Preparation Of Ru/C And Its Catalytic Properties For Selective Hydrogenation

Ruthenium colloid stabilized by nonionics was prepared by reduction of ruthenium salt at room temperature in aqueous phase. Nano Ru/C catalyst was prepared by absorption of the nonionics-stabilized Ru colloidal particles on active carbon. Ruthenium colloid and nano Ru/C catalyst were characterized by XRD, TEM, ICP, EDX and TG.The nano Ru/C catalyst performed excellently in selective hydrogenation of halonitroaromatics to the corresponding aromatic haloamines. The selectivities of 6 different aromatic haloamines were as high as 99.9% even at 100% conversion of 6 different substrates (p, o, m-chloronitrobenzene, 3, 4-dichloronitrobenzene, 2, 4-dinitrochlorobenzene, 6-chloro-3 -nitrotoluene-4-sulfonic acid). The catalyst also showed excellent catalytic activity (4.38-10.23molH₂/molRumin) in THF media under 110¹35℃ and 3.0MPa, which is much higher than either commercial Ru/C or literature results reported so far.The nano Ru/C catalyst was used in liquid phase selective hydrogenation of p-chloronitrobenzene to p-chloroaniline. The effects of various reaction parameters like amount of Ru loading, solvent, concentration of substrate, reaction temperature and pressure were investigated. No dehalogenation was observed and the selectivity to p-chloroaniline remained 100% under various reaction conditions in the scope of our investigation. Reaction parameters only influenced the reaction rate. The selectivity of p-chloroaniline was kept at 100% even when the conversion of substrate was as high as 100% over the Ru/C catalyst. The extremely high selectivity toward p-chloroaniline was due to the high activity of nano Ru on carbon. When the concentration of p-CNB was below 0.96molL^-1, the hydrogenation rate was independent of the concentration of p-CNB, but it was the function of the partial pressure of hydrogen (P_H2). The rate of the reaction (γ) was calculated using the following formula: 1/γ=1/k b_H2P_H2+1/k. The high catalytic activity 12.8molH₂/molRu·min was obtained in THF media under 110℃ and 3.0MPa. The apparent activation energy of the reaction catalyzed by the nano Ru/C was 90. 1kJmol^-1. The catalyst exhibited extra-long stability, and showed the same activity and selectivity even after 30 times continuous running, suggesting a possibility of future industrial application.The durability and regeneration of nano Ru/C catalyst were investigated in liquid phase selective hydrogenation of 3, 4-dichloronitrobenzene to 3, 4-dichloroaniline. The catalyst...