Modeling and simulation are discussed in this paper. Continuous System Modeling Program (CSMP) has been introduced to solve the simulation, some mathematical aspects arise is briefly discussed. To show the simplicity of using CSMP some simple models have been solved. An application to a more complex model is shown, that is, to solve the dimerisation of butadiene, a homogeneous gas- phase reaction, in a packed-bed tubular reactor using two dimensional models. This is a preliminary work in order to apply the program to a model of heterogeneous catalytic reaction.