Directly Printed Oxide/ZSM-5 Bifunctional Catalysts for Methanol Conversion to Dimethyl Ether with Exceptional Stability, Conversion, and Selectivity

Additive manufacturing, otherwise known as 3D printing, is an effective way of generating customizable heterogeneous catalysts. In this study, we utilized direct ink writing of insoluble oxides to produce catalysts with varying metals (i.e., 4 wt % Ga2O3, 4 wt % Ga2O3/4 wt % ZrO2, or 4 wt % Ga2O3/4 wt % V2O5) balanced with H-ZSM-5 for methanol (MeOH) conversion into dimethyl ether (DME). This particular reaction is highly attractive in the petrochemical industry, as DME can be used as an alternative fuel in diesel engines and produces lower emissions. To this end, the printed catalysts were vigorously characterized by a myriad of techniques-including X-ray diffraction, N-2 physisorption, NH3-TPD, H-2-TPR, and elemental mapping-to understand their physiochemical properties. The catalysts were also assessed for MeOH conversion into DME at 200, 300, and 400 degrees C for 5 h using a weight hourly space velocity (WHSV) of 2.6 g(MeOH)/(g(catalyst).h). Between the various samples and temperatures, it was found that 200 degrees C was optimal for all catalysts, as increasing the temperature further led to sizable reductions in DME selectivity. At 200 degrees C, however, the catalysts achieved up to 85% MeOH conversion, 81% DME selectivity, and no deactivation after 5 h. Of the four catalysts, the best behavior was observed in the sample which contained 4 wt % Ga2O3 alongside ZSM-5, where it achieved a staggering 85% MeOH conversion as well as 74% DME selectivity, which is among the highest ever reported to the best of our knowledge. In this regard, this study represents a fundamental breakthrough in DME production and clearly demonstrates a promising new material for this reaction.