Process for producing carboxylic acids or alkyl esters

Abstract

The present invention generally relates to a gas phase process for producing carboxylic acids or alkyl esters. In one embodiment, the gas phase process for producing carboxylic acids or alkyl esters includes: (a) providing a catalyst support, the catalyst support comprising a deposit of cobalt thiocyanate on at least a portion of the catalyst support; (b) heating the catalyst support to convert the cobalt thiocyanate on the support to cobalt sulfide to form a supported cobalt sulfide catalyst; and (c) reacting an alkene gas, steam or an alkanol gas, and a carbon-containing gas in a reactor in the presence of the supported cobalt sulfide catalyst to form a product stream, the carbon-containing gas comprising carbon monoxide or a mixture of carbon monoxide and carbon dioxide, where when steam is used as a reactant, the product stream comprises carboxylic acids, and when alkanol gas is used as a reactant, the product stream comprises alkyl esters.

Description

[Technical field]

[0001] The present invention relates generally to a vapor phase process for producing carboxylic acids or alkyl esters. [Background technology]

[0002] Carboxylic acids, such as propionic acid, are important intermediates for the synthesis of many oxygenates that find use in herbicides, food preservatives, plastics, plasticizers, and cosmetics.

[0003] Various methods are known for producing carboxylic acids. Taking propionic acid as an example, one commercial process relies on the liquid-phase hydrocarboxylation of ethylene. In this process, ethylene, carbon monoxide (CO), and water are directly converted to propionic acid under harsh reaction conditions (e.g., 250-320 °C and 100-300 bar) in the presence of a highly toxic Ni(CO)4 catalyst.

[0004] A second liquid-phase method for producing carboxylic acids uses olefin hydroformylation followed by oxidation of an aldehyde to produce carboxylic acid. In this commercially implemented two-step reaction process for producing propionic acid, propanal is produced in the first step via hydroformylation of ethylene, and propanal is oxidized to propionic acid in the second step (Ullmann's Encyclopedia of Industrial Chemistry, Vol. 30, pp. 295-311 (2012)).

[0005] Another route to produce carboxylic acids is the direct oxidation of hydrocarbons (“Ullmann's Encyclopedia of Industrial Chemistry” Vol. 30, pp. 295-311 (2012)). Direct oxidation of hydrocarbons can also be used to produce propionic acid as a by-product during the synthesis of acetic acid from naphtha (“Ullmann's Encyclopedia of Industrial Chemistry” Vol. 30, pp. 295-311 (2012)).

[0006] The liquid phase, single-step hydrocarboxylation of ethylene has advantages in ethylene yield compared to the two-step hydroformylation / oxidation route, but industrial use has proven limited due to the costs and risks associated with operating high-pressure reactors using corrosive and toxic nickel carbonyl catalysts.

[0007] The processes listed above concern reactions in the liquid phase. There is limited published literature on gas-phase hydrocarboxylation. Early studies described the formation of carboxylic acids by mixing water vapor with CO and olefins. Examples of catalysts are charcoal (see U.S. Pat. No. 2,089,903), ZnCl (see U.S. Pat. No. 1,924,767) and tungsten oxide (see U.S. Pat. No. 2,008,348), and in all cases the catalyst was used in combination with a metal halide. These studies indicate a pressure range of 25-900 atm, although examples are carried out at 600-700 atm.

[0008] No. 3,501,518 discloses that the carbonylation reaction can be activated by Pd sulfide. The reaction is carried out in the liquid phase at temperatures ranging from 30 to 180° C. and pressures ranging from 5 to 100 MPa (49 to 987 atm), and requires the addition of a halide or a cocatalyst, such as an acid and an organic phosphine or nitrile.

[0009] Recently, US Patent No. 10,144,693 disclosed an improved gas-phase hydrocarboxylation process using Group VIII metal sulfide catalysts. This included bulk and supported catalysts that enable high propionic acid selectivity. US Patent No. 10,144,693 also described a method for preparing a cobalt sulfide catalyst.

[0010] Alkyl esters such as methyl propionate, n-propyl propionate, n-butyl propionate, and n-pentyl propionate are important solvents that find use in lacquers, inks, paints, coatings, films, and fragrances, among other applications.

[0011] Various methods are known for producing alkyl esters of aliphatic carboxylic acids, such as methyl methacrylate (MMA). One commercial process relies solely on acetone cyanohydrin (ACH) technology, i.e., reacting acetone with hydrogen cyanide to form ACH, followed by acid-assisted hydrolysis and esterification with methanol to produce approximately 400 kilotons of MMA per year. While the ACH route has traditionally been the core technology used in the United States and other parts of the world, lower-cost alternatives are being considered for future capacity growth. Some of these alternatives are ethylene-based. One such method is the hydroformylation of ethylene to propionaldehyde, followed by condensation to form methacrolein (MA), and then oxidation and esterification to form MMA. Another route is the Alpha Process, a two-stage liquid-phase process that uses a homogeneous palladium-based catalyst to make methyl propionate, which is then condensed with formaldehyde in a second step to make MMA. This process is described in WO 1999 / 021820. Other reports of homogeneous catalysts for the liquid phase carbonylation of ethylene to methyl propionate include U.S. Pat. No. 3,507,891 (cobalt-pyridine catalyst), Chem. Commun., 2001, 47-48 (rhodium / b-ketophosphine catalyst), and J. Molecular Catalysis 40 (1987) 243-254, Hidai et al. (ruthenium-iodide catalyst).

[0012] One report of heterogeneous catalysis operating in the gas phase is by Bhattacharyya, S K and Nag, S N, Brennstoff-Chemie, Vol. 43, p. 114-118 (1962). This work describes the use of metal iodides supported on silica gel to synthesize methyl propionate from ethylene, CO and methanol in the gas phase. The process produces large amounts of undesirable by-product oxygenates and hydrocarbon compounds and operates at a pressure of 253 bar (25.3 MPa).

[0013] Recently, U.S. Patent No. 9,938,226 disclosed a gas phase carbonylation process for producing alkyl alkanoates using a Group VIII metal sulfide catalyst. U.S. Patent No. 9,938,226 also described a method for preparing a cobalt sulfide catalyst.

[0014] In addition to the methods for preparing cobalt sulfide catalysts described in US Patent No. 9,938,226 and US Patent No. 10,144,693, there are alternative approaches to prepare cobalt sulfide catalysts using additional organic ligands and / or air oxidation, as described in EP Patent No. 0065028(A1) and Thermochimica Acta 425(2005), pp.13-21. However, such approaches may result in undesirable Co oxides. Russian Patent No. 2677285 attempts to use CoO and convert the oxides to sulfides with hydrogen gas.

[0015] It would be desirable to have an alternative gas phase process for producing carboxylic acids and / or alkyl esters. Summary of the Invention

[0016] The present invention provides an alternative gas phase process for producing carboxylic acids and / or alkyl esters. Such a process utilizes a supported cobalt sulfide catalyst prepared in a manner that offers many advantages. For example, the process is versatile and in some embodiments can allow for the preparation of catalysts using a variety of supports such as Al2O3, SiO2, carbon, and SiC. In some embodiments, the carbonylation reaction can surprisingly proceed using the cobalt sulfide catalyst without the need for halides or other cocatalysts and can proceed at moderate pressures. In some embodiments, the cobalt sulfide catalyst can show promising performance in direct propionic acid synthesis achieving high selectivity of over 98% and productivity comparable to or exceeding that of conventional bulk cobalt sulfide catalysts.

