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Preliminary Optimization and Kinetics of SnCl2-HCl Catalyzed Hydrothermal Conversion of Microcrystalline Cellulose to Levulinic Acid

Dexby de Guzman, Rizalinda de Leon*

Fuels, Energy and Thermal Systems Laboratory, Department of Chemical Engineering, University of the Philippines, Quezon City, 1101, Philippines

* Corresponding Author: Rizalinda de Leon. Email:

(This article belongs to this Special Issue: Renewable materials for sustainable development)

Journal of Renewable Materials 2021, 9(1), 145-162. https://doi.org/10.32604/jrm.2021.011646

Abstract

Levulinic acid (LA) is a platform biorefinery chemical from biomass which can be converted to green solvents, plasticizers, polymer precursors, bio-based cleaning agents, fuels and fuel additives. This study assessed the potential of SnCl2-based mixed acid systems as catalyst in the hydrothermal conversion of microcrystalline cellulose to levulinic acid. Maximum LA yield of 36.2 mol% was achieved using 0.2 M SnCl2 concentration at test conditions of 3 h, 180°C and 1% w/v cellulose loading. To reduce precipitate formation and further improve LA yield, the strategy employed was to combine SnCl2 (a Lewis acid) with conventional mineral acids (Bronsted acids). Evaluation of the catalytic performance of SnCl2-HCl, SnCl2-H2SO4, SnCl2-HNO3, and SnCl2-H3PO4 (1:1 molar ratio, 0.2 M total acid concentration) were done with highest LA yield of 47.0 mol% obtained using the SnCl2-HCl system at same test conditions. Response surface methodology optimization employing Box-Behnken design generated a quadratic model with a high coefficient of determination (r2) of 0.964. A maximum LA yield of 63.5 mol% can be achieved at 0.17 M catalyst concentration, 198°C, and 5.15 h reaction time. Rate constants were estimated using nonlinear regression, while activation energies were determined using Arrhenius equation. Cellulose hydrolysis was determined to be the rate-limiting step in the overall process. Low activation energy of 63.3 kJ/mol for glucose dehydration to hydroxymethylfurfural supports the action of SnCl2 as Lewis acid in the mixed-acid system. LA yield simulations for plug flow reactor (PFR) and continuous stirred tank reactor (CSTR) were done suggesting a similar PFR-CSTR configuration with the established Biofine process. Lastly, a reaction scheme was presented to explain the synergy between SnCl2 and HCl in LA production from cellulose.

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Cite This Article

Guzman, D. D., Leon, R. D. (2021). Preliminary Optimization and Kinetics of SnCl2-HCl Catalyzed Hydrothermal Conversion of Microcrystalline Cellulose to Levulinic Acid. Journal of Renewable Materials, 9(1), 145–162.

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This work is licensed under a Creative Commons Attribution 4.0 International License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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