A method for controlling the pseudo-isothermicity of a chemical reaction in a respective reaction zone. (9) in which the use of heat exchangers (6) is foreseen having an operating heat exchange fluid flowing through them and in which heat exchange critical areas (9a) are identified, the method being distinguished by the fact that it reduces and controls, in the critical areas (9a) of the reaction zone, the value of the heat exchange coefficient between the operating fluid and the zone (9), through thermal insulation of the portions (6a, 6b) of such exchangers extending in such areas (9a).