AU2016319478B2

AU2016319478B2 - Use of molecular sieves for decarbonating natural gas

Info

Publication number: AU2016319478B2
Application number: AU2016319478A
Authority: AU
Inventors: Jean-Robert LASCOUMETTES; Cécile LUTZ; Jullian VITTENET
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2015-09-08
Filing date: 2016-09-06
Publication date: 2019-10-31
Anticipated expiration: 2036-09-06
Also published as: WO2017042466A1; BR112018004205A2; DK3347116T3; EP3347116A1; CN108348834A; AU2016319478A1; BR112018004205B1; ZA201801955B; FR3040636B1; CN117487601A; FR3040636A1; ES2906779T3; EP3347116B1

Abstract

The invention concerns the use of zeolite adsorbent materials in agglomerate form comprising at least one zeolite of type A, for gas phase separation, in particular the separation of carbon dioxide (CO

Description

USE OF MOLECULAR SIEVES FOR DECARBONATING NATURAL GAS [0001] The invention relates to the use of zeolitic adsorbent materials in the form of agglomerates, having at least one zeolite of type A for gas-phase separation, in particular the separation of carbon dioxide (CO2) in Natural Gas (NG), in pressure swing processes, either of PSA (Pressure Swing Adsorption) type or of VSA (Vacuum Swing Adsorption) type or of VPSA (hybrid process of the two preceding processes) type or of RPSA (Rapid Pressure Swing Adsorption) type, in temperature swing processes of TSA (Temperature Swing Adsorption) type and/or in pressure and temperature swing processes of PTSA (Pressure and Temperature Swing Adsorption) type.

[0002] More particularly, the invention relates to the use of zeolitic adsorbent materials defined above and comprising calcium or calcium and sodium.

[0003] The use of the zeolitic adsorbent materials is particularly advantageous for gasphase separation and very particularly for the separation of carbon dioxide (CO2) in natural gas, where the transfer kinetics and the volume adsorption capacity, which are determining parameters for the effectiveness and the overall productivity of the process, are carefully chosen.

[0004] Natural gas is used in various applications and is generally provided via pipelines. In other cases, this resource is, in a first step, liquefied and then conveyed in the form of Liquefied Natural Gas (LNG). In order to avoid damage to the transportation and liquefaction equipment, the NG consequently has to be freed from various compounds, such as water, CO2 and hydrogen sulphide (H2S).

[0005] As regards the CO2, the concentrations in natural gas can vary within wide proportions, in particular from 0.1% to more than 4%, according to the operating source and the pretreatment(s) already carried out on the gas. The specifications required for this compound in natural gas are 2% for transportation in pipelines and 50 ppm upstream of the liquefaction processes present in LNG plants and floating production, storage and discharge units, such as, for example, offshore units, FLNG (Floating Liquefied Natural Gas) units, FPSO (Floating Production Storage Offloading) units and others.

[0006] Various technologies have thus been developed to remove the CO2 in natural gas, such as absorption on chemical or physical solvents, as described, for example, in Patent US 3 161 461. However, the use of such solvents is not easy to carry out, in particular in confined sites, which, for example, FLNG sites, FPSO sites and others are.

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PCT/FR2016/052203 — 2 — [0007] Membrane systems are also techniques used for the separation of CO₂ in gas mixtures, as described, for example, in the documents US 8 192 524 and US2015/0059579. However, these processes do not make it possible to achieve the specifications of very low CO2 contents required for liquefaction of natural gas.

[0008] Thus, in order to arrive at low CO2 contents in natural gas, of the order of a few ppm, recourse is generally had to processes for separation by adsorption. The flexibility and the simplicity of these processes are an advantage in their use, in particular with regard to FPSO units, and they can be used in addition to other technologies. For example, the documents US20140357925 and US 5 411 721 provide for the separation of CO2 of natural gas using membranes coupled to TSA and PSA processes.

[0009] As the kinetics and the adsorption capacity of materials are major criteria in evaluating the effectiveness and the overall productivity of the adsorption processes, great efforts have been made to develop ever more effective and long lasting materials for the gas-phase separation of CO2 and more particularly for the separation of CO2 present in natural gas.

