ES2526259B1 - PROCEDURE FOR OBTAINING AN ADSORBENT THAT USES POST-CONSUMPTION COFFEE WASTE AND ITS USE FOR CO2 ADSORTION - Google Patents

Abstract

Method of obtaining an adsorbent using post-consumer coffee waste and its use for the adsorption of CO {sub, 2}. # The present invention relates to a process for obtaining an adsorbent material capable of adsorbing CO {sub, 2 }, which uses post-consumer coffee waste. The process for obtaining comprises drying the residue, its conformation, in the absence of binders, and its thermal activation in the presence of an activating agent, which is preferably CO {sub, 2}. The textural and density characteristics of the material obtained by the process of the invention, which is also protected, make it an ideal candidate for the adsorption of CO {sub, 2}, and preferably in the capture of CO {sub, 2} post combustion

Description

DESCRIPTION

Procedure for obtaining an adsorbent that uses post-consumer coffee waste and its use for CO2 adsorption.

Technical sector 5

The present invention has to do with a method of obtaining an adsorbent, obtained from post-consumer coffee waste, with potential application in gas separation processes by adsorption, especially useful for the capture of CO2 after combustion, and therefore It is located in the energy sector (electricity production) and industrial (cement industry, metallurgical industry, petrochemical industry, 10 etc.) large CO2 emitter.

State of the art

Post-combustion CO2 capture (CCP) refers to the separation of CO2 present in chimney gases from large stationary sources, such as thermal power plants and 15 industrial facilities, to store it safely in geological formations, preventing its emission into the atmosphere, and thus contributing to the mitigation of CO2 emissions. There are different technologies capable of carrying out this separation. Absorption with amines has been used in industry since 1930 to carry out similar separations, although on a smaller scale. However, there are still no commercial units 20 of CCP, due to both the magnitude of the problem and the high energy penalty of chemical absorption processes, since it is necessary to heat high volumes of dilute solutions of amines to achieve their regeneration. In adsorption processes with solids, the regeneration of the adsorbent is carried out by means of a change in the pressure and / or temperature of the system (PSA / TSA). This regeneration is energetically much less intensive, so the application of adsorption processes to the CCP is expected to contribute significantly to reducing its costs.

Activated carbons have good properties as adsorbents for CCP due to their low cost, availability, high stability under chimney gas conditions 30, high CO2 / N2 selectivity, and easy regeneration. There are some patented processes where activated carbons are used to separate CO2 from gaseous mixtures by adsorption processes: US4726815 describes a PSA process for adsorption and separation of CO2 from gaseous mixtures with a CO2 content equal to or greater than 10% and US2010 / 0242728A1 describes a process for separating CO2 from a gas mixture, which consists in bringing the gas into contact with a

carbonaceous adsorbent, capable of adsorbing CO2 at temperatures close to (or below) room temperature, and of releasing CO2 by heating, pressure reduction, or a combination of both.

Activated carbons can be obtained from precursors with a high content of 5 carbon and a low content of inorganic matter. The most used precursors at the industrial level are coal, coke, peat, wood and coconut shell. Biomass is a renewable source, so its use as a raw material is expected to increase over time. Obtaining activated carbons and molecular carbon sieves from biomass is widespread: Ioannidou and Zabaniotou, 2007, 10 Renew Sustainable Energy Rev, 2007, 11, p: 1966-2005; Mohamed et al., Renew Sustainable Energy Rev, 2010, 14, p: 1591-1599.

Coffee is an important source of waste: both in origin, during coffee processing (pulp, peel, etc.), and in the final destination (for every kg of green coffee, 15 0.65 kg of waste is generated. coffee out of stock) In addition, about 50% of the coffee produced worldwide is destined for the production of soluble coffee, which generates about 2 kg of waste of spent coffee per kg produced (Murthy and Naidu, Resour Conserv Recy, 2012, 66, p: 45-58). This waste of spent coffee (referred to hereinafter as post-consumer coffee) is deposited in landfills along with other municipal solid waste, or they are used as fuel in boilers or used for the manufacture of compost. However, in accordance with the hierarchy of waste established in article 8 of law 22/2011, of July 28, on contaminated waste and soil, recycling is a priority over energy recovery or disposal. Among the possibilities of recycling this waste, we find obtaining activated carbons, which are a product with high added value. In the prior art, production history of activated carbon from coffee residues by chemical activation with KOH, ZnCl2, H3PO4, and carbonates can be found: Evans et al. Carbon, 1999, 37, p: 269-274; US2003 / 0196954A1; Namane et al. J Hazard Mater, 2005, 119, p: 189-194; Boonamnuayvitaya et al. Sep Purif Technol, 2005, 42, p: 159-168; Reffas et al. J Hazard Mater, 2010, 175, p: 779-788; Plaza et al. Appl Energ, 30 2012, 99, p: 272-279; Kante et al. J Hazard Mater, 2012, 201–202, p: 147. There are also references to the production of activated carbon from post-consumer coffee waste by physical activation in two stages, consisting of a carbonization in an N2 atmosphere followed by activation with CO2 or H2O: Tsunoda et al. J. Colloid Interface Sci., 1998, 205, p: 265-270. The proposed applications for these coals are diverse, although 35

Liquid phase adsorption predominates: formaldehyde adsorption, phenol and removal of aqueous stream dyes (methylene blue and red (N-2RBL).

Activated carbons obtained directly by activation of post-consumer coffee waste, have a particle size too fine for fixed bed applications, 5 although they can be used in discontinuous processes, especially for liquid phase adsorption processes. Obtaining granular activated carbons, suitable for fixed bed operations, requires a previous stage of forming. This stage, in many cases, involves the use of binding agents (breas, for example), which can block access to micropores, reducing the adsorption capacity of the final product. However, post-consumer coffee residues have the peculiarity that they can be shaped without the aid of binders.

Brief Description of the Invention

The technical problem to be solved is the adsorption of CO2, and preferably the capture of CO2 after combustion, which refers to the separation of CO2 present in chimney gases from large stationary sources, such as thermal power plants and industrial facilities, to store it in a way safe in geological formations, avoiding their emission into the atmosphere, and thus contributing to the mitigation of CO2 emissions. The CCP is expected to contribute significantly to the fight against climate change in the medium term. However, there are still no commercial units of CCP, due to both the magnitude of the problem and the high energy penalty of available technologies. The use of the adsorbent object of this invention in a process of CO2 separation by adsorption could significantly reduce the costs of the CCP.

 25

The first object of the invention is a process for obtaining a microporous adsorbent material derived from a post-consumer coffee residue, which comprises the following steps:

a) drying of post-consumer coffee residue to reduce its initial moisture content, 30

b) formed, in the absence of binders, of the post-consumer coffee residue obtained according to step (a), and

c) activation of the post-consumer coffee residue obtained according to step (b) by heat treatment using an activating agent.

