The Upgrading of Bio-Oil from the Intermediate Pyrolysis of Waste Biomass Using Steel Slag as a Catalyst

Catalytic pyrolysis is a complex system where the selection of an efficient, cheap, abundant, and stable catalyst is vital to upgrade pyrolysis products to biofuels. Steel slag (SS) can be considered as an inexpensive catalyst, making it a very economical option. SS has a high content of calcium, iron, and magnesium, making this solid compound catalytically active. This study investigated the utilization of SS as a sacrificial catalyst in pyrolysis experiments using a thermocatalytic reforming (TCR) process to produce an upgraded bio-oil and syngas. In the first part of this work, SS was mixed with sugarcane bagasse (SB) and oat hulls (OH) biochar (in different trials) in the postreformer at different ratios (0, 30, 70, and 100 wt % of SS). In the second part, SS (powder) was pelletized directly with raw OH at different ratios (0, 10, 20, and 30 wt % of SS in the feed composition) and introduced into a pyrolysis reactor. The introduction of SS into SB in the reformer improved the higher heating value (HHV) from 29.1 MJ/kg (0 wt % of SS) to 35.5 MJ/kg (100 wt % of SS). Introducing 30 wt % of SS into OH in the feed showed a higher calorific value and lower acidity, viscosity, and density in comparison with using SS with different ratios in the reformer. The use of SS as a catalyst was found to significantly improve the quality and the properties of bio-oil and syngas, revealing an innovative pathway for its use as an inexpensive sacrificial catalyst for biofuel production via the TCR process.