A continuous intensified reactor requires precise information to adapt the design to the reaction to be implemented. In this article we present a two step approach to pre-designing such devices. The first step consists of the optimisation of the operating conditions based only on stoichio-chemical schemes and kinetic laws. This is carried out by adjusting the temperature profile and feeding rate strategy in a batch or pseudo-batch operation. The second step departs from the ideal thermo-kinetic path by taking into account heat removal and reagent injection. A simulator is used to evaluate the impact of these constraints on the selectivity and productivity. The approach is applied to the linear alkylbenzene sulfonation which characteristics present most of the challenges encountered in the intensification. Final results give a pre-design in terms of reactor characteristics (size, injections positions) and operating conditions.