WO2024002953A1 - Lignocellulose biomass extract, and method for obtaining a green synthesis gas - Google Patents

Abstract

The present invention relates to an extract obtained from lignocellulose biomass, a process for manufacturing said extract, and uses thereof. In particular, the present invention relates to an extract obtained from a lignocellulose biomass comprising cellulose and at least 1%, preferably at least 5% by weight of the total weight of the extract, of residual lignin.

Description

LIGNOCELLULOSIC BIOMASS EXTRACT AND METHOD FOR OBTAINING A GREEN SYNTHESIS GAS

Technical area

The present invention relates to the technical field of green synthesis gas, that is to say obtained from lignocellulosic biomass. The subject of the invention is in particular a particular lignocellulosic biomass extract, its process for obtaining it, a green synthesis gas as well as its manufacturing process from said particular lignocellulosic biomass extract.

Prior art

Over the past few years, our world has seen a steady increase in the concentration of CO2 in the atmosphere. Well known to climate experts, atmospheric CO2 is considered one of the main greenhouse gases responsible for global warming.

The net increase in atmospheric CO2 concentration is mainly of anthropogenic origin via the increase in the production and consumption of fossil sources (oil, coal, natural gas). Faced with climate change, the population is becoming aware of the major challenges of energy issues associated with environmental pollution. For example, the Paris agreement held in 2015 requires from the 196 parties an economic and social transformation making it possible to establish a long-term development strategy with low greenhouse gas emissions, such as the CO2 of fossil origin. Thus, the population and manufacturers are looking for new viable energy sources to reduce CO2 emissions.

Biomass, through its vast reserves and its natural origin, is considered one of the sources of renewable energy with the greatest potential to date. Indeed, biomass can be used as a raw material for the production of renewable gases (biogas, hydrogen).

The gasification of biomass makes it possible to convert biomass into a high value added product, a green synthetic gas that does not impact the carbon dioxide content of the atmosphere and therefore is neutral in fossil carbon.

Biomass gasification is a complex process that generates gases, such as hydrogen, carbon monoxide, carbon dioxide and methane, which can be used as gaseous fuels or for chemical synthesis. However, this process also produces undesirable by-products, such as tars (tars) and solid residues composed of ash and carbon (chars).

The presence of tars in the synthesis gas causes major problems such as the release of carcinogenic and toxic elements. The tars thus formed from lignocellulosic biomass cannot therefore be valorized during gasification. In addition to tars and tanks, gasification produces solid, liquid and gaseous pollutants such as nitrogen compounds (ammonia, nitrogen oxides), sulfur compounds (sulfur oxides, hydrogen sulfide), chlorinated compounds (acid hydrochloric acid), alkaline earth metals (potassium, sodium, magnesium, calcium, etc.) and heavy metals (lead, nickel, copper, mercury, zinc, etc.) and fine particles (mineral ashes, particles of carbon, etc.).

These pollutants and impurities impose numerous constraints, particularly due to clogging of the process, wear of equipment and the cost of maintenance.

These cumulative elements have been the essential obstacles to the industrial development of direct biomass gasification technology for almost a century.

To deal with these issues and reduce or eliminate tars and pollutants in order to produce quality green synthetic gas, there are different strategies.

Among the techniques used, we find:

- in situ reduction techniques such as adding catalyst or modifying gasifier parameters;

- post-gasification purification techniques such as the use of separation devices or thermal cracking of tars at high temperatures;

- techniques for extracting lignocellulosic biomass so as to gasify only the cellulose.

Adding catalyst to the mixture is a promising technique to solve the problem of formation of pollutants such as tars. However, although effective in reducing the formation of pollutants, this technique also has unresolved disadvantages.

Indeed, deactivation, sintering, coke deposition as well as economic feasibility must be taken into account to achieve large-scale biomass gasification.

Furthermore, the added catalysts do not have identical performance in terms of tar reduction, which makes the composition of the synthesis gas uncertain. The use of catalyst is essential to at least partially overcome the disadvantages of direct gasification.

Another promising technique is envisaged in patent application EP3771738, which consists of eliminating the components of lignocellulosic biomass which would inhibit the gasification reaction, such as lignin.

There is therefore a need for new alternatives to produce a green synthetic gas containing no pollutants, obtained without the addition of a catalyst.

Summary of the invention To meet this need, the invention proposes a new extract obtained from a lignocellulosic biomass allowing, by direct pyrogasification, to obtain a green synthesis gas not containing nitrogen compounds and sulfur compounds.

Thus, the invention relates to an extract obtained from a lignocellulosic biomass comprising cellulose and at least 1% lignin by weight of the total weight of the extract.

Preferably, the extract according to the invention comprises at least 5% of residual lignin, in particular at least 6%, 7%, 8%, 9%, 10%, even more preferably at least 20% by weight of the total weight of the 'extract.

Contrary to the teachings of the prior art, the inventors discovered that lignin:

- was not the cause of the appearance of pollutants during the gasification of lignocellulosic biomass; And

- is not an undesirable compound for carrying out gasification, in particular pyrogasification.

Advantageously, lignin, in addition to cellulose, makes it possible to provide a significant source of hydrogen in the extract.

Preferably, the extract according to the invention does not comprise hemicellulose and proteins.

According to a preferred object of the invention, the extract obtained from a lignocellulosic biomass according to the invention comprises a content of inorganic compounds at least 10 times lower than the content of inorganic compounds of said lignocellulosic biomass.

According to another aspect, the invention relates to a process for preparing an extract according to the invention comprising the implementation of the following steps:

1) Mixture of a lignocellulosic biomass with a solvent consisting of water and formic acid;

2) Separation, at atmospheric pressure and temperature of the mixture of step 1), of the solid fraction, constituting the cellulose paste, from a liquid organic phase containing in solution at least the solvent of step 1) and all undegraded molecules of lignocellulosic biomass.