[0010] Among the zeolitic adsorbent materials which are the most widespread in processes for the decarbonation of natural gas, various structures and combinations of zeolites are provided and available. For example, Patent GB 1 120 483 recommends the use of zeolitic adsorbent materials with a pore diameter of greater than 4 Ά for the purification of natural gas. However, this document does not indicate the nature of the binder used to agglomerate the zeolite crystals and does not allow any possible optimization in purification performances to be anticipated.

[0011] The document FR2 618 085 describes the purification of air and hydrogen by adsorption, inter alia, of carbon dioxide with a molecular sieve of 5A type in which the agglomeration binder is a clay binder of the family of the kaolinites.

[0012] Furthermore, it could be observed that the zeolitic adsorbent materials used in the decarbonation of natural gas too often undergo a premature ageing, this being the case in particular because of the risk of amorphization and/or pseudomorphism and/or mechanical degradation to which they are exposed during the phase of regeneration with a wet or nonwet gas comprising CO2. This premature ageing very obviously has a significant negative impact on the effectiveness and the overall productivity of the adsorption processes for the decarbonation of natural gas.

[0013] Other materials, such as porous metal-organic materials (Metal-Organic Framework or MOF materials), are also suggested for the decarbonation of natural gas, as described, for example, in Patent W02007111738. However, these materials are only

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PCT/FR2016/052203 — 3 — very slightly stable, indeed even unstable, in the presence of moisture, as indicated in the document “Progress in adsorption-based CO2 capture by metal-organic frameworks” (J. Liu et al., Chemical Society Reviews, 41, (2012), pp. 2308-2322).

[0014] A need thus remains for adsorbent materials, in particular zeolitic adsorbent materials, which are effective for the decarbonation of natural gas and which have large adsorption capacities and better adsorption/desorption kinetics, thus making it possible in particular to improve the processes for the decarbonation of natural gas, in particular the TSA, PSA or PTSA processes.

[0015] A need also remains for zeolitic adsorbent materials which are less impacted by the accelerated ageing often observed in processes for the decarbonation of natural gas. [0016] The Applicant Company has discovered that the abovementioned objectives can be achieved in all, or at least in part, by employing a zeolitic adsorbent material specifically dedicated to the process of the decarbonation of natural gas, in particular natural gas before liquefaction, and such as will now be described.

[0017] Thus, and according to a first aspect, the invention relates to the use, for the decarbonation of natural gas, of at least one zeolitic adsorbent material comprising:

a) from 70% to 99% by weight, preferably from 70% to 95% by weight, preferably again from 70% to 90% by weight, more preferably from 75% to 90% and very particularly from 80% to 90% of at least one zeolite A, with respect to the total weight of the zeolitic adsorbent material, and

b) from 1% to 30% by weight, preferably from 5% to 30% by weight, preferably again from 10% to 30% by weight, more preferably from 10% to 25% and very particularly from 10% to 20%, with respect to the total weight of the zeolitic adsorbent material, of at least one agglomeration binder comprising at least one clay chosen from fibrous magnesium clays. [0018] Unless otherwise indicated, in the present account, the limits of ranges of values of the expressions “from ... to ...” or “between ... and ...” are included in the said ranges of values.

[0019] The term “fibrous magnesium clays” is understood to mean the fibrous clays comprising magnesium and preferably hormites, the main representatives of which are sepiolite and attapulgite (or palygorskite). Sepiolite and attapulgite are the preferred hormites in the context of the present invention.

[0020] Preference is given in addition to zeolitic adsorbent material, the binder of which comprises only one or more clays of the family of the hormites. According to another embodiment, the binder comprises a mixture of clay(s) consisting of at least one fibrous magnesium clay, for example a hormite, and at least one other clay, for example chosen

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PCT/FR2016/052203 — 4 — from montmorillonites, for example bentonite. According to another preferred embodiment, preference is given to the binders comprising at least 50% by weight of at least one hormite with respect to the total weight of the binder. The preferred mixtures of clays are the sepiolite/bentonite and attapulgite/bentonite mixtures, more preferably the attapulgite/bentonite mixture, and entirely preferably these mixtures in which the hormites (sepiolite or attapulgite) are present at at least 50% by weight with respect to the total weight of the binder.