[0017] In one aspect, a gas phase process for producing carboxylic acids or alkyl esters comprises: (a) providing a catalyst support, the catalyst support comprising a deposit of cobalt thiocyanate on at least a portion of the catalyst support, the catalyst support having a thickness of 5 mm or less; 2 / g or more; (b) heating the catalyst support to convert the cobalt thiocyanate on the support to cobalt sulfide to form a supported cobalt sulfide catalyst; (c) reacting an alkene gas, water vapor or alkanol gas, and a carbon-containing gas in a reactor in the presence of a supported cobalt sulfide catalyst to form a product stream, wherein the carbon-containing gas comprises carbon monoxide or a mixture of carbon monoxide and carbon dioxide; When steam is used as a reactant, the product stream comprises carboxylic acids, and when alkanol gas is used as a reactant, the product stream comprises alkyl esters.

[0018] These and other embodiments are described in greater detail in the Detailed Description. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present disclosure generally relates to a gas phase process for producing carboxylic acids or alkyl esters. The process utilizes supported cobalt sulfide, which is prepared in a manner that offers many advantages. In general, a catalyst support is provided with a deposit of cobalt thiocyanate on at least a portion thereof, and then heated to convert the cobalt thiocyanate on the support to cobalt sulfide to form a supported cobalt sulfide catalyst. As further described herein, such supported cobalt sulfide catalysts perform well in the synthesis of carboxylic acids and alkyl esters, achieving high selectivity and productivity, especially when compared to conventional bulk cobalt sulfide catalysts.

[0020] All references to the Periodic Table of the Elements are to the CRC Handbook of Chemistry and Physics, 71 st Ed. (1990-1991), pages 1-10. Also, any reference to a group is to that group as reflected in the Periodic Table of the Elements using the IUPAC system for numbering groups. Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percentages are by weight and all test methods are current as of the filing date of this disclosure. For purposes of U.S. patent practice, the contents of any patent, patent application, or publication referenced are incorporated by reference (or the U.S. equivalent thereof is so incorporated by reference in its entirety), particularly with respect to disclosures of synthesis techniques, product and process designs, polymers, catalysts, definitions (to the extent not inconsistent with any definitions specifically provided in this disclosure), and general knowledge in the art.

[0021] Numerical ranges in this disclosure are approximations and therefore may include values ​​outside the range unless otherwise indicated. Numerical ranges include all values ​​including lower and upper limits in increments of one unit, provided that there is a separation of at least two units between any lower limit and any upper limit. As an example, if a compositional, physical, or other property, such as molecular weight, weight percent, is 100 to 1,000, all individual values ​​such as 100, 101, 102, etc., and subranges such as 100 to 144, 155 to 170, 197 to 200, etc., are intended to be explicitly recited. For ranges containing values ​​that are less than 1 or containing fractions greater than 1 (e.g., 1.1, 1.5, etc.), a unit is considered to be 0.0001, 0.001, 0.01, or 0.1, as appropriate. For ranges containing single digit numbers with fewer than 10 digits (e.g., 1 to 5), a unit is typically considered to be 0.1. These are merely examples of what is specifically intended, and all possible combinations of numerical values ​​between the lowest and highest values ​​recited should be considered to be expressly set forth in this disclosure. Numerical ranges are provided within this disclosure for, inter alia, the amounts of the various reactants in the inventive process and the operating conditions of the inventive process.

[0022] As used herein, "a", "an", "the", "at least one", and "one or more" are used interchangeably. The terms "comprise", "include", and variations thereof do not have a limiting meaning when these terms appear in the specification and claims. Thus, for example, an aqueous composition comprising "a" hydrophobic polymer particle can be interpreted to mean that the composition comprises "one or more" hydrophobic polymer particles.

[0023] As used herein, the term "ppmw" means parts per million by weight. When used to assess the concentration of weakly basic amines, the phrase "ppmw (nitrogen basis)" is based on the weight of the amine nitrogen divided by the total weight of the mixture. This makes the analysis independent of the molecular weight of the amine and focuses on the active groups on the weakly basic amine. The amine nitrogen does not include nitrogen moieties that cannot react with acids, such as quaternary amines.

[0024] "Composition" and like terms mean a mixture or blend of two or more components.

[0025] "Hydroxycarbonylation conditions" and like terms refer to the temperature, pressure and other conditions necessary for an alkene, carbon monoxide and water (one or more of which are at least partially in gaseous form) to react with one another on and in contact with the solid sulfide-containing catalyst to form a carboxylic acid. In one embodiment, each of the alkene, CO, and water is at least partially in gaseous form. In one embodiment, each of the alkene, CO, and water is completely or nearly completely in gaseous form.

[0026] "Halogen-free hydroxycarbonylation conditions" and similar terms refer to hydroxycarbonylation conditions in which any form of halogen is absent or essentially absent in the space in which the alkene, CO, and water contact over the sulfide-containing catalyst to form the carboxylic acid. "Essentially absent," in the context of halogen, means that any halogen present in the reaction space is present in an amount that does not substantially affect the conversion or selectivity of the reactants to the desired carboxylic acid. Such sources of halogen can be, for example, from one or more of the feeds to the reaction or catalyst (e.g., as contaminants), or from the surface of a portion of the equipment, and the like. In one embodiment, "halogen-free" means less than 1000 parts per million (ppm), preferably less than 10 ppm, and more preferably less than 1 ppm, based on the total weight of the reactants.

[0027] "Carbonylation conditions" and like terms refer to the temperature, pressure, and other conditions necessary for the alkene, carbon monoxide, and alkanol (one or more of which are at least partially in gaseous form) to react with each other on and in contact with the solid sulfide-containing catalyst to form an alkyl alkanoate. In one embodiment, each of the alkene, CO, and alkanol is at least partially in gaseous form. In one embodiment, each of the alkene, CO, and alkanol is completely or nearly completely in gaseous form.

[0028] "Halogen-free carbonylation conditions" and similar terms refer to carbonylation conditions in which any form of halogen is absent or essentially absent in the space in which the alkene, CO, and alkanol contact over the sulfide-containing catalyst to form the alkyl alkanoate. "Essentially absent" means that any halogen present in the reaction space is present in an amount that does not substantially affect the conversion or selectivity of the reactants to the desired alkyl alkanoate. Such sources of halogen can be, for example, from one or more of the feeds to the reaction or catalyst (e.g., as contaminants), or from a surface of a portion of the equipment, etc. In one embodiment, "halogen-free" means less than 1000 parts per million (ppm), preferably less than 10 ppm, more preferably less than 1 ppm, based on the total weight of the reactants.

