Method for producing aliphatic aldehydes

Abstract

The present invention relates to a method for producing aliphatic aldehydes from syngas, a ruthenium catalyst being used in the process.

Description

[0001] DESCRIPTION

[0002] Procedure for the production of aliphatic aldehydes

[0003] FIELD OF INVENTION

[0004] The present invention relates to a process for producing aliphatic aldehydes by contacting synthesis gas with a catalyst in a solvent in a reactor. The invention also relates to a catalyst for such a process.

[0005] BACKGROUND

[0006] Aliphatic aldehydes of general formula RCHO, where R is an alkyl group, are chemical compounds that find applications as intermediates in the production of surfactants and pharmaceutical compounds, in the manufacture of synthetic fragrances and flavors, as polymerization initiators and crosslinking agents in the manufacture of polymers, or as precursors to other alkyl compounds, such as alcohols and carboxylic acids, among other applications. The term 'fatty aldehydes' is commonly used to refer to aliphatic aldehydes where the alkyl group R contains between about 6 and 29 carbon atoms, i.e., they have a hydrocarbon backbone C n , where n is between approximately 7 and 30 carbon atoms. Linear aliphatic aldehydes with alkyl chains C nof between 8 and 16 carbons, i.e. Cs-ie, such as octanal, nonanal (pelargonic aldehyde), decanal (capric aldehyde), lauryl aldehyde (dodecanal), myristaldehyde (tetradecanal) or palmitaldehyde (hexadecanal), are particularly valuable as ingredients in synthetic fragrances and flavours, among other applications.

[0007] Methods known in the art for the synthesis of aliphatic aldehydes include the selective dehydrogenation of aliphatic alcohols. US5155279A describes a method for the preparation of an aldehyde that involves reacting the corresponding alkane with a solubilized stable free radical nitroxide as an oxidant. WO2019232715A1 presents a catalyst system for the oxidation of alcohols to aldehydes or ketones using molecular oxygen as the terminal oxidant. “An Overview of Selective Oxidation of Alcohols: Catalysts, Oxidants and Reaction Mechanisms.” Catal. Surv. Asia 20, 13–22 (2016) provides a review of catalytic procedures for the dehydrogenation of alcohols to aldehydes. An alternative procedure for the synthesis of aliphatic aldehydes is the hydroformylation of aliphatic alkenes.Hydroformylation, also known as the “oxo” process, involves the reaction of an alkene with synthesis gas, which is a gaseous mixture comprising carbon monoxide (CO) and hydrogen (H2), in the presence of a catalyst, adding a formyl group (-CHO) to the initial alkene reactant to form an aldehyde derivative. The paper “Hydroformylation: Fundamentals, Processes, and Applications in Organic Synthesis”, edited by Armin Borner and Robert Franke in 2016, ISBN: 9783527335527, provides a review of catalysts and methods for the hydroformylation of alkenes to produce aldehydes. While rhodium (Rh) is a common active metal in molecular catalysts for the hydroformylation of alkenes, the paper by R. Kumar and S.H.Chikkali, “Hydroformylation of olefins by metals other than rhodium,” Journal of Organometallic Chemistry, Volume 960, 2022, 122231, provides a review of procedures for the hydroformylation of alkenes using catalysts based on other metals. CN106824282B describes a method for the isomerization of long-chain internal alkenes and a homogeneous catalytic hydroformylation reaction using rhodium-ruthenium coordination complexes stabilized by phosphine-type ligands as catalysts.

[0008] Another procedure for the preparation of aliphatic aldehydes is the ozonolysis of aliphatic alkenes, as described for example in TJ Fisher, PH Dussault, “Alkene ozonolysis”, Tetrahedron, Volume 73-30, 2017, pages 4233-4258.

[0009] Common to the above procedures for the preparation of aldehydes is that the alkyl hydrocarbon skeleton in the final aldehyde product must be provided in the form of a constituent part (synthon) of a reactive compound, e.g., an alcohol, a nitrile, etc. In the case of hydroformylation methods of alkenes, the alkyl chain C n -i of an alkene reactant extends by a carbon atom to form an aldehyde product C n . Therefore, although these procedures are effective in selectively producing aliphatic aldehydes, they require the supply of a C group n or C n-i , preformed, as part of one of the reactants for the process. This reactant must be produced in another previous process, or isolated from natural sources. Therefore, it is desirable to develop methods for the selective production of aliphatic aldehydes in which monocarbon compounds (Ci), more versatile and cost-effective, are fed as the only precursors for the main hydrocarbon structure in the produced aliphatic aldehydes. Synthesis gas, commonly abbreviated as "syngas" is a mixture composed of carbon monoxide (CO), hydrogen (H2) and, in some cases, carbon dioxide (CO2) as main components. Synthesis gas streams may also comprise other gases such as nitrogen (N2), helium (He), argon (Ar), water vapor (H2O) or light hydrocarbons such as methane (CH4), ethane (C2H6), propane (CsHs), which do not significantly alter the reactivity of the main components.Synthesis gas can be obtained from a wide range of carbonaceous sources, for example, by steam reforming or partial oxidation of natural gas or shale gas, coal gasification, biomass gasification and / or reforming, carbon dioxide hydrogenation or CO2 and water coelectrolysis, among others, and is therefore considered a very versatile C1 precursor for the production of chemicals from a wide range of alternative feedstocks to petroleum. Fischer–Tropsch synthesis is a catalytic reaction through which synthesis gas is directly converted into a mixture of synthetic aliphatic hydrocarbons, mainly n-paraffins (Fischer-Tropsch Synthesis, Catalysts, and Catalysis: Advances and Applications; B.H. Davis, M.L. Occelli (Eds), CRC Press (2016), ISBN 978-1466555297).Under certain reaction conditions, the products of Fischer-Tropsch synthesis may also contain oxygenated organic compounds such as aldehydes, alcohols, or carboxylic acids. However, aldehydes, in particular, are generally obtained only as minor byproducts, with selectivities of less than 5%.

