100 t/a-Scale demonstration of direct dimethyl ether synthesis from corncob-derived syngas

Direct conversion of biomass-derived syngas (bio-syngas) to dimethyl ether (DME) at pilot-scale (100 t/a) was carried out via pyrolysis/gasification of corncob. The yield rate of raw bio-syngas was 40–45 Nm3/h with less than 20 mg/Nm3 of tar content when the feedrate of dried corncob was 45–50 kg/h. After absorption of O2, S, Cl by a series of absorbers and partial removal of CO2 by the pressure-swing adsorption (PSA) unit sequentially, the obtained bio-syngas (H2/CO≈1) was directly synthesized to DME over Cu/Zn/Al/HZSM-5 catalyst in the fixed-bed tubular reactor. CO conversion and DME space-time yield (STY) were 67.7% and 281.2 kg/mcat3/h respectively at 260 °C, 4.3 MPa and 3000 h−1(GHSV, syngas hourly space velocity). Synthesis performance would be increased if the tail gas (H2/CO > 2) was recycled to the reactor when GHSV was 650–3000 h−1.