Zeolite adsorbents for the separation of hydrocarbon isomers.

Abstract

The present invention relates to a zeolite adsorbent agglomerate comprising at least one zeolite of the faujasite type containing barium and / or potassium, wherein the particle porosity is between 25% and 45% and the standard deviation σ of the crystal size distribution in the agglomerate is less than 0.30 μm. The present invention also relates to the use of the zeolite adsorbent agglomerate in the separation of hydrocarbon mixtures and to a method for separating hydrocarbon mixtures using the zeolite adsorbent agglomerate.

Description

[Technical Field]

[0001] The present invention relates to a zeolitic adsorbent in the form of an aggregate comprising a faujasite-type zeolite for the separation of gaseous or liquid mixtures of aromatic hydrocarbons, and more particularly to a process for the separation of xylenes, and in particular para-xylene, with improved productivity.

[0002] The present invention further relates to a process for separating gaseous or liquid mixtures of isomers with improved productivity, and more particularly to a process for separating xylene isomers with improved productivity to produce high purity para-xylene from an aromatic hydrocarbon feed containing an isomer having 8 carbon atoms. [Background technology]

[0003] The use of zeolitic adsorbents consisting of faujasite zeolite of type X or Y (FAU) containing, in addition to sodium cations, barium, potassium, or strontium ions, either alone or in mixtures, for the selective adsorption of para-xylene in a mixture of aromatic hydrocarbons is well known in the art.

[0004] Patent Documents 1, 2, 3, and 4 show that a zeolite adsorbent containing an aluminosilicate containing sodium and barium (Patent Document 5), or a zeolite adsorbent containing an aluminosilicate containing sodium, barium, and potassium, is effective in separating para-xylene present in a C8 aromatic fraction (a fraction containing aromatic hydrocarbons having 8 carbon atoms).

[0005] The adsorbents described in US Pat. No. 5,629,493 are used as adsorbents in liquid phase processes, preferably in simulated countercurrent (countercurrent) liquid phase processes similar to the liquid phase process described in US Pat. No. 5,629,493, which liquid phase process is particularly applicable to C8 aromatic fractions.

[0006] It is an object of the present invention to improve the productivity of existing processes for producing para-xylene, particularly liquid phase processes, preferably simulated countercurrent processes for separating xylene isomers from a C aromatic feed. Surprisingly, it has been observed that this productivity can be improved by judicious selection of the properties of the zeolite adsorbent aggregates used in this type of process.

[0007] Separation in a simulated moving bed should be interpreted in its broadest sense in this application, i.e., it may refer to a simulated countercurrent moving bed, a simulated cocurrent moving bed, or it may refer to the so-called "Varicol" process. The Varicol process, proposed by [Non-Patent Document 1] and later developed by Novasep, allows for the desynchronization of the inlet and outlet lines (Non-Patent Document 2). The lengths of the four zones can be adjusted during a cycle, limiting the number of beds required to perform the separation.

[0008] A common feature of this group of processes is that the zeolite adsorbent aggregates (or simply "solid adsorbent") are placed in a fixed bed, and the liquid flow in contact with the solid adsorbent is controlled by a set of "on-off" valves or by a single composite valve known as a "rotary valve".

[0009] The active component of the solid adsorbents used as adsorption agents in these processes is zeolite, and the zeolites obtained in crystalline form are preferably used in the form of agglomerates on an industrial scale. These zeolite adsorbents, agglomerated in the form of laminates, beads or extrudates, generally consist of zeolite crystals, which form the active component in terms of adsorption, and a binder intended to ensure the cohesion of the crystals in the form of agglomerates. This binder also gives the agglomerates sufficient mechanical strength to withstand the mechanical stresses to which they are subjected when used in operating equipment. These mechanical stresses are responsible for the formation of "fines," which deteriorate the performance during the operating time of the process.

[0010] Methods for separating xylene by simulated moving bed (SMB) have been subject to many technical improvements, especially with respect to the liquid distribution plates, but relatively little progress has been made with regard to the intrinsic properties of the solid adsorbent.

[0011] Adsorbents for xylene separation with improved transportability for xylene separation are described, for example, in Patent Document 8, which has crystals with a size of less than 1.7 μm and a small Si / Al atomic ratio such as 1.15 < Si / Al ≦ 1.5, is exchanged with barium, and in some cases is exchanged with potassium in Patent Document 9, which describes an aggregated zeolite adsorbent having properties optimal for separating para-xylene from a C8 aromatic fraction in particular. These adsorbents exhibit the best properties for para-xylene selectivity and mass transfer, while having the greatest mechanical strength related to optimized adsorption capacity.

[0012] Patent Document 10 proposes a zeolite adsorbent in the form of an aggregate having properties optimal for separating isomeric gaseous or liquid mixtures, more specifically for separating xylene in the gas phase or liquid phase, and particularly for separating para-xylene from a C8 aromatic fraction. The zeolite adsorbent of the invention exhibits the best properties for para-xylene selectivity and mass transport, while having improved strength and a high adsorption capacity per unit volume of the adsorbent, and is particularly suitable for use in a method for separating para-xylene in the liquid phase, preferably a simulated countercurrent separation method.

[0013] In particular, this document teaches that a large increase in macroporosity and / or mesoporosity, and thus the porosity of the particles, is not desirable because this porosity is not involved in the adsorption capacity. Optimization of diffusivity and adsorption capacity was obtained by specifically selecting both porosity and the twist factor.

[0014] Patent Document 11 describes a separation method using an adsorbent having a low binder content and containing X-type faujasite crystals with a nanometer size, typically an average dimension of less than 500 nm.

[0015] In a process for separating xylenes by simulated moving bed adsorption, a zeolite adsorbent is contacted with a liquid feed stream (feed mixture) which is very often a mixture of C hydrocarbons, and generally and very often a mixture of xylene isomers, more particularly ortho-xylene, meta-xylene, para-xylene and ethylbenzene.

[0016] By using a zeolite adsorbent containing a faujasite structure zeolite having a Si / Al ratio of 1.0 to 1.5 (zeolite LSX, MSX, X) and exchanged with barium or mostly barium and some potassium, para-xylene is adsorbed in the zeolite pores in preference to all other hydrocarbon compounds in the feed stream. The adsorbed phase in the zeolite pores becomes enriched in para-xylene compared to the initial mixture forming the feed stream. In contrast, the liquid phase becomes enriched in compounds such as ortho-xylene, meta-xylene, and ethylbenzene in a greater relative proportion than the liquid phase characterizing the initial mixture forming the feed stream.

[0017] The liquid phase is removed from contact with the adsorbent to form a raffinate stream, and the para-xylene-rich adsorbed phase is desorbed under the action of a desorbent stream and removed from contact with the adsorbent to form an extract stream.

[0018] In a process for separating xylenes by adsorption in a simulated moving bed, a solid zeolite adsorbent is passed through one or two multistage columns to contact a liquid stream. The multistage columns consist of a number of plates arranged along a substantially vertical axis, each plate supporting a bed of particulate solids, and different successive beds sequentially receiving a lateral permeate flow of one or more liquids used in the column. Between two successive beds is a liquid distribution device that feeds each bed of particulate solids.

