Production of para-xylene by the methylation of benzene and/or toluene

In a process for the production of para-xylene, methanol is preheated to a first temperature, an aromatic feedstock comprising toluene and/or benzene is preheated to a second temperature and the preheated methanol and aromatic feedstocks are fed to a reactor at a first methanol to aromatic feedstock molar ratio. The preheated aromatic feedstock is contacted with the preheated methanol under alkylation conditions in the reactor in the presence of a catalyst so that the methanol reacts with the aromatic feedstock to produce an effluent comprising para-xylene. During the reaction, a temperature is measured within the reactor and is compared with a predetermined optimal temperature. The methanol to aromatic feedstock molar ratio is then adjusted in a manner to reduce any difference between the measured and predetermined optimal temperatures in the reactor.