Biorefining process for lignocellulosic waste and materials

Abstract

The present invention relates to a biorefining process for lignocellulosic waste and materials, for transforming plant waste from agriculture, agro-industrial processes, agro-food industries and the timber industry. The process consists of a first step of reactions between the lignin and the hemicellulose present in the lignocellulosic material and the SO2 in the presence of water in a three-phase heterogenous system: solid, liquid and gaseous. The main products of these reactions are lignosulphonic acid and xylose, which are dissolved in an aqueous phase. The present invention achieves lignin conversions above 90%. The process continues with physical separation steps, reactions for forming lignosulphonic acid salts, reaction for forming phosphates and purification of products, thereby producing cellulose pulp, xylose, solid and dry lignosulphonic acid, solid and dry alkaline lignosulphonates, and solid and dry calcium phosphate.

Description

[0001] BIOREFINING PROCESS OF WASTE AND MATERIALS

[0002] LIGNOCELLULOSIC

[0003] FIELD OF INVENTION

[0004] The present invention relates to the techniques and principles used in the transformation process industry, and more particularly, it refers to a process for transforming lignocellulosic materials to obtain, in an integrated scheme, the following products: cellulose, lignosulfonic acid, sodium, calcium, barium, magnesium, xylose and calcium phosphate lignosulfonates.

[0005] BACKGROUND OF THE INVENTION

[0006] In the future, with sustainable development of society, biomass is expected to be one of the main renewable sources for the production of food, materials, chemicals, fuels, energy, etc.

[0007] To this end, technologies have been developed in recent years that propose lignocellulosic biomass transformation processes for the production of various products with higher added value. Such is the case of international application W02013101650 A1 entitled "Integrated biorefinery," which proposes a hydrothermal treatment of lignocellulosic biomass to hydrolyze hemicellulose in a first stage and then separate an aqueous solution containing xylose and a solid containing mainly cellulose and lignin.

[0008] The aqueous solution is subjected to a subsequent enzymatic treatment to produce xylooligosaccharides.

[0009] The mixture of solids obtained from this initial separation is dissolved in an ionic liquid, and the insoluble fraction is regenerated with deionized water. The resulting pulp is treated with a caustic solution to remove hemicellulose, followed by another enzymatic hydrolysis to produce glucose. A subsequent separation yields a solid containing lignin as its main component.

[0010] In US patent No. US962444B2, "Biorefinery process for extraction, separation and recovery of fermentable saccharides, other useful compounds, and yield of improved lignocellulosic material from plant biomass," lignocellulosic biomass is also treated with thermal hydrotreatment. In a pressurized container at a high temperature, above 250°C, an aqueous extract is produced containing mainly hemicellulosic compounds and a solid residue composed substantially of cellulose and lignin. About 23% of the original biomass is extracted by mass.

[0011] The aqueous extract is separated by centrifugation, filtration, flocculation, or membrane separation to obtain a sugar concentrate. This solution then undergoes either enzymatic or acid hydrolysis to produce xylose and glucose, accompanied by the removal of inhibitors to allow for subsequent fermentation.

[0012] The solid residue, separated from the aqueous extract, can be used to produce plastic composite materials, fiberboard or agglomerated fuel pellets.

[0013] Unlike the aforementioned documents, the present invention allows for the production of a different and greater quantity of products from lignocellulosic biomass. In the aforementioned patents, the proposed processes result in finished products such as xylose, glucose, lignin, and a solid mixture of lignin and cellulose. The present invention consists of a process that produces xylose, cellulose, lignosulfonic acid, lignosulfonates, and calcium phosphate from lignocellulosic waste and materials.

[0014] Furthermore, the process of the present invention does not require any enzyme to produce sugars or complex solid-liquid separation methods such as centrifugation, solvent extraction, ionic liquids, membranes or flocculation.

[0015] Two other recent patent applications, "Biomass fractionation process for bioproducts" LIS20110143411 A1 and "Advanced biorefinery process" LIS20120201947 A1, share a mechanical treatment of the biomass to achieve its pulverization. Hydrolysis is carried out with finely divided particles to mainly transform the hemicellulose and separate the products obtained from a solid pulp containing lignin and cellulose. In a subsequent stage, cellulose hydrolysis gives rise to products solubilized in an aqueous phase that, when separated from the remaining solid, yields lignin as a product. This hydrolysis stage for the production of glucose requires the use of enzymes as a catalyst.

[0016] For both publications, the main products obtained are xylose, glucose and lignin, and it is important to note that neither of them mentions the yields obtained per mass of biomass used, nor their purity.

