Effects of Plasma Modification and Atmosphere on the Catalytic Hydrothermal Liquefaction of Chlorella

Abstract

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.

Effects of temperature, reaction time, atmosphere, and catalyst on hydrothermal liquefaction of Chlorella

“…Zeolite catalysts are known to promote the hydrocracking of larger molecules into smaller, more volatile molecules and can increase bio-oil yields under adequate conditions. [1] Effect of temperature As shown in Section 3.1.1 and our previous study, [18] temperature is one of the major factors that influence the HTL of microalgae. Temperature changes the dielectric constant of water during HTL, which affects the yield and quality of bio-oils.…”

“…The HTL method is described in our previous publication [ 18 ] Figure 1 outlines the experimental procedure for the separation of the HTL products.…”

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Hydrothermal liquefaction (HTL) is the direct conversion of wet biomass into bio-oil at high temperature (200-400 C) and high pressure (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). In this work, we investigated HTL with 4.5 g of Chlorella and 45 ml of water/ ethanol (1:1 vol.

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“…The current focus of this study is directed to the conversion of biomass via hydrothermal liquefaction (HTL) due to its ability to deal with whole biomass or processing wastes without drying, which is energy intensive. In the HTL process, high temperature (200-400 C) and high pressure (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) are applied to convert wet biomass into bio-crude oil, gas, aqueous phase, and solid residue. HTL has many advantages, namely, (i) drying of the bio-mass is no longer needed [3] ; (ii) the components of bio-mass, namely, lipids, proteins, and carbohydrates all undergo hydrolysis and decomposition [4] ; (iii) water possesses high dielectric constant, high ionic product, and low viscosity in the reaction system [5] ; (iv) the organic solvents, especially ethanol, can be used with water because ethanol have the ability to react with acidic components in the bio-oil and a lower dielectric constant, allowing better dissolution of high-molecular weight products derived from biomass [6] ; and (v) the nutrients (e.g., N, P, Mg, and K) can easily be separated and recycled for microalgae cultivation.…”

Utilization of reeds to sequester Ni and/or Cu from wastewater and to produce valuable products

“…The detailed HTC and product separation procedures are described in the previous publication (Haque et al 2022). Brie y, the HTC process was carried out using a 30ml High Temperature High Pressure (HTHP) batch reactor from Parr Instrument Company (Series 4590 Micro Stirred Reactor ≤ 5000psi, ≤ 500°C).…”