WO2001064602A1

WO2001064602A1 - Biocarbon material production from a modified lignocellulosic biomass

Info

Publication number: WO2001064602A1
Application number: PCT/LV2000/000001
Authority: WO
Inventors: Janis Zandersons; Janis Gravitis; Arnis Kokorevics; Tarcisio G. Della Senta; Aivars Zhurinsh; Oskars Bikovens
Original assignee: The United Nations University; The Latvian State Institute Of Wood Chemistry
Priority date: 2000-03-03
Filing date: 2000-03-03
Publication date: 2001-09-07
Also published as: AU3334200A

Abstract

The present invention relates to the production of carbonaceous materials from biomass using steam explosion lignin as a binder. These materials are designed for use as insulation boards as well as shielding and finishing panels if temperature, chemical and biological resistance is needed. The steam explosion lignin is used as a modifier and a binder and is at first introduced in the lignocellulosic biomass by impregnation or during the hot pressing process to form a hard fiberboard. By a subsequent carbonization of the fiberboard panels or blocks due to forming an internal lignin reinforsment in cell lumina and impregnation of cell walls with lignin solution or molten lignin, carbonized panels and blocks with high bending and crushing strength and suitable thermodynamic properties are obtained. The natural product, lignin, as a binder of fiberboards and blocks for carbonization and the production of carbonized lignocellulosic material proved to be superior in comparison with a synthetic phenol formaldehyde binder.

Description

Biocarbon Material Production from a Modified Lignocellulosic Biomass

The present invention relates to the production of carbanaceous materials from biomass using steam explosion lignin as a binder.

Background of the invention

Typically, carbanaceous panels and board type materials are produced from fiberboard or particle board made from fibrous materials or chips that are bounded together via a suitable heat-hardenable thermosetting adhesive under designed pressure and temperature conditions to form the product.

According to a method of Okabe and Saito described in the Japan Kokai Tokkyo Koho JP 04 164,806 (92 164,806) a medium density fiberboard was impregnated extra with phenol resin using an ultrasonic impregnation system in a ratio of 1 : 1 by weight, hardened and carbonized in a charcoal kiln. The final glowing was carried out in a high-frequency induction furnace at temperatures of up to 2000°C. The carbonized specimens had the bending strength up to 25 MPa. To improve the physical properties of the carbonized materials, a great amount of phenol- formaldehyde resin was used, and the main problems to be faced were fissures and warps, although carbonization was carried out in a vacuum furnace.

According to another practice described by Akahori in the Japan Kokai Tokkyo Koho JP 82 67,063, fine ground chips or sawdust were mixed with a small amount of oil and heated up to carbonization temperature to obtain charcoal. The prepared charcoal was cooled, mixed with a binder and moulded in a hot press. Such a method improves the dimensional stability of the article, nevertheless the expensive synthetic phenol-formaldehyde resin is used as a binder to produce carbon wall panels.

According to still another aspect, porous carbonaceous plates are formed according to the Japan Kokai Tokkyo Koho 61 86,411 (86 86, 411) by Koshiishi. Phenol resin is mixed with sawdust in a weight ratio of 1 : 1 , filled in a mould, and a plate is formed at a pressure of 0.01 to 0.05 MPa. The resin is hardened and the plate carbonized at temperatures of above 500°C to produce a porous carbonaceous plate. The best results were achieved if the amount of phenol resin was 40 to 60%. In this patent, too, the mechanical properties and porosity were secured due to glassy carbon formation from the phenol-formaldehyde resin

In a German Patent 2,131,792, Boder discloses a method for the preparation of carbonaceous articles by making blends of sawdust or wood meal and a mixture of phenol-formaldehyde or furan resins using a catalyst In these compositions, 25 to 30% by weight are made by synthetic resins The formation of warps and fissures is precluded by an extremely low heating rate of about 3 5°C per hour The recommended maximum temperature is 1000°C and as a result a glassy carbon is formed Due to a high resin content and a long duration of the process, the method is appropriate only for the production of electrodes or other bulky articles

A method for the production of carbonaceous building material is described by Keiko and Kei in WO 9856731 It is suggested to make a sheet-form material suitable for partitions, ceiling etc directly from a charcoal with admixture of a mineral filler Practically, this material is a blend containing as one of the components charcoal or its products e g. the used activated carbon