[0010] E. Durham, et al. “Diesel-length aldehydes and ketones via supercritical Fischer Tropsch Synthesis on an iron catalyst”, Applied Catalysis A: General, Volume 386, 1-2, 2010, pp. 65-73, and E. Durham, et al. “Supercritical Fischer-Tropsch Synthesis: Heavy Aldehyde Production and the Role of Process Conditions”, Industrial & Engineering Chemistry Research 2014 53 (23), 9695-9702, document the production of aldehydes, with a selectivity of up to 30% (on a carbon basis), along with major hydrocarbon products (alkanes and alkenes), in a synthesis gas (syngas) conversion method over a solid iron (Fe) catalyst containing additionally copper (Cu) and potassium (K). In this method, synthesis gas and n-hexane are fed to a fixed-bed reactor containing the solid catalyst, and the process is carried out at a temperature of 240°C and a total pressure that generates supercritical conditions for n-hexane.

[0011] A first objective of the present invention is to provide a process for producing aliphatic aldehydes by converting synthesis gas using a ruthenium catalyst.

[0012] The present invention relates to a process for the production of aliphatic aldehydes, which can be implemented by at least the following steps:

[0013] (i) supplying a reactor with a. a synthesis gas feed, and b. a solvent

[0014] (i) reacting the synthesis gas supplied in step (i) by contacting it with a catalyst comprising ruthenium (Ru), at a reaction temperature of between 373 and 523 degrees Kelvin and at a total pressure of between 0.1 MPa and 30 MPa, where 1 MPa (megapascal) is equivalent to 10 6 Pa; iii) recovering the aliphatic aldehydes from the reaction products of step (i).

[0015] The term "conversion", as used in the context of the present invention, is expressed as a percentage and is understood as the fraction of CO X (x=1 or 2), in the synthesis gas feed which is converted in the reactor to other carbon-containing compounds.

[0016] The term "selectivity", as used in the context of the present invention, is defined on a carbon basis and is therefore understood to mean the ratio of the total molar amount of carbon in the products of interest, for example aliphatic aldehydes, to the total molar amount of carbon in all reaction products, and is expressed on a percentage basis.

[0017] The terms "process" and "method" as used interchangeably in the context of the present invention are defined as the set of technical operations that involve the development of at least one chemical reaction, and that results in the deliberate modification of at least one chemical compound, which is part of a feed to the process, into at least one different chemical product.

[0018] Procedure

[0019] The types of reactors that are suitable for implementing the process of the invention are those that allow contacting of gas and liquid phases with a solid catalyst. In one embodiment of the invention, the reactor operates in a continuous mode, whereby at least one gas feed stream and one liquid feed stream are continuously provided to the reactor inlet, such as a bubble column slurry reactor or a trickle bed reactor, and a product stream is continuously removed at the reactor outlet. In another embodiment of the invention, the reactor operates in a batch mode, whereby the gas phase reactants and liquid phase feeds and the catalyst are introduced into the reactor before the reactor temperature is adjusted to the reaction temperature, the reaction proceeding without additional streams being provided to the reactor inlet during the reaction.After a certain reaction time, the reaction is terminated by lowering the reactor temperature below the temperature range for the inventive process, and at least one product stream is collected from the reactor outlet. In another embodiment of the invention, the reactor is operated in a semi-continuous mode, whereby the gas-phase reactants and liquid feeds and the catalyst are introduced into the reactor before the reactor temperature is adjusted to the reaction temperature, the reaction proceeding under the continuous provision of a gas feed stream, for example, synthesis gas, at the reactor inlet. The reaction is terminated after a certain reaction time by lowering the reactor temperature below the temperature range for the inventive process, and at least one product stream is collected from the reactor outlet.

[0020] In accordance with the present invention, the H2:CO molar ratio in the synthesis gas feed may be in the range of 0.1 to 5.0. In a preferred embodiment of the present invention, said H2:CO molar ratio in the synthesis gas is in the range of 0.3 to 3.0. More preferably, the H2:CO molar ratio in the synthesis gas is in the range of 0.5 to 2.0.

[0021] According to the present invention, the synthesis gas feed may comprise CO2. The molar ratio of CÜ2:CO in the synthesis gas feed may be in the range of 0 to 2.0. In a preferred embodiment of the present invention, said molar ratio of CÜ2:CO in the synthesis gas is in the range of 0 to 0.5. More preferably, the molar ratio of CÜ2:CO in the synthesis gas is in the range of 0 to 0.1.

