IT201600121963A1 - CELLULOSE SACCARIFICATION, PROCEDURE OF FRACTION OF LIGNOCELLULOSIC BIOMASS AND PROCEDURE OF CELLULOSE HYDROLYSIS - Google Patents

Description

TITLE: CELLULOSE SACCARIFICATION, LIGNOCELLULOSIC BIOMASS FRACTION PROCESS AND CELLULOSE HYDROLYSIS PROCEDURE

FIELD OF TECHNIQUE

The invention concerns the production of basic sugars (glucose) which find application, for example, in the fermentation and production of (bio) ethanol, for the synthesis of chemicals and for the polymerization and production of fibers. The invention relates in particular to the isolation of cellulose from lignocellulosic material through a fractionation process and proposes a process of hydrolysis of the cellulose thus isolated. In their combination, the two processes allow the saccharification of lignocellulosic material.

STATE OF THE TECHNIQUE

Cellulosic materials exist in a great variety in nature. One such known natural material is, for example, wood. It is essentially composed of cellulose (a material composed essentially of glucose), hemicellulose (a material mainly composed of pentoses and hexoses) and lignin (a polymeric substance with aromatic rings with methoxyl groups). The use of wood occurs, for example, for the production of heat, as a construction material, for the production of paper, but a purely chemical use is also possible. Chemical methods that separate the aforementioned wood components and transform cellulose into glucose have long been known, but have several disadvantages. Two traditional principles are concentrated acid treatment and dilute acid treatment. In the first case there are large losses of glucose, and in the second case the extraction of the cellulose is incomplete. Enzymatic or microbiological methods often lead directly to ethanol without the possibility of isolating glucose, or require the use of different microorganisms or enzymes.

The cellulosic fraction, in addition to being depolymerized in order to make it more attackable by the hydrolysis process for the transformation into glucose monomers, must obviously be separated from the hemicellulose-lignin envelope, in order to increase the accessible surface for the transformation into sugars. . Furthermore, it must be partially destructured in a corresponding pre-treatment. Different pretreatment methods aimed at obviating this problem can be found in the scientific literature or already applied industrially. They include: milling, irradiation, microwave treatments, steam explosion, ammonium fiber explosion (AFEX), the use of supercritical CO2 and its explosion, alkaline hydrolysis, a treatment with liquid hot water LHW, the use of organic solvents, wet oxidation, ozonolysis, hydrolysis with dilute or concentrated acid and biological pretreatments. All these procedures are unsatisfactory from the point of view of the splitting of wood, the yield in cellulose or gucose, the economic and environmental aspect that takes into account the enhancement of all parts of the biomass, such as by-products and food waste.

Currently, for the production of biofuels, pharmaceutical and cosmetic products, polymers and pigments, the chemical industry uses basic products from the agri-food industry (sugars, starches, fibers, etc.) which are, however, also competitive in the Food and Feed market. There is a concrete need to develop new technologies for the production of polymers, biofuels and pharmaceutical and cosmetic products, which make the most of the inedible waste from the agri-food industry, in both environmental and economic terms. The current production of bioethanol uses a technology based on enzymatic hydrolysis. Although it is the most sustainable technology, it has strong limitations: long reaction times, discontinuous production, loss of carbohydrates and the formation of enzymatic growth inhibitors, due to the incompatibility of the enzymatic process with the treatment of lignocellulose, whose compact structure makes it challenging. the process of solubilization and enzymatic hydrolysis.

EXHIBITION OF THE INVENTION

The purpose of the invention is to propose an adequate process that is capable of producing a high purity cellulose already with a certain degree of decrystallization, so as to make the formation process of nanofibrillated cellulose or NFC (nanofibrillated cellulose) easier. from lignocellulosic material, i.e. from wood. A further purpose is to propose a fractionation process that allows the extraction of hemicellulose and lignin from the lignocellulosic material, in addition to cellulose, and separates the latter from the cellulose before the hydrolysis phase, in order to increase its efficiency. A further purpose of the invention is to find an effective and economically sustainable process for the saccharification of lignocellulosic materials from non-food or waste crops.