 35

A second object of the invention is the adsorbent material obtained through the aforementioned method of obtaining and characterized by:

 i) an apparent density between 0.400 g cm-3 and 1,000 g cm-3,

ii) a micropore volume of at least 0.2 cm3 g-1,

iii) an average micropore size of less than 1 nm, and 5

iv) a CO2 adsorption capacity between 0.5 and 2.0 mmol g-1 at 14 kPa and at temperatures between 0 and 50 ˚C.

The third object of the invention is the use of the material for the adsorption of CO2, and preferably in the capture of CO2 after combustion, through the following steps:

a) contacting the gas to be treated with the adsorbent material to separate the CO2; Y

b) regenerate the adsorbent material, recovering the previously captured CO2.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is based on the observation that a process that uses a post-consumer coffee residue as a low-cost carbonaceous precursor, and which consists in subjecting said precursor to a forming process in the absence of binders, and subsequently to a heat treatment of activation with CO2 (see Examples 1 and 2), surprisingly, allows to obtain an adsorbent formed with better textural properties (see Example 5) and with greater CO2 adsorption capacity (see Example 6) than a non-formed adsorbent obtained by a similar procedure (see Example 3).

The high adsorption capacity of CO2 at low partial pressures (see Example 7), characteristics of post-combustion systems, of the adsorbent obtained by the above-mentioned procedure 25, together with its high selectivity of equilibrium towards CO2 over N2, which has been corroborated through adsorption experiments with binary CO2 / N2 mixtures (see Example 8), as well as its ease of regeneration (see Examples 8.2 and 9), they make it an ideal material for the capture of CO2 after combustion by adsorption.

 30

The main advantages of the process of obtaining, of the material obtained and of its use for the adsorption of CO2, preferably in the capture of CO2 after combustion, are listed below:

a) with respect to the procedure for obtaining:

- it is simple and economical, since part of a residue does not require the use of binders 35 during forming, nor does it require the carbonization stage prior to the stage of

material activation, which is conventionally used in the manufacture of other adsorbent carbonaceous materials,

- allows its preparation on an industrial scale,

- it is respectful with the Environment, in comparison, for example, with chemical activation processes, which require the use of chemical agents and washing processes to eliminate them, and

- It is an alternative for recovery of a very abundant residue, such as post-consumer coffee;

b) with respect to the material obtained:

- has a high apparent density, 10

- it has a particle size that can be adjusted to the characteristics of the final application,

- it has a high volume of micropores, with a narrow distribution of them,

- it has a high CO2 adsorption capacity, especially at low partial pressures, even at temperatures between 25 and 50 ˚C, which can be considered typical of post-combustion processes,

- it has high equilibrium selectivity towards CO2 over N2 (main component of post-combustion mixtures),

- has high stability, 20

- allows easy regeneration, and

- it has a lower carbon footprint than other adsorbents, since it uses biomass as a precursor (it has captured CO2 from the atmosphere during its growth);

c) with respect to the use in adsorption of CO2:

- allows its use in post-combustion CO2 capture processes through adsorption, which have a lower cost than absorption technologies,

- it has very good properties to be used as a CO2 adsorbent when the partial pressure of CO2 in the gas mixture to be separated is reduced,

- can be easily regenerated by reducing the pressure and / or increasing the temperature, and 30

- it requires a smaller size and / or number of adsorbers necessary to treat the gases to be separated, due to its high apparent density and its greater volumetric capacity.

It is the first object of the invention, a process for obtaining a microporous adsorbent material derived from a post-consumer coffee residue, with high apparent density, high micropore volume, high CO2 adsorption capacity, and high

equilibrium selectivity towards CO2, hereinafter method of obtaining the invention, comprising the following steps:

a) drying of post-consumer coffee residue to reduce its initial moisture content,

b) formed, in the absence of binders, of the post-consumer coffee residue obtained according to step (a), and

c) activation of the post-consumer coffee residue obtained according to step (b) by heat treatment using an activating agent.

By "equilibrium selectivity towards CO2" is meant that the adsorbent has a CO2 adsorption capacity significantly higher than that of the other components present in the mixture to be separated. N2 is the majority compound of chimney gases (around 80%), so that in the present invention, equilibrium selectivity refers to the selectivity towards CO2 over N2. This selectivity is a fundamental factor to be able to separate CO2 from chimney gases. fifteen

By "post-consumer coffee residue" is meant the bi-phase solid residue, which is obtained from the elaboration of any coffee beverage and which preferably has a high carbon content, of more than 50%, and very reduced inorganic matter, less than 2%. Examples of post-consumer coffee waste that can be used in the process of obtaining the invention are, residues obtained in the production of coffee at the domestic level, at the hospitality level or at the industrial level, and which includes the residue from coffee production soluble or instant.

In a particular embodiment of the invention, the drying of step (a) is carried out at a temperature between 50 and 150 ° C, and for a time between 1 and 24 h.

In a preferred embodiment of the invention, drying of step (a) is carried out at a temperature of 100 ° C for a time of 4 h. 30

In one aspect of the invention, the post-consumer coffee dry residue comprises a uniform particle size, smaller than 1 mm, with a majority fraction between 212 and 425 μm.

 35

In another aspect of the invention, the post-consumer coffee residue forming of step (b) is carried out without the addition of binders, according to a method selected from among, pressure compaction with the help of a pill, pelletizer or press for form pills, pellets, or briquettes, or by extrusion.

 5

In a particular embodiment of the invention, the forming treatment of step (b) is carried out by compaction by pressing the post-consumer coffee residue, using a pastillator or pelletizer that allows the desired diameter to be adjusted. Preferably, the pellets obtained have a diameter between 2 and 10 mm and a height between 2 and 11 mm. 10

In a preferred embodiment of the invention, after the step (b) of forming, cylindrical pellets of 4 mm in diameter and 3 mm in height are obtained.

In one aspect of the invention, the heat treatment of step (c) is carried out in a fixed bed, or in a fluidized bed or in a rotary kiln.

By "activating agent" is meant a chemical species capable of reacting with the carbon atoms of the surface of the material, partially gasifying it and developing the porous texture of the material. twenty

Examples of activating agents that can be used in the present invention are, without limitation, CO2, H2O, air, NH3 and mixtures thereof, and preferably CO2.

A heat treatment with a gas stream containing CO2, which is a harmless, and highly available compound, reduces the volatile content of the carbonaceous precursor by 80% and develops the porous texture, maintaining the external morphology of the shaped particle, although there is a reduction in size due to the loss of volatile matter. Additionally, the liquid and gaseous by-products produced during the heat treatment can be used for their energy content. 30

In another preferred embodiment of the invention the activating agent is pure CO2.

