ES3032946A1 - PROCEDURE FOR THE PRODUCTION OF ALIPHATIC AMIDES (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Process for the production of aliphatic amides. The present invention relates to a process for producing N-substituted alkylamides, including fatty N-substituted alkylamides, by contacting synthesis gas and an amide compound with a ruthenium catalyst. (Machine-translation by Google Translate, not legally binding)

Description

DESCRIPTION

Procedure for the production of aliphatic amides

FIELD OF INVENTION

The present invention relates to a process for producing N-substituted alkylamides, including fatty N-substituted alkylamides, by contacting synthesis gas and an amide compound with a catalyst.

BACKGROUND

N-substituted aliphatic amides (or simply N-alkylamides) are chemical compounds with a general molecular formula:

where B<1> can be a hydrogen atom or a hydrocarbyl, and at least one of the substituent groups R<1> and R<2> directly bonded to the central nitrogen atom is an alkyl group. As a separate class, N-alkyl fatty amides are alkyl amides in which at least one of the substituents R<1> and R<2> is an alkyl chain with carbon atoms (C<n>) containing between about 7 and about 30 carbon atoms. N-alkyl amides and their derivatives are valuable as intermediates in the pharmaceutical and polymer industries, phase change materials, precursors to surface-active substances in various industries, including paint manufacturing, cosmetics, or the textile industry, antistatic agents, anticaking agents, as well as precursors to alkyl isonitriles and amines, among other applications.

N-Alkylamides are conventionally produced by the condensation of carboxylic acids and alkylamines. A process for synthesizing N-alkylamides from glycerides and amines in the absence of a catalyst is described in US5,681,971. Eric Valeur and Mark Bradley, "Amide bond formation: beyond the myth of coupling reagents," Chemical Society Reviews, 2009, volume 38, pages 606-631, provides a review of the catalysts and conditions for the synthesis of N-alkylamides from carboxylic acid and amine compounds.

N-Alkylamines can also be synthesized by catalytic amidation of aliphatic olefins with nitriles. A process for preparing N-monosubstituted secondary alkylamides is presented in US 3,530,153. This process consists of reacting an aliphatic olefin with a nitrile and water in the presence of hydrogen fluoride. K. Yasude & Y. Obora, "NbCl<5>-mediated amidation of olefins with nitriles to secondary amides" Journal of Organometallic Chemistry, Volume 775, 2015, pages 33-38 reports a process for producing N-alkylamides by amidation of olefins with nitriles.

Alternatively, N-alkylamides can be produced by the catalytic coupling of aliphatic alcohol or alkyl halide reagents with amines, as described, for example, in C. Gunanathan and D. Milstein, "Applications of Acceptorless Dehydrogenation and Related Transformations in Chemical Synthesis", Science, 2013, 341, 249, or in C. L. Allen and J. M. J. Williams, "Metal-catalyzed approaches to amide bond formation", Chemical Society Reviews, 2011, vol. 40, 3405.

Catalytic oxidative amidation of aldehydes with alkylamide salts is another known procedure to produce N-alkylamides, as described in Gaspa et al. "Recent developments in oxidative esterification and amidation of aldehydes", Tetrahedron Letters, Volume 57, Issue 31, 2016, pages 3433-3440.

A common element in the above processes for preparing N-alkylamides is that the alkyl substituents (R<1> and/or R<2>) in the final N-alkylamide product must be provided in the form of a preformed Cn synthon as part of a reactive compound. Such a reactive compound, which, as described above, may be an aliphatic olefin, alcohol, amine, alkyl halide, etc., must be produced in a separate process or isolated from natural sources. It is desirable to develop processes for the production of alkylamides in which the alkyl substituents can be produced from monocarbon (C<1>) precursors and incorporated into the N-alkylamide products in a single reaction step.