There is a concrete need to develop new technologies for the production of the aforementioned products that are not in competition with the food industry, and that make the most of the inedible waste of the agri-food industry, in both environmental and economic terms. A further purpose of the invention is to propose procedures for splitting wood and hydrolysis of cellulose obtained from splitting that does not resort to the use of enzymes. The invention then aims to propose fractionation and hydrolysis processes that minimize the degeneration to non-exploitable or inhibitory substances of alcoholic fermentation processes and that at the same time are economically sustainable, i.e. fast, scalable and with low environmental and energy impact, i.e. taking into account the following technological factors: energy balance, reagent recycling, corrosion, environmental factors and the cost of initial and operating capital.

The purpose is achieved by a fractionation process of lignocellulosic biomass which includes the following phases:

(i) a delignification of the lignocellulosic biomass in a basic environment; and (ii) a bleaching treatment with an oxidant in a basic environment of the solid resulting from step (i).

The combination of phases (i) and (ii) allows to obtain cellulose as a solid phase, while lignin and hemicellulose are found in the liquid phases produced during delignification and bleaching. Furthermore, the proposed processes are delicate processes which practically do not result in a destruction of the cellulose.

Starting substances such as lignocellulosic biomass can derive, for example, from agricultural waste, forest waste, sawdust.

In a preferred variant of the invention, step (i) includes the following steps:

(i-1) shredding and optionally screening of lignocellulosic biomass;

(i-2) suspension of the chopped biomass in water and making a basic environment, preferably by adding sodium hydroxide NaOH in a concentration of 1 to 3% by weight, more preferably a concentration of about 3% by weight, to obtain the delignification in a basic environment;

(i-3) separation of the solid and liquid phases obtained in phase (i-2), preferably by filtration, obtaining a first solid phase and a first liquid phase.

A very homogeneous mince (phase (i)) favors the reaction kinetics in the subsequent phases. Sodium hydroxide has proved to be a particularly suitable reagent for the pre-treatment phase aimed at isolating a chemically purified cellulose CPC (chemically purified cellulose). Other suitable basic reagents are, for example, basic hydroxides or oxides, in particular alkali hydroxides.

Phase separation (i-3) can take place by other methods besides filtration, such as a centrifuge. The person skilled in the art easily finds alternatives to filtration to separate the solid from the liquid with his general knowledge.

The delignification advantageously takes place at temperatures> 50 ° C, preferably at a temperature of around 70 ° C. Reaction times are often sufficient 30 minutes, but times of about two hours are preferable to complete the process.

In a very advantageous variant of the invention, the first solid of phase (i-3) is subjected in phase (ii) to the bleaching treatment with an oxidant in a basic environment in which the first solid is dispersed in a hydrogen peroxide solution H2O2 in a basic environment, preferably alkaline, in which the percentage by weight of the H2O2 corresponds to 1 - 2% and the pH is adjusted to 11.0 to 11.6, preferably to about 11.5-11.6. Other oxidants are conceivable, such as organic peroxo acids (for example: peracetic acid), but hydrogen hydroxide is also particularly suitable for activating cellulose with a partial breakdown into oligomers which subsequently facilitates its hydrolysis. The bleaching process depends on the pH. At the optimum pH point of 11.5-11.6 you will have the maximum concentration of the HO <·> radicals. Bleaching advantageously takes place at temperatures> 50 ° C, preferably at a temperature of around 70 ° C. Reaction times are often sufficient 30 minutes, but times of about two hours are preferable to complete the process. In case of incomplete bleaching, the same will be repeated on the untransformed material.

While delignification already separates a large part of the lignin from the cellulose, bleaching separates the hemicellulose from the cellulose and in addition changes the crystalline structure of the cellulose and begins to weaken it and break it into short chains.

To transform the cellulose into a form suitable for hydrolysis, in a preferred variant of the invention, step (ii) is followed by a step (iii) of separating the mixture obtained in step (ii) into a second solid phase and a second liquid phase, e

by a step (iv) in which said second solid is transformed by disintegration, preferably in a dispersion in water, into nanofibrillated cellulose.

