Method for treating a catalyst containing zeolite

Abstract

The present invention is a method for treating a catalyst comprising at least one ZSM-5 type aluminosilicate zeolite and a binder containing silicon oxide, said treatment comprising a steam treatment of the catalyst, said steam treatment being carried out on the catalyst in the form of a catalyst bed of catalyst particles, disposed in a reactor for catalytic conversion of hydrocarbons, with a steam treatment gas stream containing steam passing through said bed, at a temperature of at least 150 °C and at a pressure of up to 3×10 6 Pa.

Description

Technical Field

[0001] The present invention relates to a novel method for treating a material containing ZSM-5 zeolite. This material is advantageously used not only as a catalyst and as a catalyst support, but also as an adsorbent or a separating agent. More particularly, the present invention relates to the use of this material as a catalyst.

Background Art

[0002] Crystalline microporous materials, such as zeolites, are solids that are widely used in the petroleum industry as catalysts, particularly for heterogeneous catalysis of hydrocarbon isomerization, cracking or alkylation, or as catalysts for olefin conversion, such as the conversion of ethylene to propylene. However, this type of material can also be used as a catalyst support: by adding an active element, such as copper, an oxidation catalyst, particularly for the oxidation of ethanol to acetaldehyde, can be obtained, and copper can be combined with other elements, such as chromium. It is also possible to convert alcohol to gasoline with this type of material.

[0003] For the high-temperature catalytic oligomerization-decomposition reaction in the absence of hydrogen, ZSM-5 zeolite (of the MFI framework type) is one of the most studied active phases because it has several advantages. The confinement of reactants and products within the medium-pore microporous network of ZSM-5 (the openings have 10 tetrahedral atoms) promotes the desired reactions while ensuring the diffusion of products outside the pores. The Si / Al ratio, which determines the number of acid sites, can be adjusted over a wide range (from 15 to 400 atoms / atom) by the zeolite synthesis protocol. This zeolite with medium-pore openings and a three-dimensional pore network is much less susceptible to coking than more open zeolites (e.g., Y and beta zeolites of the FAU and BEA framework types, respectively) or one-dimensional closed zeolites (e.g., ZSM-22 of the TON framework type). The synthesis of zeolites also has an acceptable low cost for industrial applications. The refining and petrochemical industries are constantly looking for zeolite catalysts that have improved properties, especially with regard to the conversion of hydrocarbon species according to the application (yield and / or selectivity of the catalyzed reaction) and / or their stability over time, their mechanical strength, etc.

[0004] Patent Document 1 discloses a zeolite ZSM-5-based catalyst in the context of a method for converting methanol to gasoline, which is pretreated with steam at atmospheric pressure to increase its activity for this conversion, and calcination is carried out after or before this treatment.

[0005] Patent Document 2 also discloses zeolite-based catalysts, especially zeolite-based catalysts of the CHA zeolite type, in the context of a method for converting ethylene to propylene. What is recommended in this document is to reduce the number of acid sites of the zeolite specifically located on the surface of the material. It proposes several methods to do this, including surface silylation, steam treatment, or treatment with dicarboxylic acids.

[0006] Patent Document 3 further discloses a method for converting ethylene from a fraction resulting from a fraction of the effluent from the catalytic cracking unit into propylene, aromatic compounds, and other desired products: This conversion method is carried out in a conversion unit using a zeolite-based catalyst at a temperature of 500°C to 650°C and an olefin partial pressure of 1 to 2 bar. This catalyst contains, for example, ZSM-5 zeolite in a silica-type matrix.

[0007] The object of the present invention is to improve the performance of catalysts containing zeolites, especially zeolites of the ZSM-5 type, without asking about or making overly complicated the preparation method of the catalysts, and more particularly by targeting the conversion of ethylene or ethanol into propylene, other short-chain olefins, and other desired products.

[0008] In the context of the present invention, the resulting olefins can be used in all applications using short-chain olefins: after separation of each type of compound, monomers or polymers for plastics (polyethylene, polypropylene, polyester), or as a feedstock for methods capable of producing fuels (jet fuel, gasoline, distillates), either alone or as a mixture.