Synthesis gas, commonly abbreviated as "syngas” is a mixture composed of carbon monoxide (CO), hydrogen (H<2>) and, in some cases, carbon dioxide (CO<2>) as main components. Synthesis gas streams may also comprise other gases such as nitrogen (N<2>), helium (He), argon (Ar), water vapor (H<2>O) or light hydrocarbons such as methane (CH<4>), ethane (C<2>H<6>), propane (C<3>H<8>), 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 or shale gas, coal gasification, biomass gasification and/or reforming, carbon dioxide hydrogenation or coelectrolysis of CO<2> and water, among others, and is therefore considered a very versatile C<1> 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). Those skilled in the art are aware of prior work on processes in which a synthesis gas feed is mixed with a gas-phase nitrogen source, such as ammonia, and said gas mixture is contacted with a catalyst, under standard conditions for Fischer-Tropsch synthesis, to promote the formation of nitrogen-containing organic compounds, or N-compounds for short. Typically, a complex mixture of nitrogen-containing compounds is produced along with non-nitrogenous hydrocarbons.

US 2,821,537 describes a process for the catalytic hydrogenation of carbon monoxide to products containing organic nitrogen compounds, in addition to a relatively high content of oxygen-containing compounds, preferably alcohols. A mixture of synthesis gas is fed, together with 0.5 to 2% by volume of a nitrogen-containing compound selected from the group consisting of ammonia and methylamine, and the mixture reacts over a precipitated iron catalyst. The reaction products contain organic nitrogen compounds, more than 20% oxygen-containing compounds, and a high content of non-nitrogenous olefinic hydrocarbons.

WO2009/127942A2 describes a process for the production of at least one nitrogen- or phosphorus-containing compound selected from linear nitriles, amides, formamides and linear phosphorus-containing compounds, from synthesis gas, characterized in that the synthesis gas together with at least one nitrogen- or phosphorus-containing compound are introduced into a reactor and reacted over a catalyst, preferably composed of unsupported and promoted iron. The process is carried out at temperatures in the range of 433 K and 673 K, and pressures between 1 and 50 bar. Ammonia, nitrogen oxides (N<2>O, NO, NO<2>) and mixtures thereof are described in the document as nitrogen-containing compounds that can be fed, as a nitrogen source, and react together with the synthesis gas. The organic products comprise a mixture of non-nitrogenous hydrocarbons (paraffins, olefins and oxygenates) and nitrogen-containing organic compounds. Alkylamides and formamides are produced with low selectivity (<1% under the conditions exemplified in the document).

A first objective of the present invention is to provide a process for producing N-alkylamides by direct N-alkylation of amide compounds with synthesis gas, in a single reaction step. A second objective of the present invention is to provide a process for producing fatty N-alkylamides with alkyl groups of between 7 and 30 carbon atoms.

DESCRIPTION

The present invention relates to a process for producing N-alkylamides which can be implemented by at least the following steps:

i) supply a reactor

a. a synthesis gas feed, and

b. at least one amide reagent selected from compounds with molecular formulae B<1>-CONB<2>H, and any combination thereof, either in pure form or dissolved in a solvent,

ii) reacting the feeds supplied in step (i) by contacting them with a catalyst comprising ruthenium (Ru), either in unsupported form or dispersed on a support material, at a reaction temperature comprised between 373 and 523 degrees Kelvin (K) and at a total pressure comprised between 0.1 MPa and 30 MPa, where 1 MPa (megapascal) is equivalent to 106 Pa;

iii) recovering from the reaction products of step (ii) N-alkylamides selected from those having molecular formulae B<1>-CONB<2>R<1>, B<1>-CONR<1>R<2> and any combination thereof,

where the groups B<1> and B<2> may be either a hydrogen atom, identical or different hydrocarbyl groups, or any combination thereof, and the groups R<1> and R<2> are alkyl groups with carbon atoms, respectively, in which m and n may be identical or different.

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

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 N-alkylamides, to the total molar amount of carbon in all reaction products, and is expressed on a percentage basis.

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.

The term “N-alkylation,” as used in the context of the present invention, is defined as a chemical reaction in which an alkyl group is added to a nitrogen atom in a molecule. Such a molecule is an amide compound according to the present invention.

