Selective ethanol synthesis via multi-step reactions from syngas: Ferrierite-based catalysts and fluidized-bed reactor application

Selective ethanol synthesis from syngas through cascade multi-step reactions via methyl acetate (MA) intermediate route was investigated using a highly crystalline ferrierite (FER) zeolite and hybridized bifunctional Cu-ZnO-Al₂O₃/FER (CZA/FER). The extent of crystallinity of the FER zeolites played crucial roles for catalytic activities of syngas conversion to dimethyl ether (DME), DME carbonylation to MA and MA hydrogenation to ethanol. With an increase of crystallinity of FER, DME productivity by CO₂ (or CO) hydrogenation was largely enhanced due to a fast dehydration rate of methanol to DME on the CZA/FER having a large surface area of metallic copper nanoparticles. The bifunctional CZA/FER was utilized to convert MA to ethanol up to the similar equilibrium yield of ∼42 mol%. In addition, highly crystalline of FER@FER, which was synthesized by using a FER seed, showed a higher DME conversion to MA and stability due to the abundant presence of Bronsted acid sites with less defect sites. To verify the possible integration of two series cascade reactions such as direct syngas conversion to DME and its consecutive carbonylation to MA, the segregated double-layer formation in one bubbling fluidized-bed reactor was simulated. Two catalytic reaction regions with a light and dense-phase at similar reaction conditions were completely segregated at optimal linear velocity ranges (minimum fluidizing velocity, U_mf) by using two different catalyst particle sizes having an average size of 112.5 and 82.5 μm in a bottom and upper reaction zone, respectively.