Patent Description:
Bark is an external tissue of plants. In the current technologies of biomass processing, such as Kraft pulping in paper industry, it is separated from trunks and treated as waste. Higher heating value of bark <NUM>-<NUM> MJ·kg-<NUM> justifies its burning for electricity production, unless more advanced procedures are developed.

Bark tissue consists of various biopolymers, tannins, lignin, suberin, suberan and polysaccharides. Up to <NUM>% of the bark tissue is made of lignin. While lignin is very abundant in other tissues as well, suberin is a specific component of bark and serves as a protective barrier of plant. Lignin is an aromatic polyether formed by oxidative coupling of sinapyl and co-niferyl alcohols. Suberin is a poorly functionalized aliphatic polyester composed of hydroxylated fatty acids. Lignin and suberin domains are highly crosslinked and form an insoluble rigid network.

In any process for conversion of bark into chemicals and/or fuels, these polymeric substances must be partially depolymerized and solubilized in order to make them accessible to chemical modification. Methods of lignin extraction have been widely studied for other types of biomass. In particular, the organosolv procedure has been developed with an intention to provide a more environmentally friendly technique as an alternative to traditional Kraft pulping. In this type of processes, the biomass is treated with organic solvents (MeOH, EtOH, dioxane) mixed with water in presence of acids and other additives at <NUM>-<NUM>. To address the emerging issues of lignin repolymerization, so-called lignin-first methodologies have been developed. The extracted lignin is subjected to in situ catalytic transformations and forms stable products, i.e. intermediates are directly trapped. A common example of lignin-first approach is metal-catalyzed hydrogenolysis where lignin is reduced into stable phenolic monomers. In "<NPL>ET AL describe a process of bark fractionation comprising depolymerization of lignin and suberin.

In general, lignin-suberin complex is not depolymerized under typical organosolv extraction conditions and its cleavage requires alkaline treatment. The known procedures do not allow to recycle the solvent and thus make the process energetically inefficient. Moreover, the extracted bio-oil is contaminated with salts. There is thus a need for a solution where these drawbacks could be eliminated.

The present invention provides a solution that eliminates the drawbacks of the prior art that includes avoiding the use of metal catalyst and implementing a volatile base instead of alkaline salt.

The invention uses a solvent system comprising water, a base selected from tertiary aliphatic amines, and optionally a low boiling alcohol. The composition of the solvent system allows for recirculating the solvent system in the process. Moreover, the composition of the solvent system also allows for the solvent system to be evaporated in the process, e.g. for the purpose of separating the solvent system, for use in a second, and further cycles, of the process.

Accordingly, in a first aspect the invention relates to a process for at least partly dissolving in a solvent system substances of bark, which bark contains a suberin component, and for at least partly depolymerising the suberin component, comprising the following steps: providing bark; providing a solvent system comprising water, and a base selected from tertiary aliphatic amines; treating the bark with the solvent system by subjecting the bark to the solvent system at a temperature of at least <NUM>, thereby obtaining a composition containing at least partly dissolved substances of bark, of which substances the suberin component is at least partly depolymerised.

In a second aspect the invention relates to a process for preparing a fuel, which process, in addition to the above steps, also comprises the following additional steps: subjecting the composition resulting from the treatment step to filtration, so as to separate from the composition any solid bark residues; separating by evaporation the solvent system from the filtrate obtained in the filtration step, so as to obtain a product mixture; and, hydrotreating the product mixture, thereby obtaining a fuel. In this aspect an alcohol is included in the solvent system.

In preferred embodiments of the inventive processes, the solvent system is recycled back to the treatment step. The used solvent system can be recycled by evaporation of the used system from the composition, however it is preferred that the solvent system is not evaporated from the composition until bark has been added to the solvent system corresponding to a lower limit of solvent to bark ratio of V ≈ <NUM>·kg-<NUM>. Accordingly, in the inventive processes, the composition is preferably recirculated back to the bark addition and treatment step until a total amount of bark has been added to the solvent system corresponding to a ratio of solvent system to bark of V ≈ <NUM>·kg-<NUM> in the composition, at which point the solvent system is evaporated from the composition. Any solid bark residues in the composition is preferably separated by means of filtration from the composition before being recirculated to the treatment step.