Preferably, the solvent of step a) comprises at least 85% by weight of formic acid.

Advantageously, formic acid is particularly effective in precipitating cellulose. The solid fraction, forming the cellulose pulp, also includes lignin interacting with the cellulose, we speak of residual lignin.

According to another aspect, the invention relates to a process for manufacturing a synthesis gas comprising the implementation of the following steps: a) Pyrolysis of the extract according to the invention; and b) Gasification of the char obtained in step a) without adding catalyst. Advantageously, such a method makes it possible to resolve the drawbacks of the prior art. Indeed, the process according to the invention makes it possible to obtain a green synthesis gas devoid of nitrogen compounds and sulfur compounds, preferably devoid of any pollutant, without a post-gasification purification step.

In a particularly advantageous manner, the process for manufacturing a synthesis gas according to the invention makes it possible to obtain a high quality green synthesis gas, having a calorific value greater than at least equivalent, preferably greater than that of a gas synthesis obtained from the gasification of raw lignocellulosic biomass at low cost.

According to another aspect, the invention relates to a green synthesis gas obtained from a lignocellulosic biomass not containing sulfur compounds and nitrogen compounds.

Preferably, the synthesis gas according to the invention does not contain any pollutant. More particularly, said synthesis gas does not contain:

- tars;

- nitrogen compounds such as ammonia and nitrogen oxides;

- sulfur compounds such as sulfur oxides;

- chlorinated compounds such as hydrochloric acid;

- alkali metals such as potassium, sodium, calcium and magnesium;

- heavy metals such as lead, nickel, copper, mercury and zinc; And

- fine particles such as mineral ash or carbon particles.

Preferably, the synthesis gas is obtained from an extract comprising cellulose extracted from a lignocellulosic biomass.

Advantageously, the extract according to the invention makes it possible to obtain a renewable synthesis gas without pollutant and without the need for the addition of catalyst during gasification.

Surprisingly, the synthesis gas obtained from coal of the extract according to the invention comprising cellulose and residual lignin does not contain sulfur compounds and nitrogen compounds, preferably the synthesis gas does not contain polluting.

According to a preferred object of the invention, the synthesis gas according to the invention is obtained without adding a catalyst during gasification.

The synthesis gas according to the invention is particularly useful in the context of the invention, thus making it possible to overcome the disadvantages of the prior art.

Finally, the invention also relates to the use of an extract according to the invention to produce a synthesis gas.

Other characteristics and advantages will emerge from the detailed description of the invention and the examples which are purely illustrative and in no way limiting the scope of the invention. Brief description of the Figures

[Fig. 1] is a graphical representation of an embodiment presenting a process for extracting cellulose from softwood sawdust

[Fig. 2] is a graphic representation of a device making it possible to characterize the synthesis gas

Detailed description of the invention

Definition

By “biochar” within the meaning of the invention is meant a charcoal of plant origin obtained by pyrolysis of a raw material such as raw biomass or the extract according to the invention obtained from a lignocellulosic biomass.

By “biomass” within the meaning of the invention is meant all organic matter of plant or animal origin.

By “reactive species” within the meaning of the invention is meant molecules participating in chemical reactions.

By “green synthesis gas” within the meaning of the invention is meant a synthesis gas obtained from a lignocellulosic biomass.

By “gasification” within the meaning of the invention, is meant the conversion of cellulose into a gaseous product via partial oxidation at high temperature using for example air, water vapor, pure oxygen. or carbon dioxide.

By “Kappa index” within the meaning of the invention, is meant a metric of the residual lignin content of a cellulose pulp such as the solid fraction resulting from the precipitation of the cellulose according to the invention. The Kappa index estimates the quantity of bleaching agent necessary to obtain a dough with a given degree of whiteness. Since the amount of bleaching agent required is related to the lignin content of the pulp, the Kappa index can be used to control the residual lignin content of said pulp.

By “not containing sulfur compounds” within the meaning of the invention, we mean that the synthesis gas according to the invention contains a content of less than 0.01% of sulfur compounds. This sulfur content can be measured by techniques well known to those skilled in the art such as, for example, gas chromatography.

By “not containing nitrogen compounds” within the meaning of the invention, we mean that the synthesis gas according to the invention contains a content of less than 0.01% of nitrogen compounds. This pollutant content can be measured by techniques well known to those skilled in the art such as, for example, gas chromatography. When traces of nitrogen are found in the synthesis gas according to the invention, it is nitrogen resulting from the pyrogasification of cellulose. The nitrogen is then in the form of inert dinitrogen. By “non-food origin” within the meaning of the invention, we mean that the synthesis gas does not come from a raw material used in human or animal food.

By “non-fossil origin” within the meaning of the invention, we mean that the synthesis gas does not come from a raw material derived from a fossil carbonaceous material: oil, gas or coal.

By “higher calorific value (GCV)” within the meaning of the invention is meant the quantity of heat produced during its complete combustion, without taking into account the latent heat of vaporization of the water formed during the combustion reaction. The PCS is the total amount of thermal energy released per unit volume of the syngas when it is completely burned. In the context of a green syngas, a high PCS indicates that the gas contains a significant amount of thermal energy per unit volume, making it effective as a fuel for various energy applications.

By “lower calorific value (LCV)” within the meaning of the invention, is meant the quantity of heat produced during the complete combustion of a fuel or synthetic gas, taking into account the latent heat of vaporization of water. formed during the combustion reaction. The PCI represents the amount of thermal energy available per unit volume of the syngas once the heat used to vaporize the water formed is subtracted. In the context of green syngas, a high PCI means that the gas produces a significant amount of thermal energy per unit volume, making it effective as a fuel for different energy applications.

