FI129154B - Porous, formable material and method for manufacturing the same - Google Patents

Abstract

The invention relates to a porous molding material and to a method for its production. The process uses a lignocellulosic starting material to form a lignin-containing mixture from the fractions from biomass fractionation, which is treated to produce a porous body. In the method, the material is foamed, shaped, heat treated, carbonized and activated. The available charred and activated part is suitable for e.g. filler, filter and catalyst filler.

Description

PORRY MOLDING MATERIAL AND METHOD

TECHNICAL FIELD The present invention relates to porous moldable biomaterial-based materials, their preparation and their use. In particular, the invention relates to a method according to the preamble of claim 1 - for obtaining a porous shaped body and to a product obtainable by such a method. Background Art - So-called porous carbon is found to be used in many different applications, such as thermal insulation (even at very high temperatures), various filters and catalysis. In catalytic reactions, porous carbonized materials are used in particular as catalyst supports due to their high specific surface area.

Traditionally, porous carbon materials are mainly made by carbonizing synthetic resin foams such as polyurethane and phenolic resin foams. Such materials S are non-ecological and expensive to manufacture. Thus, the research aims to find O alternative materials for these synthetics. It is known e.g. use of lignin 2 25 - to replace phenols in polyurethane foam. i In the past, efforts have been made to prepare various bio-based foam products mainly from 3 pure biomaterial-based starting materials, such as tannin, lignin and furfural alcohol, = but the use of impure starting materials has also been studied. The prior art in this regard is represented, for example, by US3894848, which discloses the preparation of a porous molding material from an aqueous solution of lignin. The process comprises foaming and heat treatment of the starting material in a mold and carbonization of the porous material thus obtained.

The articles “Tannin based foams and its derived carbon foams” (Tondi, G. et al, 2010) and “Chemistry, morphology, microtomography and activation of natural and carbonized tannin foams for different applications” (Pizzi, A., 2012) describe 95% pure tannin foams and their carbonation and possible activation.

WO2005016818 describes a process for preparing a carbon foam from a metal salt of a lignosulfonate.

In the process, flotation and carbonization of the starting material are performed simultaneously in an oxygen-free atmosphere, at a pressure of more than 100 psi and at a temperature of more than 250 ° C.

It is also known to make activated carbon from carbon materials, the operation of which is based on adsorption, in which case the activated carbon acts as an adsorbent, binding to its surface certain molecules from either a gaseous or a liquid substance.

Typically, depending on the pore size and the size of the molecules, the molecules are trapped in the pores of the foamed carbon material simply because of their physical size, in which case the porous material already functions as such. as a target.

A significant feature of activated carbon is its particularly porous structure, which - provides a large specific surface area and at the same time improves the filterable properties of activated carbon. = The effective surface area of activated carbon varies greatly depending on the degree of carbon activation N and the raw material used to make the activated carbon.

The aim is to use S 25 as the raw material - to choose a material that gives the best 2 properties of activated carbon for future use.

The most commonly used activated carbon raw materials are wood, sawdust, peat, E coconut shells, coal and crude oil waste.

Typically, the selected feedstock ® is crushed and then carbonized at a temperature of about 800-1000 ° C.

During carbonization 5, most of the hydrocarbon and some of the carbon are removed, thereby increasing the surface area of the carbon. > 30 - Activation of carbon can improve the adsorption capacity of carbon organic matter by increasing pore size and diameter.

During activation, various substances are removed from the carbon pores, leaving empty spaces in the structure, i.e. the volume of the pores increases.

The substances removed as a result of the activation also form completely new pores in the carbon. The specific surface area of the activated carbon is typically 500-1500 m 2 / g. When choosing a raw material, it is important to take into account the desired goal of the final product - particle size, pore structure, total surface area and empty space between the ingredients and, of course, the price of the raw material. Typically, the activated carbon is either in a fine powder or in granular form, but foamed activated carbon has also been prepared.

It is also known to produce activated carbon from biomass. Such have been described e.g. in CN1070021486 and US4552863. CN1070021486 discloses a process for producing activated carbon from biomass by foaming, calcining and finally activating the carbonized foam using a gas. In the process of US4552863, activated carbon is produced using wood as a carbon source. The general state of the art with respect to activated carbon materials is also described e.g. CN 105293490, US2016031713, US6024899 and Saha D. et al. (Studies on supercapacitor electrode material from activated lignin-derived mesoporous carbon, 2014). US3894878 also describes a process for preparing a porous material from a lignin-containing starting material.