[0029] "Condensation conditions" and like terms refer to the temperature, pressure and other conditions necessary for an alkyl alkanoate and an aldehyde, each in gaseous form, to react with each other on and in contact with a solid condensation catalyst to form an alkyl ester of an aliphatic carboxylic acid.

[0030] In one aspect, a gas phase process for producing a carboxylic acid or alkyl ester includes (a) providing a catalyst support, the catalyst support comprising a deposit of cobalt thiocyanate on at least a portion of the catalyst support, the catalyst support having a concentration of 5 μm or more. 2(b) heating the catalyst support to convert the cobalt thiocyanate on the support to cobalt sulfide to form a supported cobalt sulfide catalyst; and (c) reacting an alkene gas, water vapor or an alkanol gas, and a carbon-containing gas in a reactor in the presence of the supported cobalt sulfide catalyst to form a product stream, wherein the carbon-containing gas comprises carbon monoxide or a mixture of carbon monoxide and carbon dioxide, wherein when water vapor is used as a reactant, the product stream comprises a carboxylic acid, and when an alkanol gas is used as a reactant, the product stream comprises an alkyl ester.

[0031] In some embodiments, the catalyst support comprising a deposit of cobalt thiocyanate on at least a portion of the catalyst support is formed by contacting the catalyst support with an aqueous solution of a cobalt (II) salt in the presence of thiocyanate anion to deposit the aqueous solution on at least a portion of the catalyst support. Thus, in some embodiments, the process further comprises contacting the catalyst support with an aqueous solution of a cobalt (II) salt in the presence of thiocyanate anion to deposit the aqueous solution on at least a portion of the catalyst support to form the catalyst support comprising a deposit of cobalt thiocyanate. In some embodiments, the cobalt (II) salt in the presence of thiocyanate anion is provided by first dissolving cobalt thiosulfate in water. In such embodiments, the process further comprises dissolving cobalt thiosulfate in water to provide an aqueous solution of cobalt (II) salt in the presence of thiocyanate anion. This is particularly advantageous over providing cobalt in one compound and thiocyanate in another compound, since such an approach requires removal of anions associated with cobalt and cations associated with thiocyanate. In some embodiments, the aqueous solution does not contain more than 0.1 molar equivalents of cations other than cobalt(II) relative to cobalt, and the aqueous solution does not contain more than 0.1 molar equivalents of anions other than thiocyanate anion relative to thiocyanate.

[0032] When the catalyst support is heated to convert the cobalt thiocyanate on the support to cobalt sulfide to form the supported cobalt sulfide catalyst, in some embodiments the catalyst support is heated at a temperature between 200°C and 550°C.

[0033] In some embodiments, the process of the present invention further comprises drying the catalyst support comprising a deposit of cobalt thiocyanate on at least a portion of the catalyst support at a temperature of 150° C. or less under inert conditions prior to heating the catalyst support to convert the cobalt thiocyanate on the support to cobalt sulfide to form a supported cobalt sulfide catalyst.

[0034] In some embodiments, the catalyst support is heated to convert the cobalt thiocyanate on the support to cobalt sulfide to form the supported cobalt sulfide catalyst outside of the reactor, and the process further comprises adding the supported cobalt sulfide catalyst to the reactor, In other embodiments, the catalyst support is heated within the reactor to convert the cobalt thiocyanate on the support to cobalt sulfide to form the supported cobalt sulfide catalyst.

[0035] In some embodiments, the process of the invention further comprises passivating the supported cobalt sulfide catalyst with a dilute oxygen stream containing up to 2 volume percent O2 at a temperature of 25° C. or less. In some embodiments, for example, when the supported cobalt sulfide catalyst is formed in the reactor, the passivation step may not be required.

[0036] In some embodiments, the alkene gas is ethylene.

[0037] In some embodiments, the films of the present invention are continuous.

[0038] In some embodiments where the product stream comprises a carboxylic acid, the carboxylic acid selectivity is 80 mole % or greater. In some embodiments where the product stream comprises an alkyl ester, the alkyl ester selectivity is 80 mole % or greater.

[0039] In some embodiments, the reaction to form a carboxylic acid or alkyl ester (e.g., reacting an alkene gas, water vapor or alkanol gas, and a carbon-containing gas in the presence of a supported cobalt sulfide catalyst to form a product stream) occurs in a reactor at a pressure between 0.1 MPa and 10 MPa.

[0040] Supported cobalt sulfide catalyst The catalyst used in the gas phase process of the present invention is a supported metal sulfide catalyst.

[0041] The supported cobalt sulfide catalysts used in embodiments of the present invention can be advantageously made by first forming a catalyst support that includes a deposit of cobalt thiocyanate on at least a portion of the catalyst support. In various embodiments, a variety of catalyst supports can be used. In general, the catalyst support should have sufficient mechanical strength and surface properties for use in the reaction conditions described herein. In terms of mechanical strength, in some embodiments, the catalyst support has a crush strength of greater than 2 pounds per millimeter. In terms of surface area, the catalyst support can have a surface area of ​​greater than 5 m. 2 In some embodiments, the catalyst support has a surface area of ​​10 m 2 / g or more, in the preferred embodiment 50m 2 / g or more, in a more preferred embodiment 100m 2 In some embodiments, the surface area of ​​the catalyst support is greater than 10 m 2 / g~maximum 800m 2 / g. As used herein, the surface area of ​​the catalyst support is measured by nitrogen adsorption at 77.4 K using conventional techniques on a Micromeritics ASAP 2420 instrument. Prior to the adsorption measurements, the samples are degassed in vacuum at 300° C. for at least 3 hours. Surface area is calculated using the BET method known to those skilled in the art.

[0042] In some embodiments, the catalyst support can be alumina, carbon, silicon carbide, silica, silica-alumina, halfnia, zirconia, titania, and mixtures thereof.

[0043] The catalyst support is then contacted with an aqueous solution of a cobalt (II) salt in the presence of thiocyanate anions to deposit the aqueous solution on at least a portion of the catalyst support. In some embodiments, cobalt thiosulfate is first dissolved in water to provide an aqueous solution of a cobalt (II) salt in the presence of thiocyanate anions, which is contacted with the catalyst support.

[0044] The cobalt (II) salt in the presence of thiocyanate anion is provided by first dissolving cobalt thiosulfate in water. In such an embodiment, the process further comprises dissolving cobalt thiosulfate in water to provide an aqueous solution of cobalt (II) salt in the presence of thiocyanate anion. This is particularly advantageous over providing cobalt in one compound and thiocyanate in another compound, because such an approach requires removal of the anion associated with cobalt and the cation associated with thiocyanate.

[0045] Once contacted with an aqueous solution of a cobalt(II) salt in the presence of thiocyanate anion, the coated catalyst support can be dried to remove substantially all of the water. For example, in some embodiments, the coated catalyst support can be dried at a temperature less than 150° C. for 2 to 5 hours under inert conditions. Once dried, the catalyst support includes a deposit of cobalt thiocyanate on at least a portion of the catalyst support.

