水溶性配合物[RuCl2(TPPTS)2]2催化卤代硝基苯选择性加氢

以合成的水溶性钌配合物[RuC l2(TPPTS)2]2作为催化剂,用于水/有机两相体系中催化卤代硝基苯中硝基的选择性加氢反应.以对-氯硝基苯为底物,考察了反应温度、氢气压力、催化剂浓度、水溶液的pH值等对对-氯硝基苯转化率和生成对-氯苯胺选择性的影响.在100℃,氢气压力3.0 MPa时,反应6h,对-氯硝基苯转化率可达100%,生成对-氯苯胺的选择性可达95.2%.该催化剂对其他卤代硝基苯的加氢反应也表现出较高的催化活性.     

原子级分散Fe-N-C温和条件下选择性氧化催化特性

采用非溶液法制备了原子级分散的Fe-N-C催化剂,并用于硫醚和二级醇的选择性氧化.研究结果表明,这种原子级分散的Fe-N-C催化剂可在温和条件下选择性地将硫醚转化为亚砜,而不会产生过度氧化的砜.该工艺具有反应条件温和、反应速度快、收率高等优点;该催化剂对二级醇氧化制酮反应具有较高的催化活性,产率较高.作为一种非均相催化剂,Fe-N-C催化剂循环使用5次后活性未见显著下降;在实验结果和参考文献的基础上还提出了一种可能的自由基反应机理.     

Syntheses, reactions, and structures of osmium(II) distannyl complexes, LnOs-SnMe2SnR3 (R = Me, Ph), from reaction between LnOs-SnClMe2 and either LiSnMe3 or KSnPh3

Reaction between Os(SnClMe₂)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ and either LiSnMe₃ or KSnPh₃ produces the distannyl complexes, Os(SnMe₂SnMe₃)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (1) or Os(SnMe₂SnPh₃)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (3), respectively. Similarly, reaction between Os(SnClMe₂)Cl(CO)₂(PPh₃)₂ (6) and KSnPh₃ produces the distannyl complex, Os(SnMe₂SnPh₃)Cl(CO)₂(PPh₃)₂ (7). In the ¹¹⁹Sn NMR spectra of these stable osmium(II) distannyl complexes both the α-Sn and β-Sn atoms show well-resolved ¹¹⁹Sn-¹¹⁹Sn and ¹¹⁹Sn-¹¹⁷Sn coupling. Each of these three distannyl complexes can be selectively functionalised at the α-Sn atom by reaction with SnCl₂Me₂ giving Os(SnClMeSnMe₃)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (2), Os(SnClMeSnPh₃)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (4), and Os(SnClMeSnPh₃)Cl(CO)₂(PPh₃)₂ (8), respectively. Treatment of compounds 3 or 7 with iodine also cleaves one α-methyl group, selectively, to give Os(SnIMeSnPh₃)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (5), or Os(SnIMeSnPh₃)Cl(CO)₂(PPh₃)₂ (9). Crystal structures for complexes 3 and 7 have been determined.     

Colorimetric and fluorescence sensing of anions using thiourea based coumarin receptors

Thiourea-containing coumarins 1, 2 have been designed and synthesized via reaction of 6-aminomethylcoumarin and the corresponding isothiocyanates. Their anion-binding ability has been examined using UV-vis, fluorescence and ¹H NMR. The anion recognition takes place through charge neutral thiourea receptor sites with concomitant fluorescence quenching of the coumarin moiety with 1 showing a strong binding to C₆H₅COO⁻ over F⁻ with a distinct change in color.     

Low-temperature selective catalytic reduction of NOx with NH3 over zeolite catalysts: A review

The selective catalytic reduction (SCR) of NO_x by NH₃ is one of the most mature technologies for NO_x treatment. Catalysts are the main factors affecting denitrification efficiency. Zeolites as low-temperature NH₃-SCR catalysts have been extensively studied in the past few years. In this work, the mechanism of zeolites for NH₃-SCR reaction was reviewed and the denitrification performances of zeolite catalysts prepared by different methods were compared. The effects of sulfur and water poisoning on zeolite catalysts in NH₃-SCR reaction were also analyzed. Several ways to address the problems in low-temperature NH₃-SCR reaction were discussed. Hopefully, this review could provide a fundamental understanding of SCR reaction on zeolite catalysts and pave the way toward similar studies to realize its commercial applications.     