In another preferred embodiment of the invention, heat treatment with a stream of pure CO2 is carried out at temperatures between 600 and 900 ° C, and preferably

between 700 and 750 ° C, for periods of time between 30 min and 12 h and with a heating rate between 1 and 100 ° C min-1.

In an exemplary embodiment, the heat treatment is carried out in a fixed bed reactor (ID 3.9 cm) with a CO2 current (surface speed of 0.005 m s-1) at 700 ° C 5 for 8 h (speed of heating of 5 ° C min-1).

The activation process reduces the size of the pellets obtained after forming stage (b), due to the loss of volatile matter.

 10

In a particular embodiment of the invention after step (c) of activation of the post-consumer coffee residue, pellets with a particle diameter and a height between 1 and 10 mm, and preferably with a particle diameter of 2.7, are obtained and a height of 1.9 mm.

 fifteen

A second object of the invention is the adsorbent material obtained by the process of the invention, hereinafter adsorbent material of the invention.

In one aspect of the invention, the adsorbent material of the invention is a material having:

i) an apparent density between 0.400 g cm-3 and 1,000 g cm-3,

ii) a micropore volume of at least 0.2 cm3 g-1,

iii) an average micropore size of less than 1 nm, preferably 0.5 nm, and

iv) a CO2 adsorption capacity between 0.5 and 2.0 mmol g-1 at 14 kPa and at temperatures between 0 and 50 ˚C. 25

The micropore volume and the narrow nature thereof are responsible for the adsorbent material of the invention having a particularly high CO2 adsorption equilibrium capacity at low partial CO2 pressures, characteristic of flue gases. 30

The third object of the invention is the use of the adsorbent material of the invention for the adsorption of CO2, hereinafter use of the invention.

In one aspect of the invention, the use of the invention comprises at least the following steps:

a) contacting the gas to be treated with the adsorbent material of the invention, to separate the CO2, and

b) regenerate the adsorbent material of the invention, recovering the previously captured CO2.

 5

In a particular embodiment of the invention, the use of the material of the invention is carried out in the capture of CO2 after combustion.

The person skilled in the art will know that the most likely installation point for a post-combustion capture unit in a coal-fired power plant is at the exit of the desulfurization unit. Likewise, the person skilled in the art will know that the chimney gases leaving said unit are at a pressure close to atmospheric and at a temperature around 50 ° C.

Typically, in a post-combustion CO2 capture process, the concentration of CO2 in the gas to be separated can be between 3 and 33%, depending on the source that originates the current: gas turbine (3-4%) , natural gas boiler (7-10%), pulverized coal boiler (12-14%), metallurgical industry (20-27%), cement industry (14-33%). (IPCC, 2005: IPCC Special Report on Carbon Dioxide Capture and Storage).

 twenty

In a particular embodiment of the invention, the contact of step (a) is carried out at a temperature between 15 and 70 ° C and at a pressure between 100 and 300 kPa. Preferably the temperature is between 20 and 50 ° C and the pressure is between 100 and 150 kPa.

 25

The person skilled in the art will know that the amount of adsorbent necessary to achieve a certain CO2 capture objective depends on the adsorbent's working capacity under the operating conditions for a given cycle configuration and certain feeding conditions (temperature, pressure and composition).

 30

The selectivity, whether kinetic or equilibrium, is essential to carry out the separation of a gas mixture by adsorption.

The equilibrium selectivity of an adsorbent towards a compound present in a gas mixture is defined as the ratio between the amounts adsorbed at a given partial pressure in the gas phase, divided by the ratio between said partial pressures:

S1 / 2 = (q1 / q2) / (p1 / p2), where qi represents the adsorbed amount of compound i and p the partial pressure of i in the gas phase.

In an exemplary embodiment, starting from a regenerated bed full of helium, and for a feed with 15% CO2 (balance N2) at 50 ° C and 130 kPa the adsorbent material of the invention has an adsorption capacity of 0 , 68 mmol CO2 and 0.14 mmol N2 per g of adsorbent material, resulting in a selectivity of: 27.

In another exemplary embodiment, starting from a regenerated bed full of N2, and for a feed with 16% CO2 (N2 balance) at 21 ° C and 130 kPa, the adsorbent material of the invention has an adsorption capacity of 1.3 mmol of CO2 per g of adsorbent material.

By "regeneration" is meant the process by which it is possible to recover the CO2 previously retained by the adsorbent material of the invention, and thus achieve said material to be active again in the capture of CO2 during the next cycle.

In a particular aspect of the invention, the regeneration of step (b) is carried out by a process selected from, heating at approximately constant pressure (TSA), decrease in system pressure at approximately constant temperature (PSA and / or VSA), or by a combination of both procedures.

In a particular embodiment of the invention, the regeneration is carried out by a TSA process at a temperature between 50 and 150 ° C.

 25

It is known to the person skilled in the art that chimney gases are at a pressure close to atmospheric, and that due to their high volume, it is not economical to compress them, so that a process of separation by adsorption by pressure oscillation ( PSA) would have to operate between a slightly higher atmospheric pressure and a subatmospheric pressure, which must be lower than the partial pressure of CO2 in the feed stream. This process is known as Vacuum Swing Adsorption, or VSA. In addition, the person skilled in the art will also know that more than 70% of the energy consumed in a VSA process is due to the vacuum pump, so the evacuation pressure must be as high as possible to reduce the energy consumption of the process.

 35

In a particular embodiment of the invention the regeneration is carried out by a VSA process until a pressure that is to be lower than the partial pressure of the CO2 in the feed, preferably between 10 and 1 kPa.

The adsorbent material of the invention has an isostatic heat of adsorption of CO2 5 less than 30 kJ mol-1, typical of fisisorption processes. As the person skilled in the art will know, these values are lower than other CO2 adsorbents, such as zeolites, some MOFs, and much lower than sorbents impregnated with amines (chemisorption). This fact is highly desirable, since it will imply a lower energy consumption to carry out the regeneration in the case of a TSA process, or in a PSA or VSA process. The 10 thermal effects, which tend to reduce the productivity of the adsorbent, will also be lower.

In another particular embodiment of the invention, the regeneration is carried out by a combined TSA / VSA procedure at a pressure below the partial pressure of CO2 15 in the feed stream, preferably between 10 and 1 kPa, and at a higher temperature to that of the adsorption stage, preferably between 50 and 100 ° C. The person skilled in the art will know that the combined action of vacuum and heat allows a more efficient regeneration, improving the recovery and productivity of the process, or reducing the energy requirements of the process, either reducing the level of vacuum 20 necessary to achieve sufficient regeneration, or by reducing the regeneration temperature thanks to the auxiliary action of the vacuum.

Throughout the description and the claims the word comprises and its variants are not intended to exclude other technical characteristics, components or steps. For those skilled in the art, other objects, advantages and features of the invention will be derived partly from the description and partly from the practice of the invention. The following examples and drawings are provided by way of illustration, and are not intended to be limiting of the present invention.

