This work addresses biogenic formaldehyde (CH₂O) generated by wood during the manufacture of non-structural wood-based composites, from which CH₂O emissions are regulated. The target for regulation has been anthropogenic CH₂O released from hydrolytically unstable amino resins like urea-formaldehyde. However, current regulations (the Formaldehyde Standards for Composite Wood Products Act, signed into law in 2010 and implemented in 2016) restrict allowable emissions to such low levels that biogenic CH₂O may affect regulation compliance. The industry has met the latest regulations with new amino resin technologies. Nevertheless persistent anecdotal reports suggest that biogenic CH₂O complicates regulation compliance. This work represents an industry/university cooperation to seek a more thorough understanding of biogenic CH₂O, to begin documentation of biogenic CH₂O levels in wood, and to study the conditions and chemical mechanisms of its formation. Efforts began by establishing CH₂O analysis using the fluorimetric acetylacetone determination. A custom 12-liter chamber with controlled temperature and relative humidity, and "ultrapure" nitrogen (N₂) ventilation was created to measure CH₂O emissions from flakes sampled from four Virginia pine (Pinus virginiana) trees. Emissions from never-heated specimens varied significantly among the four trees, ranging from 0.02 – 0.19 µg CH₂O/m³g dry wood. Heating (200°C, 1 hour), followed by chamber equilibration, resulted in significantly increased emissions on the order of 50%. Sequential heating, followed by chamber equilibration (in other words, heat/equilibrate/measure emission/repeat), resulted in declining emissions suggesting that a finite chemical source of CH₂O was being depleted by the sequential heat treatment. Flake specimens were stored in the open laboratory, and over 2-3 months laboratory storage, initially high emitting specimens gradually emitted less CH₂O, and initially low emitters gradually emitted more CH₂O. Concerns over laboratory contamination were perhaps allayed when background levels of laboratory CH₂O were determined to be similar to the background levels in the ultrapure N₂ used to ventilate the chamber. Measurement of emissions was abandoned, and thereafter a simple water extraction technique (~ 94% CH₂O recovery) was used to measure the CH₂O content of never-heated and heated wood specimens, where the difference was identified as CH₂O generated due to heating. Increment cores from living Virginia pine (Pinus virginiana), yellow-poplar (Liriodendron tulipifera), and radiata pine (Pinus radiata) trees were used to measure CH₂O content and CH₂O generation due to heating (200°C, 10 min). Significant variations within and between trees of the same species were observed. Tissue types (juvenile/mature, heartwood/sapwood) sometimes correlated to higher CH₂O contents and greater heat-generation potential; but sometimes not depending upon species. Heating increased CH₂O levels 3-60 fold. Heating with high moisture levels caused greater CH₂O generation than for dry specimens. This moisture effect and a separate serendipitous observation suggested that CH₂O generation is acid catalyzed. Radiata pine generated extraordinarily high CH₂O levels when heated, far exceeding the other two species. It was suggested that pine extractives might catalyze CH₂O generation, perhaps in lignin. Pinus virginiana wood was heated (200°C, 10 or 60 min) while dry or after aqueous/acid or base pretreatment in order to reveal mechanisms of formaldehyde (CH₂O) generation. Among wood structural polymers, lignin was the overwhelming source of biogenic CH₂O, consistent with prior reports. The effects of wood extractives are mentioned below. The selection of acid catalyst strongly affected CH₂O generation as predicted in the acidolysis literature of lignin model compounds and isolated lignins. Lignin methoxyl cleavage was also observed, but was considered an unlikely source of thermochemical CH₂O. Alkaline pretreatments suppressed CH₂O generation. Regarding wood-based composite manufacture, the implications are that lignin reactions can be manipulated during hot-pressing. Potential benefits include reduced product emissions, and/or novel crosslinking strategies using biogenic CH₂O. Heat generation of CH₂O in Virginia pine and radiata pine was substantially reduced by extractives removal, but there was no such effect in yellow-poplar wood. Results suggested that pine extractives promote CH₂O generation by catalyzing or otherwise promoting C2 cleavage (acidolysis) in lignin. Thioacidolysis demonstrated that pine lignin reactions