Preparation And Application Of Raney Ruthenium-based Hydrogenation Catalyst

RuAl and modified RuAl alloy powders were prepared by high frequency induction furnace and arc furnace. Raney ruthenium (Raney-Ru) and Raney-RuNiC were obtained from the two precursors by leaching Al using NaOH aqueous solution [w(NaOH) = 20 %] respectively. The two catalysts were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Two liquid crystal intermediates and other fine chemical intermediates were produced over the two catalysts above by selective hydrogenation.Among Raney-Ru, Raney nickel (Raney -Ni) and Pd/C [vv(Pd) - 5 %], Raney-Ru was confirmed to be active in liquid phase selective hydrogenation of 4-(trans-4-propylcyclo-hexyl)benzoic acid (3HPA) to produce liquid crystal intermediate 4-(trans-4-propyIcyclo-hexyl)cyclohexylcarboxylic acid (3HHA). Effect of water on activity as well as lifetime of the catalyst and effect of temperature and pressure on reaction were studied. Simultaneously, effect of reactant concentration on reaction and dependence of concentration of reactant on reaction time were investigated. Under optimal reaction conditions: 6 = 90℃, p = 3 MPa, c(3HPA) = 0.2 molL^-1 and 2O) = 1%, conversion of the substrate was up to 100% and selectivity for the desired product was above 98%. Adding suitable amount of water improved lifetime and selectivity of the catalyst. When reaction temperature increased to 130 ℃, selectivity of the catalyst decreased to 95 %.4-(trans-4-Propylcyclohexyl)cyclohexanol was prepared by liquid phase hydrogenation of 4-((trans-4-propylcyclohexyl)phenol over Raney-Ru. Raney-Ru was the most suitable catalyst among Raney-Ni, Raney-Ru, Raney-RuNi, Pd/C [w(Pd) = 5%] and spongy ruthenium powder. Effect of temperature, pressure, concentration of substrate as well as reaction time on reaction were studied. The activity of freshly prepared catalyst was stable after being repeatedly used for 3 times (6 h) and the lifetime of the catalyst was longer than 80 h when used at below 87℃. The suitable reaction temperature was in the range of 80 °C to 90 °C and the suitable reaction pressure was from 1.25 MPa to 1.75 MPa. The concentration of substrate was nearly linear to the reaction time as the concentration of substrate was below 1.274 molL^-1. In addition, the initial concentration of substrate should be below 1.3 molL^-1.Raney-RuNiC [w(Ru): m(Ni): m(C) = 1∶ 1∶ 2] was used as catalyst in liquid phase selective hydrogenation of p-nitroanisole to prepare p-aminoanisole. Activity, durability and selectivity of the catalyst, effect of reaction temperature and pressure on reaction anddependence of concentration of substrate on reaction time were investigated. The activity of freshly prepared catalyst was stable after being repeatedly used for 3 times (6 h), and lifetime of the catalyst was longer than 70 h. The selectivity for desired product was above 99.4% below 100 °C; the suitable range of reaction temperature was from 90 °C to 100 °C; the suitable range of reaction pressure was from 1.1 MPa to 1.5 MPa; the concentration of substrate was nearly linear to reaction time as the concentration of substrate was below 1.72 molL"1.Raney-Ru was also used in hydrogenation of benzene, acetone, /?-ter/-butylphenol and /?-chloronitrobenzene. In addition, freons mixture was analyzed by gas chromatography.