Process for treating a catalyst comprising a zeolite

Abstract

The present invention relates to a method for treating a catalyst comprising at least one aluminosilicate zeolite of the ZSM-5 family and a binder comprising silicon oxide, such that said treatment comprises steam treatment of the catalyst, said steam treatment being carried out - on the catalyst in the form of a catalytic bed of catalyst particles, - said bed being arranged in a catalytic hydrocarbon conversion reactor, - with a steam treatment gas flow passing through said bed and comprising water vapor, - at a temperature of at least 150°C, - and a pressure of at most 3.106 Pa.

Description

Title of the invention: Method for treating a catalyst comprising a zeolite Technical field

[0001] The present invention relates to a new method for treating a material comprising a ZSM-5 type zeolite. This material advantageously finds applications as a catalyst, as a catalyst support, but also as an adsorbent or separation agent. The invention will focus more particularly on an application of this material as a catalyst. Prior art

[0002] Crystallized microporous materials, such as zeolites, are solids widely used in the petroleum industry as catalysts, particularly for heterogeneous catalysis of isomerization, cracking or alkylation of hydrocarbons, or for the conversion of olefins, ethylene to propylene for example. But this type of material can also be used as a catalyst support: by adding an active element, such as copper for example, an oxidation catalyst is obtained, particularly of ethanol to acetaldehyde, copper being able to be combined with other elements such as chromium. This type of material can also be used to convert alcohols into gasoline.

[0003] For high-temperature catalytic oligomerization-cracking reactions in the absence of hydrogen, ZSM-5 zeolite (MFI structural type) is one of the most studied active phases because it has multiple advantages. The confinement of reactants and products in the medium-pore microporous network of ZSM-5 (openings with 10 tetrahedral atoms) is conducive to the desired reactions while ensuring the diffusion of products to the outside of the pores. The Si / Al ratio which dictates the quantity of acid sites can be modulated by the zeolite synthesis protocol over a wide range (from 15 to 400 at. / at.). This medium-pore-opening zeolite with a three-dimensional porous network is much less sensitive to coking than more open zeolites (e.g., Y and Beta zeolites of structural type FAU and BEA respectively) or one-dimensional closed zeolites (e.g., ZSM-22 of structural type TON).Zeolite synthesis also presents a moderate cost acceptable for industrial application. The refining and petrochemical industry is always looking for zeolite catalysts that have improved properties, particularly with regard to the conversion of hydrocarbon species depending on the application (yield and / or selectivity of the catalyzed reactions), and / or with regard to their stability over time, their mechanical resistance, etc.

[0004] Patent US-4,663,492 discloses a catalyst based on ZSM-5 zeolite in the context of a process for converting methanol into gasoline, this catalyst being previously treated with steam at atmospheric pressure to increase its activity with respect to this conversion, this treatment being followed or preceded by calcination.

[0005] Also known from US patent No. 8,759,598 is a zeolite-based catalyst, in particular of the CHA zeolite type, in the context of a process for converting ethylene into propylene. This document recommends reducing the number of acid sites of the zeolite found specifically on the surface of the material. To do this, it proposes several methods, including surface silylation, steam treatment or treatment with a dicarboxylic acid.

[0006] Furthermore, patent EP-3 428 249 discloses a process for converting ethylene from a cut originating from the fractionation of an effluent from a catalytic cracking unit into propylene, aromatics and other products of interest: this conversion process is carried out in a conversion unit using a zeolite-based catalyst operating at a temperature of between 500 and 650°C and under a partial pressure of olefins of between 1 and 2 bars. This catalyst comprises, for example, a ZSM-5 zeolite in a silica-type matrix.

[0007] The invention then aims to improve the performance of catalysts comprising a zeolite, in particular of the ZSM-5 type, by targeting more particularly the conversion of ethylene or ethanol into propylene, other short olefins and other products of interest, and this without calling into question or without overly complicating their method of preparation.

[0008] In the context of the present invention, the olefins produced can be used for all applications using short olefins: monomers or polymers (Polyethylene, Polypropylene, Polyesters) for plastics after separation of each type of compound, or, alone or in a mixture, feedstocks for processes capable of producing fuel (aviation fuel, known as "jet", gasoline, distillate).

