(688e) Process Modeling and Optimization of a Bio-Adhesive Production Process Using Kraft Lignin and Soy Protein Isolate

Due to the gradual depletion of fossil fuel sources along with the issues of greenhouse gas emission and resulting environmental impact, interest in the development and application of sustainable and eco-friendly alternatives has rapidly increased over the last few decades. The global wood-panel industry heavily depends on the petroleum-derived commercial adhesives[1], [2] like phenol–formaldehyde (PF), urea–formaldehyde (UF), melamine–formaldehyde (MF) and melamine–urea–formaldehyde (MUF). These formaldehyde-based chemicals cause hazards to both human health and environment through emission of toxic volatile organic compounds[3], [4] such as phenol, formaldehyde etc. Hence, this work focuses on manufacturing bio-adhesive using renewable materials such as lignin and soy protein. Soy protein adhesive can become a potential formaldehyde-free substitute for adhesion industries due to the advantages of being bio-degradable, having low-cost and having high production possibilities[4], [5]. However, soy protein as an adhesive may suffer from various limitations, such as low water–resistance, poor mechanical properties, and relatively low bonding strength. On the other hand, lignin, one of the main constituents of lignocellulosic biomass, is considered to be another potential raw material for bio-adhesive due to the presence of both alcohol- and phenol-type hydroxyl groups in its complex molecular structure[6]. Crosslinking soy protein with lignin has proved to be an effective way to overcome the disadvantages associated with soy protein adhesive.

In this work, kraft lignin (KL) and soy protein isolate (SPI) are used as the feedstock for the bio-adhesive manufacture process. Each year, more than 50 Mt KL is produced as a waste in the paper and pulp industry, and almost 98% of it is burned as a fuel causing high emission of greenhouse gases[7], [8]. Production of the bio-adhesive consists of two steps. In the first step, the KL is depolymerized to smaller oligomer units. These oligomer fragments are added to the SPI in the second step to produce the lignin-soy protein isolate-based bio-adhesive.

In this work, a kinetic model is developed for converting lignin to oligomers by using a thermochemical method, namely hydrothermal base catalyzed depolymerization (BCD). Optimal kinetic parameters are estimated by utilizing the literature and in-house data. Then a model is developed for the bio-adhesive production step using literature data and available in-house information. The lab-scale reactor models are scaled to the commercial-scale. Models of additional balance of plant are developed with due considerations of mass and heat integration and recycling of catalysts. An economic model of the process is developed, and a mathematical optimization problem is set up to optimize the design parameters and operating conditions of the reactors for maximizing the net present value.

References:

[1] M. Podlena, M. Böhm, D. Saloni, G. Velarde, and C. Salas, “Tuning the adhesive properties of soy protein wood adhesives with different coadjutant polymers, nanocellulose and lignin,” Polymers (Basel)., vol. 13, no. 12, pp. 1–16, 2021, doi: 10.3390/polym13121972.

[2] A. Arias et al., “Recent developments in bio-based adhesives from renewable natural resources,” J. Clean. Prod., vol. 314, no. May, 2021, doi: 10.1016/j.jclepro.2021.127892.

[3] D. Gonçalves, J. M. Bordado, A. C. Marques, and R. G. Dos Santos, “Non-formaldehyde, bio-based adhesives for use in wood-based panel manufacturing industry—a review,” Polymers (Basel)., vol. 13, no. 23, 2021, doi: 10.3390/polym13234086.

[4] M. Bai et al., “A novel universal strategy for fabricating soybean protein adhesive with excellent adhesion and anti-mildew performances,” Chem. Eng. J., vol. 452, no. P3, p. 139359, 2023, doi: 10.1016/j.cej.2022.139359.

[5] C. Xu et al., “Soy protein adhesive with bio-based epoxidized daidzein for high strength and mildew resistance,” Chem. Eng. J., vol. 390, no. February, p. 124622, 2020, doi: 10.1016/j.cej.2020.124622.

[6] C. Jiang, J. Hu, C. Zhang, G. Hota, J. Wang, and N. G. Akhmedov, “Lignin oligomers from mild base-catalyzed depolymerization for potential application in aqueous soy adhesive as phenolic blends,” React. Chem. Eng., vol. 8, no. 10, pp. 2455–2465, 2023, doi: 10.1039/d3re00224a.

[7] A. Agarwal, M. Rana, and J. H. Park, “Advancement in technologies for the depolymerization of lignin,” Fuel Process. Technol., vol. 181, no. September 2018, pp. 115–132, 2018, doi: 10.1016/j.fuproc.2018.09.017.

[8] J. J. Bernhardt, B. Rößiger, T. Hahn, and D. Pufky-Heinrich, “Kinetic modeling of the continuous hydrothermal base catalyzed depolymerization of pine wood based kraft lignin in pilot scale,” Ind. Crops Prod., vol. 159, no. July 2020, 2021, doi: 10.1016/j.indcrop.2020.113119.