 30

Brief description of the figures

Figure 1. Adsorption equilibrium isotherms of CO2 and N2 at 25 ° C. Obtained in a volumetric adsorption equipment between 0.1 and 120 kPa for the adsorbent material of the invention (hereinafter PPC).

 35

Figure 2. Adsorption equilibrium isotherms of CO2 and N2 at 50 ° C. Obtained in a volumetric adsorption equipment between 0.1 and 120 kPa for PPC and an activated carbon marketed for CO2 adsorption (Norit R 2030 CO2).

Figure 3. Breaking curves of N2 and CO2 at 50 ° C. Dynamic adsorption experiment 5 performed on a bed of PPC (3.5 g) regenerated and initially filled with helium, feeding a mixture (2.7 mmol min-1) with a composition similar to that of chimney gases (15% CO2, balance N2) at 50 ° C and 130 kPa.

Figure 4. CO2 breakage curve at room temperature. Dynamic adsorption experiment 10 performed on a bed of PPC (3.5 g) regenerated and initially filled with nitrogen, when a mixture (4.5 mmol min-1) is fed with a composition similar to that of chimney gases ( 16% CO2, balance N2) at 130 kPa and room temperature (21 ° C).

 fifteen

Figure 5. Regeneration. CO2 desorption of the previously saturated PPC bed with 16% CO2 (N2 balance) at 130 kPa and 21 ° C (Figure 4), feeding a 0.07mmol min-1 purge of N2 and heating the bed from the outside.

Figure 6. Three-stage VSA process (adsorption + evacuation + repressurization). The cycle, carried out with a bed of 3.5 g of PPC, and a feed of 2.7 mmol min-1 with 13% CO2 (N2 balance) operates at an approximately constant temperature of 50 ° C and its Pressure ranges between a maximum pressure of 130 kPa (adsorption stage) and a minimum pressure of 4 kPa (evacuation stage). The pressure and molar flow rates of CO2 and N2 that leave the adsorber after the steady-state cyclic state 25 during the adsorption stage (a) and during the vacuum regeneration stage (b) are shown.

Figure 7. Four-stage VSA process (adsorption + purging with CO2 + evacuation + repressurization). The cycle, carried out with a bed of 3.5 g of PPC, and a feeding of 2.7 mmol min-1 with 13% CO2 (N2 balance), operates at an approximately constant temperature of 50 ° C and its pressure ranges between a maximum pressure of 130 kPa (adsorption stage) and a minimum pressure of 10 kPa (evacuation stage). The pressure and molar flow rates of CO2 and N2 that leave the adsorber are shown once the stationary cyclic state is reached during the CO2 purge stage (a) and during the evacuation stage (b). 35

Figure 8. Six-stage VSA / TSA (VTSA) combined process (adsorption + purging with CO2 + evacuation up to 20 kPa + evacuation up to 10 kPa with heating up to 70 ° C + purging with N2 + repressurization). The cycle has been carried out with a bed of 3.5 g of PPC and a feed of 2.7 mmol min-1 with 13% CO2 (N2 balance) at 50 ˚C and 130 kPa. The pressure, temperature and molar flow rates of CO2 and N2 are shown that leave the adsorber once the steady-state cyclic state is reached during the production stages, (a) evacuation stage at 10 kPa with simultaneous heating up to 70 ° C and (b) cooling stage at 50 ° C with purging of N2 at 10 kPa.

Embodiment Examples 10

A. Process for obtaining the adsorbent material of the invention

Example 1. Procedure for obtaining PPC

First, a coffee residue from used Nespresso® capsules was dried in a forced convection oven at 100 ° C for 4 h to remove excess moisture. fifteen

The dried coffee residue is characterized by having a particle size of less than 1 mm, with a majority fraction between 212 and 425 μm.

This material, which we will call C from now on, was formed using a desktop pelletizer (or pill), operated by means of a force flywheel, whose maximum driving force is 15 kN, and which allows to obtain pellets (or pellets) of diameter between 2 and 10 mm and with a maximum height of 11 mm. In the present embodiment, cylindrical pellets 4 mm in diameter and 3 mm high were obtained, which we will call PC. 25

Once formed, the activation of the coffee residue pellets (PC) was carried out. For this, 40 g of PC were introduced into a double-walled quartz reactor (ID 3.9 cm) so that the solid formed a fixed bed inside that was passed through the feed gas, pure CO2 with a velocity surface area of 0.005 m s-1. The reactor 30 was introduced in a vertical tubular furnace and heated at a heating rate of 5 ° C min-1 until reaching 700 ,C, a temperature that was maintained for 8 h.

The adsorbent resulting from the activation process, (PPC), had a smaller size than PC, due to the loss of volatile matter, which causes the pellet to contract, although it retained its integrity and retained its cylindrical shape.

Example 2. Procedure for obtaining CC

3 g of pellets of post-consumer coffee residue (PC) obtained by forming the post-consumer coffee residue (C) according to Example 1 were introduced into a double-walled quartz reactor (D.I. 2 cm). The reactor was introduced in a vertical tubular furnace and 5 heated at 5 minC min-1 to 700 ˚C with a stream of pure CO2 (surface speed of 0.005 m s-1), maintaining these conditions for 6 h.

The adsorbent resulting from the activation process, hereinafter referred to as CC, was smaller than the starting pellets, PC, due to the loss of volatile matter, 10 although it retained its integrity and its cylindrical shape.

Example 3. Procedure for obtaining CNC

3 g of post-consumer coffee residue from used Nespresso® capsules (C) were activated following the protocol detailed in Example 2. 15

The material resulting from the activation, hereinafter referred to as CNC, has a powdery character, with a particle size finer than the initial post-consumption coffee residue (C), and cannot be formed by simple compaction by pressure without the aid of binders following the protocol described in Example 1. 20

B. Adsorbent material of the invention

Example 4. Characterization of PPC

4.1. Density

The bulk density of the particle (called the volume occupied by the intraparticular porosity) is called bulk density (or particle density). The apparent density of PPC was determined by mercury intrusion at 0.1 MPa in an automatic Micromeritics AUTOPORE IV 9500: 0.743 g cm-3.

The density of PPC was also estimated individually for 10 pellets chosen at random 30 from their geometric volume and the mass of the dry pellet (see Table 1). The particle density estimated in this way is very close to the apparent density determined by mercury intrusion, which gives an idea of the homogeneity of the adsorbent obtained.