N N Heat-treated foams alone have often been found to be quite brittle. S 25 - In addition to other properties, carbonization or activation can also improve 2 the mechanical resistance of the porous material. x a o There is still room for improvement in the properties of porous materials, and in particular in formability, and in the starting materials used. In particular, the use of ecological feedstocks> 30 needs to be intensified and the utilization of industrial by - products needs to be further increased. Also, no starting material has succeeded in optimizing all the advantageous properties simultaneously with environmental friendliness and affordability.

The desired properties are relatively low density, mechanical strength and high thermal conductivity, which is usually the result of at least a partially organized crystal structure.

General Description of the Invention It is an object of the present invention to provide a novel method for producing porous moldable materials from bio-based starting materials. In particular, it is intended to provide a process for the preparation of carbon foams using - low-cost starting materials which, however, have the necessary physical and chemical properties for use.

In particular, it is an object of the invention to provide a process for the preparation of carbon foams from a lignocellulosic starting material.

The invention is based on the finding that by treating a lignocellulosic starting material with the process according to the invention, a bioavoidable porous shaped body can be formed which is carbonized and activated throughout.

- In the process according to the invention, the mixture containing a liquid medium is formed from a lignin-containing fraction obtained from the fractionation of biomass, to which other fractions formed as a result of the fractionation of biomass are optionally added.

= The formed mixture is foamed and shaped in a mold to a predetermined shape. The shaped foam thus obtained N is further subjected to a heat treatment, after which it is carbonized and S 25 - finally activated.

O E As shown, foamed biomass-based bodies are provided which can be used, for example, in various cleaning applications, such as the cleaning or purification of gases and liquids, as a filler or as a catalyst filler.

> 30 - More specifically, the invention is characterized by what is set out in the characterizing parts of the independent claims.

The invention provides considerable advantages. Thus, the method provides self-supporting monolithic, activated, porous structures. In particular, porous shaped bodies are obtained which are carbonized and activated throughout. The carbonized and activated porous body of the invention has 5 - advantageous properties such as low electrical conductivity, low thermal conductivity and low density. These features can also be customized in a variety of ways. In the case of insulators, for example, poor thermal conductivity can be achieved by reducing the density, and the electrical conductivity can be adjusted, for example, by adding metals to the foam that conduct electricity better. Electrical conductivity is also affected - for example, the temperature used in the heat treatment, heat treatment at high temperatures typically improves the electrical conductivity. Thus, the shaped body according to the invention has a wide range of applications.

Preferably, the flotation according to the invention takes place at normal pressure and room temperature. However, the flotation can also be carried out under reduced or overpressure, for example at an absolute pressure of 0.1 to 10 bar. When the mixture is foamed without external heating, the foaming can be better controlled and uniform foam bodies are obtained.

- The invention can be used as a starting material for a very wide range of lignocellulose-based raw materials, such as various plants and their parts, by-products of various fractionation processes, as well as peat and biogas plant digests and other partially biodegraded or treated materials. The bio-based raw materials N used in the invention reduce the need for fossil raw materials and reduce the carbon footprint of the product S 25. Thus, in the process according to the invention it is possible This also makes use of the side fractions of the fractionation process.

2 lo The production method according to the invention also has the advantage of environmental friendliness,> 30 - simple technology and low energy consumption. Energy consumption can be reduced by utilizing the energy of the gas streams used in the different process steps by recovering them and utilizing them, for example, in preheating. In addition, volatile components used for flotation can be recycled by condensation and reuse. The volatile fractions generated in the carbonization step can also be utilized as a source of energy or heat can be recovered from them by condensation, in which case these liquid fractions can also be utilized in other processes. Non-condensable gases can be burned and the energy thus produced can be utilized, for example, in process, heating or electricity generation. The porous material according to the invention also has the advantage of being recyclable and reusable. The porous material produced can be regenerated directly - by heating or alternatively by crushing, after which it can be used as a raw material for a new foam. Finally, the carbonized material can be used as a soil improver, allowing the carbon (CO; negative) it contains to be stored in the soil for a long time, or alternatively it can be burned to produce green energy.

In the following, preferred embodiments of the invention will be examined in more detail with reference to the accompanying drawing. The drawing shows a simplified schematic diagram of the steps of the method according to one embodiment. Drawings Fig. 1 is a block diagram showing the steps of a method according to one embodiment.

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The present invention relates to a porous moldable material and a method for producing the same.