[0019] In general, the operation of a column in a simulated moving bed can be described as follows:

[0020] The column contains at least four sections, and sometimes five or six sections, each of which is composed of a number of successive beds, and each section is defined by its location between an inlet line and an outlet line. Typically, a simulated countercurrent flow unit (SCC) for the production of para-xylene is supplied with at least one feed F (a feed mixture of aromatic hydrocarbons composed of isomers having eight carbon atoms) to be fractionated and a desorbent D, sometimes called an eluent (commonly para-diethylbenzene or toluene), and removes from the unit at least one raffinate containing slightly selectively adsorbed and desorbed feed products, and an extract E containing very heavily adsorbed and desorbed feed products.

[0021] Other inlet and outlet lines can be added to rinse the distribution circuit, for example, as described in U.S. Patent No. 5,929,999. Because the addition of these additional rinse streams in no way changes the operating principle of the SCC unit, for the sake of brevity we will not include these additional inlet and outlet lines in the description of the process of the present invention.

[0022] The inlet and outlet lines are varied in time and moved in the same direction by a value corresponding to one bed. The movement of the various inlet or outlet lines may or may not be simultaneous as taught in U.S. Pat. No. 5,629,499. This second mode of operation is called Varicol.

[0023] Typically, four different chromatographic zones are defined in a column operated in simulated countercurrent flow (SCC). Zone 1: desorption zone of the highly adsorbed product in the feed, located between the injection of the desorbent D and the withdrawal of the extract E. Zone 2: desorption zone of the less selectively adsorbed products in the feed, located between the extract E and the injection of the feed to be fractionated. Zone 3: adsorption zone of the highly adsorbed product of the feed, located between the injection of the feed and the withdrawal of the raffinate R. Zone 4: Located between the withdrawal of raffinate R and the injection of desorbent D.

[0024] To improve the productivity of separation processes, the prior art teaches that one way is to improve the overall transport to the zeolite adsorbent aggregates, in particular by reducing the crystal size and / or the average size of the aggregates.

[0025] A prior art document disclosing a process for pharmaceutical separations (Non-Patent Document 3) describes a liquid phase chromatographic separation process using aggregates with sizes ranging from tens of micrometers up to 100 μm.

[0026] In these processes using very small size adsorbents, the pressure drop ΔP is very large. For xylene separation processes, such levels of pressure drop ΔP are not frequent. Yet, surprisingly, it has been observed that pressure drop ΔP is not a sizing criterion. It has a particular impact on the adsorbent wall thickness and the power of the operating unit.

[0027] A further characteristic of zeolite adsorbent aggregates is their hydration rate. When used in a simulated moving bed xylene separation process by adsorption, maintaining the hydration of the zeolite at a desired value, e.g., maintaining losses by combustion of 4% to 7.7% for zeolite X, MSX, or LSX, is ensured by adding water to the feed stream and / or desorbent stream. The amount of water to be added for such levels of losses by combustion is such that the weight content of water in the hydrocarbon effluent (extract or raffinate stream) is most often between 0 ppm and 150 ppm, more commonly between 40 ppm and 150 ppm, when the adsorbent comprises X, MSX, or LSX.

[0028] Nevertheless, there is a general and constant need to increase the productivity of the above processes. [Prior art documents] [Patent documents]

[0029] [Patent Document 1] U.S. Patent No. 3,558,730 [Patent Document 2] U.S. Patent No. 3,558,732 [Patent Document 3] U.S. Patent No. 3,626,020 [Patent Document 4] U.S. Patent No. 3,663,638 [Patent Document 5] U.S. Patent No. 3,960,774 [Patent Document 6] U.S. Patent No. 3,878,127 [Patent Document 7] U.S. Patent No. 2,985,589 [Patent Document 8] International Publication No. WO2008 / 009845 [Patent Document 9] International Publication No. WO2014 / 090771 [Patent Document 10] International Publication No. WO2018 / 002174 [Patent Document 11] U.S. Patent Application Publication No. 2009 / 0326308 [Patent Document 12] U.S. Patent No. 7,208,651 [Patent Document 13] U.S. Patent No. 6,136,198 [Non-patent literature]

[0030] [Non-Patent Document 1] Ludemann-Hombourger(O.Ludemann-Hombourger,R.Nicoud,2000) [Non-patent document 2] Bailly et al., 2004 [Non-patent document 3] Gomes et al. (2006), Adsorption, Vol. 12, pp. 375ff. Summary of the Invention [Problem to be solved by the invention]

[0031] It is therefore a first object of the present invention to propose a zeolitic adsorbent in the form of an aggregate having optimal properties for the separation of gaseous or liquid mixtures of isomers, and more particularly for the separation of xylenes in the gas or liquid phase, in particular the separation of para-xylene from the C aromatic fraction. The zeolitic adsorbent aggregates of the present invention in particular exhibit the best properties of para-xylene selectivity and mass transport, while possessing high mechanical strength and adsorption capacity, and are particularly suitable for use in a liquid-phase separation process of para-xylene, preferably of the simulated countercurrent type.

[0032] To this end, the present invention proposes an agglomerated adsorbent, preferably of faujasite zeolite, having an Si / Al atomic ratio between 1.00 and 1.50 and whose particle porosity is advantageously between 25% and 45%, which makes it possible to produce high-purity para-xylene with improved productivity while avoiding deterioration of its performance over time. More particularly, the present invention relates to an agglomerated zeolitic adsorbent comprising at least one faujasite zeolite (FAU-X) having an Si / Al atomic ratio between 1.00 and 1.50 (inclusive), and preferably containing barium and optionally potassium, wherein first, the particle porosity is between 25% and 45%, preferably between 30% and 45%, more preferably between 32% and 45%, more preferably between 35% and 45%, and particularly advantageously between 36% and 45%, inclusive; and second, the standard deviation σ of the crystallite size distribution in the agglomerates is less than 0.30 μm, preferably between 0.05 μm and 0.30 μm, more preferably between 0.05 μm and 0.28 μm, even more preferably between 0.1 μm and 0.28 μm, and most preferably between 0.1 μm and 0.25 μm (inclusive). [Means for solving the problem]

[0033] Thus, in a first aspect, the present invention relates to an agglomerated adsorbent comprising at least one faujasite zeolite (FAU-X) having an Si / Al atomic ratio between 1.00 and 1.50 (inclusive), and barium and optionally potassium, characterized firstly in that the particle porosity of the adsorbent is between 25% and 45%, preferably between 30% and 45%, more preferably between 32% and 45%, more preferably between 35% and 45%, and particularly advantageously between 36% and 45%, inclusive, and secondly in that the standard deviation σ of the crystal size distribution in the agglomerates is less than 0.30 μm, preferably between 0.05 μm and 0.30 μm, more preferably between 0.05 μm and 0.28 μm, even more preferably between 0.1 μm and 0.28 μm, and most preferably between 0.1 μm and 0.25 μm, inclusive.

