The thesis work deals with the techno-economical assessment of the reactor network for methanol synthesis and direct dimethyl ether synthesis from the energy-process integration viewpoint. The reactor network is composed by a water-cooled reactor; a gas-cooled reactor used to preheat the syngas fed to the network; a separation section and a recycle loop. This general configuration is often reduced to the study of the sole water-cooled reactor in literature works. Although such reactor is the key-element of the overall system, the other parts of the process cannot be anymore neglected when the techno-economical assessment is the target of reactor design. Therefore, the so-called systematic staging design methodology proposed by Hillestad, 2010 is adopted to redefine the optimal ratio between the different stages of methanol synthesis reactor network. To do so, the phenomenological mathematical model of the overall system is required together with the solution of the resulting set of ordinary differential equations coupled with algebraic constraints and initial and boundary conditions as well. It means that beyond the cumbersome issues of mathematical modeling to properly characterize the heterogeneous reactors for methanol and dimethyl ether synthesis, a boundary value problem has to be solved iteratively within an optimization procedure. According to what has been described, the model is then implemented into a multivariable, nonlinear optimization routine in order to maximize not only the methanol and/or dimethyl ether production but also the steam generation. It is demonstrated that a revision of the traditional design based on the systematic staging design for the integrated optimization of energy and process yield can increase the net operating margin of a medium size methanol synthesis plant by about 2 M€/y.