Procedure

The types of reactors that are suitable for implementing the process of the invention are those that allow contact 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.

According to the present invention, the H<2>: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 H<2>:CO molar ratio in the synthesis gas is in the range of 0.3 to 3.0. More preferably, the H<2>:CO molar ratio in the synthesis gas is in the range of 0.5 to 2.0.

According to the present invention, the synthesis gas feed may comprise CO<2>. According to the present invention, the CO<2>:CO molar ratio in the synthesis gas feed may be in the range of 0 to 2.0. In a preferred embodiment of the present invention, said CO<2>:CO molar ratio in the synthesis gas is in the range of 0 to 0.5. More preferably, the CO<2>:CO molar ratio in the synthesis gas is in the range of 0 to 0.1.

The synthesis gas feed may also comprise other compounds such as nitrogen, helium, argon, water, C<1>-C<4> alkanes (alkanes comprising between 1 and 4 carbon atoms), or combinations thereof. Such compounds do not interfere with the conversion of the synthesis gas.

In addition to synthesis gas, in the process of the invention, at least one amide reactant is fed to the reactor. Said amide reactant may be selected from those having molecular formulas B<1>-CONB<2>H, and combinations thereof, where the groups B<1> and B<2> may be a hydrogen atom or identical or different hydrocarbyl groups. According to a preferred embodiment of the invention, said amide reactant is a formamide selected from those with molecular formulas H-CONH<2>, H-CONB<2>H and combinations thereof. According to an even more preferred embodiment of the invention, said amide reactant is N-methylformamide.

In a particular embodiment, the N-alkylamide products obtained by the process of the invention have a molecular formula B<1>-CONB<2>R<1>in which the groups B<1> and B<2> are either a hydrogen atom, identical or different hydrocarbyl groups, or any combination thereof, and the group R<1> is a linear n-alkyl group with n carbon atoms. In another particular embodiment of the process of the invention, the N-alkylamide products have a molecular formula B<1>-CONHR<1>in which the group B<1> is a hydrogen atom or a hydrocarbyl group, and the group R<1> is a linear n-alkyl group with n carbon atoms. In another particular embodiment of the process of the invention, the N-alkylamide products have a molecular formula B<1>-CONR<1>R<2>, in which the group B<1> is a hydrogen atom or a hydrocarbyl group, and the groups R<1> and R<2> are linear alkyl groups with carbon atoms, respectively, in which n and m may be identical or different.

In a preferred embodiment of the invention, nes is a number equal to or greater than 7.

In another preferred embodiment of the invention, mes is a number equal to or greater than 7.

Said amide reagent can be supplied as a pure compound or as part of a solution, i.e., dissolved in a suitable solvent that is stable under the process conditions. According to a particular embodiment of the invention, said amide reagent is supplied to the reactor as part of a solution in a suitable solvent, which is stable under the process conditions.

The solvent supplied in step (i) provides improved temperature control and a means for solubilizing compounds in the reactor. Such compounds comprise the amide reactant, reaction products, 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, /s-pentane (2-methylbutane), /s-hexane (2-methylpentane), /s-octane (2,2,4-trimethylpentane), and 2,6,11,15-tetramethylhexadecane. Again more specifically, aromatic hydrocarbon solvents may be selected from the non-limiting list consisting of benzene, toluene, xylene, trimethylbenzenes, and naphthalene. Again more specifically, 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 solvents may be selected from the non-limiting list consisting of acetonitrile, benzonitrile, diethanolamine, trin-butylamine, triethylamine, N,N-dimethylaniline, pyridine, 2-methylpyridine, N-methylmorpholine, N-methylpiperidine, N-methylpyrrole, and quinoline. Again more specifically, the halogenated organic 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 type associated with anions of the PF<6->, BF<4->, NTf<2->(bis(trifluoromethylsulfonyl)amide), OTf<">(trifluoromethylsulfonate), DCA<->(dicyanamide), acetate and CH<3>SO<3-> type.