 35

Table 1. Main characteristics of the adsorbent material pellets obtained by the process of the invention

 Pellet # (PPC)

 Diameter (mm) Height (mm) Mass (g) Densidated (g cm-3)

 one

 2.7 1.8 0.0078 0.757

 2

 2.7 2.1 0.0095 0.790

 3

 2.6 1.8 0.0076 0.795

 4

 2.7 1.9 0.0077 0.708

 5

 2.7 1.8 0.0077 0.747

 6

 2.7 1.7 0.0072 0.740

 7

 2.6 1.9 0.0080 0.793

 8

 2.6 2.1 0.0087 0.780

 9

 2.7 1.8 0.0081 0.786

 10

 2.7 1.9 0.0083 0.763

 Average

 2.7 1.9 0.0081 0.766 ± 0.028

a Calculated from the geometric volume and mass of the dry pellet.

The person skilled in the art will know that the packing density includes, in addition to the intraparticular porosity, the empty volume between the particles that make up a bed. This value depends on the size and shape of the particles, as well as the size and shape of the bed and the way in which the packing is performed.

The compacted density of PPC was determined with the help of an automatic Quantachrome 10 Autotap analyzer, using a 10 ml specimen, measuring the mass of adsorbent loaded in the specimen and its volume after being compacted (> 600 strokes: until the volume remained constant). This measure yielded a result of 0.421 g cm-3.

 fifteen

The density values obtained for the pellets of adsorbent material of the invention were considerable, something especially desirable in order to reduce the volume of adsorbent necessary for a given application.

4.2. Textural characterization 20

The total micropore volume of PPC was estimated by the Dubinin-Radushkevich method applied to the adsorption isotherm of N2 at -196 ° C and was 0.21 cm3 g-1. The average micropore size was calculated using the Stoeckli-Ballerini equation applied to the isotherm

adsorption of N2 at -196 ° C, and was 1.0 nm; The BET surface, applied to the adsorption isotherm of N2 at -196 ° C, was 507 m2 g-1; the total pore volume, calculated from the adsorption isotherm of N2 at -196 ° C, as the amount of N2 adsorbed at a partial pressure of 0.99 was 0.21 cm3 g-1; The volume of narrow micropores, calculated by the Dubinin-Radushkevich method applied to the CO2 adsorption isotherm at 0 ° C, was 5 0.23 cm3 g-1 and the average size of the narrow micropores, calculated using the equation of Stoeckli-Ballerini applied to the CO2 adsorption isotherm at 0 ° C, was 0.5 nm.

The volume of micropores coincided with the total pore volume, both calculated from the adsorption of N2 at -196 ° C, which indicates that the adsorbent material of the invention is strictly microporous.

4.3. Comparison of PPC with other adsorbent materials

The state of the art reports activated carbons that show apparent density values lower than those of PPC. For example, the commercial activated carbon Norit C GRAN, 15 obtained by activation of wood with phosphoric acid, as well as the activated carbons AC1 and AC2 used as an example in US2010 / 0242728 for the adsorption of CO2 (see Table 2). US2010 / 0242728 also indicates the apparent density values of a charcoal and a bituminous coal, clearly lower than those of the adsorbent material of the invention (see Table 2). twenty

Norit R 2030 CO2, used commercially in the adsorption of CO2, and which is obtained by activating peat with steam at 900 ˚C (extruded 3 mm in diameter) has a density, according to data provided by the manufacturer, of 0.560 g cm-3. This value corresponds to the packing density (determined from the mass that occupies a certain volume of activated carbon according to an internal standard). This value depends on the method used for its determination, so that in order to compare the packing density of this adsorbent with the PPC value, a compacted density measurement was obtained according to the procedure described in Example 2, obtaining a value of 0.476 g cm-3, not far from that of PPC (see Table 2). Likewise, the bulk (or particle) density value, determined by mercury intrusion at 0.1 MPa for this commercial adsorbent is also shown in Table 2 for comparative purposes. The bulk density of this material is the highest among all the materials shown in Table 2, followed by the PPC adsorbent, which occupies the second place.

 35

Table 2. Density of different carbonaceous materials

 Adsorbents

 Density (g cm-3)

 Norit C GRAN

 0.400a / 0.230b

 Norit R 2030 CO2

 0.850a / 0.560b / 0.476c

 PPC

 0.743a / 0.421c

 AC1d

 0.520

 AC2d

 0.390

 Charcoal d

 0.450

 Bituminosod coal

 0.640

a Apparent density measured by mercury intrusion at 0.1MPa; b Packaging density provided by the producer; c Packaging density measured according to Example 2; dUS2010 / 0242728

 5

Norit C GRAN commercial activated carbon, obtained by activating wood with phosphoric acid, is a coal with a high total pore volume, but with a very wide distribution of porosity: it contains a high volume of meso and macropores; The micropore volume represents only 53% of the total pore volume (see Table 3). These characteristics make it suitable for adsorption applications of organic compounds of high molecular mass, such as dyes or proteins. On the other hand, Norit R 2030 CO2 activated carbon, which is used commercially for the removal of CO2 in refrigerated fruit stores, has a significantly smaller total pore volume than Norit C GRAN. 90% of this volume is made up of micropores (which as the person skilled in the art knows, are responsible for the adsorption of CO2 at low pressures) and also, the average size of them is considerably smaller (see Table 3) . The adsorbent of the invention, PPC, has a smaller total pore volume than the commercial activated carbons shown in Table 3. However, the narrow micropore volume of PPC, calculated from the CO2 adsorption isotherm at 0 ° C , Is superior. Likewise, the average micropore size is also smaller than that of the 20 commercial activated carbons shown as a reference.

 25

Table 3. Textural characterization parameters of various adsorbent materials

 Adsorbent

 Adsorption of N2 at -196˚C Adsorption of CO2 at 0˚C

 Vp (cm3 g-1)

 SBET (m2 g-1) VDR, N2 (cm3 g-1) LN2 (nm) VDR, CO2 (cm3 g-1) LCO2 (nm)

 Norit C Granular

 0.97 1361 0.51 2.9 0.19 0.7

 Norit R2030CO2

 0.41 983 0.37 1.1 0.17 0.6

 PPC

 0.21 507 0.21 1.0 0.23 0.5

VDR, N2: micropore volume calculated by the Dubinin-Radushkevich method applied to the adsorption isotherm of N2 at -196 ° C; LN2: average micropore size calculated using the Stoeckli-Ballerini equation; SBET: BET surface; Vp: total pore volume calculated from the amount of N2 adsorbed at a partial pressure of 0.99; VDR, CO2: narrow micropore volume calculated by 5 the Dubinin-Radushkevich method applied to the CO2 adsorption isotherm at 0 ° C; (LCO2): average size of narrow micropores calculated using the Stoeckli-Ballerini equation

Example 5. Effect of forming in the textural development of the adsorbent of the invention

The CC adsorbent, obtained from the activation of the formed post-consumer coffee residue 10 (see Example 2) has a greater total pore volume and specific surface area (see Table 4) than the CNC adsorbent, obtained from the post-consumer coffee residue without conform (see Example 3). Greater textural development is beneficial for the application of materials as adsorbents, since it improves both the adsorption capacity and the kinetics of the adsorption process. In addition, both materials are essentially 15 microporous (the volume of micropores, VDR, N2, represents at least 95% of the total pore volume), and the average micropore size is smaller for the shaped material (CC), which is desirable to maximize CO2 adsorption at low partial pressures.

