Application of new methods to the kinetic study of diazotization and azo coupling reactions

New applications are described of the direct injection enthalpimetry (DIE method) and analysis of electrochemical currentless potential-time dependences to the kinetic study of the diazotization and azo coupling reactions. Basic principles of the methods used are given together with methods of treatment of the results obtained from the measurements of selected reaction systems. Applicability of the methods described is documented by a number of experimental results obtained in the field of both homogeneous and heterogeneous reactions.     

Rapid and efficient diazotization and diazo coupling reactions on silica sulfuric acid under solvent-free conditions

A convenient, rapid, one-pot method for the synthesis of azo dyes has been developed by the sequential diazotization–diazo coupling of aromatic amines with NaNO₂, silica sulfuric acid and coupling agents under solvent-free conditions at room temperature. Using this method, several types of aromatic amine, containing electron-withdrawing groups as well as electron-donating groups, were rapidly converted to the corresponding azo dyes in good yield. The ensuing aryldiazonium salts supported on silica sulfuric acid (aryl diazonium silica sulfates), ArN₂^+?OSO₃–SiO₂, were sufficiently stable to be kept at room temperature in the dry state. The use of mild reaction conditions and an inexpensive procedure are further advantages of this method.     

Hydrotalcite-like anionic clays in catalytic organic reactions

Hydrotalcite-like anionic clays (HTs; or layered double hydroxides, LDHs) can be used as precursors to mixed oxides, but their catalytic potential reaches much further. This review demonstrates that HTs can be successfully applied in a broad spectrum of organic reactions, with advantages such as improved activity, selectivity, metal dispersion, less waste production, and an improved recuperation of immobilized catalysts. HTs can be used in the as-synthesized form or after different pretreatments. The HT as such is a solid base or, depending on the elemental composition of its octahedral layers, may have redox properties. Specific metals can be incorporated either as a cation in the octahedral layer or as an anion via exchange. The anion-exchange strategy is especially successful in the context of heterogenizing homogeneous catalysts. A particular advantage for base catalysis is that the number and strength of the basic sites can be tuned precisely to a specific reaction. HTs are excellent materials to design bifunctional redox-base catalysts or to control the acid-base properties around a heterogenized metal complex. Potential applications of HTs range from the production of large-scale basic chemicals to the synthesis of small-scale specialty chemicals.     

Hydrotalcite-like anionic clays in catalytic organic reactions

Hydrotalcite-like anionic clays (HTs; or layered double hydroxides, LDHs) can be used as precursors to mixed oxides, but their catalytic potential reaches much further. This review demonstrates that HTs can be successfully applied in a broad spectrum of organic reactions, with advantages such as improved activity, selectivity, metal dispersion, less waste production, and an improved recuperation of immobilized catalysts. HTs can be used in the as-synthesized form or after different pretreatments. The HT as such is a solid base or, depending on the elemental composition of its octahedral layers, may have redox properties. Specific metals can be incorporated either as a cation in the octahedral layer or as an anion via exchange. The anion-exchange strategy is especially successful in the context of heterogenizing homogeneous catalysts. A particular advantage for base catalysis is that the number and strength of the basic sites can be tuned precisely to a specific reaction. HTs are excellent materials to design bifunctional redox-base catalysts or to control the acid–base properties around a heterogenized metal complex. Potential applications of HTs range from the production of large-scale basic chemicals to the synthesis of small-scale specialty chemicals.     

3-[(4'-羧基)-2'-喹啉基]酚酮的合成及溴代和偶联反应

报道了 Pfitzinger喹啉合成法在酚酮领域中的首次应用。 3-乙酰基酚酮 ( 1 )在氢氧化钾存在下与靛红反应 ,得到了喹啉基取代的酚酮化合物 3- [( 4′-羧基 ) - 2′-喹啉基 ]酚酮 ( 2 ) ;化合物 2经溴化反应得到双溴代产物5 ,7-二溴 - 3- [( 4′-羧基 ) - 2′-喹啉基 ]酚酮 ( 3) ;化合物 2经偶联反应得到 5位偶联产物 5 -苯偶氮基 - 3- [( 4′-羧基 ) -2′-喹啉基 ]酚酮 ( 4)。化合物 2、3、4为尚未见文献报道的新化合物 ,它们的结构经红外光谱、核磁共振谱及元素分析予以证实。     

改性柱撑黏土用于烟气脱硝的研究进展

柱撑黏土（PILC）由于其结构可控的二维层状多孔特性,在选择性催化还原（SCR）技术中已得到广泛应用。本文综述了近年来PILC和改性PILC的结构特性、化学性质、层间掺杂活性物质及脱硝效率的研究成果,分析表明,经过添加不同活性物质改性后的PILC具有更高的比表面积、更大的层间距和良好的耐热稳定性等特点,催化剂的表面活性及催化活性得到明显的提高,对NO_x具有更好的脱除效果。此外,本文还介绍了基于密度泛函理论（DFT）的改性PILC的吸附机理研究进展。由此指出,对PILC的改性和理论的深入研究,为设计和改造高效SCR脱硝催化剂具有重要意义,而将密度泛函理论引入PILC改性及脱硝机理研究中也为PILC的改性研究提供了新的理论思路。     