Extract

The present invention therefore relates to an extract obtained from a lignocellulosic biomass allowing, by direct pyrogasification, to obtain a green synthesis gas not containing nitrogen compounds and sulfur compounds. In the context of the invention, the extract according to the invention is a key developmental intermediate for obtaining a green synthesis gas not comprising sulfur compounds and nitrogen compounds obtained from a lignocellulosic biomass.

Thus, the invention relates to an extract obtained from a lignocellulosic biomass comprising cellulose and at least 1% of residual lignin by weight of the total weight of the extract.

Preferably, the extract according to the invention comprises at least 5%, in particular at least 10%, even more preferably at least 20% of residual lignin by weight of the total weight of the extract.

According to a preferred embodiment, the extract according to the invention comprises between 1 and 30% of residual lignin, in particular between 5 and 30%, preferably between 10 and 30% of residual lignin by weight of the total weight of the extract.

According to a variant, the extract according to the invention comprises at least 5%, in particular at least 10%, even more preferably at least 20% of lignin by weight of the total weight of the extract. Advantageously, the inventors have discovered that lignin, contrary to the teachings of the prior art, can be used for the production of a green synthesis gas without pollutant and which does not require a post-gasification purification step.

According to one embodiment, the extract according to the invention does not comprise hemicellulose and proteins.

According to another embodiment, the extract according to the invention obtained from a lignocellulosic biomass comprises a content of inorganic compounds at least 10 times lower than the content of inorganic compounds of said raw lignocellulosic biomass.

Advantageously, the lower the content of inorganic compounds, the less likely the pyrogasification of said extract is to produce pollutants.

Preferably, the extract according to the invention obtained from a lignocellulosic biomass comprises a content of at least inorganic compound chosen from calcium, potassium, magnesium, sodium, iron, phosphorus, sulfur and silica at least 10 times lower than the content of inorganic compounds in said raw lignocellulosic biomass.

According to one embodiment, the extract according to the invention does not comprise at least one inorganic compound chosen from calcium, potassium, magnesium, sodium, iron, phosphorus, sulfur and silica.

Preferably, the extract according to the invention does not comprise nitrogen compounds (ammonia, nitrogen oxides), sulfur compounds (sulphur oxides, hydrogen sulphide), chlorinated compounds (hydrochloric acid), alkaline metals earthy (potassium, sodium, magnesium, calcium), heavy metals (lead, nickel, copper, mercury, zinc) and fine particles (mineral ash, carbon particles).

Preferably, the extract according to the invention does not include inorganic compounds.

According to a particularly preferred embodiment, the extract according to the invention does not comprise silica.

Silica is an undesirable element in the context of the invention. Indeed, silica is an inhibitor of gasification reducing the production yield of synthesis gas.

Preferably, the extract according to the invention is in solid form, preferably in the form of a paste, in particular a fibrous paste.

According to one embodiment, the extract according to the invention comprises at least 80% of cellulose by weight of the total weight of the extract, preferably at least 85% by weight of the total weight of the extract.

According to one embodiment, the extract according to the invention can be obtained by a process comprising a step of treating a lignocellulosic biomass with an organic solvent.

Preferably, said organic solvent is formic acid. According to one embodiment, the extract according to the invention can be obtained by a process comprising a step of treating a lignocellus biomass with a solvent consisting of water and formic acid, preferably comprising at least 85 % by weight of formic acid.

According to another embodiment, the extract according to the invention can be obtained by a process comprising the implementation of the following steps:

1) Mixture of lignocellulosic biomass with solvent consisting of water and formic acid;

2) Separation, at atmospheric pressure and temperature of the mixture of step 1), of the solid fraction, constituting the cellulose paste, from a liquid organic phase containing in solution at least the solvent of step 1) and all undegraded molecules of lignocellulosic biomass.

Preferably, the mixture of step 1) is carried out in a lignocellulosic biomass/solvent ratio of between 1/1 and 1/15.

Preferably, the solvent of step 1) comprises at least 85% by weight of formic acid.

According to one embodiment, step 1) is carried out at a temperature of between 80°C and 100°C with a weight ratio of said solid/solvent lignocellulosic biomass of between 1/1 and 1/15, and for a period determined reaction time.

Preferably, the reaction time of step 1) is determined by measuring the Kappa index of the solid fraction until a residual lignin content of at least 1%, preferably at least 5%, is obtained, in particular 6%, 7%, 8%, 9%, 10%, even more preferably at least 20% of residual lignin by weight of the total weight of the extract.

Process for preparing an extract

The invention also relates to a process for preparing an extract according to any of the previously described embodiments.

Thus, the invention also relates to a process for preparing an extract according to the invention comprising the implementation of the following steps:

1) Mixture of a lignocellulosic biomass with a solvent consisting of water and formic acid;

2) Separation, at atmospheric pressure and temperature of the mixture of step 1), of the solid fraction, constituting the cellulose paste, from a liquid organic phase containing in solution at least the solvent of step 1) and all undegraded molecules of lignocellulosic biomass.

Advantageously, the process according to the invention makes it possible to obtain an extract comprising cellulose and a residual lignin content of between 1 and 30% by weight of the total weight of the extract.

Preferably, the extract is obtained from at least one type of lignocellulosic biomass chosen from: hardwood, softwood, cereal straw (wheat, corn, barley, rice, sorghum), bagasse from sugar plants (sugar cane). , sugar sorghum), energy plants (miscanthus, bamboo, fiber sorghum), fibrous lignocellulosic residues from agricultural production (banana trunks, pineapples, palm trees, flax, hemp) and their mixtures.

According to a particular embodiment of the invention, the cellulose is extracted from at least 2 types of biomass, in particular at least 3 types of biomass.

According to one embodiment, the solvent of step 1) comprises at least 85% by weight of formic acid.

Advantageously, formic acid makes it possible to precipitate the cellulose without degrading it, thus forming a cellulose paste comprising in particular cellulose and lignin.

Preferably, the mixture of step 1) is carried out in a lignocellulosic biomass/solvent ratio of between 1/1 and 1/15.