[0022] The synthesis gas feed may further comprise other compounds that do not interfere with the synthesis gas conversion, such as nitrogen, helium, argon, water, C1-C4 alkanes (alkanes comprising between 1 and 4 carbon atoms), or combinations thereof. The solvent provided in step (i) provides improved temperature control and a means to solubilize compounds in the reactor. Such compounds comprise synthesis gas conversion reaction products, ligands, catalyst metal species, or any combination thereof. Such solvent may be selected from the list of aliphatic hydrocarbons, aromatic hydrocarbons, oxygenated organic compounds, water, nitrogen-containing organic compounds, halogenated organic compounds, liquid organic salts, and combinations thereof.More specifically, the aliphatic hydrocarbon solvents may be selected from the non-limiting list consisting of n-hexane, n-decane, n-dodecane, n-hexadecane, / so-pentane (2-methylbutane), / so-hexane (2-methylpentane), / so-octane (2,2,4-trimethylpentane), and 2,6,11,15-tetramethylhexadecane. Again more specifically, the aromatic hydrocarbon solvents may be selected from the non-limiting list consisting of benzene, toluene, xylene, trimethylbenzenes, and naphthalene. Again more specifically, the oxygenated organic compound solvents may be selected from the non-limiting list consisting of methanol, ethanol, isopropanol, n-butanol, n-hexanol, 1,4-dioxane, dimethylformamide, tetrahydrofuran, di-n-butyl ether, cyclohexanone, methyl isobutyl ketone, ethylene glycol, propylene glycol, cyclopropylcarbonate, glycerol and ethyl acetate.Again more specifically, the nitrogen-containing organic compound solvents may be selected from the non-limiting list consisting of acetonitrile, benzonitrile, N,N-dimethylaniline, N-methylmorpholine, N-methylpiperidine, N-methylpyrrole, and quinoline. Again more specifically, the halogenated organic compound solvents may be selected from the non-limiting list consisting of methylene chloride, chloroform, 1,2-dichloroethane, perfluoropentane, perfluorohexane, perfluorotoluene, monofluorobenzene, and perfluorobenzene. Again more specifically, the liquid organic salt solvents are selected from the non-limiting list consisting of salts comprising organic cations of the imidazolium, pyridinium, 1,2,3-triazolium, morpholinium, piperidino, pyrrolidinium, pyrazolium, ammonium, and phosphonium types associated with anions of the PF type. 6 ', BF 4 ', NTf 2' (bis(trifluoromethylsulfonyl)amide), OTf (trifluoromethylsulfonate), DCA' (dicyanamide), acetate and CHsSOs'. In another particular embodiment of the invention, the solvent comprises aliphatic aldehydes of the type produced in the reaction step of the process of the invention.

[0023] In accordance with the present invention, the process is carried out at a reaction temperature in the range of 373 Kelvin (K) to 523 K. The reaction temperature, as used in the context of the present invention, is understood as the maximum temperature in the reactor measured by means of a K type thermocouple located within a stainless steel sheath and in contact with the liquid phase. In a preferred embodiment of the present invention, the process is carried out at a reaction temperature in the range of 393 K to 453 K. More preferably, the process is carried out at a reaction temperature in the range of 413 K to 433 K.

[0024] Suitable operating pressures for the process of the invention are between about 0.1 MPa and 30 MPa. In a preferred embodiment of the present invention, the process is carried out at a pressure between 1 MPa and 20 MPa. In an even more preferred embodiment of the present invention, the process is carried out at a reaction pressure between 4 MPa and 10 MPa.

[0025] In the process of the invention, the distribution of aliphatic aldehyde products may obey the so-called Anderson-Schulz-Flory (ASF) chain length distribution, which is typically observed for reactions proceeding via a chain growth polymerization mechanism from Ci units. This product distribution is mathematically described by the following relationship (Eq. 1):

[0026] W n = n ■ (1 - a) 2 ■ a n-1 (Equation 1) in which W nis the mass fraction of aliphatic aldehyde products (RCHO) for which the hydrocarbon chain R contains n carbon atoms, and a (alpha) represents the chain growth probability factor, which represents the probability, on a 0 to 1 basis, that in the polymerization process a monomeric species Ci will be added to a hydrocarbon chain, causing the latter to grow by one carbon atom. Experimentally, the chain growth probability (alpha) can be determined according to the relation a=e m , where e is the Euler number and m represents the slope obtained for the mathematical function of linear regression of the data in a graph representing Ln(W n / n) versus an over a sufficiently wide range of carbon chain lengths n, where Ln represents the natural logarithmic function.

[0027] Typically, the product mixture of the inventive process is fractionated to recover aldehyde products. Recovery of aldehyde products from mixtures with other reaction products, for example, paraffins, can be carried out by known methods such as distillation, liquid-liquid extraction, selective adsorption, or reactive derivatization of aldehydes to other derived compounds, such as hydrazones, oximes, or organoborated compounds, followed by any of the foregoing methods. Preferably, the process of the present invention produces linear aliphatic aldehydes with a hydrocarbon chain length of between 8 and 16 carbon atoms. In a particular embodiment of the invention, the compounds present in the reactor effluent stream, such as unconverted reactants, solvent, reaction products, or a combination thereof, are recovered and recycled to the reactor.