Nano-fibrillated cellulose is characterized by fiber widths or diameters <100 nm, usually between 1 and 15 nm, often less than 10 nm. These dimensions can be determined, for example with a scanning electron microscope (SEM, Scanning Electron Microscope) or other microscopy or diffraction techniques known to the expert.

Disruption can occur with many types of disrupters available on the market, such as blenders, homogenizers, ultrasonic disrupters.

Preferably, the first and / or second liquid phase is / are acidified, preferably at a pH <2, more preferably at a pH of about 1.5, to cause precipitation of lignin and the lignin is separated, preferably by centrifuge, respectively from a third and / or fourth liquid phase. Lignin is used in the zoo-pharmaceutical industry, as a natural antibiotic for chickens or even as a fuel.

Acidification takes place preferably with inorganic or mineral acids, preferably with sulfuric acid H2SO4 or hydrochloric acid HCl.

The recovery of the lignin is then carried out by causing it to precipitate in an acid environment. The pH is a variable of great influence on the precipitation of lignin from the black liquid produced by the alkaline process. There is an increase in the mass of the precipitated lignin by decreasing the pH below neutrality, in particular around 1.5, an almost total recovery can be advantageously obtained. The recovery of lignin is not only interesting from an environmental point of view, but also from an economic point of view, because it can be reused to obtain various chemical products of commercial interest.

To integrate the fractionation, in a preferred variant of the invention, the pH of the third and / or fourth liquid phase is raised, preferably to about 5.5, and a less polar solvent than water, preferably ethanol, is added to make precipitate the hemicellulose which is optionally separated. The raising of the pH advantageously occurs with NaOH, other bases are conceivable, such as hydroxides, basic oxides, in particular alkaline hydroxides. Ammonia can also be used. The third component of wood is thus obtained, the hemicellulose which is an important compound for the production of paper (it makes the paper opaque for example) or as a basic compound for the production of furfurals or furans from pentoses. Alternatives to ethanol are other neutral non-ionic surfactants, such as fatty alcohols.

The nanofibrillated cellulose, in particular that obtained according to the fractionation process according to the invention, can be subjected to hydrolysis.

A further aspect of the invention relates to a cellulose hydrolysis process which comprises the cellulose suspension phase, preferably the nanofibrillated cellulose obtained according to the invention, together with a water-insoluble solid material containing acid groups, preferably an ion exchange resin acid, in an aqueous solvent, preferably water, which results in the hydrolysis of cellulose turning into glucose. The use of "solid acids", such as in particular ion exchange resins, such as ion exchange resins carrying protons H <+>, allow the catalysis of hydrolysis on a large surface and localized in defined points on the acid catalyst and on the cellulose in interaction with the catalyst. Very suitable is, for example, a resin based on styrene divinylbenzene with –SO3H groups such as Amberlyst 15 <®>. The catalyst functions as a proton membrane in an electrochemical transformation. The supposed reaction mechanism is constituted by the absorption of glucans through the interaction of van der Waals on the catalyst and subsequent hydrolysis through the surface groups - SO3H.

The use of these solid catalysts determines a significant improvement in the efficiency and sustainability of hydrolysis. The main advantages include the recyclability of the catalyst, the non-corrosive reaction media and therefore less damage to the reactor, without the need to neutralize acids or bases and, consequently, the formation of unassociated salt, the ease of separation of the product , moreover, reduction of pollutants. Advantageously, hydrolysis occurs under pressure at temperatures around 120 ° C. A suitable reactor is an autoclave or an acid digester, i.e. an acid digestion bomb present on the market in the paper bleaching industry (Kraft process).

Very advantageously, the water-insoluble solid material containing acid groups is separated from the hydrolysis solution, regenerated and re-introduced into the hydrolysis process. The acid used in hydrolysis does not produce acid waste.

A final aspect of the invention relates to a lignocellulosic biomass saccharification process that combines the fractionation and hydrolysis processes according to the invention and includes

(a) the fractionation of the lignocellulosic biomass according to the invention, obtaining a nanofibrillated cellulose; And

(b) the hydrolysis of cellulose according to the invention of nanofibrillated cellulose.