According to one embodiment, step 1) is carried out at atmospheric pressure and under controlled reaction temperature conditions between ambient temperature and the reflux temperature of the mixture at atmospheric pressure.

According to another embodiment, step 1) is carried out at a temperature between 80°C and 100°C with a weight ratio of said solid/solvent lignocellulosic biomass between 1/1 and 1/15, and for a fixed period of reaction time.

Preferably, the reaction time of step 1) is determined by measuring the Kappa index of the solid fraction formed during the reaction of step 1) until a residual lignin content of at least least 1%, in particular at least 5%, preferably at least 10%, even more preferably between 1 and 30% by weight of the total weight of the solid fraction.

According to one embodiment, the method according to the invention also comprises the implementation of the following step:

3) Washing of the solid fraction obtained in step 2) comprising at least one washing, at room temperature, using a solution comprising water and formic acid in which the formic acid presents a concentration of at least 80%; and washing between 40 and 60°C with hot water.

Advantageously, washing step 3) makes it possible to reduce the lignin content and the content of inorganic compounds present in the solid fraction obtained in step 2).

According to a particular embodiment of the invention, the process can also comprise a step 4) of treating the solid fraction in an alkaline medium.

Advantageously, step 4) can be used to reduce the content of inorganic compounds in the solid fraction resulting from step 2) or 3).

Thus, according to one embodiment, the process for preparing an extract according to the invention comprises the implementation of the following steps:

1) Mixture of a lignocellulosic biomass with a solvent consisting of water and formic acid; 2) Separation, at atmospheric pressure and temperature of the mixture of step 1), of the solid fraction, constituting the cellulose paste, from a liquid organic phase containing in solution at least the solvent of step 1) and all undegraded molecules of lignocellulosic biomass; And

3) Washing of the solid fraction obtained in step 2) comprising at least one washing, at room temperature, using a solution comprising water and formic acid in which the formic acid presents a concentration of at least 80%; and washing between 40 and 60°C with hot water.

Synthetic gas

The present invention also relates to a synthesis gas not containing nitrogen compounds and sulfur compounds and obtained from a renewable raw material, cellulose.

Thus, the invention relates to a synthesis gas obtained from cellulose not containing nitrogen compounds and sulfur compounds, characterized in that the synthesis gas is of non-food and/or non-fossil origin.

According to a preferred embodiment, the synthesis gas according to the invention is obtained from the extract according to the invention.

Preferably, said synthesis gas does not contain tar, nitrogen compounds (ammonia, nitrogen oxides), sulfur compounds (sulfur oxides, hydrogen sulfide), chlorinated compounds (hydrochloric acid), alkaline metals earthy (potassium, sodium, magnesium, calcium), heavy metals (lead, nickel, copper, mercury, zinc) and fine particles (mineral ash, carbon particles).

Preferably, the synthesis gas according to the invention does not contain any reactive species containing nitrogen or sulfur.

According to a particular embodiment of the invention, the invention relates to a synthesis gas, consisting exclusively of carbon monoxide (CO), carbon dioxide (CO2), dihydrogen (H2) and methane (CH4 ).

According to another particular embodiment of the invention, the synthesis gas comprises carbon monoxide (CO), carbon dioxide (CO2), dihydrogen (H2) and methane (CH4) and does not contain compounds nitrogen and sulfur compounds.

According to one embodiment of the invention, at least part of the synthesis gas is obtained from cellulose tar.

The quality and stability of the cellulose mean that the synthesis gas according to the invention preferably comprises:

-between 50 and 60% by volume of H2;

-between 30 and 40% by volume of CO; -between 7 and 12% by volume of CO2; And

-between 0.4 and 1% by volume of CH4.

According to a preferred embodiment of the invention, the synthesis gas consists of:

-between 50 and 60% by volume of H2;

-between 30 and 40% by volume of CO;

-between 7 and 12% by volume of CO2; And

-between 0.4 and 1% by volume of CH4.

Advantageously, the synthesis gas according to the invention has a yield, a volume, a lower calorific value and an H2/CO ratio (volume/volume) similar to a synthesis gas obtained from raw lignocellulosic biomass. More particularly, the synthesis gas according to the invention has variations in yield, volume, lower calorific value and H2/CO ratio (volume/volume) less than 5%, preferably less than 2% compared to a gas synthesis obtained from raw biomass.

Preferably, the synthesis gas according to the invention comprises an H2/CO volume/volume ratio of between 1.5 and 3.

Advantageously, the H2/CO ratio of the synthesis gas according to the invention is similar to a synthesis gas obtained from raw lignocellulosic biomass.

Preferably, the synthesis gas according to the invention comprises an H2/CO volume/volume ratio of between 1.5 and 3, and comprises a CH4 content between 0.4 and 1%.

According to a particular embodiment of the invention, the synthesis gas comprises at least one ratio chosen from:

- an H2/CO volume/volume ratio of between 1.5 and 3;

- an H2/CO2 volume/volume ratio of between 3.5 and 6.5; And

- a CO/CO2 volume/volume ratio of between 1.5 and 4.5.

According to a particularly preferred embodiment, the synthesis gas according to the invention is obtained without using a catalyst, in particular during gasification.

Unexpectedly, the inventors succeeded in producing a synthesis gas adding catalyst during gasification.

Advantageously, the synthesis gas according to the invention has a low production cost and is suitable for large-scale production.

Preferably, the synthesis gas according to the invention is obtained according to a manufacturing process comprising the following steps: a) Recovery of cellulose extracted from a lignocellulosic biomass b) Pyrolysis of cellulose obtained in step a); c) Gasification of the biochar obtained in step b) without adding catalyst.

According to a preferred embodiment, the synthesis gas according to the invention is obtained according to a manufacturing process comprising the following steps: a) Pyrolysis of the extract according to the invention; and b) Gasification of the char obtained in step a) without adding catalyst.

