In a 1-step synthesis gas-to-dimethyl ether process, synthesis gas is converted into dimethyl ether (DME) in a single reactor. Three reactions are involved in this process: methanol synthesis, methanol dehydration and water gas shift, which form an interesting reaction network. The interplay among these three reactions results in excellent syngas conversion or reactor productivity. The higher syngas conversion or reactor productivity in the syngas-to-DME reaction_x000D_ system, compared to that in the syngas-to-methanol reaction system, is referred to as chemical synergy. This synergy exhibits a strong dependence on the composition of the reactor feed. To demonstrate the extent of this dependence, simulations with adjusted activity for each reaction were performed to reveal the relative rate of each reaction. The results show that the water gas shift reaction is the most rapid, being practically controlled by the equilibrium. Both methanol synthesis and methanol dehydration reactions are kinetically controlled. The role of the dehydration reaction is to remove the equilibrium barrier for the methanol synthesis reaction. However, the role of the water gas shift reaction is more complex; it helps the kinetics of methanol dehydration by keeping the water concentration low, which in turn enhances methanol synthesis. It also readjusts the H2 : CO in the reactor as the reactions proceed. In the CO-rich regime, the water gas shift reaction supplements the limiting reactant and H2, by reacting water with CO. This enhances both the kinetics and thermodynamic driving force of the methanol synthesis reaction. In the H2-rich regime, water gas shift consumes the limiting reactant, CO, which harms both the kinetics and thermodynamics of methanol synthesis. An understanding of these complex roles of the methanol dehydration and water gas shift reactions and of their dependence on the syngas composition explains why the synergy is high in the CO-rich regime, but decreases with the increasing H2 or CO2 content in the reactor feed. The analysis shows that the optimal H2 : CO for the LPDME reactor is around 1-to-1, in good agreement with the results from the simulation. While the 1-to-1 feed provides a good foundation for some process configurations, it does not match the composition of syngas, which typically has a H2 : CO of 3 : 1 or greater.

Dimethyl Ether LPMEOH LPDME

Chen ZH, Niu YQ, Coal Conversion, 19, 37 (1996)
Fleisch AB, Gradassi MJ, Masin JG, Stud. Surf. Sci. Catal., 107, 117 (1997)
Sills R, Gas to Market Conference, San Francisco, October 11-13 (2000)
Ng KL, Chadwick D, Toseland BA, Chem. Eng. Sci., 54(15-16), 3587 (1999)
Semelsberger TA, Borup RL, Greene HL, J. Power Sources, 156(2), 497 (2006)
Sorenson SC, Journal of Engineering for Gas Turbines and Power-Transactions of the ASME, 123, 652 (2001)
Moradi GR, Nosrati S, Yaripor F, Catal. Commun., 8, 598 (2007)
Huang D, Kang G, Zhang S, Wang X, Natural Gas Chemical Industry, 21, 43 (1996)
Pop G, Cherebetiu T, Boeru R, Ignatescu G, Albulescu V, Proceedings, The Research, Design and Construction of Refrigeration and Air Conditioning Equipment in Eastern European Countries (Bucharest, Sep. 10-13, 1996), 159 (1997)
Ge QJ, Huang YM, Qiu FY, Li SB, Appl. Catal. A: Gen., 167(1), 23 (1998)
Nie Z, Liu H, Liu D, Fang W, Journal of Natural Gas Chemistry, 14, 22 (2005)
Fukunaga T, Ryumon N, Shimazu S, Appl. Catal. A: Gen., 348(2), 193 (2008)
Tan YS, Xie HJ, Cui HT, Han YZ, Zhong B, Catal. Today, 104(1), 25 (2005)
Wang D, Tan Y, Han Y, Noritatsu T, J. Fuel Chem. Technol., 36(2), 171 (2008)
Fujimoto K, Asami K, Shikada T, Tominaga H, Chem. Lett., 2051 (1984)
Zahner JC, Conversion of modified synthesis gas to oxygenated organic chemicals, US Patent, 4,011,275 (1977)
Bharat B, Topical report prepared for DOE by air products and chemicals, Contract No. DE-AC22-90PC89865, September (1992)
Brown DM, Bhatt BL, Hsiung TH, Lewnard JJ, Waller FJ, Catal. Today, 8, 279 (1991)
Gogate MR, Lee S, Kulik CJ, Fuel Sci. Technol. Int., 9, 653 (1991)
Hansen JB, Joensen F, High conversion of synthesis gas into oxygenates, In Natural Gas Conversion Holmen et al. Eds., Elsevier Science B. V., Amsterdam, 457 (1991)
Tao J, Niu Y, Chen Z, Natural Gas Chemical Industry, 16, 17 (1991)
Ohno Y, Shikada T, Ogawa T, Ono M, Mizuguchi M, Fujimoto K, Prepr. Pap. - Am. Chem. Soc., Div. Fuel Chem., 42, 705 (1997)
Bercic G, Levec J, Ind. Eng. Chem. Res., 31, 1035 (1992)