[0021] As indicated above, the zeolitic adsorbent material of use in the context of the present invention comprises at least one zeolite A. The said zeolite A present in the said zeolitic adsorbent material comprises one or more alkali metal and/or alkaline earth metal ions chosen from the sodium, potassium, calcium, barium, lithium or caesium ions, preferably from the sodium, potassium and calcium ions, more preferably from the calcium and sodium ions. Entirely preferably, the said zeolite A comprises calcium ions and typically calcium ions and sodium ions.

[0022] The zeolitic adsorbent material defined above can complementally comprise one or more additives and/or fillers well known to a person skilled in the art, such as, for example, pore-forming agents, carboxymethylcellulose (CMC), reinforcing agents in general, fibres (such as glass, carbon, Kevlar® and other fibres), carbon nanotubes (CNTs), colloidal silica, polymers, fabrics and others. The additive(s) and/or filler(s) represent a maximum of 10% by weight, preferably a maximum of 5% by weight, with respect to the total weight of the zeolitic adsorbent material which can be used in the context of the present invention.

[0023] According to a preferred embodiment, the zeolitic adsorbent material used in the context of the present invention comprises calcium, the content of which, expressed as calcium oxide (CaO), is between 9.0% and 21.0%, preferably between 10.0% and 20.0% and more preferably still between 12.0% and 17.0%, limits included, expressed as weight of CaO with respect to the total weight of the zeolitic adsorbent material.

[0024] The term “zeolite A” is understood to mean any zeolite LTA and in particular and preferably zeolites 5A, the pore opening of which is 5 Ά, and zeolites 5AHP or zeolites 5A with Hierarchical Porosity, as described, for example, in Application W02015/019013. Zeolites A are generally characterized by an Si/AI atomic ratio equal to 1 ± 0.05. According to a preferred embodiment, the zeolite A is chosen from zeolites 5A and zeolites 5APH. In a preferred embodiment, the zeolitic adsorbent used in the process of the invention exhibits a single zeolitic crystalline phase of LTA type.

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PCT/FR2016/052203 — 5 — [0025] According to a preferred embodiment, the zeolite 5A included in the zeolitic adsorbent material used in the context of the present invention exhibits a content of calcium, expressed as calcium oxide (CaO), of between 12.0% and 21.0%, preferably between 13.0% and 20.0% and more preferably still between 14.0% and 19.0%, limits included, expressed as weight of CaO with respect to the total weight of the zeolite.

[0026] The size (number-average diameter) of the zeolite LTA crystals used to prepare the zeolitic adsorbent material of the invention, and also the size of the zeolite LTA elements in the zeolitic adsorbent material, are measured by observation with the Scanning Electron Microscope (SEM). Preferably, the average diameter of the zeolite LTA crystals is between 0.1 pm and 20 pm, preferably between 0.5 pm and 20 pm and preferably again between 0.5 pm and 10 pm.

[0027] According to another preferred embodiment, the zeolitic adsorbent material used in the context of the present invention exhibits a water adsorption capacity H50 of between 16% and 25%, preferably between 18% and 23% and more preferably still between 19% and 22%. The measurement of the water adsorption capacity H50 is explained later in the description.

[0028] According to a preferred embodiment of the present invention, the Si/AI atomic ratio of the zeolitic adsorbent material is generally between 0.5 and 2.5, limits included, preferably between 1.0 and 2.0, preferably again between 1.0 and 1.8 and more preferably still between 1.0 and 1.6, limits included. The Si/AI atomic ratio of the zeolitic adsorbent material is determined according to the method described later in the present description.

[0029] The zeolitic adsorbent material as just defined for the decarbonation of natural gas can be prepared according to any method known to a person skilled in the art or starting from known methods, such as, for example, those described in the document “Zeolite Molecular Sieves: Structure, Chemistry, and Use” (D. W. Breck, (1974), Ed. John Wiley & Sons, pp. 267-274 and pp. 537-541).

[0030] The zeolitic adsorbent material described above can be provided in all types of forms known to a person skilled in the art, such as, for example, beads, extrudates, trilobes and others. Trilobe extrudates exhibit the advantage, in use, of limiting the pressure drops, with respect to other types of extrudates, pellets in particular. Preference is thus given to the agglomerated and shaped zeolitic adsorbent materials produced according to any technique known to a person skilled in the art, such as extrusion, compacting, agglomeration on a granulating plate or granulating drum, atomization and others.

