Upgrading Algae Biocrude for a Low-Nitrogen-Containing Biofuel: Compositions, Intermediates, and Reaction Routes

Abstract

The upgrading of algae biocrude (obtained by hydrothermal liquefaction) was studied under mild conditions. Here we adopted a guard catalyst to protect the core catalyst and obtained algae biofuel with low heteroatom content at 350 °C. The nitrogen content of biofuel is 0.016 wt %, and the calculated oxygen content is less than 0.51 wt %. Furthermore, the effective yield from biocrude to a low-heteroatom-containing biofuel was close to the theoretical yield. Through a detailed study of the upgrading process, the content variation trend of biocrude and biofuel compositions and their potential reaction pathways were revealed. The results indicated that hydrogenation reactions almost finished after upgrading at 350 °C for 15–30 min.

Catalytic upgrading of hydrothermal liquefaction biocrudes: Different challenges for different feedstocks

“…Indole conversion was also observed in the reported set of experiments. Based also on literature [15], possible reaction products can be represented by ethylbenzene and ethylcyclohexane ( Figure 5), which were both detected among the reaction products. other studies [21,22], where different settings of the instruments were able to detect also other fatty acids up to C20.…”

“…Other studies in the literature were conducted with different catalysts and operating conditions, such as: ZSM-5 zeolites [10], sulfided NiMo and CoMo on Al2O3 support [11], Pt/Al2O3 and HZSM-5 [12] and several other supported metallic catalysts [13]. Two-stage upgrading has been investigated as well [14,15]. A few hydrotreating studies are also available for wood biocrude.…”

The influence of lipids on the fate of nitrogen during hydrothermal liquefaction of protein-containing biomass

“…This suggests that only adjusting the condition parameters and adding catalysts is not enough to achieve complete N removal. Despite the existence of bio-oil upgrading treatments such as hydrotreating [12] and distillation [13], which could reduce the N content in the bio-oil, these are extremely cost-intensive processes, especially the former, due to their employment of H 2 . Moreover, bio-oil obtained from HTL can contain water, which is difficult to remove during solvent extraction, being one of the mentioned causes for deactivation of upgrading sulfide catalysts [8,14,15].…”

Two-stage catalytic hydrotreatment of highly nitrogenous biocrude from continuous hydrothermal liquefaction: A rational design of the stabilization stage

“…However, a number of studies have been performed on the hydrotreatment of HTL biocrude from algae in the presence of different catalysts [22][23][24][25], where the focus was on achieving a high degree of heteroatoms removal. Zhao et al [26,27] investigated the catalytic upgrading of algae biocrude in two-stage batch experiments, and reported almost complete removal of N (99.5%) in the presence of a commercial NiMo/γ-Al 2 O 3 catalyst. Cole et al [28] successfully carried out two-stage upgrading for macroalgae biocrude and reported it as the only viable way to effectively achieve drop-in fuels.…”