[0009] The invention relates in particular to a process which accompanies the fluidized bed catalytic cracking process (commonly called FCC). At the outlet of the reaction / regeneration assembly, there is a fractionation column, which makes it possible to separate the heavy fractions, heavy naphtha, and the light fractions: gas, LPG and light gasoline which are found at the top of the column. These light overhead fractions are then sent to a section making it possible to recover the maximum amount of LPG and gasoline, and to possibly purify the gas before sending it to the fuel gas. This gas, called "fuel gas", contains a significant quantity of ethylene, which is often burned with the fuel gas. This ethylene can be converted into propylene and other valuable products such as short olefins and gasoline. Summary of the invention

[0010] The invention firstly relates to a method for treating a catalyst comprising at least one aluminosilicate zeolite of the ZSM-5 family and a binder comprising silicon oxide, such that said treatment comprises steam treatment of the catalyst, said steam treatment being carried out:

[0011] - on the catalyst in the form of a catalytic bed of catalyst particles, - said bed being arranged in a catalytic hydrocarbon conversion reactor, - with a flow of steam treatment gas passing through said bed and comprising water vapor, - at a temperature of at least 150°C, in particular at least 180°C, for example around 200°C, or at higher temperatures, up to 400°C and above 400°C, - and a pressure of at most 3.106 Pa, in particular at most 106 Pa.

[0012] In the context of the present invention, the term "silica" or "silicon oxide" also means silicon oxide, possibly in hydrated form. This may in particular be the case when the steam treatment is carried out on the solid formed into particles, for example by kneading-extrusion in the case of extrudates, and just dried after shaping.

[0013] The catalyst “particles” can be in different forms depending on the chosen shaping: they can be grains, beads, extrudates, various and more or less regular shapes. The term “particles” in the context of the invention generically encompasses all possible forms conventionally known for this type of catalyst.

[0014] The term "bed" is understood in its conventional sense in the field of catalysts (catalytic bed): it is an arrangement in layer(s) of catalyst particles, supported by conventional mechanical means (metal grids, etc.) allowing the passage of a gaseous or liquid flow through its thickness. We are therefore considering here a bed of the fixed bed type, where the particles are not in motion, are not stirred in the reaction medium defined by the reactor concerned.

[0015] The temperature is to be understood here as the temperature reached by the catalyst particles, generally due to contact with the flow of vapor treatment gas having this temperature.

[0016] Pressure is to be understood here as the pressure which prevails inside the hydrocarbon conversion reactor.

[0017] It has thus been shown within the framework of this invention that, for this type of catalyst combining a ZSM-5 zeolite and a silicic type binder, steam treatment at high temperature and in the very reactor of the targeted catalytic conversion of hydrocarbon compounds gave very interesting results, even at moderate pressure or even at atmospheric pressure: the treated catalyst allows to achieve higher conversion rates and / or yields of propylene and aromatic compounds in the case of catalysis of the ethylene to propylene conversion reaction, as well as higher stability of the conversion and / or yields.

[0018] But, above all, the invention proposes to treat the catalyst in the form of a catalytic bed arranged in a hydrocarbon catalytic conversion reactor which will use the catalyst in question. This is then referred to as "in situ" steam treatment, insofar as the catalytic bed which is steam treated is already in the reactor in its functional position to carry out the catalysis by contacting it with a hydrocarbon feedstock flow and / or a flow intended to react with a feedstock flow, such as hydrogen for example: the bed is thus first crossed by the steam treatment gas flow, then by the hydrocarbon feedstock / reagent flow.This is a way of carrying out steam treatment which is very advantageous, since it limits handling and intermediate storage of catalyst, avoids the use of a dedicated steam treatment device, and because the hydrocarbon conversion reactor is generally already equipped with all the appropriate means for implementing the invention (gas injection and evacuation means, means for heating the enclosure / gas flows, and pressurization means, means for regulating these operating conditions, in particular using sensors fitted to the reactor, etc.).

[0019] According to a first embodiment, the pressure at which the vapor treatment is carried out is atmospheric pressure.

[0020] According to a second embodiment, the pressure at which the vapotreatment is carried out is higher than atmospheric pressure, but is preferably low. It is preferably between 2 bars and 30 bars, i.e. between 0.2.106 Pa and 3.106 Pa, or between 2 and 10 bars, i.e. 0.2.106 Pa and 106 Pa, or between 3 and 8 bars, i.e. between 0.3.106 Pa and 0.8.106 Pa.

[0021] According to one embodiment, the temperature at which the steam treatment is carried out is at least 450 or 500°C, in particular between 500 and 700°C, preferably between 550 and 650°C, for example in the vicinity of 600°C.

[0022] According to another embodiment, the temperature at which the steam treatment is carried out is lower, in particular between 150 and 250°C, for example between 180 and 200°C. In this embodiment, the pressure at which the steam treatment is carried out is advantageously greater than or equal to 10 bars, i.e. greater than or equal to 106 Pa.

[0023] Preferably, the duration of vapotreatment is at most 24 hours, in particular at most 10 hours, or at most 5 hours, preferably between 1 hour and 3 hours. It is therefore a duration which can be quite short, and therefore not too costly in terms of catalyst preparation time or in terms of immobilization of the catalytic conversion reactor.