Process for manufacturing synthesis gas from the extract according to the invention

Also, according to another aspect, the invention relates to a manufacturing process comprising the following steps: a) Pyrolysis of the extract according to the invention; and b) Gasification of the char obtained in step a) without adding catalyst.

The process according to the invention advantageously makes it possible to produce a synthesis gas not containing sulfur compounds and nitrogen compounds, preferably not containing inorganic compounds.

Preferably, pyrolysis step a) is carried out at a maximum temperature of between 750 and 950°C, preferably 850°C, for a period of between 0.5 and 1.5 hours, preferably 1 hour.

Preferably, the pyrolysis is carried out by increasing the temperature constantly, in particular between 10 and 30°C per minute, very preferably 20°C per minute.

According to a preferred embodiment, the pyrolysis is carried out by injecting a continuous flow of dinitrogen, preferably a flow rate of between 30mL/min and 20L/min.

The gasification of step b) is preferably gasification with water vapor.

Advantageously, steam gasification makes it possible to increase the production of hydrogen in the synthesis gas.

Steam gasification is preferably carried out by injecting a steam/carbon mass ratio between 1 and 3 at a temperature between 850 and 1000°C, preferably between 900 and 975°C, even more preferably 950°C.

When the gasification temperature is 950°C, the synthesis gas thus formed after gasification step c) has a lower calorific value and an H2/CO ratio (volume/volume) equivalent to a synthesis gas obtained from of raw biomass.

More particularly, the synthesis gas obtained after gasification step b) has variations in yield, volume, lower calorific value and H2/CO ratio (volume/volume) of less than 5%, preferably less than 2%. compared to a synthesis gas obtained from raw biomass. Preferably, the undegraded molecules of the lignocellulosic raw material are monomeric and oligomeric hemicellulose sugars, lignin oligomers, trace elements in ionic form (sources of sulfur, nitrogen, inorganic and metallic elements), tannins, proteins (nitrogen sources) and extractables from the lignocellulosic raw material considered.

Process for manufacturing a synthesis gas from cellulose

According to an alternative subject, the invention relates to a process for manufacturing a synthesis gas comprising the implementation of the following steps: a) Recovery of cellulose extracted from a lignocellulosic biomass; b) Pyrolysis of the cellulose obtained in step a); and c) Gasification of the biochar obtained in step b) without catalyst.

The cellulose from step a) can be extracted from a lignocellulosic biomass by any means.

According to a preferred embodiment of the invention, the cellulose extracted from a lignocellulosic biomass of step a) is in the form of fibrous cellulose pulp and comprises at least 60% cellulose, preferably at least 75%, in particular at least 80%, even more preferably at least 95%.

Preferably, pyrolysis step b) is carried out at a maximum temperature of between 750 and 950°C, preferably 850°C, for a period of between 0.5 and 1.5 hours, preferably 1 hour.

Preferably, the pyrolysis is carried out by increasing the temperature constantly, in particular between 10 and 30°C per minute, very preferably 20°C per minute.

According to a preferred embodiment, the pyrolysis is carried out by injecting a continuous flow of dinitrogen, preferably a flow rate of between 30mL/min and 20L/min.

The gasification of step c) is preferably gasification with water vapor.

Advantageously, steam gasification makes it possible to increase the production of hydrogen in the synthesis gas.

Steam gasification is preferably carried out by injecting a steam/carbon mass ratio between 1 and 3 at a temperature between 850 and 1000°C, preferably between 900 and 975°C, even more preferably 950°C.

When the gasification temperature is 950°C, the synthesis gas thus formed after gasification step c) has a lower calorific value and an H2/CO ratio (volume/volume) equivalent to a synthesis gas obtained from of raw biomass. More particularly, the synthesis gas obtained after gasification step c) presents variations in yield, volume, lower calorific value and H2/CO ratio (volume/volume) less than 5%, preferably less than 2% compared to a synthesis gas obtained from raw biomass.

Preferably, the cellulose from step a) is extracted from a lignocellulosic biomass by an extraction process comprising the following steps:

A') Place at least one solid lignocellulosic raw material in the presence of a mixture composed solely of water and formic acid;

B') separate, at atmospheric pressure and at said reaction temperature, a solid fraction, constituting the cellulose paste, from a liquid organic phase containing in solution at least the starting mixture of formic acid and water and all undegraded natural molecules of the lignocellulosic raw material.

Thus, according to a preferred embodiment, the invention relates to a process for manufacturing a synthesis gas comprising the following steps:

Optionally:

A') Place at least one solid lignocellulosic raw material in the presence of a mixture composed solely of water and formic acid;

B') Separate, at atmospheric pressure and at said reaction temperature, a solid fraction, constituting the cellulose paste, from a liquid organic phase containing in solution at least the starting mixture of formic acid and water and all undegraded natural molecules of the lignocellulosic raw material;

B") Regularly measure or determine the Kappa index of the cellulose pulp during the determined reaction time period to identify the stabilization of the Kappa index of the extracted cellulose which can also be classified as crude cellulose pulp;

C') said raw cellulose pulp is washed successively in two stages with:

- C'1) a solution composed of water and formic acid with a concentration of formic acid in said solution of between 80% and 100%, at room temperature; And

- C'2) with hot water between 40°C and 60°C; a) Recovery of cellulose extracted from lignocellulosic biomass; b) Pyrolysis of the cellulose obtained in step a); and c) Gasification of the biochar obtained in step b) without catalyst.

Advantageously, step A') makes it possible to extract lignins, hemicelluloses and other constituents from the lignocellulosic biomass, with the exception of cellulose. Preferably, the undegraded natural molecules of the lignocellulosic raw material are monomeric and oligomeric hemicellulose sugars, lignin oligomers, trace elements in ionic form (sources of sulfur, nitrogen, inorganic and metallic elements), tannins, proteins (nitrogen sources) and extractables from the lignocellulosic raw material considered.