[0009] The present invention relates in particular to methods involving a fluid catalytic cracking process (generally called the FCC process). At the outlet of the reaction / regeneration assembly, there is a fractionation column, which makes it possible to separate the heavy fraction, heavy naphtha, and light fraction: the gas, LPG, and light gasoline at the top of the column. These light overhead fractions are then sent to a section for recovering the maximum amount of LPG and gasoline and, optionally, for purifying the gas before sending it to fuel gas. This gas, which is called "fuel gas", contains a significant amount of ethylene, and ethylene is often burned together with the fuel gas. This ethylene can be converted into propylene and other upgradable products, such as short-chain olefins and gasoline.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Means for Solving the Problems

[0011] (Summary of the Invention) The first subject of the present invention is a method for treating a catalyst comprising at least one aluminosilicate zeolite of the ZSM-5 family and a binder containing silicon oxide, said treatment comprising a steam treatment of the catalyst, said steam treatment being: - on the catalyst in the form of a catalyst bed of catalyst particles, - said bed being disposed within a catalytic hydrocarbon conversion reactor, - a steam treatment gas stream passing through said bed and containing water vapor, - at a temperature of at least 150°C, particularly at least 180°C, for example about 200°C, or at a temperature of up to 400°C and higher than 400°C, and - at a pressure of up to 3×10 6 Pa, particularly up to 10 6 Pa, which is carried out.

[0012] In the context of the present invention, the terms “silica” or “silicon oxide” also mean silicon oxide in a hydrated form in some cases. This can particularly apply, for example, in the case of extrudates where a steam treatment is carried out on a solid formed into particles by kneading-extrusion and only dried after formation.

[0013] The "particles" of the catalyst may be in various forms depending on the selected formation method: they may be pellets, beads or extrudates of various and generally regular shapes. The term "particle" in the context of the present invention comprehensively encompasses all possible shapes conventionally known for this type of catalyst.

[0014] The term "bed" is understood in its conventional meaning in the field of catalysts (catalyst bed): it is an arrangement in one or more layers of catalyst particles supported by conventional mechanical means (such as a metal screen) through which a gaseous or liquid flow can pass through its thickness. Thus, a fixed-bed type of bed where the particles do not move and do not move around in the reaction medium defined by the reactor in question is, therefore, considered here.

[0015] The temperature should here be understood as the temperature reached by the catalyst particles generally due to contact with a steam treatment gas stream having the same temperature.

[0016] The pressure should here be understood as the pressure inside the hydrocarbon conversion reactor.

[0017] Therefore, what has been shown in the context of this invention is that for this type of catalyst combining ZSM-5 zeolite and a silicate-type binder, steam treatment in the reactor itself at high temperature for the targeted catalytic conversion of hydrocarbons has brought very advantageous results even at mild pressure or atmospheric pressure: with the treated catalyst, it is possible to achieve higher conversion rates and / or yields of propylene and aromatic compounds in the case where the catalysis is the conversion reaction of ethylene to propylene, as well as greater stability of the conversion and / or yield.

[0018] However, most importantly, the present invention proposes to treat a catalyst in the form of a catalyst bed disposed in a catalytic hydrocarbon conversion reactor in which the catalyst in question will be used. This is called "in situ" steam treatment as long as the catalyst bed to be steam-treated is already in its functional position in the reactor to effect catalysis by contacting a hydrocarbon feed stream and / or a feed stream intended to react with it, such as hydrogen: the bed is thus first passed through by a steam treatment gas stream and then by a hydrocarbon feed / reactant stream. This is a very advantageous way of carrying out the steam treatment. This is because it limits the handling and intermediate storage of the catalyst, avoids the use of a dedicated steam treatment device, and also because a hydrocarbon conversion reactor is generally already equipped with all the appropriate means for implementing the present invention (means for injecting and discharging gases, means for heating the chamber / gas stream, and means for pressurizing, means for regulating these operating conditions, especially using sensors equipped in the reactor, etc.).

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

[0020] According to a second embodiment, the pressure at which the steam treatment is carried out is higher than atmospheric pressure, but preferably not very high. It is preferably from 2 bar to 30 bar, i.e. 0.2×10 6 Pa to 3×10 6 Pa, or from 2 to 10 bar, i.e. 0.2×10 6 Pa to 10 6 Pa, or from 3 to 8 bar, i.e. 0.3×10 6 Pa to 0.8×10 6 Pa.

[0021] According to one embodiment, the temperature at which the steam treatment is carried out is at least 450 °C or at least 500 °C, especially from 500 °C to 700 °C, preferably from 550 °C to 650 °C, in the region of 600 °C by way of example.

[0022] According to another embodiment, the temperature at which the steam treatment is carried out is lower, especially 150°C to 250°C, for example 180°C to 200°C. In this embodiment, the pressure at which the steam treatment is carried out is preferably 10 bar or more, that is, 10 6 Pa or more.

