Steam reforming of pyrolysis oil aqueous fraction obtained by one-step fractional condensation

• Steam reforming feedstock produced via fractional condensation of pyrolysis vapors.
• Aqueous fraction with high concentration of low molecular weight oxygenates.
• High H2 yields obtained at 650 °C without any additional steam (S/C = 3.84).

The aqueous fraction of pyrolysis oil, which was produced and fractionally condensed in VTT's 20 kg/h fast pyrolysis Process Development Unit, was successfully steam reformed in a fixed-bed reactor over a commercial nickel catalyst without any additional steam. As a result of the one-step fractionation process, the aqueous pyrolysis oil, which had a water content of 72.7 wt%, contained only limited amounts of thermally unstable sugar-type compounds that typically hinder the performance of catalytic steam reforming. An average hydrogen yield of 81% was achieved over two hours at relatively mild process conditions: 650 °C, steam-to-carbon ratio of 3.84 and gas hourly space velocity of 5000 h−1. When the reaction temperature was varied between 600 and 750 °C, clear catalyst deactivation was only observed at 600 °C. In theory, by utilizing the one-step fractional condensation scheme and subsequently steam reforming the aqueous pyrolysis oil, sufficient amounts of hydrogen could be generated for significantly deoxygenating the organic pyrolysis oil via catalytic hydrodeoxygenation.