were strongly dependent upon the presence or absence of the extractives. When present, pine extractives seemed to promote C2 cleavage (CH₂O generation), but otherwise reduced the overall extent of lignin degradation. When pine extractives were removed, lignin suffered substantial degradation, but apparently less C2 cleavage since CH₂O generation was reduced. In contrast, thioacidolysis showed that yellow-poplar extractives appeared to promote lignin degradation, but extractives removal had no detectable impact on CH₂O generation. Implications exist for biorefinery research because it was shown that lignin reactions can be strongly affected by wood extractives. Two dimensional, proton-carbon, correlation NMR spectroscopy (2D NMR), and solvent submersion dynamic mechanical analysis (DMA) was used to investigate wood changes caused by heating in the presence or absence of external acid catalysis. 2D NMR was relatively insensitive to fine lignin changes that were detected using thioacidolysis. 2D NMR was effective for observing lignin changes under more extreme heating conditions, and evidence was found for lignin crosslinking reactions that probably occurred through substitution into lignin aromatic rings. DMA showed that most heating conditions caused an increase in the lignin glass transition temperature (Tg), consistent with heat-induced lignin crosslinking. Under one experimental condition of wood heating, DMA showed a reduction in the lignin glass transition temperature (Tg). This suggested that lignin cleavage without subsequent repolymerization might be promoted by carefully controlled conditions, and this has implications for biorefinery research where lignin repolymerization can be problematic. Finally, this work strongly supported the hypothesis that lignin generates CH₂O through well-known acidolysis pathways where CH₂O is borne from the lignin gamma-methylol group. Therefore, it was predicted that upon heating corn (Zea mays L.) stalk should generate less CH₂O than wood because corn stalk lignins exhibit a high degree of coumaric acid esterfication at the gamma-methylol group. This hypothesis was perhaps verified- it was found that in 4 out of 6 experimental heating conditions that corn stalk generated significantly less CH₂O than Virginia pine. / Ph. D.

Polymer blends consisting of hydroxypropyl lignin (HPL ) and commercially available poly(methyl methacrylate) (PMMA ) and poly(vinyl alcohol) (PVA) were evaluated in terms of their morphology, viscoelastic properties and mechanical properties. In the case of HPL/PMMA blends experimental variables included HPL molecular weight, HPL content and method of preparation. Methods of preparation included injection molding and solution casting with THF (a hydrogen bonding solvent ) and chloroform (a non-hydrogen bonding solvent) . SEM results indicated that all HPL/ PMMA blends formed two phase systems. However the domain-matrix interphase varied with the method of preparation and HPL molecular weight. Most notably was that solution cast blends showed domains that were "pulled away" from the matrix whereas injection molded blends showed HPL striations that were closely associated with the matrix. Injection molded blend's T_g values were found to more closely follow predicted T_g values (Flory-Fox equation) and injection molded blends also showed consistently superior material properties. Polymer blends of HPL and PVA were prepared by solution casting and evaluated in terms of HPL content and PVA's solubility parameter. Blends of HPL and PVA formed homogeneous materials over a much broader range of solubility parameters than would be predicted from the theory of matching solubility parameters. It was concluded that hydrogen bonding between hydroxyl groups on both polymers was responsible for the formation of at least partially miscible systems over a wider than expected range of solubility parameters. / M.S.

This investigation was undertaken to further the work of Wagner who isolated coniferyl aldehyde by the treatment of wood with stannous chloride. An attempt has been made to determine whether or not coniferyl aldehyde can be obtained by the action of stannous chloride on two different lignin preparations, and thus answer the question as to whether Wagner’s coniferyl aldehyde came from the lignin of the wood or existed free in the wood. 1. It is unlikely that white pine lignin will yield coniferyl aldehyde when isolated and treated with stannous chloride according to the methods described in this investigation. 2. It is probable that Wagner’s coniferyl aldehyde existed free in the wood. / M.S.

Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) were used to characterize the morphology of solvent cast hydroxypropyl cellulose (HPC) films. These techniques revealed the existence of three phases in the bulk material: 1) an amorphous phase, 2) a crystalline phase, and 3) a phase of intermediate order which arises as a consequence of liquid crystal mesophase formation during solvent evaporation. Characterization of the effect of crosslinking on the tan peak temperature led to the conclusion that these relaxations (as observed by DMTA) are similar to glass transitions (T_g's) involving large-scale cooperative motions of the main chains. This three-phase morphology presents a unique system for study with regard to the resultant morphology of binary blends with lignin. This blend system was prepared by solution blending in pyridine and dioxane, as well as melt-mixing followed by extrusion. A partially miscible system was obtained from all preparation methods; however, the injection molded and dioxane-cast materials were generally distinguished from those blends cast from pyridine solution. Their distinction is explained by an enhanced level of superstructure development in these blends as reflected by DMTA analysis and tensile properties. The dramatic improvement in modulus and tensile strength, particularly for the injection-molded samples, leads to the conclusion that lignin serves to reinforce the amorphous matrix of the resulting composite material. The modification of lignin's polyhydroxy character through ethylation, acetylation, and propoxylation, revealed that specific secondary interactions between the components play a minor role, if any, in determining the state of miscibility in this blend system. However, from the analysis of the interaction parameter, B, it is concluded that the extensive hydrogen bonding within the lignin influences the conformation and chain rigidity of this component which dramatically influences the development of supermolecular morphology, and subsequently the overall morphology of the polymeric blend. This is reflected by a substantial increase in the amorphous volume fraction as detected by both DSC and DMTA. The characterization of blends prepared from the unmodified organosolv lignin with ethyl cellulose and a cellulose acetate/butyrate ester confirms the minimal role of secondary interactions between components. However, the characteristics of the second phase suggest that the formation of liquid crystal domains in the cellulose derivatives significantly contribute to the overall morphology and properties of this blend system, as was noted for the HPC/lignin blend systems. / Ph. D.

For the first time, the bonding patterns of specific carbon atoms in woody plant lignin have been identified in situ. This was accomplished by administering and incorporating into the lignin fraction of Leucaena leucocephala, a tropical hardwood, ferulic acid enriched with ¹³C at either the 1-, 2-, or 3-C atom of the side chain. The plants were grown hydroponically over extended periods of time (28 days) under aseptic conditions in media containing the ferulic acid precursor, and then the tissues were examined by solid-state ¹³C NMR spectroscopy. Consequently, resonances due to the bonding patterns of the specific carbon atoms were determined. These resonances differ substantially from similarly labelled synthetic dehydrogenatively polymerized (DHP) lignin in both spectral profile and relative peak intensities. Subsequent studies using phenylalanine as precursor showed that it was better translocated into the aerial portions of the plant, and that its uptake did not result in distortion of lignification in those tissues, both in amount and monomeric composition. Consequently, the difference spectra obtained by ¹³C NMR analyses of phenylalanine-treated plants confirmed and extended the results obtained with ferulic acid. Evidence for the conversion of both precursors to the monolignols was shown by the difference spectra of [1-¹³C]-precursor-fed tissues, where the dominant resonance at 61-63 ppm is consistent with substructures containing the hydroxymethyl functionality. The spectrum obtained with roots administered [1-¹³C] ferulic acid showed the presence of a minor resonance (170-174 ppm) attributable to carboxylic acids/esters. By allowing the plant to undergo further metabolism by growing in hydroponic media without the precursor, these signals disappeared from the resulting spectrum. The first direct evidence for the dominance of the β-O-4’ linkage of lignin in situ was shown by the appearance of the resonance at 83 ppm corresponding to this substructure in both [2-¹³C] ferulic acid-treated roots and [2-¹³C] phenylalanine-treated roots and stems. Evidence for the occurrence of α-O-carbohydrate or α-O-aryl linkage in intact plant tissues was obtained in the spectra of tissues administered [3-¹³C] ferulic acid and [3-¹³C] phenylalanine. The effect of horseradish peroxidase/H₂O₂ in organic medium (dioxane/aqueous acetate buffer, pH 5, 95:5) on dehydrogenatively polymerized (DHP) lignin was reinvestigated. We found no evidence for vigorous depolymerization of DHP lignin under these conditions, contrary to claims made by Dordick, Marletta and Klibanov (1986, Proc. Natl. Acad. Sci. USA 83:6255-6257). Furthermore, we did not detect ferulic acid as a degradation product following treatment of DHP lignin with HRP/H₂O₂. Both coniferyl alcohol and DHP lignin were used in incubation experiments to determine effects of lignin peroxidase from the white-rot fungus Phanerochaete chrysosporium and H₂O₂ on these substrates. Gel filtration chromatography showed that polymeric materials of high molecular weights were the result of these treatments. Incubation of [1-¹³C], [2-¹³C] and [3-¹³C] coniferyl alcohol with lignin peroxidase/H₂O₂ resulted in products similar to-DHP lignins prepared by horseradish peroxidase/H₂O₂ with respect to occurrence of identical resonances in corresponding solution-state ¹³C NMR spectra. Consequently, the role of polymerization of low molecular weight phenolics as a mechanism for detoxification was ascribed to these fungal peroxidases. / Ph. D.

