Stabilization of fast pyrolysis liquids from biomass by catalytic hydrotreatment using Raney nickel type catalysts

The catalytic hydrotreatment of fast pyrolysis liquids (PL) from lignocellulosic biomass is a promising technology to improve the properties of PL. Mild hydrotreatment (< 250 degrees C) using a suitable catalyst allows the production of stabilized oils that have for instance potential for co-processing in existing oil refinery units. Here, we report a catalyst screening study to stabilize PL by a mild hydrotreatment using five Raney nickel type catalysts (Ra-Ni), more specifically a benchmark Ra-Ni, two types of Fe/Cr promoted, and two Mo-promoted ones. Experiments were performed at relatively mild hydrotreatment conditions (200 degrees C, initial 140 bar H-2 pressure, 4 h) in a batch autoclave. Among all the Ra-Ni catalysts, the Mo promoted (A-7063) showed the highest hydro-(deoxy)genation activity, a lower extent of repolymerization (GPC), and lower charring tendency of the product oil (TGA) compared to the promoter-free and Fe/Cr promoted Ra-Ni catalysts. Analyses of the product oils showed that the oils contain a significant amount of phenolics (7.4-15.4 wt% on oil, GC x GC-FID). These findings indicate that commercially available Raney nickel type catalysts, and particularly the Mo promoted ones, are attractive to be used for the mild hydrotreatment of pyrolysis liquids.

Automated summary

The study focused on catalytic hydrotreatment of fast pyrolysis liquids from lignocellulosic biomass using different types of Raney nickel catalysts, with Mo-promoted Ra-Ni catalyst showing the highest hydro-(deoxy)genation activity and lowest charring tendency of the product oil. The analyses of product oils revealed the presence of a significant amount of phenolics, indicating the potential of commercially available Raney nickel catalysts, particularly the Mo-promoted ones, for mild hydrotreatment of pyrolysis liquids.