According to another embodiment of the invention, the amide compound is introduced into the reactor in the dual role of reactant and solvent. The use of a single compound in the dual role of both amide reactant and solvent facilitates process design, since the reaction products can be separated from the solvent, and the latter can be recycled to the reactor, with a small make-up addition to compensate for its consumption in the reaction. In a particular embodiment of the invention, N-methylformamide is introduced into the reactor in the dual role of reactant and solvent.

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.

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 pressure between 4 MPa and 10 MPa.

In the process of the invention, the distribution of alkyl substituents in the N-alkylamide 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 C<1> units. This product distribution is mathematically described by the following relationship (Eq. 1):

where Wn is the mass fraction of N-alkylamide products for which the alkyl group (C<n>), or the longest alkyl group if more than one alkyl group is bonded to the nitrogen atom of the amide group, contains 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 C<n> hydrocarbon chain, causing the latter to grow by one carbon atom. Experimentally, the chain growth probability (alpha) can be determined according to the relationship a=em, where e is the Euler number and m represents the slope obtained for the mathematical function of linear regression of the data on a graph plotting Ln(W<n>/n) versus n over a sufficiently wide range of carbon chain lengths n, where Ln represents the natural logarithmic function.

Typically, the product mixture of the inventive process is fractionated to recover N-alkylamide products. Recovery of N-alkylamide products from mixtures with other reaction products, e.g., paraffins, can be carried out by methods such as distillation, liquid-liquid extraction, selective adsorption, or reactive derivatization of N-alkylamides to other derivative compounds, such as hydrazones, enamine oximes, acetals, or organoboron compounds, followed by any of the above methods.

In a particular embodiment of the invention, the stream containing reactants that have not been converted, solvent, unrecovered reaction products, or a combination thereof, is recycled to the reactor.

Catalyst

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.

Several processes are known in the art for incorporating a metallic part 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 part into a support material are provided in "Handbook of Heterogeneous Catalysis", G. Ertl, H. Knozinger, 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.

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 more than 50% of the metallic portion. More preferably, Ru represents more than 80% of the metallic portion.

The support material must be chemically stable under the reaction conditions encountered in a synthesis gas conversion process. Such a support may be an oxide selected from those porous oxide supports that are employed as support materials for supported metal catalysts in the art, and which may comprise, but are not limited to, SiO<2>, transition forms of AhO<3>, α-AhO<3>, TiO<2>, ZrO<2>, carbide or oxycarbide material such as SiC, SiO<x>C<y>, with x in the range of 0<x<2 and y in the range of 0<y<1 and any combination thereof. Alternatively, the support material may be carbon-based. Alternatively, the support material may be a composite incorporating a combination of such materials. By transition forms of AhO<3> are meant metastable polymorphs of aluminium oxide (111) which can be obtained at intermediate temperatures during the transformation of aluminium hydroxides and oxyhydroxides to the thermodynamically most stable phase, i.e. alpha-AhO<3> (a-AhO<3>). Such transition forms of Al<2>O<3> comprise chi-Al<2>O<3>, kappa-AhO<3>, gamma-Al<2>O<3>, delta-Al<2>O<3>, theta-Al<2>O<3>, eta-Al<2>O<3>, rho-Al<2>O<3>, and combinations thereof.

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-

<2 0>% by weight.

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.

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.

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.

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., N-alkylamides in the present invention, stability under operating conditions, or a combination thereof.

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 N-alkylamides. 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 is present in a content in the range of 0-50% by weight, preferably in the range of 0-20% by weight, and more preferably in the range of 0-10% by weight, calculated on the basis of the total mass of the promoter element to the total mass of the catalyst.

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 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.

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 state, i.e., zero-valent. 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 dispensed with in cases where exposure to the reaction conditions of the process of the invention, i.e., in the presence of synthesis gas as a reducing atmosphere, is sufficient to convert part or all of the active metallic portion into the metallic state, in situ, in the reactor of the process of the invention.

