Steam reforming of raw bio-oil in a fluidized bed reactor with prior separation of pyrolytic lignin

Abstract

The effect operating conditions (temperature, steam/carbon molar ratio and space-velocity) have on the steam reforming of raw bio-oil has been studied in a two-step reaction unit. In the first step (operated at 500 ºC), a carbonaceous solid (pyrolytic lignin) deposits by re-polymerization of certain bio-oil components, and the remaining volatiles are reformed in the second step (fluidized bed reactor) on a Ni/La2O3-αAl2O3 catalyst. Under suitable reforming conditions (700 ºC, S/C = 9, space-velocity = 8,000 h-1), the yields of H2 and CO were 95 % and 6 %, respectively. Catalyst deactivation was very low, whereby the H2 yield decreased by only 2 % over 100 min of reaction. By using dolomite as adsorbent in the reforming reactor, CO2 was effectively captured and the raw bio-oil was reformed at 600 °C without adding water (S/C = 1.1), thus avoiding its vaporization cost. The yields of H2 and CO were 80-82 % and 1 %, respectively, for a space-velocity (GC1HSV) of 7,000 h-1 and catalyst/dolomite ratio of 0.25, although a high yield of CH4 (7 %) was obtained due to the cracking capacity of the dolomite. The coke content on the catalyst was high (7.7 wt% in 2 h) because of the limited gasification of coke precursors under the operating conditions (low temperature and low S/C ratio) used in the process with CO2 capture.