Preferably, step A') is carried out at atmospheric pressure and under controlled reaction temperature conditions between ambient temperature and the reflux temperature of the mixture at atmospheric pressure.

Preferably, step A') is carried out at a temperature between 80°C and 100°C, in particular 85°C, with a weight ratio of said at least one solid lignocellulosic raw material/liquid mixture of between 1/1 and 1/15, in particular between 1/4 and 1/6 and for a specific period of reaction time.

Preferably, the mixture of water and formic acid of step A') comprises a formic acid concentration of between 50% and 100%, preferably between 80% and 90%.

The cellulose extraction process preferably comprises an additional step after step B') consisting of washing the raw cellulose.

Advantageously, washing the cellulose makes it possible to have a homogeneous raw material that is clean and free from sources of pollutants for the gasification operation.

Thus, in a step C'), said raw cellulose pulp can be washed successively in two steps with:

- C'1) a solution composed of water and formic acid with a concentration of formic acid in said solution of between 80% and 100%, at room temperature; And

- C'2) with hot water between 40°C and 60°C;

Optionally, a centrifugation step at room temperature can be carried out between said first washing step C'1) and step C'2) with hot water; another centrifugation step can also be carried out step C'2).

Advantageously, centrifugation makes it possible to effectively separate the solid cellulosic phase from the liquid phase.

Separation step B') can therefore be carried out by centrifugation or filtration, preferably at atmospheric pressure for a reaction time t;

The reaction time t depends on the measured or determined Kappa index of the cellulose pulp obtained in step B'); According to one embodiment, the reaction is stopped when the Kappa index of the cellulose pulp reaches a stabilized value depending on the nature of at least one lignocellulosic raw material. Thus, the method may comprise a step B”) consisting of regularly measuring or determining the Kappa index of the cellulose pulp during the reaction time period determined to identify the stabilization of the Kappa index of the extracted cellulose which can also be described as crude cellulose pulp;

Preferably, step B”) consists of regularly measuring or determining the Kappa index of the cellulose pulp every ten minutes.

The reaction is stopped when the Kappa index of the cellulose pulp is stabilized after at least three consecutive measurements or determinations.

Uses:

According to a final aspect, the invention relates to the use of an extract according to the invention to produce a synthesis gas, in particular without nitrogen compounds and sulfur compounds.

More particularly, the extract according to the invention can be used to produce hydrogen and green carbon dioxide. In fact, these natural gases will be recycled via the carbon cycle without impacting their atmospheric concentrations.

Preferably, the synthesis gas according to the invention is particularly suitable for use as a raw material for the production of existing and renewable fuels according to the well-known Fischer - Tropsch reaction, in particular for flying planes or powering cars, trucks. , boats, trains and other types of existing mobility

Advantageously, the synthesis gas according to the invention has remarkable quality allowing it to be used in numerous applications depending on the gas of interest (CH4, CO, CO2, H2).

The invention is now illustrated by examples.

Example 1: Comparative test of the process according to the invention

Selection of lignocellulosic raw material

Wheat straw (WS) and softwood fir sawdust (SS) were chosen as lignocellulosic biomass samples for the cellulose extraction and pyrogasification experiments.

A commercial cellulose in the form of Arbocell cellulose fibers (ARC) was also used.

Characterization of properties

The physio-chemical properties of the selected materials, extracted cellulose and pyrogasification coal were characterized.

A) Proximity analysis

Proximity analysis helps determine product distribution when samples are heated under specific conditions. Proximity analysis includes the determination of several parameters such as humidity, volatile matter, ash and fixed carbon. The first three parameters were determined in accordance with the standards EN ISO 18134-3 [ISO 18134-32015], EN ISO 18123 [ISO 181232015], and EN ISO 18122 [ISO 181222015]. The measurements were carried out in triplicate. The fixed carbon was calculated by making the difference:

Total mass = moisture + ash + volatile matter + fixed carbon

[Table 1]

Cellulose contains more volatile matter than different types of raw biomass. This can be explained by the separation of part of the lignin.

The ash rate is similar between samples due to silica precipitation.

B) Ultimate Analysis

The quantification of the mass fractions of carbon (C), hydrogen (H), nitrogen (N) was obtained by CHNS analysis using a Themoquest NA 2000 elemental analyzer. Three repetitions of the analysis were was carried out according to standard EN ISO 16948:2015 [ISO2015], The mass fraction of oxygen was calculated by difference:

Total mass = C + H + N + S + O

[Table 2]

It is observed that the H/C and O/C ratios are similar for the biomass and extracted cellulose samples.

Cellulose samples (extracted) contain a low content of nitrogen resulting from their production process. In fact, this is a residual content due to the injection of dinitrogen.

The nitrogen content is different between biomass samples and cellulose samples. Cellulose (extracted or commercial) has a low or even zero nitrogen content.

C) Analysis of the higher calorific value (GCV)

The gross calorific value was determined using an automated oxygen bomb calorimeter (IKA C 5000).

Approximately 400 mg of the sample powder was pressed to produce a tablet. The tablet was placed in the crucible which, in turn, was enclosed in the calorimeter bomb to undergo complete combustion. The PCS value was calculated by the bomb calorimeter.

[Table 3]

The higher calorific value is directly proportional to the lignin content in the sample. Thus, the greater the PCS, the greater the lignin content in the sample. We see here that the cellulose samples (extracted or commercial) have a lower PCS than the biomass samples. The samples used for this example include residual lignin contents of between 1 and 30% by weight of the sample.

Measurement of inorganic composition:

Quantitative analysis:

The identification and quantification of mineral species were carried out using Coupled Plasma Optical Emwassion Spectroscopy (ICP-OES). Before the analysis, complete digestion of the solid was carried out using acidic reagents, as described in Pham Minh, D. et al. (2020).

