贮氢合金催化氢化对硝基甲苯及苯胺衍生物的合成

【作者】 刘勇；

【导师】 蒋金芝； 唐有根；

【作者基本信息】 中南大学 ， 有机化学， 2011， 硕士

【摘要】 对甲苯胺用于医药、农药、颜料等领域,是重要的有机合成中间体。该中间体主要是在不同的还原剂或催化剂的共同作用下催化还原对硝基甲苯制得。贮氢合金是近年来开发的一类新型加氢(脱氢)催化剂,具有加氢条件温和、活性好、选择性高等特点,是加氢过程不可多得的优良催化剂。贮氢合金电极用于电化学合成的报道较多,但直接用合金粉加氢还原化合物的报道并不多见。因此,本文围绕贮氢合金、对甲苯胺进行了以下研究：本文研究了在Ar气保护下,使用纯度高于99%的金属材料,通过真空负压中频感应熔炼制备了AB5型的ML(Ni3.69Co0.72Mn0.35Al0.24)和A2B7型的La2(NiCoAl)7两种贮氢合金。采用X射线衍射对两种合金结构进行表征,测试结果表明,两种贮氢合金都有尖锐的X射线衍射峰,具有均匀的结晶状态,晶粒尺寸约为50nm；用兰电电池测试系统和CHI660D电化学工作站对合金的电化学性能进行测试,结果表明：两种合金均容易被活化,在3次充放电循环内达到最大放电容量。合金的电化学性能与合金的成分、晶胞形貌有密切的关系。A2B7型贮氢合金的电化学容量比AB5型合金高；同时也更容易粉化,循环性能不如AB5型合金；另外A2B7型合金有比AB5型合金更好的高倍率性能。总体说来,A2B7型贮氢合金电化学性能更优。采用掺杂AB5与A2B7型两种贮氢合金形成的氢化物作为氢源及催化剂,加氢还原对硝基甲苯生成对甲苯胺进行了研究。利用GC-MS和GC分别对产物进行定性和定量分析。结果表明：该催化剂可以在温和条件下将对硝基甲苯加氢还原成对甲苯胺,未检测到副产物的产生,对甲苯胺选择性高达100%,且反应后催化剂与反应体系容易分离。并详细探讨了催化剂用量、不同溶剂、反应温度和反应时间等对反应的影响。结果表明：催化剂的含氢量与催化剂的活性密切相关,溶剂的性质对反应有明显影响,以无水乙醇或甲苯为溶剂时催化剂性能最好,重复使用5次仍具有较高的催化活性。在相同外界条件作用下,AB5型贮氢合金的催化性能不如A2B7型合金。以对甲苯胺为原料,合成了对二甲胺基苯甲醛和对甲基氯化苄两种化合物,通过红外光谱、质谱、核磁共振谱对产物进行表征,证实了合成产物为目标产物。更多还原

【Abstract】 P-toluidine, which is used in medicine, pesticide, pigments and other fields, is obtained by catalytic reduction of p-nitrotoluene in different reaction systems. In recent years, hydrogen storage alloy has been developed as a new type of hydrogenation (dehydrogenation) catalyst. There are several advantages of the alloy, such as:it can hydrogenate the compounds under mild conditions, it has good catalytic activity, and the reaction has high selectivity when the catalyst is used. Because of the characteristics of the alloy, it has become a good catalyst for the hydrogenation process. The research about the hydrogen storage alloy which is used as an electrode in electrochemical synthesis has already been reported a lot, but there are rare reports about the direct hydrogenation of compounds with the alloy powder. Therefore, The hydrogen storage alloys and P-toluidine have been studied in this paper.In this paper, ML(Ni3.69Co0.72Mn0.35Al0.24) and La2(NiCoAl)7 hydrogen storage alloys were prepared using the metal materials(purity higher than 99%) by medium frequency vacuum induction melting under the protection of the Ar gas. The structures of the alloys were characterized by X-ray diffraction (XRD). The results reveal that the XRD peaks of two kinds of hydrogen storage alloys were sharp. The hydrogen storage alloys were nano-crystalline structure, and its grain size below 50nm. The electrochemical properties of the alloys were tested by LAND Test Systems and CHI660D ChemStation. The results reveal that the two kinds of alloys could be activated easily and the maximum discharge capacity appeared in 3 times charge-discharge cycles. The electrochemical properties of the alloys are related to alloy compositions and cell morphology. The capacity of A2B7-type hydrogen storage alloy is higher than that of AB5-type alloy. Otherwise, the A2B7-type hydrogen storage alloy could be powdered more easily, so the cycle performance is not better than the AB5-type alloy. In addition, the high-rate performance of A2B7-type alloy is better than AB5-type alloy. In a word, A2B7-type hydrogen storage alloy has better electrochemical properties.The hydrides formed by doping AB5-type and A2B7-type hydrogen storage alloys are used as the hydrogen sources and catalysts for hydrogenation of p-nitrotoluene to p-toluidine. GC-MS and GC were used to make qualitative analysis and quantitative analysis on the products. The results reveal that the catalysts can hydrogenate the p-nitrotoluene to p-toluidine under the mild conditions with no by-products, the selectivity of p-toluidine is up to 100%, and the reaction catalyst and reaction system could be separated easily after the reaction. The effect of the amount of catalyst, solvent, reaction temperature and reaction time during the reaction process is discussed in details. The results reveal that the amount of the catalyst is closely related to the catalytic activity of hydrogen. The nature of the solvent has a significant effect on the reaction. The performace of the catalyst is the best when the ethanol or toluene is used as solvent, and it has maintained high catalytic activity after repeating for 5 times. Under the same external conditions, the catalytic properties of A2B7 type alloy are better than that of AB5 type alloy.The p-dimethylamino benzaldehyde and p-methyl benzyl chloride have been synthesized by p-toluidine and characterized by infrared spectroscopy, mass spectroscopy and nuclear magnetic resonance spectroscopy, which confirmed that the synthetic product is the target product.更多还原