[0024] Preferably, the flow rate of the vapor treatment gas stream at the inlet of the reactor is between 0.01 and 0.1 NL per hour and per gram of catalyst, in particular between 0.01 and 0.05 NL per hour and per gram of catalyst.

[0025] Advantageously, the vapor treatment gas flow may contain a mixture of gases comprising water vapor and at least one or more other gases, chosen from N2, CO2, Ar, He, CH4, air or any mixture thereof, preferably air or nitrogen.

[0026] Thus, the volume proportion of water vapor in the vapor treatment gas can be between 10 and 100%, in particular between 40 and 90%, preferably between 50 and 80%.

[0027] The water vapor content in the vapor treatment gas may be constant or may vary during at least part of the vapor treatment. Choosing a constant water content is the simplest solution. Changing it, in particular increasing it gradually or in stages, may also be beneficial.

[0028] Similarly, the pressure and temperature during vaping can be constant or vary, with progressive increases or by one or more temperature or pressure stages in particular.

[0029] According to a first variant, the binder comprises silicon oxide, preferably consists of silicon oxide. It can be introduced during the preparation of the catalyst at least partly in the form of colloidal silica and / or in the form of precipitated silica and / or silica gel, preferably both in the form of colloidal silica and in the form of precipitated silica, or both in the form of colloidal silica and in the form of silica gel. Such a binder is particularly inert with respect to the conversion reactions to be catalyzed, more so than alumina for example, which is advantageous, because it will increase the durability of the catalyst, and this without interfering with the reactions to be catalyzed: this avoids any disturbance, any risk of promoting a reaction leading to unwanted by-products.

[0030] Preferably, the catalyst comprises between 20 and 80% by weight of zeolite, in particular between 30 and 70% by weight of zeolite, or between 50 and 70% by weight of zeolite, and between 20 and 80% by weight of binder, for example between 30 and 70% by weight of binder, or between 30 and 50% by weight of binder.

[0031] For the mixing and shaping of the catalyst from zeolite (for example in powder form) and the binder or its precursor(s) (for example in powder form or in liquid form), at least one additive may be added, which may in particular have the function of helping to control the viscosity of the mixture before shaping (for example a viscosifying additive), particularly when this shaping is an extrusion of the mixture in pasty form. In the final catalyst, particularly when it has been heated / cooked / calcined, the additive disappears, particularly when it is made of organic material. It may be, for example, a derivative cellulose, especially methylcellulose.

[0032] The Si / Al atomic ratio of the zeolite contained in the catalyst is preferably between 12 and 200, in particular between 35 and 180, preferably between 35 and 150.

[0033] The catalyst may also comprise at least one doping element, for example belonging to the group consisting of sodium, potassium, magnesium, calcium, phosphorus, copper, silver, manganese, molybdenum. Preferably the doping element is phosphorus, optionally combined with one or more other elements. The content of doping element is preferably such that the atomic ratio of the element to the aluminum contained in the zeolite is less than or equal to 0.8. The doping element may be introduced by any type of preparation known to those skilled in the art, for example by dry impregnation, by excess impregnation, by chemical vapor deposition or any other type. Concerning the phosphorus element, it may for example be introduced using one or more precursors of the phosphoric acid or ammonium dihydrogen phosphate or hypophosphorous acid type.

[0034] According to a variant, the catalyst according to the invention comprises at least two ZSM-5 zeolites (which have been mixed, for example, in a preliminary mixing step for preparing the catalyst), among which at least two have different Si / Al atomic ratios, for example in a mass ratio of 10 / 90 to 90 / 10, in particular 20-80 to 80-20, for example between 40-60 and 60-40. Indeed, it appears that the catalytic properties are linked at least in part to the Al site content of the zeolite: combining two zeolites with different Si / Al ratios can make it possible to adjust the overall acidity of the material and thus more easily improve the catalytic properties of the catalyst and the compromise between activity and selectivity.

[0035] The shaping of the catalyst into particles can be carried out by any known method, such as, for example, kneading / extrusion, shaping by dripping (“oil-drop”), granulation, compaction, atomization.

[0036] The steam treatment of the catalyst can be preceded or followed by calcination of the catalyst, in a bed in the catalytic conversion reactor. The fact that calcination remains optional is very interesting: it is therefore possible, surprisingly, to dispense with calcination of the catalyst. This replaces a calcination step with a steam treatment step in the catalyst preparation process, which thus avoids lengthening the catalyst preparation time and complicating this preparation process.

[0037] Optional calcination of the catalyst can be carried out on the catalyst before or after the steam treatment, in the conversion reactor where the steam treatment is carried out. The calcination conditions are for example the following:

[0038] - rise in air at INl / h / g at 2°C / min up to 250°, 1h level;

[0039] - rise in air at INl / h / g at 2°C / min up to 550°C, 2h stage;

[0040] - temperature drop in air.

