terms of their structure and texture. The catalytic properties of the samples were evaluated through toluene methylation reaction. As comparison material, a commercial zeolite HZSM-5 was used. The toluene conversion at short time-on-stream over PILCs, although smaller than the value obtained with HZSM-5, attains values of 37 (molar %). In all cases the reaction products are a mixture of xylene, ethyltoluene and trimethylbenzene isomers. All samples present higher selectivity to xylene isomers, which are the primary products. For Zr pillared clay, the percentage of these isomers is the highest.     

Acidity and aniline alkylation activity of oxides and supported vanadia oxides

Aniline alkylation activity of simple oxides and supported vanadia oxides are compared from the point of view of acidity and vanadia-support interaction.

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IICT communication No. 2915     

Adsorption and characteristics of base-treated pillared clays

The effect of base treatment on the cation exchange capacity (CEC) of pillared clays and their adsorption isotherms for Cu²⁺, Cr³⁺ and Pb²⁺ have been investigated. Results indicate that although the CEC of pillared clays are only about 15% of that of the parent clays, a large fraction of the native clays CEC may be recovered by treatment with base. The fraction of the CEC recovered depends upon the base strength, its concentration, and the temperature. Contrary to previous suggestions the mechanism of recovery is related to the destruction of pillars which is accompanied by the loss of surface area. It is possible under conditions specified to prepare these base treated pillared clays as a new class of useful, regenerable adsorbent for heavy metal adsorption from aqueous solution.     

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.     

Thermal stability and flammability performance of polypropylene composites with silica pillared montmorillonites

In present work, silica pillared montmorillonite material (C‐SiO₂‐OMT) was prepared via the sol–gel method, and the influence of the powder on thermal stability and flammability performance of polypropylene (PP) composites was investigated. Characterization of C‐SiO₂‐OMT, elucidated with X‐ray diffraction, transmission electron microscopy, and N₂ adsorption–desorption, suggested that the powder had a mesoporous lamellar structure with high specific surface area and mesoporous volume. The formation of porous structure of C‐SiO₂‐OMT was more conducive than organically modified montmorillonite (OMT) to slowing the volatilization of pyrolytic products generated during thermal degradation process, which led to PP/C‐SiO₂‐OMT microcomposite show better thermal stability than PP/OMT nanocomposite at high temperature range. Flammability properties of these polymer materials evaluated by microscale combustion calorimetry, and cone calorimetry showed a contrary tendency, but C‐SiO₂‐OMT holds high promise to reduce the smoke yield. Copyright © 2013 John Wiley & Sons, Ltd.     

Depollution of uranyl polluted waters using pillared clays

This paper reports on the use of clays pillared with copper polyhydroxycations in the depollution of waters polluted with radioactive elements. The pillared clays have very good surface properties which recommend them for use in cationic depollution. The article includes a kinetic study on the depollution of radioactive polluted waters, studying the influence of temperature on the process. The pillared clays are prepared from Romanian clay originally from Valea Chioarului deposits; the experiments have used an autochthonous material in an unconventional performant depollution technology.     

Acidity dependence of aniline alkylation activity over modified alumina+

-Al₂O₃ is modified by lithium additions and by calcination. Aniline alkylation activity over modified alumina is correlated with the Al–OH group population responsible for the acidity.

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-Al₂O₃ . Al–OH, .

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IICT Communication No.: 2824     

新型层柱化合物合成、表征及催化活性

将含过氧铌一、三取代钨硅、钨磷过氧杂多阴离子利用离子交换法嵌入Zn2Al类水滑石中制得层柱化合物,利用XRD,IR,UV等方法对产物的结构进行了表征。结果表明在层柱化合物中过氧杂多阴离子仍然保持Keggin结构,并且过氧键没被破坏。层柱化合物在酯化反应中显示优良的催化性能。     

过氧杂多阴离子型层柱化合物的合成、表征及催化活性

通过离子交换法,将含Zr过渡金属离子1,3取代钨硅、钨磷过氧杂多酸盐嵌入Zn2Al类水滑石中,获得了层柱化合物,并用XRD,IR,UV等手段对产物的结构进行了表征.结果表明过氧杂多阴离子进入水滑石层间后,水滑石的层间距从0.92增大到1.47 nm,且过氧链没被破坏.层柱化合物在酯化反应中显示优良的催化性能.     