150 mg of dried and ground solid sample was placed in a closed PTFE Teflon container.

1.5 ml of H202, 4 ml of HNO3, and 0.5 ml of HF were added. The system was heated at 220 °C for 1 h and 8 h for the feedstock and biochar, respectively. The resulting acidic solution was then diluted with deionized water to 50 ml. Finally, the solution was analyzed using a HORIBA Jobin Yvol Ultima 2 ICP-OES.

Extraction de la cellulose à échelle pilote (Figure 1) : [Table 4]

Cellulose extraction on a pilot scale (Figure 1):

Softwood sawdust (SS) was dried at 40°C for 48 hours.

40.2 kg of SS were extracted in the ROSENMUND RoLab 0.4 m2 pilot filter/dryer.

Before acid cooking, the biomass was dried in a ventilated oven for 5 hours at 70°C (30% air change), in order to achieve the highest possible dry matter content. The final dry matter was 97.8% by weight.

1. Acid cooking / Filtration

14kg of biomass were loaded into the tank equipped with the 120pm filtration cloth

The equipment was closed, then the remaining 26.2 kg were introduced by suction. On the 40.2 kg of total biomass, a formic acid ratio 85% by weight/biomass of 5:1 weight/weight, Agitation started at 30 RPM and the jacket was heated to 90°C. After 3 h, the temperature of the reaction medium (MR) reached 85°C. This temperature was maintained for 4.5 hours before cooling the reaction medium (observation of black coloring). Agitation was then slowed to 7 RPM overnight and the next morning an overpressure of 1.5 barg was applied to filter the liquor. The filtrate was stored in a 200 liter plastic barrel.

2. Acid Washing/Filtration

103.6 kg of formic acid were introduced onto the cellulose retained on the filter on two occasions.

36.4 kg and 67.2 kg of the acid solvent were added for the first and second rounds, respectively. For each addition, the cellulose in contact with the acid mixture was stirred for 5 min then filtered at 1.5 barg on a 120 pm cloth. The filtered acidic liquors were stored in containers.

3. Water washing / Filtration

The water washes were carried out in 3 times. Around 200 L of hot water (60°C) were introduced into the Rolab each time. The mixture was stirred for 5 min and then filtered at 1 barg through a 120 µm filter cloth. All filtrates were collected in a single storage.

4. Drying

After washing the cellulose, the filtration tank was opened and the resulting cellulose was placed in the tank.

The drying tank has a larger heat exchange surface.

The drying conditions were set at 70°C, with stirring at 25 RPM and with a vacuum of 50 mbar in order to obtain a weight around 90% of the weight before drying.

The cellulose thus extracted on a pilot scale from softwood sawdust will be called “Cell-SS-P”.

5. Pyrolysis

During the experiment, 90 g of the sample was heated to the sample was heated at a heating rate of 20°C/min to complete the pyrolysis step. After reaching 950°C, the reactor was kept under an inert atmosphere for 15 minutes.

Dinitrogen was used as a carrier gas to provide an inert atmosphere with a flow rate of 3.5 L/min.

6. Gasification

The gasification step was carried out in the same reactor.

After that, the steam is injected continuously (isothermal for 1 hour) with nitrogen to constitute a mixture comprising 60% by volume. At the end of the gasification stage experiment, the heater was turned off and the atmosphere switched to nitrogen until room temperature was reached. Product characterization

Gas characterization:

Non-condensable gases were sampled upstream of the condensation train (Figure 2).

A gas meter was added to measure the volume of combustion gases. The concentration of H2, N2, CH4, CO, CO2 and C2Hn was examined by gas chromatography (micro GV-3000A, agilent).

The flow rate of permanent gases in the produced gas was calculated from the composition of the gas analyzed and the material balance.

A) Raw biomass: softwood fir sawdust (SS) [Table 5]

Hydrogen is the largest volume fraction. We can see the effect of adding water vapor on the quality of the gas (H2/CO) by increasing the hydrogen concentration.

B) Cellulose extracted on a pilot scale from resinous fir sawdust (Cell - SS -P)

Caractérisation du goudrons : [Table 6]

Characterization of tars:

The condensable liquid, including the tar, was recovered by the condensation train placed upstream of the heated line (Figure 2). The packaging unit was adapted from the tar protocol (CEN BT/TF 143) Good, 2005 using 6 impinger bottles containing iso-propanol. First two bottles were placed at room temperature. Three other impactors were placed in a bath cooled to approximately -20°C. The last one is lined with silica gel in order to trap the last traces of water and to protect the impactors from the last traces of water and to protect the micro-GC. The mass of iso-propanol remained constant for each experiment.

For pyrolysis tests, the condensables are composed of water and tar. The water content was immediately determined by the Karl Fischer method using the V30 volumetric titrator (METTLER TOLEDO). The mass of the analyzed sample (iso-propanol + condensables) was approximately 0.5 g, where HYDRANAL 5 composite and dry methanol were used as titrant and solvent respectively.

The flow rate of permanent gases in the produced gas was calculated from the composition of the gas analyzed and the material balance. It was calculated based on the N2 inlet flow rate and its mole fraction in the produced gas:

Product gas flow = N2/YN2 flow - N2 flow

Where Y NN2 is the volume fraction of N2 in the gas mixture

The mass flow rate of the gas produced is calculated by the product of the density of the gas and its volume flow rate.

Carbon conversion was used to show that there are no tars produced during the gasification stage of the char from the pyrolysis stage. In other words, the carbon balance of the reaction is calculated to demonstrate the presence or absence of tars.

The carbon conversion in the char was calculated by determining the carbon content in the gasified char and the retained char at the end of the gasification stage.