[0017] In the present invention, in addition to producing other different products such as xylose, cellulose, lignosulfonic acid, lignosulfonates and calcium phosphate, all of them are produced with high yields per mass of biomass used and with high purity.

[0018] The present invention presents a flexible and modular process design that adapts to small and large production scales and is easily installed in various agricultural, timber, and industrial areas. The process achieves high yields of products with greater added value, making their production economically viable.

[0019] The refining of lignocellulosic materials should consist of the production of multiple products, efficiently utilizing their main components and intermediate compounds, generating small amounts of waste. Biorefining should consist of the integrated production of chemical products, which are highly consumed in the industrial market. With a sustainable society as a future prospect, biomasses are expected to be one of the main renewable sources for the production of food, materials, chemicals, fuels, energy, etc.

[0020] OBJECTS OF THE INVENTION

[0021] Taking into account the disadvantages found in the state of the art, an object of the present invention is to provide a biorefining process for lignocellulosic waste and materials to obtain the following products in an integrated scheme: cellulose, lignosulfonic acid, sodium, calcium, barium, magnesium, xylose and calcium phosphate lignosulfonates.

[0022] A further object of the present invention is to provide a biorefining process for lignocellulosic waste and materials that allows the transformation of waste and plant materials from agriculture, agro-industrial processes, the agri-food industry, and the wood industry. The process consists of an initial stage of reactions between the lignin and hemicellulose present in the lignocellulosic material and SO2 in the presence of water, in a heterogeneous system with three phases: solid, liquid, and gas. The main products of the reactions are lignosulfonic acid and xylose, which are dissolved in the aqueous phase. A further object of the present invention is to provide for the production of lignosulfonic acid with lignin conversions greater than 90% and the production of xylose with hemicellulose conversions close to 90%.

[0023] A further object of the present invention is to provide a process that, during the production of lignosulfonic acid and xylose, conserves nearly all of the cellulose present in the original lignocellulosic material. The present invention also proposes a chemical treatment of lignocellulosic materials, employing temperatures of no less than 130°C.

[0024] It is still another additional object of the present invention to provide a biorefining process of lignocellulosic waste and materials for obtaining lignosulfonic acid and xylose that proposes a treatment of lignocellulosic materials in a stirred tank reactor that allows a subsequent liquid-solid separation by filtration.

[0025] It is a further object of the present invention to provide a biorefining process for lignocellulosic waste and materials for obtaining lignosulfonic acid and xylose that allows easy separation by filtration of solid cellulose from all the remaining products of the transformation of lignin and hemicellulose.

[0026] Another object of the present invention is to provide a process for obtaining lignosulfonic acid and lignosulfonates that proposes, by adding CaO to the aqueous solution, separated from the solids, the precipitation and separation of calcium lignosulfonate from the products resulting from the chemical treatment. Yet another object of the present invention is to propose obtaining an aqueous solution containing lignosulfonic acid by adding H3PO4 to the calcium lignosulfonate.

[0027] Another object of the present invention is the production of lignosulfonic acid in solid phase by vaporization of its aqueous solution.

[0028] Furthermore, another object of the present invention is the production of sodium, magnesium, ammonium, barium or calcium lignosulfonates from the aqueous solution containing lignosulfonic acid, by adding the corresponding sodium, magnesium, ammonium, barium and calcium hydroxides.

[0029] Another object of the present invention is the production of sodium lignosulfonates in solid phase by vaporization of its aqueous solution.

[0030] Another object of the present invention is to propose the production of calcium phosphate in solid phase, by adding H3PO4 to calcium lignosulfonate, previously precipitated.

[0031] Furthermore, another object of the present invention is the production of cellulose pulp, separated by filtration from the aqueous suspension, a mixture of products from chemical reactions in the presence of SO2. Cellulose pulp contains over 95% of the cellulose present in the original biomass and has a lignin content close to 4% by weight.

[0032] Another object of the present invention is that, in the first stage of chemical transformation of the process, the operating conditions of the three-phase solid-liquid-gaseous reactor allow the simultaneous production with high yields of lignosulfonic acid, xylose and cellulose.

[0033] Another object of the present invention is that the simultaneous production of lignosulfonic acid, xylose and cellulose allows their subsequent separation, purification and obtaining of lignosulfonates of sodium, calcium, barium, magnesium and calcium phosphate.

