WO2010020903A1

WO2010020903A1 - Process for the production of liquid poliols of renewable origin by the liquefaction of agro-forestry and agro-food biomass

Info

Publication number: WO2010020903A1
Application number: PCT/IB2009/053485
Authority: WO
Inventors: Alessandro Gandini; José Joaquim COSTA CRUZ PINTO; Carlos Pascoal Neto
Original assignee: Universidade De Aveiro
Priority date: 2008-08-20
Filing date: 2009-08-07
Publication date: 2010-02-25
Also published as: PT104160A; EP2313358A1

Abstract

The present invention concerns the process for producing liquid polyols of renewable origin from organic materials such as agro-forestry and agro-food biomass and respective industrial residues, constituting a profitable and bio-friendly alternative to commercial polyols obtained from petrochemical sources. The said process involves two steps in a single reactor: i) the activation of the substrate with an alkaline alcoholic solution (pre-functionalization); ii) the oxypropylation and liquefaction of the activated substrate in heterogeneous conditions. The latter step might also involve the controlled addition of a monomer polyol, also of renewable origin, so as to adjust the properties of the final product, taking the desired applications into account. The present process does not require any specific operations to isolate the end product. The polyols thus obtained can be used in the formulation and preparation of polyurethanes and polyesters being applicable in food, pharmaceutical, furniture, civil engineering, automotive and polymer industries.

Description

Title of Invention: PROCESS FOR THE PRODUCTION OF LIQUID POLIOLS OF RENEWABLE ORIGIN BY THE LIQUEFACTION OF AGRO-FORESTRY AND AGRO-FOOD

BIOMASS

Technical Domain of the Invention

[1] The present invention concerns the process for the production of liquid polyols of renewable origin from organic material such as biomass of an agro-forestry and agro- food origin, including various industrial residues, namely cork powder, olive stones, grape bagasse, residues from cereal processing, residues from chitin and chitosan, residues from the papermaking industry and from the transformation of woods, or mixtures thereof.

[2] The polyols thus obtained could be used directly in the formulation and preparation of polyurethanes (including rigid and flexible foams) and polyesters being applicable, in food, pharmaceutical, furniture, civil engineering, automotive and polymer industries. Background of the Invention

[3] The renewable resource exploitation in energy and new material fields, has attracted growing attention over the last few decades, especially in order to confront the economic and environmental problems inherent to the use of fossil fuels.

[4] The production of polyols from biomass for application in polyurethanes and polyesters, traditionally based on petrochemical sources is an example of this approach and has drawn wide attention in the last few years given the importance of these materials for the development in present society of industrial areas such as furniture, civil engineering and the automobile industry. The worldwide consumption of polyurethanes is currently above 11 million tons/year.

[5] Various documents disclose processes for the production of polyols from renewable resources involving the ozonolysis of oils and vegetable or animal fats (Reference 1) or the etherification of specific substrates, as, for example, starch (Reference 2) or poly- hydroxilated alcohols (glycerol or saccharose, among others) (Reference 3), through the reaction with alkaline oxides (ethylene oxide and propylene oxide). Such approaches involve, thus, the transformation of specific agricultural biomass sources that can compete favorably with the food industry where some of these raw materials are traditionally used.

[6] In this context, the enormous quantity of side products resulting from agricultural, forestry and food industry activities, normally of low added value and intractable, represent an attractive and economical viable alternative, calling upon renewable raw substrates for the development of these new materials. This strategy is particularly interesting and relevant for the implementation of the bio-refinery concept, namely, the integral valorization of all components of a given biological resource. These initiatives are obviously important in any national context, because agricultural, forestry and agricultural activities represent areas of enormous impact for any national economy and contribute to the reduction of the dependence on fossil-based resources.