LO co N 30 - The products to be manufactured are hereinafter referred to as 'body' and 'foam body' as synonyms for each other. It is a three-dimensional body that is porous. After flotation, the porous material comprises mainly macroporous. Typically, the smallest dimension of the pores is then at least 0.01 mm. As a result of activation, a large number of micropores and mesopores are formed in the body. Preferably, the body is porous throughout, which means that the porous structure - extends from inside the body to its surface. Preferably, the porous body, i.e. the foam body, is permeable to gases. The bodies are “monolithic”, which in this context means that their body structure consists of the same substance throughout, i.e. the body is “one substance”.

The pieces are typically mechanically strong and it is possible to make self-supporting pieces from the present material. “Self-supporting” means that they can be used to form products, such as filters and similar bodies, that do not require a separate body layer or structure.

The process according to one embodiment is shown in Figure 1. In the first step of the process (reference number 2 in Figure 1), a mixture containing a liquid medium is formed from a lignin-containing fraction obtained from biomass fractionation 1. Typically, the lignin-containing fraction is derived from biomass, such as wood or annual or perennial plants. The fraction is obtained, for example, by extracting the biomass with aqueous solutions, for example by hot water extraction or pressurized hot water extraction or by conventional S 25 chemical pulp digestion. Aqueous solutions preferably contain components which promote the dissolution of lignin 2, such as alkalis, e.g. alkali metal or alkaline earth metal E hydroxides, carbonates, sulphides or mixtures thereof. Extraction solutions may also contain peroxides as well as organic compounds such as perforic acid or Caron's salt. Extraction can also be performed with organic or ionic solvents. > 30 The liquid medium in the mixture acts as a foamer in the mixture. In one embodiment, the liquid medium is water. According to another embodiment, the liquid medium may be, for example, an organic solution such as an alcohol or an ionic solution. The liquid medium may also be a mixture of several different liquids. By using a liquid medium with a low boiling point, the energy required to dry the foam can be reduced.

In one embodiment, the liquid medium used for flotation can be recovered and recycled for reuse. The lignin may be either untreated or treated or a mixture thereof. Thus - lignin can be in any form, such as alkali lignin, thiol form or metal salt of lignosulfonate. According to one embodiment, other fractions from biomass fractionation 1 are also added to the lignin-containing mixture. These fractions may or may not contain - lignin. Typically, the fractions to be added contain, for example, organic components from biomass, such as extractants, furfural or tannin, or monomeric, oligomeric or polymeric saccharides derived from cellulose or hemicellulose. - In addition, the fractions to be added may be pure or unpurified. The proportion of each such fraction in the solids of the mixture to be foamed may be, for example, about 0.1 to 25% by weight. Thus, in the present invention, it is possible to efficiently utilize the N different side fractions of the fractionation process. S 25 2 In one embodiment, the mixture of biomass fractions contains at least E 1% by weight of lignin, preferably at least 5% by weight of lignin, more preferably 10-80% by weight of lignin, for example 20-50% by weight of lignin based on the dry weight of the mixture. 5> 30 - In one embodiment, the mixture formed from the fractions contains at least 1% by weight of lignin, preferably at least 5% by weight of lignin, more preferably 10-75% by weight of lignin, for example 30-50% by weight of lignin based on the total weight of the mixture.

According to one embodiment, the mixture formed contains 0.1 to 70% by weight, preferably 1 to 50% by weight, more preferably 5 to 30% by weight, for example about 10% by weight, of liquid medium, based on the total weight of the mixture.

Components can also be added to the mixture, which, for example, modify the properties of the final product according to the application. In one embodiment, these components are added prior to flotation. According to another embodiment, these components can also be added at any other stage of the process, such as before drying or carbonization, or in several different stages. In one application, a substance or substances belonging to one or more of the following groups are added to the mixture: - a substance which modifies the mechanical properties of the articles to be manufactured (especially their strength agents), a fire modifier, a catalyst or an insecticide. = Furthermore, it is possible to add various fillers, wetting agents and stabilizers to the mixture. = The total amounts of the above substances and components are typically about 0.01 to N 25% by weight, especially about 0.1 to 10% by weight based on the dry weight of the starting material. S 25 2 The mixture formed in the next step 3 of the method is foamed and formed in a mold E into a predetermined shape. 3 lo In one embodiment, the mixture formed from the fractions> 30 - obtained as a result of the biomass fractionation is foamed before it is fed into the mold, whereby the mold is carefully filled and the foamed body is made exactly mold-shaped. According to another embodiment, the mixture is foamed only in the mold. The mold may be heated to promote solidification of the foam, as described below.

