Pilot-Scale Tests of Direct Dimethyl Ether Synthesis from Biomass-Derived Syngas

Direct conversion of biomass-derived syngas to dimethyl ether (DME) at pilot-scale of 100 t/a was carried out in a fixed-bed tubular reactor over Cu/Zn/Al/HZSM-5 catalyst. The bio-syngas was obtained by pyrolysis and gasification of corncob under O₂-rich air in fixed-bed reactors. The effects of gasification, synthesis temperature and gas hourly space velocity (GHSV) of bio-syngas on DME synthesis were investigated with the corncob feedrate of 45~50 kg/h. The results shows that H₂/CO ratio of the obtained bio-syngas was around 1. CO conversion was 75.2% under optimized synthesis temperature of 270degC and GHSV of 1200 h^-1. CO conversion and space-time yield of DME were in the range of 82.0~67.7%, 124.3~281.2 kgldrm_cat ^-3ldrh^-1 respectively when GHSV was between 650 h^-1 and 3000 h^-1 under 4.3 MPa and 260degC. Cu (111) was considered to be the active phase for DME synthesis, confirmed by X-ray diffraction (XRD) characterization.