In a preferred embodiment of the inventive process for preparing a fuel, the product mixture is mixed with, as a carrier liquid, a plant-derived oil, such as tall oil fatty acid (TOFA) or rapeseed oil. More preferably, the composition is a suspension of said mixture in TOFA.

Preferably, the hydrotreatment is performed by hydrodeoxygenation. In a preferred embodiment the hydrotreatment produces C<NUM>-C<NUM> hydrocarbons, preferably C<NUM>-C<NUM> hydrocarbons. The hydrotreatment may suitably be carried out at a temperature within a range of <NUM>-<NUM>, preferably <NUM>-<NUM>, and at a hydrogen pressure within a range of <NUM>-<NUM> bar, e. g about <NUM> bar. The duration of the hydrotreatment may e.g. be <NUM>-<NUM> hours.

In a third aspect the invention relates to a preferred composition, which can be used in the inventive processes, which composition comprises a mixture of bark having a particle size of not more than <NUM> in a solvent system, the solvent system comprising: water at a content of at least <NUM> % by volume; triethylamine at a content of <NUM>-<NUM> % by volume; and, methanol at a content of <NUM>-<NUM> % by volume of the total volume of the solvent system.

In the inventive processes the substances of bark are at least partly dissolved in the solvent system, and of which substances the suberin component of bark is at least partly depolymerised.

Primary and secondary aliphatic amines are not suitable for use in the invention, since these form amides when reacting with esters. Ammonium is not suitable either.

The tertiary aliphatic amine is preferably a simple tertiary aliphatic amine, more preferably a trialkylamine, such as triethylamine (Et<NUM>N), trimethylamine (Me<NUM>N), dimethylethylamine, or diethylmethylamine, and most preferably triethylamine (Et<NUM>N).

Preferably, the inventive solvent system further comprises an alcohol, preferably a low boiling alcohol such as methanol, ethanol, or propanol, or a mixture of low boiling alcohols, most preferably the alcohol is methanol.

In further preferred embodiments of the inventive processes, the degree of solubilization of the bark in the solvent system is at least <NUM>%, preferably at least <NUM>% and more preferably <NUM>-<NUM>%.

In yet further preferred embodiments of the inventive processes, the composition obtained after the treatment step comprises a variety of oligomeric products of suberin and lignin, each molecule being composed of <NUM>-<NUM> monomeric units of lignin and/or suberin, and the whole mixture having the number-average molecular weight <NUM> Da and the weight-average molecular weight <NUM> Da, according to SEC data.

Upon further treatment in alkaline conditions the bark containing composition affords a mixture of fatty acids having a chain length of <NUM>-<NUM> carbons, the fatty acids being saturated or unsaturated, and optionally substituted by at least one hydroxy group. Preferably the mixture of fatty acids includes at least two of <NUM>-hydroxyoctadec-<NUM>-enoic acid, <NUM>,<NUM>-octadec-<NUM>-enedioic acid, <NUM>,<NUM>-octadecanedioic acid, <NUM>-hydroxyeicosanoic acid, <NUM>,<NUM>-eicosanedioic acid, <NUM>,<NUM>-docosanedioic acid, <NUM>,<NUM>-dihydroxyoctadecane-<NUM>,<NUM>-dioic acid, and <NUM>-hydroxydocosanoic acid.

The inventive solvent system used preferably comprises from <NUM>-<NUM> % by volume of the amine, more preferably <NUM>-<NUM> %, even more preferably <NUM>-<NUM> % by volume, and most preferably no more than <NUM>% by volume of the amine.