[0023] Preferably, the duration of the steam treatment is at most 24 hours, especially at most 10 hours, or at most 5 hours, preferably 1 hour to 3 hours. It is, therefore, an extremely short time and not so expensive in terms of the catalyst preparation time or the immobilization of the catalytic converter.

[0024] Preferably, the flow rate of the steam treatment gas stream at the inlet of the reactor is 0.01 to 0.1 NL per hour and per gram of the catalyst, especially 0.01 to 0.05 NL per hour and per gram of the catalyst.

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

[0026] Therefore, the volume ratio of water vapor in the steam treatment gas may be 10% to 100%, especially 40% to 90%, preferably 50% to 80%.

[0027] The water vapor content in the steam treatment gas may be constant or variable during at least part of the steam treatment. Choosing a constant water content is the simplest solution. There may also be advantages in varying it, especially in increasing it gradually or stepwise.

[0028] Similarly, the pressure and temperature during the steam treatment may be constant or variable, especially the temperature or pressure may increase gradually or in one or more steps.

[0029] According to the first modification, the binder contains silicon oxide and preferably consists of silicon oxide. It may be introduced during the preparation of the catalyst, at least partially in the form of colloidal silica and / or in the form of precipitated silica and / or silica gel, preferably in both the form of colloidal silica and the form of precipitated silica, or in both the form of colloidal silica and the form of silica gel. Such a binder is particularly inert towards the conversion reaction to be catalyzed compared to, for example, alumina, which is advantageous because it will increase the durability of the catalyst without interfering with the reaction to be catalyzed: this will, therefore, avoid any interference and any risk of promoting reactions that lead to unwanted by-products.

[0030] Preferably, the zeolite contained in the catalyst is 20 wt% to 80 wt%, especially 30 wt% to 70 wt%, or 50 wt% to 70 wt%, and the binder is 20 wt% to 80 wt%, for example 30 wt% to 70 wt%, or 30 wt% to 50 wt%.

[0031] For mixing and shaping the catalyst from zeolite (e.g., in powder form) and binder (e.g., in powder form or liquid form) or one or more precursors thereof, at least one additive may be added, the function of which may especially be to help control the viscosity of the mixture before shaping (e.g., a thickening additive), very particularly in the case where this shaping is the extrusion of a paste-form mixture. In the final catalyst, especially when it is heated / cured / fired, the additive disappears, especially when it is made of an organic material. It may be, for example, a cellulose derivative, especially methylcellulose.

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

[0033] The catalyst may contain at least one doping element, for example, those belonging to the group consisting of sodium, potassium, magnesium, calcium, phosphorus, copper, silver, manganese, and molybdenum. Preferably, the doping element is phosphorus, and in some cases, it is combined with one or more other elements. The content of the doping element is preferably such that the atomic ratio of the element to aluminum contained in the zeolite is 0.8 or less. 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 by any other type. Regarding the phosphorus element, it can be introduced, for example, by using one or more precursors of the type of phosphoric acid, ammonium dihydrogen phosphate, or hypophosphorous acid.

[0034] According to a variation, the catalyst according to the present invention contains at least two types of ZSM-5 zeolites (for example, mixed in a preliminary mixing step for preparing the catalyst), and at least two of them have different Si / Al atomic ratios. For example, the weight ratio is from 10 / 90 to 90 / 10, especially from 20 / 80 to 80 / 20, for example, from 40 / 60 to 60 / 40. In fact, the properties of the catalyst seem to be related, at least in part, to the content of Al sites in the zeolite: By combining two types of zeolites with different Si / Al ratios, it is possible to adjust the overall acidity of the material, and thus it is possible to more easily improve the compromise between the catalytic properties and the activity and selectivity of the catalyst.

[0035] The shaping of the catalyst particles can be carried out by any known method, for example, kneading / extrusion, oil-drop shaping, granulation, compression, or spray drying.

[0036] Before or after the steam treatment of the catalyst, in-bed calcination of the catalyst may be carried out in the catalytic conversion reactor. The fact that the calcination remains optional is highly advantageous: Thus, surprisingly, it is possible to omit the calcination of the catalyst. The calcination step is therefore replaced by the steam treatment step in the catalyst preparation method, which therefore avoids extending the catalyst preparation time and complicating this preparation method.

[0037] The optional calcination of the catalyst can be carried out on the catalyst in the conversion reactor where the steam treatment is carried out, before or after the steam treatment.