Table 4. Textural characterization parameters of two adsorbents obtained from 20 coffee residue

 Adsorbent

 Adsorption of N2 at -196˚C

 Vp (cm3 g-1)

 SBET (m2 g-1) VDR, N2 (cm3 g-1) LN2 (nm)

 CC Adsorbent (Example 2)

 0.21 491 0.20 0.8

 CNC Adsorbent (Example 3)

 0.15 378 0.14 0.9

C. Use of the adsorbent material of the invention for the adsorption of CO2

Example 6. Effect of forming on CO2 adsorption capacity

The adsorption capacity of CO2 at atmospheric pressure of the adsorbent materials CC (Example 2) and CNC (Example 3) was evaluated in a gravimetric analyzer measuring the mass gain experienced by exposing 20 mg of sample, previously regenerated and dried (dried) : 1 h at 100 ˚C in a stream of 50 ml min-1 of Ar), at a stream of 50 ml min-1 of CO2. The CO2 adsorption capacity of the CC adsorbent at 25 and 50˚C was higher than that of CNC (see Table 5). In addition, the CC shaped material took less time to reach equilibrium, indicating that the formed adsorbent exhibits lower resistance to matter transfer, which is especially desirable for application in cyclic adsorption processes.

Table 5. CO2 adsorption capacity of two adsorbents obtained from post-consumer coffee residue

 Adsorbent

 Adsorption of CO2 at 101 kPa (mmol CO2 g-1 adsorbent)

 25 ˚C

 50 ˚C

 CC Adsorbent (Example 2)

 2.4 1.8

 Non-conformed CNC adsorbent (Example 3)

 2.3 1.7

 fifteen

Example 7. Adsorption equilibrium (monocomponent) of CO2 and N2 of the PPC adsorbent

A study of the monocomponent adsorption equilibrium of CO2 and N2 between 0.1 and 120 kPa at 0.25 and 50 ° C on the PPC adsorbent was carried out. For this purpose, a volumetric equipment (also called manometric) was used for gas adsorption TriStar 3000 from Micromeritcs. Prior to measuring the adsorption isotherms of pure compounds, a sample aliquot is introduced into the sample holders (around 0.17 g) to be degassed at 100 ° C under vacuum for at least 12 h. The adsorption isotherms are automatically measured by the equipment, which doses in a controlled manner volumes of gas to the sample holder, initially under vacuum, recording the amount adsorbed by the sample as the pressure in it is increased. The adsorption temperature 25 is regulated by a circulation thermostat. The dead volume is corrected by performing a helium pycnometry in situ, with the sample, before or after performing the isotherm.

The adsorption isotherms of N2 are linear, Henry type, indicating a weak adsorbent-adsorbate interaction, while the CO2 adsorption isotherms are Type I (BDDT classification), indicating a stronger adsorbent-adsorbate interaction (see Figures 1 and 2). This difference is due to the greater quadrupole moment of the CO2 molecule with respect to N2. In addition, the CO2 adsorption equilibrium capacity is much higher than that of N2. This indicates a high selectivity of CO2 / N2 equilibrium, a relevant parameter for the application of these adsorbents in post-combustion capture, where N2 is the major component of chimney gases.

Moreover, the CO2 adsorption equilibrium capacity of the PPC adsorbent is especially high at low CO2 pressures, characteristic of flue gases. For example, the CO2 adsorption capacity at a pressure of 14.4 kPa is 1.19 ± 0.03 mmol g-1 at 25 ˚C, and 0.68 ± 0.08 mmol g-1 at 50 C. These values correspond to the average of two experimental measurements.

 fifteen

The isostatic heat of CO2 adsorption of the adsorbent of the invention was estimated from the CO2 adsorption isotherms at 0, 25 and 50 ° C by means of the Clausius-Clapeyron equation, resulting in an average value of 24 kJ mol-1, characteristic of fisisorción processes, easily reversible.

 twenty

7.1. Comparison of the adsorption isotherms of the PPC adsorbent and an activated commercial carbon

The CO2 adsorption equilibrium capacity of the PPC adsorbent is superior to that of Norit R 2030 CO2 commercial activated carbon, which is used as a CO2 adsorbent, especially at low partial pressures (see Figure 2). For example, the CO2 adsorption capacity of Norit R 2030 CO2 at 25 ° C and 14.5 kPa is 0.82 mmol g-1 and at 50 ° C and 14.6 kPa 0.46 mmol g-1. The adsorption capacity of PPC has a capacity almost 50% higher in these conditions. This difference is due to the greater volume of narrow micropores and the narrower nature of them, which gives them greater adsorption potential. In addition, the N2 adsorption equilibrium capacity of 30 Norit R 2030 CO2 is slightly higher than that of PPC (see Figure 2), which implies a lower equilibrium selectivity of commercial coal.

The CO2 adsorption equilibrium capacity of PPC at 25 ° C and 101 kPa (2.77 ± 0.03 mmol g-1) is also greater than that of Norit R 2030 CO2, which under these conditions has a capacity of adsorption of 2.66 mmol CO2 g-1. Likewise, PPC also presents greater

adsorption capacity than other commercial activated carbons of the state of the art. For example, "AC1", used as a CO2 adsorbent in US2010 / 0242728 A1, has a CO2 adsorption capacity of about 10% by mass (2.3 mmol g-1) at 25 ° C and 100 kPa.

 5

Example 8. Adsorption of binary gaseous mixtures of CO2 and N2 in the PPC adsorbent using a fixed bed adsorption system

The CO2 separation from a binary CO2 / N2 mixture using the PPC adsorbent was evaluated under dynamic conditions. For this, an adsorption unit equipped with a stainless steel bed with an internal diameter of 9.12 mm, with temperature control (± 1 ° C) and pressure (± 10 kPa) was used. The composition and flow rate of the feed gas was regulated by mass flow controllers, and the composition of the output stream was determined by a gas microchromatograph. The flow rate at the exit of the bed was determined by the addition of a known flow rate of oxygen before the analyzer. fifteen

In these experiments, called the rupture curve, the adsorption stage (feeding of the mixture to be separated) was prolonged for 1 h, so that the bed was completely saturated (it reached equilibrium). Also, desorption (regeneration of the adsorbent) was carried out by heating at 150 ° C for 1 h with a gas purge, so that the regeneration was also complete. Before carrying out a new adsorption stage, the adsorbent was allowed to cool to the adsorption temperature. These adsorption / desorption experiments were repeated consecutively for 6 complete cycles with matching results, indicating good repeatability and adsorbent behavior. 25

