Rice Husk Hydrolytic Lignin Transformation in Carbonization Process

Abstract

Lignin processing products have an extensive using range. Because products properties depend on lignin precursor quality it was interesting to study lignin isolated from rice husk being a large tonnage waste of rice production and its structural transformations during carbonization. Lignin isolated by the thermal hydrolysis method with H2SO4 1 wt % solution and its carbonized products prepared under different carbonization conditions were characterized using elemental analysis, IR, TPD-MS, XRD, TEM, and EPR. It was shown lignin degradation takes place over the wide (220–520 °C) temperature range. Silica presenting in lignin affects the thermal destruction of this polymer. Due to the strong chemical bond with phenolic hydroxylic group it decreases an evaporation of volatile compounds and as a result increases the temperature range of the lignin degradation. Rice husk hydrolytic lignin transformations during carbonization occur with generation of free radicals. Their concentration is decreased after condensation of aromatic rings with carbon polycycles formation, i.e., the graphite-like structure. Quantity and X-ray diffraction characteristics of the graphite-like phase depend on carbonization conditions. Morphology of the lignin-based carbonized products is represented by carbon fibers, carbon and silica nanoparticles, and together with another structure characteristics provides prospective performance properties of lignin-based end products.

Rice Husk Research: From Environmental Pollutant to a Promising Source of Organo-Mineral Raw Materials

“…The pyrolysis stage with T max ~350 °C occurs due to the degradation of aromatic compounds of lignin, which proceeds in a wider temperature range with the formation of phenol ( m / z = 94, T max = 350 °C), pyrocatechol ( m / z = 110, T max = 290–330 °C), cresols ( m / z = 107, T max = 365 °C), tropylium ion, C 7 H 7 + ( m / z = 91, T max = 340 °C), 4-vinyl-methylguaiacol ( m / z = 164, T max = 290 °C), benzene ( m / z = 78, T max = 360, 545 °C), naphthalene ( m / z = 128, T max = 520 °C), and 4-vinylphenol ( m / z = 120, T max = 220, 290 °C). The formation of these compounds is caused by thermal transformations of corresponding aromatic links and functional groups of lignin [ 35 ]. The stage with T max ~200 °C corresponds to the destruction of hemicelluloses [ 36 ].…”

Catalytic Pyrolysis of Lignin Model Compounds (Pyrocatechol, Guaiacol, Vanillic and Ferulic Acids) over Nanoceria Catalyst for Biomass Conversion

“…Since the structure of this natural polymer is extremely complex, model compounds are often used to study its conversion to high value-added chemicals [8,10]. Ferulic and vanillic acids, as well as pyrocatechol and guaiacol are common products of lignin processing [1,8,[11][12][13], and therefore are often used as model lignin compounds [4,8,11,[14][15][16][17]. These compounds are lignin structural units of various sizes and contain almost the entire list of functional groups present in the lignin macromolecule.…”

Physicochemical properties of porous activated carbon prepared from palm kernel shell through a low-cost activation protocol

“…The reason for this is that, at a higher carbonisation temperature, more acid and/or volatile substances will evaporate from the sample, thereby reducing the carbon yield. 50 Yefremova et al 53 proposed that the decrease in the yield of carbonised products at higher pyrolysis temperatures may be due to the increase in the primary decomposition of the precursor and the increase in the secondary decomposition of the formed carbon material. Mussatto et al 49 , Hayashia et al 54 and Wu et al 55 reported similar results from biomass materials.…”