Abrasive Stripping Voltammetric Studies of Lignin and Lignin Model Compounds

Abstract

Lignin is potentially a major renewable, nonfossil source of aromatic and cyclohexyl compounds. In this study, we have investigated the abrasive stripping voltammetry of lignin and four lignin model compounds in the room temperature ionic liquids (RTILs) [C 4 À ¼ trifluoromethanesulfonate) on a gold macrodisk and in 0.1 M H 2 SO 4 and 0.1 M NaOH on a boron-doped diamond (BDD) macroelectrode, with the hope of using the voltammetry to fingerprint the functional groups within the lignin molecule. The use of RTILs on metal electrodes, or either acidic or basic media in combination with BDD electrodes allows solvent systems with wide electrochemical potential windows, useful for studying voltammetry which may be difficult to observe in systems where early breakdown of the solvent occurs.

Ionic Liquids for Lignin Processing: Dissolution, Isolation, and Conversion

“…[73] Oxidation of dissolved Kraft lignin was performed and a variety of products were obtained, including vanillin and at least nine other identified aromatics. In line with what can be inferred from the work of Chen et al [81] described above, as the oxidation potential was made more positive, the products had correspondingly smaller molecular weights correlating with a greater degree of cleavage. [73] Conclusion and Outlook ILs can be successfully employed at many stages of a potential biorefinery, from facilitating biomass grinding [71] through to whole-biomass dissolution or selective component extraction.…”

“…They demonstrated the utility of this system in abrasive stripping voltammetry, whereby insoluble material is rubbed onto the surface of the electrode and the electrochemical response used to fingerprint or identify the composition of the solid material, or even quantify it. [81] Excitingly, multiple peaks were observed, at different potentials for different lignin model compounds. In the context of analytical chemistry, fingerprinting the origin of wood or lignin samples is therefore feasible.…”

“…[13] ILs themselves make excellent electrolytes, displaying inherent conductivity, frequently displaying large electrochemical windows, and incorporating the ability to tailor electrochemical response by choice of IL. [24] Chen and coworkers [81] were apparently the first to investigate lignin electrochemistry in ILs, although with particles of insoluble Kraft lignin or lignin model compounds immobilized at an electrode surface in contact with [Bmim][N(SO 2 CF 3 ) 2 ]. They demonstrated the utility of this system in abrasive stripping voltammetry, whereby insoluble material is rubbed onto the surface of the electrode and the electrochemical response used to fingerprint or identify the composition of the solid material, or even quantify it.…”

Developing energy efficient lignin biomass processing – towards understanding mediator behaviour in ionic liquids

“…This is possibly related to the oxidation of the hydroxyl (OH) group on either the -carbon or -carbon (see Figure 8). 36 (Figures 11 and 12). However, organosolv lignin caused a significant increase in the second oxidation peak of ABTS ( Figure 10).…”

“…Also, they possess a wide window of electrode potential and no addition of supporting electrolyte is required, which can assist electrochemical processes such as the oxidation of lignin. 35,36 When compared to conventional solvents, however, ILs are commonly 10-100 times more viscous, and the diffusion rates of species in these media are lowered accordingly.…”