Abstract Nickel exchanged zeolite has been reported to be active for ethylene oligomerization. However, there are very few detailed reports on the kinetics of reaction. Our work is focused on the effect of temperature (50°C to 70°C) and pressure (100 psig to 600 psig) on product yield and selectivity, particularly to 1-butene. A tubular flow reactor operating in a differential mode is used for the kinetic studies. NiNaY is effective for ethylene dimerization to 1-butene. However, the catalyst deactivates rapidly probably due to the formation of oligomers. A first order dependence on ethylene concentration was observed. The apparent activation energy decreased from 58.6 kJ/mol to 42.1 kJ/mol as the time of the catalyst on stream increased. The changing and low activation energy may be attributed to a mixture of mass transfer and chemical controlled reaction. There appears to be a threshold Ni loading at which point the activity per Ni site is increased. This is probably related to the initial migration of Ni2+ to the inactive SI sites of the hexagonal prism of the zeolite. Preliminary results on the modification of NiNaY with picolinic acid suggest that Ni is the active site for ethylene dimerization. The isomerization of 1-butene is caused primarily by the protonic acid sites on the zeolite support.