During step (ii) of the process of the invention, the catalyst metal, that is, 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 have one or more formal oxidation states in the reactor. Said metal preferably has 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, that is, a zero-valent state.

In a particular embodiment of the invention, the catalyst is added to the reaction medium in a ratio of mass of catalyst to volume of solvent, alternatively volume of amide reagent when it is fed in the form of a pure compound, 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.

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

FIGURES

Figure 1: 13C[1H] nuclear magnetic resonance spectrum (400 MHz, CDCh, room temperature) for a representative mixture of products comprising N-alkylamides obtained according to the process of the invention using N-methylformamide as the amide reagent. Process conditions: 5 mL of N-methylformamide, 82.8 mg of Ru/AhO<3> catalyst, T=413 K, P=1.5 MPa (initial, measured at room temperature), N<2> (99.999% vol) gas phase, stirring speed 800 revolutions per minute, reaction time 24 h. The abscissa (x) axis represents the chemical shift in units of parts per million (ppm), increasing from right to left. The ordinate (y) axis represents the intensity in arbitrary units, increasing from bottom to top. The inset shows an enlarged view of a spectral region. 58.02 -8 .01 (m, 1H), 3.32 -3 .18 (m, 2H), 2.94 -2 .81 (m, 3H), 1.64 -1 .57 (m, 3H), 1.31 (d,J= 46.8 Hz, 37H), 0.90 -0 .83 (m, 10H).

EXAMPLES

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

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

(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 ~0.5 Pa for 15 h. The specific surface area was determined by applying 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/P0=0.95.

(ii) 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 the X-ray source. Measurements of the powder samples were performed at room temperature and under a 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.

(iii) The molecular structure of the N-alkylamide product mixture was evaluated by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and distortion-free enhancement polarization transfer (13C-DEPT) NMR spectroscopy. About 25 mg of the product mixture recovered after one reaction run was transferred to a Young's NMR tube and diluted with deuterated chloroform. Spectra were acquired on a 400 MHz NMR spectrometer (Bruker) equipped with an autosampler at a temperature of 293 K.

Synthesis of catalysts according to the invention

Ru/SiO2 catalyst

A ruthenium precursor solution was prepared by dissolving ruthenium(III) nitrosyl nitrate (N<4>O<10>Ru, AlfaAesar, Ru 31.3% minimum content) in a 0.1 M HNO<3> 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 SiO<2> support was first dried in a glass flask at 423 K for 15 hours under dynamic vacuum (1.5 mbar). Next, a volume of ruthenium precursor solution, equivalent to 90% of the pore volume of the SiO<2> support (0.72 cm<3>/g), was contacted 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 (room temperature heating ramp of 1 K/min) under a N<2>/H<2> flow (80% N<2>, 20% H<2>, vol) to decompose the Ru precursor and convert the metal to its metallic state. After heat treatment, the tubular reactor was purged with N<2> flow and the activated catalyst was transferred to a glove box filled with N<2> (O<2><<1.0>ppm, H<2>O<<0.1>ppm) for storage. The Ru content in the Ru/SiO<2> catalyst was 7.0 wt%.

RU/AI2O3 catalyst

The Ru/AhO<3> catalyst was synthesized as detailed above for Ru/SiO<2>, using Y-AhO3 as the support material in this case. The Y-AhO3 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 cm3/g. Following the incorporation of Ru by incipient wetness impregnation 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 rate of N<2>/H<2> (80% N2, 20% H<2>, vol) to decompose the Ru precursor and convert the metal to its metallic state. The Ru content in the Ru/AhO<3> catalyst was 8.0 wt %.

General experimental method for testing catalysts according to the invention

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).