[7] In general terms, the present invention describes a novel method of oxypropylation which can be applied to the total conversion of agro-forestry residues or bio products of the food industry possessing a low added value, into polyols which can be applied to the formulation of polyurethanes and polyesters, being therefore different, compared to the process mentioned above (References 1,2 and 3) because of its transversal character: any biomass residue bearing appreciable quantities of polysaccharides, proteins, oils, phenol compounds, among others, can be used successfully as a substrate for this process.

[8] In this context, numerous examples can be cited of biomass residues which can be used as raw materials, namely cork powder, olive stones, chitin and chitosan residues, brewer's spent grain (residue from barley fermentation), residues from roasted barley/ chicory, sugarcane bagasse, wood powder or chips, tree bark, lignins and ligno- sulphonates (byproducts from cellulose pulp industry), among others. The polyols obtained through the application of the present invention, using residues of different origins, possess, in general, similar properties, except for some differences specifically in terms of their structure and rheology, which gives rise to a wide diversity of products.

[9] In addition, these polyols obtained from renewable resources, are potentially biodegradable and can hence be labeled as 'green products'.

[10] Other approaches described in various documents, including patents, for the production of polyols from biomass residues, call upon processes and reactive systems different from that described in the present invention, such as ozonolysis (Reference 1), the use of liquefying agents like ethylene carbonate or propylene carbonate with acid catalysis (Reference 4), whereas the present invention utilizes as liquefying agent propylene oxide, following a pretreatment (pre-functionalisation) with a base.

[11] The addition of a monomer polyol, selected among various hydroxylated compounds, including glycerol or a monosaccharide, during the reaction as a means to control the properties, such as the hydroxyl index and the viscosity of the final product, constitutes an additional innovation when compared to the process previously divulged (References 2 and 3). Typically, the addition of these monomer polyols, results in a product with a lower viscosity and a higher hydroxyl index. In this way, through the addition of a monomer polyol, it thus becomes possible to control the viscosity and the hydroxyl index of the ensuing polyols within a large range of values, hence widening the domain of potential applications. Description of the Invention

[12] The process described in the present invention encompasses two main steps namely a) a pretreatment of the substrate and b) its liquefaction, carried out in a single steel reactor, closed and stirred, built to withstand temperatures up to 250 ⁰C and pressures up to 30 bar, equipped with heating and cooling systems. [13] a) The pretreatment (or pre-functionalization) of the substrate is carried out by mixing the organic material with an alkaline alcoholic solution with the purpose of increasing the reactivity and accessibility of the reactive groups, preferably hydroxyl groups and, consequently, increasing the final degree of conversion of the substrate, and thus reducing the percentage of the unconverted final residual substrate from about 10-20% to less than 3%.

For the purpose of the present invention, the organic biomass matter can be, for example, cork powder, olive stones, chitin and chitosan residues, brewer's spent grain, residues from roasted barley/chicory, sugarcane bagasse, wood powder or chips, tree bark, lignins and lignosulphonates, among others, arising from agro-forestry and agro- food biomass. These examples of organic matter, represent a diversified composition, representative of different residues from agro-forestry and agro-food industries, covering the kind of biomass substrates rich in polysaccharides, phenol compounds, oils or protein substrates, among others, as well as mixtures thereof, emphasizing the transversal nature of the process with respect to the starting substrate (biomass).

The alkaline solution is prepared by dissolving a base, for example one belonging to the family of the hydroxides of alkali or earth-alkali metals, preferably potassium hydroxide, or any other Lewis or Brønsted base, in the corresponding alcohol solution under stirring. The typical percentage of the base, for example potassium or sodium hydroxide, varies between 1 and 20% with respect to the weight (of the dry biomass substrate).

Thereafter, the alkaline solution is added to the substrate using a volume sufficient to impregnate it completely and the reactor is pressurized with an inert gas to 10-30 bar. This range is defined as a function of the ease of diffusion of the pre-functionalizing agent (the base) within the texture of the biomass, i.e. lower pressures would be less efficient; whereas higher pressures will require the use of high-pressure technologies, without any significant advantage with respect to the impregnation efficiency.

