Search results for "ligniini"
showing 10 items of 25 documents
Novel concepts on the recovery of by-products from alkaline pulping
2016
Innovative biorefinery concepts were developed for the separation and utilization of organic materials, especially aliphatic carboxylic acids, lignin, and extractives, which are formed as by-products during wood-based alkaline delignification processes. The partial recovery of sodium as NaOH and aliphatic carboxylic acids from hardwood soda-AQ black liquor was studied via electrodialysis. The lignin was partly (about 59 % of the initial lignin) precipitated from black liquor by carbonation (pH to about 8.5) followed by electrodialysis or H2SO4 (pH to about 2), with subsequent precipitation of more lignin and the liberation of aliphatic acids. The Na2SO4 formed was successfully separated fro…
Valorization potential of technical lignins from Norway spruce (Picea abies) via pyrolysis
2022
Analytical pyrolysis (Py-GC/MS) on mg-scale of Norway spruce (Picea abies)-derived kraft lignin, ethanosolv lignin, and dried lignin-rich soda-anthraquinone (AQ) black liquors was studied at 500 °C to compare the valorization potential of these materials, focusing on the type and yield of condensable pyrolysis products. Of particular interest was the relatively selective formation of guaiacol (2-methoxyphenol) from the dried soda-AQ black liquors in contrast to the formation of complex phenolic product mixtures from the pyrolysis of the kraft and ethanosolv lignins. It was shown that this finding could be attributed to differences in composition and structure as was assessed by various NMR …
Säteilyn aiheuttamat värinmuutokset korkeasaantoisessa massassa
2017
Korkeasaantoisen havusulfaattimassan sähkömagneettisen säteilyn aiheuttama kellastuminen aiheutuu puun natiiveista sekä sulfaattikeiton aikana syntyvistä kromoforeista. Kromoforit ovat kemiallisia rakenteita, jotka absorboivat säteilyä näkyvän valon alueelta, minkä seurauksena syntyy värejä. Kellastumisen aiheutumiseksi kemialliseen rakenteeseen on synnyttävä kromoforisia rakenteita, jotka absorboivat näkyvää valoa sini-viher-alueella. Havupuiden osalta kromoforisia rakenteita esiintyy ligniinissä, uuteaineissa sekä hiilihydraattien johdannaisissa. Lopputyöni kirjallisessa osassa perehdytään havupuiden natiivien sekä sulfaattikeiton aikana syntyvien kromoforien ominaisuuksiin sekä muodostum…
Advanced biorefinery concepts related to non-wood feedstocks
2018
Agricultural residues, such as wheat straw (Triticum aestivum), okra stalk (Abelmoschus esculentus), and giant miscanthus (Miscanthus × giganteus, a hybrid of M. sinensis and M. sacchariflorus) were investigated to assess their possible consumption for integrated lignocellulosic biorefining. The efficient fractionation and recovery of all important chemical components (cellulose, hemicelluloses, and lignin) of such feedstocks are a prerequisite for realistic biorefinery concepts. Water is one of the most eco-friendly solvents with the highest potential for industrial use, and it is also suitable for full-scale biorefinery purposes. For example, under pressure at elevated temperatures over 1…
Lignin recovery from spent alkaline pulping liquors using acidification, membrane separation, and related processing steps: A Review
2019
The separation of lignin from the black liquor generated during alkaline pulping is reviewed in this article with an emphasis on chemistry. Based on published accounts, the precipitation of lignin from spent pulping liquor by addition of acids can be understood based on dissociation equilibria of weak acid groups, which affects the solubility behavior of lignin-related chemical species. Solubility issues also govern lignin separation technologies based on ultrafiltration membranes; reduction in membrane permeability is often affected by conditions leading to decreased solubility of lignin decomposition products and the presence of colloidal matter. Advances in understanding of such phenomen…