Compared to traditional saccharification processes that involve a deterioration or loss of cellulose up to 90% (pretreatments with concentrated acids) or 20-30% in the case of treatments with diluted acids, the proposed procedure results in a much lower loss, only 2-3% of the total cellulose, hemicellulose and lignin.

The proposed processes have several advantages: the separation of the lignocellulosic biomass into cellulose, hemicellulose and lignin; a low degenerative coefficient of cellulose, a transformation of cellulose into an easily hydrolyzable form, the use of few reagents, the avoidance of enzymes and short reaction times.

In summary, the fractionation process according to the invention provides a pretreatment step which consists in the isolation of the chemically purified cellulose and in the simultaneous recovery of the lignin and hemicellulose, as in the solubilization and depolymerization of the cellulose (partial disintegration into oligomers) before the hydrolysis phase and then the optimization of hydrolysis through the use of solid materials carrying acid groups.

The process according to the invention made it possible to obtain, with the choice of appropriate reagents, the fractionation of the wood source and the isolation of chemically purified cellulose, lignin and hemicellulose. In addition, the activation of the cellulose was achieved by transforming it into a nanofibrillated cellulose. The particular fractionation process that led to a high degree of crystallization of the cellulose, facilitated the production of nanofibrillated cellulose through the use of a simple disruptor. The alkaline solution used for delignification promoted the breaking of the ester bonds between lignin and carbohydrates and its fragmentation and dissolution. As a result, there was a great lignin removal efficiency. In addition, alkaline solutions have the effect of swelling the biomass, altering the degree of crystallinity of the cellulose. The latter aspect could lead to the side effect of the partial solubilization of hemicellulose, since hemicellulose is generally defined as a low molecular weight and therefore soluble polysaccharide, which can be extracted from lignocellulosic tissues by water or alkaline solutions. This is a problem as the cellulose recovered in this delignification phase is still partially linked to lignin, a solution has been found by reducing the concentration of the base (for example: NaOH from 3% to 1% by weight). By recovering the hemicellulose only in the bleaching phase, it will be possible to have a solid of a whiter color, a consequence of a lower content of associated lignin, compared to that obtained in the alkaline delignification phase. During the alkaline de-lignification it was also found that this phase did not lead to a complete dissolution of the lignin; this is due to the fact that lignin has two types of bonds within the lignocellulosic structure. Ester bonds susceptible to alkaline solutions and ether bonds which are not susceptible. Consequently, it was appropriate to proceed through an oxidation step (bleaching).

The alkaline peroxide solution, used in the bleaching phase, has proved to be very effective both for the de-lignification and for the solubilization of hemicellulose from lignocellulosic materials, as H2O2 is unstable in alkaline conditions and easily decomposes into hydroxyl radicals (HO <· >) and superoxide radicals (O2 <·>). These radicals probably cause the oxidation of the lignin structure, due to the splitting of some bonds between the units and, finally, to the dissolution of lignin and hemicellulose without damaging the latter, with the possibility therefore of recovering the latter at the solid state, which is difficult to do with acid treatment. Other treatments known in the art lead either to high management costs (process with organic solvents) or to complicated operating conditions (Kraft process).

During the treatment with alkaline hydrogen hydroxide not only the dissolution of the lignin is completed, but there is also a complete dissolution of the hemicellulose, in addition there is the consequence of a high depolymerization / decrystallization of the cellulose.

For disintegration it is preferable not to dry the chemically purified and partially depolymerized cellulose isolated in the fractionation process, since during drying it loses its disintegrated structure, which makes its transformation into nanofibrillated cellulose more difficult. These complications have also been found in an attempt to activate (break down) commercial microcrystalline cellulose.

For the production of nanofibrillated cellulose from pure crystalline cellulose, the technologies that can be used can be: ball milling method, mixed grinding or mechano-catalytic depolymerization of cellulose (grinding the cellulose and the catalyst, for example sulfuric acid, together) , treatment of cellulose (4% by weight) with NaOH / urea / H2O in a ratio of 7:12:81 and dispersion by ultrasound or with a homogenizer, use of microwaves.

