【作者】 侯洁；

【导师】 吕连海；

【作者基本信息】 大连理工大学 ， 应用化学， 2008， 博士

【摘要】 硝基芳胺是重要的有机中间体,可用于有机合成、颜料和染料、医药、农药和橡胶助剂、树脂、感光材料等领域中。目前硝基苯类化合物制备芳胺的液相催化加氢工艺已趋成熟,但当苯环上硝基与其他不饱和基团共存时,如何实现硝基的选择性还原一直是国内外选择性催化领域的研究热点,特别是对于二硝基苯类化合物的高选择性部分还原更具挑战性。因此对二硝基苯类化合物高选择性部分加氢生成硝基芳胺的催化体系的深入研究兼具有理论意义和实际应用价值。间二硝基苯是最简单并且选择性加氢研究最多的二硝基化合物,因此本论文首先从间二硝基苯的催化加氢展开,通过比较不同骨架型催化剂对间二硝基苯的加氢反应历程,发现骨架钌镍炭（RuNiC）催化剂对间硝基苯胺的选择性最高,当底物完全转化时,间硝基苯胺选择性为96%;系统考察了反应溶剂、反应温度、压力和底物浓度因素对加氢选择性的影响。此外,邻二硝基苯和对二硝基苯的选择性加氢也呈现出了较高的选择性,当底物完全转化时,邻硝基苯胺及对硝基苯胺的选择性分别为92%和90%;通过跟踪邻、间、对二硝基苯的反应历程,发现三种底物的反应速率虽略有差异,但具有相似的反应规律。本论文进一步对底物范围进行了扩充,发现骨架钌镍炭对2,4-二硝基甲苯、2,4-二硝基苯甲醚、2,4-二硝基苯胺、2,4-二硝基苯酚及3,5-二硝基苯甲酸的选择性加氢均呈现出较高的选择性,但不同取代基会影响底物的反应活性;吸电子基团（-COOH）比供电子基团（-OH、-OCH₃、-NH₂）更有利于加氢反应的进行。此外,由于取代基与两个硝基（2,4-二硝基苯类化合物）位置上的相对差异,会生成不同的单还原位置异构体,特别是取代基为-NH₂、-OH、-OCH₃,表现出较强的邻基效应,产物以取代基邻位硝基还原为主。考虑到金属钌价格昂贵且骨架钌基催化剂难于制备,限制了骨架钌基催化剂的工业应用。采用负载型催化剂可以大大减少金属用量,降低催化剂制备成本,在本论文中采用表面活性剂保护法制备出高分散纳米负载型催化剂,比较Ru/C、Rh/C、Pd/C及Pt/C对间二硝基苯的催化加氢历程,发现Ru/C催化剂对间硝基苯胺的选择性高于其它三种催化剂,在较温和条件下,当底物完全转化时,间硝基苯胺的选择性可达到99%;系统考察了反应溶剂、温度、压力、底物浓度、催化剂担载量及催化剂用量对反应的影响,催化剂连续使用15次后,补加催化剂后,仍然可以保持较高的活性和选择性。此外,对邻、对二硝基苯进行选择性加氢,当底物转化率为100%时,邻硝基苯胺、对硝基苯胺的选择性分别为99%和95%,均高于骨架RuNiC体系。对比邻、间、对二硝基苯加氢的反应历程,结果表明三种底物具有相似的反应规律,均为典型的连串反应,而反应速率略有差异。进而将底物范围进行扩充,发现纳米Ru/C催化剂对取代二硝基苯类化合物的选择性催化加氢也表现出较高的选择性和反应活性。分别对2,4-二硝基甲苯、1,3-二硝基甲苯、2,5-二硝基-对二甲苯选择性加氢,底物转化率为98%、100%、95%时,单硝基还原产物的选择性分别为98%、92%、100%;在2,4-二硝基苯酚、2,4-二硝基苯胺、2,4-二硝基苯甲醚的选择性加氢中,底物完全转化时,部分还原产物的选择性为100%、100%、96%;对3,5-二硝基苯甲酸、3,5-二硝基水杨酸,2,4-二硝基氟苯的选择性加氢,底物完全转化时,硝基苯胺的选择性分别为97%、100%、97%,反应活性及对目标产物的选择性均高于文献报道。与骨架RuNiC体系相同,取代基性质会影响底物的反应活性及选择性。含有吸电子基团的二硝基苯类化合物反应活性明显高于含有供电子基的二硝基化合物的加氢反应;部分底物由于取代基与硝基相对位置不同,会导致单还原产物异构体的生成,并且取代基为-OH、-NH₂、-OCH₃时,邻基效应表现更为强烈,取代基邻位硝基还原产物的选择性分别100%,98%,96%。3,5-二硝基水杨酸的选择性加氢反应为两段反应,第一段反应是-OH邻位硝基的选择性还原,3,5-二硝基水杨酸完全转化时,3-氨基-5-硝基水杨酸的选择性为100%;第二段反应则需要提高反应条件后才能生成双还原产物3,5-二氨基水杨酸。更多还原