[0046] The catalyst support containing the cobalt thiocyanate deposit is then heated to convert the cobalt thiocyanate on the support to cobalt sulfide to form a supported cobalt sulfide catalyst. In some embodiments, the catalyst support is heated at a temperature between 200° C. and 550° C. to convert the cobalt thiocyanate to cobalt sulfide. In some embodiments, the catalyst support is heated to convert the cobalt thiocyanate on the support to cobalt sulfide in an inert gas stream at a temperature between 200° C. and 550° C. In some embodiments, the catalyst support can be heated within the reactor (where a carboxylic acid or alkyl ester is formed) to convert the cobalt thiocyanate on the support to cobalt sulfide. In other embodiments, the catalyst support can be heated outside the reactor and then provided to the reactor at an appropriate time for use in the reaction.

[0047] In some embodiments, the process of the invention further comprises passivating the supported cobalt sulfide catalyst with a dilute oxygen stream containing up to 2 volume percent O2 at a temperature of 25° C. or less. Passivating the supported cobalt sulfide catalyst can help avoid over-oxidation of the cobalt sulfide particles and protect the catalyst prior to use. In some embodiments, for example, when the supported cobalt sulfide catalyst is formed in the reactor, the passivation step may not be required.

[0048] Cobalt sulfide can include multiple phases. In some embodiments, cobalt sulfide can be CoS2, Co4S3, Co3S4, CoS, Co7S8, Co9S8, Co 1-x S, where x is 0.2 or less, or a combination thereof. While much of the cobalt sulfide on the catalyst support may be crystalline, in some embodiments, at least a portion of the cobalt sulfide may be amorphous.

[0049] In some embodiments, the catalyst support comprises alumina, carbon, silicon carbide, silica, silica-alumina, ferrous oxide, zirconia, titania, or mixtures thereof.

[0050] In some embodiments, the bulk sulfur to cobalt atomic ratio in the cobalt sulfide is 0.3 or greater. In some embodiments, the bulk sulfur to cobalt atomic ratio in the cobalt sulfide is 0.75 or greater. In some embodiments, the bulk sulfur to cobalt atomic ratio in the cobalt sulfide is up to 2.0.

[0051] In some embodiments, the cobalt content in the supported cobalt sulfide catalyst is from 5 weight percent to 50 weight percent, based on the total weight of the supported cobalt sulfide catalyst.

[0052] In some embodiments, the cobalt oxide content in the supported cobalt sulfide catalyst is less than 5 weight percent based on the total content of cobalt oxide and cobalt sulfide.

[0053] Production of Carboxylic Acids Reactants In the production of carboxylic acids according to some embodiments of the gas phase process of the present invention, the reactants are an alkene gas, water vapor (i.e., gaseous water), and a carbon-containing gas, the carbon-containing gas comprising carbon monoxide or a mixture of carbon monoxide and carbon dioxide. The alkene gas can be either a monoolefin or a polyolefin, i.e., containing two or more double bonds. The monoolefin alkene can be represented by the formula C n H 2n where n is an integer greater than 1, typically 2 to 8, more typically 2 to 6. In some embodiments, n is 2 (i.e., the alkene is ethylene). In some embodiments, mixtures of alkenes can be used. For example, commercially available alpha-olefins containing 4 or more carbon atoms may contain small amounts of the corresponding internal olefins and / or their corresponding saturated hydrocarbons, and such commercially available alkenes do not necessarily need to be purified therefrom prior to use.

[0054] The carbon-containing gas may be carbon monoxide or a mixture of carbon monoxide and carbon dioxide. In some embodiments, the carbon-containing gas is carbon monoxide. In such embodiments, carbon monoxide may be used as is or in combination with one or more other gases that are inert to the reaction reagents, products, and by-products under the reaction conditions. Such other gases include, but are not limited to, nitrogen and the noble gases.

[0055] The terms "alkene" and "olefin" are used interchangeably herein. Exemplary alpha and internal olefins include, for example, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 2-butene, 2-methylpropene (isobutylene), 2-methylbutene, 2-pentene, 2-hexene, 3-hexene, 2-heptene, cyclohexene, butadiene, styrene, 1,4-hexadiene, 1,7-octadiene, as well as alkyl alkenoates, alkenyl alkanoates, alkenyl alkyl ethers, alkenols, alkenals, and the like. As with carbon monoxide, alkenes may contain other compounds, such as impurities and contaminants. In the case of alkenes, some of these compounds may be present as a result of the process in which the alkene was formed. For example, methane-containing sources, such as shale gas or natural gas, can be converted to alkenes by techniques well known to those skilled in the art. Depending on the alkene production process, by-products such as CO, H2, CO2, and / or others may be present in the alkene. Thus, in some embodiments, the gas phase process of the invention comprises producing carboxylic acids by contacting an alkene gas, carbon monoxide gas, water vapor, and a supported cobalt sulfide catalyst under halogen-free hydroxycarbonylation conditions at a temperature greater than 250° C. to 400° C., where the alkene, preferably ethylene, is derived from a methane-containing source such as shale gas or natural gas.

[0056] The water (liquid or gas) may be pure or diluted, in some embodiments, the water may be provided at least in part by any precursor that provides water, including alcohols, acids, and other oxygenates.

[0057] catalyst The catalyst used in the reaction is the supported cobalt sulfide catalyst described above.

[0058] Process conditions and equipment The process of the present invention is carried out in the gas phase over a solid catalyst. Thus, in one embodiment, the alkene, the carbon-containing gas (e.g., CO) and water are introduced as gases and contact each other over and in contact with the solid catalyst bed. The reactants can be introduced in a single or multiple feed streams. In an embodiment in which the carbon-containing gas comprises carbon monoxide, the molar ratio of CO to alkene is typically at least 1:1, typically at least 3:1, more typically from 3:1 to 50:1, even more typically from 3:1 to 15:1. The molar ratio of alkene to steam is typically at least 0.1:1, more typically at least 0.5:1, more typically from 0.1:1 to 10:1, even more typically from 0.2:1 to 2:1.

[0059] The process can be operated in either continuous or batch mode, although the process is preferably operated in continuous mode.

[0060] The process temperature may be greater than 250° C. to 450° C., 260° C. to 400° C., or 280° C. to 350° C. The total pressure of the process may be 0.1 to 30 MPa, or 1.5 to 6 MPa. The gas hourly space velocity of the process is typically 100 to 1,000,000 liters of gas feed per liter of catalyst per hour (L / L*hr), more typically 500 to 5,000 L / L*hr.

[0061] In one embodiment, the reaction is carried out in a fixed bed reactor. In one embodiment, the reactor is a tubular reactor. In a typical protocol, the temperature and pressure are slowly increased to the reaction conditions. The catalyst can be exposed to a feed that includes an inert gas (such as nitrogen or helium), carbon monoxide, an alkene, water, optionally a small amount of a sulfur-containing gas such as H2S, and any combination of the above. Examples of other sulfur-containing gases include, but are not limited to, mercaptans, thiophenes, dimethyl sulfide, and dimethyl disulfide. The feed gas may also include impurities or contaminants, such as hydrogen. The effluent gas from the reactor can be analyzed by gas chromatography (GC) to determine the product composition and the amount of CO converted.

