Tantalum and silica based catalysts for converting a feedstock comprising ethanol to butadiene

Abstract

This invention relates to catalysts comprising tantalum and a silica-based matrix, wherein the catalyst has a tantalum content between 0.1% and 30% by weight relative to the silica-based matrix, and a tantalum content greater than or equal to 1000 au / g. Ta The Lewis acidity content, wherein the Lewis acidity content is determined by Fourier transform infrared spectroscopy (FTIR) after pyridine adsorption and subsequent thermal desorption. The invention also relates to the use of the catalyst in the conversion of a feedstock containing ethanol into butadiene.

Description

Technical Field

[0001] This invention relates to heterogeneous catalysts for the optimal conversion of ethanol-containing feedstocks to 1,3-butadiene (which may also be referred to as butadiene in this specification). More particularly, this invention relates to catalysts comprising elemental tantalum and a silica-based support (or matrix) that exhibit optimal catalytic performance levels during the conversion of feedstocks containing ethanol and preferably a mixture of ethanol and acetaldehyde to butadiene, and particularly optimized butadiene selectivity and optimized butadiene productivity. Existing technology

[0002] Butadiene is widely used in the chemical industry, particularly as a reactant in the production of polymers. Currently, butadiene is produced almost entirely by steam cracking units, where it is an upgradable byproduct. Fluctuations in oil prices and the increasing demand for this chemical intermediate make its price highly volatile, prompting diversification of its supply methods. For example, it is well known to those skilled in the art that 1,3-butadiene can be produced from ethanol. Two methods have undergone large-scale industrialization, particularly in the 1940s and 1950s: the "SK method" and the "carbide method." In the "SK method," 1,3-butadiene is produced from ethanol in a single step, while in the "carbide method," it is produced in two steps: first, ethanol is converted to acetaldehyde, and then the ethanol-acetaldehyde mixture is converted to 1,3-butadiene. The main difference between the catalysts used in these methods is that one catalyst (SK method) can dehydrogenate ethanol to acetaldehyde, and simultaneously produce butadiene from the resulting mixture, while another catalyst cannot (thus requiring a first dehydrogenation step on a specific catalyst). The most effective catalysts for this butadiene production method are magnesium, tantalum, zirconium, and hafnium, with selectivity for butadiene ranging from 50% to 69%. Niobium is considered less attractive, with selectivity less than 40% (see BB Corson et al.). , Butadienefrom Ethyl Alcohol. Catalysis in the One- and Two-Step Processes. Industrial And Engineering Chemistry. 1950, 42 (2), 359-373).

[0003] Regardless of the method used (one-step or two-step), the overall equilibrium of the main reaction can be written as follows: 2 CH3CH2OH CH2CHCHCH2+ H2+ 2 H2O Behind this overall equilibrium are a number of chemical reactions, including the dehydrogenation reaction for the production of acetaldehyde (I), the aldol condensation / butenaldehyde reaction for the production of crotonaldehyde from acetaldehyde (II), the Meerwein-Ponndorf-Verley (MPV) reaction between ethanol and crotonaldehyde (III), and the final step of dehydrating crotonol to produce butadiene (IV).

[0004] I: CH3CH2OH CH3CHO + H2 II: 2 CH3CHO CH3CHCH-CHO + H2O III: CH3CHCH-CHO + CH3CH2OH CH3CHCH-CH2OH + CH3CHO IV: CH3CHCH-CH2OH CH2CHCHCH2+ H2O If the steps are not performed in the order specified above, this diversity of chemical reactions is a source of numerous byproducts, especially in the presence of secondary dehydration and condensation reactions. Furthermore, other reactions (such as isomerization, cyclization, and Diels-Alder reactions) may occur, further increasing the number of byproducts. Thus, depending on the nature of the catalyst used to convert ethanol (or an ethanol-acetaldehyde mixture) to 1,3-butadiene, the distribution of these byproducts can vary significantly. For example, the addition of acidic elements, particularly Brønsted acidic elements, will increase the production of dehydration products (e.g., ethylene or diethyl ether), while the addition of basic elements will promote the formation of multiple condensation products (e.g., hexene or hexadiene).

[0005] Therefore, regardless of the method (one-step or two-step), the selectivity and productivity of converting ethanol-containing feedstocks to 1,3-butadiene are moderate. However, due to the relatively high cost of starting materials, economic analysis of this method shows that the conversion efficiency of the feedstock constitutes an important tool for ensuring its feasibility. Consequently, considerable efforts have been made to maximize the catalytic performance of catalysts used for the conversion of ethanol (or ethanol-acetaldehyde mixtures) to 1,3-butadiene, and especially the selectivity and carbon productivity of butadiene.

[0006] In particular, during the development of methods for producing butadiene from ethanol / acetaldehyde mixtures (two-step process) in the 1940s and 1950s, the best catalyst found was tantalum oxide deposited on amorphous silica (Ind. Eng. Chem., 1949, 41, pp. 1012-1017). With an initial feed conversion of 34%, the butadiene selectivity was 69%. It has also been shown that the use of this same catalyst in industrial “carbide” units results in the formation of the following major impurities (byproducts): diethyl ether (23 wt% of the impurities), ethylene (11 wt% of the impurities), hexene, hexadiene (11 wt% of the impurities), etc. (WJ Toussaint, JT Dunn, DR Jackson, Industrial and Engineering Chemistry, 1947, 39 (2), pp. 120-125). Despite the presence of byproducts, their formation is limited by the relatively weak acidity / basicity properties of elemental tantalum. The latter also makes it possible to catalyze reactions II, III, and IV very efficiently.

