Gas/liquid oligomerization reactor having successive zones with variable diameters

A gas/liquid oligomerization reactor comprising:

• a reaction chamber (1), of elongate shape along a vertical axis,
• a means for introducing gaseous ethylene (2), located in a bottom of the reaction chamber,
• a means for withdrawing (5) a reaction liquid effluent, located in the bottom of the reaction chamber, and
• a means for purging (4) a gaseous fraction, located at the atop of said reactor;
• wherein
• said chamber is composed of n consecutive zones having a diameter Dn which decreases in the direction from a bottom zone to a top zone of said chamber,
• the ratio (Dn/Dn−1) of the diameter of an upper zone Dn, to the diameter of an adjacent lower zone Dn−1, is less than or equal to 0.9,
• for a given zone, the ratio of the volume Vn, to the total volume of the reaction chamber, Vtot, (Vn/Vtot) is between 0.2 and 0.8,
• the n consecutive zones are placed in series along a vertical axis of the reaction chamber reactor so as to define zones in the reaction chamber having diameters that decrease from a bottom of the reaction chamber to a top of the reaction chamber and thus to increase the height of a liquid phase that can be contained in said reaction chamber compared to a height of a constant-diameter reactor.