(63a) A Study for Kinetic Modeling and Experimental Validation of Lignin Fractionation with 4-Phenolsulfonic Acid for Effective Lignocellulosic Biomass Utilization

In terms of sustainability and renewability, biomass utilization has received significant research interest, instead of consuming only petrochemical products, to obtain alternative resources such as energy, aromatic chemicals, etc. [1] However, those biorefineries are still suffering from their low cost-competitiveness, compared to the existing petrorefineries, despite considerable research efforts on effective biomass utilization. To improve the competitiveness of biomass-derived products, it is necessary to maximize the use of major biomass components including cellulose and lignin via effective refinery strategies. Among the major biomass components, lignin is a crucial recalcitrance factor since it acts as either a physical barrier limiting cellulose accessibility to chemicals and/or enzymes, or an inhibitor reducing enzymes and microorganism activities, resulting in poor productivity of the end-products like biofuel [2]. Consequently, effective lignin removal is desired in most biomass utilization strategies. There have been a number of studies for biomass pretreatment/fractionation using acid, alkaline, organic solvent, or hot water [3]. However, these conventional methods had unwanted lignin degradation and modification due to their harsh reaction conditions. Therefore, recently fractionation processes have been developed to yield not only carbohydrates but also high-quality lignin [4].

In this sense, 4-phenolsulfonic acid (PSA) has been considered as an effective fractionation reagent [2]. The amphiphilic property of PSA makes effective lignin fractionation under mild conditions. In our previous study [3], the technical feasibility of PSA in biomass fractionation was conceptionally proven by experiments; however, the development of the systematic model and process optimization is still necessary for maximizing process efficiency. To achieve these objectives, our model was initially developed based on a series of experiments. That is, underlying kinetics of the reactions were firstly examined from the experimental data with different biomass dimensions and reaction temperatures using aspen wood chip as bulk biomass and PSA as a solvent. Afterward, the kinetic Monte Carlo (kMC) algorithm was combined with a governing equation, i.e., mass balance equation of major component (e.g., cellulose, lignin), to model a sophisticated series of phenomena. By using the above-developed multiscale model, one can track not only macroscopic phenomena (e.g., mass/energy transfer) but also microscopic events (e.g., tracing porosity and cell wall thickness); therefore, the biomass properties can extensively be understood throughout the entire process period[5]. Especially, the model includes consideration for delignification and de/repolymerization processes of lignin fragments in the reacting solution to overcome underutilization of the lignin.

Literature cited:

[1] Kim K.H., & Kim C.S. (2018). Recent Efforts to Prevent Undesirable Reactions From Fractionation to Depolymerization of Lignin: Toward Maximizing the Value From Lignin. Front. Energy Res., 6, 92.

[2] Yoo C.G., Meng X., Pu Y., & Ragauskas A.J. (2020). The critical role of lignin in lignocellulosic biomass conversion and recent pretreatment strategies: A comprehensive review. Bioresour. Technol., 301, 122784.

[3] He D., Wang Y., Yoo C.G., Chen Q.-J., & Yang Q. (2020). The fractionation of woody biomass under mild conditions using bifunctional phenol-4-sulfonic acid as a catalyst and lignin solvent. Green Chem., 22, 5414-5422.

[4] Morais A.R.C., da Costa Lopes A.M., & Bogel-Łukasik R. (2015). Carbon Dioxide in Biomass Processing: Contributions to the Green Biorefinery Concept. Chem. Rev., 115, 3-27.

[5] Choi H.-K., & Kwon J.S.-I. (2019). Modeling and control of cell wall thickness in batch delignification. Comput. Chem. Eng. 128, 512-523.