The solvent system used according to the invention preferably comprises a low boiling alcohol. When present, the low boiling alcohol is preferably in an amount of up to <NUM>% by volume, more preferably up to <NUM>%. Preferably the alcohol is included in an amount of at least <NUM>% by volume of the solvent system.

It is preferred that the solvent system comprises at least <NUM> % by volume of water.

Preferably, the combined amounts of amine, water, and, when present, alcohol, constitute <NUM> % by volume of the solvent system.

In a preferred embodiment the inventive solvent system comprises:.

of the total volume of the solvent system.

The bark used in the invention is preferably bark having a high content of suberin and lignin, such as Quercus Suber (oak) or Betula Pendula (birch) bark, preferably Betula Pendula bark.

In the inventive processes, the treatment temperature is preferably at least <NUM>, and preferably up to <NUM>, such as within a range of <NUM>-<NUM>, more preferably within a range of <NUM>-<NUM>, preferably at the most <NUM>, and most preferably in the range of <NUM> to <NUM>.

In the inventive processes, the heating is preferably performed for at least <NUM> hours, preferably for <NUM> to <NUM> hours, and most preferably for <NUM> to <NUM> hours.

The ratio of MeOH:H<NUM>O in the solvent system is preferably from <NUM>:<NUM> to <NUM>:<NUM> by volume, such as <NUM>:<NUM> by volume.

According to the invention, the bark is preferably in the form of finely divided particles, such as milled bark particles, preferably having a particle size of not more than <NUM>, more preferably around <NUM> or smaller. Preferably, the bark is a bark having a high content of suberin and lignin, such as Quercus Suber or birch bark, preferably birch bark. It is also preferable that the composition obtained as a result of the depolymerization reaction performed on the finely divided bark, for depolymerizing the suberin component of bark at least partly, in the process is subjected to filtration and any solid bark residues are separated and discarded. Preferably, the filtrate obtained by the filtration is recycled at least once and used as solvent system for the next portion of bark to be subjected to depolymerisation conditions for at least partly depolymerising the suberin component in the bark.

Preferably, the solvent system, after completion of the depolymerisation treatment of the bark for depolymerising at least partly the suberin component in the bark, is separated from the resulting reaction mixture by evaporation and recycled for use as solvent system for new portions of bark to be subjected to depolymerisation treatment for depolymerising at least partly the suberin component.

The inventors of the present invention have surprisingly found that by using the solvent system of the invention, it is possible to provide a salt- and metal-free solvent system that is recyclable and affords to solubilize bark, such as e.g. bark of birch (Betula Pendula) to a very high degree (for birch bark <NUM>% (<NUM>% of wax-free bark)). This clearly solves the problems of the prior art solutions.

In the following, the present invention is explained in more detail, by way of example only, and should not be construed as limiting the scope of protection sought in the appended claims. In this detailed description it is referred to the following figures, wherein:.

The present inventors have developed a two-stage process and system for bark conversion into biofuel. According to a preferred embodiment the bark is birch bark. First, in a preferred embodiment, milled birch bark is treated with MeOH-H<NUM>O-Et<NUM>N solvent system in a reactor or the like. The obtained mixture, containing bark solubilized in the solvent system and solid bark residue is filtered. The filtrate may be returned into the same reactor and thus play the role of the next portion of solvent system. The solid bark residue obtained in the filtration is discarded. The filtrate consists mainly of gum, comprising at least partly depolymerized suberin and other substances of bark ("depolymerized bark") dissolved in the solvent system.

After several runs of using the gum solution solubilized in the solvent system as solvent for new portions of milled bark, the solvent system MeOH-H<NUM>O-Et<NUM>N is recycled by evaporation and returned to be used again as a pure solvent system consisting of MeOH, H<NUM>O and Et<NUM>N. As a result of the evaporation a semi-solid gum is obtained. This semi-solid gum is subjected to hydrotreatment by hydrodeoxygenation, for example in the presence of a suitable hydrodeoxygenation catalyst, such as Pt/TiO<NUM>/Mo<NUM>, and H<NUM> gas or HCOOH. This second stage of the process leads to a reaction mixture comprising a variety of different hydrocarbon oils in the diesel-range that may be separated from each other through distillation. The reaction mixture resulting upon hydrotreatment is then distilled in order to obtain different hydrocarbons boiling at different temperatures.

