Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-III-18of 2. MSR has been coupled with CH 4 combustion for heating purposes. The rate expressionproposed by Kolaczkowski et al. [4] for CH 4 combustion in excess air at atmospheric pressureover PdO was adopted. Complete CH 4 combustion (1wt. % in air) is guaranteed in themicrochannels at GHSV as high as 214,290 h –1 with negligible pressure drop. In the case ofthe FT synthesis microreactor GHSV in the 5,000-10,000 h –1 range have been considered forthe syngas stream (H 2 /CO molar ratio of 2). The synthesis reaction has been modelled as aheat source on the walls, coupled with the partial boiling of water in neighbour microchannelsfor heat removal.Isothermal block at750ºC and 1 atmLiquid waterMSRmicrochannelMethane combustionmicrochannelIsothermalFTS at 218ºCand 15 atm18 wt% steamFigure 1. MSR and CH 4 combustion in two neighbourmicrochannels in parallel arrangementFigure 2. FTS coupled with partial boiling of waterat 15 atm in the micoreactor (crossed flow).It has been found that for both MSR (Figure 1) and FT synthesis (Figure 2) reactionsisothermal operation can be achieved at temperatures in the 750-900 °C and 200-250 °Crange, respectively. Methane conversions close to the equilibrium values are obtained at theMSR microchannels outlet. Isothermal MSR operation can be achieved by adjusting the spacevelocity and/or concentration of the CH 4 -air mixture although a sufficiently high inlettemperature is required. A great influence of the microchannels arrangement has been foundin this case. As concerns the FT synthesis, isothermicity can be achieved by setting theoperating pressure at a value (10-39 atm) at which the boiling point of water is slightly belowthe temperature at which the synthesis reaction has to be carried out.AcknowledgementsWe gratefully acknowledge financial support of this work by Petróleo Brasileiro S.A. –PETROBRAS and Spanish Ministry of Education and Science (MAT2006-12386-C05-01,-02 and -04).References1. E.F. Sousa-Aguiar, L. Gorestin Appel, C. Mota, Catal. Today 101 (2005) 3.2. K.T. Jarosch, A.L.Y. Tonkovich, S.T. Perry, D. Kuhlmann, Y. Wang. In Microreactor Technology and ProcessIntensification; ACS Symposium Series 914, American Chemical society, Washington, 2005, p. 258.3. J.R. Rostrup-Nielsen. Catalytic Steam Reforming. In Catalysis, Vol. 5; Springer-Verlag, Berlin, 1984, p. 1.4. R.E. Hayes, S.T. Kolaczkowski. Catalytic Combustion; Gordon and Breach, Amsterdam, 1997, p. 622.126