[0041] The vapor treatment of the catalyst may be preceded by (optional) drying of the catalyst particles outside the hydrocarbon catalytic conversion reactor, in particular at a temperature of at least 30°C, and preferably at most 150°C, in particular between 50 and 100°C, preferably between 70 and 90°C. Preferably, the drying of the catalyst is carried out following the preparation of the catalyst (mixing of the components then shaping). The dried catalyst may then be stored and then transferred to the installation where the conversion reactor is located. It has surprisingly been found that the catalyst, simply dried (and not calcined for example) has very high mechanical properties, which greatly facilitate its storage, transport and installation in the conversion reactor.In situ steam treatment then allows it to acquire the other desired properties, without requiring calcination (even if it can be provided as an option).

[0042] It has thus been found that the catalyst according to the invention, once dried, can have before steam treatment a mechanical resistance, measured by the average grain-by-grain crushing value, called average EGG, of at least 1 daN / mm, in particular at least 2 daN / mm and even at least 2.3 to 2.5 daN / mm, in the case where the catalyst is put in the form of extrudates.

[0043] The invention also relates to a process for preparing a catalyst comprising at least one aluminosilicate zeolite of the ZSM-5 family and a binder comprising silicon oxide, said process comprising i. a mixture of at least one ZSM-5 zeolite in powder form, said binder and / or a precursor of said binder, and optionally an additive ii. ii) shaping said mixture into catalyst particles iii) steam treatment of the catalyst obtained in step ii), said steam treatment being carried out - on the catalyst in the form of a catalytic bed of catalyst particles, - said bed being arranged in a hydrocarbon catalytic conversion reactor, - with a flow of vapor treatment gas passing through said bed and comprising water vapor, iii. - at a temperature of at least 150°C, iv. - and a pressure of at most 3.106 Pa.

[0044] Step iii) of this preparation process may comprise calcination of the catalyst, before or after the steam treatment in the bed in the catalytic conversion reactor, advantageously in situ therefore, like steam treatment iii).

[0045] Step iii) of this preparation process may be preceded by drying of the catalyst particles obtained in step ü) outside the hydrocarbon catalytic conversion reactor, in particular at a temperature of at least 30°C, and preferably at most 150°C, in particular between 50 and 100°C, preferably between 70 and 90°C.

[0046] The catalyst obtained in step ii) of this preparation process, then dried, may have, before step iii) of steam treatment, a mechanical resistance corresponding to the average grain-by-grain crushing value, called average EGG, of at least 1 daN / mm, in particular at least 2 daN / mm, when the catalyst is in the form of extrudates.

[0047] The invention also relates to a device for implementing the method described above, and which comprises a reactor for the catalytic conversion of hydrocarbons in which is arranged a catalytic bed of catalyst particles comprising at least one aluminosilicate zeolite of the ZSM-5 family, a binder comprising silicon oxide, and such that the reactor comprises means for injecting and discharging steam treatment gas comprising water vapor. As mentioned above, this is an “in-situ” implementation of the invention, where the flow of steam treatment gas will pass through the catalytic bed as will the hydrocarbon feedstock and / or a flow of reactant to be converted subsequently.

[0048] The invention also relates to the catalyst obtained by the treatment method or the treatment device described above.

[0049] The invention also relates to a process for converting ethylene or ethanol into propylene, other short olefins and gasoline or aromatic compounds, which uses a catalyst as treated and described above. The feedstock to be treated is brought into contact with the catalyst under the conditions of the conversion process, after possible activation of the catalyst.

[0050] The optional activation of the catalyst in the form of a bed of particles can take the form of a heat treatment such as drying at high temperature in air, and / or calcination aimed at burning off any traces of oil or grease that may be present.

[0051] The operating conditions of the ethylene conversion process are for example described in patent EP - 3 428 249, to which reference will be made for more details and which can be summarized as follows: use is made of a unit for converting ethylene into propylene and other products of interest, which is a catalytic unit using a zeolite-based catalyst working at a temperature of between 450°C and 650°C, and under a partial pressure of olefins of between 1 and 4 bars, i.e. between 0.1.106 Pa and 0.4.106 Pa, with an hourly weight rate (weight of olefinic feedstock per weight of catalyst and per hour) of between 0.1 and 10 h1, preferably between 1 and 7 h-1.