[0028] Catalyst

[0029] According to the present invention, the catalyst is a solid. In a particular embodiment of the invention, the catalyst is a supported metal catalyst. The concept of "supported metal catalyst" is understood in the art as a catalyst composition comprising, on the one hand, a metallic portion, dispersed in the form of particles with an average diameter typically less than 100 nm, which is generally catalytically active, or can be converted into an active phase in situ, before or during use of the catalyst, and, on the other hand, a non-metallic portion, the carrier material or support, which is generally porous and forms the majority of the catalyst by mass.

[0030] Several processes are known in the art for incorporating a metallic component into a support material. These processes include preparation techniques such as impregnation, deposition precipitation, ion exchange, electrochemical deposition, electrostatic adsorption, melt infiltration, and coprecipitation. References to existing processes for incorporating a metallic component into a support material are provided in "Handbook of Heterogeneous Catalysis", G. Ertl, H. Knózinger, F. Schüth, J. Weitkamp (Eds.); Volume 1, Wiley-VCH Verlag GmbH & Co. Weinheim, 2008, and "Synthesis of solid catalysts", K. P. de Jong (Ed.); Wiley-VCH Verlag GmbH & Co. Weinheim, 2009.

[0031] According to the present invention, the solid catalyst comprises ruthenium (Ru) as the active metal. According to a preferred embodiment of the invention, Ru represents between 50% and 100% of the metallic portion. More preferably, Ru represents between 80% and 100% of the metallic portion.

[0032] The support material must be chemically stable under the reaction conditions encountered in a synthesis gas conversion process. Said support may be an oxide selected from the porous oxide supports that are used as support materials for supported metal catalysts in the art, and which may comprise, among others, SiO2, transition forms of Al2O3, α-AfeOs, TiO2, ZrO2, carbide or oxycarbide material such as SiC, SiO x C y, with x in the range of 0 <x<2 e y en el rango de 0<y<1 , carbono y cualquier combinación de los mismos. Por formas de transición de AI2O3 se entienden polimorfos metaestables de óxido de aluminio (III) que pueden obtenerse a temperaturas intermedias durante la transformación de hidróxidos y oxohidróxidos de aluminio a la fase termodinámicamente más estable, esto es alfa-ALOs (a-ALOs). Dichas formas de transición de AI2O3 comprenden chi-ALOs, kappa-ALOs, gamma-ALOs, delta-ALOs, theta-ALOs, eta-ALOs, rho-ALOs, y combinaciones de las mismas.

[0033] Preferably, the weight loading of the metal, preferably Ru, defined as the weight fraction of the total catalyst that corresponds to the metal, preferably Ru, in said catalyst, is in the range of 0.5-50% by weight, and more preferably in the range of 3-20% by weight.

[0034] The metals are incorporated onto the support material using metal precursor compounds such as inorganic and organic metal salts, metal clusters, and organometallic complexes. Examples of ruthenium-containing precursors are ruthenium acetylacetonate, ruthenium chloride, ruthenium nitrosyl nitrate, ammonium hexachlororuthenate, triruthenium dodecacarbonyl, bis(cyclopentadienyl)ruthenium(II), and the like. The ruthenium precursors can provide ruthenium in a zero oxidation state, oxidation state II, oxidation state III, oxidation state IV, oxidation state VI, or a combination thereof. According to a preferred embodiment of the invention, the catalyst is prepared using ruthenium nitrosyl nitrate as the ruthenium precursor.Typically, after the metal precursor has been incorporated, a heat treatment is applied under a gas atmosphere, either sealed or flowing, of air, water vapor, an inert gas such as nitrogen, helium, argon, or combinations thereof, to decompose the metal precursor into an oxide or suboxide form on the surface of the support material.

[0035] In another particular embodiment of the invention, the catalyst is an unsupported (bulk) metal catalyst, such as a fine divided metal powder, a metal gauze or a metal foam.

[0036] In a particular embodiment of the invention, the catalyst comprises, in addition to Ru, also a second metal (M2) selected from the list of rhodium (Rh), cobalt (Co), iridium (Ir), and any combination thereof. In a preferred embodiment, the catalyst comprises, in addition to Ru, also rhodium (Rh). The content of the second metal M2, expressed as the molar ratio M2:Ru is preferably between 0.001 and 1, more preferably between 0.001 and 0.5 and even more preferably between 0.001 and 0.2.

[0037] It is common in the art for supported metal catalysts to comprise so-called promoters, in addition to the primary active metal and the support material in the case of supported catalysts. In general, a promoter is a substance that improves catalyst performance in terms of activity, selectivity to a desired product or product fraction, e.g., aliphatic aldehydes in the present invention, stability under operating conditions, or a combination thereof.

[0038] In another particular embodiment of the invention, the catalyst comprises at least one promoter. Said promoter may be selected from the list of alkali metals, alkaline earth metals, lanthanides, transition metals (other than ruthenium (Ru), rhodium (Rh), iridium (Ir) and cobalt (Co)), boron (B), aluminum (Al), gallium (Ga), indium (In), carbon (C), germanium (Ge), tin (Sn), nitrogen (N), phosphorus (P), arsenic (Ar), antimony (Sb), and any combination thereof. Any of these elements may be in elemental form or in ionic form. In a preferred embodiment of the invention, the promoter contributes to greater selectivity to aliphatic aldehydes. In a preferred embodiment of the invention, said promoter is selected from the list of alkali metals, alkaline earth metals, lanthanides, yttrium (Y), manganese (Mn), zinc (Zn), gallium (Ga), boron (B), indium (In) and any combination thereof.In an even more preferred embodiment of the invention, said promoter is selected from the list of alkali metals, alkaline earth metals, lanthanides, Y, B, Mn and any combination thereof. Said promoter may be present in a content in the range of 0.001-50% by weight, preferably in the range of 0.001-20% by weight, and more preferably in the range of 0.001-10% by weight, calculated on the basis of the total mass of the promoter element to the total mass of the catalyst.