A joint drawback for phenol and furan resins is that these are synthesized from petroleum-derived materials, hence are expensive and are not available for an acceptable price everywhere Cost wise, these resins comprise a substantial portion of the overall system cost Therefore, it would be reasonable to use a less expensive non- petrochemical phenolic binder

Lignin, is being phenolic in nature and widely distributed in lignocellulosic plant materials, had been studied in the past century Therefore, lignin is an alternative for phenol considered already There have been numerous patents and publications on lignin as a binder for lignocellulosic composite products, both as an admixture in phenol-formaldehyde resin compositions and alone In a recent patent WO 9837148 by Shen Kuo Cheng, an adhesive composition is recommended comprising a product produced by the copolymerization of one or more phenolic compounds and one or more water-soluble carbohydrates containing lignin and wood hydrolysates alone or in mixture with phenol-formaldehyde resins

The best known use of lignin as a binder is an invention of Mason and Boehm described in the U S Patent 2,303,345, wherein the steam explosion autohydrolysis process employes high pressure steam to separate lignin from the lignocellulosic matrix The hemicellulose is hydrolyzed into water solubles and removed by leaching and washing with water before the lignin and cellulose fibers are made into fiberboard. The Masonite process of making fiberboard is a commercial one, but it is currently in decline due to inefficiencies and mostly due to environmental concerns regarding enormous quantities of waste water.

DeLong, in the U.S. Patents 4,908,098 and 4, 966,650, describes a method for leaching out of lignin from steam explosion pulp in a two- or three-stage process to separate lignin from water-soluble products of hemicelluloses autohydrolysis, wherein lignin is extracted with organic solvents or alkaline water solutions. The method is laborous and the separate isolation of components is technically inconvenient.

Due to the above and other shortcomings of the above mentioned prior art technologies, an object of this invention is to provide a novel system and method for the production of carbonaceous materials by the carbonization of fiberboards.

Another object of the invention is to provide a method for binding and moulding of panels and/or boards intended for the production of carbonaceous panels and/or boards.

Still another object of the invention is to provide a cost effective and specific binders for fibreboard type materials intended for carbonization.

Other general ond more specific objects of the invention will in part be obvious and will in part appear from the description and examples which follow.

Summary of the invention

The present invention attains the above and other objects of the invention by providing a method for forming a carbonaceous material from a lignocellulosic blend containing as a binder a steam explosion lignin, a mixture of steam explosion lignin and reducing substances and a steam explosion pulp containing the above binders and a cellulosic fraction of steam explosion treated biomass: bagasse, wood and other lignocellulosic biomass of the same kind. The steam explosion lignin has a relatively low molecular mass and has a relatively high number of reactive functional groups. Being dissolved in an organic solvent, it is readily impregnated into the cell lumens and the wall of the fibrous material of biomass, e.g., milled bagasse or straw, sawdust etc. Thereby, the cell wall is reinforced to minimize the formation of warps and fissures during the carbonization process. The portion of lignin and reducing substances located at the surface of fibers acts as an adhesive if the hot-platen temperature is high enough, the preferable temperature ranging from 200 to 240°C. It has been previously demonstrated that the formation of fissures and warps is due to different rate of carbonization of the fibrous material and the binder The more direct reason for fissuring is the difference in shrinkage of different components of the composite material during the carbonization process According to our invention, the binders and modifiers are lignin and reducing substances It is reasonable to assume that the shrinkage and the rate of the thermal decomposition of lignin, reducing substances and fibers will be the same for all of them Morever, our investigations, using a scanning electron microscope have shown that some kind of framework inside the cell lumens is formed by the lignin-carbohydrate binder during the carbonization of panels Therefore, the steam explosion lignin and reducing substances binder demonstrates its positive effect upon bending strength after a high temperature carbonization process