Multiphase star-like copolymers containing lignin have been synthesized and characterized. All copolymers contained hydroxypropyl lignin (HPL) as the central core. Polycaprolactone (PCL), cellulose propionate (CP) or polystyrene (PS), served as radiating blocks attached to the lignin core in star-like manner. These materials were studied in relation to their structure, morphology, effect on crystallization behavior and application in polymer blends. Three series of semi-crystalline (PCL)_n — HPL have been synthesized with HPL segments of 2,100, 3,500 and 6,400 molecular weight, respectively, and polycaprolactone blocks of varying size. Copolymers were produced by either copolymerizing ɛ-caprolactone or grafting preformed PCL segments onto HPL. The thermal and optical properties of these copolymers were investigated by DSC, DMTA and optical microscopy. The copolymers exhibited variable thermal behavior in relation to composition. The crystallization of PCL blocks was mainly governed by the nature of the HPL phase. PCL block length was another variable that affected crystallinity. The longer the segment, the higher the degree of crystallinity. The compatibility, morphology and mechanical properties of (PCL)_n - HPL copolymers blended with poly(vinyl chloride) were also investigated. Methods used in this study included DSC, DMTA, SEM, TEM and stress-strain testing. The blends were shown to be compatible in all proportions. Mono-hydroxyl terminated cellulose propionate oligomers were synthesized by degradation with hydrogen bromide of a fully substituted, high molecular weight cellulose propionate molecule. Evidence of strict monofunctionality was demonstrated by H-NMR spectroscopy. Thermal analysis results indicated that the oligomers were semi-crystalline and their melting points were functions of molecular weight. (CP)_n — HPL copolymers were synthesized by grafting oligomeric CP segments onto HPL via a coupling agent. The thermal and morphological properties of the copolymers were characterized by DMTA, DSC and TEM. Analysis by thermal methods and by electron microscopy showed strong evidence for microphase separation between HPL and CP segments. Cellulose propionate chains crystallize even at a low degree of polymerization, such as DP 5. The copolymer morphologies exhibit a broad variety of features. They vary from dispersed fibrils to spheres like and alternate lamella type patterns according to composition and molecular weights. The interfacial activity of the copolymers in blends of CP and HPL prepared in the melt state was also investigated. The tensile properties of the ternary blends were altered slightly by the presence of the copolymer. Melt blended cellulose propionate and HPL with low degree of propoxylation forms a miscible system with up to 40% HPL component. The incorporation of 5% of the (CP)_n — HPL copolymer reduces the tensile strength by about 10%. Thermal behavior of melt blended cellulose propionate and HPL with high degree of propoxylation indicates the formation of an incompatible system at any composition. Before the addition of the copolymer the blend exhibits higher toughness, elongation up to 160%, and a Young's modulus of 23 ksi. The copolymer-modified blend shows a decrease in toughness and an increase in tensile strength by about 10%. The synthesis and characterization of (PS)_n — HPL copolymers was accomplished in an analogous manner. When added to blends of PS and HPL, (PS)_n -- HPL produced improved mechanical properties of the blends. Scanning electron microscopy of fracture surfaces demonstrated that the addition of copolymer to the PS/HPL blends improved the adhesion of the two phases. The addition of (PS)_n — HPL copolymer to the 90 PS/10 HPL blend system strongly reduced, by about 10 fold, the particle size of the unmodified blend. No significant difference was observed in the morphology of the 80 PS/20 HPL system. The phases exhibited poor adhesion before and after the addition of copolymer. / Ph. D.

Lignin was refluxed with four different metallic salts. In each case, the salt treatment was followed by treatment with hydrogen sulfide. The SnCl₂ treated lignin possessed the best molding characteristics. To determine the value of the salt treatment and the hydrogen sulfide treatment lignin was treated with SnCl₂ only and molded, lignin was treated with hydrogen sulfide only and molded, and lignin was treated with SnCl₂ followed by hydrogen sulfide and molded. Lignin was not treated in any way was also molded. Lignin treated with SnCl₂ followed by treatment with hydrogen sulfide had the best water absorption characteristics of any run made in this investigation. Lignin not treated at all had the highest relative impact strength. Stannous lignin was condensed with ½ mol, 1 mol, and 2 mols of formaldehyde in the presence of NaOH> All molded samples made from formaldehyde condensed lignin had very poor flow in the mold and very poor water absorption characteristics. Stannous lignin was condensed with a mixture of formaldehyde and furfural. The amount of formaldehyde remained fixed at ½ mol whereas ½ mol, 1 mol, and 1½ mols of furfural were used. A molded sample that had been condensed with a mixture of ½ mol of formaldehyde and 1 mol of furfural had the highest relative impact strength of any sample in this investigation. Stannous lignin was treated with ½ mol, 1 mol, and 2 mols of furfural. Better flow in the mold was obtained when furfural was used than was obtained in any of the other tests. It was found that 1 mol of furfural was the best quantity to use. A run was made using zinc sulfate treated lignin instead of stannous lignin. The zinc sulfate treated lignin when condensed with furfural had a lower per cent of water absorption than the stannous lignin when condensed with furfural. This low water absorption value was equaled only by stannous lignin which was not treated with a condensing agent. / M.S.