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PCT/FR2016/052203 — 6 — [0031] The volume-average diameter (D50) of the zeolitic adsorbent material used in the process according to the invention is generally between 0.4 mm and 5.0 mm, preferably between 0.5 mm and 4.0 mm and preferably again between 0.6 mm and 3.8 mm. The method for measuring the volume-average diameter of the zeolitic adsorbent material is explained later in the description.

[0032] The zeolitic adsorbent material of use in the context of the present invention additionally has mechanical properties very particularly appropriate to the applications for which it is intended, in particular:

• a bed crushing strength (BCS), measured according to Standard ASTM 7084-04, of between 0.5 MPa and 6 MPa, preferably between 0.5 MPa and 4 MPa, preferably again between 0.5 MPa and 3 MPa and more preferably between 0.75 MPa and 2.5 MPa, for a material with a volume-average diameter (D50) or a length (greatest dimension when the material is not spherical) of less than 1 mm, or else • a grain crushing strength, measured according to Standards ASTM D4179 (2011) and ASTM D 6175 (2013), of between 0.5 daN and 20 daN, preferably of between 1 daN and 10 daN and preferably again between 1 daN and 8 daN, for a material with a volume-average diameter (D50) or a length (greatest dimension when the material is not spherical) of greater than or equal to 1 mm.

[0033] According to the present invention, the zeolitic adsorbent materials described above proved to be very particularly appropriate and effective in processes for the decarbonation of natural gas, in particular in pressure swing processes, either of PSA type, or of VSA type, or of VPSA type, or of RPSA type, or in temperature swing processes of TSA type and/or in processes of PTSA type.

[0034] More specifically, the present invention relates to the use of at least one zeolitic adsorbent material, comprising at least one zeolite LTA, preferably of 5A type, as defined above, for the decarbonation of natural gas using the abovementioned separating processes, preferably the TSA, PSA and PTSA processes and more preferably still the TSA process.

[0035] According to a preferred aspect of the present invention, the zeolitic adsorbent materials which can be used for the decarbonation of natural gas are particularly appropriate for the separation of the CO2 from a natural gas comprising less than 5% by volume of CO2, preferably less than 3% by volume of CO2 and preferably less than 2% by volume of CO2.

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PCT/FR2016/052203 — 7 — [0036] According to a preferred aspect of the present invention, the zeolitic adsorbent materials which can be used for the decarbonation of natural gas are particularly appropriate for the decarbonation of natural gas for NG plants, LNG plants and floating units, as described above, using the separating processes defined above.

[0037] According to a preferred aspect of the present invention, the zeolitic adsorbent materials which can be used for the decarbonation of natural gas can be combined with other adsorbent materials in one and the same separating process which are defined above. In particular, the zeolitic adsorbent materials defined according to the invention can be used in combination, as a mixture or separately, with one or more other zeolitic adsorbent materials comprising a zeolite chosen from zeolites 3A, 4A and 13X, and their mixtures, in order to carry out a complementary and/or supplementary decarbonation treatment and/or in order to remove other impurities, such as water, aromatic compounds and hydrocarbons.

[0038] In the case where the natural gas comprises impurities, such as water, in large amounts, it can be envisaged to remove the water by specific adsorption on a specific zeolitic adsorbent material, comprising a zeolite of, for example, 3A and/or 4A type or other adsorbents well known to a person skilled in the art, and then to lead the natural gas, no longer comprising water or only comprising minimum traces of water, into the decarbonation process according to the present invention.

[0039] In the case where the natural gas comprises impurities, such as aromatic hydrocarbons, in large amounts but also water, it can be envisaged to remove these impurities by specific adsorption on a zeolitic adsorbent material, advantageously comprising a zeolite of 13X type, or on silica gel or other adsorbents well known to a person skilled in the art, and then to lead the natural gas, no longer comprising aromatic hydrocarbons or water or only comprising minimum traces of aromatic hydrocarbons and water, into the decarbonation process according to the present invention.