[0034] In one embodiment, the agglomerated zeolite adsorbent of the present invention comprises number average The zeolite crystals have a diameter of less than 1200 nm, preferably between 100 nm and 1200 nm, more preferably between 400 nm and 1200 nm, even more preferably between 500 nm and 1200 nm, even more preferably between 550 nm and 1200 nm, and most advantageously between 600 nm and 1200 nm, inclusive.

[0035] In another embodiment, the agglomerated zeolite adsorbent of the present invention is in the form of beads having an average diameter of from 100 μm to 1000 μm, preferably from 100 μm to 600 μm, more preferably from 200 μm to 550 μm, inclusive.

[0036] In one preferred embodiment, the at least one FAU-X zeolite of the agglomerated zeolitic adsorbent of the present invention has an Si / Al atomic ratio of from 1.05 to 1.50, preferably from 1.05 to 1.40 inclusive, more preferably from 1.10 to 1.40 inclusive.

[0037] In another preferred embodiment of the present invention, no zeolitic structures other than the faujasite structure, preferably other than the faujasite X structure, have been detected by X-ray diffraction in the agglomerated zeolitic adsorbent of the present invention.

[0038] Furthermore, the weight fraction of FAU zeolite, preferably the weight fraction of FAU-X zeolite, is preferably 80% or more of the total weight of the agglomerated zeolite adsorbent of the present invention.

[0039] The agglomerated zeolite adsorbent of the present invention contains one or more alkali or alkaline earth ions, preferably ions selected from sodium, barium and potassium.

[0040] In one preferred embodiment, the barium content in the agglomerated zeolite adsorbent of the present invention, expressed as barium oxide (BaO), is greater than 10% by weight, more preferably greater than 15% by weight, even more preferably greater than 20% by weight, even more preferably greater than 23% by weight, and even more preferably greater than 33% by weight, and the barium content is advantageously between 23% and 42% by weight, and typically between 30% and 40% by weight (inclusive), relative to the total weight of the adsorbent.

[0041] In another preferred embodiment, the potassium content in the agglomerated zeolite adsorbent of the present invention, expressed as potassium oxide (KO), is less than 25% by weight, preferably from 0 to 20% by weight, more preferably from 0 to 15% by weight, inclusive, based on the total weight of the adsorbent.

[0042] In one embodiment of the invention, the agglomerated zeolite adsorbent of the invention has a loss on combustion of not more than 7.7%, preferably from 0 to 7.7%, more preferably from 3.0% to 7.7%, even more preferably from 3.5% to 6.5%, and advantageously from 4.5% to 6%, inclusive, measured at 900°C according to standard NF EN 196-2.

[0043] In another aspect, the present invention relates to the use of an agglomerated zeolite adsorbent as described herein in the following method: -C8 aromatic isomer fraction and in particular xylenes, more particularly para-xylene; - separation of isomers of substituted toluenes, such as nitrotoluene, diethyltoluene, toluenediamine and others; - Separation of cresols; -Polyhydric alcohol separation.

[0044] Finally, in a further aspect, the present invention relates to a process for separating para-xylene from an aromatic isomer fraction having eight carbon atoms using an agglomerated zeolite adsorbent as defined above and more particularly as described hereinafter as a para-xylene adsorbent.

[0045] The process for separating para-xylene from the isomeric fraction of aromatic hydrocarbons having 8 carbon atoms according to the present invention is carried out by adsorption of para-xylene in the gas or liquid phase, preferably in the liquid phase, in the presence of a desorbent, which is preferably selected from toluene and para-diethylbenzene.

[0046] In one preferred embodiment, the process for separating para-xylene according to the present invention is a simulated moving bed process, more preferably a simulated countercurrent process. DETAILED DESCRIPTION OF THE INVENTION

[0047] The zeolite adsorbent of the present invention preferably comprises macropores, mesopores, and micropores. By "macropores" we mean pores with openings larger than 50 nm, preferably between 50 nm and 400 nm. By "mesopores" we mean pores with openings between 2 nm and 50 nm (inclusive). By "micropores" we mean pores with openings smaller than 2 nm.

[0048] As previously indicated, the adsorbent of the present invention is in the form of an adsorbent having a particle porosity of from 25% to 45%, preferably from 30% to 45%, more preferably from 32% to 45%, even more preferably from 35% to 45%, and particularly advantageously from 36% to 45%, inclusive, and the standard deviation σ of the crystal size distribution in the adsorbent is less than 0.30 μm, preferably from 0.05 μm to 0.30 μm, more preferably from 0.05 μm to 0.28 μm, even more preferably from 0.10 μm to 0.2 μm, and most preferably from 0.10 μm to 0.25 μm, inclusive.

[0049] The present inventors have surprisingly discovered that when the standard deviation σ of the crystal size distribution in the zeolite adsorbent is greater than 0.30 μm, a dramatic drop in productivity is observed in para-xylene separation processes, particularly in liquid-phase separation processes in simulated countercurrent moving beds.

[0050] Even more surprisingly, it was also found that this productivity value reaches a maximum for zeolite adsorbent agglomerates with a standard deviation σ of the crystal size distribution of less than 0.30 μm. This standard deviation σ value appears to correspond to an optimum particle porosity. In a completely surprising manner, it was also observed that for zeolite adsorbent agglomerates, particle porosity is inversely proportional to the standard deviation σ of the crystal size distribution. Thus, the more the standard deviation σ decreases, the greater the particle porosity. Nevertheless, too high a particle porosity can lead to quite undesirable effects, such as loss of adsorption capacity, loss of mechanical strength, etc.

[0051] As a result, those skilled in the art who desire maximum productivity from the present invention will find a compromise between particle porosity and the standard deviation σ of the crystal size distribution in the zeolite adsorbent agglomerate. Thus, the agglomerated adsorbents of the present invention can be used to obtain maximum productivity in xylene separation processes.

[0052] Advantageously, the agglomerated zeolite adsorbent is in the form of beads having an average diameter of between 100 μm and 1000 μm, preferably between 100 μm and 600 μm, more preferably between 200 μm and 550 μm, inclusive.

[0053] Preferably, the faujasite zeolite adsorbent of the present invention contains barium and, optionally, potassium.

[0054] In a further embodiment of the invention, the zeolitic adsorbent has a barium content, expressed as barium oxide (BaO), of greater than 10% by weight, preferably greater than 15% by weight, more preferably greater than 20% by weight, even more preferably greater than 23% by weight, or even greater than 33% by weight, relative to the total weight of the adsorbent. Advantageously, the barium content is between 23% and 42% by weight, and typically between 30% and 40% by weight, inclusive, relative to the total weight of the adsorbent.

[0055] In another aspect of the invention, the zeolitic adsorbent may have a potassium content, expressed as potassium oxide, KO, of less than 25% by weight, preferably between 0 and 20% by weight, more preferably between 0 and 15% by weight inclusive, based on the total weight of the adsorbent.