At the end of the contact period between the alkaline solution and the substrate, typically between 30 and 90 minutes, during which the activation takes place, the solvent is evaporated by heating the reactor, thus making the substrate ready to be submitted thereafter to the reaction with propylene oxide. [14] b) The liquefaction of the substrate, achieved by its reaction with propylene oxide

(oxipropilation), is carried out by the addition of propylene oxide to the substrate after the activation described in the preceding point, either by its complete addition at the beginning of the reaction, or by its gradual addition during the reaction using a weight proportion which varies between 0.5 and 8.0 Kg of propylene oxide per Kg of substrate, while heating the reactor to the desired temperature (150-250⁰C). Depending on the nature of the substrate, both the range of temperatures and that of the weight proportions of propylene oxide, allows the liquefaction of the substrate to be attained leaving a percentage of unconverted final residual substrate lower than 3%. With lower temperatures and lower weight proportion of propylene oxide, the efficiency of the reaction decreases producing a correspondingly higher percentage of unconverted residual substrate.

Throughout the process, the reactor can be cooled down in order to control the temperature and hence the quality of the final product, particularly in terms of its hydroxyl index, viscosity and percentage of unreacted residue. Typically, higher temperatures favor a lower viscosity and a lower percentage of final residual product.

This latter stage can involve the controlled addition, with a weight proportion which can vary between 0 and 50% of the weight of the organic substrate, of a monomer polyol, also of renewal origin, such as glycerol or a monosaccharide, with the purpose of adjusting the properties of the final product as a function of the desired application. The addition of this monomer polyol to the reaction mixture in a gradual fashion during the process, leads typically to a decrease in the viscosity and to an increase in the hydroxyl index of the final product, thus allowing the preparation of polyols specifically adapted to the production of highly cross-linked materials to be obtained, for example, polyurethane rigid forms.

The process ends with the total consumption of the added propylene oxide, controlled by the decrease of the pressure inside the reactor, and with the cooling of the reactor to room temperature.

In this way, the product obtained consists of a mixture of polyols: the polyol formed by the oxypropylation of the substrate, the polyol resulting from the homopoly- merisation of propylene oxide and the polyol resulting from the oxypropylation of the monomer polyol (if added).

The mixture of polyols thus obtained, can be utilized directly, i.e. without any additional treatment, in the formulation of polyurethanes and polyesters, by its reaction with isocyanates and carboxylic acids, respectively, following the methodologies known and used industrially. Detailed Description of the Invention [15] 1. The biomass byproduct from agro-forestry and agro-food activities (organic substrate) previously dried and ground, is placed in a reactor, closed and stirred, constructed to withstand temperatures up to 250⁰C and pressures up to 30 bar, equipped with heating and cooling devices.

[16] 2. An alkaline alcoholic solution is then added, using a volume sufficient to cover the organic substrate, containing a Lewis or Brønsted base of 0.01 to 0.2 Kg per Kg of dry organic substrate.

[17] 3. The reactor is pressurized to 10 bar with an inert gas and stirred at room temperature for 30-90 minutes to activate the substrate (pre-functionalization step).

[18] 4. The reactor is then heated to a temperature of 50 to 80⁰C in order to evaporate the alcohol used in the pre-functionalization step; the alcohol can be later recovered and reutilized.

[19] 5. The reactor is depressurized and thereafter propylene oxide is added, totally at the beginning of the process, or gradually during the process, in a total quantity of 1.5 to 8 Kg per Kg of dry organic substrate. Concurrently, a monomer polyol can also be added, totally at the beginning of the process, or gradually during the process, in a quantity of 0 to 0.5 Kg per Kg of dry substrate.

[20] 6. The reactor, which is kept under continuous stirring, is heated up to a temperature of 150 to 220 ⁰C, which leads to an increasing pressure whose maximum is typically attained at 10 to 20 bar (oxypropylation and liquefaction step).

