Synthesis of p‐aminophenol from the hydrogenation of nitrobenzene over metal–solid acid bifunctional catalyst

BACKGROUND: A single‐step conversion of nitrobenzene (NB) to p‐aminophenol (PAP) through catalytic hydrogenation is a widely used synthesis route for PAP. The main shortcoming of this route is the use of sulfuric acid for rearrangement of the phenylhydroxylamine (PHA) intermediate. In this paper, S₂O₈^2?/ZrO₂ (PSZ) solid acid and Pt‐S₂O₈^2?/ZrO₂ (Pt‐PSZ) bifunctional catalysts were prepared for the synthesis of PAP in non‐acid medium. RESULTS: Calcination temperature has a substantial effect on the acidity, structure and activity for PHA rearrangement of PSZ. The highest PAP yield was 33.8% over PSZ calcined at 823 K when the reaction was carried out in water at 423 K. A high PAP yield of 23.9% was achieved by a single‐step reaction of nitrobenzene over Pt‐PSZ bifunctional catalysts. CONCLUSION: PSZ solid acid exhibits high activity for PHA rearrangement. Perfect tetragonal ZrO₂ and much stronger acid sites play important roles in catalytic activity. Inhibiting the hydrogenation activity by reducing the amount of Pt loading on Pt‐PSZ can improve the competition of PHA rearrangement on acid sites with hydrogenation of PHA on metal active sites, resulting in better selectivity to PAP. Copyright © 2008 Society of Chemical Industry     

Electrochemical copolymerization of aniline with m-aminophenol and novel electrical properties of the copolymer in the wide pH range

A copolymer, poly(aniline-co-m-aminophenol), has been synthesized using repeated potential cycling. The monomer concentration ratio, acid concentration and applied potential strongly affect the copolymerization rate and the properties of the copolymer. The optimum conditions for the copolymerization are that the scan potential range is controlled between −0.10 and 0.95 V (vs.SCE), and a solution consists of 0.34 M aniline, 0.012 M m-aminophenol and 2 M H₂SO₄. The IR spectra of the copolymers demonstrate that the m-aminophenol units are included in the copolymer chains. The cyclic voltammograms of the copolymers in 0.3 M Na₂SO₄ solution with various pH values were performed at the potential ranges from −0.20 to 0.80 V and at a scan rate of 60 mV s⁻¹. The results indicate that the copolymer still hold 41.7% of the electrochemical activity when the copolymer electrode was transferred from a solution of pH 5.0 to a solution of pH 11.0 in the potential range of −0.20 to 0.80 V. An impedance plot of the copolymer in a solution with pH 12.0 and at 0.40 V is constructed of a semicircle and a Warburg line with a slope of 1. This means that the electrode reaction of the copolymer at pH 12.0 is also under mass transfer control. The conductivity of the copolymer prepared under the optimum conditions is 1.42 S cm⁻¹, and slightly depends on the pH value. Thus, the pH dependence of the electrical properties of the copolymer is improved compared with poly(aniline-co-o-aminophenol), and is much better than that of the parent polyaniline.     

Synthesis, structure and catalytic behavior of ytterbium complexes bearing a phenoxy（quinolinyl）amide ligand

Two ytterbium complexes stabilized by phenoxy(quinolinyl)amide ligand 3,5-Bu t 2 -2-OC 6 H 2 CH 2 N-8-C 9 H 6 N (L) were synthesized and characterized. Reaction of anhydrous YbCl 3 with 1 equiv. of LLi 2 in THF gave the ytterbium chloride [LYbCl(THF)] 2 (1) in 73% yield. A further reaction of complex 1 with equimolar of NaN(SiMe 3 ) 2 in THF afforded the unexpected heterobimetallic "ate"-complex L 2 YbNa(THF) 2 (2) via a ligand redistribution reaction. Complex 2 could also be prepared in high isolated yield by the reaction of anhydrous YbCl 3 with 2 equiv. of LNa 2 generated in situ. Both complexes 1 and 2 were characterized by IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction analysis. It was found that complex 2 was an effective catalyst for the addition reaction of aromatic amines to carbodiimides.     

