Dimethyl ether (DME) is a clean and colorless gas that has remarkable potential for use as an automotive fuel and in domestic applications. DME is commercially produced by methanol dehydration reaction that uses solid acid catalysts. Among the catalysts, γ-alumina and HZSM-5 are extensively studied and they have attracted a great deal of attention as potential catalysts because of their high activity and proper stability. In this book, it is attempted to find suitable rate of reactions over HZSM-5 and γ-alumina at industrial conditions. In addition, a comparison between the performances of the catalysts is performed. It is found that HZSM-5 has superior performances compared to the γ-alumina in terms of conversion. Modeling results are also indicated that the proposed rate of reaction predicts the behavior of the process, properly. Therefore, the vapor phase DME synthesis is simulated by Hysys process simulation software and relevant cost analysis is also conducted and some new processes are investigated to reduce capital and operating costs. Moreover, the HZSM-5 material is modified by aluminophosphate catalyst to improve its activity and retarding hydrocarbon formation.