Catalytic Hydrogenation Activity of a ZrNi sub 3 Intermetallic Alloy

摘要

The catalytic hydrogenation activity of a ZrNi sub 3 intermetallic alloy has been determined and has been found to be more active than either pure Ni or Pt for the hydrogenation of ethylene to ethane. The ZrNi sub 3 , prepared by arc melting, was powdered and sieved (-200, +325 mesh) and tested in a microcatalytic reactor. Ni and Pt were also studied. Results indicate that from 30 to 120 sup 0 C the relative hydrogenation activities are ZrNi sub 3 > Pt > Ni for this reaction. Over this temperature range the apparent activation energies were found to be: ZrNi sub 3 = 7.1 kcal/mole; Pt = 11.5 kcal/mole; and Ni = 7.0 kcal/mole. Above approx.100 sup 0 C the activity of the ZrNi sub 3 begins to decline (as does that of Pt from previous studies). Upon pretreating the ZrNi sub 3 in an O sub 2 /He stream at 400 sup 0 C for two hours followed by a two-hour treatment in H sub 2 at 400 sup 0 C the activity increased and the apparent activation energy decreased to 0.75 kcal/mole. A further treatment at 550 sup 0 C caused the apparent activation energy to decrease to 0.40 kcal/mole. Both of these Q sub 2 treatments also resulted in an enhanced stability of the alloy with regard to its time-on-stream activity and in its activity temperature maximum being extended to approx.140 sup 0 C. The catalytic activity of ZrNi sub 3 is due to an O sub 2 induced decomposition into a NiO/ZrO sub 2 mixture residing on an inner core of ZrNi sub 3 alloy. Upon reduction the active catalyst is reduced Ni dispersed on ZrO sub 2 which, in turn, is present as a thin film on the ZrNi sub 3 core. (ERA citation 12:000734)