Evaluation of Catalyst Deactivation during Catalytic Steam Reforming of Biomass-Derived Syngas

Journal Article · Sat Jan 01 04:00:00 EST 2005 · Industrial and Engineering Chemistry Research

DOI:https://doi.org/10.1021/ie050098w· OSTI ID:981281

Bain, R L; Dayton, D C; Carpenter, D L; Czernik, S R; Feik, C J; French, R J; Magrini-Bair, K; Phillips, S D

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 H{sub 2}-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/Al{sub 2}O{sub 3} 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 first-order reforming reactions and catalyst deactivation. For reforming, the representative activation energies were 32 kJ/g{center_dot}mol for ethane, 19 kJ/g{center_dot}mol for tars, 45 kJ/g{center_dot}mol for tars plus benzene, and 8-9 kJ/g{center_dot}mol for benzene and toluene. For catalyst deactivation, representative activation energies were 146 kJ/g{center_dot}mol for ethane, 121 kJ/g{center_dot}mol for tars plus benzene, 74 kJ/g{center_dot}mol for benzene, and 19 kJ/g{center_dot}mol for total tars. Methane was also modeled by a second-order reaction, with an activation energy of 18.6 kJ/g{center_dot}mol and a catalyst deactivation energy of 5.8 kJ/g{center_dot}mol.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO.
• Sponsoring Organization: USDOE
• DOE Contract Number: AC36-08GO28308
• OSTI ID: 981281
• Journal Information: Industrial and Engineering Chemistry Research, Journal Name: Industrial and Engineering Chemistry Research Journal Issue: 21, 2005 Vol. 44; ISSN IECRED; ISSN 0888-5885
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ACTIVATION ENERGY
Alternative Fuels
BENZENE
BIOMASS
CATALYSTS
CATALYTIC REFORMING
DEACTIVATION
ENERGY
ETHANE
FLUIDIZED BEDS
GASIFICATION
HYDROCARBONS
KINETICS
METHANE
NAPHTHALENE
REACTORS
SIMULATION
SPACE-TIME
STEADY-STATE CONDITIONS
STEAM
STREAMS
TAR
TOLUENE
VISIBLE RADIATION