8.1. Breaking curve of a binary mixture of CO2 and N2 at a temperature of 50˚C

Figure 3 shows the rupture curves of CO2 and N2 at 50 ° C and 130 kPa resulting from feeding a gaseous mixture (2.7 mmol min-1) with 15% CO2 (N2 balance) on a bed of PPC (3 , 5 g) regenerated and full of helium. The first compound to reach exit 30 of the bed was the N2, which was barely retained (break time ≈ 0.5 min), while the CO2 break time was about 6 min under these conditions. As can be seen in Figure 3, in the course between both ruptures, the molar flow of N2 at the exit of the bed exceeds the flow of N2 fed for a few minutes. This is because part of the initially adsorbed N2 is displaced by the preferential adsorption of CO2 35 (a phenomenon known as roll-up). When the bed begins to saturate, the molar flow rate

of CO2 at the exit of the bed begins to increase until the flow of fed CO2 is equalized (fully saturated bed, in balance with the composition of the feed). Performing a balance of matter to the bed, and discounting the dead volume of the equipment and the porosity of the bed, it is possible to obtain the adsorbed amount of each of the gases: 0.68 mmol of CO2 and 0.14 mmol of N2 per g of PPC, and calculate the real selectivity in these 5 conditions: 27. This value is higher than what would be estimated from the adsorption equilibrium of the pure compounds for the same partial pressure (19) due to the competitive adsorption, which causes the adsorption sites are preferably occupied by CO2 versus N2.

 10

8.2. CO2 adsorption from a binary mixture of CO2 and N2 at room temperature

The CO2 rupture curve at room temperature (21 ° C) and 130 kPa on the bed of adsorbent material of the invention (initially regenerated and filled with nitrogen) and for a feed of 4.5 mmol min-1 with 16% of CO2 (balance N2), is shown in Figure 4. The amount of CO2 adsorbed under these conditions was 1.3 mmol g-1. A thermocouple embedded in the bed allowed to record the temperature variation during the experiment. As seen in Figure 4, the temperature increase associated with CO2 adsorption was only 5 ° C, and the heat dissipated rapidly. This indicates that the temperature during the adsorption stage in a cyclic process will remain approximately constant, which is favorable, since the adsorption capacity decreases 20 when the temperature increases. The thermal effects for the adsorbent of this invention will be of less importance than for other adsorbents with higher isostatic heat of CO2 adsorption.

8.3. CO2 desorption 25

The saturated PCC bed (see Figure 4) was regenerated by feeding a small purge of N2 (0.07 mmol min-1) and heating the reactor from the outside. Figure 5 shows the evolution of the temperature and the molar flow of CO2 at the outlet of the adsorber during the regeneration stage. By integrating the area below the CO2 curve and discounting the CO2 stored in the porosity of the bed and the dead volume of the equipment, the amount of desorbed CO2 is obtained: 1.3 mmol g-1. That is, all previously adsorbed CO2 was desorbed. The CO2 flow rate went through a maximum at 2.8 min, at which time the bed temperature had only reached 70 ° C. Other adsorbents, with higher isospheric heat of CO2 adsorption, require higher temperatures for regeneration.

 35

Example 9. Cyclic adsorption / desorption processes

The cycles included below illustrate the versatility of the adsorbent object of the present invention for application in post-combustion CO2 capture processes.

Unlike the long adsorption / desorption cycles presented in Example 8, in which the adsorbent was allowed to reach the adsorption equilibrium with the feed and 5 in which the bed was completely regenerated during the desorption stage, the cycles presented in this example, they intend to give a more representative view of a real cyclic operation, in which the adsorption stage stops before the bed is completely saturated, and where the regeneration is usually not complete. The adsorption and desorption stages alternate rapidly so that the adsorber oscillates between two states 10 with different pressure and / or temperature conditions, which allow it to carry out the separation of the feed continuously. In an industrial process there are usually several adsorbers (multicolumn process), so that when a bed needs to be regenerated, the feed stream is directed to another bed, already regenerated, producing a constant consumption of feed (continuous process). fifteen

9.1. VSA three-stage process

A simple three-stage VSA process (adsorption + evacuation + repressurization with feed) was carried out at 50 ° C, with a bed of PPC (3.5 g). To carry out the evacuation stage, a diaphragm pump with pressure control (≥ 0.5 20 kPa) was connected to the adsorber outlet by means of an automatically actuated valve.

During the adsorption stage, 2.69 mmol min-1 of a mixture with 13% CO2 (N2 balance) was fed at a pressure of 130 kPa for 330 s. After this time (partially saturated bed) the bed entrance was closed and evacuated for 365 s. Finally, the bed was repressed with the feed, keeping the exit of the bed closed (40 s).

During the adsorption stage, an effluent depleted in CO2 leaves the bed at 130 kPa (see Figure 6a). The results shown correspond to the stationary cyclic state 30 (cycles 7-28). It can be seen that PPC exhibits good performance in cyclic operation, producing repetitive results, without loss of capacity.

Figure 6b shows the molar flow of CO2 and N2 and the pressure at the exit of the bed during the vacuum regeneration stage. The flow leaving the bed reached its maximum value 35 during the first moments of depressurization, which was very fast. The purity of

CO2 obtained during the regeneration stage was 36%, and 52% of the total CO2 fed was recovered. The purity of CO2 was not high because the bed still contained a large amount of nitrogen when the evacuation began. This cycle is not intended to be an optimized cycle, but only illustrative. If the evacuation was carried out in countercurrent, purity would be increased, since the bed inlet, unlike the outlet, is completely saturated.

9.2. VSA four-stage process

A VSA cycle similar to that of Example 9.1 was carried out, although adding a purge stage with pure CO2 (365 s; 0.2 mmol min-1) between the adsorption and evacuation steps to improve the CO2 purity.

Figure 7a shows the molar flow rates of CO2 and N2 at the exit of the bed during the CO2 purge stage: the fed CO2 is mostly adsorbed, while the N2 is displaced, leaving the adsorber. The average composition of the effluent during this stage, 13% CO2, is similar to that of the feed, so in an industrial operation, it could be recirculated and fed along with it.

Figure 7b shows the evolution of the CO2 and N2 molar flows and the pressure at the exit of the bed during the evacuation stage. The purity of the CO2 recovered during 20 this stage increased to 61%, and the amount of CO2 recovered accounted for 67% of the total CO2 fed.

In Figure 7b it is observed that the N2 remnant that had not yet been displaced in the CO2 purge stage, left the bed during the first moments of the evacuation stage; however, the CO2 presented 2 maximums: the first, like the N2, at the beginning of the stage, and the second, after approximately 50 s, when most of the N2 had already left the bed, and the pressure had reached 20 kPa By setting the start of the production stage at 735 s, the purity of the product would reach 87%. The product from the first 40 s of the evacuation, which has an average 30% molar composition of 26% CO2, could be recirculated and fed together with the feed (the partial pressure of the CO2 would be increased during the adsorption stage favoring separation ). Another option, even more preferable, would be to carry out a pressure balancing stage by connecting the exit of the bed that ended the purge stage with CO2 with the entrance of a newly regenerated bed that must be pressurized. In this way, recovery would be improved, and mechanical energy would be saved.

