Reaction engineering investigations of CO2 reforming in a fluidized-bed reactor

CO2 reforming of methane to synthesis gas over an Ni (1 wt%)/alpha-Al-2 O-3 catalyst was studied in lab-scale fluidized-bed reactors (ID = 3,5 cm). In the whole range of reaction conditions (p(CH4) = p(CO2) = 25-45kPa, p(N2) = 10-50 kPa, T-R = 700-800 degrees C, H-mf = 3,4,5 cm, m(eat)/V (over dot) = 2.8-7.3 g s ml(-1), u/u(mf) = 6.5-11.8) a stable isothermal operation was achieved. The catalytic performance strongly depended on the oxidation state of the catalyst. When applying a reduced catalyst initial yields of carbon monoxide and hydrogen near the thermodynamic equilibrium were obtained. However, a slow decrease of methane conversion and syngas yield caused by carbon deposition was observed. The fresh unreduced catalyst exhibited significantly lower activity. The in situ reduced catalyst was mom active but yielded CH4 and CO2 conversions lower than predicted by the thermodynamic equilibrium. The reaction was not influenced by interphase gas exchange. Based on these results, reaction engineering modeling and simulation yielded a global kinetic model which described the experimental data with an error of less than 10% was developed. (C) 2000 Elsevier Science Ltd. All rights reserved.