The inventors of the present invention found that certain amines work surprisingly well in the invention. Ammonia, primary and secondary amines cannot be used because they form amides when reacting with esters.

For the purpose described herein, the simple tertiary aliphatic amine Et<NUM>N (pKa <NUM>) was found to be a surprisingly good choice as a component of the solvent system. In the presence of Et<NUM>N in organosolv pulping conditions, suberin was found to undergo alkaline hydrolysis (cf. After the solubilization of the substances of bark in the solvent system has been accomplished, Et<NUM>N can be easily removed by distillation (bp <NUM>) together with other components of the solvent system.

Mixtures of alcohols with water are suitable for the extraction of nonpolar components of biomass, such as lignin and suberin. Mixtures are more efficient than alcohol or water alone. MeOH can be recycled easier than any other alcohol due to its low boiling point (<NUM>).

Solubilization of the bark with the MeOH-H<NUM>O-Et<NUM>N solvent system was optimized with regard to minimization of the mass of solid bark residue. The degrees of solubilization (%) are reported in relation to the mass of extractive-free bark (content of EtOH-extractives plus moisture is <NUM>%). As a starting point, we treated the bark with MeOH-H<NUM>O (<NUM>:<NUM> v/v or <NUM> vol. % H<NUM>O) at <NUM> for <NUM> in absence of Et<NUM>N, in which conditions only <NUM>% were solubilized (<FIG>). Addition of <NUM> vol. % of Et<NUM>N improved the result toward <NUM>%. Increase of Et<NUM>N concentration to <NUM> vol. % led to <NUM>% solubilization. Further increase (<NUM> vol. %) caused a decline of the solubilization degree (<NUM>%).

Using the optimized Et<NUM>N concentration (<NUM> vol. %), we explored the role of water as component of the solvent system. If no water was added (i.e., Et<NUM>N-MeOH mixture was used as the solvent system), the solubilization degree was lower than in case of MeOH-H<NUM>O <NUM>:<NUM> v/v, but still significant (<NUM>%). Addition of <NUM> vol. % of water did not affect this result (<NUM>%). When water became the major component with concentration of <NUM> vol. %, the degree of solubilization hits the maximum (<NUM>%). A H<NUM>O-Et<NUM>N solvent system without MeOH led to a small decline of the result (<NUM>%) and was more difficult to handle during filtration. Therefore, if the content of water is higher than <NUM> vol. % its change does not affect the process. We decided to use <NUM> vol. % of water because presence of MeOH makes recycling of the solvent system as well as other operations such as filtration easier.

We also investigated the effect of temperature. When the process was carried out for <NUM> with the optimized solvent system (MeOH-H<NUM>O <NUM>:<NUM>,<NUM> vol. % Et<NUM>N) at <NUM>, very poor solubilization was observed (<NUM>%). Increase of the temperature afforded better results: from <NUM>% at <NUM> to <NUM>% at <NUM> and, finally, <NUM>% at <NUM>.

The solvent system was recycled <NUM> times by distillation in vacuum. The recycling and bark solubilization data are presented in Table <NUM> below. Composition of the solvent system after each recycling step was determined by NMR in acetone-d<NUM>. It was observed that concentration of Et<NUM>N slightly decreases at each step, therefore it makes sense to start with higher concentrations of Et<NUM>N (-<NUM>%) when optimizing the process for industry. The recycled solvent was used for solubilization of new samples of bark. The data were in accordance with the obtained during optimization.