[0056] In another embodiment of the invention, the total content of alkali or alkaline earth ions other than barium and potassium, expressed as oxides of alkali or alkaline earth ions other than barium oxide BaO and potassium oxide KO, relative to the total weight of the adsorbent, is between 0 and 5% by weight, inclusive.

[0057] Preferably, the zeolitic adsorbent of the present invention is an adsorbent comprising FAU zeolite, commonly referred to as zeolite type X. By "Zeolite X" is meant a zeolite having an Si / Al atomic ratio of 1.00 to 1.50 inclusive, preferably 1.00 to 1.40 inclusive.

[0058] Within zeolite X, it is generally accepted that two subgroups are recognized today, called zeolite LSX and zeolite MSX: zeolite LSX has an Si / Al atomic ratio of about 1, i.e., 1.00±0.05, and MSX has an Si / Al atomic ratio of about 1.05 to about 1.15 (both exclusive).

[0059] In one preferred embodiment of the invention, zeolite X has an Si / Al atomic ratio of 1.15 to about 1.50, inclusive. In another preferred embodiment, zeolite X is an LSX type zeolite having an Si / Al atomic ratio of about 1, i.e., 1.0±0.05. It is also contemplated that the adsorbent may comprise a mixture of two or more zeolite X types as just defined.

[0060] In one preferred embodiment, the at least one FAU zeolite included in the zeolite adsorbent aggregate of the present invention has a Si / Al atomic ratio of from 1.00 to 1.50 (inclusive), preferably from 1.05 to 1.40, and more preferably from 1.10 to 1.40. Preferably, the at least one FAU zeolite is zeolite X.

[0061] In another preferred embodiment, the zeolite adsorbent aggregates of the present invention have no zeolite structures other than the FAU structure, preferably no zeolite structures other than the faujasite X structure, detected by X-ray diffraction (known to those skilled in the art by the abbreviation XRD).

[0062] In a further preferred embodiment, the weight fraction of FAU zeolite, preferably zeolite X, is greater than or equal to 80% relative to the total weight of the adsorbent of the invention, the remainder up to 100% preferably being made up of non-zeolitic phases.

[0063] The zeolite adsorbent aggregates of the present invention can contain a non-zeolitic phase (NZP), i.e., a non-crystalline phase that is essentially inactive to adsorption. The crystalline content (weight fraction of zeolite) of the adsorbents of the present invention can be determined by X-ray diffraction analysis, known to those skilled in the art by the abbreviation XRD.

[0064] The zeolite adsorbent aggregates of the present invention are preferably composed in the form of aggregates, i.e. composed of crystalline components (or crystals) of at least one FAU zeolite as defined above, said crystalline components (or more simply "crystals") being number averageThey have a diameter of less than 1200 nm, preferably between 100 nm and 1200 nm, more preferably between 400 nm and 1200 nm, even more preferably between 500 nm and 1200 nm, even more preferably between 550 nm and 1200 nm, and most advantageously between 600 nm and 1200 nm inclusive.

[0065] Aspects The zeolite adsorbent aggregates of the present invention can be produced by employing operating modes already known to those skilled in the art, and by selecting and adjusting synthesis parameters to obtain aggregates with the desired particle porosity and standard deviation σ values, for example as described in the previously cited documents WO 2014 / 090771, WO 2018 / 002174, US 2009 / 0326308.

[0066] The method for synthesizing the zeolite adsorbent aggregates of the present invention may, for example, comprise at least the following steps: a) agglomerating crystals of at least one zeolite of the FAU-X type with a binder comprising at least 80% clay or zeolitizable clay, optionally with up to 5% additives, and with water in an amount sufficient to form an aggregate material; drying the aggregates at a temperature between 50°C and 150°C; calcining the dried aggregates under an oxidizing and / or inert purge gas, in particular oxygen, nitrogen, air, dry and / or decarbonated air, optionally with dry and / or decarbonated oxygen-depleted air, at a temperature above 150°C, typically between 180°C and 800°C, preferably between 200°C and 650°C; b) contacting the agglomerates obtained in step a) with an alkaline base solution to zeolitize all or a portion of the binder; c) cation-exchanging the aggregates of step a) and / or step b) by contacting them with barium ions and / or potassium ions; d) optionally further cation-exchanging the aggregates of step c) by contacting them with a solution of potassium ions; e) washing and drying the agglomerates obtained in step c) or d) at a temperature of 50°C to 150°C; and f) Activation by heating, generally at a temperature of from 100°C to 400°C, preferably from 200°C to 300°C, followed by recovery of the zeolitic agglomerated adsorbent.

[0067] The zeolite crystals that can be used in the synthesis step a) above can be advantageously synthesized according to known procedures available in the scientific or patent literature and on the Internet. In particular, the zeolite crystals can be prepared as described in documents CN1191118C or WO2014 / 090771, or US7812208B2, US2009 / 326308 and US2007 / 224113.

[0068] The parameters that allow control over the standard deviation σ in the zeolite adsorbent aggregates of the present invention relate, for example, to the type of crystals used in step a), in particular their size and standard deviation, but also to the zeolitization conditions of the agglomerated binder, such as temperature, time, pH of the alkaline zeolitization solution, as well as duration, stirring mode, shear rate, pressure, etc.

[0069] More specifically, "the type of crystals used in step a)" refers in particular to the standard deviation of the crystals, which can be controlled by adjusting the synthesis parameters, in particular the synthesis temperature, stirring speed, and shear rate, as shown, for example, in documents WO2009 / 081022 or US2009 / 326308.

[0070] The synthesis parameters that allow for control of the porosity of the zeolite adsorbent aggregates of the present invention are also known to those skilled in the art. Generally, these parameters include, but are not limited to, binder percentage, type of agglomeration (by extrusion, spraying, granulation, etc.), humidity level, binder type, zeolitization conditions (temperature, time, pH of the alkaline zeolitization solution, duration, stirring mode, shear rate, pressure, etc.).

[0071] In one preferred embodiment, the synthesis of the zeolite adsorbent aggregates of the present invention does not involve the addition of pore-forming agents, although the presence of pore-forming agents would likely lead to a deterioration, particularly in crystallinity.

[0072] The crystalline component can also be prepared by seeding the synthesis and / or adjusting the synthesis operating conditions, such as the SiO2 / Al2O3 ratio, the sodium content and the alkalinity of the synthesis mixture.

[0073] The synthesis of FAU-type zeolites is generally carried out in a sodium medium (Na + The crystalline component of the FAU zeolite thus obtained contains almost exclusively sodium cations. However, it would be within the scope of the present invention to use a crystalline component that has undergone one or more cation exchanges during synthesis in the sodium form.

[0074] The size of the FAU zeolite crystals used in step a) and the size of the crystalline component of FAU zeolite in the aggregates of the present invention are measured by scanning electron microscopy (SEM). As indicated above, the average diameter of the crystals is generally less than 1200 nm, preferably between 100 nm and 1200 nm, more preferably between 400 nm and 1200 nm, more preferably between 500 nm and 1200 nm, even more preferably between 550 nm and 1200 nm, and most preferably between 600 nm and 1200 nm, inclusive.