[0062] Production of alkyl esters Reactants In producing alkyl esters according to some embodiments of the gas phase process of the present invention, the reactants are an alkene gas, an alkanol gas, and a carbon-containing gas, the carbon-containing gas comprising carbon monoxide or a mixture of carbon monoxide and carbon dioxide. The alkene gas can be represented by the formula C n H 2n where n is an integer greater than (>) 1, typically 2 to 8, more typically 2 to 6. In some embodiments, n is 2 (i.e., the alkene is ethylene). In some embodiments, mixtures of alkenes can be used. For example, commercially available alpha-olefins containing 4 or more carbon atoms may contain small amounts of the corresponding internal olefins and / or their corresponding saturated hydrocarbons, and such commercially available alkenes do not necessarily need to be purified therefrom prior to use.

[0063] The carbon-containing gas may be carbon monoxide or a mixture of carbon monoxide and carbon dioxide. In some embodiments, the carbon-containing gas is carbon monoxide. In such embodiments, carbon monoxide may be used as is or in combination with one or more other gases that are inert to the reaction reagents, products, and by-products under the reaction conditions. Such other gases include, but are not limited to, nitrogen and the noble gases.

[0064] Alkanol (i.e., alcohol) gases are typically C 2 O 4 which may contain one or more substituents such as cyano, carbonyl, alkoxy or aryl groups. 1~8 Alkanol. Exemplary alkanols include, but are not limited to, methanol, ethanol, propanol, 2-propanol, 2-butanol, t-butyl alcohol, and capryl alcohol. For purposes of the present invention, polyhydroxyl compounds (e.g., diols and sugars) are considered alkanols that may be used in the practice of the present invention. Methanol is a particularly useful alkanol in some embodiments.

[0065] catalyst The catalyst used in the reaction is the supported cobalt sulfide catalyst described above.

[0066] Process conditions and equipment The process of the present invention is carried out in the gas phase over a solid catalyst. Thus, in one embodiment, the alkene, the carbon-containing gas (e.g., CO), and the alkanol are introduced as gases and contact each other over and in contact with the solid catalyst bed. The reactants can be introduced in a single or multiple feed streams. In an embodiment in which the carbon-containing gas comprises carbon monoxide, the molar ratio of CO to alkene is typically at least 1:1, typically at least 3:1, more typically from 3:1 to 50:1, even more typically from 3:1 to 15:1. The molar ratio of alkene to alkanol is typically at least 0.1:1, more typically at least 0.5:1, more typically from 0.1:1 to 10:1, even more typically from 0.2:1 to 2:1.

[0067] The process can be operated in either continuous or batch mode, although the process is typically and preferably operated in continuous mode.

[0068] The process temperature is typically from 120° C. to 450° C., more typically from 250° C. to 380° C., and even more typically from 280° C. to 340° C. The total process pressure is typically from 0.1 to 20 MPa, more typically from 1.5 to 6 MPa. The space velocity of the process is typically from 100 to 1,000,000 liters of gas feed per liter of catalyst per hour (L / L*hr), more typically from 500 to 5,000 L / L*hr.

[0069] In one embodiment, the reaction is carried out in a high pressure fixed bed reactor. In one embodiment, the reactor is a tubular reactor. In a typical protocol, the temperature and pressure are slowly increased to the reaction conditions. The catalyst can be exposed to a feed consisting of an inert gas (such as nitrogen or helium), hydrogen, small amounts of H2S, carbon monoxide, olefins, alkanols, and any combination of the above. The effluent gas from the reactor is analyzed by gas chromatography (GC) to determine the product composition and the amount of CO converted.

[0070] In one embodiment of the gas phase process of the invention, ethylene, CO, and methanol are contacted under carbonylation conditions over and in contact with a supported cobalt sulfide catalyst to form methyl propionate.

[0071] Preparation of alkyl esters of aliphatic carboxylic acids In one embodiment of the present invention, the alkyl ester produced in the gas phase process described above is condensed with an aldehyde to form an alkyl ester of an aliphatic carboxylic acid. When the alkyl ester is methyl propionate and the aldehyde is formaldehyde, the product is methyl methacrylate (MMA). The equipment, conditions and protocols for this condensation reaction are well known to those skilled in the art.

[0072] Some embodiments of the invention are described in more detail in the following examples. EXAMPLES

[0073] All parts and percentages in the following examples are by weight unless otherwise indicated. Pressures are listed as absolute pressures unless otherwise indicated.

[0074] Catalyst synthesis A number of catalysts have been synthesized as described. The catalysts described as examples of the present invention can be used in gas phase processes according to some embodiments of the present invention.

[0075] Example 1 of the present invention Catalyst Co X S y Al2O3 is prepared by incipient wetness impregnation method. An impregnation solution of cobalt(II) thiocyanate in deionized water is prepared at a concentration of 2 molar. Then, 7.86 grams of 40-80 mesh size Al2O3 support (NORPRO SA31132) is placed in a porcelain dish and 7.86 milliliters of the impregnation solution is added dropwise with gentle shaking. The properties of the support are shown in Tables 1a-1b.

[0076] In Tables 1a-1b, the surface areas of the supports are measured by nitrogen adsorption at 77.4 K using conventional techniques on a Micromeritics ASAP2420 instrument. Prior to the adsorption measurements, the samples are degassed in vacuum at 300° C. for at least 3 hours. The surface areas are calculated using the BET method known to those skilled in the art.

[0077] The porcelain dish with the impregnated catalyst is placed in a stainless steel drum, where the catalyst is dried and autoreduced in a stream of pure N2 (overhead flow 5.5 L / min) using the following procedure: run the N2 stream at room temperature for 30 minutes, ramp from room temperature to 120°C at 2°C / min, dwell at 120°C for 2 hours, ramp from 120 to 550°C at 3°C / min, dwell at 550°C for 4 hours, and cool to room temperature 20-25°C (24-48 hours). The catalyst is then passivated in a 1% by volume O2 / N2 stream at room temperature (20-25°C) for 2 hours, then the oxygen concentration in the gas stream is gradually increased to 21% by volume O2 / N2. Before opening the stainless steel drum, the catalyst is purged in 21% by volume O2 / N2 for 1 hour. The result is a black material. The catalyst compositions were determined by X-ray fluorescence (XRF) and X-ray diffraction (XRD) and are reported in Tables 2a-2b.

[0078] Example 2 of the present invention Catalyst Co X S y / Al2O3 is prepared by incipient wetness impregnation method. The support is Al2O3 (NORPRO SA6173, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method as used in Example 1 of the present invention is used. The mass of the support used is 9.14 grams. The volume of 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 8.226 milliliters. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0079] Example 3 of the present invention Catalyst Co X S y / Al2O3 is prepared by incipient wetness impregnation method. The support is Al2O3 (NORPRO SA6178, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method as used in Example 1 of the present invention is used. The mass of the support used is 6.8 grams. The volume of 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 5.916 milliliters. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0080] Example 4 of the present invention Catalyst Co X S y The catalyst is prepared by incipient wetness impregnation method. The support is Al2O3-SiO2 (SASOL Siralox 1.5 / 140 in powder form, support properties are reported in Tables 1a-1b). The same catalyst preparation method as used in Example 1 of the present invention is used. The mass of the support used is 10 grams. The volume of 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 9.5 milliliters. After preparation, the catalyst was pelletized, crushed and sieved to 40-80 mesh size. The catalyst composition was determined by XRF and XRD and is reported in Tables 2a-2b.