9.3. VTSA hybrid adsorption process (combines the effect of a moderate vacuum with a shallow increase in temperature)

A hybrid VTSA process consisting of a 6-stage cyclic process was carried out: adsorption at 130 kPa and 50 ° C (330 s; 2.69 mmol min-1; 13% CO2, balance N2), purging with 5 pure CO2 (185 s; 0.47 mmol min-1), evacuation up to 20 kPa (40 s), evacuation up to 10 kPa with external heating up to 70 ° C (325 s), cooling up to 50 ° C at 10 kPa with a purge of Pure N2 (185 s; 0.07 mmol min-1), and feed repressurization (40 s).

 10

The purge stage with N2 under vacuum allows the bed to cool down to the adsorption temperature, but also improves the recovery of CO2, since it reduces the partial pressure of the CO2 in the bed, facilitating its desorption, and displaces the adsorbed CO2.

The production stages (evacuation at 10 kPa and purging with N2) are shown in Figure 8. 15 With this configuration, 84% of the CO2 fed with 88% purity was recovered (productivity: 2.73 mol CO2 kg-1 h-1).

This recovery (and productivity) would increase if, in a multicolumn process, the current produced during the purge stage with 20 CO2 (average molar composition: 12% CO2) was recirculated along with the feed.

Also, in a multicolumn process, the current generated during the first evacuation stage (average molar composition: 21% CO2) could be used to repressurize another bed, including a pressure balancing stage connecting the outlet of bed 25 at the end of the stage of purge with the entry of a newly regenerated bed and that must be repressed. This would improve the recovery (and productivity) as well as the energy efficiency of the process. In fact, in the present example, the duration of the first evacuation stage has been set at 40 s, to coincide with the pressurization time, simulating the configuration of a cycle that included a pressure balancing stage 30 (with a only a bed of adsorption is not possible to carry out a true pressure balancing stage).

Claims (25)

1.- Procedure for obtaining a microporous adsorbent material derived from a post-consumer coffee residue, characterized in that it comprises the following steps: a) drying of post-consumer coffee residue to reduce its initial moisture content, b) formed, in the absence of binders, of the post-consumer coffee residue obtained according to step (a), and c) activation of the post-consumer coffee residue obtained according to step (b) by heat treatment using an activating agent. 10 2. Method according to claim 1, characterized in that the post-consumer coffee residue is obtained from the coffee production and has a carbon content greater than 50% and an inorganic matter content less than 2%.  fifteen 3. Method according to any one of claims 1 to 2, characterized in that the drying of step (a) is carried out at a temperature between 50 and 150 ° C, and for a time between 1 and 24 h. 4. Method according to claim 3, characterized in that the drying of step (a) is carried out at 100 ° C for a time of 4 hours. 5. Method according to any one of claims 1 to 4 characterized in that the post-consumer coffee residue after the drying step of step (a) comprises a uniform particle size and less than 1 mm, and with a majority fraction between 25 212 and 425 μm. 6- Method according to any one of claims 1 to 5, characterized in that the forming of step (b) is carried out, without the addition of binders, by compaction by pressure or extrusion. 30 7. Method according to claim 6 characterized in that pellets having a particle diameter between 2 and 10 mm and a height between 2 and 11 mm are obtained.  35 8. Method according to claim 7 characterized in that the pellets have a particle diameter of 4 mm and a height of 3 mm. 9. Method according to any one of claims 1 to 8, characterized in that the heat treatment of step (c) is carried out in a fixed bed, a fluidized bed or a rotary kiln. 10. Method according to claim 9, characterized in that the activating agent is chosen from CO2, H2O, air, NH3 and mixtures thereof.  10 11. Method according to claim 10, characterized in that the CO2 is pure CO2. 12. Method according to any one of claims 9 to 11, characterized in that the heat treatment of step (c) is carried out at temperatures between 600 and 900 ° C, for periods of time between 30 min and 12 h and with a heating rate 15 between 1 and 100 ° C min-1. 13. Method according to claim 12, characterized in that the heat treatment of step (c) is carried out at a temperature of 700 ° C, for a period of 8 h and with a heating rate of 5 ° C min- one. twenty 14. Method according to any one of claims 9 to 13, characterized in that pellets having a particle diameter and a height between 1 and 10 mm are obtained.  25 15. Method according to claim 14, characterized in that the pellets have a particle diameter of 2.7 and a height of 1.9 mm. 16. Adsorbent material obtained by the method of obtaining according to any one of claims 1 to 15. 30 17. Adsorbent material according to claim 16, characterized in that it has: i) an apparent density between 0.400 g cm-3 and 1,000 g cm-3, ii) a micropore volume of at least 0.2 cm3 g-1, iii) average micropore size less than 1 nm, and 35 iv) a CO2 adsorption capacity between 0.5 and 2.0 mmol g-1 at 14 kPa and at temperatures between 0 and 50 ˚C. 18. Use of the material according to any one of claims 16 and 17 for the adsorption of CO2. 5 19. Use of the material according to claim 18, characterized in that it comprises at least the following steps: a) contacting the gas to be treated with the adsorbent material according to any one of claims 16 and 17, to separate the CO2; and 10 b) regenerate the adsorbent material of the invention, recovering the previously captured CO2. 20. Use according to any one of claims 18 and 19 for the capture of CO2 after combustion. fifteen 21. Use according to any one of claims 18 to 20 characterized in that the contact of step (a) is carried out at a temperature between 15 and 70 ° C and at a pressure between 100 and 300 kPa.  twenty 22. Use according to claim 21 characterized in that the temperature is between 20 and 50 ° C and the pressure between 100 and 150 kPa. 23. Use according to any one of claims 18 to 22 characterized in that the regeneration of step (b) is carried out by a process selected from, approximately constant pressure heating, decrease of the system pressure at temperature approximately constant or by a combination of both procedures. 24. Use according to claim 23, characterized in that the regeneration of step (b) is carried out by an approximately constant pressure heating process at a temperature between 50 and 150 ° C. 25. Use according to claim 23, characterized in that the regeneration of step (b) is carried out by a process of lowering the system pressure at temperature 35 approximately constant up to a pressure lower than the partial pressure of the CO2 in the feed, between 10 and 1 kPa. 26.- Use according to claim 23, characterized in that the regeneration of step (b) is carried out by means of a combined process of heating at approximately constant pressure and of decreasing the pressure of the system at approximately constant temperature to a pressure comprised between 10 and 1 kPa, and at a temperature between 50 and 100 ˚C.