Optimization Study on Microwave-Assisted Hydrothermal Liquefaction of Malaysian Macroalgae Chaetomorpha sp. for Phenolic-Rich Bio-Oil Production

Abstract

There are several methods of biomass conversion, including hydrothermal liquefaction (HTL). The implementation of microwave technology in the HTL process is still new, especially on the conversion of marine biomass into bio-crude. In this work, the macroalgae Chaetomorpha sp. was used as the biomass feedstock to produce phenolic-rich bio-oil through microwave-assisted HTL. Chaetomorpha sp. was abundantly found in Malaysia, creating a green tides issue. By utilizing these algae, the green tide issue can be solved and value-added bio-oil is obtained. However, bio-oil from macroalgae has a relatively low heating value, restricting its fuel application. Therefore, it is suggested to be used for bio-polymer synthesis, including bio-based phenol formaldehyde. In this study, the effect of different parameters, such as reaction temperature, preloaded pressure, water-to-algal biomass ratio, and holding time, on both the bio-oil yield and phenolic yield was evaluated. Folin–Ciocalteu method was introduced as the phenolic determination method and the optimal conditions were located by using Response Surface Methodology (RSM). As a results, an optimal biodiesel yield and phenolic yield of 21.47 wt% and 19.22 wt% Gallic Acid Equivalent was obtained at a reaction temperature of 226 °C, 42 bar preloaded pressure and 30:1 water-to-algal biomass ratio after 79 min. Sensitivity analysis also concluded that the water-to-algal biomass ratio is the most influential factor, followed by the preloaded pressure. The FTIR spectrum of the bio-oil produced indicated the presence of different functional group of compounds. In short, Chaetomorpha sp. has been successfully converted into valuable bio-oil through microwave-assisted HTL.

Hydrothermal Treatment of Biomass Feedstocks for Sustainable Production of Chemicals, Fuels, and Materials: Progress and Perspectives

“…to biocrude. 523 The maximum biodiesel yield of 21.47 wt % and phenolic yield of 19.22 wt % was obtained at optimum operation conditions of 226 °C, 76 min, water-to-biomass ratio of 30:1, and with pressure of 42 bar. The sensitivity analysis showed that HTL process is mostly impacted by the water-tobiomass ratio because water is the main microwave absorber.…”

“…A recent study optimized microwave-assisted HTL (MW-HTL) process conditions (temperature 200–260 °C, holding time 30–90 min, water-to-microalgae biomass ratio 10–30, preloaded pressure 25–45 bar) to improve the yield for the conversion of marine microalgae ( Chaetomorpha sp.) to biocrude . The maximum biodiesel yield of 21.47 wt % and phenolic yield of 19.22 wt % was obtained at optimum operation conditions of 226 °C, 76 min, water-to-biomass ratio of 30:1, and with pressure of 42 bar.…”

“…The liquefaction product of bagasse lignin can be used to replace (up to 20%) synthetic phenol in the production of resin adhesives. MW-HTL reaction using macroalgae Chaetomorpha sp., MW-HTL reaction at 226 °C yielded 21.47 wt % biodesel and 19.22 wt % phenol . The authors reported that the heating value of bio-oil from macroalgae was relatively low, limiting its potential application as a fuel.…”

“…The sensitivity analysis showed that HTL process is mostly impacted by the water-tobiomass ratio because water is the main microwave absorber. 523 Lorente et al studied the MW-HTL of brewers' spent grains at different temperatures (180−250 °C), pressures (50−130 bar), reaction times (0−2 h), and catalyst doses (Ni−Co/Al-Mg, dose: 0−0.25 g catalyst/g biomass). 524 The researchers found that the operation of the reactor at a temperature of 250 °C with a pressure of 125 bar for the residence time of 7 h without adding a catalyst resulted in the optimum production of various biofuels, i.e., 8% biooil, 35% solid char, and 31% saccharide-rich solution.…”

“…MW-HTL reaction using macroalgae Chaetomorpha sp., MW-HTL reaction at 226 °C yielded 21.47 wt % biodesel and 19.22 wt % phenol. 523 The authors reported that the heating value of bio-oil from macroalgae was relatively low, limiting its potential application as a fuel. However, the phenolic-based biooil can be used for the synthesis of biopolymer (e.g., phenol formaldehyde).…”