[0075] This SEM observation also allows the identification of the presence of non-zeolitic phases in the aggregates, such as non-zeolitic phases containing residual binder (not converted in the zeolitization step) or other amorphous phases.

[0076] In this application, the term number average The terms "diameter" or "size" are used specifically with respect to crystalline zeolite components and zeolitic adsorbents. Methods for measuring these dimensions are explained later in the specification.

[0077] Agglomeration and shaping (step a) can be carried out using techniques known to those skilled in the art, such as extrusion, densification, agglomeration on a plate granulator, a drum granulator, spraying and others.

[0078] The proportions of agglomerating binder (see definition below) and zeolite used are typically those of the prior art, ie, 5-20 parts by weight of binder per 95-80 parts by weight of zeolite.

[0079] The agglomerates derived from step a), whether in the form of beads, extrudates or other, are generally number average The diameter, or length (longest dimension if not spherical) is between 100 μm and 1000 μm, preferably between 100 μm and 600 μm, more preferably between 200 μm and 550 μm inclusive.

[0080] After step a), the finest agglomerates can be removed by cycloning and / or screening, and / or oversized agglomerates can be removed by screening or crushing, for example in the case of extrudates.

[0081] The flocculating binder used in step a) comprises, or preferably consists of, a clay or clay mixture preferably selected from kaolin, kaolinite, nacrite, dickite, halloysite, attapulgite, sepiolite (sepiolite), montmorillonite, bentonite, illite and metakaolin, and mixtures of two or more thereof in any proportion.

[0082] For the zeolitization step, the agglomerating binder used in step a) comprises at least 80% by weight, preferably at least 90% by weight, more preferably at least 95% by weight, and more particularly at least 96% by weight of at least one zeolitizable clay, and may also contain other mineral binders such as bentonite, attapulgite, and others. Zeolitizable clay refers to a clay or clay mixture that can be converted into a zeolite material, most often by the action of an alkaline base solution. The zeolitizable clay generally belongs to the kaolin family (e.g., kaolinite, nacrite, dickite, halloysite) and / or metakaolin.

[0083] Among the additives optionally used in step a) may be any type of silica source known to those skilled in the art of zeolite synthesis, such as colloidal silica, diatoms, perlite, fly ash, sand, or any other form of solid silica.

[0084] In step a), in addition to the crystalline components of the FAU zeolite and the binder, other additives can also be used, such as additives intended to facilitate agglomeration or improve hardening, and other additives known to those skilled in the art.

[0085] In particular, when the agglomerating binder contains one or more zeolitizable clays, calcination allows the conversion of the zeolitizable clays, typically kaolin, to metakaolin, which can then be converted to zeolites in a zeolitization step (step b)), the principle of which is shown in "Zeolite Molecular Sieves", D.W. Breck, John Wiley and Sons, New York, 1973, pp. 314-315.

[0086] Zeolitization of the agglomerated binder can be carried out using any method currently known to those skilled in the art, and can be carried out, for example, by immersing the product derived from step a) in a generally aqueous alkaline base solution, such as an aqueous solution of sodium hydroxide and / or potassium hydroxide.

[0087] As a general rule, the concentration of the alkaline zeolitization solution is preferably between 0.5 M and 5 M. Zeolitization is preferably carried out under heat at temperatures above ambient temperature, typically in the range of 80° C. to 100° C. The duration of the zeolitization step is generally between a few tens of minutes and several hours, preferably between about 1 and 8 hours.

[0088] Preferably, and in order to ensure sufficient zeolitization of the binder without degrading the crystallinity of the zeolite crystals present, the adsorbent is contacted with cold sodium hydroxide and a gradual temperature increase to a temperature of 80°C to 100°C is applied.

[0089] Similarly, the concentration of sodium hydroxide can be maintained at the same concentration or gradually increased to maintain maximum crystallinity of the initial crystals and ensure maximum conversion of the zeolitizable binder.

[0090] The cation exchange steps c) and d) are carried out according to conventional methods known to those skilled in the art, and very often involve contacting the agglomerate derived from step a) with a barium and / or potassium salt, such as barium chloride (BaCl) and / or potassium chloride (KCl), in aqueous solution at a temperature between ambient and 100°C, preferably between 80°C and 100°C, to rapidly obtain a high barium content, expressed as barium oxide, i.e., preferably greater than 10 wt. %, more preferably greater than 15 wt. %, even more preferably greater than 20 wt. %, even more preferably greater than 23 wt. %, or even greater than 33 wt. %, based on the total weight of the adsorbent.

[0091] Advantageously, the barium content, expressed as barium oxide, is between 23% and 42% by weight, typically between 30% and 40% by weight (inclusive), relative to the total weight of the adsorbent. It is desirable to operate with a large excess of barium ions relative to the zeolite cations desired to be exchanged, typically an excess ranging from 10 to 12, advantageously proceeding by continuous exchange.

[0092] The optional exchange with potassium (step d) can be carried out before and / or after the exchange with barium (step c). As indicated above, it is also possible in step a) to agglomerate crystalline components of the FAU zeolite that already contain barium or potassium ions or barium and potassium (it is also possible to pre-exchange the cations, typically sodium cations, contained in the starting zeolite of FAU type with barium or potassium ions or barium and potassium before step a), and to omit (or not omit) steps c) and / or d).

[0093] The cation exchange step a) is generally and preferably followed by washing with water, and then drying the agglomerates thus obtained.

[0094] Activation after drying is carried out in a conventional manner using methods known to those skilled in the art, for example at temperatures generally between 100°C and 400°C, preferably between 200°C and 300°C, for a time, typically between 1 and 6 hours, as a function of the desired water content and losses due to combustion.

[0095] Characterization Technology Zeolite crystal particle size measurement: The components (i.e., crystals) of the FAU-type zeolite used in step a) number average The diameter and the content of zeolite X in the aggregates (i.e., crystals) number average Diameter estimation is performed by observation under a scanning electron microscope (SEM).

[0096] To estimate the size of the zeolite particles (i.e., crystallites) of a sample, a set of images is taken at a magnification of at least 5000. The diameter is then measured for at least 200 particles using dedicated software, such as Smile View software by LoGraMi. The accuracy is within 3%. The histogram formed from the diameter measurements simultaneously determines the standard deviation σ of the distribution. Chemical analysis of zeolite adsorbent aggregates - Si / Al ratio and exchange kinetics:

[0097] The elemental chemical analysis of the final product obtained after steps a) to f) described above can be carried out using various analytical techniques known to those skilled in the art, among which we can mention X-ray fluorescence chemical analysis with a wavelength dispersive X-ray fluorescence spectrometer (WDXRF), for example Tiger S8 by Bruker, as described in standard NF EN ISO 12677:2011.

[0098] X-ray fluorescence is a non-destructive spectroscopic technique that uses the photoluminescence of atoms in the X-ray region to determine the elemental composition of a sample. Excitation of the atoms, typically by an X-ray beam or electron bombardment, results in the emission of specific radiation after the atoms return to their ground state. X-ray fluorescence spectra have the advantage of being very nearly independent of the chemical bonding of the elements, which allows for accurate determinations of both quantity and quality. After calibration, the uncertainty in the measurements obtained for each oxide is typically less than 0.4% by weight.

