杯芳烃催化剂在有机反应中的应用

杯芳烃是一类新型的主客体化合物。本文综述了杯芳烃催化剂在某些有机化学中的应用,并拓宽了合成杯芳烃催化剂的新思路。     

Synthesis of metal intercalated clay catalysts for selective hydrogenation reactions

Interlamellar space of the smectite clay minerals have been found as an excellent nano phase reactor due to their easy swelling property and the adsorption capacity. In this work size quantized nano particles of catalytically active noble metals have been generated within the interlamellar space of the smectite type clay minerals. Platinum and ruthenium intercalated/impregnated montmorillonite and hectorite catalysts were synthesised and characterized by various instrumental techniques. Catalytic activity of the synthesised catalysts was evaluated towards hydrogenation of cinnamaldehyde in liquid phase. The effect of various reaction parameters such as temperature, hydrogen pressure, solvents, and amount of catalyst and time on stream on conversion and selectivity were studied and the results are discussed. The studies revealed that noble metal intercalated/impregnated clay catalysts were very effective in hydrogenation reactions as they showed significant conversion and selectivity. Comparison of catalytic activity made with the impregnated catalysts showed that the intercalated catalysts were better than impregnated catalysts in terms of conversion and selectivity.     

Ozonation of organic compounds in alkaline aqueous media

Effect of pH on the aqueous phase ozonation of various organic compounds was investigated. The reaction was accelerated in alkaline media due to the formation of active hydroxyl radical by an interaction of ozone with hydroxide ion. However, in a strongly alkaline media (pH < 11.9), hydroxyl radical dissociated into less reactive oxygen ion and the efficiency of ozonation decreased. By means of the theory of gas absorption accompanied by chemical reaction, it was found that the rate of the decomposition of ozone in the presence of about 300 ppm of 1-butanol was 5-80 times larger than that catalyzed only by hydroxide ion in the pH range of 11-13. Efficiency of ozonation showed that an optimum range of pH for the removal of total organic carbon was 9-10.     

Degradation of solvolysis lignin using Lewis acid catalysts

Alcell‐derived lignin was depolymerized in a batch reactor using the Lewis acid catalysts NiCl₂ and FeCl₃. The objective was to investigate the use of Lewis acids in the production of useful liquid products directly from solvolysis lignin. The effects of reaction temperature, time and catalyst were studied on the conversion of this lignin to gas, solid and liquid products. Also, selected monomeric compounds in the ether solubles were monitored in terms of the variation in their yields with different reaction conditions. The highest conversions, 30% and 26% from Ni and Fe, respectively, were both attained at the reaction conditions of 305°C and 1 h reaction time. The Ni produced a somewhat higher yield of ether solubles, reflecting its slightly higher performance. Under the reaction conditions studied, both catalysts apparently favour condensation reactions leading to the formation of insoluble reactor residue from solvolysis lignin. Low quantities of monomeric compounds were produced, with phenols dominating over ketones and aldehydes for both catalysts.     

Catalytic oxidation of organic compounds in aqueous media

Ru, Pt and Rh catalysts supported on titania, ceria or active carbon and a Mn/Ce composite oxide catalysts were prepared and their catalytic behavior in Wet Air Oxidation ( 20 bar O₂) of phenol and acetic acid were investigated. Phenol was found to be an easily oxidizable compound as 170°C, while acetic acid was a very refractory molecule, even at 200°C. Ru(5 wt.-%)/C is a very efficient catalyst for the WAO of acetic acid without any leaching of noble metal.     

Development of novel adsorbent materials for recovery and enrichment of uranium from aqueous media

