FI73013B - FOERFARANDE FOER DELIGNIFIERING AV RAOMATERIAL INNEHAOLLANDE LIGNOCELLULOSA. - Google Patents

Description

1 73013

METHOD FOR THE DELJGNI FIXING OF LIGNOCELLULOSIC RAW MATERIAL - FÖRFARANDE FÖR DELIGNIFIERING AV RAMATE-RIAL INNEHÄLLANDE LIGNOCELLULOSA

The invention relates to a process for delignifying a lignocellulosic feedstock, wherein the feedstock is heat-treated with a chemical containing a tetrahydrofurfuryl alcohol compound and possibly water. Ter-5 by which the tetrahydrofurfuryl compound is meant in this context tetrahydrofurfuryl alcohol, its derivatives or mixtures thereof.

In chemical delignification methods commonly used today, e.g. the sulphate-10 or sulphite process, the fibrous material is separated from the wood by dissolving the lignin in a cooking solution consisting of inorganic cooking chemicals. The process is carried out at a relatively high pressure, of the order of e.g.

6-10 atm, and at a relatively high temperature, a mouth-15 rose order e.g. 160-180 ° C.

The disadvantages of these known methods are the unpleasant odor and the environmental disadvantages of the waste materials. In addition, the recovery and reuse of chemicals requires the incineration of waste liquor 20 as well as a complex regeneration process. Furthermore, in connection with the pulp cooking of wood, only about half of the wood can be utilized in product form.

Recently, increasing attention has been paid to alternative delignification methods to avoid the above-mentioned drawbacks. In particular, the so-called organosolv methods have gained particular interest. In these, the aim is to dissolve the lignin in the organic solvent without damaging the cellulosic fibers, whereby the lignin and any other dissolved components can be recovered after the solvent has been separated and regenerated.

2 7301 3

Lignin solvents are known, for example, from Lignins, Occurrence, Formation, Structure and Reactions, Sarkanen, Ludwig, Willey Interscience, N.Y., 1971. However, the lignin solvents known from said publication do not meet the requirements for a solvent suitable for a technical process.

A solvent suitable for the technical process is required to dissolve the lignin also in the presence of water, since the lignocellulosic raw material always contains more or less moisture.

The solvent must therefore be water-soluble. It is further important for the implementation of the process that the solvent be non-toxic. Furthermore, the solvent must not react with lignin or other solutes, since the reaction makes regeneration difficult or impossible.

In technical experiments, various alcohols have been found to dissolve some lignin at high temperatures. Light alcohols, methanol, and ethanol, whose volatility, however, present difficulties in the technical implementation of solvent recovery and recycling appear to work best. Furthermore, all alcohol-based soups require relatively high temperatures, 160-220 ° C, as well as the use of an acid catalyst-25 pathway. The use of acid catalysts lowers the quality of the fibrous material produced; the kappa numbers obtained are high and the yield low.

Chem & Eng News, May 31, 1982 discloses a process using phenol as a lignin solvent and carried out under normal pressure. This method has largely achieved the goals set for organosolv soup. However, for large scale implementation of the method, the toxicity of phenol may cause difficulties.

35 Furthermore, a delignification process using tetrahydrofurfuryl alcohol as a solubilizer for lignin 3 7301 3 is known from Soviet patent publication 672 260. This process requires a cooking temperature of the order of 150-160 ° C and the use of an acid-base catalyst. Furthermore, the process is carried out under pressure in the same way as a conventional pulp cooking process. The experimental results obtained are unsatisfactory in terms of yield and lignin content of the product.

It is an object of the present invention to obviate the above drawbacks. It is a further object of the invention to provide a new method for delignifying a lignosel-10 lulose-containing raw material under more reasonable conditions, i.e. at a lower temperature and a lower pressure. In particular, it is an object of the invention to provide a process of the type in which the yield of the pulp to be produced is higher than before and the lignin content, i. lower number of pieces than before.

It is a further object of the invention to provide a novel delignification process by which the lignin contained in the lignocellulosic feedstock and any other dissolved components can be further utilized after solvent separation and / or regeneration.

It is a further object of the invention to provide a new delignification method suitable for de-lignification in the presence of water, e.g. for delignification of moist and wet wood.

It is a further object of the invention to provide a novel method of delignification which does not cause, to the same extent as previously known processes, an unpleasant odor and other environmental disadvantages.

It is a further object of the invention to provide a process of the type in which the solvent used is non-toxic and does not react with dissolved wood materials.

With regard to the features characteristic of the invention, reference is made to the claims.

4 7301 3

The invention is based on a new use of tetrahydrofufuryl alcohol previously known in connection with delignification. According to the invention, it has surprisingly been found that the best cooking results when using tetrahydrofurfuryl-5 alcohol are obtained at considerably lower temperatures and pressures. In fact, the delignifying effect of tetrahydrofurfuryl alcohol is more effective at relatively low temperatures, atmospheric pressure conditions, than at higher temperatures, where hydrolysis of hemicellulose causes undesirable side reactions that complicate solvent recovery and reduce solvent recovery.

