Synthesis of dimethyl ether from syngas using a hierarchically porous composite zeolite as the methanol dehydration catalyst

Hierarchically porous composite zeolite (BFZ, with Beta zeolite cores and Y zeolite polycrystalline shells) was employed as the methanol dehydration catalyst in the direct synthesis of dimethyl ether (DME) from syngas in a fixed-bed reactor. The correlation between the catalytic activity and the textural and acid properties of the dehydration catalyst was investigated. The results indicate that the composite zeolite of H-form (HBFZ) exhibits moderate acid strength and meso-porosity, which is responsible for the high activity of CO hydrogenation. For the direct synthesis of DME from CO hydrogenation over the physical mixture of commercial CuO/ZnO/Al₂O₃ catalyst (CZA) and the H-form zeolites (HBFZ or HY), CZA/HBFZ exhibits higher activity and stability than CZA/HY. Under 250 ℃, 5.0 MPa and 1 500 h^-1, the conversion of CO and the selectivity to DME over CZA/HBFZ achieve 94.2% and 67.9%, respectively.