[0007] Various studies were subsequently conducted to optimize the efficiency of tantalum and / or replace the element. For example, patent US2421361 describes a method for preparing butadiene, which includes converting monoalkenal acyclic aldehydes (crotonaldehyde or acetaldehyde) and monohydroxy alcohols (ethanol) on a catalyst selected from zirconium oxide, tantalum oxide, niobium oxide, and combinations of these oxides with silica. However, according to the provided examples, tantalum oxide alone remains the best catalyst for converting specific ethanol / acetaldehyde mixtures. According to Ind. Eng. Chem., 1950, 42 (2), pp. 359-373, the best combination for converting ethanol / acetaldehyde mixtures is: Ta-Cu, Ta-Zr, Zr-Nb, Zr-Ti, and Zr-Th deposited on a silica support (patents US2374433, US2436125, US2438464, US2357855, and US2447181).

[0008] Many studies have also focused on improving silica supports and / or optimizing methods for preparing heterogeneous catalysts, particularly tantalum and silica-based heterogeneous catalysts. For example, application WO2014 / 061917 describes a catalyst based on tantalum and silica supports, characterized by regularly distributed mesopores (“mesoporous” silica) of uniform size and morphology within the material. Application WO2017 / 009107 discloses, in itself, a catalyst comprising elemental tantalum and an acid-washed silica-based mesoporous oxide matrix. More recently, application WO2022 / 165190 describes a method for preparing a tantalum and silica-based catalyst by organic deposition of a specific tantalum precursor having a controlled distribution of tantalum within silica particles, the specific tantalum precursor preferably selected from tantalum ethoxide, particularly tantalum tetraethoxide 2,4-pentanedionate (optionally combined with acetylacetone) or tantalum pentaethoxylate. Patent application CN115364844 describes the preparation of a tantalum- and silica-based catalyst by contacting silica with an anhydrous ethanol solution containing a tantalum precursor and anhydrous citric acid. Finally, Ushikubo's team compared a tantalum oxide-on-silica catalyst prepared from a hexane solution of tantalum alkoxide with a tantalum oxide-on-silica catalyst prepared by impregnating silica with a 1M hydrochloric acid aqueous solution containing 1 wt% TaCl5, for the vapor-phase decomposition of methyl tert-butyl ether (Ushikubo T et al.: “Preparation, characterization, and catalytic activities of silica-supported tantalum oxide for the vaporphase decomposition of methyl tert-butyl ether”, Applied Catalysis A: General, Vol. 124, No. 1, March 1, 1995 (1995-03-01), pp. 19-31).

[0009] There is still a need to improve the catalytic performance of catalysts containing elemental tantalum and silica supports. Therefore, the object of this invention is to provide a heterogeneous catalyst based on tantalum and silica for converting ethanol-containing feedstocks into butadiene (or 1,3-butadiene), exhibiting optimized catalytic performance, particularly optimized butadiene selectivity and optimized butadiene productivity. Invention Overview The present invention thus relates to catalysts comprising tantalum and a silica-based matrix, said catalyst having a tantalum content between 0.1% and 30% by weight relative to the silica-based matrix, said catalyst having a tantalum content greater than or equal to 1000 au / g. Ta Lewis acidity content [LAS], The Lewis acidity (LAS) content is determined by the ratio of 1622 to 1593 cm⁻¹. -1 Area A in the IR spectrum within the wavenumber range 1612 The IR spectrum was determined by integration and calculation using the following method, obtained by Fourier transform infrared spectroscopy (FTIR) of a sample of the catalyst that had been reduced into powder and subsequently pelletized, following adsorption and subsequent thermal desorption of pyridine at 150 °C: Where S corresponds to the surface area of ​​the sample pellet (in cm²) 2 [Ta] is the unit of measurement, and [Ta] corresponds to the weight content of tantalum in the catalyst per unit weight of the catalyst.

[0011] Surprisingly, the catalyst according to the invention, based on a tantalum and silica matrix and having such an amount of acid sites per unit weight of tantalum, exhibits an optimized level of catalytic performance during the conversion of ethanol-containing feedstocks into 1,3-butadiene, particularly in terms of butadiene selectivity and butadiene productivity. Thus, the catalyst according to the invention, used to convert feedstocks containing ethanol, particularly ethanol-acetaldehyde feedstocks (especially at an ethanol / acetaldehyde molar ratio of 2.6) to 1,3-butadiene, particularly at a reaction temperature of 350°C and a pressure of 0.15 MPa, enables high butadiene selectivity, particularly for 40% by weight of feedstock, with a conversion rate greater than or equal to 70%, preferably greater than or equal to 72%, and satisfactory butadiene productivity, particularly for 250 g / g Ta / h of feedstock with a gravity space velocity (gravity space velocity or WWH is expressed as the weight of tantalum per unit weight in the catalyst used to convert the feedstock and the weight of the feedstock per hour) greater than or equal to 30 g / g Ta / h (g / g Ta / h refers to the number of grams of butadiene produced per hour per gram of tantalum in the catalyst used to convert the feedstock), preferably greater than or equal to 32 g / g Ta / h.

