Abstract
For the synthesis of bio-dimethyl ether (DME) from woody biomass via gasification, we have developed and promoted the biomass-to-liquid (BTL) process. This process consisted of oxygen-enrichment gasification of woody biomass by a bench-scale fixed-bed gasifier, wet gas cleaning, gas compression, desulfurization, removal of CO2, DME synthesis reaction by a fixed-bed reactor. The composition obtained at gasification step was as follows: 25.6 vol% of H2, 31.2 vol% of CO, 2.7 vol% of CH4, 0.4 vol% of CO2, 40.1 vol% of N2, <5 ppb of H2S, and <5 ppb of COS. In the DME synthesis step, DME was synthesized via methanol synthesis and following dehydration reaction in a fixed-bed reactor using the Cu-Zn catalyst for methanol synthesis and γ-Al2O3 catalyst for dehydration. It was found that the Cu-Zn and γ-Al2O3 catalysts exhibited higher activity when used as mixed powder form than used as separated pellet form. DME concentration 5.2 vol% in the product gas was obtained under the following conditions: 0.98 MPa, 230 °C, W/F=37.9 cat.-kg h/m3. It was possible to recover the almost all DME in the gas phase by using the activated carbon trap with dry ice. Finally, we succeeded in the continuous synthesis of DME over 200 h and recovery of approximately 120 g of liquefied bio-DME.