[0038] The calcination conditions are, for example, as follows: - Heating at 2 °C / min to 250 °C and holding for 1 hour in air at 1 NL / h / g; - Heating at 2 °C / min to 550 °C and holding for 2 hours in air at 1 NL / h / g; - Returning to the temperature in air.

[0039] Before the steam treatment of the catalyst, (optional) drying of the catalyst particles outside the catalytic hydrocarbon conversion reactor may be carried out first, and the temperature at that time is, inter alia, at least 30 °C, and preferably at most 150 °C, especially 50 °C to 100 °C, preferably 70 °C to 90 °C. Preferably, after the preparation of the catalyst (mixing of the components and subsequent shaping), the catalyst is dried. The dried catalyst can then be stored and then transferred to the plant where the conversion reactor is located. Surprisingly, simply dried (e.g., uncalcined) catalysts have very high mechanical properties, which have been found to greatly facilitate their storage, transportation and loading in the conversion reactor. The on-site steam treatment enables it to acquire other desired properties without the need for calcination (even if it can be provided optionally).

[0040] Therefore, the mechanical strength of the catalyst according to the present invention, when dried, is measured by the single pellet crush strength value, called average SPCS, before the steam treatment, and in the case where the catalyst is formed into extrudates, it has been found that it can be at least 1 daN / mm, especially at least 2 daN / mm, and even at least 2.3 - 2.5 daN / mm.

[0041] Another subject of the present invention is a method for preparing a catalyst comprising at least one aluminosilicate zeolite of the ZSM-5 family and a binder containing silicon oxide, said method comprising the following steps: i) mixing 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-treating the catalyst obtained in step ii). The steam treatment comprises: - on the catalyst in the form of a catalyst bed of catalyst particles, - said bed being arranged in a catalytic hydrocarbon conversion reactor, - a steam treatment gas stream passing through said bed and containing water vapor, - at a temperature of at least 150 °C and - at a pressure of at most 3×10 6 Pa. It is carried out.

[0042] Step iii) of this preparation method may advantageously be carried out on-site, before or after the in-bed steam treatment in the catalytic conversion reactor, and thus may include the calcination of the catalyst, similar to the steam treatment iii).

[0043] Before step iii) of this preparation method, the drying of the catalyst particles obtained in step ii) may preferably be carried out in advance outside the catalytic hydrocarbon conversion reactor, and the temperature at that time is at least 30 °C and preferably at most 150 °C, especially 50 °C to 100 °C, preferably 70 °C to 90 °C.

[0044] The mechanical strength of the catalyst obtained in step ii) of this preparation method and then dried corresponds to the crushing strength value of a single pellet called average SPCS before the steam treatment step iii), and when the catalyst is in the form of an extrudate, it is at least 1 daN / mm, especially at least 2 daN / mm.

[0045] Another subject of the present invention is a device for carrying out the above method, which comprises a catalytic hydrocarbon conversion reactor, in which a catalyst bed of catalyst particles containing at least one aluminosilicate zeolite of the ZSM-5 type and a binder containing silicon oxide is arranged, and for this reason, the reactor is provided with means for injecting and discharging a steam treatment gas containing water vapor. As described above, this is an "in-situ" embodiment of the present invention, where the steam treatment gas stream will pass through the catalyst bed, similar to the stream of hydrocarbon feedstock and / or reactants to be converted later.

[0046] Another subject of the present invention is the catalyst obtained by the above treatment method or treatment device.

[0047] Another subject of the present invention is a method for converting ethylene or ethanol into propylene, other short-chain olefins and gasoline or aromatic compounds, and the method uses the catalyst treated and described as above. The feedstock to be treated is brought into contact with the catalyst under the conditions of the conversion method after optional activation of the catalyst.

[0048] Optional activation of the catalyst in the form of a bed of particles can take the form of a heat treatment of the drying type at high temperature in air and / or a firing aimed at burning off any trace amounts of oil or grease present.

[0049] The operating conditions of the ethylene conversion process are described, for example, in Patent EP-3428249, to which reference should be made for more details and which can be summarized as follows: A unit for the conversion of ethylene to propylene and other products of interest is used, which is a catalyst unit using a zeolite-based catalyst and is operated at a temperature of 450 °C to 650 °C and an olefin partial pressure of 1 to 4 bar, i.e., 0.1×10 6 Pa to 0.4×10 6 Pa, and the hourly weight space velocity (weight of the olefinic feedstock per weight of catalyst and per hour) is 0.1 to 10 h ?1 , preferably 1 to 7 h -1 .

