Effect of Solvents on Fe–Lignin Precursors for Production Graphene-Based Nanostructures

Abstract

Kraft lignin was catalytically graphitized to graphene-based nanostructures at high temperature under non-oxidative atmospheres. To obtain the best catalytic performance, a uniform catalyst–lignin mixture must be made by bonding transitional metal (M) ions to oxygen (O), sulfur (S) or nitrogen (N)-containing functional groups in kraft lignin. One of the strategies is to dissolve or disperse kraft lignin in a suitable solvent, whereby the polymer chains in the condensed lignin molecules will be detangled and stretched out while the functional groups are solvated, and when mixing lignin solution with catalyst metal solution, the solvated metal ions in an aqueous solution can diffuse and migrate onto lignin chains to form M-O, M-S, or M-N bonds during the mixing process. Therefore, solvent effects are important in preparing M–lignin mixture for production of graphene-based nanostructures. Fe–lignin precursors were prepared by dissolving lignin with different solvents, including water, methanol, acetone, and tetrahydrofuran (THF). Solvent effects on the catalytic performance, size and morphology of graphene-based nanostructures were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), and nitrogen sorption measurements. The sizes, morphologies, and catalytic properties of the products obtained from Fe–lignin precursors are greatly influenced by the solvents used. It was found that Fe–lignin (THF) had the highest iron dispersion and the smallest iron particle size. Furthermore, Fe–lignin (THF) exhibited the best catalytic performance for graphitization of kraft lignin while the graphitization degree decreased in the order: Fe–lignin(THF) > Fe–lignin(Acetone) > Fe–lignin(methanol) > Fe–lignin(water).

Effect of Precursors of Fe-Based Fischer–Tropsch Catalysts Supported on Expanded Graphite for CO2 Hydrogenation

“…The phase state of iron species was mainly γ-Fe 2 O 3 , only containing a small amount of χ-Fe 5 C 2 ; the carbonization degree of these two catalysts was extremely low. Yan 59 and Lü6 0 found that Fe with a smaller particle size was much easier to be reduced and carbonized during the Fischer−Tropsch reaction. Combined with the previous results of electronic properties and iron particle sizes, it could be inferred that for FeNa/EG-O, although it contained a small amount of N doping and was relatively easy to be reduced compared with FeNa/EG-C, it was difficult to be carbonized during the reaction process due to its large particle size of iron.…”

A Study of the Key Factors on Production of Graphene Materials from Fe-Lignin Nanocomposites through a Molecular Cracking and Welding (MCW) Method

“…In the Fe-lignin composites, iron ions were uniformly distributed throughout lignin molecules by chelating to the oxygen-containing functional groups [ 37 ]. These Fe-lignin composites are thermally unstable and are decomposed to lignin char embedded with nano iron oxide particles when heated at 200–300 °C [ 37 , 38 ].…”

“…In the Fe-lignin composites, iron ions were uniformly distributed throughout lignin molecules by chelating to the oxygen-containing functional groups [ 37 ]. These Fe-lignin composites are thermally unstable and are decomposed to lignin char embedded with nano iron oxide particles when heated at 200–300 °C [ 37 , 38 ]. At elevated temperatures, the lignin char was catalytically carbonized, and alien elements, oxygen, and hydrogen in the lignin char were eliminated as gaseous water, carbon monoxide, carbon dioxide, and hydrogen ( Figure 1 a).…”

Green Synthesis of Cellulosic Nanofiber in Enset Woven Fabric Structures via Enzyme Treatment and Mechanical Hammering

“…Mostly the fine fibers were obtained by this concentration up to 2m diameter size. The peak of wave length of 1100 cm -1 , corresponding to C-O stretching conjugate (lignin) and 1321 cm -1 , ring condensed stretching (lignin) revealed the removal of excess lignin from enset fibers [32]. Moreover, there was a clear peak shape difference between untreated and treated enset fiber at wave number of 1100cm 1 .…”