[0012] The present invention also relates to the use of the catalyst according to the invention for converting a feedstock containing ethanol into butadiene at a temperature between 250 and 450°C and a pressure between 0.05 and 2.00 MPa. Invention Details According to the present invention, the expressions "between... and..." and "between... and..." are equivalent, and refer to the fact that the limit value of the interval is included in the range of the described values. If this is not the case and if the limit value is not included in the range, this specification will specify it as such.

[0014] According to the present invention, different parameter ranges for a given step can be used individually or in combination. For example, a preferred range of tantalum content values ​​can be combined with a more preferred range of silica content values.

[0015] In the remainder of this specification, specific embodiments of the invention are described. According to the invention, these embodiments may be implemented individually or in combination with each other, without being limited to any particular combination, where technically feasible.

[0016] In the remainder of this specification, pressure is absolute pressure and is given in MPa absolute pressure (or MPa abs).

[0017] In the remainder of this specification, time and duration are expressed in hours (h), minutes (min), and / or seconds (sec).

[0018] According to the present invention, the terms “catalyst,” “heterogeneous catalyst,” and “supported catalyst” are used interchangeably and refer to any type of catalyst that comprises elemental tantalum and a support, and particularly a silica-based matrix.

[0019] In this specification, the terms "matrix" and "support" are used interchangeably to refer to a solid support for the catalyst. In the catalyst according to the invention, the support is based on silica.

[0020] In this specification, the terms “1,3-butadiene” and “butadiene” are used interchangeably and refer to one of the isomers of butadiene (a hydrocarbon compound having four carbon atoms and two double bonds) containing a double bond between carbon 1 and carbon 2 and a second double bond between carbon 3 and carbon 4, namely the 1,3 isomer of butadiene.

[0021] In this specification, the term "butadiene productivity" corresponds to the butadiene carbon productivity (generally expressed as % wt / wt per hour) of an apparatus for converting a feedstock containing ethanol into 1,3-butadiene, and specifically to the mass flow rate (in g / h) of butadiene per unit mass of Ta element measured at the outlet of the apparatus or reactor for a feedstock of 250 g / g Ta / h. Meanwhile, the term "butadiene selectivity" (expressed as % wt / wt) is carbon selectivity and corresponds to the flow rate of butadiene measured at the outlet of the apparatus or reactor relative to the sum of the flow rates of the carbon-based products formed (unconverted ethanol and any unconverted acetaldehyde are not considered in the calculation of selectivity).

[0022] The present invention thus relates to a heterogeneous catalyst comprising elemental tantalum and a silica-based matrix, and advantageously exhibiting a strength greater than or equal to 1000 au / g. Ta (Any unit of tantalum contained in the catalyst), preferably greater than or equal to 1100 au / g Ta The Lewis acidity content ([LAS]) is preferably less than or equal to 1900 au / g. Ta Very preferred is less than or equal to 1800 au / g Ta The catalyst has a Lewis acidity content ([LAS]). Advantageously, the catalyst has a low Brønsted acidity content, that is, a Lewis acidity content below a certain level. Specifically, the catalyst has a relative Lewis acidity content (%LAS) greater than or equal to 90%, preferably greater than or equal to 92%, which corresponds to the ratio between the Lewis acidity content and the total acidity content of the catalyst (i.e., the total number of acid sites, or the sum of Lewis acid and Brønsted acid sites).

[0023] The acidity of the catalyst, particularly Lewis acidity and Brønsted acidity, was determined by indirect analytical methods, and more particularly by Fourier transform infrared spectroscopy (FTIR) after pyridine adsorption and subsequent thermal desorption. This method is routinely used to characterize acidic solids such as zeolites, as described in the article Zholobenko et al., Journal of Catalysis, 385, 52 (2020). Prior to analysis, the catalyst was ground into powder form and then compacted into pellets, preferably 13 mm or 16 mm in diameter, particularly 13 mm. The pellets were then dried in an oven with an infrared (IR) cell under secondary vacuum (especially less than 10 °C). -5The sample was in-situ activated at 450°C for 10 hours under a pressure of millibars, and then the temperature was lowered to 150°C. Excess gaseous pyridine was introduced into an IR cell with a pyridine partial pressure greater than 1 millibar and contacted with the pellets for 10 minutes (adsorption phase). A thermal desorption phase was then performed at 150°C for 2 hours. The adsorption phase allows pyridine to react with the acid sites of the sample, while the thermal desorption step removes physi-adsorbed pyridine molecules (i.e., pyridine molecules that have not reacted with the acid sites; in other words, pyridine molecules that have no chemical bond with the acid sites of the analyzed catalyst) to retain only chemi-adsorbed pyridine molecules. After this thermal desorption phase, the sample was analyzed by Fourier transform infrared spectroscopy (FTIR) to obtain the IR spectrum of the sample; the IR spectrum corresponds to the sample's "thermal desorption spectrum".