The mixture can be foamed by any generally known flotation method, such as heating, mechanical stirring, a blowing gas process, or a brine process.

Preferably, the mixture is foamed by mechanical agitation or chemically.

For example, sodium carbonate or potassium carbonate can be used in chemical foaming, which decomposes to produce carbon dioxide and whose alkali moiety also acts as an activation aid.

The flotation can be performed, for example, in a mixing tank.

To promote foaming, a blowing agent such as a surfactant such as polysorbate may be added to the mixture, e.g. about 0.1-10% by weight of the dry matter of the mixture.

According to a preferred embodiment, the flotation is carried out at normal pressure or low overpressure, for example at an absolute pressure of 1.1 to 10 bar.

The flotation temperature is - preferably above 20 ° C but below 100 ° C.

The reaction is exothermic, i.e. without heating the flotation is more controllable and the shaping of the part is easier.

With the help of the mold, the foamed product acquires a clear shape in three dimensions, which is in no way delimited.

It can be, for example, a cube, a cone, a cylinder or a ball.

According to a preferred embodiment, the mold must be closed.

However, the mold can also be open.

The shaped porous material prepared as described above is subjected to = heat treatment 4. & S 25 The formed porous material is heat treated 4 at a mild temperature to strengthen the foam 2.

In a preferred embodiment, the heat treatment is performed with the foam still E in the mold. 2 lo However, the heat treatment can also be performed in a separate oven. > 30 The heat treatment is carried out by heating the foamed mixture to a suitable temperature and maintaining it at this temperature for a sufficient time, such as 0.1 to 24 hours, for example 0.5 to 12 hours, depending on the composition of the mixture formed from the fractions. Preferably, the heat treatment takes place at a temperature below 250 ° C, for example at a temperature below about 200 PC, most preferably at a temperature of about 101-195 ° C. Usually the heat treatment is carried out at normal atmospheric pressure (at a pressure of about 1 bar), but it is of course also possible to carry it out at an elevated pressure, e.g. at an absolute pressure of about 1.1-10 bar. The temperature of the foam should be raised at a sufficiently low rate to allow the material to heat evenly. According to one embodiment, a suitable heating rate is occasionally 1-120 ° C / minute, in particular the temperature is raised in the heat treatment vessel to about 5-50 ° C / minute, for example about 10-30 / * C / minute. According to one embodiment, the temperature of the heat-treated porous material is preferably lowered to a temperature of about 50-100 ° C. The lowering of the temperature is carried out - preferably so slowly that there are no cracks in the carbon foam due to thermal stress. A suitable cooling rate is about 1-120 ° C / minute, especially the temperature is lowered in the heat treatment vessel to about 5-50 ° C / minute, for example about 10-30 ° C / minute. This is typically done if the shaped porous body is removed from the mold at this point and the following method steps are performed without the mold. Typically, the porous body is also held in the mold during carbonization and activation, if the mold is such that the gases released during carbonization and activation can pass freely therein.

N N In another, preferred embodiment, the heat-treated porous material is taken S 25 - directly, without substantially lowering its temperature, to the next process step, where it 2 is charred and activated. x a o According to a preferred embodiment, the carbonization 5 after the heat treatment takes place in 5 inert gas phases at a temperature above 500 ° C, such as 500-1500 ° C,> 30 - preferably at a temperature of about 800-1000 ° C. The temperature of the foam is slowly raised to the carbonation temperature. A suitable heating rate is about 1-120 ° C / minute, especially the temperature in the heat treatment vessel is raised to about 5-50 ° C / minute, for example about 10-

30 / * C / minute. The inert gas phase used in carbonization may contain any gases that are substantially inert under the conditions of carbonization. Examples of such gases are nitrogen, helium, carbon dioxide and argon and mixtures thereof. Carburization can be performed in a sealable reactor or furnace. Typically, such a reactor or furnace operates at near atmospheric pressure or at low overpressure.

- According to one embodiment, even after carbonization, the temperature of the body must decrease slowly enough so that no cracks occur in the body. A suitable cooling rate is about 5-50 * C / minute.

In another, preferred embodiment, the carbonized porous material is taken directly, without substantially lowering its temperature, to the next possible process step in which it is activated.

According to a preferred embodiment, the carbonized body is activated to further increase its specific surface area. It is by the method of the present invention that the material is first uniformly carbonized and then activated throughout. The carbonization and activation steps of the material also increase the mechanical strength of the porous material.