According to another aspect, the direct admixing of the steam explosion pulp without processing to a fibrous lignocellulosic bulk of milled bagasse or sawdust demonstrates the same effect upon the bending strength of carbonized panels and boards as steam explosion lignin and reducing substances It makes the whole technological process of the production of carbonaceous materials simple and coast effective The possibility of a direct use of untreated steam explosion pulp as it is obtained after steam explosion processing makes the production of carbonaceous materials cheaper and independent from the further processing of the fibrous fraction as the case would be if only the steam explosion lignin or its mixture with water soluble products of hemicelluloses autohydrolysis would be acceptable It is another feature of our invention that the admixture of carbohydrate destruction products to steam explosion lignin and their presence in the steam explosion pulp by no means worsens the strength properties of the the carbonized panels and boards

The practice of the present invention can produce stable and strong carbonaceous panels, boards and other articles employing steam explosion lignin, a mixture of steam explosion lignin and the holocellulose destruction products and steam explosion pulp as it is obtained as a binders

The following non-restrictive examples exemplify these features Examples

Methodology for the following examples

The methods for the formation of carbonaceous panels and blocks described herein are illustrated by the following examples This methodology corresponds to the methodology employed for laboratory use, and those of ordinary skill will readily recognize the adaptations that might be necessary to this methodology for use in the existing fiberboard and panel formation systems and carbonization facilities

In all the examples, air-dry milled Brazilian bagasse and air-dry birch sawdust with a fraction measuring less than 2 mm were used

The steam explosion pulp of bagasse and birch wood prepared in a batch-type steam explosion device with a 0 5 1 reactor was used

The steam explosion parameters for bagasse and sawdust treatment were the same reactor temperature 235°C, treatment time at the reaction temperature 3 minutes, pressure 4 MPa Steam explosion lignin was prepared in a two-stage process at first, the steam explosion pulp was extracted with hot water to separate the water- soluble hemicelluloses autohydrolysis products In the second stage, the washed steam explosion pulp was extracted with 90% vol ethanol to obtain steam explosion

The lignin and hydrolysis products (reducing substances) mixture was obtained by extraction of steam explosion pulp with 90% vol ethanol

The blends for moulding of 250x250 mm panels were prepared by mixing of 700 g of air-dry milled bagasse or sawdust with a calculated amount of binder solution in 90% vol ethanol in a double-helical mixer

The blends for moulding of blocks measurig 120x15x15 mm were prepared in a similar way by thoough mixing by hand in a china jug

The impregnated fibrous material was dried in a dryer at 85-90°C for 2 5 to 4 0 hours

The blend with the steam explosion pulp was prepared by mixing the milled bagasse or sawdust with the steam explosion pulp (w = 55% wet basis) in the ratio 0 5 1 to 1 1 by weight in a double-helical mixer

Test panels 250x250 mm were made on a hydraulic hot plate press For the preparation of the test blocks 120x15x15 mm in size, a stainless steal die designated for simultaneous moulding of two specimens was used The die was electrically heated The moulding temperature was adjusted by a transformer The duration of hot pressing was calculated as 1 minute for 1 mm of the thickness of a specimen

The test blocks were carbonized in a 2 1 capacity retort heated in an electrical oven at the temperature up to 900°C The panels measuring 250x250 mm were carbonized in a laboratory thermoreactor with a maximum temperature of 700°C The heating rate was 1 6 °C x min^"1

Example 1

In this example, the efficiency of steam explosion pulp as a binder was demonstrated in comparison with phenolic alcohols The data represented in Table 1 illustrate that the uncarbonized blocks moulded with phenolic alcohols demonstrate the maximum bending strength On the contrary, after carbonization, the bending strength of the blocks with a steam explosion pulp binder are 1 5 to 2 times stronger than that of specimens made with phenolic alcohols This superiority of steam explosion pulp as a binder in the preparation of carbonized panels, blocks and other articles is due to the prevention of fissure formation during carbonization This can be observed if degree of shrinkage in the thickness of the specimens is compared The degree of shrinkage of the specimens made with phenolic alcohols is lower than that for specimens with a steam explosion pulp binder

Example 2

In this example, the efficiency of paraformaldehyde premix used as a fortifier in blends with steam explosion pulp as a binder is demonstrated. The experimental data are presented in Table 2 All the carbonized test blocks demonstrate a good blending strength The same can be said about the carbonised specimens It can be seen that the efficacy of formaldehyde is negligible and the claim of Shen Kuo Cheng (WO 9837148) that formaldehyde in lignin-carbohydrate formation improves the blending strength of the binder does not manifest itself Maybe, the pH of the present blend was not optimum for the corresponding reactions Example 3

