In this paper, a third-generation dry gas-to-ethylbenzene process in a factory of PetroChina is considered. For the gradual catalyst deactivation in the alkylation reactor, a model is established with the parameters estimated from the reaction rate equation of alkylation based on the on-site data and those from laboratory analysis. The real-time dynamic simulation of the alkylation process is carried out, in which the module accuracy is ensured by using OPC (Object linking and embedding for Process Control) technique and adaptive correction of model parameters. Both the current and future operation temperature can be predicted.