[0099] These elemental chemical analyses allow the verification of both the Si / Al atomic ratio of the zeolite used for the agglomerates and of the Si / Al atomic ratio of the final product obtained after steps a) to f) described above, as well as the verification of the quality of the ion exchange described in step c) and optional step d). In the present description, the measurement uncertainty of the Si / Al atomic ratio is ±5%.

[0100] The quality of the ion exchange is related to the number of moles of sodium oxide (Na2O) remaining in the zeolite aggregates after ion exchange. More specifically, the percentage of exchange with barium ions is estimated by evaluating the ratio of the number of moles of barium oxide (BaO) to the number of moles of the group (BaO + Na2O). Similarly, the percentage of exchange with barium and / or potassium ions is estimated by evaluating the ratio of the number of moles of the sum of barium oxide and potassium oxide (BaO + KO2O) to the number of moles of the sum of (BaO + KO2O + Na2O). Note that the contents of the different oxides are given in weight percentages relative to the total weight of the anhydrous zeolite adsorbent.

[0101] Zeolite adsorbent particle size measurement: of the zeolite adsorbent obtained after the agglomeration and formation step a) number average The diameter determination is carried out by analysis of the particle size distribution in the aggregate sample by using a conveyor to pass the sample in front of a camera and imaging the sample according to standard ISO 13322-2:2006.

[0102] Next number average The diameter is calculated from the particle size distribution by applying the standard ISO 9276-2:2001. number average The terms "diameter" or "size" are used for zeolite aggregates. The accuracy is in the region of 0.01 mm for the size range of the aggregates of the present invention.

[0103] Mechanical strength of zeolite adsorbent: The crush strength of a bed of zeolite adsorbent as described in this invention is characterized by Shell Method Series SMS 1471-74 "Determination of the bulk crush strength of catalysts. Compression-sieve method" in conjunction with the "BCS Tester" device marketed by Vinci Technologies. This method, originally intended for the characterization of catalysts between 3 mm and 6 mm, is based on the use of a 425 μm screen, which allows the separation of fines during crushing. The use of a 425 μm screen is still suitable for particles with a diameter greater than 1.6 mm, but must be adapted to the particle size of the agglomerates whose characterization is sought.

[0104] The aggregates of the present invention are generally in the form of beads or extrudates and are generally number average The diameter or length, i.e., the longest dimension for non-spherical agglomerates, is from 0.2 mm to 2 mm, and especially from 0.2 mm to 0.8 mm, preferably from 0.4 mm to 0.65 mm, inclusive. Thus, a 100 μm screen is used instead of the 425 μm screen mentioned in Shell standard SMS 1471-74.

[0105] The measurement protocol is as follows: 20 cm of agglomerated adsorbent previously screened with a fitted screen (100 μm) and previously oven-dried at 250°C (instead of 300°C as stated in Shell Standard SMS1471-74) for at least 2 hours is applied. 3 The sample is placed in a metal cylinder of known internal cross section. Increasing force is applied to the sample gradually in increasing steps by a piston, which is fitted with a 5 cm 2 cylinder of stainless steel beads to better distribute the force on the adsorbent aggregate. 3 A force is applied to the sample through the bed (2 mm diameter beads are used for spherical particles with a diameter strictly less than 1.6 mm). The fines obtained at increasing stages of applied pressure are separated by sieving (fitted with a 100 μm screen) and weighed.

[0106] The in-bed crush strength is measured by the pressure in megapascals (MPa) where the amount of accumulated fines passing through the screen amounts to 0.5% by weight of the sample. This value is obtained by plotting the resulting mass of fines as a function of the force applied to the adsorbent bed and interpolating to 0.5% by weight of accumulated fines. The in-bed crush strength is typically between several hundred kPa and several tens of MPa, generally between 0.3 MPa and 3.2 MPa. Accuracy is conventionally within less than 0.1 MPa.

[0107] Non-zeolitic phases of zeolitic adsorbents. The percent of non-zeolitic phase NZP after zeolitization, e.g., residual non-zeolitic binder or other amorphous phase, is calculated by the following formula:

[0108] (Number 1) NZP=100-Σ(ZP) Here, ZP represents the total amount of zeolitic fractions within the meaning of the present invention.

[0109] The percentage of zeolite X fraction (percent crystallinity) is determined by X-ray diffraction analysis, known to those skilled in the art by the abbreviation XYD. This analysis is carried out on a Bruker instrument, and the percentage of zeolite X fraction is evaluated using TOPAS software by Bruker.

[0110] Micropore (micropore) volume: The crystallinity of the aggregates is also assessed by measuring their micropore volume in comparison with an appropriate reference (a 100% crystalline zeolite under the same cation treatment conditions, or a theoretical zeolite), which is determined from a gas adsorption isotherm, e.g., nitrogen, measured at its liquefaction temperature.

[0111] Before adsorption, the zeolite adsorbent was heated at 300 to 450°C for 9 to 16 hours under reduced pressure (P < 6.7 × 10 -4 The nitrogen adsorption isotherm is then measured at 77 K on an ASAP2020M type apparatus from Micromeritics at at least 35 measuring points at relative pressures with a P / P ratio between 0.002 and 1.

[0112] Total macropore and mesopore volume and particle porosity: Volume of macropores Vma and mesopores Vme, particle density Dp and porosity ε of macroporous and mesoporous types p is measured by mercury intrusion porosimetry. A mercury porosimeter of the Autopore® 9500 model by Micromeritics is used to analyze the distribution of pore volume in macropores and mesopores.

[0113] The experimental method, described in the operating manual of the said equipment, with reference to the standard ASTM D4284-83, involves placing a sample of adsorbent (zeolite aggregates in the form of aggregates to be measured) of known losses on combustion and previously weighed, in a porosimeter cell, and after previous degassing (evacuation pressure 30 μm mercury for at least 10 minutes), filling the cell with mercury at a given pressure (0.0036 MPa), then gradually increasing the pressure level up to 400 MPa in order to gradually force the mercury into the porous network of the sample, using at least 15 atmosphere levels up to 0.2 MPa, then applying increments of 0.1 MPa up to 1 MPa, then applying increments of 0.5 MPa up to 10 MPa, then applying increments of 2 MPa up to 30 MPa, then applying increments of 5 MPa up to 180 MPa and finally applying increments of 10 MPa up to 400 MPa.