[0050] In the case where the reaction feedstock is ethanol, the ethanol is first dehydrated to ethylene, which is then converted to oligomers, i.e., C3-C6 light olefins, under the same operating conditions as for the dehydration and in the presence of the water released by the dehydration reaction on the same catalyst. The operating conditions of the ethanol conversion process are described, for example, in Patent FR-2,948,937, to which reference may be made for details and which can be summarized as follows: For example, the temperature is 300 °C to 600 °C, preferably 450 °C to 575 °C, the pressure is 0.1×10 6 to 1.5×10 6 Pa, preferably 0.1×10 6 to 0.5×10 6 Pa, and the hourly weight space velocity (weight of the ethanol feedstock per weight of catalyst and per hour) is 0.1 to 10 h -1 , preferably 1 to 4 h -1 .

Mode for Carrying Out the Invention

[0051] (Description of Embodiment) The present invention relates to a catalyst comprising at least one zeolite or aluminosilicate of the ZSM-5 type and a binder containing silicon oxide.

[0052] It is implemented in the following examples using three different catalysts having the following formulations.

[0053] (Catalyst A) It is in the form of an extrudate (a cylinder with a diameter of 1.4 mm and a length of 2 - 6 mm), containing 60 wt% of ZSM-5 zeolite with a Si / Al atomic ratio equal to 140 (commercially available from Zeolyst under the commercial reference number CBV28014) and 40 wt% of a silicon oxide binder, which is obtained from the following two sources of silica: - On the one hand, 20% (expressed in terms of dry weight) of silica gel; available under the trade name Siliaflash C60 (particle size < 20 μm) and sold by SiliCycle; - On the other hand, 20% (expressed in terms of dry weight) of colloidal silica; available under the trade name LUDOX® AS-40 and sold by Grace; this is a 40 wt% suspension of colloidal silica in water.

[0054] (Preparation of Catalyst) The preparation of the catalyst from the zeolite and the two silica sources was carried out with a forming additive, here a cellulose derivative: METHOCEL®. The cellulose derivative: METHOCEL® is present in a proportion of 4 wt% relative to all of the dry solids, is available from DuPont, and is a water-soluble polymer derived from cellulose.

[0055] The zeolite, silica sources, additive and water were mixed and kneaded. When the paste had the appropriate rheology, it was extruded through a die.

[0056] (Drying of Catalyst) The drying of the catalyst was carried out in a drying oven in air at 80 °C for 24 hours after shaping it into the form of an extrudate and before the steam treatment according to the invention. As a variation, the drying may be shorter (only a few hours, for example 5 to 10 hours) or longer, and may be carried out at a slightly higher temperature (90 to 100 °C) or a lower temperature (60 to 70 °C).

[0057] It should be noted here that the extrudate is in the shape of a cylinder, but alternatively it can have another shape, for example a three - or four - leaf shape.

[0058] (Steam treatment of the catalyst) The steam treatment according to the invention is carried out on catalyst A in the form of particles arranged in a catalyst bed in a catalytic hydrocarbon conversion reactor, and a steam treatment gas stream containing steam of water passes through the catalyst bed at a high temperature, that is, at least 400 °C and a maximum of 3×10 6 Pa, especially at a maximum of 10 6 Pa, for a maximum of 10 hours, preferably for a maximum of 4 hours.

[0059] Alternatively, as indicated above, the steam treatment according to the invention can also be carried out at a lower temperature (starting from 150 °C or 180 °C) and / or a higher pressure, especially at a maximum of 30 bar.

[0060] Experiments were carried out in a laboratory reactor simulating the chamber of a catalytic conversion reactor: to do this, 10 g of the catalyst was loaded into a tubular steel reactor, and the steam treatment fluid was made to flow through it. This fluid is, in this case, a gas stream that contains steam of water and may also contain other gases of the air or nitrogen type and is made to withstand high pressures. The uncompressed thickness of the catalyst bed is 20 cm. This reactor is placed in a heating chamber. Water is vaporized upstream of the reactor in another tubular reactor (referred to as a "vaporizer") filled with silicon carbide, and the connecting line between the vaporizer and the steam treatment reactor is heated to 220 °C. The gas injected simultaneously with the steam of water also passes through the vaporizer.