A new polymeric adsorbent bearing both hydrophilic groups providing swelling in water and amidoxime groups for chelating with uranyl ions (UO₂²⁺), has been developed and its adsorptive ability for recovering uranium from aqueous media has been investigated. The polymers obtained by irradiating the solution of polyethylene glycol (PEG) in acrylonitrile (AN) are defined as interpenetrating polymer networks (IPNs) and the adsorbent has been obtained by applying the amidoximation reaction to the IPNs with a conversion ratio of ∼ 60%. Kinetics of the conversion reaction of the cyano (CN) group to the amidoxime (HONCNH₂) group has been studied by reacting with hydroxylamine (NH₂OH) solution at a molar ratio of NH₂OH/CN = 1.25 in aqueous media at three different temperatures, 30, 40, and 50°C, for 3–4 days. The degree of amidoximation ratio was determined by UO₂²⁺ ion adsorption and FTIR spectrometry and the UO₂²⁺ ion adsorption values were found by both UV and gamma spectrometry and also by gravimetry. It was found that the polymeric adsorbent has a very high adsorption ability for uranium and quite a good stability in aqueous media. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2475–2480, 1997     

Deactivation of metal catalysts in liquid phase organic reactions

The paper gives a general survey of the factors contributing to the deactivation of metal catalysts employed in liquid phase reactions for the synthesis of fine or intermediate chemicals. The main causes of catalyst deactivation are particle sintering, metal and support leaching, deposition of inactive metal layers or polymeric species, and poisoning by strongly adsorbed species. Weakly adsorbed species, poisons at low surface coverage and solvents, may act as selectivity promoters or modifiers. Three examples of long term stability studies carried out in trickle-bed reactor (glucose to sorbitol hydrogenation on Ru/C catalysts, hydroxypropanal to 1,3-propanediol hydrogenation on Ru/TiO₂ catalysts, and wet air oxidation of paper pulp effluents on Ru/TiO₂) are discussed.     

Conformation-switched chemosensor for selective detection of Hg2+ in aqueous media

A conformation flexible chemosensor for selective detection of Hg²⁺ in aqueous media was achieved by incorporating two well-known rhodamine-6G dyes and a ferrocene group within one molecule. Distinguished from the monosubstituted ferrocene derivative which is previously reported a lack of interaction with Hg²⁺, the title compound was characteristic of two-armed bidendate binding unit. The Hg²⁺ sensing behavior can be switched via the conformation flexibility. The 1:1 sensor/Hg²⁺ binding mode was proposed and supported by the titration experiment and ESI mass spectrum. The fluorescent sensor can display a highly selective response of fluorescence enhancement toward Hg²⁺ and detect the parts per billion (ppb) level of Hg²⁺ in aqueous environment.     

A novel thermo and pH-double sensitive hydrogel immobilized Pd catalyst for Heck and Suzuki reactions in aqueous media

A novel Hydrogel (1) was prepared from N-isopropylacrylamide, 4-vinylpyridine and potassium acrylate by free radical cross-linking polymerization. Hydrogel (1) showed both thermosensitivity and pH-sensitivity, and exhibited high swelling capacity in water. Because Hydrogel (1) has porous structure in its network and good loading performance with Pd²⁺, it was used as “microreactor” for immobilization of metal nanoparticles. We chose Heck and Suzuki reaction of aryl halides in water as test reaction to probe the catalytic activity of such Hydrogel (1) supported palladium catalyst. As a result, the Hydrogel (1)-Pd (II) catalyst exhibited good catalytic activity in both Heck and Suzuki reactions. Moreover, the Hydrogel (1)-Pd (II) catalyst was easily recovered and recycled. The reuse experiments showed that it was recycled six times without obviously losing of catalytic activity.     

A benzothiazole-based semisquarylium dye suitable for highly selective Hg sensing in aqueous media

A novel semisquarylium dye was synthesized by the reaction between 3,4-dibutoxy-3-cyclobutene-1,2-dione and a benzothiazolium salt and its metal ion sensing properties were investigated using absorption and emission spectroscopy. These misquarylium exhibited high selectivity for Hg²⁺ ions, as compared with Ca²⁺, Pb²⁺, Al³⁺, Ce²⁺, Ba²⁺, Ni²⁺, Cd²⁺, Zn²⁺ and Mg²⁺ ions in DMSO/H₂O (9:1, v/v), which was attributed to the formation of a 2:1 BSQ:Hg²⁺ coordination complex, the formation of which was supported by the calculated geometry of the complex.     