[0024] Lewis acidity and Brønsted acidity were determined using thermal desorption spectroscopy, and their values ​​varied with the concentration of Lewis ([LAS]) and Brønsted ([BAS]) acid sites in the sample, respectively. For Lewis acidity ([LAS]), a wavelength of 1612 cm⁻¹ was used. -1 + / - 4 cm -1 The contribution area centered on the catalyst (corresponding to the υ8a mode of pyridine coordinated with Lewis acid sites on the catalyst surface) is better than that at 1450 cm⁻¹. -1 + / - 4 cm -1 The contribution area centered on this (which corresponds to the u19b mode of protonated pyridine) is considered, as the u19b mode of protonated pyridine may be affected by the residual presence of hydrogen-bonded pyridine. Therefore, the Lewis acidity content ([LAS]) of the sample (i.e., the analyzed catalyst) is determined by the area centered on the region between 1622 and 1593 cm⁻¹. -1 The signal area A in the wavenumber range between 1612 (i.e., the area under the IR spectrum) is integrated and then determined using the following calculations: Where [LAS]: Lewis acidity content of the analyzed sample (i.e., the catalyst), expressed in any unit per gram of tantalum contained in the catalyst (au / g). Ta The arbitrary unit mentioned here is proportional to the number of moles of Lewis acid sites in the analyzed sample (i.e., in the catalyst). A 1612 : 1612 cm -1 The absorbance of the center is expressed in cm⁻¹ as a percentage of the catalyst (i.e., per gram of the sample analyzed). -1 This indicates, and through the analysis of the values ​​between 1622 and 1593 cm -1 The signal area (i.e., the area under the IR spectrum) within the wavenumber range between the two values ​​is determined by integration. S: Surface area of ​​the pellets in the sample analyzed in transmission (in cm²) 2 (where S is the unit of measurement), that is, for a pellet with a diameter of 1.3 cm (i.e., 13 mm), S = π x (1.3 / 2)². [Ta]: The weight content of tantalum in the catalyst per unit weight of the catalyst (e.g., a tantalum content of 3% by weight in the catalyst corresponds to 0.03 g of tantalum per unit weight, i.e., per gram of catalyst).

[0025] Regarding the Brønsted acidity content ([BAS]), it was calculated using the υ19b mode corresponding to the protonated pyridine at the Brønsted acid sites on the catalyst surface at 1545 cm⁻¹. -1 + / - 4 cm -1 The Brønsted acidity content ([BAS]) of the sample (i.e., the analyzed catalyst) is determined by the area of ​​contribution centered at 1555 to 1532 cm⁻¹. -1 The wavenumber range between 1545 cm -1 + / - 4 cm -1 The signal area A centered on 1545 (i.e., the area under the IR spectrum) is integrated and then determined using the following calculations: Where [BAS]: Brønsted acidity of the analyzed sample (i.e., the catalyst), expressed in any unit per gram of tantalum contained in the catalyst (au / g). Ta The arbitrary unit mentioned here is proportional to the number of moles of Brønsted acid sites in the analyzed sample (i.e., in the catalyst). A 1545 : at 1545 cm -1 The absorbance of the center is expressed in cm⁻¹ as a percentage of the catalyst (i.e., per gram of the sample analyzed). -1 This indicates, and through the analysis of the values ​​between 1555 and 1532 cm -1 The signal area (i.e., the area under the IR spectrum) within the wavenumber range between the two values ​​is determined by integration. S: Surface area of ​​the pellets in the sample analyzed in transmission (in cm²) 2 (where S is the unit of measurement), that is, for a pellet with a diameter of 1.3 cm (i.e., 13 mm), S = π x (1.3 / 2)². [Ta]: The weight content of tantalum in the catalyst per unit weight of the catalyst (e.g., a tantalum content of 3% by weight in the catalyst corresponds to 0.03 g of tantalum per unit weight, i.e., per gram of catalyst).

[0026] The relative Lewis acidity content (%LAS) of the catalyst can then be calculated as follows: This is the ratio of the Lewis acidity content to the total acidity of the catalyst (i.e., the total number of acid sites, or the sum of Lewis acid and Brønsted acid sites). %LAS = 100 × [LAS] / ([LAS]+[BAS]) Where [LAS]: Lewis acidity content of the analyzed sample (i.e., the catalyst), expressed in any unit per gram of tantalum contained in the catalyst (au / g). Ta As detailed above, the measurements, and [BAS]: Brønsted acidity of the analyzed sample (i.e., the catalyst), expressed in arbitrary units per gram of tantalum contained in the catalyst (au / g). Ta As detailed above, the measurement was performed.

[0027] Advantageously, the catalyst according to the invention contains tantalum in an amount between 0.1% and 30% by weight, preferably between 0.3% and 10% by weight, and more preferably between 0.5% and 5% by weight, relative to the silica-based matrix. The catalyst may optionally contain at least one other metallic element (other than tantalum) selected from groups 3, 4, 5, 11, and 12 of the periodic table. Preferably, the catalyst according to the invention contains only elemental tantalum as a metallic element.

[0028] The silica-based matrix of the catalyst according to the invention preferably has a silica weight content of greater than or equal to 95% dry weight (i.e., between 95% and 100% dry weight), more preferably greater than or equal to 98% dry weight (i.e., between 98% and 100% dry weight), more preferably greater than or equal to 99.5% dry weight (i.e., between 99.5% and 100% dry weight), and more preferably greater than or equal to 99.9% dry weight (i.e., between 99.9% and 100% dry weight), relative to the total weight of the silica-based matrix in dry form (i.e., excluding the weight of any water that may be present in the matrix). The silica content is given herein as a percentage of the weight of silica (excluding water) relative to the total weight of the dry silica matrix (i.e., excluding the weight of any water that may be present in the matrix).