[0040] When the natural gases comprise several impurities, in particular those defined above, it is thus possible to envisage one or more treatments by adsorption on zeolitic adsorbent materials and then to carry out the treatment for decarbonation of natural gas according to the present invention. The process for removing the impurities which are defined above combined with the decarbonation treatment defined above also forms part of the present invention.

[0041] It is also possible to carry out all these treatments, subsequent or prior to or simultaneously with the treatment for the decarbonation of natural gas as defined above, with adsorbent beds (zeolitic adsorbent materials or other adsorbents well known to a

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PCT/FR2016/052203 — 8 — person skilled in the art, for example silica gel, active charcoal, activated alumina, metal oxide and others), separated and/or mixed. The term “mixed beds” is understood to mean mixtures of two or more different adsorbents or superimpositions of two or more different adsorbents, indeed even alternating or nonalternating layers of different adsorbents.

[0042] According to another aspect, the present invention relates to a process for the decarbonation of natural gas comprising at least the following stages:

• providing a natural gas comprising carbon dioxide, • bringing the said natural gas into contact with at least one zeolitic adsorbent material as defined above, and • recovering the decarbonated natural gas.

[0043] The decarbonation process according to the present invention is particularly appropriate for the decarbonation of natural gas comprising less than 5% by volume of CO2, preferably less than 3% by volume of CO2 and preferably less than 2% by volume of CO₂.

[0044] As indicated above, the process of the decarbonation of natural gas discussed above in the context of the present invention is very particularly appropriate for NG plants, LNG plants and floating units, such as offshore units, FLNG (Floating Liquefied Natural Gas) units, FPSO (Floating Production Storage Offloading) units and others.

[0045] Thus, and according to yet another aspect, the present invention relates to a unit for the decarbonation of natural gas, for example as defined above, comprising at least one zeolitic adsorbent material as described above for the decarbonation of natural gas.

Characterization techniques [0046] The physical properties of the zeolitic adsorbent materials which can be used in the present invention are evaluated by methods known to a person skilled in the art and defined below.

Size of the zeolite LTA crystals [0047] The number-average diameter of the zeolite LTA crystals present in the zeolitic adsorbent materials and which are used for the preparation of the said zeolitic adsorbent material is estimated by observation using a Scanning Electron Microscope (SEM), optionally after fracturing the samples of zeolitic adsorbent material.

[0048] In order to estimate the size of the zeolitic crystals on the samples, a group of photographs is taken at a magnification of at least 5000. The diameter of at least 200 crystals is subsequently measured using dedicated software, for example the Smile View software from the editor LoGraMi. The accuracy is of the order of 3%.

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PCT/FR2016/052203 — 9 —

Particle size determination of the zeolitic adsorbent materials [0049] The volume-average diameter (D50, or length, that is to say greatest dimension when the material is not spherical) of the zeolitic adsorbent material of the process of the invention is determined by analysis of the particle size distribution of a sample of adsorbent material by imaging according to Standard IS0 13322-2:2006, using a conveyor belt which makes it possible for the sample to pass in front of the lens of the camera.

[0050] The volume-average diameter is subsequently calculated from the particle size distribution by applying Standard ISO 9276-2:2001. In the present document, the term “volume-average diameter” or else “size” is employed for the zeolitic adsorbent materials. The accuracy is of the order of 0.01 mm for the size range of the adsorbent materials of use in the context of the present invention.

Chemical analysis of the zeolitic adsorbent materials - Si/AI atomic ratio and calcium oxide (CaO) content [0051] An elemental chemical analysis of a zeolitic adsorbent material described above can be carried out according to different analytical techniques known to a person skilled in the art. Mention may be made, among these techniques, of the technique of chemical analysis by X-ray fluorescence, such as described in Standard NF EN ISO 12677: 2011, on a wavelength dispersive spectrometer (WDXRF), for example Tiger S8 from Bruker.

[0052] X-ray fluorescence is a non-destructive spectral technique which makes use of the photoluminescence of the atoms in the X-ray region to establish the elemental composition of a sample. The excitation of the atoms, which is most often and generally produced by a beam of X-rays or by bombardment with electrons, generates specific radiation after return to the ground state of the atom. There is obtained, conventionally, after calibrating, for each oxide, an uncertainty of measurement of less than 0.4% by weight.