[0081] Example 5 of the present invention Catalyst Co X S y / Al2O3 is prepared by incipient wetness impregnation method. The support is Al2O3 (NORPRO SA6176, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method as used in Example 1 of the present invention is used. The mass of the support used is 10 grams. The volume of 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 11.5 milliliters. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0082] Example 6 of the present invention Catalyst Co X S y / Al2O3 is prepared by incipient wetness impregnation method. The support is basic Al2O3 doped with 4.5% CaO and 1% MgO (NORPRO SA65169, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method as used in Example 1 of the present invention is used. The mass of the support used is 10 grams. The volume of 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 10.68 milliliters. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0083] Example 7 of the present invention Catalyst Co X S y Catalyst 100 / C is prepared by incipient wetness impregnation method. The support is activated carbon (Norit GAS 610, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method as used in Example 1 of the present invention is used. The mass of the support used is 10 grams. The volume of 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 12 milliliters. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0084] Example 8 of the Invention Catalyst Co X S y Catalyst Meso-C is prepared by incipient wetness impregnation method. The support is activated carbon (Sicat Catalyst Meso-C, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method as used in Example 1 of the present invention is used. The mass of the support used is 10 grams. The volume of 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 5.2 milliliters. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0085] Example 9 of the Invention Catalyst Co X S y / SiO2 is prepared by incipient wetness impregnation method. The support is SiO2 (NORPRO SS61138, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method as used in Example 1 of the present invention is used. The mass of the support used is 5 grams. The volume of 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 6.1 milliliters. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0086] Example 10 of the Invention Catalyst Co X S y / SiO2 is prepared by incipient wetness impregnation method. The support is SiO2 (Fuji Sliysia Cariact Q20C, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method as used in Example 1 of the present invention is used. The mass of the support used is 5 grams. The volume of 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 5.1 milliliters. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0087] Example 11 of the present invention The catalyst CoXSy / SiO2 is prepared by incipient wetness impregnation method. The support is SiO2 (Fuji Sliysia Cariact Q30C, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method as used in Example 1 of the present invention is used. The mass of the support used is 5 grams. The volume of 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 6.1 milliliters. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0088] Example 12 of the Invention Catalyst Co X S y / SiO2 is prepared by incipient wetness impregnation method. The support is SiO2 (Fuji Sliysia Cariact Q40C, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method as used in Example 1 of the present invention is used. The mass of the support used is 5 grams. The volume of 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 5.1 milliliters. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0089] Example 13 of the Invention Catalyst Co X S y / SiO2 is prepared by incipient wetness impregnation method. The support is SiO2 (Fuji Sliysia Cariact Q10, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method is used as in Example 1 of the present invention. The mass of the support used is 10.2 grams. The volume of the 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 10.2 milliliters. Drying and self-reduction are performed as in Example 1, but the final calcination temperature is 400°C (4 hours) instead of 550°C. Catalyst passivation is performed as in Example 1. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0090] Example 14 of the Invention Catalyst Co X S y / SiO2 is prepared by incipient wetness impregnation method. The support is SiO2 (Fuji Sliysia Cariact Q20C, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method is used as in Example 1 of the present invention. The mass of the support used is 10.2 grams. The volume of 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 8.0 milliliters. Drying and self-reduction are performed as in Example 1, but the final calcination temperature is 400°C (4 hours) instead of 550°C. Catalyst passivation is performed as in Example 1. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0091] Example 15 of the Invention Catalyst Co X S y / Al2O3 is prepared by incipient wetness impregnation method. The support is Al2O3 (NORPRO CA 08408, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method is used as in Example 1 of the present invention. The mass of the support used is 11.8 grams. The volume of the 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 10 milliliters. Drying and self-reduction are performed as in Example 1, but the final calcination temperature is 400°C (4 hours) instead of 550°C. Catalyst passivation is performed as in Example 1. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0092] Example 16 of the Present Invention Catalyst Co X S y / SiC is prepared by incipient wetness impregnation method. The support is SiC (manufactured by SiCat Catalyst, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method is used as in Example 1 of the present invention. The mass of the support used is 10.6 grams. The volume of the 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 5 milliliters. Drying and self-reduction are performed as in Example 1, but the final calcination temperature is 400°C (4 hours) instead of 550°C. Catalyst passivation is performed as in Example 1. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0093] Example 17 of the Present Invention Catalyst Co X S y / ZrO2 is prepared by incipient wetness impregnation method. The support is ZrO2 (NORPRO SZ31164, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method is used as in Example 1 of the present invention. The mass of the support used is 11.3 grams. The volume of the 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 4 milliliters. Drying and self-reduction are performed as in Example 1, but the final calcination temperature is 400°C (4 hours) instead of 550°C. Catalyst passivation is performed as in Example 1. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0094] Example 18 of the Present Invention Catalyst Co X S yCatalyst 100 / C is prepared by incipient wetness impregnation method. The support is activated carbon (Sicat Catalyst Meso-C, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method is used as in Example 1 of the present invention. The mass of the support used is 10.22 grams. The volume of the 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 5 milliliters. Drying and self-reduction are carried out as in Example 1, but the final calcination temperature is 400°C (4 hours) instead of 550°C. Catalyst passivation is carried out as in Example 1. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0095] Example 19 of the Present Invention Catalyst Co X S y / TiO2 is prepared by incipient wetness impregnation method. The support is TiO2 (NORPRO ST31119, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method is used as in Example 1 of the present invention. The mass of the support used is 11.22 grams. The volume of the 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 5 milliliters. Drying and self-reduction are performed as in Example 1, but the final calcination temperature is 400°C (4 hours) instead of 550°C. Catalyst passivation is performed as in Example 1. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0096] Comparative Example 1 (Bulk Cobalt Sulfide Catalyst) The bulk cobalt sulfide catalyst with Co9S8 as the main crystalline phase is prepared by coprecipitation method using an aqueous solution of cobalt(II) acetate tetrahydrate (440 g Co(CH3COO)2·4H2O, purchased from Sigma Aldrich) and an aqueous solution of ammonium sulfide (531.7 g (NH4)2S, 20%, purchased from Sigma Aldrich) in 3200 ml H2O at 60 °C.