[0029] Advantageously, the silica-based matrix of the catalyst according to the invention comprises pores, particularly mesopores. Preferably, the catalyst according to the invention has an average pore size greater than or equal to 4 nm, preferably between 4.5 and 50 nm, and even more preferably between 4.5 and 20 nm. Preferably, the catalyst according to the invention has a pore volume greater than or equal to 0.47 ml / g, preferably between 0.47 and 1.8 ml / g, preferably between 0.58 and 1.5 ml / g, and more preferably between 0.8 and 1.5 ml / g. Preferably, the catalyst according to the invention has a pore volume greater than or equal to 100 m... 2 / g, preferably greater than or equal to 200 m 2 / g, preferably greater than or equal to 250m 2 / g, preferably 250 m 2 / g to 700 m 2 Specific surface area S between / g BET .

[0030] The aforementioned textural parameters were determined using an analytical technique called "nitrogen volumetry," which corresponds to the physical adsorption of nitrogen molecules into the pores of the material by gradually increasing pressure at a constant temperature. According to the invention, the specific surface area of ​​the tested material (particularly the catalyst) corresponds to the BET specific surface area (in m²). 2 S in g BET The BET specific surface area is based on the information in the journal " The Journal of the American Chemical Society The standard ASTM D 3663-78, established based on the Brunauer-Emmett-Teller method described in 1938, 60, 309, determines nitrogen adsorption. The pore distribution representing the mesoporous population is determined using the Barrett-Joyner-Halenda (BJH) model. The nitrogen adsorption-desorption isotherms obtained according to the BJH model are described in the journal article by EP Barrett, LG Joyner, and PP Halenda. The Journal of the American Chemical Society In the *Journal of the American Chemical Society*, 1951, 73, 373, the pore volume V is defined as the partial pressure P / P corresponding to the nitrogen adsorption-desorption isotherm. 0 最大 The observed volume values. Nitrogen adsorption volume is at P / P 0 最大= 0.99, the volume measured at this pressure assuming nitrogen has filled all pores. The mesopore diameter ϕ of the tested material, particularly the catalyst, is determined by formula 4000.V / S BET To determine.

[0031] The catalyst according to the invention can be in powder form or shaped, particularly in the form of granulated, crushed and sieved powder, beads, pellets, granules or extrusions (hollow or filled cylinders, multi-lobed cylinders with 2, 3, 4 or 5 lobes, such as twisted cylinders) or rings, etc. For example, the catalyst is optionally in the form of spherical extrusions or beads, preferably having a size between 0.5 and 10 mm, preferably between 1.0 and 5 mm. Thus, in addition to elemental tantalum and a silica-based matrix, the catalyst according to the invention can contain at least one porous oxide material that is advantageously inert relative to the reaction of converting a feedstock containing ethanol to butadiene and acts as a binder, thereby facilitating shaping and producing sufficient physical properties (mechanical strength, wear resistance, etc.) for the catalyst. The porous oxide material acting as a binder can be selected from silica, magnesium oxide, clay (such as kaolinite, chrysotile, montmorillonite, bedesulfurite, vermiculite, talc, hydropyrite, soapstone, lithium soapstone), titanium oxide, titanates (e.g., zinc, nickel, or cobalt titanates), lanthanum oxide, cerium oxide, boron phosphate, and mixtures thereof, and is preferably selected from silica and titanium oxide. Very preferably, the binder used has siliceous properties, and is preferably present in a content between 5% and 60% by weight, more preferably between 10% and 30% by weight, relative to the total weight of the catalyst.

[0032] The catalyst according to the present invention may preferably be: - Fresh catalyst, i.e., a catalyst that has been prepared but has not yet been used in a catalytic reactor or device, or - A reactivated catalyst, i.e. a spent catalyst that has undergone a reactivation process (particularly regenerated by burning coke in the presence of oxygen, and / or rejuvenated by means of a reactivating compound, optionally accompanied by the addition of tantalum, the reactivating compound being, for example, a hydroxy acid, keto acid, acidic polyacid, its ester, or a mixture thereof, or a monofunctional acid, hydroxy ketone, or diketone) in order to at least partially restore its catalytic performance level (i.e. a catalyst already used in a reaction section for converting a feedstock containing ethanol into butadiene).

[0033] Optionally, the catalyst may be: - Used catalyst, i.e., the catalyst that has already been used in the reaction section used to convert feedstock containing ethanol into butadiene. - Aged catalysts, i.e., catalysts that have been treated, such as by heat treatment, especially those heat-treated under humid gas streams.

[0034] Such a catalyst is highly advantageous in enabling optimization of catalytic performance levels during the conversion of ethanol-containing feedstocks to 1,3-butadiene, particularly in terms of butadiene selectivity and butadiene productivity. Thus, the catalyst according to the invention for converting ethanol-containing feedstocks, especially ethanol-acetaldehyde feedstocks, to 1,3-butadiene enables high butadiene selectivity, particularly for 40% by weight of feedstock, with a conversion rate greater than or equal to 70%, preferably greater than or equal to 72% (conversion rate is the weight conversion of the feedstock and corresponds to the difference between the weight flow rate of the feedstock at the inlet and the weight flow rate of the feedstock at the outlet relative to the weight flow rate of the feedstock at the inlet), and satisfactory butadiene productivity, particularly for feedstocks with a gravity space velocity (gravity space velocity or WWH is expressed as the weight of tantalum per unit weight and the weight of feedstock per hour contained in the catalyst used (i.e., the total weight of the catalyst used) greater than or equal to 30 g / g Ta / h, preferably greater than or equal to 32 g / g Ta / h.

