14 



THE ROYAL SOCIETY OF CANADA 



Experiment 7. 



It was of interest to know whether unreduced nickel oxide is 

 active or not for catalysing the union of ethylene with hydrogen. The 

 nickel material was accordingly heated with oxygen for a long time at 

 240°C. The free oxygen was expelled by nitrogen and a mixture of 

 210 c.c. hydrogen and 95 c.c. ethylene passed at 150°. For half an 

 hour there was only a small change in volume and it appeared that 

 the action was going to be very slow when suddenly a reduction in 

 volume of 95 c.c. occurred, and simultaneously water was seen to 

 pass over into the absorbers. In other words, there was no indication 

 of hydrogénation until there was evidence of reduction. Nickel oxide 

 cannot catalyse the union of hydrogen and ethylene until some 

 reduction has occurred, which, as has already been pointed out, is 

 accompanied by the absorption of hydrogen to form a hydrogen- 

 hydroxyl complex on the surface of the particles. This experiment 

 was repeated with exactly the same observations. 



This experimental data appears to receive an adequate repre- 

 sentation by the following mechanism: 



Nickel oxide partially reduced at a low temperature consists of 

 particles of nickel oxide surrounded by metallic nickel carrying 

 positive hydrogens and negative hydroxyls alternately arranged on 

 the surface in several layers, thus with only one layer of hydrogen and 

 hydroxyls represented — 



Q 



.Ni 



H + 

 OH- 

 H + 

 OH- 



When this complex catalyses the union of hydrogen and ethylene 

 four reactions occur: 



"•/ A VERY FAST REACTION 



Ni\ 



II . Ni 



H^ 



-H 



\ PH- , . 



I 



Ni' 

 II 



N, 



H' 

 OH 



--hC^Hs-hHsO 



2 A \/£RY SLOW ffEACr/OA/ 



OH- 



H^ 



\0H- 



jhr!\-H- 



Ni 



^^t' -^ H,0 



H- 

 I 