[0053] Other analytical methods are, for example, illustrated by the atomic absorption spectrometry (AAS) and inductively coupled plasma-atomic emission spectrometry (ICPAES) methods described in Standards NF EN ISO 21587-3 and NF EN ISO 21079-3 on an appliance of Perkin Elmer 4300DV type, for example.

[0054] The X-ray fluorescence spectrum has the advantage of not depending very much on the chemical combination of the element, which provides a precise determination, both quantitative and qualitative. There is obtained, conventionally, after calibrating, for each oxide S1O2 and AI2O3, and also CaO, an uncertainty of measurement of less than 0.4% by weight.

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PCT/FR2016/052203 — 10 — [0055] The elemental chemical analyses described above make it possible to simultaneously confirm the Si/AI atomic ratio of the zeolite used within the zeolitic adsorbent material, the Si/AI atomic ratio of the zeolitic adsorbent material and the calcium oxide content, expressed as weight of CaO, of the zeolitic adsorbent material. In the description of the present invention, the uncertainty of measurement of the Si/AI atomic ratio is ± 5%. The Si/AL atomic ratio of the zeolite present in the adsorbent material can also be measured by solid-state silicon Nucleic Magnetic Resonance (NMR) spectroscopy.

Mechanical strength of the zeolitic adsorbent materials [0056] The bed crushing strength (BCS) of the zeolitic adsorbent materials as are described in the present invention is characterized according to Standard ASTM 7084-04. The grain crushing mechanical strengths are determined with a “Grain Crushing Strength” device sold by Vinci Technologies, according to Standards D4179 (2011) and ASTM D 6175 (2013).

Loss on ignition of the zeolitic adsorbents [0057] The loss on ignition is determined in an oxidizing atmosphere, by calcination of the sample in air at a temperature of 950°C ± 25°C, as described in Standard NF EN 196-2 (April 2006). The measurement standard deviation is less than 0.1%.

Qualitative and quantitative analysis by X-ray diffraction [0058] The content of zeolite A in the zeolitic adsorbent material is evaluated by X-ray diffraction (XRD) analysis according to methods known to a person skilled in the art. This identification can be carried out by means of an XRD device having the Bruker trademark. [0059] This analysis makes it possible to identify the different zeolites present in the zeolitic adsorbent material as each of the zeolites has a unique diffractogram defined by the positioning of the diffraction peaks and by their relative intensities.

[0060] The zeolitic adsorbent materials are ground and then spread and smoothed over a sample holder by simple mechanical compression.

[0061] The conditions for acquisition of the diffractogram produced on the Bruker D5000 device are as follows:

Cu tube used at 40 kV - 30 mA;

size of the slits (divergent, scattering and analysis) = 0.6 mm;

filter: Ni;

rotating sample device: 15 rev.min^-1;

measurement range: 3° < 20 < 50°;

step: 0.02°;

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PCT/FR2016/052203 — 11 — • counting time per step: 2 seconds.

[0062] The diffractogram obtained is interpreted with the EVA software with identification of the zeolites using the ICDD PDF-2, release 2011, base.

[0063] The amount of the zeolite A fractions, by weight, is measured by XRD in the analysis; this method is also used to measure the amount of the fractions of zeolites other than zeolite A. This analysis is carried out on the D5000 device having the Bruker trademark and then the amount by weight of the zeolite fractions is evaluated by means of the TOPAS software from Bruker.

Measurement of the water adsorption capacity H50 [0064] The water adsorption capacity H50 is measured by a static method which consists in measuring the increase in weight of the zeolitic adsorbent material, placed in a leaktight chamber for 24 hours in equilibrium with an atmosphere controlled at 50% relative humidity and at ambient temperature (22°C). The water adsorption capacity, as a percentage, is expressed by the difference in weight between the zeolitic adsorbent material after and before the test described above, divided by the weight of the zeolitic adsorbent material before the test described above. The measurement standard deviation is less than 0.3%.

Examples [0065] The present invention is now illustrated by means of the following examples which do not in any way limit the field of the invention, the scope of protection of which is conferred by the claims. In that which follows, a weight expressed as “anhydride equivalent” means a weight of product decreased by its loss on ignition.

[0066] The zeolitic adsorbent materials used in the examples which follow are prepared in the form of extrudates with a diameter of 1.6 mm and with a length from 5 mm to 7 mm. The zeolitic adsorbent materials tested are described below.

