Solvent Effects on Organosolv Lignin fromPinus caribaea hondurensis

Abstract

Keywords Lignin analysis Organosolv lignin Molccular wcight (Mini, Mw and MWD) dctcrminations Hilücbrand's solubility paramctcr Sawdust Pinus caribaea hondurensis SummaryLignin from Pinus caribaea hondurensis sawdust (pre-extracted with bcnzenc/mcthanol 1:1) was obtaincd by pulping using ninc diffcrent organic solvcnts (in 9:1 mixturcs with 2.0 N HC1 aqucous Solutions) in a stainlcss stcel rcactor at 125 °C for six hours.Thc obtaincd lignins wcrc charactcrizcd by chcmical analysis (clcmcntal analysis, mcthoxyl and phcnolic hydroxyl groups) and by infrarcd spcctroscopy. Morcovcr, the avcrage molccular wcights (Mn, Mw and MWD) werc dctcrmincd by vapor phasc osmomctry and high pcrformancc-size exclusion chromatography and shown thrcc diffcrent pattcrns according to thc solvent mixturcs cmploycd. The yields of lignin dcpcnd on the acccssibility and nuclcophilicity of thc solvcnts äs well äs on thc lignin solubility, and are rclatcd to thc Hildcbrand's solubility paramctcrs ( ) of the solvent mixturcs. The plot of lignin yields against 6 show a charactcristic "Bell shapc" curvc wilh maximum at 23 MPa l/2 corrcsponding to thc lignin solubility paramctcr. IntroductionPulping processes can be divided into three main groups, depending on the solvent System employed: -Aqueous processes: These pulping processes use water äs solvent and inorganic reagents to cleave the protolignin to water soluble fragments. The inorganic reagents are generally used in high concentrations and the processes are carried out at high temperatures and pressures. -Organosolv processes: These processes use organic solvents, commonly in association with water and, in the most cases, an acid catalyst. In the acid catalyzed organosolv processes, water acts äs nucleophilic agent and reacts with reactive centers (which have been activated by the catalyst) in the protolignin. Organosolv processes generally use lower temperatures and pressures than the aqueous processes, and differ from in the recovery of the Chemicals, in organosolv processes only the solvent has to be recovered. -Mixed processes: The solubilization power of the organic solvents can be used in association with water and inorganic reagents producing mixed processes. These Systems are also performed at high temperatures and pressures and the inorganic reagents have to be recovered due to economical reasons. Organosolv processes making use of alkaline reagents are included in this group.

Comparative study of three lignin fractions isolated from mild ball‐milled Tamarix austromogoliac and Caragana sepium

“…The solvent primarily acts on the promotion of vegetal tissue impregnation and the solubilization of the lignin fragments so produced. 30 In this study, posttreatment of 80% acidic dioxane extracted TA and CS with 50% aqueous ethanol containing 1M TEA at 708C for 4 h resulted in 27.3 and 33.3% removal of the original lignin, respectively. As expected, the yield of acid-insoluble lignin (4.3% from TA and 4.8% from CS) was much higher than that of the acid-soluble lignin (1.0% from TA and 1.4 from CS), indicating a slight degradation reaction during the posttreatment with 50% aqueous ethanol under the organic alkali condition (1M TEA) because these acid-soluble phenolic compounds of low molecular weight were released as a result of lignin degradation.…”

Extraction of lignin from sugar cane bagasse and Pinus taeda wood chips using ethanol–water mixtures and carbon dioxide at high pressures

“…The water acts as a nucleophile and reacts with centers activated by the catalyst in the protolignin ("in situ lignins"). The solvent solubilizes the lignin and impregnates the plant tissue, carrying the reagents to the protolignin and the resulting lignin fragments from the inner part of the cell to the solution [11]. A possible modification in the organosolv processes, which could offer improved yields of pulp, regardless of the raw material used, consists in a change of the experimental conditions, high pressure being employed to allow the main pulping processes to occur in sub-and supercritical conditions.…”

Extração da lignina e emprego da mesma em curvas de calibração para a mensuração da lignina em produtos vegetais

“…ROSSINI et al (1989) empregaram diversos solventes para extrair lignina da serragem da madeira Pinus caribaea hondurensis, obtendo de 2,0 a 6,6% de rendimento. A obtenção de lignina foi melhorada, quando a extração foi catalisada por um ácido mineral, variando de 1,1 a 24,4%, em relação ao peso seco da madeira (BALOGH et al, 1989).…”