[0039] Suitable methods for incorporating the second metal M2 and / or promoter elements include techniques known in the art such as impregnation, deposition precipitation, ion exchange, electrochemical deposition, electrostatic adsorption, melt infiltration, or coprecipitation with suitable precursors, including inorganic and organic salts, metal clusters, and organometallic complexes of the corresponding element. Examples of suitable rhodium-containing precursors are rhodium acetylacetonate, rhodium chloride, rhodium nitrate, rhodium sulfate, rhodium carbonyl chloride, rhodium(II) acetate dimer, dicarbonyl (pentamethylcyclopentadienyl) rhodium(I), acetylacetone (1,5-cyclooctadiene) rhodium(I), and the like. Rhodium precursors can provide ruthenium in a zero oxidation state, oxidation state I, oxidation state II, oxidation state III, or a combination thereof.

[0040] Before its application in the process of the invention, whether supported or unsupported, the catalyst is typically subjected to heat treatments in the presence of hydrogen or an alternative reducing agent to convert part or all of the active metallic portion into the metallic, i.e., zero-valent, state. In a preferred embodiment, said reduction treatment takes place at a temperature in the range of 373-873 K, and more preferably in the range of 373-773 K in the flow of a stream comprising hydrogen, either as pure gas or in combination with an inert gas selected from the list of nitrogen, helium, argon or combinations thereof.Said heat treatment may be omitted in cases where exposure to the reaction conditions of the process of the invention, that is, in the presence of synthesis gas as a reducing atmosphere, is sufficient to convert part or all of the active metallic part into a metallic state, in situ, in the reactor of the process of the invention.

[0041] During step (i) of the process of the invention, the catalyst metal, i.e. ruthenium, alone or in combination with a second metal (M2) selected from the list of rhodium (Rh), cobalt (Co), iridium (Ir), and any combination thereof, may exhibit one or several formal oxidation states in the reactor. Said metal preferably exhibits an oxidation state of +3 or lower, more preferably an oxidation state of +2 or lower, even more preferably an oxidation state of +1 or lower, and even more preferably an oxidation state of 0, i.e., zero-valent state.

[0042] In a particular embodiment of the invention, the catalyst is added to the reaction medium in a ratio of catalyst mass to solvent volume in the range of 0.001 kg / L to 0.1 kg / L, preferably in the range of 0.001 kg / L to 0.01 kg / L.

[0043] In a particular embodiment of the invention, an organic ligand is added to the liquid phase in which the catalyst is suspended in the solvent. The term "ligand", as used in the context of the present invention, is understood as an organic ion or molecule that can bind to a metal through coordination-type bonds, giving rise to a coordination complex. The role of the ligand is to promote the activity of the catalyst towards greater selectivity to aliphatic aldehydes. Without intending to be limited by any particular theory, it is considered that the ligand can form a coordination complex with one or more metal elements of the catalyst, which could have a formula H type chemistry. x (M)y(CO)z(L)n, where x is equal to or greater than zero, y is equal to or greater than 1 , z is equal to or greater than zero and n is equal to or greater than zero, and M denotes a metal, and L denotes an organic ligand.

[0044] The organic ligand can be selected from the list that includes phosphorus-containing ligands, nitrogen-containing ligands, oxygen-containing ligands, and combinations thereof. In particular, phosphorus-containing ligands can be selected from the list that includes phosphines, polyphosphines, phosphine oxides, and phosphites. Non-limiting examples include triethylphosphine, tributylphosphine, trihexylphosphine, trioctylphosphine, triisopropylphosphine, tricyclohexylphosphine, tricyclopentylphosphine, hexylphobane, cyclohexylphosphine, triphenylphosphine, diethylphenylphosphine, ethyldiphenylphosphine, bis(diphenylphosphino)ethane, bis(diphenylphosphino)butane, triphenylphosphite, 6,6'-[(3,3'-D¡- tert-butyl-5,5'-dimethoxy¡-[1, 1 '-biphenyl]-2, 2 '-dii I) bis(oxy)] bis(6 Hd i benzo[d , f][ 1,3,2]dioxafosfepin (Biphephos), (9,9-Dimethyl-9H-xanthene-4,5-diyl)bis-diphenylphosphane (Xantphos), 1,2-bis(diphenylphosphino)ethane (dppé), 2-(Dicyclohexylphosphino)-1-methyl-1 H-imidazole, and combinations thereof.In particular, the nitrogen-containing ligands may be selected from the list including monoamines, diamines, triamines and polyamines, imines, diimines, pyridines, bipyridines, imidazoles, pyrroles and pyrazoles. In particular, the oxygen-containing ligands may be selected from the list including alcohols, ethers, ketones, acetals and combinations thereof. In a preferred embodiment of the invention, the ligand is selected from the list including phosphorus-containing ligands.