As reported in Table 1, which shows the mass balance of the components of the treated biomass, the recovered cellulose consists mainly of the depolymerized component (93% of chemically purified cellulose partially depolymerized on total cellulose). The mass balance was obtained by isolating, drying with a thermal balance and weighing the various solid phases of the process.

Table 1

Component Mass% in% by weight on cellulose

[mg] weight on total

biomass

initial

biomass 1030 ± 1 - crystalline cellulose 40 ± 1 3.9 7.4

cellulose 498 ± 1 48.3 92.6

depolymerized

total cellulose 598 ± 1 52.2 - hemicellulose 262 ± 1 25.4 - lignin 209 ± 1 20.3 - dry matter 21 ± 1 2.0 - remaining

The procedures devised by the invention for the fractionation of biomass and for the production of sugars proved to be valid for the set objective, that is the development of a technology suitable for the treatment of lignocellulosic biomass with high structural complexity and which is at the same time effective, that is, capable of splitting the three components of the lignocellulosic structure and extracting the maximum quantity and quality of simple sugars, minimizing their degeneration into non-exploitable or inhibitory substances of alcoholic fermentation processes. These are economically sustainable, i.e. scalable, processes with a low environmental and energy impact.

The isolation of cellulose, ignoring the isolation of lignin and hemicellulose, is preferably divided into the following phases:

(i) pretreatment with:

(i-1) grinding of biomass,

(i-2) alkaline delignification with sodium hydroxide NaOH,

(i-3) bleaching with hydrogen peroxide H2O2 in a basic environment,

(i-4) recovery and solubilization / depolymerization of chemically purified cellulose forming nanofibrillated cellulose

(ii) hydrolysis of nanofibrillated cellulose with “solid acids”.

The basis for the hydrolysis process is the solubility of cellulose. Native cellulose is not soluble, as it has a highly crystalline structure stabilized by a strong network of intra- and intermolecular hydrogen bonds. Table 2 shows the solubility of glucose and cellulosic polymers.

Table 2

Sugar / cellulose Solubility in water [g / l] at 25 ° C

glucose 909

cellobiose 120

Soluble oligosaccharides (nanocellulose, 3-10 units)

insoluble polysaccharides (microcellulose)

The table shows that the degree of polymerization has a significant influence on the hydrolysis efficiencies of cellulose. According to the literature, it is possible to depolymerize / solubilize crystalline cellulose through the use of acidic or basic solvents, capable of dissolving the cellulose without chemically modifying the constituent molecules (referred to as non-derivatizing solvents); or through the use of microwaves or bombs for digestion in dilute acid or base. In this way, already arriving at the formation of the nanocellulose, it will be possible to have a significant increase in efficiency. Commercially, two general classes of cellulose nanomaterials can be found, which are crystalline nanocellulose and NFC nanofibrillated cellulose which appears at the nanometer level as a network of highly intertwined filaments (glucan chains), while crystalline celluloses appear as rods. highly rigid. The type of nanocellulose that best suits the aim of the invention is nanofibrillated cellulose. The advantages obtained are a greater production of glucose due to the lower presence of hydrogen bonds. The invention has succeeded in proposing a process that produces nanofibrillated cellulose through moderate operating conditions that lead to lower initial and management costs than standard methods.

The aforementioned purposes and advantages will be better highlighted during the description of a preferred embodiment of the invention given by way of example, but not of limitation.

Variants of the invention are the subject of dependent claims. The description of the preferred example of execution of the procedure according to the invention is given by way of non-limiting example with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWING

Fig. 1 illustrates in a block diagram an executive example for the saccharification of lignocellulosic material which includes the pretreatment and fractionation process of the lignocellulosic material and the hydrolysis of the isolated cellulose in this fractionation process.

DESCRIPTION OF A FAVORITE EXAMPLE OF EXECUTION

Figure 1 illustrates in a block diagram an executive example for the saccharification of lignocellulosic material which comprises a pretreatment-fractionation process of the lignocellulosic material A and a process of transformation of isolated nanofibrillated cellulose into glucose B through hydrolysis. The pretreatment-fractionation A leads to the isolation of purified and nanofibrillated cellulose, hemicellulose and lignin. The fractionation comprises on the branch leading to the cellulose fraction two sub-processes, and in particular the alkaline delignification A-1 and the oxidative bleaching A-2.