In this example, the influence of raising the hot platen temperature on the physical properties of the carbonized sawdust panels is demonstrated. The experimental data shown in Table 3 testify that even a small increase in moulding temperature improves the physical properties of carbonized panels. The blending strength of uncarbonized panels after 24 hours of soaking in water are also improved. The thermodynamic properties of carbonaceous panels are within the limits of these properties for dry pine wood and are suitable as heat resistant insulation and finishing materials.

Example 4

In this example, the efficiency of temperature increase on the properties of bagasse panels is presented in Table 4. In this example, the binder is a mixture of steam explosion lignin and reducing substances. It is seen that, lignin - reducing substances mixture is used as a binder, the temperature must be elevated at least to 220°C. All the physical characteristics of carbonized panels are improved.

Attention should be paid to the efficacy of steam explosion products (steam explosion pulp, a mixture of steam explosion lignin and reducing substances) as binders in the process of the production of carbonaceous panels, blocks and boards. The analysis of the data represented in Tables 1 to 4 shows that the carbonaceous products obtained by the carbonization of composite products bound together with the aforementioned steam explosion products of bagasse and wood demonstrate sufficiently high physical and thermodynamic properties to meet the requirements for heat, corrosion and biological decay resistant insulation and finish materials.

It will thus be seen that the invention efficiently attains the objects set forth above, among those made apparent from the preceding description. Since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all the matter contained in the above description be interpreted as illustrative and not in a limiting sense. It also to be understood that the following claims are to cover all generic and specific features of the invention described herein, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described the invention, what is claimed as new and desired to be secured by Letters Patent is.

Table 1. Properties of carbonized specimens of bagasse and birch sawdust (pressing time 1 mm/min; pressure 96.0 MPa; hot-platen temperature 170-180°C; maximum carbonization temperature 900°C)

* the decrease of density and bending strength and degree of shrinkage is in % from parameters and dimensions of the corresponding specimens before carbonization

Table 2. Properties of carbonized specimens from milled bagasse and birch sawdust made with steam explosion (SE) pulp as binder (moulding time 1 mm/min; pressure 80.0 MPa; hot-platen temperature 180°C; maximum carbonization temperature 900°C).

Table 3. Physical properties of birch sawdust panels and carbonized panels made with SE pulp as a binder (wt. ratio 1:1; pressure 8.0 MPa ; pressing time 1 mm/min; maximum temperatute of carbonization 670°C)

* - dimension Wxc 1/2. xm xK .

Table 4. Physical properties of sugar cane bagasse panels and carbonized panels made with SE lignin and reducing substances as a binder (binder o 15% on o.d. blend mass; pressure 8.0 MPa; pressing time 1 mm/min; maximum temperature of carbonization 670 C)

dimension Wxc xm xK .

Claims

1. A method for the manufacture of carbonaceous dimension stable, heat, corrosion and biological decay resistant, insulation, isolation and finish materials from lignocellulosic biomass by compression, adhesive bonding and carbonization comprising the steps of:

(a) transforming a part of the lignocellulosic biomass by steam explosion autohydrolysis into steam explosion pulp;

(b) leaching said steam explosion pulp with organic solvent to obtain solvent soluble mater and steam explosion cellulose;

(c) mixing lignocellulosic biomass with said steam explosion pulp to form the blend;

(d) drying said blend;

(e) compresing said blend in a hot press to form fiberboard type products;

(f) carbonization of said fibreboard type products to form said material.

2. The method according to claim 1 wherein the solvent soluble matter added to the lignocellulosic biomass comprises 15 to 30% on the o.d. mass of said blend.

3. The method according to claim 1 wherein the steam explosion pulp added to the lignocellulosic biomass comprises 30 to 50% on the o.d. mass of said blend.

4. The method according to claim 1 wherein the compresing of said blend is performed at temperatures above 220°C.

5. The method according to claim 1 wherein the carbonization of said blend is performed at temperatures above 650°C.