Pretreatment of fast pyrolysis bio-oil by slurry hydroprocessing

In this work, fast pyrolysis bio-oil (FPBO) has been hydroprocessed in a continuous pilot scale slurry process utilizing unsupported molybdenum sulfide catalyst with the aim of producing a partially upgraded oil product suitable for processing in conventional fixed bed hydrotreaters into final hydrocarbons. Screening of process parameters in the slurry-process revealed that changes in reaction pressure (70–140 bar) had minimal effect on the amount of H 2 consumed, while increases in temperature (350–390 °C) or catalyst loading (0.25–0.5 wt% Mo) resulted in increased H 2 -consumption. A higher level of H 2 -consumption was, in turn, strongly linked to improved properties, but reduced yield, of the oil product. Recirculation of used slurry catalyst back to the process was also demonstrated in continuous operation of the pilot plant for over 60 h and ten reactor passes of the catalyst. Although an initial decrease in the catalytic activity was observed, the catalyst quickly attained a stable and still relatively high performance. The results show that, using the slurry-process, it is possible to obtain a partially upgraded FPBO with significantly improved properties, such as low coke formation tendencies and minimal levels of inorganics.