Methanol Conversion to Dimethyl Ether in Catalytic Zeolite Membrane Reactors

In this work, two ZSM-5 type zeolite supported membranes were used as catalytic membrane reactors for dimethyl ether (DME) synthesis via MeOH dehydration. The membranes, both commercial and tubular, had the same ZSM-5 zeolite layers, but a different support each (TiO2 and gamma-Al2O3) and were operated as contactors in through flow configuration. The performance of the two membrane reactors was analyzed as a function of the temperature (150-250 degrees C) and feed pressure (120-300 kPa), spanning a wide range of WHSV (1-13.3 g(MeOH) g(Catalyst)(-1) h(-1)) and feed composition (25-100%(mol) MeOH). The ZSM-5-Al2O3 membrane (Si/Al = 200; porosity of the zeolite layer = 0.2; thickness = 50 mu m; area = 50.6 cm(2)) exhibited always a greater conversion than ZSM-5-TiO2 (Si/Al = 200; porosity of the zeolite layer = 0.2; thickness = 63 mu m; area = 18.8 cm(2)), revealing an influence of the membrane support, correspondent to an additional catalytic effect induced by the Al2O3, which further enhanced the DME production. At 200 degrees C and 1 h(-1), this reactor achieved a MeOH conversion of 86.6 +/- 6.7%, very close to thermodynamic equilibrium conversion. In addition, both membrane reactors showed 100% DME selectivity.