[0052] In the case where the reaction charge is ethanol, the latter is in a first dehydrated time into ethylene, which is transformed, under the same operating conditions as those of dehydration and on the same catalyst, in the presence of the water released by the dehydration reaction, into oligomers, that is to say into light C3-C6 olefins. The operating conditions of the ethanol conversion process are for example described in patent FR- 2 948 937, to which reference will be made for more details and which can be summarized as follows: for example a temperature between 300 and 600°C, preferably between 450 and 575°C, under a pressure between 0.1.106 and 1.5.106 Pa, preferably between 0.1.106 and 0.5.106 Pa, with an hourly weight rate (weight of ethanol feedstock per weight of catalyst and per hour) between 0.1 and 10 h *, preferably between 1 and 4 h1. Description of the embodiments

[0053] The invention relates to a catalyst comprising at least one zeolite or aluminosilicate of the ZSM-5 family and a binder comprising silicon oxide.

[0054] It is implemented in the following examples using three different catalysts having the following formulations:

[0055] Catalyst A

[0056] It comes in the form of extrudates (cylinders with a diameter of 1.4 mm and a length of between 2 and 6 mm) containing 60% by weight of ZSM-5 zeolite with an Si / Al atomic ratio of 140 (commercially available from the company Zeolyst, under the commercial reference CBV28014) and 40% of silicon oxide-based binder obtained from two sources of silica: - on the one hand from 20% (expressed on a dry basis) of silica gel available under the trade name Siliaflash C60 (grain size < 20 pm) and marketed by the company Silicycle;

[0057] - on the other hand from 20% (expressed on a dry basis) of colloidal silica, available under the trade name LUDOX™ AS-40 marketed by the company Grâce, and which is a suspension of colloidal slice at 40% weight in water.

[0058] Preparation of the catalyst

[0059] The preparation of the catalyst from the zeolite and the two silica sources was carried out with a shaping additive, here a cellulose derivative: METHOCEL ™, in a proportion of 4% by weight relative to the total dry solid, available from the company DuPont, and which is a polymer derived from cellulose and soluble in water.

[0060] The zeolite, silica sources, additive and water were mixed and kneaded. When the paste exhibited the appropriate rheology, it was extruded through a die.

[0061] Drying of the catalyst

[0062] After shaping into extrudates, and before the steam treatment according to the invention, the catalyst was dried at 80°C in air in an oven for 24 hours. Alternatively, the drying can be shorter (only a few hours, 5 to 10 hours for example) or longer, and can be carried out at slightly higher (90-100°C) or lower (60-70°C) temperatures.

[0063] Note that here the extrudate is cylindrical in shape, but alternatively it can have another shape, for example trilobed or quadrilobed.

[0064] Vapor treatment of the catalyst

[0065] The steam treatment according to the invention is carried out on catalyst A in the form of particles arranged in a catalytic bed in a hydrocarbon catalytic conversion reactor, said catalytic bed being crossed by a flow of steam treatment gas comprising water vapor, at a high temperature according to one embodiment, namely at least 400°C and a pressure of at most 3.106 Pa, in particular 106 Pa, for a duration of at most 10 hours, preferably at most 4 hours.

[0066] Alternatively, as indicated above, the vapotreatment according to the invention can also be carried out at a lower temperature (from 150 or from 180°C) and / or at a higher pressure, in particular up to 30 bars.

[0067] The experiments were conducted in a laboratory reactor simulating the enclosure of a catalytic conversion reactor: to do this, 10 g of catalyst are loaded into a tubular steel reactor so that it can be crossed by a vapor treatment fluid, in this case a gas flow containing water vapor and possibly other gases such as air or nitrogen, and to withstand high pressures. The unpacked thickness of the catalytic bed is 20 cm. This reactor is placed in a heating enclosure. The water is vaporized upstream of the reactor in another tubular reactor (called a "vaporizer") filled with silicon carbide, and the vaporizer-vapor treatment reactor junction lines are heated to 220°C. The gas injected at the same time as the water vapor also passes through the vaporizer.

[0068] The steam treatment according to the invention is defined by a temperature T in °C of the catalytic bed, a pressure P in bar / Pa (in the tubular reactor containing the catalyst), a duration D in hours of treatment, which corresponds to the duration during which the temperature T was reached and maintained (duration of the temperature plateau therefore), a flow rate Q of steam treatment gas passing through the catalytic bed expressed in NL / h / g (standardized liter per hour and per gram of catalyst), and a volume percentage of water vapor in the steam treatment gas comprising a mixture of water vapor and air.

[0069] The steam treatment conditions for catalyst A are as follows: - rise in air at INl / h / g at 5°C / min up to 150°C, 1h stage, then up to 600°C;

[0070] - change to 50 / 50% vol. H2O / air, 4-hour hold;

[0071] - temperature drop in air

[0072] - pressure: atmospheric P

[0073] Optional calcination of the catalyst

[0074] It can be carried out on the catalyst before or after the steam treatment, in the conversion reactor where the steam treatment is carried out.