将DNA碱基翻译成蛋白质氨基酸程序设计

基因是生物的遗传物质,蛋白质是生物性状的体现物质,基因通过控制蛋白质的形成来控制生物的性状。根据DNA转录形成RNA,RNA翻译形成蛋白质的规则,利用C语言编写出翻译基因碱基序列成蛋白质氨基酸序列的程序,这无论在遗传学、医学研究,还是C语言程序设计的教学和学习都具有一定的实用价值。     

高性能海工混凝土正交试验研究

采用正交试验方法,研究了不同水胶比、胶凝总量、矿物掺合料品种、外加剂的品种、粗骨料品质对高性能海工混凝土工作性、强度和抗氯离子渗透性能的影响。试验结果表明,胶凝总量、水胶比、矿物掺合料及粗骨料品质对海工混凝土的抗氯离子渗透性能有显著的影响。随着水胶比的降低、胶凝总量的增加,添加硅粉等矿物掺合料以及选择品质较好的粗骨料,海工混凝土的抗压强度及抗氯离子渗透性得到提高。     

间氨基酚生产与发展

本文着重介绍了间氨基酚的各种生产方法,市场需求及发展前景。     

An Environmentally Benign,Highly Efficient Catalytic Reduction of p‐Nitrophenol using a Nano‐Sized Nickel Catalyst Supported on Silica‐Alumina

A green and effective method is reported for the reduction of p‐nitrophenol to p‐aminophenol using a nano‐sized nickel catalyst supported on silica‐alumina in the presence of hydrazine hydrate as an alternative source of hydrogen. It was found that nickel loaded on a silica‐alumina support is a very effective catalyst in the hydrogenation of p‐nitrophenol to p‐aminophenol. Thus it attained 100% conversion in only 69 seconds instead of 260 seconds for commercial Raney nickel. In addition, the possibility to reuse it more than one time with great efficiency gives it another advantage over commercial Rainey nickel which cannot be used more than once. This economical and environmentally friendly method provides a potentially new approach for the synthesis of the intermediate product of paracetamol in industry, which overcomes the drawbacks of the known reduction methods. The prepared catalysts were fully characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray (EDX), and electron spin resonance (ESR) tehniques.     

以偶合反应萃取催化光度法间接测定铊

研究了在pH 5 .5的弱酸性介质中 ,利用Tl(Ⅲ )置换出Cu(Ⅱ ) EDTA络合物中的Cu(Ⅱ )和Cu(Ⅱ )催化H2 O2 氧化邻氨基酚的指示反应相结合 ,通过测量 42 4nm下有机相的吸光度 ,建立了偶合反应萃取催化光度法间接测定铊的新方法。该方法的线性范围为 :0 .0 0 10～ 0 .5 0mg·L- 1 ,检出限为 :6.1× 10 - 1 0 g·ml- 1 ,可用于粉煤灰中Tl(Ⅲ )的测定。并对反应机制进行了探讨 ,建立了动力学方程式。     

硝基苯催化加氢合成对氨基苯酚

以 Pt/ γ-Al2 O3 为催化剂研究了硝基苯催化氢化法制对氨基苯酚的反应 ,得到了适宜的工艺条件。以H2 Pt Cl6溶液浸渍 γ-Al2 O3 制备的催化剂在 30 0℃用常压氢气还原 3h,再经噻吩预中毒处理后用于反应。将5 m L硝基苯加于 5 0 m L的 1 0 %硫酸溶液中 ,加质量分数为 0 .4 %的催化剂 ,搅拌速度 30 0 r/ min,在 80～ 90℃下反应 3h,对氨基苯酚的收率可达 86 % ,且催化剂寿命较长     

邻胺基苯酚在Al-Ga-Sn-Mg/KOH环境中的抑氢作用

通过恒电流集气、稳态极化曲线、交流阻抗等电化学方法探讨了邻胺基苯酚在4 mol/L KOH溶液中对Al-0.2Ga-0.1Sn-1Mg的自腐蚀抑氢作用,分析了其作用机理.结果表明：铝合金在强碱性介质中的自腐蚀析氢呈现出典型的正差异效应,自腐蚀严重.由于苯环、胺基、羟基等基团的存在使得邻胺基苯酚易在金属的表面吸附,减少了OH-与金属表面接触的机会,析氢量降低,自腐蚀程度减轻,但铝阳极的活性没有降低,正差异效应的规律也没有改变,是碱性介质中铝阳极的良好添加剂.