Prior to reaction experiments, all liquid reactants were dried for 15 h using a thermally activated molecular sieve (5 A, 3.2 mm particle size, Sigma Aldrich) and then stored in a glove box under N<2> atmosphere (O<2>< 1.0 ppm, H<2>O < 0.1 ppm). Also under exclusion of air, the powdered catalyst, the amide reactive compound, the solvent (when different from the amide reactive compound) and a magnetic stir bar (L x D 9 mm x 20 mm) were added to a PTFE cylindrical 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/H<2>/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 inner diameter, 20.0 jm film thickness) and an HP-MOLSIEVE packed column molecular sieve (30 m, 0.32 mm inner diameter, 12.0 jm 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 inner diameter, 3 jm film thickness) and an FID detector for the analysis of hydrocarbons and nitrogen 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 μm film thickness) and an FID detector, using H<2> as the carrier gas and tetrahydrofuran (THF) as the external standard. Both liquid and gaseous 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 μm film thickness) for compound separation and an FID detector for analysis. Helium was used as the carrier gas. The mass-based response factors at 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.

Example I

In an example according to the present invention, 79.8 mg of Ru/AhO<3> was used as catalyst and 12 mL of N-methylformamide (Sigma Aldrich, 99%) was added to the reactor in the dual role of amide reagent and solvent. The experiment was carried out according to the general experimental method for catalytic tests described above. The H<2>:CO molar ratio in the feed synthesis gas was 1:1. The reaction time was 24 h.

Example II

In one example according to the present invention, 150 mg of Ru/AhO<3> was used as catalyst and 12 mL of N-methylformamide (Sigma Aldrich, 99%) was added to the reactor in the dual role of amide reagent and solvent. The experiment was carried out according to the general experimental method for catalytic tests described above. The H<2>:CO molar ratio in the feed synthesis gas was 1:1. The reaction time was 24 h.

Example III

In an example according to the present invention, 149 mg of Ru/SiO<2> was used as catalyst and 12 mL of N-methylformamide (Sigma Aldrich, 99%) was added to the reactor in the dual role of amide reagent and solvent. The experiment was carried out according to the general experimental method for catalytic tests described above. The H<2>:CO molar ratio in the feed synthesis gas was 1:1. The reaction time was 24 h.

Example IV

In an example according to the present invention, 189 mg of Ru/SiO<2> was used as catalyst and 12 mL of N-methylformamide (Sigma Aldrich, 99%) was added to the reactor in the dual role of amide reagent and solvent. The experiment was carried out according to the general experimental method for catalytic tests described above. The H<2>:CO molar ratio in the feed synthesis gas was 1:1. The reaction time was 24 h.

Example V

In an example according to the present invention, 149 mg of Ru/SiO<2> was used as catalyst and 12 mL of N-methylformamide (Sigma Aldrich, 99%) was added to the reactor in the dual role of amide reagent and solvent. The experiment was carried out according to the general experimental method for catalytic tests described above. The H<2>:CO molar ratio in the feed synthesis gas was 2:1. The reaction time was 24 h.

Example VI

In an example according to the present invention, 151 mg of Ru/AhO<3> was applied as catalyst, 1 mL of N-methylformamide (Sigma Aldrich, 99%) was added as amide reagent dissolved in 12 mL of 1,4-dioxane (Sigma Aldrich, anhydrous, 99.8%) as solvent. The method was carried out according to the general experimental procedure for catalytic tests described above. The H<2>:CO molar ratio in the feed synthesis gas was 1:1. The reaction time was 24 h.

Example VII

In an example according to the present invention, 200 mg of Ru/SiO<2> was used as catalyst and 12 mL of N-methylformamide (Sigma Aldrich, 99%) was added to the reactor in the dual role of amide reagent and solvent. The experiment was carried out according to the general experimental method for catalytic tests described above. The H<2>:CO molar ratio in the feed synthesis gas was 1:1. The reaction time was 24 h.

Example VIII

In an example according to the present invention, 199 mg of Ru/AhO<3> was employed as catalyst, 0.5 mL of N-methylformamide (Sigma Aldrich, 99%) was added as amide reagent dissolved in 12 mL of 1,4-dioxane (Sigma Aldrich, anhydrous, 99.8%) as solvent. The experiment was carried out according to the general experimental method for catalytic tests described above. The molar ratio H<2>:CO in the feed synthesis gas was 1:1. The reaction time was 24 h.