Phase A: Isolation of chemically purified cellulose and recovery of lignin and hemicellulose

At the start there is the crushed and screened woody material (lignocellulosic biomass) 2 to which sodium hydroxide NaOH 4 is added. Specifically, the chopped mass is treated with a solution of sodium hydroxide NaOH at 3% by weight (w / p) for two hours at 70 ° C under magnetic stirring (30 ml of water, approx. 1 g of minced material, 0.93 g of NaOH). This alkaline delignification treatment 6 aims to remove the lignin. At the end of the alkaline treatment, the solution becomes dark brown due to the solubilization of the lignin in a basic environment. At the end of the alkaline delignification phase, the presence of a whitish crystalline cellulosic residue, consisting mainly of carbohydrates, is also noted. Filtration 8 is carried out, at the laboratory level for example with a Büchner filter. The phase of isolating the chemically purified cellulose follows:

The solid residue 10, a crystalline cellulose, is brownish in color, attributable to incomplete delignification. To complete the delignification it is not sufficient to increase the reaction times or the temperature, but it has proved appropriate to proceed with a bleaching step 12 through the use of an alkaline oxidant 14. The preferred oxidant is <hydrogen peroxide H> 2 <O> 2 <in a basic environment (alkaline hydrogen peroxide, AHP).>

Consequently, 1.6 ml of H2O2 (at 130 volumes, title 35 g / 100 g) concentrated in 30 ml of deionized water is dissolved and the pH is brought to a value of 11.5 using a 5M solution of hydroxide of sodium NaOH. The solid cellulosic residue 10 obtained in the previous step is dispersed in this solution. With the bleaching phase 12, it is possible to completely whiten the cellulose, a consequence of the completion of the dissolution of the lignin. In addition, a further depolymerization of the cellulose is obtained, that is, a partially depolymerized cellulose which, thanks to its hydrophilicity, is finely dispersed in the water. A small part (7%) of a non-depolymerized crystalline cellulose residue remains which is separated by decantation 16. The crystalline cellulose is reprocessed, inserting it into the process in step 6, in order to decrease its degree of crystallization. The dispersion is filtered 18 which provides a solid 20 and a filtrate 22. The two types of cellulose represent a chemically purified cellulose (CPC) from hemicellulose and lignin, which is divided into a partially depolymerized chemically purified cellulose (CPC-DP ) 20 and in a chemically purified crystalline cellulose CPC-C 16.

In summary, the recovery of chemically purified cellulose consists of two phases:

(a) delignification with 3% (w / w) NaOH at 70 ° C for 2 hours; And

(b) bleaching with 2% (w / w) of H2O2 / NaOH at pH 11.5 for 2 hours at 70 ° C.

With the above procedure it is possible to completely recover the cellulose, consisting mainly of the depolymerized component (93% of the total cellulose) and 7% of crystalline cellulose. The partially depolymerized cellulose is subjected to an NFC nanofibrillated cellulose production step:

The chemically purified cellulose 20 obtained after the bleaching step 12 is dispersed in water 24 and is further solubilized / depolymerized by means of a simple disintegrator 26. The result is the realization of a dispersion / suspension of cellulose nanofibrils in water 28.

The filtrate 30 of filtration 8 after alkaline delignification 6 and filtrate 22 of filtration 18 after bleaching 12 are then used for

recovery of lignin and hemicellulose:

The filtrates from the alkaline delignification (brown filtrate) 30 and from the bleaching phase (yellowish transparent filtrate) 22 are further treated and initially concentrated (to the initial reaction volume) to make it easier for the precipitation of lignin and hemicellulose. The resulting solutions are respectively constituted by monomers of lignin, hemicellulose and to a small extent by derivative products of sugars. The color of the solutions is mainly due to the presence of more or less concentrated lignin monomers (more or less brown color).