[0034] Another object of the present invention is the transformation of lignocellulosic biomass, its biorefining, into a considerable number of products with greater added value: cellulose, xylose, lignosulfonic acid, sodium, calcium, barium, magnesium and calcium phosphate lignosulfonates.

[0035] Another object of the present invention is to provide processes for the transformation and treatment of lignocellulosic raw materials and intermediate products, which generate a very small amount of solid waste.

[0036] These and other objects, particularities and advantages of the biorefining process of lignocellulosic waste and materials of the present invention will be evident to a person skilled in the art from the detailed description of certain embodiments, as well as from the appended claims.

[0037] DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention relates to a process for transforming lignocellulosic materials for the production of cellulose, lignosulfonic acid, sodium, calcium, magnesium, xylose lignosulfonates, and calcium phosphate. The present invention involves the transformation of lignocellulosic biomass, with hemicellulose conversions close to 90%, lignin conversions greater than 90%, and the retention of 95% of the original cellulose. The process of the present invention produces a by-product, calcium phosphate, resulting from the use of intermediate compounds, thereby avoiding the generation of solid waste.

[0039] The present invention consists of a process for transforming solid lignocellulosic materials containing:

[0040] • A mass proportion of cellulose, expressed as mass of dry cellulose and mass of a dry lignocellulosic material, preferably between 20% and 90% and in particular between 25% and 65%, a mass proportion of hemicellulose expressed as mass of dry hemicellulose and mass of a dry lignocellulosic material, between 10% and 50%.

[0041] • A mass proportion of lignin, expressed as dry lignin mass and lignocellulosic matter mass, between 10% and 40%.

[0042] These materials are initially subjected to a grinding stage, in order to limit the length of the fibers to a maximum of 1 cm.

[0043] In a stirred tank reactor, an aqueous suspension is formed with a ratio of the total mass of the suspension to the mass of the dry lignocellulosic material of between 2 and 8.

[0044] Sulfur dioxide is added to the aqueous biomass dispersion in a ratio of 10 to 40% of the total dispersion mass to the SO2 mass. The aqueous dispersion is then heated to a temperature of between 90°C and 130°C for a treatment time of between 2 and 5 hours. In a subsequent step, the SO2 is removed from the aqueous dispersion by degassing and sent to an accumulator vessel. From the accumulator vessel, the sulfur dioxide is sent back to the reactor containing the aqueous biomass suspension to initiate another batch of lignocellulosic material transformation.

[0045] A quantity of SO2 is fed into this vessel to replace the amount consumed in the sulfonation of the lignin. A portion of the sulfur dioxide fed into the reactor is recovered by degassing and reused cyclically for a subsequent batch.

[0046] The aqueous dispersion is sent to a solid-liquid separation filter. The resulting solid is washed with water, and the aqueous solution is mixed with the liquid obtained from this initial filtration.

[0047] The washed solid is then dried, consisting of cellulose with low amounts of hemicellulose and lignin. CaO is added to the aqueous solution resulting from this first filtration, containing the products of the hemicellulose and lignin transformations, in a ratio of 11 to 3% of the mass of biomass initially fed to the mass of calcium oxide.

[0048] The solution is heated to a temperature between 20°C and 50°C for a reaction time of 20 to 50 minutes. At the end of this stage, pH values ​​between 10 and 13 are reached.

[0049] A second filtration is then performed to separate a solid mixture containing calcium lignosulfonate, which is washed at room temperature. The aqueous solution from the wash of the previously filtered solid mixture is mixed with the aqueous solution from this second precipitation, which contains mainly xylose.

[0050] The pH of this entire volume of solution, containing xylose as a product of the process, is adjusted to values ​​between 3 and 5.

[0051] The next step is to add H3PO4 to the solid mixture from this second filtration. A highly concentrated acid is added until a pH between 2 and 3 is reached.

[0052] The suspension resulting from this treatment with H3PO4 passes to a third filtration, to separate a solid containing calcium phosphate as its main product and an aqueous solution containing high purity lignosolonic acid.

[0053] The solid, which primarily contains calcium phosphate, is washed with water to recover the retained lignosulfonic acid. This washing solution is then mixed with the solution from the final filtrate.

[0054] The washed solid is then subjected to a drying stage to obtain another product of the process, dry, high-purity calcium phosphate.

[0055] The solution containing lignosulfonic acid has concentrations between 150 g / lt and 250 g / lt. This other product of the biomass transformation process, the object of the present invention, is lignosulfonic acid dissolved in water. The yields achieved of this acid, based on the transformed lignin, are greater than 97%. The aqueous solution containing lignosulfonic acid can be used in various ways. Evaporation of this solution can produce high-purity solid lignosulfonic acid.

