Study On Hydrogenation Of 2-(2,5-Dimethoxyphenyl) Nitroethene

The high effective and selective hydrogenation of organic substrates with molecular hydrogen and metal complex as catalyst is one of the most interesting and challenging topics in catalytic frontier. 2-(2,5-Dimethoxyphenyl)nitroethene (DMPNE) and its hydrogenation product 2,5-Dimethoxyphenethylamine(DMPEA) are wildly used in fine chemical synthesis and medicine intermediate. The developments of catalytic hydrogenation, especially the hydrogenation of nitrobenzene are reviewed. TPPTS [P(C6H4SO3Na)3] have been synthesized. With molecular hydrogen as reductive, the DMPNE hydrogenation catalyzed by RuCl3-TPPTS has been investigated in autoclave. The catalytic performance of Ru/C, Ru-Pd/C, Ru/Al2O3, Ru-Pd/Al2O3 in the hydrogenation have been also studied. A series of new and useful results with application prospect have been obtained. Ru/C, Ru-Pd/C etc. have been synthesized and their structures have been confirmed by BET, XRD, XPS.With molecular hydrogen as reductive, the performance of RuCl3-TPPTS as catalyst precursor for selective hydrogenation of both C=C and -NO2 groups in DMPNE have been studied in biphasic catalytic system (aqueous/organic phase). Their hydrogenation products have been analyzed by GC-MS, the main product is DMPEA. The conversion and the selectivity for hydrogenation of both C=C and -NO2 groups both increase after a long time reaction when the reaction conditions are [Ru]= 4mmol/L, [TPPTS]/[Ru]mol ratio=6,PH2=4.0MPa and 90 ℃. Hydrogenation of aromatic ring is not found to occur (or does not occur). The addition of a surfactant (CTAB: cetyltrimethylammonium bromide) rather decreases the hydrogenation activity as well as the selectivity for hydrogenation of both C=C and -NO2 groups although the surfactant (CTAB) would increase hydrogenation activity in general. It is suggested that the steric hindrance of the surfactant micelle formed may decrease the solubility of DMPNE in biphasic catalytic system. Under the best reaction conditions, the conversion of substrate is 98.0%. It's easy to separate the hydrogenation product from the catalyst after the reaction .In biphasic catalytic system (liquid/solid phase), the conversion rises and the selectivity for hydrogenation of both C=C and -NO2 groups increases after 5 hours reaction when the reaction conditions are Ru = 0.049mmol, PH2=5.0MPa and 150 ℃. Under optimized condition, the conversion of DMPNE hydrogenation catalyzed by Ru-Pd/C, Ru/Al2O3, Ru-Pd/Al2O3 reaches 90% but the selectivity of DMPEA is lower.