N N According to one embodiment, the body is chemically activated. Preferably, the S 25 chemical activation occurs by heating the material treated with the activation chemicals to a temperature of 2400-800 ° C. Activation chemicals are used to remove E moisture from the material. As the activating chemicals, for example, alkali salts, phosphoric acid, zinc chloride or sulfuric acid or a mixture thereof can be used.

MN co> 30 - According to another embodiment, the body is physically activated, whereby the carbon is activated by gas at a temperature of about 800-1100 ° C. The gas used can be, for example, water vapor, carbon dioxide or a mixture thereof. As a result of exothermic reactions of activation, hydrogen, carbon monoxide and carbon dioxide are removed from the material. According to a preferred embodiment, the body is activated by steam. In this case, the external adsorption surface of the activated material becomes large and the structure becomes small pores, whereby the foam mainly comprises micropores (pores below 2 nm) and mesopores (pores 2-50 nm), respectively. According to a preferred embodiment, the specific surface area of the body after activation is more than 500 m * / g, which corresponds to the minimum surface area requirement for activated carbon. More preferably, the specific surface area of the body after activation is more than 600 m? / G, for example 750-2500 m * / g. According to a preferred embodiment, the pore volume of the body after activation is more than 0.3 cm '/ g. More preferably, the pore volume of the body after activation is greater than 0.4 cm '/ g, for example 0.5-0.7 cm' / g.

According to one embodiment, the carbonized porous body can be further graphitized before activating the body by heating the body to an even higher temperature of more than 1500 PC. Graphitization can further modify the properties of carbon foam.

According to one embodiment, even after activation, the temperature of the body must decrease slowly enough so that no cracks occur in the body. A suitable cooling rate is = about 5-50 * C / minute. & S 25 - In one embodiment, the porous carbonized body 2 prepared by the method can be washed to reduce any inorganic materials. The washing can be carried out, for example, with water, aqueous acids, bases or some other solution, in particular an aqueous solution. The body can then optionally be dried by well-known drying methods. o 30 According to one embodiment, impregnates can be added to the starting material, i.e. additives which further improve, for example, the adsorption of certain substances on the material during its use. The amount of such substances is typically about 0.1 to 10% by weight based on the dry weight of the starting material. Based on the above, the method according to the invention in the first - embodiment 1) fractionation of biomass and formation of a mixture containing liquid medium from fractions at least one of which contains lignin, 2) placing the mixture in a closed mold, 3) foaming the mixture, 4) heat treating the porous material to foam, 5) carbonizing the reinforced foam and 6) finally activating the carbonized body.

In another embodiment, the method of the invention comprises 1) fractionating biomass and forming a mixture containing a liquid medium from fractions, at least one of which contains lignin, 2) foaming the mixture, 3) placing the porous material in a closed mold, 4) heat-treating the porous material to reinforce the foam; carbonization and 6) finally activation of the carbonized body. According to one embodiment, the process according to the invention can be combined with efficient energy use by utilizing the energy of the gas streams used in the different process steps. N At the same time, liquid fractions are formed that can be utilized in other processes. Liquid fractions S 25 - can be recovered or incinerated.

O E According to another application, which can also be combined with the previous one, the volatile fractions in the carbonization step o and, in the previous application, possibly non-condensable gases 5 are burned to produce energy. The generated energy can be used, for example, in the> 30 process, heating or electricity generation. According to one embodiment, the heat energy recovered can be utilized in the internal heating of the process, i.e. in the heating of raw materials or a building, for example. According to another embodiment, the thermal energy can be sold to third parties. The carbon content of the porous body of the present invention depends on the starting material used and the temperature used in the carbonization or graphitization of the foam. According to one embodiment, the carbon content of the finished porous body is 50 to 100% by weight, preferably 75 to 100% by weight, for example 80 to 98% by weight, based on the weight of the finished body.

According to one embodiment, the porous body according to the invention has a density of 20-950 g / dm ", preferably 50-500 g / dm * and a compressive strength of about 0.07-7 MPa, preferably about 0.1-1.0 MPa. - Examples Example 1 150 g of water, 200 g of furfuryl alcohol and 25 g of surfactant (polysorbate) were first mixed together until they formed a homogeneous mixture, followed by the addition of 200 g of powdered lignin and 200 g of tannic acid, followed by vigorous stirring for several minutes. In the third step of forming the mixture N, 50 g of volatile compound (n-pentane) was added, and finally N, 100 g of acid catalyst (para-toluenesulfonic acid) was added, which started the reaction and β-foaming began as a result of the chemical reaction. was transferred to an oven to reinforce the foam LS, which was kept in the oven for 1200 minutes at 110 ° C. carbonization in the inert gas phase by raising the temperature of the foam 2 to 550 ° C. After carbonization, the body was activated at 800 ° C using steam as the activating gas. After activation, the body temperature was lowered to room temperature and the finished porous body was removed from the mold.