Xtotal= Cc+ Cgas + C tar

Total XC = (mchar entered *%Cchar entered - mretained* %Cchar retained)/ (mchar entered * %Cchar entered)

The determination of the carbon conversion in the produced gas was carried out by the following equation:

XC gas = (Gas volume produced * 12/22.4)*(%CH4 + % CO + CO2) / (mchar entered * %Cchar entered)

Gas XC values are similar to total Xc; which seems to show that there is no production of tar.

Characterization of tanks

The physicochemical characterization of pyrolysis and gasification residues was analyzed using the following methods

Analytical techniques include: ultimate and proximal analysis, ICP-OES, SEM-EDX, and TEM-EDX.

A) Raw biomass: Softwood fir sawdust (SS) [Table 7]

B) Cellulose extracted on a pilot scale from resinous fir sawdust (Cell - SS -P) [Table 9]

Gasification at 950°C converts a high amount of the carbon and steam in syngas into hydrogen.

All of these results clearly show the potential of using cellulose extracted from biomass to produce a pollutant-free synthesis gas, presenting a gas yield, a calorific value and an H2/CO ratio similar to those of natural gas. synthesis obtained directly from biomass.

Example 2: Comparative test of process according to the invention

The process according to the invention, used in this example, is as follows: a) Recovery of a raw material:

- raw biomass: resinous fir sawdust (SS)

- Cellulose extracted from coniferous fir sawdust Cell-SS-P

- Commercial cellulose (Arbocel ARC) b) Pyrolysis of the raw material extracted in step A)

Pyrolysis is carried out at room temperature, increasing the temperature by 20°C/min until reaching 950°C. The temperature increment is carried out under injection of nitrogen with a continuous flow rate of 3.5 L/minute. c) Gasification of the biochar from the raw material at 950°C by injecting 45% water vapor for 1 hour.

Comparison of the synthesis gases obtained:

[Table 11]

In addition to the advantage of containing less pollutant, the synthesis gas according to the invention has a hydrogen yield from the gasification of cellulose similar to that of biomass.

Claims

Claims [Claim 1] Extract obtained from a lignocellulosic biomass comprising cellulose and at least 1% residual lignin by weight of the total weight of the extract. [Claim 2] Extract according to the preceding claim, characterized in that it does not include hemicellulose or proteins. [Claim 3] Extract according to the preceding claim, characterized in that it does not include silica. [Claim 4] Extract according to one of the preceding claims, characterized in that it does not include nitrogen compounds and sulfur compounds. [Claim 5] Extract according to one of the preceding claims, characterized in that it comprises: - at least 80% cellulose by weight of the total weight of the extract. [Claim 6] Extract according to one of the preceding claims, characterized in that it is in the form of a paste, preferably in the form of a paste. [Claim 7] Extract according to one of the preceding claims, characterized in that it is obtained by a process comprising a step of treating a lignocellulosic biomass with an organic solvent. [Claim 8] Extract according to one of claims 1 to 6, characterized in that it is obtained by a process comprising the implementation of the following steps: 1) Mixture of a lignocellulosic biomass with a solvent consisting of water and formic acid; 2) Separation, at atmospheric pressure and temperature of the mixture of step 1), of the solid fraction, constituting the cellulose paste, from a liquid organic phase containing in solution at minus the solvent from step 1) and all the non-degraded molecules of the lignocellulosic biomass; [Claim 9] Process for preparing an extract according to one of the preceding claims, characterized in that it comprises the implementation of the following steps: 1) Mixture of a lignocellulosic biomass with a solvent consisting of water and formic acid; 2) Separation, at atmospheric pressure and temperature of the mixture of step 1), of the solid fraction, constituting the cellulose paste, from a liquid organic phase containing in solution at least the solvent of step 1) and all undegraded molecules of lignocellulosic biomass. [Claim 10] Process according to the preceding claim, characterized in that the solvent of step 1) comprises at least 85% by weight of formic acid. [Claim 11] Method according to one of claims 9 or 10, characterized in that step 1) is carried out at atmospheric pressure and under controlled reaction temperature conditions between ambient temperature and the reflux temperature of the mixture at atmospheric pressure. [Claim 12] Method according to one of claims 9 to 11, characterized in that step 1) is carried out at a temperature between 80°C and 100°C with a weight ratio of said solid/solvent lignocellulosic biomass included between 1/1 and 1/15, and for a specific period of reaction time. [Claim 13] Method according to one of claims 9 to 12, characterized in that the reaction time of step 1) is determined by measuring the Kappa index of the solid fraction formed during the reaction of step 1) until a lignin level of at least 5% by weight of the total weight of the solid fraction is obtained. [Claim 14] Method according to one of claims 9 to 13, characterized in that it also comprises the implementation of the following steps: 3) Washing the solid fraction obtained in step 2) comprising at least one washing, at room temperature, using a solution comprising water and formic acid in which the formic acid presents a concentration of at least 80%; and washing between 40 and 60°C with hot water. [Claim 15] Process for manufacturing a synthesis gas from an extract according to one of claims 1 to 8, comprising the implementation of the following steps: a) Pyrolysis of the extract obtained from a lignocellulosic biomass according to one of claims 1 to 8; and b) Gasification of the char obtained in step a) without adding catalyst. [Claim 16] Process for manufacturing a synthesis gas according to the preceding claim, characterized in that the pyrolysis step of step a) is carried out at a maximum temperature of between 750 and 950°C for a duration of between 0.5 and 1.5 hours. [Claim 17] Process for manufacturing a synthesis gas according to one of claims 15 or 16, characterized in that the gasification of step b) is a water vapor gasification. [Claim 18] Process for manufacturing a synthesis gas according to the preceding claim, characterized in that the steam gasification is carried out by injecting a steam/carbon mass ratio between 1 and 3 at a temperature between 850 and 1000° vs. [Claim 19] Use of an extract obtained from a lignocellulosic biomass according to one of claims 1 to 8 to produce a synthesis gas. [Claim 20] Use according to the preceding claim, to produce hydrogen and/or carbon dioxide.