Selective removal of Cu versus Ni, Zn and Mn by using a new carrier in a supported liquid membrane

A study on transport, kinetic selectivity and stability in SLM operations using a new carrier, the molecule 2-hydroxy-5-dodecylbenzaldehyde (2H5DBA) in kerosene, is described. A simple transport model is derived to evaluate the mass transfer coefficient in the membrane. Finally a comparison with the di-(2-ethylhexyl) phosphoric acid (D2EHPA) carrier in kerosene is made. The SLM system was employed and tested in the removal of Cu²⁺ from wastewater by using the operating conditions obtained from L–L extraction tests. Studies on the kinetics of copper extraction by using the 2H5DBA showed that complexation reaction is very fast. Transport tests were performed at different carrier concentrations (10%, 30%, 50% (v/v)) showing the improvement of SLM performance with increasing its concentration. Operating the SLM at optimum conditions (50% (v/v) 2H5DBA concentration in kerosene, feed pH 5, strip pH 2.2) final copper concentrations in the feed and strip phases were, respectively, 2.0 and 47.0 mg L⁻¹, starting from 50 mg L⁻¹ in the feed, meaning a significant up-hill transport. The fluxes (J) were calculated by fitting the experimental data of copper concentration in the feed by an exponential equation. They were used to calculate the transport (kinetic) selectivities of Cu²⁺ SLM separation over Ni²⁺, Zn²⁺ and Mn²⁺, given by the ratio J₀(Cu)/J₀(M), where M = Ni, Zn and Mn. The values were 37.4, 48.2 and 42.1, respectively. Transport and stability tests at the optimal carrier concentration by using the 2H5DBA and the D2EHPA in kerosene were carried out to compare them in terms of flux, lifetime and mass transfer coefficients. Experimental data evidenced for 2H5DBA a lower copper flux (8.67 mmol h⁻¹ m⁻² versus 36.71 mmol h⁻¹ m⁻²), a lower lifetime (20 h versus 57 h) and lower mass transfer coefficient in the membrane (3.00 × 10⁻⁷ m s⁻¹ versus 2.00 × 10⁻⁶ m s⁻¹) but the selectivity of the separation process can overcome the disadvantages.     

微乳液法制备Pt/ZrO2催化剂及其催化加氢活性研究

采用十六烷基三甲基溴化铵（CTAB）/正丁醇/环己烷/H2PtCl6微乳液体系,以N2H4.H2O为还原剂,ZrO2为载体,制备Pt/ZrO2催化剂。以对氯硝基苯（p-CNB）选择加氢反应为探针,考察微乳液组成及载体焙烧温度对Pt/ZrO2催化剂催化活性的影响。由TEM、XRD对载体和催化剂进行表征。结果表明,采用微乳...     

Pd/Fe3O4-MCNT磁性催化剂的制备、表征及催化性能

利用多元醇法制备了单分散Fe₃O₄纳米粒子修饰多壁碳纳米管(MCNT)的磁性复合材料, 并以X射线衍射(XRD)、透射电镜(TEM)和X射线能量色散谱(EDS)对碳纳米管磁性复合材料的结构和组成进行了表征. 研究发现, 通过调控Fe₃O₄前驱体与MCNT载体的质量比, 可以很好地控制沉积的磁性纳米粒子大小. 以碳纳米管磁性复合材料为载体, 采用多元醇法成功制备了Pd负载量为3.0% (w)的Pd/Fe₃O₄-MCNT磁性催化剂. 磁性质测试表明碳纳米管磁性复合材料在负载Pd前后都具有良好的超顺磁性. 以肉桂醛加氢为探针反应研究了Pd/Fe₃O₄-MCNT的催化性能, 结果表明该催化剂表现出良好的催化加氢性能, 在外加磁场下催化剂能与液相反应体系高效分离, 循环使用4次后, 催化性能没有明显下降, 显示了良好的循环利用性能.     

PEG-stabilized palladium nanoparticles： An efficient and recyclable catalyst for the selective hydrogenation of 1,5-cyclooctadiene in thermoregulated PEG biphase system

Polyethylene glycol （PEG）-stabilized palladium nanoparticles were prepared and applied to the selective hydrogenation of 1,5- cyclooctadiene （1,5-COD） in thermoregulated PEG biphase system, which allows a reaction in a single-phase at a higher temperature followed by a phase split at a lower temperature. Under the optimized reaction conditions, the conversion of 1,5-COD and the selectivity of cyclooctene （COE） were 100 and 98%, respectively. The catalyst could be easily separated from the product by phase separation and reused for 6 times without evident loss in activity and selectivity. 2007 Yan Hua Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

The effect of substituents and operating conditions on the electrochemical fluorination of alkyl phenylacetates in Et3N·4HF medium

Selective electrochemical fluorination of alkyl phenylacetates (Ph-CH₂-COOR, where R is methyl, ethyl, n-propyl, n-butyl, i-propyl and sec-butyl) under galvanostatic conditions were reported in Et₃N·4HF medium. Preparative electrolysis experiments were carried out both in pre-electrolysed dry Et₃N·4HF and the same electrolyte medium without pre-electrolysis. Very little hydrolysed fluorinated products were obtained in pre-electrolysed medium where as significant quantities of hydrolysed products leading to fluorinated phenylacetic acid were obtained from Et₃N·4HF without pre-electrolysis. Under optimum experimental conditions up to 87% selectivity of monofluoro ester could be achieved. Difluoro alkyl phenylacetate, monofluoro and difluoro phenylacetic acids were the other predominant side products obtained. The hydrolysis appears to be initiated by tautomeric transformation of proton after the initial electro oxidative formation of the cation radical. ¹⁹F as well as ¹H NMR spectroscopy have been employed to identify the minor constituents formed during the electro oxidative process.