[0045] In a particular embodiment of the invention, the ligand is added to the reactor in a molar ratio of ligand:M, defined as the quotient of the moles of ligand and the moles of metal M, between 0.1 and 100, preferably between 0.1 and 10 and more preferably between 0.1 and 1.0, where M represents Ru, a second metal (M2) selected from the list of rhodium (Rh), cobalt (Co), iridium (Ir), and any combination thereof in the catalyst formulation.

[0046] The present invention is described in more detail by means of the following figures and experimental examples.

[0047] FIGURES

[0048] Figure 1: Evolution of the relative abundance of products with hydrocarbon chain lengths in the Cs-ie range, along the ordinate axis, in arbitrary units, increasing from bottom to top, as a function of the chain growth probability parameter (dimensionless) along the abscissa axis, increasing from left to right, according to an Anderson-Schulz-Flory (ASF) distribution. The line joining the scattered data points corresponds to the interpolated spline function.

[0049] EXAMPLES

[0050] The following examples are presented by way of illustration, and are not intended to limit the scope of the invention.

[0051] The following experimental methods have been used to determine the properties of the materials prepared and used in the following examples:

[0052] (i) The specific surface area and pore volume of the support materials used for catalyst synthesis were determined by nitrogen adsorption. Nitrogen adsorption isotherms were recorded using an ASAP 2420 apparatus (Micromeritics) at -196 °C (77 K). Prior to analysis, approximately 200 mg of the sample (sieve fraction 0.2-0.4 mm) was degassed at a temperature of 673 K and a vacuum of ~5x10 -1 Pa for 15 hours. The specific surface area was determined using the Brunauer-Emmett-Teller (BET) equation in the relative pressure (P / P°) range of 0.05–0.3. The pore volume was derived from nitrogen adsorption at a relative pressure P / P°=0.95.

[0053] (i) The elemental composition of the catalysts was determined by X-ray fluorescence (XRF) spectroscopy on a Zetium 4 kV spectrometer (Malvern Panalytical), equipped with a Rh cathode as X-ray source. Measurements of powder samples were performed at room temperature and under helium atmosphere. Prior to measurements, the equipment was calibrated by preparing solid mixtures containing known metal concentrations, within the range consistent with the theoretical metal content of the catalysts. The calibration was repeated for each support material.

[0054] Synthesis of catalysts according to the invention

[0055] RU / SIO2 Catalyst A ruthenium precursor solution was prepared by dissolving ruthenium(III) nitrosyl nitrate (N4O10RU, Alfa Aesar, Ru 31.3% minimum content) in a 0.1 M HNO3 solution in deionized water. Specifically, 1.0 g of metal precursor was added to 2.5 mL of acid solution. Silica gel (S10020M - Silicycle) powder was used as catalyst support. The metal was incorporated by incipient wetness impregnation. The SIO2 support was first dried in a glass flask at 423 K for 15 hours under dynamic vacuum (1.5 mbar). Then, a volume of ruthenium precursor solution, equivalent to 90% of the pore volume of the SIO2 support (0.72 cm 3 / g), with the dry support, under magnetic stirring and static vacuum. After impregnation, the material was kept under dynamic vacuum (1.5 mbar) for at least 3 h, transferred to a quartz fixed-bed tubular reactor, axially mounted in a furnace, and treated at 623 K for 3 h (heating ramp to room temperature of 1 K / min) under an N2 / H2 flow (80% N2, 20% H2, vol) to decompose the Ru precursor and convert the metal to its metallic state. After heat treatment, the tubular reactor was purged with N2 flow and the activated catalyst was transferred to a glove box filled with N2 (C>2<1.0 ppm, H2O<0.1 ppm) for storage. The Ru content in the Ru / S¡C>2 catalyst was 7.0 wt%.

[0056] RU / AI2O3 catalyst

[0057] The Ru / Al2O3 catalyst was synthesized as detailed above for Ru / S¡C>2, using in this case Y-Al2O3 as support material. The Y-Al2O3 support was synthesized by calcining a pseudo-boehmite precursor (DISPERAL 80, Sasol) at 823 K (heating ramp of 2 K / min from room temperature) for 5 h in a muffle furnace under air atmosphere, and presented a pore volume of 0.66 cm 3 / g. After the incorporation of Ru by impregnation at incipient wetness, as detailed above, the solid was dried at room temperature under dynamic vacuum (1.5 mbar) for at least 3 h, transferred to a quartz fixed bed tubular reactor, axially mounted in a furnace, and treated at 623 K for 3 h (heating ramp from room temperature of 1 K / min) under a flow of N2 / H2 (80% N2, 20% H2, vol) to decompose the Ru precursor and convert the metal to its metallic state. The Ru content in the RU / AI2O3 catalyst was 8.0 wt%.

[0058] General experimental method for testing catalysts according to the invention

[0059] In a general experimental method, the conversion reaction is carried out in a magnetically stirred 316L stainless steel batch reactor (ILSHIN) with an internal volume of approximately 30 mL. Temperature is measured using a K-type thermocouple sheathed in a 316L stainless steel sheath, inserted into the liquid reaction medium, while pressure is measured using a digital pressure transducer (Sensys).