[21] 7. The reaction is considered as finished when the pressure decreases to a constant value, which depends on the reactor temperature, indicating the total consumption of the propylene oxide.

[22] 8. The reactor is then cooled down to room temperature and the final reaction product, a liquid polyol, is unloaded from the reactor, being ready to be used directly without any further separation or purification process.

Examples

[23] Example 1 - Preparation of polyols from cork powder, olive stones, chitin/chitosan, brewer's spent grain or roasted barley/chicory residue.

[24] The conditions used were, generally, the same for the different residues mentioned above and are described below.

[25] The two process steps carried out in a steel reactor equipped with mechanical stirring and temperature and pressure controls: i) The pre-functionalization step was carried out at room temperature in a nitrogen atmosphere (10-30 bar) for 30 to 90 minutes. The alkaline solution used was prepared by dissolving potassium hydroxide in ethanol in proportions ranging between 1 and 20 % (relative to the weight of dry substrate) and was added under stirring (using a volume sufficient to cover the substrate) to the dry substrate. The solvent was then evaporated by heating the reactor. ii) Theliquefaction of the dry and functionalized substrate was carried out at 150-220 0C and maximum pressures of 10-20 bar, for 0.5 to 8.0 hours. The quantity of added propylene oxide varied between 1.5 and 8 times the weight of the dry substrate. When used, the monomer polyol (glycerol), was added at different reaction times (at the beginning, half way through and at the end of the reaction) in total quantities that varied between 0 and 50% of the weight of the substrate. During the process, the reaction temperature was controlled by cooling with water or ethylene glycol flowing through an inner coil, in order to maintain the reaction temperature within ±5 ⁰C of the desired value.

[26] The biomass liquefaction product obtained under these conditions displays a homogeneous consistency and a brownish color.

[27] The viscosity and the hydroxyl index of the obtained polyol mixtures varied between

0.1 and 100 Pa. s and between 20 and 300, respectively, depending on the nature of the substrate and the reaction parameters. REFERENCES

[28] 1. Methods for producing biopolymers, US Patent, 60/398,766, July 26, 2002.

[29] 2. Starch-base polyethylene polyols, US Patent, 4,585,858, April 29, 1986

[30] 3. Formation of polyols. International Patent WO 86/02635, May 9, 1986.

[31] 4. Bioplastics, monomers thereof and process for the preparation thereof from agricultural feedstocks. US Patent, 2007/0175793 Al, August 2, 2007.

Claims

[Claim 1] Process for the production of liquid polyols of renewable origin, characterized in that the organic substrate is submitted to liquefaction, comprising the following steps: i) The pre-functionalization with organic substrate activation with an alkaline alcoholic solution; ii) The oxypropylation and liquefaction of the activated substrate in a heterogeneous medium.

[Claim 2] Process, according to claim 1, characterized in that the organic substrate is constituted by residues from agricultural or forestry activities and agro-forestry or agro-food industries, such as cork powder, olive stones, chitin and chitosan residues, residues from barley fermentation, residues from roasted barley/chicory, sugar cane bagasse, wood power or chips, tree bark, lignins and ligno- sulphonates, among others, or mixtures thereof.

[Claim 3] Process, according to claim 1, characterized in that the alkaline alcoholic solution contains a Lewis or Brønsted base in a quantity of 0.01 to 0.2 Kg per Kg of dry organic substrate.

[Claim 4] Process, according to the preceding claim, characterized in that the alkaline alcoholic solution comprises a potassium hydroxide solution in ethanol as pre-functionalization agent.

[Claim 5] Process, according to claim 1, characterized in that the oxypropylation and liquefaction agent is propylene oxide. [Claim 6] Process, according to claims 1 and 5, characterized in that a monomer polyol is added during the oxypropylation step. [Claim 7] Process, according to claim 6, characterized in that the monomer polyol is chosen among various hydroxyl compounds, including glycerol, a monosaccharide, an alditol or a generic glycol.