Due to the low density of bark packing in a reactor (<NUM>·m-<NUM>), the lower limit of solvent system to bark ratio is V ≈ <NUM>·kg-<NUM>. It was found that until that point, for V = <NUM>, <NUM>, <NUM> and <NUM>·kg-<NUM>, solubilization degree does not depend on this parameter, coming to <NUM>, <NUM>, <NUM> and <NUM>%, respectively. Handling is more convenient with larger ratio V. However, evaporation of solvent system demands a sufficient amount of energy, -<NUM> MJ per liter of the solvent system. Therefore, and also because solvent system recycling by evaporation causes a slight decline of the yield (cf. Table <NUM>), it would be beneficial to decrease V by using the solvent system several times before evaporation, i.e. using the solution for processing each portion of bark like in a looped flow system. Indeed, the presence of bark components in the solution did not affect its ability to solubilize new portions of bark: in three consecutive experiments with V = <NUM>·kg-<NUM>, degrees of solubilization came to <NUM>%, <NUM>%, <NUM>%. Thus, the efficient solvent system to bark ratio was reduced to <NUM>·kg-<NUM>. It must be noticed that filtration slows down significantly with each time as the solution becomes more concentrated and viscous, and it might lead to problems when putting the process on industrial scale.

The gum obtained by "bark depolymerization" (i.e. bark wherein suberin component of bark has been at least partly depolymerized) contains a variety of oligomeric products of suberin and lignin cleavage. MW = <NUM> Da, MN = <NUM> Da (PD = <NUM>), according to SEC data, i.e. an average dissolved molecule is composed of <NUM>-<NUM> monomeric units of lignin and/or suberin. Elemental composition of the material differs insignificantly from the composition of bark, however <NUM>-<NUM>% of residual nitrogen is present. The material is insoluble in hexane, moderately soluble in toluene (<NUM>% of the gum weight) and well soluble in methanol (<NUM>% of the gum weight).

Noteworthy, the gum forms a suspension in tall oil fatty acid (TOFA) at <NUM> which remains practically stable at room temperature, therefore TOFA can be used as a carrier liquid in an industrial process of the gum hydrotreatment. Viscosity of the suspension at room temperature is <NUM>-<NUM> mPa-s for the concentration range <NUM>-<NUM> wt. % and temperature range <NUM>-<NUM>.

HSQC NMR (cf. <FIG>) demonstrated presence of typical structural motifs of suberin. In order to analyze monomeric fatty acids, the gum was subjected to alkaline methanolysis, and the extract was studied by means of GC (<FIG>). A variety of C<NUM>-C<NUM> hydroxylated carboxylic acids and diacids was identified, with the main components being <NUM>-hydroxydocosanoic (<NUM>% TIC as silylated derivatives) and <NUM>,<NUM>-octadec-<NUM>-enedioic (<NUM>%) acids. In addition, ferulic acid (<NUM>%) was detected.

The gum was subjected to hydrodeoxygenation in the presence of Pt/MoO<NUM>/TiO<NUM> catalyst at <NUM>. Simulated distillation study of the obtained bio-oil showed that it contains hydrocarbons within the diesel range. The lightest components have boiling points of <NUM> and <NUM>% of the mixture boils away before <NUM> (<FIG>).

2D GC technique allowed to study different types of components of the mixture (<FIG>). The most abundant molecules are C<NUM>-C<NUM> hydrocarbons. In the natural suberin, only fatty acids with even carbon atom numbers are present. Therefore, hydrocarbons with uneven chain length emerge due to cracking and/or decarboxylation processes. Higher aromatic compounds such as naphthalenes (<NUM> wt. %) are probably also the products of cracking since their carbon atom numbers are generally lower than the ones of other observed hydrocarbons (average <NUM> versus <NUM> for the whole mixture). Unsaturated and monounsaturated hydrocarbons account for up to <NUM> wt. %, however, due to the presence of aromatic compounds the average number of double bonds and/or cycles per molecule for the whole mixture is <NUM> and H/C ratio is <NUM>.

