(379e) The Upgrading of Biomass-Derived Dimethyl Ether to High-Octane Hydrocarbons: The Effect of Process Conditions on Catalyst Performance

Dimethyl ether (DME) and/or methanol can be converted into C₅₊ branched hydrocarbons at low temperatures and pressures over large-pore acidic zeolites. Recently, we have demonstrated that Cu-modification of the existing commercial catalyst (H-BEA) resulted in a 2-fold increase in total hydrocarbon productivity at 200 °C with co-fed H₂.¹ The Cu/H-BEA catalyst incorporated H₂ with DME into the desired branched hydrocarbons, while maintaining the high C₅₊ selectivity of the parent H-BEA. Here, we compare the performance of Cu/H-BEA and the parent H-BEA at 175, 200 and 225 °C, and at weight-hourly space velocities (WHSV) for DME ranging from 0.43-1.4 h^-1. The productivity of C₅₊ products increased with temperature over H-BEA, with no significant changes over Cu/H-BEA due to a decrease in C₅₊ selectivity at elevated temperature, which was observed for both catalysts. Operation at 175 °C resulted in a significant increase in C₅₊ selectivity (75-85% for Cu/H-BEA), but lower productivity than at 200 °C due to lower reactant conversion. Lower space velocities increased reactant conversion over both catalysts, but significantly decreased the C₅₊ productivity over Cu/H-BEA. The Cu/H-BEA catalyst was stable for 100 h at 200 °C after an initial 40 h break-in period. In previous research, we demonstrated that C₄-C₈ olefins produced in the DME homologation reaction can be oligomerized to C₁₂-C₂₂ branched hydrocarbons with properties that align with a synthetic paraffinic kerosene product.² Following a simple vacuum distillation, the fuel properties of the distillate-range product align well with a jet fuel blend when compared with 5 ASTM methods. This DME-to-hydrocarbons reaction represents a promising route to transform renewable biomass sources into commercially viable, high-performance biofuels.³

¹Schaidle, J. A.; Ruddy, D. A.; Habas, S. E.; Pan, M.; Zhang, G.; Miller, J. T.; Hensley, J. E. ACS Catal. 2015, 5, 1794.

²Behl, M.; Schaidle, J. A.; Christensen, E.; Hensley, J. E. Energy & Fuels 2015, 29, 6078.

³Tan, E. C.; Talmadge, M.; Dutta, A.; Hensley, J.; Snowden-Swan, L. J.; Humbird, D.; Schaidle, J.; Biddy, M. Biofuels, Bioproducts and Biorefining 2016, 10, 17.