O desempenho animal pode ser melhorado pelo incremento na digestibilidade dos alimentos. Um dos elementos neste processo é a acurada caracterização da composição química. Objetivando avaliar quatro métodos para determinar o teor de lignina, foram estudadas cinco gramíneas: Brachiaria brizantha cv. Marandú, Brachiaria brizantha cv. Xaraés (MG-5), Panicum maximum cv. Mombaça, Pennisetum purpureum cv. Cameroon e Pennisetum purpureum cv. Napier. As frações fibrosas da parede celular (PC), fibra em detergente neutro (FDN) e fibra em detergente ácido (FDA) aumentaram conforme as plantas amadureceram, refletindo as mudanças na composição dos componentes da parede celular (celulose, hemicelulose e lignina). Os valores de PC foram superiores aos da FDN indicando solubilização da pectina e outros oligossacarídeos da parede celular na solução de detergente neutro. O método LDA apresentou os menores teores de lignina, evidenciando a solubilização de parte da lignina na solução de detergente ácido. Os resultados de LPer foram maiores que os de LDA, que pode ser devido à oxidação da celulose e pectina pelo permanganato de potássio. Os teores de LK foram maiores que os de LDA possivelmente por contaminação protéica, mas, menores que os de LPer. Os teores de LBA foram maiores que os outros três métodos. A digestibilidade acompanhou, de forma inversa, o estádio de maturidade das plantas. A digestibilidade in vitro apresentou forte correlação negativa com os teores de lignina para todos os métodos, menos para LPer. Encontrou-se um valor de relação de 2,23, entre os métodos LDA e LBA, que, ao ser aplicado, nos teores de LDA, resultou em reta similar ao da LBA. Chama a atenção como este valor de 2,23 é muito próximo ao 2,4 utilizado nas equações B2 e C das frações de carboidratos do \"Cornell Net Carbohydrate & Protein System\" e nas equações do National Research Counsil de 1996, para corrigir o teor de lignina. O método LBA é um método fácil e conveniente para determinar a concentração de lignina em forrageiras e uma boa opção para uso rotineiro nas análises de laboratório. / Animal performance can be improved by enhancing feed digestibility. One of the elements for this process is an accurate characterization of feedstuff chemical composition. With the objective of evaluating four methods used today for lignin determination, five grasses were used: Brachiaria brizantha cv. Marandú, Brachiaria brizantha cv. Xaraés (MG-5), Panicum maximum cv. Mombaça, Pennisetum purpureum cv. Cameroon e Pennisetum purpureum cv. Napier, All fibrous fractions, neutral detergent fiber (NDF), acid detergent fiber (ADF) and cell wall (CW), increased as the plants matured, reflecting the changes in the CW composition (cellulose, hemicellulose and lignin). The values obtained for CW were higher than those obtained for NDF, indicating solubilization of pectin and other cell wall oligosaccharides in the neutral detergent solution. The ADL method produced the lowest lignin values, reflecting lignin solubilization by the acid detergent solution. PerL results were higher than those of ADL, possibly due to hemicellulose and pectin oxidation by potassium permanganate. The values for KL were higher than those of ADL, possibly due to protein contamination, but were lower than PerL values. ABL values were the highest among all methods. Digestibility inversely followed plant maturity throughout the study. In vitro dry matter digestibility showed high negative correlation with lignin contents. A 2,23 ratio between ADL and ABL methods was found, which when applied to ADL values, resulted in a curve similar to ABL method curve. It is interesting to note that, this value of 2,23 is very close to the 2,4 used in carbohydrate fractions B2 and C of the \"Cornell Net Carbohydrate & Protein System\", for the correction of lignin content. The ABL method is easy and convenient for total lignin content determination in forages.