The residual solution from the alkaline delignification step 30 is treated with a solution of hydrochloric acid HCl 32 to precipitate the lignin 34 up to pH = 1.5 and subjected to centrifuge 36 to easily recover the precipitate, the lignin 37 (which can be dried with thermal balance). As an alternative to hydrochloric acid, for example, sulfuric acid H2SO4 could also be used.

The solution resulting from the bleaching step 12 is acidified 38 to pH = 1.5 and centrifuged 40, resulting in an insignificant amount of lignin (<1 mg) 42.

For the recovery of the hemicellulose, the deliberate solutions 39 and 43 are further concentrated from the precipitates 37 and 42 and the pH is brought to a value of 5.5 using a 5 M sodium hydroxide solution, in steps 44 and 46 respectively The result is a decrease in the solubility of the hemicellulose which made the solutions cloudy. From the suspensions obtained it is precipitated with two volumes of ethanol (95% v / v), i.e. by adding a volume of ethanol that corresponds to double the volume of the suspension, in steps 48 and 50, the hemicellulose is then separated by centrifuge 49, 51. The remaining solutions 56 and 58 do not contain cellulosic material in significant quantities, but are made up of monomers of lignin, of hemicellulose and to a small extent of derivative products of sugars. The color of the solutions is mainly due to the presence of more or less concentrated lignin monomers. Darker colors of solutions are due to a higher concentration of lignin monomers.

The recovered hemicellulose 52, 54 is dried with a thermal balance. The hemicellulose is recovered with a greater amount from the filtrate 30 of the alkaline delignification step. The recovered hemicellulose has a brownish color due to the associated lignin content characteristic of the hemicellulose precipitate recovered from the delignification phase. The remaining solutions 56 and 58, after the removal of the three lignin components, chemically purified cellulose and hemicellulose, consist mainly of soluble acid lignin represented by low molecular weight molecules or hydrophilic derivatives of lignin which determine the yellowish color of the solution, with a higher concentration in solution 58 resulting from the alkaline delignification process. This yellowish color is not attributable to the decomposition of the cellulose, this has been experimentally verified by applying the bleaching step on the commercial crystalline cellulose and noting any variation in the color of the solution.

In summary, the recovery of the lignin is achieved by precipitating the latter at pH = 1.5 (32, 38g), the recovery of the hemicellulose, on the other hand, is achieved by bringing the relative solution to a pH = 5.5 (46, 46 ) and adding two volumes of ethanol (48, 50) in order to favor its precipitation. Finally, the last phase of wood saccharification is added, namely the

phase of glucose synthesis from nanofibrillated cellulose:

The nano-fibrillated cellulose 28 is transferred to an autoclave and subjected to a hydrolysis 60 at 120 ° C in the presence of an acid ion exchange resin (Amberlyst 15®) (acid catalyst) where after separation of the solid, the resin can be recovered, recycled and reintroduced 62 in the hydrolysis process 60 which produces sugars in the form of glucose from cellulose 64.

The hydrolysis was carried out experimentally by loading the reaction tube with 100 mg of nanofibrillated cellulose, 100 mg of catalyst and 1 ml of water. After homogenization, the reactor is placed in an autoclave so as to bring the reaction temperature to 120 ° C. The presence of glucose is already detected after one hour of reaction, and after five hours there is no longer any increase in glucose yield. At the end of the first execution of the reaction (after five hours), the solid catalyst is filtered and separated from the cellulose residue and is regenerated before its reuse. Then the catalyst is reinserted into the reaction tube together with the cellulose residue and the reaction is then carried out again for another five hours at 120 ° C.

This repeated operating mode leads to an almost complete conversion of the nanofibrillated cellulose into glucose with an insignificant formation of unwanted products. The suspension becomes clear and transparent. The bleaching process 12 can also be repeated on the solid obtained to complete the separation of the hemicellulose.