[0097] After precipitation, the sample is left to age at 60°C for 15 min and then cooled to room temperature. The final pH of the slurry is about 6.9. The resulting precipitate is washed three times with deionized water (500 mL for each wash) and centrifuged at 6000 rpm for 15 min. The sample is then dried overnight (18 h) at 60°C in a vacuum oven and heat treated at 550°C for 1 h in a tube furnace under N2 flow of 50 mL / min, followed by passivation with 1% O2 / Ar for 2 h at room temperature. The BET surface area of ​​this sample measured by N2ads / des is 10.7 m 2 The catalyst is Co by XRD. 1-x The catalyst contains Co9S8 and Co9S8 phases. Prior to testing, the catalyst is tableted, crushed, and sieved to 40-80 mesh size. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0098] Comparative Example 2 Catalyst Co X S y / Al2O2 is prepared by incipient wetness impregnation method. The support is Al2O3 (NORPRO SA51161, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The same catalyst preparation method as used in Example 1 of the present invention is used. The mass of the support used is 9.2 grams. The volume of 2M cobalt(II) thiocyanate solution used for incipient wetness impregnation is 4.692 milliliters. The catalyst composition is determined by XRF and XRD and is reported in Tables 2a-2b.

[0099] Comparative Example 3 Catalyst Co X S y / Al2O3 is prepared by the incipient wetness impregnation method.

[0100] Chief of Staff x Preparation of / Al2O3 First, an impregnation solution of cobalt(II) acetate in deionized water is prepared at a concentration of 1 molar (M). Then, 5 grams of 40-80 mesh size Al2O3 support (NORPRO SA31132, support properties are reported in Tables 1a-1b) is placed in a porcelain dish and 5 ml of the impregnation solution is added dropwise while gently shaking. The as-impregnated catalyst is dried in air at 120 °C in a box oven for 2 h. The impregnation is repeated two more times, drying in air after each impregnation. A total of three impregnations are performed. Total volume of 1 M cobalt(II) acetate solution used for the three incipient wetness impregnations: 15.0 ml. The impregnated catalyst is dried and calcined in air using the following program: temperature ramp from room temperature to 120°C at 2°C / min, dwell at 120°C for 2 hours, ramp from 120 to 400°C at 3°C / min, dwell at 400°C for 4 hours, cool to room temperature to obtain the supported cobalt oxide material CoO x / Al2O3 is obtained.

[0101] Chief of Staff x / Al2O3 sulfurization As-prepared CoO x / Al2O3 is sulfurized in the liquid phase using an aqueous solution of ammonium sulfide. For this purpose, 25 milliliters of deionized water and 25 milliliters of a 20% by weight aqueous solution of ammonium sulfide are added to a 250 milliliter glass beaker equipped with a magnetic stirring bar and a thermocouple. The solution is heated to 60°C and then 5 grams of CoO x Add the / Al2O3 material to the solution and stir the slurry for 20 minutes at 60°C (± 5°C). Filter the cake through a paper filter, collect it and wash with 500ml of deionized water.

[0102] The cake is dried overnight in air at room temperature. The dried cake is then placed in a stainless steel drum for drying, autoreduction and passivation. Drying and autoreduction are carried out in a flow of pure N2 (overhead flow 5.5 liters / min) using the following program: N2 flow for 30 minutes at room temperature, temperature is increased from room temperature to 120°C at 2°C / min, dwell at 120°C for 2 hours, increased from 120 to 550°C at 3°C / min, dwell at 550°C for 4 hours and cooled to room temperature 20-25°C (24-48 hours). The catalyst is then passivated in a 1% by volume O2 / N2 flow at room temperature (20-25°C) for 2 hours. The oxygen concentration in the gas flow is then gradually increased to 21% by volume O2 / N2. Before opening the stainless steel drum, the catalyst is purged in 21% by volume O2 / N2 for 1 hour. A black supported cobalt sulfide catalyst is obtained. The catalyst compositions were determined by XRF and XRD and are reported in Tables 2a-2b.

[0103] Comparative Example 4 Catalyst Co X S y / Al2O3 is prepared using the preparation method described in Comparative Example 3.

[0104] Preparation of CoOx / Al2O3 The same preparation method described in Comparative Example 3 is used in this comparative example. The support is Al2O3 (NORPRO SA6176, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The mass of support used is 5 grams. The total volume of 1M cobalt(II) acetate solution used for the three incipient wetness impregnations is 17.25 milliliters.

[0105] Sulfurization of CoOx / Al2O3 The same sulfurization method as described in Comparative Example 3 is used in this comparative example.

[0106] The catalyst compositions were determined by XRF and XRD and are reported in Tables 2a-2b.

[0107] Comparative Example 5 Catalyst Co X S y / Al2O3 is prepared using the preparation method described in Comparative Example 3.

[0108] Preparation of CoOx / Al2O3 The same preparation method described in Comparative Example 3 is used in this comparative example. The support is Al2O3 (NORPRO SA6178, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The mass of support used is 5 grams. The total volume of 1 M cobalt (II) acetate solution used for the three incipient wetness impregnations is 13.05 milliliters.

[0109] Sulfurization of CoOx / Al2O3 The same sulfurization method as described in Comparative Example 3 is used in this comparative example.

[0110] The catalyst compositions were determined by XRF and XRD and are reported in Tables 2a-2b.

[0111] Comparative Example 6 Catalyst Co X S y / SiO2 is prepared using the preparation method described in Comparative Example 3.

[0112] Preparation of CoOx / SiO2 The same preparation method described in Comparative Example 3 is used in this comparative example. The support is SiO2 (NORPRO SS61138, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The mass of support used is 5 grams. The total volume of 1M cobalt(II) acetate solution used for the three incipient wetness impregnations is 18 milliliters.

[0113] Sulfurization of CoOx / SiO2 The same sulfurization method as described in Comparative Example 3 is used in this comparative example.

[0114] The catalyst compositions were determined by XRF and XRD and are reported in Tables 2a-2b.

[0115] Comparative Example 7 Catalyst Co X S y / SiO2 is prepared using the preparation method described in Comparative Example 3.

[0116] Preparation of CoOx / SiO2 The same preparation method described in Comparative Example 3 is used in this comparative example. The support is SiO2 (Fuji Sliysia Cariact Q10, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The mass of support used is 5 grams. The total volume of 1M cobalt(II) acetate solution used for the three incipient wetness impregnations is 12.9 milliliters.

[0117] Sulfurization of CoOx / SiO2 The same sulfurization method as described in Comparative Example 3 is used in this comparative example.

[0118] The catalyst compositions were determined by XRF and XRD and are reported in Tables 2a-2b.

[0119] Comparative Example 8 Catalyst Co X S y / SiO2 is prepared using the preparation method described in Comparative Example 3.

[0120] Preparation of CoOx / SiO2 The same preparation method described in Comparative Example 3 is used in this comparative example. The support is SiO2 (Fuji Sliysia Cariact Q20C, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The mass of support used is 5 grams. The total volume of 1M cobalt(II) acetate solution used for the three incipient wetness impregnations is 15 milliliters.

[0121] Sulfurization of CoOx / SiO2 The same sulfurization method as described in Comparative Example 3 is used in this comparative example.

[0122] The catalyst compositions were determined by XRF and XRD and are reported in Tables 2a-2b.

[0123] Comparative Example 9 Using the preparation method described in Comparative Example 3, a cobalt oxide supported catalyst CoO x / Al2O3 is prepared.

[0124] The support is Al2O3 (NORPRO SA31132, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The mass of support used is 10 grams. The total volume of 1 M cobalt(II) acetate solution used for the three incipient wetness impregnations is 20 milliliters.

