A process comprising selective oligomerization of ethylene to give a linear alpha-olefin, carried out at a pressure of between 0.1 and 10 MPa, at a temperature of between 30 and 200° C., in a cascade of N gas/liquid reactors in series, N being at least equal to 4, comprising the following:
- a. introducing a homogeneous catalytic oligomerization system comprising at least one metal precursor, optionally at least one activator and optionally at least one additive into at least the first reactor of the cascade,
- b. bringing said homogeneous catalytic system and an optional solvent into contact with ethylene by introducing said ethylene into the lower part of the reaction chamber of each of the N reactors of the cascade, with the exception of the last reactor in the cascade,
- c. for each reactor n, withdrawing a liquid fraction in the lower part of the reaction chamber of the reactor n, the liquid fraction being separated into two streams:
- a first stream corresponding to a first part of the liquid fraction, which is conveyed to a heat exchanger for cooling;
- a second stream corresponding to the second part of the liquid fraction which constitutes the liquid feedstock of the following reactor n+1 in the cascade,
- d. introducing said second part of the liquid phase withdrawn from the reactor n towards the reaction chamber of the following reactor n+1 in the direction of flow, comprising a liquid phase and a gas phase,
- e. cooling said first part of the liquid fraction withdrawn from the reactor n in c) by passing said first part of the liquid fraction into a heat exchanger in order to obtain a cooled liquid fraction,
- f. introducing said liquid fraction cooled in e) at the top of the reaction chamber of said reactor n, a) to f) being carried out, unless indicated otherwise, for each reactor n of the cascade, n being between 1 and N.