The development of third-generation biofuels from microalgae has been extensively researched over the last few years. Hydrothermal liquefaction (HTL) is a promising route for producing bio-oils from wet algae. The major drawback in HTL is the high temperature and high pressure that result in the high capital cost of the process. To make HTL an economical process for bio-oil production, the temperature and pressure should be reduced, which can be achieved by adding alcohol to water for HTL. The efficiency of the HTL process can also be improved by using a suitable heterogeneous catalyst with additional modifications. In this work, we investigated the effect of dielectric barrier discharge (DBD) plasma (argon and hydrogen plasma) modified zeolite Y as catalysts on the yield and quality of bio-oils produced in a hydrogen atmosphere versus air at different reaction times (0 and 15 min) and temperatures (240 and 250 °C). The mixture of solvents (50 vol % water and 50 vol % ethanol) was used in HTL to increase the yield and quality of bio-oils. Two sequential extractions were used to extract bio-oils from HTL products using dichloromethane. Different analytical techniques, such as thermal gravimetric analysis, elemental analysis, and gas chromatography−mass spectrometry, were used to understand the physicochemical properties of the bio-oils and for the determination of the higher heating value (HHV). The introduction of DBD plasma to modify zeolite Y improved the bio-oil quality and yield from HTL processes. The H 2 plasma modified catalyst enhanced the bio-oil yield at 240 °C from 46.83 ± 1.48% (240-0-H 2 -ZY) to 50.04 ± 0.88% (240-0-H 2 -ZY-HP) and from 50.24 ± 1.96% (250-0-H 2 -ZY) to 53.01 ± 0.73% (250-0-H 2 -ZY-HP) at 250 °C. The argon plasma modified catalyst reduced N-containing compounds from 29.42% (240-0-H 2 -ZY) to 2.94% (240-0-H 2 -ZY-AP) and decreased O-containing compounds from 4.02% (240-0-H 2 -ZY) to 1.38% (240-0-H 2 -ZY-AP) at 240 °C.

Hydrothermal liquefaction (HTL) is the direct conversion of wet biomass into bio‐oil at high temperature (200–400°C) and high pressure (10–25 MPa). In this work, we investigated HTL with 4.5 g of Chlorella and 45 ml of water/ethanol (1:1 vol. ratio) in a 100 ml reactor. Bio‐oils produced are characterized via elemental analysis, thermogravimetric analysis, and gas chromatography–mass spectrometry (GC–MS). HTL of Chlorella was investigated at 240 and 250°C for 0 and 15 min under an air or H2 atmosphere and with and without 5% zeolite Y. Temperature increased the bio‐oil yield from 38.75% at 240°C to 43.04% at 250°C for 15 min reaction time. Longer reaction time increased the bio‐oil yield at 250°C from 39.14% for 0 min to 43.04% for 15 min. The H2 atmosphere had a significant effect for HTL at 240°C. Zeolite Y increased the bio‐oil yield significantly from 32.03% to 43.06% at 250°C for 0 min. The carbon content of bio‐oil increased with the temperature while the oxygen content decreased. The boiling point distribution of bio‐oils in the range of 110–300°C varies with temperature, and atmosphere. At 240°C for 15 min, the 110–300°C range increased from 31.19% in air (240‐15‐air) to 39.25% in H2 (240‐15‐H2). The H2 atmosphere increased the content of hydrocarbons, alcohols, and esters from 69.61% in air (240‐0‐air) to 82.83% in H2 (240‐0‐H2). Overall, temperature, reaction time, atmosphere, and catalyst all significantly influenced the yield and/or quality of bio‐oils from HTL of Chlorella.

No abstract