[0075] The calcination conditions are as follows:

[0076] - rise in air at INl / h / g at 2°C / min up to 250°, 1h level;

[0077] - rise in air at INl / h / g at 2°C / min up to 550°C, 2h stage;

[0078] - temperature drop in air.

[0079] Catalyst B

[0080] Catalyst B is in the form of extrudates (cylinders with a diameter of 1.4 mm and a length of between 2 and 6 mm) containing 60% by weight of ZSM-5 zeolite with an Si / Al atomic ratio equal to 140 (commercially available from the company Zeolyst, under the commercial reference CBV28014) and 40% of silicon oxide-based binder obtained from two sources of silica:

[0081] - on the one hand from 20% (expressed on a dry basis) of silica gel available under the trade name Siliaflash C60 (grain size range 40-63pm) and marketed by the company Silicycle;

[0082] - on the other hand from 20% (expressed on a dry basis) of colloidal silica, available under the trade name LUDOX™ AS-40 marketed by the company Grâce, and which is a suspension of colloidal slice at 40% weight in water.

[0083] The catalyst is prepared according to the same protocol as that applied for catalyst A.

[0084] Catalyst C

[0085] Catalyst C is in the form of extrudates (cylinders with a diameter of 1.4 mm and a length of between 2 and 6 mm) containing 60% by weight of ZSM-5 zeolite with an Si / Al atomic ratio equal to 140 (commercially available from the company Zeolyst, under the commercial reference CBV28014) and 40% of silicon oxide-based binder obtained from two sources of silica:

[0086] - on the one hand from 20% (expressed on a dry basis) of precipitated silica powder, available under the trade name NYASIL™20 marketed by the company Nyacol Nano Technology) and which is an amorphous silica powder structured at the nanometric scale; - on the other hand from 20% colloidal silica, available under the trade name LUDOX™ AS-40 marketed by the company Grâce, and which is a suspension of colloidal slice at 40% weight in water.

[0087] The catalyst is prepared according to the same protocol as that applied for the ca- talyser A.

[0088] Example 1 (according to the invention)

[0089] Catalyst A was prepared, dried and then steam treated as indicated above.

[0090] Example 2 (according to the invention)

[0091] Catalyst B was prepared, dried and then steam treated as indicated above.

[0092] Example 3 (according to the invention)

[0093] Catalyst C was prepared, dried and then steam treated as indicated above.

[0094] Example 4 (comparative)

[0095] Catalyst A was prepared and then dried under the same conditions as in Example 1, but was not steam-treated. However, it was calcined in the conversion reactor.

[0096] Example 5 (comparative)

[0097] Catalyst B was prepared and then dried under the same conditions as in Example 2, but was not steam-treated. However, it was calcined in the conversion reactor.

[0098] Example 6 (comparative)

[0099] Catalyst C was prepared and then dried under the same conditions as in Example 3, but was not steam-treated. However, it was calcined in the conversion reactor.

[0100] Table 1 below gives textural characteristics of the catalysts treated according to examples 1 to 6:

[0101] - Vp Hg inf 7 pm: corresponds to the volume of pores with a diameter less than 7 mi crometers measured by mercury porosimetry;

[0102] - V macro Hg: corresponds to the volume representative of the macroporous volume (pore diameter between 50 nm and 7 pm measured by mercury intrusion;

[0103] - V meso Hg: corresponds to the representative volume of the mesoporous volume (diameter pores between 2 and 50 nm) measured by mercury intrusion;

[0104] - S BET: corresponds to the specific surface area measured by adsorption isotherm nitrogen;

[0105] - Vp N2: corresponds to the microporous volume obtained (pore diameter less than 2 nm) calculated from the nitrogen adsorption isotherm by the t-plot method;

[0106] - Average EGG: corresponds to the average breaking force in daN per mm of length The nitrogen adsorption isotherm measurement was carried out at 77 K following the ASTM D3663-03 standard, using a Micromeritics 2020 ASAP apparatus. Just before analysis, the sample was placed under secondary vacuum (1 xlO5 mbar) for 1 hour at 100°C and then for 4 hours at 450°C.

[0107] The measurement of pore volume by mercury porosimetry is carried out according to the ASTM D4284-03 standard. Just before analysis the sample is studied at 250°C overnight.

[0108] The EGG value is obtained via a standardized test (ASTM D4179-01 standard) which consists of subjecting a material in the form of a millimetric object to a force of com pressure generating rupture. This test is therefore a measure of the tensile strength of the material. The analysis is repeated on a certain number of individual solids and typically on a number of solids between 10 and 200. The average of the measured lateral rupture forces constitutes the average EGG.