Industrial Applicability The method according to the invention can be utilized for the production of various porous moldable materials, and the material produced by the method can be widely used for various industrial applications. The material can be used as such or used as a starting material in other processes. The produced activated porous material can be utilized e.g. in various - cleaning applications, such as cleaning gases and liquids, and in cleaners and filters, such as car fresh air filters. Other applications for the material according to the invention are, for example, use as a filler, as a catalyst filler, for gas storage and as a porous electrode. The invention is not intended to be limited to the embodiments exemplified above, but rather to be broadly construed within the scope defined by the claims set forth below.

Reference numbers

N O. ko N 1 biomass fractionation © O 25 2nd mixture LO. . - 3. flotation and shaping

I T 4, heat treatment 2 5. carbonization and activation

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References Patent literature US3894878A WO 2005016818 A1 CN 1070021486 A CN 106587001 A US 4552863 WO 2018085918 A1 Other literature Tondi, G., Pizzi, A., Celzard, A. (2010) Tannin based foams and its derived carbon foams. - Processing Technologies for the Forest and Biobased Products Industries, Kuchl / Austria. Pizzi, A., Celzard, V., Tondi, G. (2012) Chemistry, morphology, microtomography, and activation of natural and carbonized tannin foams for different applications. Special Issue: Functional Polymeric Materials and Composites, Volume 313-314: 1, 100-111.

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Claims (12)

Patent claims A process for the preparation of porous pieces from lignocellulosic starting material, in which process - a mixture containing a liquid medium is formed from a lignin-containing fraction obtained from fractionation of biomass, - the mixture is fed to other fractions obtained from the fractionation of biomass, - the mixture is foamed and brought to a predetermined shape by means of a mold and - the shaped mixture thus obtained is subjected to a heat treatment, after which it is carbonized, - the carbonized piece is activated to increase its specific surface, - whereby it the foamable mixture contains 30-75% by weight of lignin calculated on the basis of the total weight of the mixture, characterized by - that mixture is foamed before feeding into the mold and the heat treatment is carried out in the mold as the foam piece is formed, without removing it from the mold, and - 80% by weight of lignin calculated on the basis of the dry weight of the mixture. . Process according to Claim 1, characterized in that the liquid medium consists of water, organic solution or ionic solution or some mixture thereof. and N 20 Process according to one of the preceding claims, characterized in that the mixture is foamed by mechanical mixing or chemically. LO E Process according to one of the preceding claims, characterized in that the mixture is foamed at an absolute pressure of 0.1 to 10 bar and at a temperature below 100 ° C, preferably at normal pressure and at room temperature. N - Process according to one of the preceding claims, characterized in that an open or a closable mold is used in the process, in which the foamed product is formed into a three-dimensional piece, which is formed e.g. of a cube, a cone, a cylinder or a sphere. Process according to any one of the preceding claims, characterized in that the porous material is heat-treated below 250 ° C, preferably below 200 ° C, suitably at 75-150 ° C, to stiffen the foam. Process according to any one of the preceding claims, characterized in that the foam piece is carbonized in an inert gas phase at a temperature above 500 ° C, preferably at a temperature of 600-1200 ° C. Process according to any one of the preceding claims, characterized in that - the foam piece is activated by means of water vapor, its specific surface area being preferably above 500 m 2 / g and / or the pore volume of the micro- and mesopores amounting to preferably above 0.3 cm ”/ g. Process according to one of the preceding claims, characterized in that the mixture contains 20-50% by weight of lignin, calculated on the basis of the dry weight of the mixture. Process according to any one of the preceding claims, characterized in that the lignin-containing fraction is obtained by treating biomass, such as wood or annual or perennial plants, with aqueous solution containing lignin-promoting substances, such as alkali, or with organic or ionic solvent. N A method according to any one of the preceding claims, characterized N O 20 of that foam piece reinforcing substances, mold protection substances, fire protection substances, O LO catalysts or mixtures thereof are added to the mixture before the foaming of the mixture. = = Process according to one of the preceding claims, characterized in that the volatile fractions formed in the carbonization step are condensed or incinerated. co O N