Surface structure of F-treated La1.8Ca0.2Mg14Ni3La1.8Ca0.2Mg14Ni3 alloy and hydrogenation properties of solid–liquid system composed of the alloy and benzene

The hydrogenation properties of the solid–liquid (slurry) system of the F-treated La1.8Ca0.2Mg14Ni3La1.8Ca0.2Mg14Ni3 alloy and C6H6C6H6 were investigated. The solid La1.8Ca0.2Mg14Ni3La1.8Ca0.2Mg14Ni3 was treated previously with the solution of NH4FNH4F and deionized water. The concentration of NH4FNH4F varied from 0.03 to 0.15 mol/L in steps. After treatment, a new compound that is snowlake-shaped is wholly covered on the surface of the treated alloy. The XPS and AES analysis indicated that MgF2MgF2 and metallic La are concentrated at the top of the surface and the oxygen content is substantially decreased; and at the outmost layer of the surface, the content of nickel is very low. The appearance of the surface greatly improved the hydrogen absorption of alloy in slurry and the catalytic activity of alloy catalyzing C6H6C6H6 to C6H12C6H12. The hydrogenation rate of solid–liquid system composed of benzene and F-treated alloy is much higher than the slurry composed of an equal amount of untreated as-cast alloy. Under the best treatment condition, the slurry composed of 20 wt% alloy and 80 wt% benzene absorbs 6.5 mass% hydrogen in 3–4 min at 483 K and under 4.0 MPa hydrogen pressure.