Compression and permeability relationships in high water content clays

Storing contaminant soils, such as dredge materials, sludge and mine tailings, and reclaiming contaminant soil storage areas back into the economy has arisen as an important economical and environmental problem in today's world. The scientific studies in the last thirty years have revealed critical new information regarding the deformation behavior of high water content soils.In this article relationships between material properties used in constitutive models for self-weight and/or surcharge loaded high water content (slurry) clays and their index properties are investigated. For this purpose three different kinds of clays in a slurry consistency are subjected to seepage induced consolidation in an experimental setup. Information obtained from these experiments, together with information already in literature, is used to investigate the relationships between the index properties and the consolidation constitutive model parameters. The relationships obtained from the experiments are then utilized to predict the self-weight consolidation of Halic (Golden Horn) dredge materials. These predictions are then compared with the results of numerical analysis and found to be in good agreement.     

Application of nickel‐catalysed reduction and azo dye reactions for the determination of tinidazole

A macrocyclic Schiff base nickel(ii ) complex was synthesised via template synthesis by treating acetylacetone with 1,8‐diaminonaphthalene in the presence of nickel chloride in a 2:2:1 ratio in an aqueous methanol solution at 75 °C for 30 min. It was characterised by elemental, infrared, proton and carbon nuclear magnetic resonance and mass spectral analysis and used as a catalyst for the reduction of tinidazole. The reduced tinidazole was treated with nitrous acid and 2‐naphthol and the resulting azo dye was used for the spectrophotometric determination of the reduction product of tinidazole.     

Nanoparticles of organosilane-based nitrite ionic liquid immobilized on silica for the diazotization of aniline derivatives and subsequent synthesis of azo dyes

Imidazolium based nitrite ionic liquid containing trimethoxysilyl group was prepared from the reaction of N-methylimidazole and (3-chloropropyl) trimethoxysilane. This ionic liquid was immobilized on silica covalently to give nanoparticles with the imidazolium nitrite moiety remaining intact. The diazotization reaction was performed as a model reaction to examine the activity of these nanoparticles as a nitrosonium source. Excellent performance was exhibited in the diazotization reaction of various aniline derivatives in the presence of HCl under mild heterogeneous conditions (room temperature and short reaction time). In-situ coupling of diazonium salts to a range of tertiary anilines, phenols and naphthols afforded the requisite azo dyes in good yield, using standard experimental procedures.     

Crown ether‐modified clays and their polystyrene nanocomposites

Crown ether‐modified clays were obtained by the combination of sodium and potassium clays with crown ethers and cryptands. Polystyrene nanocomposites were prepared by bulk polymerization in the presence of these clays. The structures of nanocomposites were characterized by X‐ray diffraction and transmission electron microscopy. Their thermal stability and flame retardancy were measured by thermogravimetric analysis and cone calorimetry, respectively. Nanocomposites can be formed only from the potassium clays; apparently the sodium clays are not sufficiently organophilic to enable nanocomposite formation. The onset temperature of the degradation is higher for the nanocomposites compared to virgin polystyrene, and the peak heat release rate is decreased by 25% to 30%.     

Polymer nanocomposites from modified clays: Recent advances and challenges

Since the end of the last century, the discovery of polymer nanocomposites and their ever-expanding use in various applications has been the result of continuous developments in polymer science and nanotechnology. In that regard, progress in developments on the use of modified natural and synthetic clays for designing polymer nanocomposites is presented herein. The modified clays used in composite preparation include natural clays such as montmorrilonite, hectorite, sepiolite, laponite, saponite, rectorite, bentonite, vermiculite, biedellite, kaolinite, and chlorite, as well as synthetic clays including various layered double hydroxides, synthetic montmorrilonite, hectorite, etc. The preparation, structure and properties of polymer nanocomposites using the modified clays are discussed. Even at a low loading, these composites are endowed with remarkably enhanced mechanical, thermal, dynamic mechanical, adhesion and barrier properties, flame retardancy, etc. The properties of the nanocomposites depend significantly on the chemistry of polymer matrices, nature of clays, their modification and the preparation methods. The uniform dispersion of clays in polymer matrices is a general prerequisite for achieving improved mechanical and physical characteristics. Various theories and models used to design polymer/clay nanocomposites have also been highlighted. A synopsis of the applications of these advanced, high-performance polymer nanocomposites is presented, pointing out gaps to motivate potential research in this field.     

