A high-pressure fixed-bed reactor has been used for the direct synthesis of dimethyl ether (DME) from syngas, through a single-step process using a CuO-ZnO-MnO/SAPO-18 (CZMn/S) bifunctional catalyst. The effects of temperature (250-350 degrees C), space time (2.5-20 g(cat) h (mol(c))(-1)), reaction pressure (20-40 bar) and time on stream have been studied. The results show that suitable conditions for attaining high yield and selectivity of DME are 275-300 degrees C, with moderate reaction pressure (30 bar). For space time values above 5 g(cat) h (mol(c))(-1), the catalyst acquires a pseudo-steady state of constant activity. The need of purifying the syngas feed (free of olefins and/or paraffins) in order to avoid the activation of the hydrocarbon pool has also been evidenced. Deactivation of CZMn/S is mainly caused by coke deposition, and three types of coke are distinguished based on its location on the catalyst: i) metal surface, ii) interface metal-MnO, and acid function. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.