Starting from a rigorous and comprehensive kinetic model, three types of reactors are investigated as to their performance in MTO; a multi-tubular quasi-isothermal reactor, a multi-bed adiabatic reactor with intermediate heat exchangers, and a bubbling fluidized bed reactor with internal heat exchanger. For each type, extensive simulation led to optimal design and operation, guaranteeing the desired ratio of ethylene to propylene and keeping the deactivation of the catalyst under control. The final selection is a matter of economics and reliability. The availability of kinetic models for MTO on SAPO-34 and on ZSM-5 also allowed a comparison of the yields achieved with those catalysts in a multi-bed adiabatic reactor.