Photodegradation of dye pollutants on TiO_2 pillared bentonites under UV light irradiation

TiO2 pillared bentonite samples dried under different conditions are used to degrade 2,4-dichlorophenol and orange II under UV light irradiation. The supercritical dried sample exhibits a high activity for the photodegradation of 2,4-dichlorophenol and orange II due to its structural features. TOC and COD are measured during the degradation of 2,4-dichlorophenol under UV light irradiation using P25 and TiO2 pillared bentonite samples dried under different conditions. The clay-based catalysts can be readily separated by filtration or sedimentation.     

铁-锆交联蒙脱土的制备和结构表征

我们首次合成了铁锆复合柱交联蒙脱土, 并用XRD, 比表面及孔径测定和Mossbauer谱学等方法进行了表征。结果表明, 铁锆交联蒙脱土比表面增大为原土的三倍以上, 其层间距可达0.88nm(d001=1.84nm)。热稳定性明显高于单一Fe柱交联蒙脱土。在500℃加热后层间距保持0.63nm~0.71nm。但由于铁柱的坍塌造成微孔减少, 比表面明显下降。Mossbauer谱研究表明, 500℃焙烧单一铁柱转变为α-Fe~2O~3, 而Fe-Zr-PILC中铁仍以超顺磁Fe^3^+存在, 单一铁柱的铁组分在400℃可还原为金属铁, 而铁锆混合柱交联蒙脱土中由于铁与锆之间存在较强的相互作用, 450℃氢气气氛中铁组分仍不能还原为金属铁。     

Site of alkylation of N-methyl- and N-ethylaniline in the gas phase: a tandem mass spectrometric study

N-Methylaniline (NMA) was ethylated and N-ethylaniline (NEA) was methylated under chemical ionization conditions using C₂H₅I and CH₃I, respectively, as reagent gases. The structures of the resulting m/z 136 adduct ions have been probed using metastable ion and collision-induced dissociation (CID) methods. From the similarity of the spectra obtained and from the presence of structure-diagnostic ions at m/z 59 (CH₃NHC₂H₅^+•) and m/z 44 (CH₃NHCH₂⁺), it is concluded that predominantly N-alkylation occurs in both systems. This interpretation was aided by the use of C₂D₅I and CD₃I as reagents. Adduct ions of m/z 136 were also formed by ethylation of the isomeric toluidines and by methylation of the ring-ethylanilines. The resulting CID mass spectra were distinctly different from those obtained for the m/z 136 ions obtained by alkylation of NMA and NEA. Protonation of N-ethyl-N-methylaniline using CH₃C(O)CH₃ as Brønsted acid reagent produced an m/z 136 species whose CID mass spectrum also featured intense ion signals at m/z 59 and 44. This observation led to the conclusion that protonation with acetone as reagent results, in this case, in dominant N-protonation. However, the CID mass spectrum of the m/z 136 ion formed when CH₃OH was the protonating agent featured a weak signal at m/z 44 and no signal at m/z 59. Hence it was concluded that the latter m/z 136 ion contains a larger contribution from the ring-protonated adduct. Copyright © 2004 John Wiley & Sons, Ltd.     

Acidity effects of Hβ zeolite on olefin alkylation of thiophenic sulfur in gasoline

Olefin alkylation of thiophenic sulfur process was carried out in model gasoline, using Hβ zeolites with different Si/Al2 ratios as catalysts. In particular, the influence of acid properties of Hβ zeolites on its catalytic ability for the thiophene alkylation, xylene alkylation and hexene oligomerization was investigated. The results showed that the acidity of the Hβ zeolite was increased with the decrease of Si/Al2 ratio, but its catalytic ability was not always increased. In fact, it reached the maximal catalytic ability at Si/Al2 ratio of 66, and under the reaction conditions of 60 ℃, 1.5 MPa, WHSV 3.0 h^-1 and time on stream 2 h. At the ratio, the conversion of thiophene, xylene, and oligomerized hexene were 96.6%, 2.7% and 2.8%, respectively. An optimal Si/Al2 ratio exists for the catalytic performance of Hβ zeolite. By investigating the coke deposition of the used Hβ zeolite catalysts, it has been found that the optimal Si/Al2 ratio is attributed to the combined effect of the carbocation activation capability and the hydrogen transformation capability of the Hβ zeolite catalyst.     

