Evaluation of Catalyst Deactivation during Catalytic Steam Reforming of Biomass-Derived Syngas
| Autor: | Calvin Feik, Richard J. French, Richard L. Bain, Kimberly A. Magrini-Bair, Stefan Czernik, Steven D. Phillips, Daniel Carpenter, David C. Dayton |
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| Rok vydání: | 2005 |
| Předmět: | |
| Zdroj: | Industrial & Engineering Chemistry Research. 44:7945-7956 |
| ISSN: | 1520-5045 0888-5885 |
| DOI: | 10.1021/ie050098w |
| Popis: | Mitigation of tars produced during biomass gasification continues to be a technical barrier to developing systems. This effort combined the measurement of tar-reforming catalyst deactivation kinetics and the production of syngas in a pilot-scale biomass gasification system at a single steady-state condition with mixed woods, producing a gas with an H2-to-CO ratio of 2 and 13% methane. A slipstream from this process was introduced into a bench-scale 5.25 cm diameter fluidized-bed catalyst reactor charged with an alkali-promoted Ni-based/Al2O3 catalyst. Catalyst conversion tests were performed at a constant space time and five temperatures from 775 to 875 °C. The initial catalyst-reforming activity for all measured components (benzene, toluene, naphthalene, and total tars) except light hydrocarbons was 100%. The residual steady-state conversion of tar ranged from 96.6% at 875 °C to 70.5% at 775 °C. Residual steady-state conversions at 875 °C for benzene and methane were 81% and 32%, respectively. Catalytic deactivation models with residual activity were developed and evaluated based on experimentally measured changes in conversion efficiencies as a function of time on stream for the catalytic reforming of tars, benzene, methane, and ethane. Both first- and second-order models were evaluated for the reforming reaction and for catalyst deactivation. Comparison of experimental and modeling results showed that the reforming reactions were adequately modeled by either first-order or second-order global kinetic expressions. However, second-order kinetics resulted in negative activation energies for deactivation. Activation energies were determined for firstorder reforming reactions and catalyst deactivation. For reforming, the representative activation energies were 32 kJ/g‚mol for ethane, 19 kJ/g‚mol for tars, 45 kJ/g‚mol for tars plus benzene, and 8-9 kJ/g‚mol for benzene and toluene. For catalyst deactivation, representative activation energies were 146 kJ/g‚mol for ethane, 121 kJ/g‚mol for tars plus benzene, 74 kJ/g‚mol for benzene, and 19 kJ/g‚mol for total tars. Methane was also modeled by a second-order reaction, with an activation energy of 18.6 kJ/g‚mol and a catalyst deactivation energy of 5.8 kJ/g‚mol. |
| Databáze: | OpenAIRE |
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