[0056] Alkalis such as NaOH, Mg(OH)2, Ba(OH)2, CaO or NH4OH, or carbonates such as CaCOs, Na2COs can be added to the lignosulfonic acid solution to produce the corresponding lignosulfonates.

[0057] These high yields of lignosulfonic acid production, which give rise to the production of alkaline salts, the high yields of conservation of the cellulose contained in the initially treated biomass, the production of an aqueous solution containing xylose and the production of calcium phosphate, show the high efficiency of transformation of the lignocellulosic material, achieved by the process of this invention.

[0058] In order to explain the scope and use of the present invention, examples of experimental work corresponding to some embodiments of the invention are presented below. The following examples show the high yields obtained in the production of sodium and cellulose lignosulfonates, as well as the high productions of xylose and calcium phosphate.

[0059] EXAMPLES

[0060] The present invention will be better understood from the following examples, which are presented solely for illustrative purposes and are in no way intended to limit the scope of said present invention, but rather to allow a full understanding of the modalities thereof: 4 lignocellulosic materials were subjected to this transformation process: corn cob, waste from the industrial production of grain corn, teak, pine and oak wood chips, waste from industrial wood production.

[0061] In the particular case of teak wood in the form of chips, 1 kg of dry material contains 0.985 kg of organic matter, of which 0.52 kg of cellulose, 0.18 kg of hemicellulose, 0.21 kg of lignin and 0.075 kg of organic matter soluble in hot water.

[0062] The teak is dispersed in water in a ratio of 5.5 to 1, total mass of the suspension to the mass of dry lignocellulosic material. Gaseous sulfur dioxide is added to the aqueous dispersion in an amount equivalent to 9.2% of the total mass of the dispersion. This heterogeneous solid-liquid-gaseous mixture is heated to a temperature of 130°C and maintained for 4 hours.

[0063] The reactor is then cooled to a temperature range between 100° and 120°C, allowing the SO2 to escape in the gas phase and be sent to an accumulator vessel.

[0064] The reactor suspension is sent to filtration equipment to separate the solids from the aqueous phase. The solid retained in the filter is washed with water to recover retained soluble compounds, which are then mixed with the aqueous phase from the filtration. This solid is then sent to a drying stage to obtain a product with very low hemicellulose and lignin content and high cellulose content. The mass of this solid is 50.8% of the mass of the initially treated biomass.

[0065] Calcium oxide is added to the aqueous solution resulting from the filtration in an amount equivalent to 12% of the mass of the biomass initially fed. The calcium lignosulfonate formation reaction is allowed to proceed until the pH of the solution remains constant, close to 12.5.

[0066] The solids obtained from the calcium oxide treatment are separated by filtration and then washed with water. The solids washing water is added to this filtration solution, and the pH is adjusted to a value close to 4.5. Xylose, a product of the almost complete hydrolysis of the hemicellulose present in the original biomass, is dissolved in it.

[0067] A concentrated solution of H3PO4 is then added to the mixture of washed solids to transform the calcium lignosulfonate into water-soluble lignosulfonic acid, until a pH close to 2.5 is reached.

[0068] Phosphoric acid also reacts with calcium hydroxide present in the solid mixture, giving rise to calcium phosphate, also in solid phase.

[0069] Another filtration is then carried out to obtain a concentration of 190g / lt of lignosulfonic acid in the aqueous solution.

[0070] To this solution containing lignosulfonic acid, a concentrated NaOH solution is added until a pH close to 7 is reached. Finally, this solution containing sodium lignosulfonate, with a mass concentration of 210 g / lt, is subjected to drying to obtain the dry solid product.

[0071] Based on the sodium lignosulfonate mass produced, the yield of the lignin transformation present in the biomass used in the process is determined. This yield also guarantees at least the same yield as the lignosulfonic acid production. The calcium phosphate resulting from this final filtration is washed with water and dried to obtain another product from this lignocellulosic biomass biorefining process.

[0072] Results obtained

[0073] Example

[0074] It is noted that in relation to this date the best method known to the applicant to carry out the aforementioned invention is the one that is clear from the present description of the invention.Even though in the previous description reference has been made to certain modalities of the biorefining process of lignocellulosic waste and materials of the present invention, it should be emphasized that numerous modifications to said modalities are possible, but without departing from the true scope of the invention, such that the characteristics of the present invention described in the modalities and claimed in the claims, can be used individually or in any arbitrary combination for the realization of the present invention, as well as different modalities that have not been described here, consequently, it should be understood that the modalities of the present invention are only illustrative and are not intended to limit the scope of the present invention, except as established both in the state of the art and in the appended claims.