[0035] The present invention also relates to the use of the catalyst according to the invention for converting a feedstock comprising ethanol, and according to one specific embodiment, a mixture of ethanol and acetaldehyde, into 1,3-butadiene. The operating conditions for the conversion reaction are preferably a temperature between 250 and 450°C, more preferably between 270 and 380°C, more preferably between 300 and 360°C; a pressure between 0.05 and 2.00 MPa, more preferably between 0.05 and 1.50 MPa, more preferably between 0.08 and 1.00 MPa; and preferably 0.2 to 10 h. -1 Between, preferably 0.5 to 5 h -1 Between and preferably 1 to 4 hours -1 The space velocity is defined as the ratio between the mass flow rate of the feedstock and the mass of the catalyst. When the feedstock also contains acetaldehyde, the ethanol / acetaldehyde molar ratio is between 1 and 5, preferably between 2 and 4. The catalyst according to the invention, when used to convert an ethanol-containing feedstock to butadiene, subsequently shows optimized butadiene selectivity and butadiene carbon productivity.

[0036] The following examples illustrate the present invention, and in particular, specific embodiments thereof, but do not limit its scope. Example

[0037] Example 1: Preparation of tantalum-based catalysts on silica supports Catalysts containing 2.5% or 3% tantalum on silica beads (also known as silica supports) are prepared, where the percentage of tantalum is given by the weight of tantalum element relative to the weight of silica beads.

[0038] The preparation methods for each catalyst are as follows: Before impregnation, the silica support is oven-dried at 100°C or 250°C for 2 hours.

[0039] Introducing tantalum precursors—pentaethoxytantalum (Ta(OEt)5) or tetraethoxyacetylacetonetantalum (Ta(AcAc)(OEt)4)—and in a certain solvent volume V 溶剂 The solvent is ethanol, ethanol hydrochloric acid solution (ethanol containing 1.25 M HCl, where M refers to moles, i.e., mol / L), or a 70 / 30 weight / weight mixture of ethanol and acetic acid.

[0040] The organic solution was then homogenized by stirring.

[0041] The obtained organic solution was rapidly added dropwise and mixed with the silica support until wetting of the support surface was observed (dry impregnation). The solid was then placed in an ethanol-saturated atmosphere for 3 hours. The solid was then dried in an oven at 100°C for 24 hours, followed by calcination in air at 550°C for 4 hours to obtain the catalyst.

[0042] The prepared catalyst, its preparation parameters, and textural characteristics, particularly the average pore size Dp, pore volume Vp, and specific surface area S measured by an analytical technique known as the "nitrogen capacity determination method" as described above in the specification. BET Presented in Table 1. The content or purity of the SiO2 matrix (or support) (excluding elemental tan) was determined by multi-element detection via ICP (inductively coupled plasma) spectroscopy; it is given as a weight percentage of silica relative to the total weight of the dry support (i.e., excluding water).

[0043] [Table 1] Catalyst F is prepared from a silica support that is different from the silica support used to prepare catalysts A to E.

[0044] The catalyst, prepared as catalyst D, was used to convert a feedstock containing ethanol and acetaldehyde at an ethanol / acetaldehyde molar ratio of 2.6 to butadiene at a temperature of 350 °C and a pressure of 0.15 MPa. After several hours, the feedstock supply was stopped (and the reaction was thus stopped), and the catalyst was subsequently subjected to a decoking step (regeneration stage) via controlled combustion. The recovered catalyst was the spent catalyst: catalyst G. A portion of the spent catalyst (catalyst G) was then reactivated by contacting it with a rejuvenation solution at ambient temperature and atmospheric pressure. The rejuvenation solution contained lactic acid from ethanol and tantalum pentaethoxy (Ta(OEt)5), such that the amount of lactic acid in the rejuvenation solution corresponded to a molar ratio equal to 15 between lactic acid in the rejuvenation solution and tantalum present on the spent catalyst, and the amount of tantalum pentaethoxy in the rejuvenation solution corresponded to an additional tantalum content of 1% by weight relative to the weight of the spent catalyst. The volume of the liquid rejuvenation solution used was proportional to the pore volume of the spent catalyst and was added dropwise to the spent catalyst at ambient temperature and atmospheric pressure until wetting of the latter's surface was observed (dry impregnation). The solid was then allowed to mature for 0.5 to 2 hours. The solid was dried at 100°C and then, finally, heat-treated with a humid air stream (20 vol%) at up to 250°C at a gas flow rate of 2.5 NL / h. The resulting catalyst was catalyst H.

[0045] Example 2: Measurement of catalyst acidity Sample preparation and IR measurement The acidity of the catalyst prepared as described in Example 1 was measured by adsorption of pyridine followed by thermal desorption and then by Fourier transform infrared (FTIR) spectroscopy. This method is conventionally used to characterize acidic solids such as zeolites, as described in the journal Zholobenko et al., Journal of Catalysis, 385, 52 (2020).