Preliminary evaluation of polymeric Fe‐ and Al‐modified clays as adsorbents for heavy metal removal in water treatment

This paper assesses the potential of modified montmorillonite clays as low‐cost adsorbents/ion‐exchangers for the removal of trace level heavy metals (Cd, Cu, Ni, Pb and Zn) from potable water. Modification of the montmorillonites resulted in the exchange of the interlayer calcium ions for the polymeric species. One unmodified montmorillonite and three polymeric Fe‐ and Al‐modified montmorillonites have been evaluated with respect to their selectivity and uptake performance. All of the clays are selective for Pb and Cu adsorption from aqueous solutions at the mildly acidic pH range in which the experiments were performed (pH 5.5–6). Polymeric iron‐ and polymeric Al/Fe‐modified clays had comparatively great affinities for all the metals studied, whilst the original and polymeric Al modified clays had relatively lower affinities. Only the uptake of Pb and Cu could be correlated with physical properties such as clay surface area. The metal selectivity could be correlated to the type of intercalated polymeric Fe and Al species of the modified clays. © 2002 Society of Chemical Industry     

Recuperative coupling of exothermic and endothermic reactions

Coupling energy intensive endothermic reaction systems with suitable exothermic reactions improves the thermal efficiency of processes and reduces the size of the reactors. One type of reactor suitable for such a type of coupling is the heat exchanger reactor. In this work, a one-dimensional pseudo-homogeneous plug flow model is used to analyze and compare the performance of co-current and counter-current heat exchanger reactors. A parametric analysis is carried out to address the vital issues, such as the exit conversion of the endothermic reaction, the temperature peak (hot spot) of the exothermic reaction and the reactor volumetric productivity. The measures to reduce the hot spot by different catalyst profiling techniques are also addressed. Some features of the dynamic behavior exhibited by these reactors, which are important from design, operational and control point of view, are presented.     

Natural and modified clays from Morocco as sorbents of ionizable herbicides in aqueous medium

The capacities of two Moroccan clays, one of them swelling and the other non-swelling, as sorbents of three ionisable pesticides: terbutryn (basic), dicamba (anionic) and paraquat (cationic) were studied. Sorption was studied on natural and modified clays with three quaternary alkyl ammonium cations of different long-chain, octadecyltrimethylammonium (ODTMA), octyltrimethylammonium (OTMA) and tetramethylammonium (TMA). Freundlich or Langmuir models were used to obtain sorption parameters. Sorption of terbutryn and dicamba by ODTMA-clays was always higher than by natural clays. Distribution coefficients (Kd) of these modified clays increased 55-128-fold (terbutryn), and 1.4-8.6-fold (dicamba) respect to the natural clays. In contrast, sorption of terbutryn by the TMA-clays and of dicamba by TMA- and OTMA-clays was lower than for natural clays. Sorption coefficients of paraquat by natural clays were similar or higher than those obtained with modified clays. In general, the sorption of herbicides was higher by swelling clay than by non-swelling clay. The results point out that the Moroccan clays studied may be used as sorbents of cationic pesticides in their natural form and of basic or even anionic herbicides when modified with long-chain organic cations in barrier technologies to enhance the immobilization of herbicides and to prevent the contamination of surface and ground water.     

溶剂浮选光度法测定水中混合偶氮染料的含量

采用溶剂气浮光度分析联用技术,研究了同时测定水中混合偶氮染料的影响因素,优化出最佳溶剂浮选条件,实验表明,染料的溶剂浮选萃取率大于96%,浓度在1~150 mg/L时,溶剂中离子缔合物的吸光度与水中活性艳红X-3B和活性黄X-R的浓度均具有较好的线性关系,相关系数为0.998以上,RSD小于1.8%。     

Failure of azo coupling by ion pairing of 4′-Diethylamino-α-cyano-stilbene-4-diazonium tetraphenylboranates in water

The influence of chloride and five tetracoordinated boron anions on the light absorption and azo coupling of the 4′-diethylamino-α-cyano-stilbene-4-diazonium ion 1 in formamide, dimethylformamide and water, respectively, is reported. In highly diluted solutions, no ion pairing of 1 occurs in polar organic solvents. Except for tetraphenylboranates, this applies also to water. Here, tetraphenylboranates produce a large bathochromic shift of the intramolecular CT-band of 1 due to the formation of contact ion pairs. This ion pairing is strongly favoured by hydrophobic interaction between 1 and the complex anion. In contrast to the free diazonium 1 , its ion pairs with tetraphenylboranates fail in azo coupling in water. This is shown on coupling with 2-naphthol.     

Adsorption of surfactants from water onto raw and HCl-activated clays in fixed beds

The removal of surfactants from water by adsorption onto raw and HCl-activated montmorillonite in fixed beds was studied. Three surfactants hexadecylpyridinium chloride (cationic), sodium dodecyl sulfate (anionic), and Triton X-102 (non-ionic) were selected in the concentration ranges lower than their critical micelle concentrations in fixed bed experiments. It was shown that the adsorption of anionic surfactant onto Ca-montmorillonite (SAz-1) decreased with increasing pH but that of cationic surfactant increased. The adsorption capacity of non-ionic surfactant was maximized at pH 7.0. For given clay, the adsorption capacities of surfactants were strongly pH-dependent. The adsorption capacity and adsorption rate of non-ionic surfactant onto SAz-1 could be largely improved after acid activation of the clay. Such an improvement was due to the fact that the dissolution of Al³⁺ or Fe²⁺ of montmorillonite occurs in acid solution. The calculated breakthrough curves in fixed bed agreed with the measured ones (standard deviation < 6%). The 50% C/C₀ breakthrough time (τ) decreased with increasing liquid flow rate. The effects of flow rate on the adsorption constant and adsorption capacity were also discussed.