[0061] The steam treatment according to the present invention is defined by the temperature T (°C) of the catalyst bed, the pressure P (bar / Pa) (in the tubular reactor containing the catalyst), the treatment time D (hours) corresponding to the time until and during which the temperature T is reached and maintained (thus, the duration of the temperature held), the flow rate Q of the steam treatment gas passing through the catalyst bed expressed in NL / h / g (normal liters per hour and per gram of catalyst weight), and the volume percentage of steam in the steam treatment gas containing a mixture of steam and air of water.

[0062] The steam treatment conditions for Catalyst A are as follows: - Heating from room temperature to 150°C at 5°C / min at 1 NL / h / g in air, holding for 1 hour, and then heating to 600°C; - Passing through in 50 / 50 vol% H2O / air and holding for 4 hours; - Returning to the original temperature in air; - Pressure: atmospheric pressure P.

[0063] (Optional calcination of the catalyst) It can be carried out on the catalyst in the conversion reactor where the steam treatment is carried out, either before or after the steam treatment.

[0064] The calcination conditions are as follows: - Heating from room temperature to 250°C at 2°C / min at 1 NL / h / g in air and holding for 1 hour; - Heating from room temperature to 550°C at 2°C / min at 1 NL / h / g in air and holding for 2 hours; - Returning to the original temperature in air.

[0065] (Catalyst B) Catalyst B is in the form of extrudates (cylinders with a diameter of 1.4 mm and a length of 2 - 6 mm) and contains 60 wt% of ZSM-5 zeolite with a Si / Al atomic ratio equal to 140 (commercially available from Zeolyst under the commercial reference number CBV28014) and 40 wt% of a silica oxide binder, and the binder is obtained from the following two sources of silica: - On the one hand, 20% (expressed in terms of dry weight) of silica gel (particle size 40 - 63 μm); available under the trade name Siliaflash C60 and sold by SiliCycle; - On the other hand, 20% (expressed in terms of dry weight) of colloidal silica; available under the trade name LUDOX® AS - 40 and sold by Grace; this is a 40 wt% suspension of colloidal silica in water.

[0066] The catalyst is prepared according to the same protocol as applied to Catalyst A.

[0067] (Catalyst C) Catalyst C is in the form of extrudates (cylinders with a diameter of 1.4 mm and a length of 2 - 6 mm) and contains 60 wt% of ZSM - 5 zeolite (commercially available from Zeolyst under the commercial reference number CBV28014) with an Si / Al atomic ratio equal to 140 and 40 wt% of a silica oxide binder, and the binder is obtained from the following two sources of silica: - On the one hand, 20% (expressed in terms of dry weight) of precipitated silica powder; available under the trade name NYASIL® 20 and sold by Nyacol Nano Technology; this is a nanostructured amorphous silica powder; - On the other hand, 20% of colloidal silica; available under the trade name LUDOX® AS - 40 and sold by Grace; this is a 40 wt% suspension of colloidal silica in water.

[0068] The preparation of the catalyst is carried out according to the same protocol as applied to Catalyst A.

[0069] (Example 1 (in accordance with the present invention)) Catalyst A was prepared, dried, and then steam - treated as indicated above.

[0070] (Example 2 (in accordance with the present invention)) Catalyst B was prepared, dried, and then steam-treated as indicated above.

[0071] (Example 3 (in accordance with the present invention)) Catalyst C was prepared, dried, and then steam-treated as indicated above.

[0072] (Example 4 (comparative)) 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 a conversion reactor.

[0073] (Example 5 (comparative)) 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 a conversion reactor.

[0074] (Example 6 (comparative)) 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 a conversion reactor.

[0075] The following Table 1 gives the texture characteristics of the catalysts treated according to Examples 1 to 6: - Vp Hg inf 7μm: corresponds to the pore volume of pores with a diameter less than 7 micrometers measured by mercury porosimetry; - V macro Hg: corresponds to the volume corresponding to the macro pore volume (pore diameter 50 nm to 7 μm) measured by mercury intrusion; - V meso Hg: corresponds to the volume corresponding to the meso pore volume (pore diameter 2 to 50 nm) measured by mercury intrusion; - S BET: corresponds to the specific surface area measured by nitrogen adsorption isotherm; - Vμ N2: corresponds to the obtained micro pore volume (pore diameter less than 2 nm) calculated from the nitrogen adsorption isotherm by the t-plot method; - Average PPC: Corresponds to the average breaking load (daN per mm length). The nitrogen adsorption isotherm was measured at 77 K according to ASTM D3663-03 using a Micromeritics 2020 ASAP apparatus. Immediately before analysis, the sample was placed under high vacuum (1×10 -5 mbar) at 100 °C for 1 hour and then at 450 °C for 4 hours.