The process according to the invention makes it possible to carry out the delignification at a low temperature, even below 100 ° C, so that the course of the reaction can be well controlled so that no adverse side reactions occur.

The delignification carried out mainly at normal pressure according to the invention offers considerable technical and economic advantages, the most important of which are the simplification of the process equipment and the higher yield obtained from the raw materials sold as raw materials. The method makes it possible to separate the main components of the lignocellulosic material: cellulose, hemicellulose and lignin into useful end products.

The process does not require drying or other expensive pretreatment of the wood raw material like many other organosolv methods.

Due to the low cooking temperature, the energy consumption of the process is low.

The tetrahydrofurfuryl alcohol used as a solvent in the process, its derivatives and / or mixtures thereof can be reused after separation and / or regeneration and can be prepared from pentosans dissolved in the cooking solution to replace technical solvent losses.

A further advantage of the process according to the invention is the safety of the solvent used from the point of view of the environment in comparison with the compounds used in other organosolv processes, such as, for example, phenol.

Example 1 illustrates some preferred embodiments of the method, and Example 2 illustrates a prior art method.

Example 1 About 20 g of lignocellulosic material from various sources was mixed with 200 g of THFA (tetrahydrofurfuryl alcohol) or aqueous THFA. The catalyst was added to the solution, and the mixture was maintained at the dissolution temperature for 1 to 6 hours. The pulp obtained after treatment was decomposed and washed. From the obtained mass, the number of pieces was determined, which describes the amount of lignin remaining in the mass. The results are shown in Table 1.

20 Experiment with lignocell- Treatment Mas- Pulp no. loose THFA catalyst pretty warm kappa raw. substance pit. h pöt. yield substance%% to% 1 birch, wood 50 HCl 2 4 100 40 40 25 scattered flour 2 birch, wood chips 80 HCl 1 4 104 49 3 3 birch, wood chips 80 HCl 0,25 4 104 49 39 4 pine, wood chips 80 HCl 1 4 104 45 29 5 spruce, chips 80 HCl 1 4 104 4 5 1 5 30 6 birch, chips 80 H2SC> 4 1 4 104 50 38 7 birch, Sahaj. 80 HCl 0,5 4 104 4 2 1 9 8 birch, wood chips 40 H2SO4 5 4 98 40 40 9 spruce, wood chips 80 HCl 1 6 50 50 39 10 birch wood, wood chips 100 HCl 1 1 120 46 35 35 11 birch wood, wood chips 80 CH3COOH 1 4 103 55 50 12 straw * 80 HCl 1 4 104 38 20 13 bagasse 80 HCl 1 4 104 35 16 7301 3 6

Example 2 50 g of birch chips, 240 g of THFA, 34 g of water and 9 g of concentrated hydrochloric acid were heated in an autoclave to 160 ° C and maintained at this temperature for 2 hours. The pressure in the autoclave was 6 bar. After cooling and depressurization, the completely decomposed pulp in which the fibrous structure of the cellulose was barely detectable was removed from the autoclave.

In this specification and claims, the concentrations are expressed as percentages by weight of the of the total number of substances or solutions.

The invention is not limited to the embodiments shown, but can be varied and modified within the scope of the appended claims. In this case, it should be noted that the water of the chemical containing the tetrahydrofurfuryl alcohol compound and water may be derived from a delignifiable raw material such as moist wood, or water may be added with or in addition to the tetrahydrofurfuryl alcohol compound if desired. Further, as described in the embodiment, the delignification 20 can also be performed with a tetrahydrofurfuryl alcohol compound that does not contain water, i.e., the water contained in the chemical is derived from the raw material to be delignified.

25 30 35

Claims (7)

A method for delignifying a lignocellulosic feedstock, wherein the feedstock is heat treated with a chemical containing a tetrahydrofurfuryl alcohol compound and water, characterized in that the heat treatment is performed at a temperature of 50 to 120 ° C. Process according to Claim 1, characterized in that the heat treatment is carried out at a temperature of 95 to 115 ° C, preferably about 104 ° C. Process according to Claim 1 or 2, characterized in that the heat treatment is carried out with a chemical containing 0 to 60% by weight of water, preferably about 10 to 30% by weight. Process according to one of Claims 1 to 3, characterized in that the treatment time is 1 to 6 hours, preferably 2 to 3 hours. Process according to one of Claims 1 to 3, characterized in that the chemical contains 0 to 2.5% by weight, preferably 0.5 to 2% by weight, of mineral or organic acid as catalyst. Process according to one of Claims 1 to 5, characterized in that the tetrahydrofurfuryl alcohol compound is separated from the resulting solution after delignification for regeneration and / or reuse. Method according to one of Claims 1 to 6, characterized in that the treatment is carried out at a pressure of 1 to 2 atm, preferably 1 atm.