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A Continuous Electrochemical Process to Convert Lignin to Low Molecular Weight Aromatic Compounds and Cogeneration of Hydrogen

Naderinasrabadi, Mahtab
http://orcid.org/0000-0003-0538-849X
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1584622583669502

Abstract Details

2020, Doctor of Philosophy (PhD), Ohio University, Chemical Engineering (Engineering and Technology).
Lignin is one of the main byproducts of pulp and paper industry and biorefineries. Depolymerization of lignin can lead to producing valuable low molecular weight compounds with different functional groups, which are mainly achieved from crude oil sources. Lignin electrolysis could address issues of other lignin depolymerization methods such as complexity, lignin combustion, and low selectivity. On the other hand, lignin electrolysis can occur at significantly lower overpotentials than those required for water electrolysis, which leads to lower-voltage electrolyzer operation and as a result lower energy consumption for hydrogen production. This study includes research and experimental works on developing a continuous electrochemical process for both lignin electrolysis and hydrogen production in an electrolyzer. At the first step of this project, high surface area TiO2 or carbon-supported NiCo electrocatalysts were synthesized and applied for lignin depolymerization at room temperature and pressure. The electrocatalysts were characterized by Brunauer-Emmett-Teller (BET), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDS) techniques. In addition, a three-electrode rotating disc electrode (RDE) system was used to test the performance and durability of 6 electrocatalysts individually and among them 1:3NiCo/TiO2 was selected as the most effective catalyst for lignin depolymerization. In the second step, a continuous electrochemical cell with 10 cm2 electrodes, separated by an anion exchange membrane (AEM), was applied for lignin electrolysis in the anode and hydrogen generation in the cathode. The effects of temperature, lignin concentration, cell voltage, and electrolysis time on hydrogen production, oxygen evolution, lignin conversion, products with different functional groups, and energy efficiency of the electrochemical reactor were investigated. Although applying high cell voltages increases the rate of electrochemical reactions and lignin conversion, it produces inefficiencies in energy consumption by enhancing oxygen evolution reaction (OER). Several techniques including gas chromatography-mass spectroscopy (GC/MS), ultraviolet-visible (UV-Vis) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), and Raman spectroscopy were applied to analyze the lignin samples. In addition, the generalized standard addition method (GSAM) for the first time was applied for measuring lignin conversion after electrolysis. The third step of this project included scaling-up the 10 cm2 continuous electrochemical cell to a 200 cm2 reactor and utilizing it for lignin electrolysis and H2 production on a larger scale. The results indicate that the performance of the scaled-up reactor is extremely analogous to the 10 cm2 cell.
John Staser (Advisor)
150 p.
Chemical Engineering; Chemistry; Engineering; Environmental Engineering; Wood Sciences
Lignin electrolysis; Hydrogen production; Oxygen evolution reaction; Lignin depolymerization; Lignin conversion; GSAM; AEM electrolyzer

Recommended Citations

Citations

  • Naderinasrabadi, M. (2020). A Continuous Electrochemical Process to Convert Lignin to Low Molecular Weight Aromatic Compounds and Cogeneration of Hydrogen [Doctoral dissertation, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1584622583669502

    APA Style (7th edition)

  • Naderinasrabadi, Mahtab. A Continuous Electrochemical Process to Convert Lignin to Low Molecular Weight Aromatic Compounds and Cogeneration of Hydrogen. 2020. Ohio University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1584622583669502.

    MLA Style (8th edition)

  • Naderinasrabadi, Mahtab. "A Continuous Electrochemical Process to Convert Lignin to Low Molecular Weight Aromatic Compounds and Cogeneration of Hydrogen." Doctoral dissertation, Ohio University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1584622583669502

    Chicago Manual of Style (17th edition)

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This open access ETD is published by Ohio University and OhioLINK.