Claims

NOVELTY OF THE INVENTION CLAIMS 1.- A biorefining process for solid lignocellulosic waste and materials, characterized in that it comprises the steps of: a) subjecting the lignocellulosic materials to a grinding step to limit the fiber length to a maximum size of 1 cm; b) forming an aqueous dispersion in a tank reactor, which has a ratio between the total mass of a suspension and the mass of dry lignocellulosic material of between 2 and 8; c) incorporating sulfur dioxide (SO2) into the aqueous dispersion in a ratio between the total mass of the dispersion and the mass of sulfur dioxide of between 10 and 40; d) heating the aqueous dispersion resulting from step c) to a temperature of between 90 and 130°C for a time of between 2 and 5 hours; e) removing the SO2 from the aqueous dispersion by degassing and sending it to an accumulator container;(f) sending the SO2 from the accumulator vessel to the tank reactor containing an aqueous suspension of biomass, to initiate another batch of transformation of lignocellulosic material; (g) sending the aqueous dispersion from the accumulator vessel to a first solid-liquid separation filtration; (h) incorporating CaO into the solution resulting from the first filtration containing the products of the transformations of hemicellulose and lignin, in a ratio between the mass of biomass initially fed and the mass of calcium oxide comprised between 1.1 and 3.0; (i) heating the solution resulting from step h) to a temperature comprised between 20°C and 50°C for a reaction time comprised between 20 and 50 minutes; (j) carrying out a second filtration to separate a solid mixture containing calcium lignosulfonate, which is washed at room temperature; (k) mixing the aqueous solution from the washing of the previously filtered solid mixture with the aqueous solution from the second filtration, which mainly contains xylose; (l) adjusting the pH to values ​​between 3 and 5 of the solution resulting from step k) containing xylose as a product of process (m); adding HPO to the solid from the second filtration until reaching pH values ​​between 2 and 3; (n) filtering the suspension from step (m) to separate a solid containing calcium phosphate as its main product, another product of the process, and an aqueous solution containing high purity lignosulfonic acid; (o) washing with water and drying the solid containing calcium phosphate from step (n) to obtain dry, high purity calcium phosphate;and p) evaporate the solution from the second filtration containing lignosulfonic acid in concentrations between 150 g / lt and 250 g / lt, to obtain a dry and high purity product.; 2.- The process according to claim 1, characterized in that in an additional embodiment of the invention, after step n), alkalis such as NaOH, Mg(OH)2, Ba(OH)2, CaO or NH4OH, or carbonates such as CaCOs Na2COs are added to the solution containing lignosulfonic acid to produce the corresponding lignosulfonates. 3.- The process according to claim 1, characterized in that the lignocellulosic waste and materials comprise • a mass proportion of cellulose expressed as dry cellulose mass and dry lignocellulosic material mass between 20 and 90%; • a mass proportion of hemicellulose expressed as dry mass of hemicellulose and as dry mass of lignocellulosic material between 10% and 50%; and • a mass proportion of lignin expressed as dry lignin mass and dry lignocellulosic matter mass between 10% and 40%. 4.- The process according to claim 1, further characterized in that in step c) the container is fed with an amount of SO2 greater than that necessary for the sulfonation of the lignin. 5.- The process according to claim 1, further characterized in that in steps e) and f) the excess SO2 used in the transformation of the biomass is recovered by degassing and is reused cyclically for a next batch. 6.- The process according to claim 1, further characterized in that said process allows obtaining cellulose, lignosulfonic acid, sodium, calcium, barium, magnesium, xylose and calcium phosphate lignosulfonates. 7.- The process according to claim 1, further characterized in that it allows obtaining lignosulfonic acid with lignin conversions greater than 90%. 8.- The process according to claim 1, further characterized in that it allows obtaining xylose with hemicellulose conversions greater than 85%. 9.- The process according to claim 1, further characterized in that the operating conditions of the three-phase solid-liquid-gaseous reactor allow the simultaneous production of lignosulfonic acid, xylose and cellulose. 10.- The process according to claim 1, further characterized in that the simultaneous production of lignosulfonic acid, xylose and cellulose allows their subsequent separation, purification and obtaining of lignosulfonates of sodium, calcium, barium, magnesium and calcium phosphate.

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