REACTIVITY OF NICKEL PARTICLES HIGHLY DISPERSED ON ZEOLITES EXCHANGEDBY ION CE3+ OR EU3+

The composition of zeolitic support in Ni2+ zeolite X systems (acidity , presence of other ions) has closely effect in the obtention of a hig hly dispersed metallic state of nickel. Hydrogenolysis, methanation an d chemisorption properties of nickel are closely depending of particul e size. These properties are extenuated when particule sizes are 12 an gstrom or below this diameter. A temperature-programmed desorption stu dy of these systems showed the presence of a ''hydrogen-species'' phas e strongly chemisorbed to the particules of catalyst which avoids any contact between activated sites and reagents.