The invention has therefore achieved all the objectives set. The invention, among other things, has provided a process for the production of sugars from lignocellulosic material capable of offering the maximum quantity of high purity extractable sugars, i.e. without non-exploitable or inhibitory substances for the alcoholic fermentation processes and this in a fast, scalable and low environmental and energy impact process. With the invention it is possible to degrade or separate the lignin and hemicellulose from the cellulose without damaging any component, thanks to a selective and minimally invasive chemical treatment. Degeneration to non-exploitable or inhibitory substances of alcoholic fermentation processes has been minimized, also thanks to the use of catalytic protons. Short reaction times are achievable in each step of the process. In addition, it has been possible to propose a process useful for eliminating the production of high-impact toxic processing waste.

In the executive phase, further modifications or executive variants not described may be made to the fractionation, hydrolysis and saccharification processes, object of the invention. Should such modifications or variations fall within the scope of the following claims, they must all be considered protected by this patent.

Claims (10)

CLAIMS 1) Process of fractionation of lignocellulosic biomass (A) comprising the following phases: (i) delignification of the lignocellulosic biomass in a basic environment (A-1, 6); and (ii) bleaching treatment (A-2, 12) with an oxidant in a basic environment (14) of the solid (10) resulting from step (i). 2) Process of fractionation of lignocellulosic biomass (A) according to claim 1 characterized in that step (i) comprises the following steps: (i-1) shredding and optionally screening of lignocellulosic biomass; (i-2) suspension of the chopped biomass (2) in water and making a basic environment (4), preferably by adding sodium hydroxide NaOH in a concentration of 1 to 3% by weight, more preferably a concentration of about 3% in weight, to obtain delignification in a basic environment (6); (i-3) separation (8) of the solid and liquid phases obtained in phase (i-2), preferably by filtration, obtaining a first solid phase (10) and a first liquid phase (30). 3) Process of fractionation of lignocellulosic biomass (A) according to claim 2 characterized in that said first solid (10) of phase (i-3) is subjected in phase (ii) to the bleaching treatment (12) with an oxidant in basic environment (14) in which the first solid (10) is dispersed in a solution of hydrogen peroxide H2O2 in a basic environment (14), preferably alkaline, in which the percentage by weight of H2O2 corresponds to 1 - 2% and the pH is adjusted to 11.0 to 11.6. 4) Process of fractionation of lignocellulosic biomass (A) according to any one of the preceding claims characterized in that said step (ii) is followed by a step (iii) of separation (18) of the mixture obtained in step (ii) in a second solid phase (20) and a second liquid phase (22), and a phase (iv) wherein said second solid (20) is transformed by disintegration (26), preferably in a dispersion in water (24), into nanofibrillated cellulose (28). 5) Process of fractionation of lignocellulosic biomass (A) according to any one of claims 2 to 4 characterized in that said first (30) and / or said second liquid phase (22) is / are acidified (32, 38) , preferably at a pH <2, more preferably at a pH of about 1.5, to cause the precipitation of lignin (34, 40) and that said lignin is separated (37, 42), preferably by centrifuge, respectively from a third (39) and / or fourth liquid phase (43). 6) Process of fractionation of lignocellulosic biomass (A) according to claim 5 characterized in that the pH of said third (39) and / or said fourth (43) liquid phase is raised (44, 46), preferably to about 5, 5, and that a less polar solvent than water (48, 50), preferably ethanol, is added to precipitate the hemicellulose (52, 54) which is optionally separated (49, 51). 7) Cellulose hydrolysis process (B) comprising the suspension phase of the cellulose, preferably the nanofibrillated cellulose obtained according to claim 4, together with a water-insoluble solid material containing acid groups, preferably an acid ion exchange resin, in a aqueous solvent, preferably water, which results in the hydrolysis of cellulose (60) transforming into glucose (64). 8) Cellulose hydrolysis process according to claim 7 characterized in that said water-insoluble solid material containing acid groups is separated from the hydrolysis solution, regenerated and re-introduced (62) in the hydrolysis process. 9) Process of saccharification of lignocellulosic biomass comprising (a) fractionation of the lignocellulosic biomass (A) according to any one of claims 4 to 6; And (b) the hydrolysis of cellulose (B) according to claim 7 or 8. 10) Use of the glucose (64) obtained according to any one of claims 4, 7 or 8 for alcoholic fermentation or the production of polymers.