Novel fixed-bed Raney nickel catalysts(II) Leaching procedures of alloy extrudates
A novel activated fixed-bed Raney nickel catalyst was p repared by extruding Ni-Al alloy powder with 20% pseudo-boehmite as binding ma terial. Appropriate leaching conditions of calcined alloy extrudates were studie d by using of benzene hydrogenation activity as the main evaluation factor.Leach ing procedures of such calcined alloy extrudates were also tested by contrast wi th alloy powder,in which released hydrogen and dissolved aluminum in caustic sol ution were determined.The experimental results showed that the fixed-bed Raney nickel catalyst could achieve higher benzene hydrogenation activity by leaching the alloy extrudates calcined at 860℃ for 2 h with 10%—20% NaOH soluti on at 80—90℃ for 3—4 h, and that the leaching procedures had significant effe ct on catalyst compressive strength. The metallic aluminum in calcined alloy ext rudates could almost dissolve completely in caustic solution within 1—4 h, and microporous structures appeared on the surface of leached catalysts appear. The results of benzene hydrogenation suggested that the novel fixed-bed Raney nicke l catalysts showed higher hydrogenation activity and stability, and that benzene could be hydrogenated to cyclohexane completely at mild conditions of reaction temperature 120 ℃, hydrogen pressure 0.5 MPa and space velocity 2 h -1 .