Sample A: zeolitic (zeolite 4A) adsorbent material Siliporite® NK 10, sold by CECA S.A. Sample B: zeolitic (zeolite 13X) adsorbent material Siliporite® G5, sold by CECA S.A. Sample C: preparation of a zeolitic adsorbent material obtained by extruding a mixture of zeolite 5A (80% by weight, anhydrous equivalent) and kaolin (20% by weight, anhydrous equivalent) as agglomeration binder, according to techniques well known to a person skilled in the art, such as described, for example, in US 3 219 590. The size of the zeolite 5A crystals is 7.5 pm. The CaO content of the zeolitic adsorbent material is 12.3% by weight, its Si/AI ratio is 1.01 and its water adsorption capacity H50 is 20.5%

Sample D: preparation of a zeolitic (zeolite 5A) adsorbent material similar to Sample C, the kaolin being replaced with attapulgite. The CaO content of the zeolitic adsorbent

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PCT/FR2016/052203 — 12 — material is 12.4% by weight, its Si/AI ratio is 1.33 and its water adsorption capacity H50 is 20.6%.

Sample E: preparation of a zeolitic adsorbent material similar to Sample D, the zeolite 5A being replaced with zeolite Y (CBV 100 from Zeolyst International).

Sample F: preparation of a zeolitic (zeolite 5A) adsorbent material similar to Sample D, attapulgite being replaced with a mixture by weight of 2 parts of attapulgite and 1 part of montmorillonite. The CaO content of the zeolitic adsorbent mixture is 12.2% by weight, its Si/AI ratio is 1.30 and its water adsorption capacity H50 is 20.5%.

[0067] An amount of 725 g of each of the samples is charged to a pilot plant for the decarbonation (pilot plant for adsorption of carbon dioxide) of natural gas equipped with an adsorption column, the internal diameter of which is 27 mm, and where the height of the adsorbent bed is 2 m. The incoming natural gas comprises 1.2% (% by volume) of CO2 and 91% (% by volume) of methane, the remainder being other hydrocarbons (ethane, propane). The flow rate is 12 m³/h, the pressure is 6 MPa and the temperature is 40°C.

Example 1 [0068] The CO2 adsorption capacities, expressed as the percentage by weight (g of CO2 adsorbed per 100 g of zeolitic adsorbent material), are presented in Table 1 and are calculated in the following equation:

Capacity =

Q_gas ^x[C0₂]^xt5o

Weight x 10 where • Qgas represents the mean flow rate of the gas stream in Sm³/h, • [CO2] represents the mean concentration at the inlet of CO2 in ppm, • t₅₀ represents the stochiometric time in hours, the time reached when the concentration of CO2 at the outlet of the column is equal to 50% of the mean CO2 concentration at the inlet of the column, and • Weight represents the weight of zeolitic adsorbent material (in grams).

[0069] The results of the tests on the pilot plant indicate that Sample D, consisting of zeolite 5A with a CaO content of 12.4% and agglomerated with a binder of attapulgite type, exhibits the greatest CO2 adsorption capacity. The results are presented in Table 1 below:

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PCT/FR2016/052203 — 13 —

- Table 1 -

Sample A	Sample B	Sample C	Sample D	Sample E	Sample F
8.2%	10.2%	11.9%	12.3%	5.8%	12.1%

Example 2 [0070] The mass transfer zones (MTZ), expressed in centimetres, of the CO2 over the zeolitic adsorbent materials are presented in Table 2 and are calculated from the following equation below. The lower the MTZ value of the zeolitic adsorbent material, the faster the kinetics of adsorption of the zeolitic adsorbent material.

k/lT7 — to _v ^X (^50 tcolumn) ^{M 1 Z} ~ ^breakthrough ^X-------7--------Eo where • MTZ represents the mass transfer zone, in centimetres, • Hcoiumn represents the height of the column, in centimetres, • tbreakthrough represents the breakthrough time, in hours, as described in the work “Encyclopedia of Chemical Processing and Design”, 28 May 1999, Vol. 67, pp. 384-385 : “Zeolites”, John J. McKetta Jr., CRC Press, 500 pages, • t₅₀ represents, in hours, the time reached when the CO2 concentration at the outlet of the column is equal to 50% of the mean CO2 concentration at the column inlet.

