We subjected a set of model compounds (cornstarch and cellulose as model polysaccharides, soy protein and albumin as model proteins, sunflower oil and castor oil as model lipids) to the processing conditions and product recovery protocol commonly used for hydrothermal liquefaction (HTL) of algal biomass to make crude bio-oil. The model compounds were treated individually and in mixtures at 300 and 350 °C for batch holding time ranging from 10 min to 90 min. The model lipids produced the highest yield (>90 wt%) of biocrude (operationally defined as material soluble in dichloromethane), followed by the model proteins (∼30-35 wt%) and then the model polysaccharides (∼10-15 wt%). The production of biocrude at 350 °C occurred fully within the first 10 min of treatment, and the biocrude yield changed very little at longer times. Liquefaction at 350 °C and 60 min nearly doubled the biocrude yields from polysaccharides, relative to those obtained at 300 °C and 20 min. Otherwise, the yields from the different model compounds at the milder and the more-severe conditions were comparable. In most instances, the biocrude yield from hydrothermal treatment of mixtures was very similar to the mass-averaged yield calculated from the individual compound results. The chief exceptions were binary combinations of polysaccharide and protein under the more-severe conditions. For these mixtures, the biocrude yield exceeded the mass-average yield calculated from the pure compound results, thereby providing evidence that interactions influencing the biocrude yield can occur during hydrothermal treatment of mixtures of the biomolecules. Even so, a quantitative model built on the assumption that the lipids, polysaccharides, and proteins react independently during HTL predicted biocrude yields for ternary mixtures more accurately than did a model with three additional parameters that allowed for the possibility of interactions between the different model compounds.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology