Distributed production of DME based fuels using microwave technology and direct catalytic synthesis Roger Ruan, Professor and Director Paul Chen, Associate Research Professor and Program Director Qinglong Xie, Peng Peng, Shiyu Liu, Bo Zhang, Erik Anderson, Yanling Cheng, Yuhuan Liu Center for Biorefining and Department of Biosystems and Bioproducts Engineering and Kasiviswanathan Muthukumarappan, Distinguished Professor South Dakota State University

Dimethyl ether (DME) The simplest ether Boiling point: -24 ºC, it is a colorless gas at room temperature Relatively non-toxic

Applications Chemical feedstock Production of dimethyl sulfate CH3OCH3 + SO3 → (CH3)2SO4 The largest use of DME Consumes several thousand tons of DME annually

Applications Laboratory reagent and solvent DME is a low-temperature solvent and extraction agent Applicable to special laboratory procedures Its usefulness is limited by its low boiling point

Applications Fuel in household and industry DME can be used in diesel engines to increase the cetane number As substitute for propane Very low emissions of NOx, CO and sulfur

DME synthesis Methanol synthesis: 2 H2 + CO → CH3OH Catalyst: Cu-ZnO-based catalyst Methanol dehydration: 2 CH3OH → CH3OCH3 + H2O Catalyst: solid acid catalyst, such as γ-Al2O3, zeolites

DME synthesis 2 H2 + CO → CH3OH 2 CH3OH → CH3OCH3 + H2O DME can be produced using two-step method or single-step method. Single-step DME synthesis can overcome the equilibrium limitation in syngas to methanol process. It has thermodynamic and economic advantages over two-step DME synthesis.

Overall goal To develop a single-step method for distributed production of DME from biomass-derived syngas. 8

Specific objectives Produce high-quality syngas from biomass through fast microwave-assisted gasification (fMAG) Further improve syngas quality through cleaning and conditioning processes Study single-step synthesis of DME from syngas Examine the effect of zeolite type on the syngas-to-DME process 9

Distributed production of DME from biomass-derived syngas Overall process Fast microwave-assisted gasification Syngas cleaning and purification Effect of zeolite type Single-step DME synthesis Biomass Syngas

Distributed production of DME from biomass-derived syngas Overall process

Fast microwave-assisted biomass conversion system 12

Fast microwave-assisted gasification (fMAG) 13

Proximate analysis (wt.%) Elemental analysis (wt.%) fMAG of corn stover Characteristics of corn stover Proximate analysis (wt.%) Elemental analysis (wt.%) Moisture 5.3 C 40.38 Volatile 81.9 H 5.16 Fixed Carbon 10.7 N 0.38 Ash 2.1 O 52.01 Fe/Al2O3, Co/Al2O3, Ni/Al2O3 will be used as the catalysts.

fMAG: Effect of catalyst type on product distribution

fMAG: Effect of catalyst type on gas composition

fMAG: Effect of catalyst to feed ratio

Gas cleaning and purification Gasifier Tars, H2S, NH3 sorbents O2 trap Molecular sieve or Silica gel Particle filter

Gas cleaning and purification systems

Gas cleaning and purification Concentrations of impurities before and after cleaning Impurities Tar O2 NH3 H2S+COS Before cleaning 500-3000 ppm 0.1-2% 200-1000 ppm 200-400 ppm After cleaning < 1 ppm < 0.1 ppm < 1 ppb

Single-step synthesis of DME from syngas After purification, the syngas from biomass gasification can then be converted to DME. Temp.: 260 ºC Pressure: 50 bar Catalyst: Cu-ZnO-Al2O3 & zeolite (Bifunctional)

Single-step synthesis of DME from syngas

Effect of zeolite type on DME synthesis Different zeolites were used as methanol dehydration catalyst

Single-step synthesis of DME from syngas Characterization of zeolites No. Product name Type Framework type Si/Al ratio Pore size (Å) BET surface area (m2/g) 1 CBV28014 H-ZSM-5 MFI 280 5.6×5.3, 5.5×5.1 400 2 CBV8014 80 425 3 CBV3024E 30 405 4 CBV400 H-Y FAU 5.1 7.4×7.4 730 5 CBV780 780 6 CP811C-300 H-Beta BEA 300 7.6×6.4, 5.6×5.6 620 7 CP914C H-Ferrierite FER 20 4.2×5.4, 3.5×4.8

Single-step synthesis of DME from syngas Effect of zeolite type on DME synthesis No. Catalyst CO conversion (%) Selectivity (%) DME yield (g·kgcat-1·h-1) DME CH3OH CO2 1 CZA-CBV28014 44.6 70.4 24.5 5.2 161.0 2 CZA-CBV8014 65.5 62.9 24.9 12.3 211.2 3 CZA-CBV3024E 87.8 65.9 3.4 30.7 297.0 4 CZA-CBV400 91.9 63.9 3.0 33.1 301.7 5 CZA-CBV780 50.6 23.3 64.5 12.2 60.6 6 CZA-CP811C-300 30.0 25.9 64.1 9.9 40.0 7 CZA-CP914C 93.0 61.4 2.8 35.8 293.4

Single-step synthesis of DME from syngas NH3-TPD profiles for the bifunctional catalysts The dehydration activity of zeolite is determined by its surface acidity. Temperature programmed desorption

Single-step synthesis of DME from syngas Surface acidity of catalysts as determined by NH3-TPD No. Catalyst Density of acid sites (µmol NH3/g) Density of acid sites (µmol NH3/g) T1 T2 T3 T4 Total Weak Strong 1 CZA-CBV28014 465.8 266.4 – 242.6 974.8 509.0 2 CZA-CBV8014 345.5 128.2 284.8 225.1 983.6 638.1 3 CZA-CBV3024E 955.6 961.4 518.9 2435.9 1480.3 4 CZA-CBV400 722.2 547.4 434.7 1704.3 982.1 5 CZA-CBV780 432.8 205.6 221.0 338.7 1198.1 765.3 6 CZA-CP811C-300 337.3 383.0 364.4 1084.7 747.4 7 CZA-CP914C 720.0 679.8 344.3 1744.1 1024.1 Methanol synthesis: 2 H2 + CO → CH3OH Acid sites help methanol dehydration Methanol dehydration: 2 CH3OH → CH3OCH3 + H2O

Single-step synthesis of DME from syngas CO conversion as a function of time on stream (TOS) The catalyst stability is also influenced by zeolite type.

Conclusions Syngas of high yield and quality was obtained from fast microwave-assisted gasification (fMAG) of biomass. The impurities in syngas were removed by gas cleaning and purification processes. DME was produced from biomass-derived syngas using single-step method with different zeolites. 29

Acknowledgments: Related Group Members and Collaborators: B. Polta, J. Willett, A. Sealock, R. Hemmingsen, P. Chen, M. Min, W. Zhou, M. Mohr, Y. Chen, L. Wang, Yecong Li, Bing Hu, Q. Kong, X. Wang, Y. Wan, K. Hennessy, Y. Liu, X. Lin, Yun Li, Y. Cheng, S. Deng, Q. Chen, C. Wang, Y. Wang, Z. Du, X. Lu, Z. Wang, R. Griffith, J. Thissen, Q. Xie, Y. Nie, F. Borge, F. Hussain, Y. Jiang, Y. Sun, Z. Fu, R. Zhu, A. Olson, B. Martinez, B. Zhang, J. Zhu, B. Hu, L. Schmidt, D. Kittelson, R. Morey, D. Tiffany, F. Yu, H. Lei, X. Ye, M. Muthukumarappan, P. Heyerdahl, …… Funding Agencies: 30

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