Conversion of Biomass Derived Tar in a Catalytic Post-Gasification Process
Abstract
The present MESc thesis reports the performance of a fluidizable CeO2 promoted Ni/γ-Al2O3 catalyst to be used in a post-gasification process for tar removal. The catalysts developed were prepared using the incipient wetness technique and characterized chemically and physically, using the following techniques: N2 Adsorption-Desorption, XRD, NH3 and CO2 TPD, Pyridine-FTIR, H2-TPR, and H2-Pulse Chemisorption. The catalysts were tested in a fluidized CREC Riser Simulator, in the 500°C-550°C temperature range, within 5 s-10 s reaction times, using both steam and steam-H2/CO2 atmospheres.A 2-methoxy-4-methlyphenol (2M4MP) compound was used as a biomass derived tar surrogate.
The CeO2 promoter helped to reduce the strong and very strong acidity of the γ-Al2O3 support, without significantly affecting the specific surface area of the alumina support. However, the specific surface area of the precursor catalyst decreased moderately, with the increase of the Ni loading. Using the developed Ni-CeO2-/γ-Al2O3 catalyst, runs with the 2M4MP were conducted in the CREC Riser Simulator. These runs showed a high overall 2M4MP conversion, comparable to those of the thermal non-catalytic runs. There was, at the same time, a significant desirable reduction of the C1+ hydrocarbons product species selectivity, with a simultaneously high CO2/CO and H2/CO ratios. These two high ratios are indicators of a strong water-gas shift reaction influence, with H2/CO larger than 2 yielding a valuable syngas for methanol synthesis.