[0109] [Tableauxl] example Vplnf7pm (cc / g) Vmacro Hg (cc / g) Vmeso Hg (cc / g) SBET (m2 / g) VpN2 (cc / g) EGG after drying (daN / mm) EGG of the final catalyst (daN / mm) Example 1 0.38 0.15 0.23 331 0.099 2.4 0.36 Example 2 0.33 0.12 0.21 332 0.097 2.7 0.32 Example 3 0.30 0.13 0.17 288 0.108 2.9 0.32 Example 4 (comp.) 0.41 0.17 0.24 324 0.107 2.4 0.10 Example 5 (comp.) 0.39 0.15 0.22 321 0.110 2.5 0.11 Example 6 (comp.) 0.23 0.09 0.13 291 0.104 2.9 0.31

[0110] It is noted that the catalyst of example 1 (dried then steam-treated) has porosity characteristics close to the catalyst of example 4 (dried then calcined): the steam-treatment slightly modifies the textural properties of the catalyst.

[0111] On the other hand, it can be seen that the catalyst dried only according to Example 1 has an EGG value more than 6 times higher than that of the catalyst of Example 1 which was subsequently steam-treated in situ: it is confirmed that a heat treatment of the steam-treatment type modifies the mechanical resistance of the catalyst, and that it is very advantageous to handle, transport, and install the catalyst in the catalytic conversion reactor before its steam treatment. Once in place in the reactor, it is no longer necessary for the catalyst to maintain a very high level of resistance, and the steam treatment can then be carried out, which is beneficial to the catalytic performance of the catalyst. The same trend is observed on catalysts 2 and 5, as well than on catalysts 3 and 6.

[0112] Measurements were also made to quantify the catalytic performance of the examples for converting ethylene predominantly to propylene.

[0113] After the in situ heat treatment (steam treatment or calcination depending on the examples), the reactor is then inerted under a nitrogen flow with a flow rate of 6NL / h then the hydrocarbon feedstock consisting of pure ethylene is injected.

[0114] For each test, 7 g of ethylene feedstock are injected per hour and per gram of catalyst. The reaction conditions used are a temperature of 500°C and a pressure of 0.17 MPa. At the reactor outlet, all of the effluent maintained in gaseous form by heating the transfer lines is analyzed by gas chromatography.

[0115] The catalytic performances thus obtained for each of the catalysts are given in Table 2 below. They are expressed using the following criteria: - the conversion of ethylene X(ethyl.) and the yield of propylene Y(propyl.) expressed as follows:

[0116] X(ethyl.) = 1 - (mass fraction of ethylene in the effluent)

[0117] Y(propyl.) = mass fraction of propylene in the effluent

[0118] - the purity of propylene within the cut consisting of propane and propylene P(propyh), corresponding to 55% conversion of ethylene, expressed as follows:

[0119] P(propyl.) = mass fraction of propylene in the effluent / mass fractions of propylene and propane in the effluent

[0120] The activity of the catalyst is characterized by the conversion of the initial ethylene X. The selectivity of the catalyst is characterized by the purity of propylene P and the yield of propylene Y. The stability of catalyst performance is quantified as follows:

[0121] Conversion stability = (initial conversion - conversion after 15 hours under load) / initial conversion

[0122] Stability of propylene yield = (initial propylene yield - propylene yield after 15 hours under load) / initial propylene yield

[0123] The catalytic performances thus obtained for each of the catalysts are given in Table 2 below.:

[0124] [Tables2] No. Example Initial X(ethyl. ) X(ethyl. ) after 15h under load Conversion loss after 15h (% relative) Initial Y(propyl •) Y(propyl .) after 15h under load Loss of propylene yield after 15h (% relative) P(propyl. ) for a conversion X(ethyl.) of 55% 1 63 55 13% 21 19 10% 94 2 61 47 23% 19 16 16% 95 3 60 40 33% 18 13 28% 95 4 (comp.) 60 5 92% 17 1.5 91% 93 5 (comp.) 58 4 93% 19 1.2 94% 92 6 (comp.) 59 10 83% 17 5 71% 95

[0125] It can be seen that the catalyst treated according to the invention (example 1) compared to the non-vapotreated reference catalyst (example 4) presents:

[0126] - a similar initial conversion but a significant gain in stability of the conversion;

[0127] - a similar initial propylene yield, but a significant gain in stability of this yield;

[0128] - a propylene purity at least equivalent to the reference.

