Catalytic hydrothermal liquefaction of soy protein concentrate

We report herein on the hydrothermal catalytic liquefaction of soy protein concentrate. Catalyst screening experiments have shown that metal catalysts (e.g., 5 wt % Pt, Pd, or Ru) supported on porous solids (e.g., carbon, Al₂O₃) produce crude bio-oils with less heteroatom content than does noncatalytic liquefaction of this material under otherwise identical conditions. The catalysts had little influence on the biocrude yield. Of the different catalytic materials tested, Ru/C had the greatest influence on the biocrude composition. The heating value of the biocrude produced from liquefaction at 350 °C for 120 min with a 20 wt % loading of Ru/C was 16% higher than the heating value from the noncatalytic run (37 MJ/kg vs 43 MJ/kg). Moreover, the heteroatom content of this biocrude from catalytic liquefaction was less than half that of its noncatalytic counterpart (16.6 wt % vs 7.8 wt %). The catalyst reduced sulfur levels in the biocrude to below detection limits and the nitrogen level to 45% of that in the noncatalytic product. Additional experiments with the Ru/C catalyst showed only modest improvements in biocrude quality with increasing catalyst loading or liquefaction temperature or time. The presence of the Ru/C catalyst shifted the distribution of products amenable to gas chromatography (GC) analysis from being primarily heterocyclic nitrogen-containing compounds and fatty acid amides to being primarily single-ring aromatic hydrocarbons and phenolics. Taken collectively, these results show that heterogeneous catalysts can be effective during hydrothermal liquefaction of material rich in protein.