环丙烷-1,1-双甲酸酯的路易斯酸催化开环反应

作为现代有机化学中应用广泛的3-碳合成子,活化的环丙烷衍生物的开环反应一直受到人们的普遍关注,并且已经很好地被应用于串联的开环反应来构筑具有复杂结构的有机分子骨架。介绍了环丙烷1,1-双甲酸酯的一般合成方法,综述了近年来环丙烷-1,1-双甲酸酯在路易斯酸催化下的开环反应及其在某些领域的应用,并对其未来发展方向进行了展望。     

Oxidation of organic pollutants in aqueous solutions by nanosized copper oxide catalysts

The catalytic activity of copper oxide nanoparticles was investigated for the removal of organic pollutants in aqueous solutions, using hydrogen peroxide as an oxidant. Complete degradation of both alachlor and phenanthrene was achieved after 20 min. The kinetics of the reaction was found to be pseudo-first-order with respect to the pollutant. The influence on the reaction kinetics of different catalyst samples, consisting of the same material but of different origin and different particle properties, was examined. The effects of several factors such as irradiation, oxidant concentration, ionic strength and pH on the reaction were also investigated. The catalysis is not photo-induced and can be performed without UV–vis irradiation. In particular, an optimal oxidant concentration was determined for the studied system. The presence of salts was found to inhibit the alachlor degradation rate. The addition of high concentrations of oxidant or salt results in pseudo-zero-order kinetics. However, NaCl at very high concentrations (>1 M) was found to cause a dramatic increase in reaction rate. The catalysis is efficient over a wide range of pH values.     

Preparation of Rh/active carbon catalysts by adsorption in organic media

We have attempted to rationalize the preparation of metal/activated carbon catalysts, taking into account the surface properties of the support. The texture and structure of two commercial carbons, NORIT SX-1 and CECA BGP and of a third one C2, obtained from almond shell, have been fully characterized. These data were used for choosing the optimum conditions for the active phase incorporation. In this way, a fairly good loading and dispersion of ∼- 1% Rh on the supports have been obtained by adsorption from solution, using acetone and 4:1 benzene-ethanol as the suspension media. Some general considerations about the preparation of metal/activated carbon catalysts are given.     

Lewis acid initiated melt reactions of polystyrene and EPDM rubber

Summary In order to obtain high impact polystyrene (PS), experiments have been performed on coupling of EPDM rubber and PS in the mixing chamber of a HAAKE plastograph. Lewis acids were added to the melt and the torque increase observed by their addition proved that chemical reactions take place in the system. During the reaction, the rubber proved to be more active, it became crosslinked and/or it was coupled with the PS molecules. Only a small fraction of the PS present coupled to the rubber molecules. No significant degradation process could be detected. Mechanical properties (tensile modulus and strength) improved during the reaction. This can be interpreted by the increased solubility of the coupled rubber molecules in the continuous PS phase.     

Zeolite-Y immobilized Metallo-ligand complexes: A novel heterogenous catalysts for selective oxidation

Transition metal [M = Co(II), Cu(II)] complexes of H₂L¹ and H₂L² ligands have been prepared as neat and nanohybrid zeolite-Y immobilized complexes. The various analytical tools such as FTIR, ICP-AES, elemental analysis, UV–vis, Brunauer, Emmett and Teller (BET) surface area analysis, Thermal analysis, scanning electron micrographs, Powder XRD, conductivity, magnetic moment, and AAS were employed for the characterization of the prepared catalysts. Among all catalysts, the [Cu(L¹)]-Y (heterogeneous) and [Cu(L¹)] (homogeneous) have offered high activity and selectivity over oxidation of cyclohexene. Moreover, the [Cu(L¹)] and [Cu(L¹)]-Y were employed as catalyst over various organic substrates at identical reaction condition. The immobilized catalyst [Cu(L¹)]-Y is found to be moderate active over oxidation of cyclohexane (75.2%,), benzene (8.21%), phenol (14.5%), styrene (87.5), benzyl alcohol (21.5%), limonene (11.2%), α-pinene (9.15%), and cyclooctane (76.8%) with high TON values (21942-2054). The mechanistic study using UV–vis and FTIR suggests the participation of active metalperoxo species, which is reinforced by its high catalytic activity over limonene (16.3%) in the absence oxidant.