[0046] For each catalyst, the catalyst sample was ground to obtain powder, which was then compacted into pellets with a diameter of 13 mm. These pellets were then placed in an IR measurement cell and subjected to a secondary vacuum (<10⁻⁶ Ω·cm). -5 The cells were activated in situ at 450°C for 10 hours at a temperature of 100 mg / L. The temperature was then lowered to 150°C.

[0047] When the temperature reached 150°C, excess gaseous pyridine was introduced into the IR cell to achieve a pyridine partial pressure greater than 1 mbar, and it was brought into contact with the pellets for 10 minutes (adsorption stage). A thermal desorption step was then performed at 150°C for 2 hours. FTIR measurements were then performed, and the IR spectra of the samples were recorded.

[0048] Data Analysis For each catalyst tested, the Lewis and Brønsted acidity contents of the sample were determined using IR spectroscopy, which were [LAS] and [BAS], respectively.

[0049] More specifically, the Lewis acidity content ([LAS], expressed in au / g) of the sample was also measured. Ta (Unit: 1622-1593 cm) -1 Area A in the IR spectrum within the wavenumber range 1612 Integrate and then use the following calculations to determine: Where S: the surface area of ​​the pellets in the sample analyzed in transmission (in cm²). 2 (In units of measurement), a pellet with a diameter of 13 mm: S is approximately equal to 1.327 cm. 2 , [Ta]: The weight content of tantalum in the catalyst per unit weight of the catalyst, i.e. 0.03 g for catalysts A to D, F and G, 0.025 g for catalyst E and 0.04 g for catalyst H.

[0050] Brønsted acidity ([BAS], in au / g) of the sample Ta (in units) By analyzing the values ​​between 1555 and 1532 cm -1 Area A in the IR spectrum within the wavenumber range 1545 Integrate and then use the following calculations to determine: Where S: the surface area of ​​the pellets in the sample analyzed in transmission (in cm²). 2 (In units of measurement), a pellet with a diameter of 13 mm: S is approximately equal to 1.327 cm. 2 , [Ta]: The weight content of tantalum in the catalyst per unit weight of the catalyst, i.e. 0.03 g for catalysts A to D, F and G, 0.025 g for catalyst E and 0.04 g for catalyst H.

[0051] The relative Lewis acidity (%LAS) of the catalyst was also calculated for each test catalyst as follows: %LAS = 100 × [LAS] / ([LAS]+[BAS]). Table 2 summarizes the results obtained for each catalyst in each test. Table 2 also categorizes the tested catalysts according to whether they are based on the present invention.

[0052] [Table 2]

[0053] Example 3: Catalyst Performance Testing The reactor used consisted of stainless steel tubes 20 cm in length and 10 mm in diameter. Silicon carbide was first added to the reactor, followed by a catalyst diluted in the silicon carbide, and finally, silicon carbide was added again. The silicon carbide was inert relative to the feedstock and did not affect the catalytic results. The reactor temperature was controlled using a tubular furnace with three heating zones.

[0054] The catalyst was calcined in situ at 550°C for 4 hours in dry air, and then placed under nitrogen at the test temperature for 1 hour.

[0055] A liquid feedstock (a mixture of ethanol and acetaldehyde, with an ethanol / acetaldehyde molar ratio of 2.6 mol / mol) was injected into the catalytic system using a dual-piston HPLC pump. The liquid feedstock was vaporized and homogenized by passing it through a static mixer before entering the reactor. For each test, the ethanol / acetaldehyde ratio was set to 2.6 mol / mol, the reaction temperature to 350 °C, and the pressure to 0.15 MPa.

[0056] At the reactor outlet, the products formed during the reaction are retained in the gas phase for online analysis by gas chromatography (PONA capillary column), allowing identification of the formed products.

[0057] For each catalyst tested, at the same feed flow rate (constant WWH of 250 g / g Ta / h, i.e., 7.5 h),... -1 Carbon productivity is measured at a space velocity (WH), while butadiene selectivity is measured at an equivalent conversion rate (40% feed conversion). Carbon productivity (usually expressed as % wt / wt / h) corresponds to the mass flow rate (in g / h) of butadiene at the reactor outlet for a feedstock of 250 g / g Ta / h WWH, per unit mass of elemental Ta. The measured butadiene selectivity (expressed as % wt / wt) is the carbon selectivity and corresponds to the flow rate of butadiene at the reactor outlet, calculated as the sum of the flow rates of the carbon-based products formed (excluding unconverted ethanol and ethanol in the selectivity calculation).

[0058] The catalytic results are presented in Table 3 and compared with the thresholds for selectivity (greater than or equal to 70, preferably greater than or equal to 72) and productivity (greater than or equal to 30, preferably greater than or equal to 32). Table 3 also shows the Lewis acidity content ([LAS]) of each catalyst as determined according to Example 2 (in au / g). Ta (in units) and relative Lewis acidity content (%LAS).

[0059] [Table 3]

[0060] Catalysts B, C, D, E, and H according to the invention—which are tantalum and silica-based catalysts—contain 2.5 wt%, 3 wt%, or 4 wt% tantalum relative to the silica support, and have a strength of at least 1000 au / g as measured by FTIR after pyridine adsorption and thermal desorption. Ta The Lewis acidity content exhibits satisfactory butadiene selectivity and butadiene productivity. In particular, catalysts B, C, D, E, and H (which are according to the invention) for converting ethanol-acetaldehyde feedstock to butadiene at 350°C enable butadiene selectivity greater than or equal to 72% (at 40% conversion) and butadiene productivity greater than 32 g / g Ta / h (at a feedstock weight hourly space velocity of 250 g / g Ta / h).