【Abstract】 Nitroanilines are important intermediates widely used in pharmaceuticals,polymers, herbicides,fine chemicals and some other industrial fields;therefore,there is a strong incentive both in theoretical and economic perspective to develop chemoselective catalyst for the partial hydrogenation of dinitrobenzenes to nitroanilines.Although the reductions of various simple nitro compounds have been readily carded out with different commercial catalysts,the selective reduction of a nitro group amoung several reducible groups in the same molecule is more challenging,especially when two NO₂ groups co-exist.In recent years,ruthenium-catalyzed processes have become one of the most preferred methodologies in reduction reactions due to their high efficiency and versatile applications.In this dissertation,hydrogenations of m-dinitrobenzene over four kinds of skeletal catalysts were compared.The hydrogenation of m-dinitrobenzene to m-nitroaniline over skeletal RuNiC was higher than other catalysts,when m-dinitrobenzene converted completely,the selelctity to m-nitroaniline reached 96%.Based on this result,effects of the reaction conditions including temperature,pressure,and substrate concentration on selective hydrogenation of m-dinitrobenzene over Skeletal RuNiC were investigated.Additionally,the hydrogenation of o-,p-dinitrobenzene over Skeletal RuNiC also showed high selectivity to o-, p-nitroaniline.The reaction courses were tracked by gas chromatography,indicating that three substrates converted in a similar rule with different reaction order.In order to extend the applicability of skeletal ruthenium,selective hydrogenations of substituted dinitrobenzenes（2,4-dinitrophenol,2,4-dinitrobenzamine,2,4-dinitrotoluene, 3,5-dinitrobenzoic acid） were studied.The electron-withdrawing groups favored the hydrogenation of substituted dinitrobenzenes than electron-donating group.In addition, different position of the substituted group to two nitro groups in 2,4-dinitrobenzenes could lead to isomers,and the effect of substituted group on the isomer ratio was discussed.The industrial application of Skeletal Ru-based catalysts is limited by the high-cost and high melting point of metal ruthenium.Thus,supported ruthenium catalyst with high dispersion was prepared through surfactant-protection Ru colloid method.Hydrogenation of m-dinitrobenzene was chosen as the model reaction,and it was found that the Ru/C showed the highest selectivity to m-nitroanilines among several supported catalysts.The selective hydrogenation of m-dinitrobenzene over Ru/C was investigated and effects of reaction conditions such as temperature,pressure,substrate concentration,and Ru load amount and catalyst amount as well as catalyst lifetime were studied during circulation use.The reaction course showed that the hydrogenation of m-dinitrobenzene was a typical tandem reaction including m-dinitrobenzene to m-nitroaniline and m-nitroaniline to m-phenyldiamine,and the second step only occurred when the m-dinitrobenzene was converted completely;Ru/C also showed high selectivity to o-,p-nitroaniline in hydrogenation of o,p-dinitrobenzene.Similar to Skeletal RuNiC systermRu/C catalyst was also suitable for chernoselective hydrogenation of other substituted dinitrobenzenes.The selectivity of 2,4-dinitrotoluene,1,3-dinitrotoluene,2,5-dinitro-p-xylene, to partially hydrogenated products was 98%,92%and 100%respectively,when the conversion of substrate was 98%,100%,95%;the selectivity to partially reduced product was 100%,100%and 95%when 2,4-dinitrophenol,2,4-dinitrobenzamine,2,4-dinitroanisole converted completely;the selectivity of partial hydrogenation of 3,5-dimtrobenzoic acid, 3,5-dinitrosalicylic acid and 2,4-dinitrofluorobenzene was 97%,100%and 97%when substrate converted completely.All these results are higher than the selectivity published in literature.Similar to Skeletal RuNIC systerm,substited group played important role in the selective hydrogenation.The dinitrobenzene with electron-withdrawing group can be hydrogenated much easier than the dinitrobenzene with electron-donating group.The relative position of substituted group to two nitro groups can lead to foramation of isomers,when the group was -NH₂,-OH,-OCH₃,the reaction showed strong ortho effect,that is,the -NO₂ at the otho position of substituted group could be reduced easily.The hydrogenation of was not only step-wised,but also a two-stage reaction.At first stage,3,5-dinitrosalicylic acid partially hydrogenated to 3-amino-5-nitrosalicylic acid with high selectivity（100%）,and the second-stage reaction,in which 3-amino-5-nitrosalicylic acid hydrogenated to 3,5-diaminosalicylic acid,occurred until the reaction conditions were increased.更多还原