Yield of the obtained bio-oil is <NUM>% of initial bark weight (<NUM>% of extractive-free bark). Carbon content in the bio-oil is <NUM>%, as calculated through 2D GC data, and the carbon yield (the ratio of carbon which has been transferred from bark to the product) is <NUM>%. Various types of bio-oil components and their content are presented in Table <NUM>.

The bark of birch (Betula Pendula) was analysed.

A sample of bark was extracted with EtOH in Soxhlet extractor for <NUM> and then dried in air at <NUM> for <NUM>. Weight loss: <NUM>% of bark weight. Mass of the EtOH-solubilized material: <NUM>% of bark weight.

Extractive-free bark sample (<NUM>) was treated with <NUM>% MeONa solution in MeOH (<NUM>) under reflux for <NUM>. The solution was centrifugated and the residue was washed with MeOH and water. Centrifugation and washing were repeated until the pH became neutral. Solid residue was dried (<NUM>, <NUM>% of extractive-free bark, <NUM>% of total). Solution was acidified to pH <NUM> with H<NUM>SO<NUM> and extracted with DCM (<NUM> × <NUM>). The organic fraction was dried, filtered and concentrated to afford suberin oil (<NUM>, <NUM>% of extractive-free bark, <NUM>% of total).

The solid residue which remained after alkaline methanolysis (extractive-free desuberized bark) was dried in air at <NUM> for <NUM>. A sample (<NUM>) was treated with <NUM>% aqueous H<NUM>SO<NUM> (<NUM>) at <NUM> for <NUM>. Then the mixture was diluted with water (<NUM>) and refluxed for <NUM>. After cooling to rt, the mixture was filtered through paper filter. The filter was washed with water until a neutral pH was reached, and the residue was dried in air at <NUM> for <NUM> to afford acid-insoluble lignin (<NUM>, <NUM>% of extractive-free bark, <NUM>% of total).

A sample of untreated bark (<NUM>) was placed into a stainless-steel reactor together with <NUM>% aqueous KOH (<NUM>) and nitrobenzene (<NUM>). The reactor was heated with stirring at <NUM> for <NUM>. After cooling, the mixture was acidified with HCl to pH <NUM> and extracted with DCM (3x5 mL). Combined organic fraction was dried with Na<NUM>SO<NUM>, diluted with Et<NUM>O and subjected to GC-MS. Method: Syringol and guaiacol units were detected as syringaldehyde and vanillin. Though the reproducibility of the method is low, syringol to guaiacol ratio was determined to be <NUM>-<NUM> based on three runs.

Analysis for carbohydrates was carried out according to previously published procedure; <NPL>. No carbohydrates were detected.

The results of the analysis of composition of the birch bark feedstock used are presented in Table <NUM> below.

The direct elemental analysis by combustion was performed on the birch bark feed stock. The following results were obtained: C, <NUM>%; H, <NUM>%; N, <NUM>%; O, <NUM>%.

Grinded birch bark (~<NUM> particle size, <NUM>) was placed into a stainless-steel reactor (internal volume <NUM>) together with a mixture of triethylamine (<NUM>), methanol (<NUM>) and water (<NUM>) and a magnetic stirring bar. The reactor was heated at <NUM> in an oil bath for <NUM> hours with <NUM> rpm stirring. After cooling, the mixture was filtered through paper filter. The solid residue was dried at <NUM> for <NUM> hours and weighted (<NUM>, <NUM>% of initial bark weight). The filtrate was distilled to recover the solvent system. The residual brown gum was dried in air at <NUM> or <NUM> for <NUM> hours (<NUM>, <NUM>% of initial bark weight) and subjected to analyses.

The procedure was optimized with regard to minimization of weight of the solid residue. Each experiment was repeated at least twice to address possible issues of samples' heterogeneity. The experimental data of these experiments are presented in Table <NUM> below. For graphical representation of the results, see <FIG>.