[0114] The characteristic dimensions of the applied pressure and pore penetration threshold (corresponding to the pore diameter of the device) are determined using the Laplace-Young equation and assuming a cylindrical pore opening, a contact angle between the mercury and the pore wall of 140°, and a mercury surface tension of 485 dynes / cm. The volume increase ΔVi of the inserted mercury at each pressure level Pi is recorded, and the accumulated volume of inserted mercury is subsequently plotted as a function of the applied pressure V(Pi) or the apparent diameter of the pores V(l). The value when and thereafter the mercury fills all intraparticle voids is set to 0.2 MPa, above which mercury is considered to enter the pores of the adsorbent. The particle volume Vp is then calculated by subtracting the accumulated volume of mercury at this pressure (0.2 MPa) from the volume of the porosimeter cell and dividing this difference by the mass of the equivalent anhydrous adsorbent, i.e., the mass of that material corrected for losses due to combustion. The particle density Dp is the reciprocal of the particle volume Vp, as defined previously.

[0115] The macropore volume Vma of the adsorbent is defined as the accumulated volume of mercury inserted at pressures between 0.2 MPa and 30 MPa, and corresponds to the volume accommodated in pores with an apparent diameter greater than 50 nm. The mesopore volume Vme of the adsorbent is defined as the accumulated volume of mercury inserted at pressures between 30 MPa and 400 MPa. Since the method for measuring pore volume by mercury intrusion does not provide access to the micropore volume, the total pore volume Vtot as measured by mercury intrusion corresponds to the sum of the macropore volume Vma and the mesopore volume Vme.

[0116] In this specification, cm 3 g -1 The macropore volume Vma and mesopore volume Vme of the zeolite adsorbent, expressed as V, and their sum (total pore volume V), are therefore measured by mercury intrusion porosimetry and relate to the mass of the sample in anhydrous equivalent form, i.e., the mass of the adsorbent corrected for losses due to combustion. The particle density Dp is expressed in gcm -3 and refers to the mass of the sample in anhydrous equivalent form.

[0117] Particle porosity ε of macroporous and mesoporous types p is the product of the particle density Dp multiplied by the sum of the macropore and mesopore volumes, Vma and Vme:

[0118] (Number 2) ε p =Dp×(Vma+Vme)

[0119] Combustion losses of zeolite adsorbents. The losses due to combustion are measured in an oxidizing atmosphere by calcining the samples in air at a temperature of 900°C ± 25°C, according to the operating mode described in standard NF EN 196-2 (April 2006). The standard deviation σ of the measurements is less than 0.1%. [Example]

[0120] Example 1: Preparation of aggregates Four adsorbents were prepared as described below from faujasite zeolite powder of type X (inventive aggregates 1, 3, and 4 and comparative aggregate 2), with an average crystal size of 0.6 μm, with standard deviations of 0.25 μm, 0.30 μm, 0.35 μm, and 0.50 μm, respectively.

[0121] Preparation of Aggregate 1 (of the Present Invention) A homogeneous mixture is prepared, and 800 g of zeolite crystals with a standard deviation of 0.25 μm are agglomerated with 160 g of kaolin (expressed in calcined equivalent) and 60 g of colloidal silica sold under the trade name Klebosol® 30N50 (containing 30% by weight of SiO and 0.5% by weight of NaO) using a quantity of water that allows the mixture to be extruded. The extrudates are dried and calcined at 550° C. for 2 hours under a nitrogen flow (calcination of the clay), and finally crushed to recover agglomerates with a number average diameter of 0.5 mm.

[0122] The aggregates (20 g) obtained as above are placed in a double-jacketed glass reactor, the temperature of which is controlled at 85°C ± 1°C, to which 250 mL of a 1M aqueous solution of sodium hydroxide is added, and the reaction medium is left under stirring for 5 hours.

[0123] The aggregates are then washed with water in three successive washes and the reactor is drained. The effectiveness of the water washes is checked by measuring the final pH of the wash water, which should be between 10.0 and 10.5.

[0124] The agglomerates are exchanged with a 0.5 M barium chloride solution at 95°C in four steps. In each step, the ratio of solution volume to solid mass is 29 mL / g, and the exchange lasts for 4 hours each. Between each exchange, the solid is washed several times to remove excess salt. The agglomerates are then dried at 80°C for 2 hours and finally activated at 250°C for 2 hours under a nitrogen stream.

[0125] Preparation of Aggregate 2 (for comparison) A homogeneous mixture is prepared, and 800 g of zeolite crystals with a standard deviation of 0.50 μm are agglomerated with 145 g of kaolin (expressed in calcined equivalent) and 55 g of colloidal silica sold under the trade name Klebosol® 30N50 (containing 30% by weight of SiO and 0.5% by weight of NaO) using a quantity of water that allows the mixture to be extruded. The extrudates are dried and calcined at 550° C. for 2 hours under a nitrogen flow (calcination of the clay), and finally crushed to recover agglomerates with a number average diameter of 0.5 mm.

[0126] The aggregates (20 g) obtained as above are placed in a double-jacketed glass reactor, the temperature of which is controlled at 95°C ± 1°C, to which 250 mL of a 1.25 M aqueous solution of sodium hydroxide is added, and the reaction medium is left under stirring for 4 hours.

[0127] The aggregates are then washed with water in three successive washes and the reactor is drained. The effectiveness of the water washes is checked by measuring the final pH of the wash water, which should be between 10.0 and 10.5.

[0128] The agglomerates are exchanged with a 0.5 M barium chloride solution at 95°C in four steps. In each step, the ratio of solution volume to solid mass is 20 mL / g, and the exchange lasts for 4 hours each. Between each exchange, the solid is washed several times to remove excess salt. The agglomerates are then dried at 80°C for 2 hours and finally activated at 250°C for 2 hours under a nitrogen stream.

[0129] Preparation of Aggregate 3 (of the Present Invention) A homogeneous mixture is prepared and 800 g of zeolite crystals with a standard deviation of 0.30 μm are agglomerated with 160 g of kaolin (expressed in calcined equivalent) and 60 g of colloidal silica sold under the trade name Klebosol® 30N50 (containing 30% by weight of SiO2 and 0.5% by weight of Na2O) with a quantity of water that allows the mixture to be extruded. The extrudates are dried and calcined at 550° C. for 2 hours under a nitrogen flow (calcination of the clay) and finally crushed. number average Aggregates with a diameter of 0.5 mm are collected.

[0130] The aggregates (20 g) obtained as above are placed in a double-jacketed glass reactor, the temperature of which is controlled at 90°C ± 1°C, to which 250 mL of a 0.9 M aqueous solution of sodium hydroxide is added, and the reaction medium is left under stirring for 6 hours.

[0131] The aggregates are then washed with water in three successive washes and the reactor is drained. The effectiveness of the water washes is checked by measuring the final pH of the wash water, which should be between 10.0 and 10.5.

[0132] The agglomerates are exchanged with a 0.5 M barium chloride solution at 95°C in four steps. In each step, the ratio of solution volume to solid mass is 20 mL / g, and the exchange lasts for 4 hours each. Between each exchange, the solid is washed several times to remove excess salt. The agglomerates are then dried at 80°C for 2 hours and finally activated at 250°C for 2 hours under a nitrogen stream.

