Ni dopped MgAl hydrotalcite catalyzed hydrothermal liquefaction of microalgae for low N, O bio-oil production. (1st February 2023)

• Record Type: Journal Article
• Authors: Lu, Tao; Sun, Yabo; Shi, Menghan; Ding, Dan; Ma, Zhiwen; Pan, Yali; Yuan, Yupeng; Liao, Wenchao; Sun, Yingqiang
• Is Part Of: Fuel. Volume 333(2023)Part 1
• Publication Date: 2023-02-01
• Subjects: Hydrothermal liquefaction -- Microalgae -- Low N -- O bio-oil -- MgAl-LDH; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2022.126437
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: Ni x Mg2 Al-LDHs with tunable acidic/basic and reducing properties are synthesized. Ni0.9 Mg2 Al-LDH is more favorable for biofuel production with maximum yield of 31.4%. Reducing property of Ni x Mg2 Al-LDH is increased with present of Ni 2+ . Final 13.49%, 9.09% decreases of O/C, N/C are observed at Ni ratio of 1.1, 0.9, respectively. Abstract: Catalytic hydrothermal deoxygenation and denitrogenation of microalgae for bio-oil production can potentially avoid energy-intensive upgrading of bio-oil, while tandem amidation of deoxygenation products and re-esterification of NH3 with free fatty acids make simultaneous removal of N, O a dilemma to achieve. Taking advances of Ni in catalytic hydrogenation of biofuel, Ni dopped MgAl layered double hydroxides (Ni x Mg2 Al-LDHs, x = 0, 0.5, 0.7, 0.9, 1.1) with tunable acidic/basic property are synthesized to simultaneously catalyze deoxygenation and denitrogenation for low N, O biofuel production. The results indicate that Ni doping is favorable to hydrothermal liquefaction (HTL) of microalgae with maximum yield of 31.4 wt% obtained via Ni0.9 Mg2 Al-LDH catalyzed HTL of microalgae at temperature of 300 ℃, time of 1 h, and catalyst loading of 5 wt%. Ni doping initially reduces basicity of Ni x Mg2 Al-LDH, subsequently leading to increase of O/C ratio of bio-oil, while a continuous increase of Ni 2+ provides more active species for deoxygenation with a final 13.49 % decrease of O/C ratio. Simultaneously, Ni doping of Ni x Mg2 Al-LDHs weakens denitrogenation of amino acids. However, tandem reactions of NH3 with reducing sugars, deoxygenation fatty acids radicals, and free fatty acids through Maillard reaction, amidation, and re-esterification are initially enhanced, leading to increase N/C ratio of bio-oil. Nevertheless, reducing property of Ni x Mg2 Al-LDH is continuously enhanced with increase of (Ni + Mg)/Al ratio from 0 to 2.9, finally resulting in 9.09 % decrease of N/C of biocrude. This work reports a methodology for simultaneous removal of N, O from biocrude, possibly providing a strategy for low N, O bio-oil production without further hydrogenation.