[0076] The pore volume is measured by mercury porosimetry according to standard ASTM D4284-03. Immediately before analysis, the sample is placed in an oven at 250 °C overnight.

[0077] The SPCS value is obtained via a normalization test (standard ASTM D4179-01) that consists of subjecting a material in the form of a millimeter-scale object to a compressive force and breaking it. This test is, therefore, a measurement of the tensile strength of the material. The analysis is repeated on a certain number of individually taken solids, typically on a large number of 10 to 200 solids. The average of the measured transverse breaking loads is the average SPCS.

[0078]

Table 1

[0079] It is found that the porosity characteristics of the catalyst of Example 1 (catalyst dried and then steam-treated) are similar to those of the catalyst of Example 4 (catalyst dried and then calcined): steam treatment slightly modifies the texture characteristics of the catalyst.

[0080] However, it can be understood that the SPCS value of the catalyst that was only dried according to Example 1 is six times higher than the SPCS value of the catalyst of Example 1 that was subsequently subjected to in-situ steam treatment: that the heat treatment of the steam treatment type modifies the mechanical strength of the catalyst, and that it is very advantageous to handle, transport, and mount the catalyst in the catalytic conversion reactor before that steam treatment. Once placed in the reactor, it is actually no longer necessary for the catalyst to maintain a very high level of strength, and the steam treatment can then be carried out, which is in itself beneficial for the catalytic performance of the catalyst. The same tendency is also observed for Catalysts 2 and 5, as well as for Catalysts 3 and 6.

[0081] Measurements were also carried out to quantify the catalytic performance of the examples with respect to the conversion of ethylene mainly to propylene.

[0082] After the in-situ heat treatment (steam treatment or calcination according to the example), the reactor is then made inert under a nitrogen flow rate of 6 NL / h, and then a hydrocarbon feedstock consisting of pure ethylene is injected.

[0083] For each test, 7 g of ethylene feedstock per hour and per gram of catalyst weight is injected. The reaction conditions used are a temperature of 500 °C and a pressure of 0.17 MPa. At the outlet of the reactor, the entire effluent maintained in gaseous form by heating the transfer line is analyzed by gas chromatography.

[0084] The catalytic performance characteristics thus obtained for each of the catalysts are shown in Table 2 below. They are expressed using the following criteria: - The conversion rate of ethylene X (ethyl) and the yield of propylene Y (propyl) expressed as follows: X (ethyl) = 1 - (weight fraction of ethylene in the effluent) Y (propyl) = weight fraction of propylene in the effluent - The purity P (propyl) of propylene in the fraction consisting of propane and propylene corresponds to a 55% conversion rate of ethylene and is expressed as follows: P(propyl) = weight fraction of propylene in the effluent / weight fraction of propylene and propane in the effluent The activity of the catalyst is characterized by the initial ethylene conversion rate X. The selectivity of the catalyst is characterized by the propylene purity P and the propylene yield Y.

[0085] The stability of the catalyst performance is quantified as follows: Conversion stability = (initial conversion rate - conversion rate after 15 hours under the feedstock) / initial conversion rate Stability of propylene yield = (initial propylene yield - propylene yield after 15 hours under the feedstock) / initial propylene yield The catalyst performance values thus obtained for each catalyst are shown in Table 2 below.

[0086]

Table 2

[0087] It can be understood that the catalyst treated according to the present invention (Example 1) has the following compared to the untreated reference catalyst (Example 4): - Similar initial conversion rate, but a significant increase in conversion stability; - Similar initial propylene yield, but a significant increase in the stability of this yield; - At least equivalent propylene purity to the reference.

Claims

1. A method for treating a catalyst comprising at least one aluminosilicate zeolite of the ZSM-5 system and a binder containing silicon oxide, said treatment comprising steam treatment of the catalyst, said steam treatment being - on the catalyst in the form of a catalyst bed of catalyst particles, - said bed being arranged in a catalytic hydrocarbon conversion reactor, - a steam treatment gas stream passing through said bed and containing water vapor, - at a temperature of at least 150 °C, and - up to 3×10 ６ Pa pressure characterized in that it is carried out.

2. The method according to claim 1, characterized in that the pressure at which the steam treatment is carried out is atmospheric pressure.