[0133] Preparation of Aggregate 4 (of the Invention) A homogeneous mixture is prepared and 800 g of zeolite crystals with a standard deviation of 0.35 μm are agglomerated with 150 g of kaolin (expressed in calcined equivalent) and 58 g of colloidal silica sold under the trade name Klebosol® 30N50 (containing 30% by weight of SiO2 and 0.5% by weight of Na2O) with a quantity of water that allows the mixture to be extruded. The extrudates are dried and calcined at 550° C. for 2 hours under a nitrogen flow (calcination of the clay) and finally crushed. number average Aggregates with a diameter of 0.5 mm are collected.

[0134] The aggregates (20 g) obtained as above are placed in a double-jacketed glass reactor, the temperature of which is controlled at 90°C ± 1°C, to which 250 mL of a 1.15 M aqueous solution of sodium hydroxide is added, and the reaction medium is left under stirring for 5 hours.

[0135] The aggregates are then washed with water in three successive washes and the reactor is drained. The effectiveness of the water washes is checked by measuring the final pH of the wash water, which should be between 10.0 and 10.5.

[0136] The agglomerates are exchanged with a 0.5 M barium chloride solution at 95°C in four steps. In each step, the ratio of solution volume to solid mass is 20 mL / g, and the exchange lasts for 4 hours each. Between each exchange, the solid is washed several times to remove excess salt. The agglomerates are then dried at 80°C for 2 hours and finally activated at 250°C for 2 hours under a nitrogen stream.

[0137] Properties of aggregates 1-4 The mechanical strength (REL) of the aggregates was characterized using the characterization technique described above, and a value of 3.2 MPa was obtained for aggregate 1, 3.1 MPa for aggregate 2, 2.9 MPa for aggregate 3, and 3.1 MPa for aggregate 4.

[0138] Particle porosity ε of the crystals in the final aggregate measured for aggregates 1 to 4 p The values ​​of and standard deviation σ are shown in Table 1 below.

[0139] Aggregate 1 containing BaX crystals exhibits an average crystal size measured on the final aggregate of 0.79 μm, Aggregate 2 containing BaX crystals exhibits an average crystal size measured on the final aggregate of 0.76 μm, Aggregate 3 containing BaX crystals exhibits an average crystal size measured on the final aggregate of 0.77 μm, and Aggregate 4 containing BaX crystals exhibits an average crystal size measured on the final aggregate of 0.76 μm.

[0140] The barium exchange rate of aggregates 1-4 is 99.0% as calculated from elemental analysis of barium oxide and sodium oxide by X-ray fluorescence as described in the characterization techniques.

[0141] The BaO content in aggregates 1 to 4 is 36.2 wt %.

[0142] The loss due to combustion, measured as described above, is 5.2%±0.1%.

[0143] Example 2: Implementation in the separation process Use of Aggregates 1, 3 and 4 Aggregates 1, 3 and 4 were used for the separation of para-xylene in a simulated moving bed.

[0144] The apparatus used, operated as a simulated moving bed, consisted of 24 beds, 1.1 m long, with feed inlets, desorbent inlets, extract outlets, and raffinate outlets. The beds were divided into four chromatographic zones with a 5 / 9 / 7 / 3 distribution.

[0145] The feed consisted of 50% para-xylene, 14.5% ortho-xylene, 30.6% meta-xylene, and 4.9% ethylbenzene. The desorbent was para-diethylbenzene. The temperature was 175°C and the pressure was 15 bar. The water content was 95 ppm (by weight).

[0146] The resulting productivity is shown in Table 1 below. The surface linear velocity in zone 3 was 1.63 cms -1 It was.

[0147] Use of Aggregate 2 Aggregate 2 was used for the separation of para-xylene in a simulated moving bed.

[0148] The apparatus used, operated as a simulated moving bed, consisted of 24 beds, 1.1 m long, with feed inlets, desorbent inlets, extract outlets, and raffinate outlets. The beds were divided into four chromatographic zones with a 5 / 9 / 7 / 3 distribution.

[0149] The feed consisted of 50% para-xylene, 14.5% ortho-xylene, 30.6% meta-xylene, and 4.9% ethylbenzene. The desorbent was para-diethylbenzene. The temperature was 175°C and the pressure was 15 bar. The water content was 95 ppm (by weight).

[0150] Productivity was 186 kg of para-xylene m -3 h -1 The surface linear velocity in zone 3 was 1.63 cm s -1 It was.

[0151] The productivity results for the four flocculated adsorbents are shown in Table 1 below.

[0152] [Table 1]

[0153] The aggregates of the present invention are clearly shown to significantly increase productivity in the para-xylene production process.

Claims

1. An agglomerated zeolite adsorbent comprising at least one faujasite zeolite (FAU-X) having an Si / Al atomic ratio between 1.00 and 1.50 (inclusive), and barium and optionally potassium, characterized in that first, the particle porosity of the adsorbent is between 25% and 45% (inclusive), and second, the standard deviation σ of the crystal size distribution in the adsorbent is between 0.05 μm and 0.30 μm (inclusive), and the adsorbent comprises zeolite crystals having a number average diameter of 100 nm to 1200 nm (inclusive).

2. 10. The agglomerated zeolite adsorbent of claim 1, wherein the adsorbent comprises zeolite crystals having a number average diameter of 400 nm to 1200 nm, inclusive.

3. 3. Agglomerated zeolite adsorbent according to claim 1 or 2, characterized in that the adsorbent is in the form of beads having an average diameter of 100 μm to 1000 μm inclusive.

4. 4. The agglomerated zeolitic adsorbent according to any one of claims 1 to 3, wherein said at least one faujasite zeolite (FAU-X) has an Si / Al atomic ratio of 1.05 to 1.50 inclusive.

5. 5. The agglomerated zeolite adsorbent according to any one of claims 1 to 4, wherein the barium content is between 23% and 42% by weight, inclusive, based on the total weight of the adsorbent.

6. Potassium oxide (K ２ 6. The agglomerated zeolite adsorbent according to any one of claims 1 to 5, wherein the content of 0) is between 0 and 20 wt. % inclusive.

7. 7. The agglomerated zeolite adsorbent according to claim 1, wherein no zeolite structure other than the faujasite structure is detected by X-ray diffraction.

8. 8. The agglomerated zeolite adsorbent according to any one of claims 1 to 7, wherein the weight fraction of FAU zeolite is 80% or more based on the total weight of the adsorbent.

9. Use of the agglomerated zeolite adsorbent according to any one of claims 1 to 8 in the following method: - Separation of the C8 aromatic isomer fraction; - separation of isomers of substituted toluenes; - Separation of cresols; - Separation of polyhydric alcohols.

10. 10. Use according to claim 9 for separating para-xylene from the aromatic isomer fraction having 8 carbon atoms.

11. A method for separating para-xylene from an aromatic isomer fraction having 8 carbon atoms, comprising using the agglomerated zeolite adsorbent according to any one of claims 1 to 8 as a para-xylene adsorbent in the liquid or gas phase.

12. 12. A process for separating para-xylene from the aromatic isomer fraction having 8 carbon atoms according to claim 11, carried out by adsorption of para-xylene in the liquid phase in the presence of a desorbent.

13. 13. The method according to claim 11 or 12, which is a simulated moving bed type.

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