UV light‐mediated alkylation of inorganic selenium

In the presence of low molecular weight organic acids (formic, acetic, propionic and malonic), inorganic selenium(IV) is converted by UV irradiation to volatile selenium carbonyl, dimethylselenide and diethylselenide, depending on the acid used. Gas chromatography–mass spectrometry analysis of the volatile products shows that, in 0.7 M formic acid solution, approximately 60–70% (v/v) SeH₂ and 30–40% (v/v) SeCO are formed. The presence of nitrate ion appears to increase threefold the formation of SeCO while completely suppressing formation of SeH₂. Copyright © 2003 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.     

烷基化催化剂表面酸性及催化性能的动力学研究

在确定关联升温速率、脱附峰温和脱附峰覆盖率的程序升温脱附动力学模型的基础上，通过TPD实验和模型参数估值，建立了表征催化剂酸密度、酸强度及强度分布情况的方法。研究表明，随着活化温度的提高，固体酸催化剂表面酸中心强度分布先变宽后趋于均匀，350?℃活化催化剂的强度分布最宽；催化剂表面酸强度和酸密度随活化温度提高均呈先增大后降低、分别在350 ℃和250 ℃活化温度达到极大值的变化规律。催化剂酸性与催化性能关联的结果表明，随着活化温度的提高，烷基化反应速率常数与总脱附量的变化趋势相同，而催化剂失活速率常数与脱附活化能变化趋势相同；催化剂活性稳定性随其酸强度的增大而变差，催化剂活性与催化剂酸量和酸强度有关。     

Electrochemical copolymerization of thiophene and aniline

In this study homopolymer, copolymer, and composites of aniline and thiophene were synthesized in nitrogen atmosphere by using TEATFB (Tetraethyl ammonium tetrafluoroborate) and Lithium perchlorate as supporting electrolytes. In order to analyze their structure and characteristics, IR spectrums of the samples were taken and thermogravimetric analysis (TGA) was applied. Also, the samples were photographed under scanning electron microscope (SEM) for microstructure analysis and their electrochemical properties were observed and conductivities were obtained by four probe method. Homopolymerization and copolymerization reactions were carried out in two different solvents viz. acetonitrile and benzonitrile in order to see the solvent effect on polymerization. However, changing the solvent was found to have no significant effect on the resulting properties. It was concluded that changing the supporting electrolyte caused a structural difference in the resulting homopolymer. It also affects the properties considerably. During the bilayer preparation changing the coating turn led to variations in the properties of the samples. When polythiophene (PT) was coated with polyaniline (PA), the resulting system was a composite. However, in coating PA with PT the system was identified to be a copolymer. © 1996 John Wiley & Sons, Inc.     

Solar photooxidation of azo dye over mixed (Al-Fe) pillared bentonite using hydrogen peroxide

Summary The mixed Al-Fe pillared bentonite (Al/Fe-B) was tested as a heterogeneous catalyst for the photo-Fenton discoloration of azo dye X-3B under solar light irradiation. The structural characteristics of the catalyst were examined by XRD, BET, and TEM. The results indicate that the heterogeneous photo-Fenton process employing the Al/Fe-B as catalyst exhibits higher photo-catalytic activity compared to its corresponding homogeneous photo-Fenton process. The amount of Fe ions in solution leaching from the Al/Fe-B is less than 0.26% of the total iron content in the catalyst.     

Reductive alkylation of p-benzoquinone using mixed organoboranes

Mixed organoboranes based on diphenyl- or dimethylalkylboranes transfer the alkyl group in the reductive alkylation of p-benzoquinone to form the alkylhydroquinones in very high yields. The auxiliary groups do not transfer or have a low migratory aptitude. Primary and secondary alkyl groups are transferred with retention of regio- and stereochemistry to the hydroquinone. O-Alkylation is the major product with tertiary and secondary groups with steric bulk in proximity to the site of attachment. The presence of metal salts, such as magnesium, results in reduction to the unsubstituted hydroquinone. This reaction makes the first practical route to alkylhydroquinones via organoboranes.