<NUM> of the gum was suspended in <NUM> of CDCl<NUM> at <NUM>, the mixture was cooled to room temperature without filtration and subjected to NMR analysis. The spectra were recorded with a Bruker <NUM> (<NUM>) spectrometer as solutions in CDCl<NUM>. Chemical shifts are expressed in parts per million (ppm, δ) and are referenced to CHCl<NUM> (δ = <NUM> ppm) as an internal standard. <NUM>C NMR spectra were recorded as solutions in CDCl<NUM> with complete proton decoupling. Chemical shifts are expressed in parts per million (ppm, δ) and are referenced to CDCl<NUM> (δ = <NUM> ppm) as an internal standard. 2D-NMR spectra were acquired on an Agilent <NUM>-MR spectrometer. The standard Agilent implementations of gHSQCAD experiments were used. The results of the NMR spectroscopy analysis are presented in <FIG>.

Size exclusion chromatography (SEC) was performed using a YL <NUM> HPLC-GPC system with three Styragel columns (HR <NUM>, HR <NUM>, and HR <NUM>, <NUM>×<NUM> each) connected in series (flow rate: <NUM>·min-<NUM>; injection volume: <NUM>µL; THF), a UV detector (<NUM>), and an auto-sampler. The system was calibrated using ReadyCal-Kit poly(styrene) (MP <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> Da). Samples were dissolved in THF to a concentration of <NUM>·L-<NUM>.

The detected oligomers possess the following properties:.

Solubility of the gum in various organic solvents was measured as follows. The gum (<NUM>) was treated with a solvent (<NUM>) at <NUM>-<NUM> for <NUM>, the solution was cooled <NUM> and filtered through a <NUM> syringe filter. Mass of the filtrate was measured. Then the filtrate was concentrated in vacuum and the residue dried in air at <NUM> for <NUM> hours. Mass of the residue was measured. The results of the tests on solubility of the bark gum in various solvents are presented in Table <NUM> below.

Tall oil is a naturally occurring liquid mixture of fatty acids and rosins which has been demonstrated to be useful carrier liquid for hydrotreatment of biomass derivatives. For this purpose, viscosity of the mixture is crucial. The gum forms a suspension in tall oil fatty acids mixture (TOFA) at <NUM> which remains practically stable at room temperature. Viscosity of the suspension was measured with Anton Paar Rheolab QC rotational rheometer with a CC10 sensor (stirring rates <NUM> to <NUM>-<NUM>). The viscosity data of the gum suspension in TOFA at different temperatures and concentrations is given in Table <NUM>.

1D GC was used for analysis of monomeric composition of the gum. A sample of the gum (<NUM>) was refluxed with <NUM>% KOH/MeOH (<NUM>) for <NUM>. The mixture was acidified with HCl, diluted with water and extracted with CHCl<NUM> (<NUM> × <NUM>). Combined organic phases were dried with Na<NUM>SO<NUM>, filtered and concentrated. A sample of the residue (<NUM>-<NUM>) was dissolved in THF (<NUM>) and silylated with bis(trimethylsilyl)acetamide (<NUM>µL) in the presence of pyridine (<NUM>µL). The solution was subjected to GC. GC measurements were performed on a Shimadzu Shimadzu GC-MS-QP2020 equipped with a HP-<NUM> capillary column (<NUM> × <NUM> × <NUM>) and an MS detector. Compounds were identified by comparing the observed fragmentation patterns to literature data. MS spectra of each identified derivative are given in <FIG>.

Claim 1:
A process for at least partly dissolving in a solvent system substances of bark, which bark contains a suberin component, and for at least partly depolymerising the suberin component, comprising the following steps:
providing bark;
providing a solvent system comprising water, and a base selected from tertiary aliphatic amines;
treating the bark with the solvent system by subjecting the bark to the solvent system at a temperature of at least <NUM>, thereby obtaining a composition containing at least partly dissolved substances of bark, of which substances the suberin component is at least partly depolymerised.