[0061] Conversely, catalysts A, F, and G not according to the invention (which have less than 1000 au / g as measured by FTIR after pyridine adsorption and thermal desorption) Ta The Lewis acidity content indicates poor catalytic performance. Specifically, catalysts A and G (not according to the invention) for converting ethanol-acetaldehyde feedstock to butadiene at 350 °C exhibit butadiene selectivity of less than 70% (at 40% conversion) and butadiene productivity of less than 30 g / g Ta / h (at a feedstock weight hourly space velocity of 250 g / g Ta / h). Regarding catalyst F (not according to the invention), even when used under the same conditions to convert ethanol-acetaldehyde feedstock to butadiene to achieve a butadiene selectivity of 70% (at 40% conversion), the productivity obtained with catalyst F is still far below 30 g / g Ta / h (for a feedstock weight hourly space velocity of 250 g / g Ta / h).

Claims

1. A catalyst comprising tantalum and a silica-based matrix, said catalyst having a tantalum content between 0.1% by weight and 30% by weight relative to the silica-based matrix, said catalyst having a tantalum content greater than or equal to 1000 au / g Ta Lewis acidity content [LAS], The Lewis acidity (LAS) content is determined by the ratio of 1622 to 1593 cm⁻¹. -1 Area A in the IR spectrum within the wavenumber range 1612 Integration was performed and the following calculations were used to determine the IR spectrum obtained by Fourier transform infrared spectroscopy (FTIR) of a sample of the catalyst milled into powder and subsequently pelletized, following adsorption of pyridine at 150 °C and subsequent thermal desorption: Wherein [LAS] refers to the Lewis acidity content of the catalyst, expressed in any unit per gram of tantalum (au / g). Ta A 1612 Corresponding to 1612 cm -1 The absorbance contributed by the center, expressed in cm⁻¹ per gram of catalyst. -1 This indicates, and through the analysis of the values ​​between 1622 and 1593 cm -1 The area under the IR spectrum within the wavenumber range between the two values ​​is integrated to determine S; S corresponds to the surface area of ​​the sample pellet (in cm⁻¹). 2 [Ta] is the unit of measurement, and [Ta] corresponds to the weight content of tantalum in the catalyst per unit weight of the catalyst.

2. The catalyst according to claim 1, having a concentration of less than or equal to 1900 au / g Ta Very preferred is less than or equal to 1800 au / g Ta Lewis acidity content [LAS].

3. The catalyst according to claim 1 or 2, having a tantalum content of elemental tantalum of between 0.3% and 10% by weight, preferably between 0.5% and 5% by weight, relative to the silica-based matrix.

4. The catalyst according to any one of the preceding claims, wherein the silica-based matrix has a silica weight content of greater than or equal to 95 dry weight%, preferably greater than or equal to 98 dry weight%, preferably greater than or equal to 99.5 dry weight%, and more preferably greater than or equal to 99.9 weight% relative to the total weight of the silica-based matrix in dry form.

5. The catalyst according to any one of the preceding claims has a relative Lewis acidity content of 90% or more, preferably 92% or more, expressed as %LAS, which corresponds to the ratio of the Lewis acidity content to the total acidity content of the catalyst. Total acidity is the sum of Lewis acidity and Brønsted acidity. The Brønsted acidity content [BAS] was determined by measuring the Brønsted acidity at 1555 to 1532 cm⁻¹. -1 Area A in the IR spectrum within the wavenumber range 1545 Integrate and use the following calculations to determine: Wherein [BAS] refers to the Brønsted acidity content of the catalyst, expressed in any unit per gram of tantalum (au / g). Ta A 1545 Corresponding to 1545 cm -1 The absorbance contributed by the center, expressed in cm⁻¹ per gram of catalyst. -1 This indicates, and through the analysis of the values ​​between 1555 and 1532 cm -1 The area under the IR spectrum within the wavenumber range between the two values ​​is integrated to determine S; S corresponds to the surface area of ​​the sample pellet (in cm⁻¹). 2 [Ta] is the unit of measurement, and [Ta] corresponds to the weight content of tantalum in the catalyst per unit weight of the catalyst.

6. The catalyst according to any one of the preceding claims has an average pore size greater than or equal to 4 nm, preferably between 4.5 and 50 nm, and even more preferably between 4.5 and 20 nm.

7. The catalyst according to any one of the preceding claims has a pore volume greater than or equal to 0.47 ml / g, preferably between 0.47 and 1.8 ml / g, preferably between 0.58 and 1.5 ml / g, and preferably between 0.8 and 1.5 ml / g.

8. The catalyst according to any one of the preceding claims, having a concentration of 100 m 2 / g, preferably greater than or equal to 200m 2 / g, preferably greater than or equal to 250 m 2 / g, preferably 250 m 2 / g to 700 m 2 Specific surface area S between / g BET .

9. The catalyst according to any one of claims 1 to 8 is used for converting a feedstock containing ethanol into butadiene at a temperature between 250 and 450°C and a pressure between 0.05 and 2.00 MPa.

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