3. The pressure during the steam treatment is 0.2×10 ６ Pa to 3×10 ６ Pa or 0.2×10 ６ Pa to 10 ６ Pa, and the method according to claim 1 is characterized by this.

4. The temperature at which the steam treatment is carried out is at least 450 °C or at least 500 °C, especially 500 °C to 700 °C, preferably 550 °C to 650 °C, or 150 °C to 250 °C, especially 180 °C to 200 °C, according to any one of claims 1 to 3. The method described.

5. The method according to any one of claims 1 to 4, characterized in that the duration of the steam treatment is at most 24 hours, especially at most 10 hours, or at most 5 hours, preferably 1 hour to 3 hours.

6. The flow rate of the steam treatment gas stream is 0.01 to 0.1 NL per hour and per gram of catalyst weight, especially 0.01 to 0.05 NL per hour and per gram of catalyst weight, according to any one of claims 1 to 5. The method described.

7. The steam treatment gas stream contains a gas mixture containing water vapor and at least one other gas, especially air and / or nitrogen, and the content of water vapor in the steam treatment gas is constant or varies during at least part of the steam treatment. The method according to any one of claims 1 to 6, characterized in that

8. The method according to claim 7, characterized in that the volume ratio of water vapor in the steam treatment gas is 10% to 100%, especially 40% to 90%, preferably 50% to 85%.

9. The binder contains silicon oxide, preferably consists of silicon oxide, and is introduced into the catalyst at least partially in the form of colloidal silica and / or in the form of precipitated silica, preferably in both the form of colloidal silica and the form of precipitated silica. The method according to any one of claims 1 to 8, characterized in that

10. The catalyst according to any one of claims 1 to 9, characterized in that it contains 20% to 80% by weight of zeolite, in particular 30% to 70% by weight of zeolite, and 20% to 80% by weight of binder, in particular 30% to 70% by weight of binder.

11. The method according to any one of claims 1 to 10, characterized in that the Si / Al atomic ratio of the ZSM-5 zeolite is 12 to 200, in particular 35 to 180, preferably 35 to 150.

12. The method according to any one of claims 1 to 11, characterized in that the catalyst contains at least one doping element, in particular belonging to the group consisting of sodium, potassium, magnesium, calcium, phosphorus, copper, silver, manganese and molybdenum.

13. The method according to any one of claims 1 to 12, characterized in that the catalyst contains at least two types of ZSM-5 zeolites, at least two of which have different Si / Al atomic ratios.

14. The method according to any one of claims 1 to 13, characterized in that the catalyst is calcined as a bed in the catalytic conversion reactor before or after the steam treatment of the catalyst.

15. Before the steam treatment of the catalyst, the drying of the catalyst particles is carried out outside the catalytic hydrocarbon conversion reactor, and the temperature at that time is at least 30°C, and preferably at most 150°C, in particular 50°C to 100°C, preferably 70°C to 90°C. The method according to any one of claims 1 to 14, characterized in that.

16. The mechanical strength of the dried catalyst corresponds to the crushing strength value of the average single pellet called average SPCS before the steam treatment, and in the case where the catalyst is formed into extrudates, it is at least 1 daN / mm, in particular at least 2 daN / mm. The method according to claim 15, characterized in that.

17. A method for preparing a catalyst containing at least one aluminosilicate zeolite of the ZSM-5 type and a binder containing silicon oxide, the method comprising: i) a step of mixing at least one ZSM-5 zeolite in powder form with the binder and / or a precursor of the binder, and optionally an additive; ii) a step of shaping the mixture into catalyst particles; iii) a step of steam-treating the catalyst obtained in step ii) The steam treatment includes: - on a catalyst in the form of a catalyst bed of catalyst particles, - said bed being disposed within a catalytic hydrocarbon conversion reactor, - a steam treatment gas stream passing through said bed and containing water vapor, - at a temperature of at least 150 °C, and - Up to 3×10 ６ Pa pressure a method carried out.

18. A device for carrying out the method according to any one of claims 1 to 17, comprising a catalytic hydrocarbon conversion reactor, within which is disposed a catalyst bed of catalyst particles comprising at least one aluminosilicate zeolite of the ZSM-5 type and a binder containing silicon oxide, the reactor being provided with means for injecting and discharging a steam treatment gas containing water vapor.

19. A method for the catalytic conversion of a feedstock containing ethylene or ethanol to propylene and gasoline or aromatic compounds, comprising the step of contacting said feedstock with a catalyst treated as described in any one of claims 1 to 16 or a catalyst prepared as described in claim 17.

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