Table 1: Summary of conversion and product selectivities for the examples made according to the present invention.

(a) Reaction temperature; (b) Total pressure, determined at the start of the reaction and at the reaction temperature; (c) Molar ratio of CO in the synthesis gas feed to the total metal in the catalyst; (d) CO conversion; (e) Product selectivity, determined on a carbon molar basis; (f) Non-nitrogenous hydrocarbons, i.e., paraffins and olefins; (g) Byproducts of the amide reactant conversion; (i) Chain growth probability parameter determined from alkyl chain length analysis in N-alkylamide products according to an ASF-type distribution in the chain length range n=5–20.

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 immediately 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 falling within the spirit and scope of the present invention.

Claims (20)

1. A process for producing N-alkylamides comprising at least the following steps: i) supply a reactor c. a synthesis gas feed, and d. at least one amide reagent selected from compounds with molecular formulas B<1>-CONB<2>H, and any combination thereof. ii) reacting the feeds supplied in step (i) by contacting them with a catalyst comprising ruthenium (Ru), either in unsupported form or dispersed on a support material, at a reaction temperature comprised between 373 and 523 degrees Kelvin and at a total pressure comprised between 0.1 MPa and 30 MPa; iii) recovering from the reaction products of step (ii) N-alkylamides selected from those having molecular formulae B<1>-CONB<2>R<1>, Bi-CONR<1>R<2> and any combination thereof, where the groups Bi and B<2> are either a hydrogen atom, identical or different hydrocarbyl groups, or any combination thereof, and the groups Ri and R<2> are alkyl groups with carbon atoms, respectively, in which m and n may be identical or different. 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 SiO<2>, transition forms of AhO<3>, α-AhO<3>, TiO<2>, ZrO<2>, carbide or oxycarbide materials selected from: SiC, SiOxCy, where x is in the range of 0<x<2 and y is in the range of 0<y<1, carbon and any combination thereof. 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 method according to claim 4, 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 preceding claim, 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), 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 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 in step i,d) a solvent 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 is added. 9. A process according to any of the preceding claims, wherein the reaction is carried out in a stirred batch reactor. 10. A process according to any one of claims 1 to 8, wherein the reaction is carried out in a continuous reactor to which both a gas stream and a liquid stream are fed. 11. A process according to any of the preceding claims, wherein the reaction temperature is in the range between 393 K and 453 K. 12. A process according to any of the preceding claims, wherein the reaction pressure is in the range of 1 MPa to 20 MPa. 13. A process according to any preceding claim, wherein the H<2>:CO molar ratio in the synthesis gas feed is between 0.1 and 5.0. 14. A process according to any preceding claim, wherein the N-alkylamide products have a molecular formula B<1>-CONB<2>R<1> wherein the groups B<1> and B<2> are either a hydrogen atom, identical or different hydrocarbyl groups, or any combination thereof, and the group R<1> is a linear n-alkyl group with carbon atoms. 15. A process according to any of claim 14, wherein the group B<2> is a hydrogen atom. 16. A process according to any one of claims 1 to 13, wherein the N-alkylamide products have a molecular formula B<1>-CONR<1>R<2>, wherein the group B<1> is a hydrogen atom or a hydrocarbyl group, and the groups R<1> and R<2> are linear n-alkyl groups with carbon atoms, respectively, where m and n may be identical or different. 17. A method according to any one of claims 14 to 16, wherein the number of n is equal to or greater than 7. 18. A method according to claim 16, wherein m is a number equal to or greater than 7. 19. A process according to any preceding claim, wherein the synthesis gas feed further comprises other compounds such as nitrogen, helium, argon, water, C<1>-C<4> alkanes or combinations thereof. 20. A process according to any preceding claim, wherein, after recovery of N-alkylamides from the reaction products, a stream containing unconverted reactants, solvent, unrecovered reaction products, or a combination thereof, is recycled to the reactor.