Effects of Space Velocity on Direct Synthesis of Dimethyl from Synthesis gas

The space velocity had profound effects on dimethyl ether synthesis from syngas over bi-functional catalyst at 513 K and 3.5 MPa. The bi-functional catalyst was prepared by physical mixing of CuO/ZnO/Al2O3 (methanol synthesis catalyst) and H-ZSM-5 (methanol dehydration catalyst) and then characterized by BET, XRD, XRF and TPR analysis. The results indicated that yield of DME as well as the conversion of CO increased continuously with decreasing the space velocity and/ or increasing the residence time of reactants. The main by-products of DME synthesis were water, CO2 and methane. Below a certain space velocity (1100 mln/gr.cat-hr), DME yields and productivities showed a maximum with H2O concentration about 2-10%. Furthermore, it was found that the exit concentration of CO2 has a similar trend as DME yield with decreasing the space velocity. The space velocity that gave the maximal rate of DME production also depended on the H2/CO ratio of feed. In DME synthesis reaction, it was observed that the feed with H2/CO ratio equal to 1.5, have higher activity. For a feed consist of H2 and CO, an optimal space velocity exists for obtaining the kinetic and thermodynamic data for direct synthesis of dimethyl ether.

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Catalysis Research group , Arak center , Petrochemical Research &Technology Company NPC ,