Hydrothermal liquefaction of fresh lemon-peel and Spirulina platensis blending -operation parameter and biocrude chemistry investigation

Abstract

The present study investigated the biocrude production from the blending of Spirulina platensis and lemon-peel via hydrothermal liquefaction process. The interaction of parameters such as temperature (280–350 °C), time (10–60 min), and different blending ratio on liquefaction was visualized using the response surface methodology. During the experiment, the highest biocrude yield of 26 wt% was achieved at 336 °C and 35 min with the Spirulina platensis/lemon-peel mass ratio of 4:1. Results showed that the biocrude yield was increased with microalgae content in the blending, whereas the effect of temperature and time was dependent on the other parameters. The blending led to a reduction in the yield, energy recovery, and also the nitrogen content of the biocrude compared with the model estimation. GC-MS, FT-IR, NMR, and TGA were applied to characterize the biocrude. Results demonstrated an increase of nitrogen heterocycles and a decline of unsaturated compounds due to liquefaction of the blending. The blending resulted in a shift of compounds in biocrude from low to middle distillation region. The ultimate analysis indicated a strong deoxygenation degree of biomass during hydrothermal liquefaction process, while the blending displayed an inconspicuous improvement in the deoxygenation.