[0060] Prior to reaction experiments, all liquid reactants were dried for 15 h using a thermally activated molecular sieve (5 A, particle size 3.2 mm, Sigma Aldrich) and then stored in a glove box under N2 atmosphere (U2< 1.0 ppm, H2O < 0.1 ppm). Also under exclusion of air, the powdered catalyst, solvent, optionally the organic ligand, and a magnetic stir bar (L x D 9 mm x 20 mm) were added to a PTFE liner and the latter was capped and inserted into the autoclave reactor body. The autoclave was then sealed and purged three times with a synthetic synthesis gas mixture containing CO / H2 / Ar (Ar used as an internal standard for gas chromatography analysis of gaseous products) in preset volumetric ratios, and then filled with the same synthesis gas mixture to a preset total pressure P (bar) at room temperature.The reactor was inserted into a custom-made aluminum block mounted on a stir / heating plate (Heidolph), the stirring speed was set to 800 rpm, and the temperature inside the autoclave liner was raised to the reaction temperature at a rate of 3 K / min. After a selected reaction time, the autoclave reactor was cooled to room temperature. The gas phase in the headspace was sampled on an Agilent 7890 gas chromatograph equipped with two analytical channels and using He as the carrier gas.A first channel equipped with an HP-PLOT-Q packed column (30 m, 0.32 mm ID, 20.0 pm film thickness) and an HP-MOLSIEVE packed column molecular sieve (30 m, 0.32 mm ID, 12.0 pm film thickness) and a TCD detector for the analysis of permanent gases and carbon dioxide using argon as internal standard; and a second analysis channel equipped with a DB1 capillary column (60 m, 0.32 mm ID, 3 pm film thickness) and an FID detector for the analysis of hydrocarbons and oxygenated organic compounds. The liquid phase of the product was collected directly from the lining inside the reactor and filtered to remove solid particles prior to analysis.Gas chromatography analysis was performed on a Shimadzu GC-2010 Plus gas chromatograph equipped with an HP5 capillary column (30 m, 0.25 mm i.d., 0.25 pm film thickness) and an FID detector, using H2 as the carrier gas and tetrahydrofuran (THF) as the external standard. Both liquid and gas phase products were identified by gas chromatography / mass spectrometry using an Agilent 8890 gas chromatograph paired with a 5977B single quadrupole GC / MSD equipped with an HP5 capillary column (30 m, 0.32 mm i.d., 0.32 pm film thickness) for compound separation and an FID detector for analysis. Helium was used as the carrier gas.The mass-based response factors in the FID detector of those reaction products not available in pure form from commercial suppliers were determined using a polyARC microreactor coupled with the FID detector on the Agilent 8890 gas chromatograph.

[0061] Example I

[0062] In an example according to the present invention, 148 mg of RU / AI2O3 was used as catalyst and 12 mL of 1,4-dioxane (Sigma Aldrich, 99.8%) was added to the reactor as solvent. The experiment was carried out according to the general experimental method for catalytic tests described above. The H2:CO molar ratio in the feed synthesis gas was 1:1. The reaction time was 24 h.

[0063] Example II

[0064] In an example according to the present invention, 267 mg of Ru / AhOs were used as catalyst and 12 mL of iso-octane (Sigma Aldrich, 99.8%) were added to the reactor as solvent. The experiment was carried out according to the general experimental method for catalytic tests described above. The H2:CO molar ratio in the feed gas was 2:1. The reaction time was 24 h.

[0065] Example III

[0066] In an example according to the present invention, 182 mg of Ru / S¡C>2 were used as catalyst and 12 mL of iso-octane (Sigma Aldrich, 99.8%) were added as solvent. The experiment was carried out according to the general experimental method for catalytic tests described above. The H2:CO molar ratio in the feed gas was 1:1. The reaction time was 24 h.

[0067] Example IV

[0068] In an example according to the present invention, 180 mg of Ru / S¡C>2 was used as catalyst and 12 mL of iso-octane (Sigma Aldrich, 99.8%) was added to the reactor as solvent. The experiment was carried out according to the general experimental method for catalytic tests described above. The H2:CO molar ratio in the feed gas was 1:1. The reaction time was 24 h.

[0069] Example V In an example according to the present invention, 177 mg of Ru / S¡C>2 was used as catalyst and 12 mL of iso-octane (Sigma Aldrich, 99.8%) was added to the reactor as solvent. The experiment was carried out according to the general experimental method for catalytic tests described above. The H2:CO molar ratio in the feed gas 5 was 1 : 1. The reaction time was 24 h.

[0070] Example VI

[0071] In an example according to the present invention, 145 mg of Ru / S¡C>2 was applied as catalyst, and 12 mL of iso-octane (Sigma Aldrich, anhydrous, 99.8%) was added as solvent. The method was carried out according to the general experimental procedure for catalytic tests described above. The H2:CO molar ratio in the feed gas was 1.5:1. The reaction time was 24 h.

[0072] Example VII 5 In an example according to the present invention, 231 mg of Ru / S¡O2 was used as catalyst and 12 mL of iso-octane (Sigma Aldrich, anhydrous, 99.8%) was added as solvent. The experiment was carried out according to the general experimental method for catalytic tests described above. The H2:CO molar ratio in the feed gas was 1:1. The reaction time was 24 h.

