Effect of H-Bonding on Brønsted Acid Ionic Liquids Catalyzed In Situ Transesterification of Wet Algae

Abstract

Brønsted acid ionic liquids (BAILs) are effective to biodiesel production of in situ transesterification of wet algae due to their dual role as both solvents of cellulose and catalysts of transesterification. The cellulose solubilities of BAILs are depending on H-bonding of BAILs-cellulose in varied solvent conditions, which subsequently affect the biodiesel productions. For this reason, the effects of H-bonding between BAILs includingand cellulose under different methanol and water conditions on cellulose extractions are experimentally and theoretically investigated. The cellulose extractions in BAILs are decreasing as [Bmim][H 2 PO 4 ] > [Bmim] 2 [HPO 4 ] > [Bmim][HSO 4 ], contrary to the variation of their thermal stabilities and crystallinities caused by varied Hbonding of BAILs-cellulose. Increasing methanol is positive to cellulose extractions in [Bmim][HSO 4 ], while negative to those in [Bmim][H 2 PO 4 ] and [Bmim] 2 [HPO 4 ], due to the solvent effect of methanol confirmed by cyclic voltammetry (CV) measurements. The effect of water on H-bonding of BAILs-cellobiose is contrary to the effect of methanol. It is confirmed via the bonding interaction of BAILs-cellobiose through the density functional theory (DFT) computational method. However, the biodiesel yields are varied differently due to the competition of H-bonding of BAILs-cellobiose and deprotonation of BAILs under different methanol and water conditions. This study might pave the way to neutralize the negative effect of water on in situ transesterification via enhancing the cellulose extractions of BAILs.

Keggin‐type Heteropolyacids‐Catalyzed Selective Hydrothermal Oxidation of Microalgae for Low Nitrogen Biofuel Production

“…[8] Among vast biomass resources for bio-oil production, microalgae are recognized as the most promising biofuel feedstocks because of their high photosynthetic efficiency, fast growth rate and high lipid content properties. [9][10][11] During the HTL of microalgae, their cellular compounds including lipids, proteins, and carbohydrates are converted into bio-oil, water soluble nutrients, gases, and residues, through hydrolysis of cellular compositions into monomers, deamination, decarboxylation and dehydration of the monomers, and the following tandem reaction including cyclization, condensation and repolymerization of the fragments. [12,13] Besides the valuable bio-oil products, the inorganic nutrients of microalgae are transformed into water soluble nutrients during HTL process, which can be recycled for algae growth.…”

MgAl-LDH/LDO-Catalyzed Hydrothermal Deoxygenation of Microalgae for Low-Oxygen Biofuel Production

“…However, there is a slight decrease of the biocrude yields of MgAl-LDH 3 - and MgAl-LDO 3 -catalyzed HTL of microalgae when the reaction temperature is higher than 300 °C (Figure (a)). On the one hand, increasing temperature below 300 °C is favorable to biocrude production due to the enhanced hydrolysis of cellular compounds of microalgae and the following cleavage of the monomers including fatty acids, amino acids, and monosaccharide at higher reaction temperatures. , However, small molecules might undergoing secondary bond cleavage to produce lower molecular weight compounds including aqueous volatile organics and gas products when the temperature is higher than 300 °C, leading to a decrease of biocrude yield of MgAl-LDH 3 /LDO 3 -catalyzed HTL of microalgae . On the other hand, the biocrude yields decrease as MgAl-LDH 3 > MgAl-LDO 3 > control in the range of 200–330 °C (Figure (a)), indicating that both MgAl-LDH 3 and MgAl-LDO 3 with both acidic and basic properties are favorable to the hydrolysis of cellular compounds and following the cleavages of corresponding monomers.…”

“…The initial column temperature was held at 50 °C for 3 min and was then heated to 300 °C at a rate of 5 °C/min. The final temperature of the column was held at 300 °C for 10 min …”

“…Acid- or base-catalyzed HTLs of microalgae have been extensively studied to improve the yield and the properties of the resulting bio-oil. , Generally, homogeneous acids and alkalis, such as inorganic acid, organic acids, and water-soluble alkalis, are favorable to the thermochemical decomposition of lipids, carbohydrates, and proteins. − However, they are rarely utilized in large scale due to their corrosive nature and the difficulty of recycling. Accordingly, heterogeneous acid or base catalysts composed of transition metals, such as Ni, Pd, Pt, Ru, and Mo, and supporting materials, including carbon nanotubes, zeolites, and activated carbons, are extensively investigated for catalyzing the HTL of microalgae for biofuel production. − Nevertheless, the N and O contents in the proteins and carbohydrates of algal biomass of bio-oil are thermally transformed into N-containing and O-containing compounds, leading to the lower higher heating value (HHV) and quality of algal bio-oil. − Accordingly, catalytic hydrodeoxygenation (HDO), decarboxylation (DCO 2 ), and decarbonylation (DCO) of crude bio-oil via metal-based catalysts, such as CoMo/C, Ni/Al 2 O 3 , Ni/C, Mo 2 C/TiO 2 , and MoN/C, have been extensively utilized to tackle these undesirable properties of bio-oil. − However, these metal-based catalysts suffer from aggregation of the metal species, low catalytic performances, and high hydrogen pressure (7–20 MPa). , Further development of the effective catalyst for deoxygenation of the bio-oil remains a core challenge in the overall process from microalgae to biofuel.…”

“…8,9 Acid-or base-catalyzed HTLs of microalgae have been extensively studied to improve the yield and the properties of the resulting bio-oil. 10,11 Generally, homogeneous acids and alkalis, such as inorganic acid, organic acids, and water-soluble alkalis, are favorable to the thermochemical decomposition of lipids, carbohydrates, and proteins. 12−15 However, they are rarely utilized in large scale due to their corrosive nature and the difficulty of recycling.…”