Claims

Claims

1. Process for treating a catalyst comprising at least one aluminosilicate zeolite of the ZSM-5 family and a binder comprising silicon oxide, characterized in that said treatment comprises a steam treatment of the catalyst, said steam treatment being carried out - on the catalyst in the form of a catalytic bed of catalyst particles, - said bed being arranged in a hydrocarbon catalytic conversion reactor, in its functional position to carry out the catalysis by contacting with a hydrocarbon feedstock flow and / or a flow intended to react with a feedstock flow, - with a flow of steam treatment gas passing through said bed and comprising water vapor, - at a temperature of at least 150°C, - and a pressure of at most 3.106 Pa.

2. Method according to the preceding claim, characterized in that the pressure at which the vapor treatment is carried out is atmospheric pressure.

3. Method according to claim 1, characterized in that the pressure at which the vapotreatment is carried out is between 0.2.106 Pa and 3.10 6 Pa or 0.2.106 Pa and 106 Pa.

4. Method according to one of the preceding claims, characterized in that the temperature at which the steam treatment is carried out is at least 450 or 500°C, in particular between 500 and 700°C, preferably between 550 and 650°C, or between 150 and 250°C, in particular between 180 and 200°C.

5. Method according to one of the preceding claims, characterized in that the duration of vapotreatment is at most 24 hours, in particular at most 10 hours, or at most 5 hours, preferably between 1 hour and 3 hours.

6. Method according to one of the preceding claims, characterized in that the flow rate of the vapor treatment gas flow is between 0.01 and 0.1 NL per hour and per gram of catalyst, in particular between 0.01 and 0.05 NL per hour and per gram of catalyst.

7. Method according to one of the preceding claims, characterized in that the vapor treatment gas flow contains a gas mixture comprising water vapor and at least one other gas, in particular air and / or nitrogen, the water vapor content in the vapor treatment gas treatment being constant or evolving during at least part of the vaping treatment.

8. Method according to the preceding claim, characterized in that the volume proportion of water vapor in the vapor treatment gas is between 10 and 100%, in particular between 40 and 90%, preferably between 50 and 85%.

9. Method according to one of the preceding claims, characterized in that the binder comprises silicon oxide, preferably consists of silicon oxide, introduced into the catalyst at least partly in the form of colloidal silica and / or in the form of precipitated silica, preferably both in the form of colloidal silica and in the form of precipitated silica.

10. Method according to one of the preceding claims, characterized in that the catalyst comprises between 20 and 80% by weight of zeolite, in particular between 30 and 70% by weight of zeolite, and between 20 and 80% by weight of binder, in particular between 30 and 70% by weight of binder.

11. Method according to one of the preceding claims, characterized in that the Si / Al atomic ratio of the ZSM-5 zeolite is between 12 and 200, in particular between 35 and 180, preferably between 35 and 150.

12. Method according to one of the preceding claims, characterized in that the catalyst comprises at least one doping element, in particular part of the group consisting of sodium, potassium, magnesium, calcium, phosphorus, copper, silver, manganese, molybdenum.

13. Method according to one of the preceding claims, characterized in that the catalyst comprises at least two ZSM-5 zeolites, among which at least two have different Si / Al atomic ratios.

14. Method according to one of the preceding claims, characterized in that the vapor treatment of the catalyst is preceded or followed by calcination of the catalyst in a bed in the catalytic conversion reactor.

15. Method according to one of the preceding claims, characterized in that the vapor treatment of the catalyst is preceded by drying of the catalyst particles outside the hydrocarbon catalytic conversion reactor, in particular at a temperature of at least 30°C, and preferably at most 150°C, in particular between 50 and 100°C, preferably between 70 and 90°C.

16. Method according to the preceding claim, characterized in that the dried catalyst has, before steam treatment, a mechanical resistance corresponding to the average grain-by-grain crushing value, known as average EGG, of at least 1 daN / mm, in particular at least 2 daN / mm, in the case where the catalyst is in the form of extrudates.

17. Process for the preparation of a catalyst comprising at least one aluminosilicate zeolite of the ZSM-5 family and a binder comprising silicon oxide, said process comprising i) a mixture of at least one ZSM-5 zeolite in powder form, said binder and / or a precursor of said binder, and optionally an additive ii) shaping said mixture into catalyst particles iii) steam treatment of the catalyst obtained in step ii), said steam treatment being carried out - on the catalyst in the form of a catalytic bed of catalyst particles, - said bed being placed in a hydrocarbon catalytic conversion reactor, - with a flow of vapor treatment gas passing through said bed and comprising water vapor, - at a temperature of at least 150°C, - and a pressure of at most 3.106 Pa.

18. Device for implementing the method according to one of claims 1 to 16, characterized in that it comprises a reactor for the catalytic conversion of hydrocarbons in which is arranged a catalytic bed of catalyst particles comprising at least one aluminosilicate zeolite of the ZSM-5 family, a binder comprising silicon oxide, and in that the reactor comprises means for injecting and evacuating steam treatment gas comprising water vapor.