[0073] Example VIII

[0074] In an example according to the present invention, 181 mg of Ru / AhCh were used as catalyst, 12 mL of iso-octane (Sigma Aldrich, anhydrous, 99.8%) were added as solvent and 2.5 mg of triphenylphosphine (Sigma Aldrich, 99.9%) as organic ligand. The experiment was carried out according to the general experimental method for catalytic tests described above. The H2:CO molar ratio in the feed gas was 1:1. The reaction time was 24 h.

[0075] Table 1: Summary of conversion and selectivities to products for examples 0 carried out according to the process of the invention.

[0076] (a) Reaction temperature in degrees Kelvin; (b) Total pressure, in megapascals, determined at the start of the reaction and at the reaction temperature; (c) molar ratio of CO in the syngas feed to metal in the catalyst; (d) CO conversion; (e) Selectivities expressed on a carbon molar basis; (f) non-oxygenated hydrocarbons; (g) Chain growth probability parameter determined from the analysis of the alkyl chain length in the aliphatic aldehyde products according to an ASF distribution considering compounds in the chain length range n=Cs-C25. nd: not detected.

[0077] Although the present invention has been described in terms of preferred embodiments, it is understood that such description should not be construed as a limitation of the invention described herein. Upon reading the description, it will be readily apparent to those of ordinary skill in the art, in view of the teachings of this invention, that various alterations and modifications can be made thereto. The appended claims should be construed as embracing all such alterations and modifications as fall within the spirit and scope of the present invention.

Claims

CLAIMS 1. A process for producing aliphatic aldehydes comprising at least the following steps: (i) supplying a reactor with a. a synthesis gas feed, and b. a solvent (i) reacting the synthesis gas supplied in step (i) on a catalyst comprising ruthenium (Ru), either in unsupported form or dispersed on a support material, at a reaction temperature of between 373 and 523 degrees Kelvin (K) and at a total pressure of between 0.1 MPa and 30 MPa; (iii) recovering the aliphatic aldehydes from the reaction products of step (i).

2. A method according to claim 1, wherein the catalyst is a supported catalyst in which Ru is dispersed on a support material selected from the list comprising: SiO2, transition forms of Al2O3, a-ALOs, TiO2, ZrO2, carbide or oxycarbide materials selected from: SiC and SiO xC y , where x is in the range of 0 <x<2 e y en el rango de 0<y<1 , carbono cualquier combinación los mismos.

3. A process according to any of the preceding claims, wherein the weight fraction of the total catalyst corresponding to Ru is in the range of 0.5-50% by weight.

4. A process according to any of the preceding claims, wherein the catalyst further comprises a second metal M2 selected from the list of rhodium (Rh), cobalt (Co), iridium (Ir) and any combination thereof.

5. A process according to any of the preceding claims, wherein the content of the second metal (M2), expressed as the molar ratio M2:Ru, is between 0.001 and 1.

6. A process according to any of the preceding claims, wherein the catalyst further comprises a promoting element selected from the list comprising: alkali metals, alkaline earth metals, lanthanides, transition metals other than ruthenium (Ru), rhodium (Rh), iridium (Ir) and cobalt (Co), boron (B), aluminum (Al), gallium (Ga), indium (In), carbon (C), germanium (Ge), tin (Sn), nitrogen (N), phosphorus (P), arsenic (Ar), antimony (Sb), and any combination thereof.

7. A process according to claim 6, wherein the promoter element is present in a content between 0.001 and 50% by weight, calculated on the basis of the total mass of the promoter element with respect to the total mass of the catalyst.

8. A process according to any of the preceding claims, wherein the solvent is selected from the list comprising: aliphatic hydrocarbons, aromatic hydrocarbons, oxygenated organic compounds, water, nitrogenous organic compounds, halogenated organic compounds, liquid organic salts and combinations thereof.

9. A process according to any of the preceding claims, wherein an organic ligand selected from the list comprising: phosphorus-containing ligands, nitrogen-containing ligands, oxygen-containing ligands, and combinations thereof is further added to the solvent.

10. A method according to claim 9, wherein the organic ligand is selected from the list including phosphines, polyphosphines, phosphine oxides and phosphites.

11. A process according to any of the preceding claims, wherein the reaction is carried out in a stirred batch reactor.

12. A process according to any one of claims 1 to 10, wherein the reaction is carried out in a continuous reactor to which both a gas stream and a liquid stream are fed.

13. A process according to any of the preceding claims, wherein the reaction temperature is in the range between 393 K and 453 K.

14. A process according to any of the preceding claims, wherein the reaction pressure is in the range of 1 MPa to 20 MPa.

15. A process according to any preceding claim, wherein the H2:CO molar ratio in the synthesis gas feed is between 0.1 and 5.

0.

16. A process according to any of the preceding claims, wherein the aliphatic aldehydes are linear aliphatic aldehydes with a hydrocarbon chain length of between 8 and 16 carbon atoms.

17. A process according to any preceding claim, wherein the synthesis gas feed further comprises other compounds such as nitrogen, helium, argon, water, C1-C4 alkanes or combinations thereof.

18. A process according to any preceding claim, wherein, after recovery of aliphatic aldehydes from the reaction products, a stream containing unconverted reactants, solvent, unrecovered reaction products, or a combination thereof, is recycled to the reactor.

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