[0071] The results of the tests on the pilot plant indicate that Sample D, consisting of zeolite 5A agglomerated with attapulgite, exhibits a shorter MTZ and thus faster kinetics of adsorption of CO2 than the material agglomerated with kaolin (Sample C).

[0072] The zeolitic adsorbent material based on zeolite 5A agglomerated with attapulgite is thus very particularly appropriate for the decarbonation of natural gas. The results are presented in Table 2 below.

- Table 2 -

Sample C	Sample D	Sample F
126 cm	93 cm	97 cm

Example 3 [0073] Accelerated ageing tests are carried out on samples of the zeolitic adsorbent materials C and D by bringing each sample into contact with pure carbon dioxide at a

WO 2017/042466

PCT/FR2016/052203 — 14 — temperature close to those used during the regeneration of the zeolitic adsorbent materials in an industrial TSA process (180°C) for 3 months. This duration of 3 months is representative of the total duration of bringing into contact with the hot regeneration gas in an industrial unit. The CO2 pressure is maintained at 5 bar for the duration of the test. 5 After cooling and rendering inert with nitrogen, the sample of zeolitic adsorbent material is discharged for evaluation of the mechanical crushing strength (MS).

[0074] The initial mechanical crushing strengths of the zeolitic adsorbent materials C and D, and also the values obtained after accelerated ageing tests described above, are presented in Table 3.

- Table 3 -

	Sample C	Sample D	Sample F
Initial MS	4.0	3.5	3.7
MS after ageing	2.2	3.0	3.2

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2016319478 11 Jul 2019

Claims

1. The use, for the decarbonation of natural gas, of at least one zeolitic adsorbent material comprising:

a) from 70% to 99% by weight of at least one zeolite A, with respect to the total weight of the zeolitic adsorbent material, and

b) from 1% to 30% by weight, with respect to the total weight of the zeolitic adsorbent material, of at least one agglomeration binder comprising at least one clay chosen from fibrous magnesium clays.

2. The use as claimed in claim 1, in which the fibrous magnesium clays are hormites and are preferably chosen from sepiolite and attapulgite.

3. The use as claimed in claim 1 or claim 2, in which the binder comprises a mixture of clay(s) consisting of at least one fibrous magnesium clay and at least one other clay.

4. The use according to any one of the preceding claims, in which the zeolite A comprises calcium ions and typically calcium ions and sodium ions.

5. The use according to any one of the preceding claims, in which the zeolitic adsorbent material comprises calcium, the content of which, expressed as calcium oxide (CaO), is between 9.0% and 21.0%, limits included, expressed as weight of CaO with respect to the total weight of the zeolitic adsorbent material.

6. The use according to any one of the preceding claims, in which the zeolite A is chosen from zeolites 5A and zeolites 5APH.

7. The use according to any one of the preceding claims, in which the Si/AI atomic ratio of the zeolitic adsorbent material is between 0.5 and 2.5, limits included.

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2016319478 11 Jul 2019

8. The use according to any one of the preceding claims, in which the process for the decarbonation of natural gas is a TSA process, or a PSA process or a PTSA process.

9. The use according to any one of the preceding claims, in which the zeolitic adsorbent material is used in combination, as a mixture or separately, with one or more other zeolitic adsorbent materials comprising a zeolite chosen from zeolites 3A, 4A and 13X, and their mixtures.

10. A process for the decarbonation of natural gas comprising at least the following stages:

providing a natural gas comprising carbon dioxide, bringing the said natural gas into contact with at least one zeolitic adsorbent material as defined in any one of claims 1 to 7, and recovering the decarbonated natural gas.

11. The process as claimed in claim 10, in which the natural gas brought into contact with the said at least one zeolitic adsorbent material comprises less than 5% by volume of CO₂.

12. The unit for the decarbonation of natural gas, comprising at least one zeolitic adsorbent material as defined in any one of claims 1 to 7.

13. The unit for the decarbonation of natural gas as claimed in claim 12, which is an NG plant, an LNG plant, a floating unit, an offshore floating unit, an FLNG unit or an FPSO unit.