Chemical Pretreatments of Wood Chips Prior to Alkaline Pulping - A Review of Pretreatment Alternatives, Chemical Aspects of the Resulting Liquors, an…
2015
The chemical industry is being forced to evaluate new strategies for more effective utilization of renewable feedstocks to diminish the use of fossil resources. In this literature review, the integration of both acidic and alkaline pretreatment phases of hardwood and softwood chips with chemical pulping is discussed. Depending on the pretreatment conditions, high-volume sulfur-free fractions with varying chemical compositions can be produced. In case of acidic pretreatments, the major products include carbohydrates (mono-, oligo-, and polysaccharides), whereas under alkaline (i.e., aqueous NaOH) pretreatment conditions, the sulfur-free fractions of aliphatic carboxylic acids, lignin, and ex…
Activated carbon from hydrolysis lignin: Effect of activation method on carbon properties
2022
This study presents the effects of different activation methods to produce activated carbon from the hydrolysis lignin. Pretreatment of the feedstock with common mineral acids (HCL, HNO3, and H3PO4), different steam rates for physical activation, and different chemical activating agents (ZnCl2, Na2CO3, and KOH) for chemical activation were investigated. The pretreated biomass was carbonized and activated in one-stage process and the surface characteristics, such as total pore volume, pore size distribution and specific surface area, were investigated. The results showed that the activated carbon surface properties were not greatly affected by acid pretreatment. Brunauer-Emmett-Teller (BET) …
Rapid one-step solvent-free acid-catalyzed mechanical depolymerization of pine sawdust to high-yield water-soluble sugars
2017
Abstract One-step absolute solvent-free acid-catalyzed mechanical depolymerization of pine sawdust (PSD) and commercially available α-cellulose to water-soluble sugars was carried out using ball milling. For comparison purposes, the commonly reported “solvent-free” mechanocatalytic depolymerization of lignocellulose method, which normally involves three steps (acid impregnation in solvent, vacuum drying, and mechanical depolymerization of lignocellulose), was performed. The 3,5-dinitrosalicylic acid (DNS) method was used to measure the total reducing sugar (TRS) of the obtained sugar solution, and major monosaccharides in the solution were analyzed by capillary electrophoresis (CE). More th…
Ligniinin osuuden vaikutus ligniini-fenoliformaldehydihartsien kemiaan
2017
Fenoliformaldehydihartsia valmistetaan fenolista ja formaldehydistä, joka toimii ristisilloitusagenttina. Katalyyttinä käytetään natriumhydroksidia. Formaldehydi liittyy fenolin renkaaseen hydroksyyliryhmän para- tai orto-asemiin additioreaktiolla alkalisissa olosuhteissa. Fenolin alkalointi saa aikaa renkaaseen karbanioneja, joihin formaldehydin elektrofiilinen hiiliatomi voi liittyä. Reaktio tunnetaan Lederer-Manasse-reaktiona. Ligniini on amorfinen biopolymeeri, jota saadaan esimerkiksi sulfaattiprosessin sivutuotteena. Rakenteellisesti ligniinistä voidaan erottaa kolme fenyylipropaaniyksikköä, jotka ovat p-kumaryylialkoholi, koniferyylialkoholi ja sinapyylialkoholi. Ligniinillä voidaan …
Combustion behavior of black liquors : droplet swelling and influence of liquor composition
2017
The combustion of black liquor (BL) in a recovery boiler is a central process in a kraft pulp mill for recovering the cooking chemicals and for producing heat and power. This work explored the most important combustion behavior of BL, the swelling of in-flight droplets, from the viewpoint of liquor composition. It also studied the combustion behavior of BL droplets obtained from two biorefining subprocesses (carbonation and hot-water pretreatment, HWP) and sulfur-free pulping alternatives (soda-anthraquinone (AQ) and oxygen-alkali pulping). The formation of a plastic state essential for the swelling of BL droplet was found to result from the melting of an array of carbohydrate-derived aliph…