• Energy Research

Abstract Hydrothermal liquefaction (HTL) is a promising technique of producing crude bio-oil (biocrude) from wet biomass. This work conducted the co-HTLs of microalgae (chlorella) and sewage sludge (SS) at 340 °C, 18 MPa, 0.3 MPa of initial H2 addition, 30 min of residence time under different feedstock mass ratios conditions, and explored the effects of three kinds of SS ashes on biocrude properties during microalgae HTL for the first time. Corresponding biocrude yields, elemental compositions, higher heating values, energy recoveries, boiling point distributions, and compound compositions were examined systematically. The results show that there was a certain synergistic effect on the improvement of biocrude yield other than biocrude quality in the co-HTL of microalgae and SS, especially at the 1:1 of mass ratio condition. This co-HTL could improve the actual biocrude yield by 4.7 wt% and decrease the actual solids yield by 3.6 wt% in contrast to corresponding theoretical yields. The pyrolysis-state SS ash could reduce the N and O contents, increase the C and H contents and HHV, and improve the proportion of low-boiling-point (

This article focuses on the kinetic modeling and catalytic performance of hydrodenitrogenation of pyridine under hydrothermal conditions. Piperidine derivatives are the major nitrogen-containing in...

Abstract The hydrothermal liquefaction (HTL) of microalgae produces water-soluble biocrude (WSB) and water-insoluble biocrude (WISB) simultaneously. The effects of heterogeneous catalysts (i.e. Pt/C, Ru/C, and Pt/C + Ru/C) on the properties of the two types of biocrudes derived from Chlorella HTL were explored for the first time. The results show that the addition of catalyst (Pt/C, Ru/C, or Pt/C + Ru/C) and/or the increase of residence time (from 10 to 30 min) could decrease the WSB fraction in total biocrude (WSB + WISB) mainly due to the improvement of the WISB yield. The catalytic effects on the WISB yield primarily occurred at the low algae loading (i.e., 1:10 of algae/water) condition, and there was a certain synergetic catalytic effect between Pt/C and Ru/C at this condition. The catalytic effect of Pt/C on the yields of WISB and total biocrude reduced as residence time increased. At the HTL conditions of 350 °C, 0.3 MPa H2, and 1:5 of algae/water for 30 min, Pt/C and Ru/C separately led to WSB and WISB with the highest C (63.57 and 74.16 wt%), H (7.34 and 8.44 wt%) contents and the lowest N (12.19 and 7.06 wt%), O (14.06 and 9.15 wt%) contents, and the highest HHVs (29.73 and 35.60 MJ/kg). The WISB produced with Pt/C mainly consisted of amides, hydrocarbons, organic acids and phenols. Pt/C could promote the cracking of high-molecular-weight compounds in WSB to form more low-boiling-point compounds.

Hydrothermal liquefaction of the third-generation biomass represented by microalgae can produce biocrude. However, the directly obtained biocrude has a high heteroatom content and a low higher heating value (HHV), which cannot meet the standards of biofuel. In this work, water-insoluble biocrude which was directly gained from microalgae hydrothermal liquefaction (HTL) was upgraded under four kinds of solvents (i.e., methanol, ethanol, acetone, and H₂O) and one type of catalyst (H₂O + Ru/C) at 240–400 °C for 1 h. The results show that the HHV and C and H contents of upgraded bio-oil increased and the O/C ratio decreased significantly after solvent upgrading. The highest upgraded bio-oil yield appeared in the case of ethanol upgrading and reached the maximum value of 82.8 wt % at 360 °C. The upgraded bio-oil yield of acetone upgrading increased from 45.8 to 68.2 wt % as the temperature increased within 240–400 °C. Also, esterification reactions between alcohol and acid in the supercritical system remarkably reduced the content of carboxyl-containing organic matter.

This article systematically describes chemical reactions in biomass HTL and the catalytic hydrogenation upgrading of the obtained biocrude and analyze the effects of operating parameters on these two processes, such as reaction temperature, residence time and catalyst type.