In Hinblick auf den stetig steigenden Bedarf der chemischen Industrie an Grundstoffchemikalien und der teilweise unsicheren Versorgung mit Erdöl und Erdgas ist es notwendig alternative Rohstoffe und Verwertungspfade für die Bereitstellung von Basischemikalien zu finden. Ziel der vorliegenden Arbeit war die Untersuchung der Hydrogenolyse von Lignin in niedermolekulare Produkte unter Verwendung geeigneter Salzschmelzen. Es konnte gezeigt werden, dass Lignin in Zinkchlorid/Kaliumchloridschmelzen in niedermolekulare Produkte abgebaut werden kann. Hierbei erwiesen sich der Einsatz eines entsprechenden Eutektikums und einer Alternativschmelze mit niedrigem Schmelzpunkt als hilfreich. Durch den Einsatz verschiedener Apparaturen wurden Untersuchungen in statischer und dynamischer Atmosphäre durchgeführt. Es ergaben sich während der Untersuchung Abhängigkeiten der Hydrogenolyse von verschiedenen Reaktionsparametern. Optima der Umsetzung hinsichtlich der Reaktionsparameter Temperatur, Zeit und Ligninanteil in der Schmelze wurden herausgearbeitet. Die Ausbeute an gewünschten Flüssigprodukten wurde, im Untersuchungsbereich, an diesen Punkten maximiert. Gleichzeitig war die Rückstands- und Gasbildung eingeschränkt. Es konnten Erkenntnisse eines komplexen Systems der Abhängigkeiten der Ausbeuten an Reaktionsprodukten von den Parametern der Untersuchung gewonnen werden. Die Hydrogenolyse von Lignin führte zur Aromatisierung fester Residuen sowie zur Abreicherung von Sauerstofffunktionalitäten. Komplexe Reaktionsmechanismen bewirkten den Abbau von Methoxyl-, Carboxyl- und Hydroxylgruppen der Ligninstruktur. Carbeniumionmechanismen konnten als wichtige Reaktionen zur Spaltung von Ether Arylbindungen identifiziert werden. Die Freisetzung von Monomeren und die Polymerisation anderer Intermediäre sind durch Sekundärreaktionen denkbar. Die gebildeten Flüssigprodukte bestanden hauptsächlich aus Monoaromaten (v.a. Guajakole und Kresole) und wenigen Polyaromaten. Die Selektivität der Bildung einzelner Verbindungen war gering, d.h. die Flüssigprodukte sind eine heterogene Mischung mit geringen Konzentrationen der Einzelsubstanzen. Die Unterschiede in der Struktur der Ausgangslignine bildeten sich auch in der Zusammensetzung der Flüssigprodukte ab. / In view of the steadily increasing demand of the chemical industry to base chemicals and the partial uncertain supply of crude oil and gas, it is necessary to find alternative raw materials and conversion routes for the provision of basic chemicals. The aim of the present work was to investigate the hydrogenolysis of lignin in low molecular weight products using appropriate molten salt media. It could be demonstrated that lignin can be convert in low molecular weight products using zinc chloride/potassium chloride molten salt media. The use of an appropriate eutectic melt and of an alternative melt with low melting point proved helpful. By the use of different apparatus investigations in static and dynamic atmosphere could be carried out. During the investigation dependencies of the hydrogenolysis of various reaction parameters are submitted. Optima of the hydrogenolysis regarding to reaction temperature, time and lignin content at the melt could be identified. The yields were maximized at these points in the range of investigation. Concurrently formation of gases and residues were suppressed. Some evidence of a complex system of the dependencies of the yields of reaction products are obtained from the parameters of the investigation. Hydrogenolysis of lignin leads to aromatic solid residues and to a loss of oxygen containing structures. Structures containing methoxyl-, carboxyl- and hydroxyl groups are degraded by various complex reaction mechanisms. Mechanisms of the formation of carbonium ions were identified as important reactions of the cleavage of ether aryl bonds. Secondary reactions caused the liberation of monomers and polymerisation of some intermediaries. The resulting liquid products consist mainly of monoaromatics (guaiacols and cresols) and less of polyaromatics. The selectivity of the formation of single compounds was low, i.e. the liquid products constitute a heterogenous mixture with low concentrations of the single compounds. The structural differencies of the feedstock lignins also showed at the composition of the liquid products.

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