Abstract
To obtain drop-in fuel properties from 3rd generation biomass, we herein report the catalytic hydrotreatment of microalgae biocrude, produced from hydrothermal liquefaction (HTL) of Spirulina. Our contribution focuses on the effect of temperature, initial H2 pressure, and residence time on the removal of heteroatoms (O and N) in a batch hydrotreating setup. In contrast to common experimental protocols for hydrotreating at batch scale, we devised a set of two-level factorial experiments and studied the most influential parameters affecting the removal of heteroatoms. It was found that up to 350 °C, the degree of deoxygenation (de-O) is mainly driven by temperature, whereas the degree of denitrogenation (de-N) also relies on initial H2 pressure and temperature-pressure interaction. Based on this, complete deoxygenation was obtained at mild operating conditions (350 °C), reaching a concurrent 47% denitrogenation. Moreover, three optimized experiments are reported with 100% removal of oxygen. In addition, the analysis by GC-MS and Sim-Dis gives insight to the fuel quality. The distribution of heteroatom N in lower (<340 °C) and higher (>340 °C) fractional cuts is studied by a fractional distillation unit following ASTM D-1160. Final results show that 63–68% of nitrogen is concentrated in higher fractional cuts.
Highlights
Unprecedented climate shift and brisk depletion of conventional resources have raised socioeconomic and environmental concerns; the pursuit of clean, independent and alternative renewable and sustainable commercialized solutions for fuels has been expedited [1]
The distribution of heteroatom N in lower (340 ◦ C) fractional cuts is studied by a fractional distillation unit following ASTM D-1160
The yields of the small fractional distillation unit are stated in Table 7. 2.76 g and 1.09 g of sample is used for the fractional distillation of experiments 8 and 9, respectively
Summary
Unprecedented climate shift and brisk depletion of conventional resources have raised socioeconomic and environmental concerns; the pursuit of clean, independent and alternative renewable and sustainable commercialized solutions for fuels has been expedited [1]. Out of all available energy valorization techniques at our disposal, hydrothermal liquefaction (HTL) is considered as one of the most promising technologies for the production of biocrude oil, due to its advantages in rapid reaction, using all types of wet or dry feedstocks with no lipid-content restriction [10,11,12]. Recent techno-economic analyses and life cycle assessments on the conversion of microalgae into liquid fuels show that HTL has lower GHG emissions and higher economic potential, with a better energy return on investment as compared to conventional lipid extraction and transesterification technologies [13,14,15,16]
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