[0125] The catalyst compositions determined by XRF and XRD are reported in Tables 2a-2b.

[0126] Comparative Example 10 Using the preparation method described in Comparative Example 3, a cobalt oxide supported catalyst CoO x / Al2O3 is prepared.

[0127] The support is Al2O3 (NORPRO SA6176, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The mass of support used is 10 grams. The total volume of 1 M cobalt(II) acetate solution used for the two incipient wetness impregnations is 23 milliliters.

[0128] The catalyst compositions determined by XRF and XRD are reported in Tables 2a-2b.

[0129] Comparative Example 11 Using the preparation method described in Comparative Example 3, a cobalt oxide supported catalyst CoO x / Al2O3 is prepared.

[0130] The support is Al2O3 (NORPRO SA6178, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The mass of support used is 10 grams. The total volume of 1 M cobalt(II) acetate solution used for the two incipient wetness impregnations is 17.4 milliliters.

[0131] The catalyst compositions determined by XRF and XRD are reported in Tables 2a-2b.

[0132] Comparative Example 12 Using the preparation method described in Comparative Example 3, a cobalt oxide supported catalyst CoO x / Al2O3 is prepared.

[0133] The support is Al2O3-SiO2 in powder form (SASOL Siralox 1.5 / 140, support properties are reported in Tables 1a-1b). The mass of support used is 10 grams. The total volume of 1 M cobalt(II) acetate solution used for the two incipient wetness impregnations is 19 milliliters. After preparation, the catalyst is pelletized, crushed, and sieved to 40-80 mesh size.

[0134] The catalyst compositions were determined by XRF and XRD and are reported in Tables 2a-2b.

[0135] Comparative Example 13 The preparation method described in Comparative Example 3 is used to prepare the cobalt oxide supported catalyst CoOx / SiO2.

[0136] The support is SiO2 (NORPRO SS61138, support properties are reported in Tables 1a-1b). The support is crushed and sieved to 40-80 mesh size. The mass of support used is 10 grams. The total volume of 1 M cobalt(II) acetate solution used for the two incipient wetness impregnations is 24 milliliters.

[0137] The catalyst compositions were determined by XRF and XRD and are reported in Tables 2a-2b. [Table 1] *BJH adsorption average pore width (4V / A) na - not available [Table 2] *BJH adsorption average pore width (4V / A) **From the supplier nm - not measured [Table 3] *Balance-Carbon **Calculated from the amount of impregnated cobalt and the S / Co ratio determined by XRF ***Two phases of cobalt sulfide were detected by XRD. 1-x S and Co9S8 are in a ratio of approximately 1:1 wt / wt. ^Sample composition derived from XRD. [Table 4] *Balance-Carbon **Calculated from the amount of impregnated cobalt and the S / Co ratio determined by XRF ***Two phases of cobalt sulfide were detected by XRD. 1-x S and Co9S8 are in a ratio of approximately 1:1 wt / wt. ^Sample composition derived from XRD.

[0138] Catalyst Tests of Examples 1 to 19 of the Invention and Comparative Examples 1 to 13 Kinetic measurements Kinetic measurements of the cobalt sulfide catalyst are evaluated using a fixed bed reactor under the conditions specified in Table 3. The reactor is loaded with 1 gram size catalyst (40-80 mesh) and the catalyst bed is sandwiched between layers of 20-40 mesh quartz chips. The reactor is leak tested under N2 at 750 psig and then started up by flowing a dry reactant gas feed containing 8% ethylene, 56% CO and 16% N2 at a flow rate of 50 standard cubic centimeters per minute (sccm). A liquid water feed is introduced at a rate of 2.5 milligrams per minute at >150°C, which results in a feed composition as follows: ethylene / CO / water / N2 (vol %) in the total gas stream = 7.5% / 53.5% / 5.9% / bal. For conditions 1 and 2 in Table 3, the start of the reaction is considered when the reaction temperature reaches 270°C. The catalyst is first tested at 270°C for several hours (condition 1), then at 290°C (condition 2). For conditions 3-5 in Table 3, the start of the reaction is considered to be when the reaction temperature reaches 250°C. The catalyst is first tested at 250°C for several hours (condition 3), then at 270°C for several hours (condition 4), then at 290°C for several hours (condition 5).

[0139] X-Ray Fluorescence (XRF) Measurement X-ray fluorescence (XRF) data are collected at room temperature (RT) with a PANalytical PW4400 spectrometer using an X-ray tube with a rhodium anode.

[0140] Powder X-ray Diffraction (XRD) P-XRD measurements are performed at ambient laboratory conditions on a Bruker AXS diffractometer D8 Discover equipped with a General Area Diffraction Detector System (GADDS) using Cu Kα (λ=1.5406 Å). The 2-theta range of 9-70° is recorded with an integration step size of 0.05°. XRD patterns are after 2-theta calibration against a reference standard (Al2O3 corundum, PDF#00-046-1212).

[0141] The reference numbers used for the cobalt sulfide phases are as follows: Co 1-x S(“Co7S8”)-PDF#00-042-0826,04-022-8171 Co9S8-PDF#01-073-6395,04-004-4525 CoS-PDF#01-075-0605,03-065-3418 CoS2-PDF#04-004-6455 Co4S3-PDF#00-030-0458 (cubic crystal), 00-002-1458 (hexagonal crystal) Co3S4-PDF#04-006-5317 Co3O4-PDF#00-042-1467 CoO-PDF#01-076-3832 The results are shown in Tables 4 to 6.

[0142] Examples 1-19 of the present invention demonstrate that supported cobalt sulfide catalysts can be prepared by incipient wetness impregnation followed by thermal decomposition of cobalt(II) thiocyanate under inert conditions. When used in some embodiments of the gas phase process of the present invention, the as-prepared catalysts show high selectivity towards propionic acid. This preparation method is versatile, allowing for the preparation of catalysts across different classes of supports; alumina, silica, carbon, etc.

[0143] Comparative Example 1 is a bulk cobalt sulfide catalyst. Comparison of the inventive examples with Comparative Example 1 demonstrates that comparable activity and selectivity performance of the supported catalyst can be achieved with lower cobalt loading in the supported catalyst according to some embodiments of the invention (<15 wt% Co) compared to the bulk catalyst (67.4 wt% Co).

[0144] Comparative Example 2 demonstrates that not all supports are suitable for the preparation of cobalt sulfide catalysts according to some embodiments of the present invention. Comparative Example 2 demonstrates that low surface area (<5 m), such as alpha alumina, is not a suitable support for the preparation of cobalt sulfide catalysts according to some embodiments of the present invention. 2The results show that oxide supports having a Cd content of 0.1 wt. / g result in less active catalysts, possibly due to the formation of large cobalt sulfide crystallites.

[0145] Comparative Examples 3-8 show that supported cobalt sulfide catalysts prepared by sulfiding cobalt oxide and self-reduced at 550° C. have lower activity compared to catalysts prepared according to some embodiments of the present invention.

[0146] Comparative Examples 9-13 show that other classes of catalysts (ie, supported cobalt oxide) are not active in the Direct Synthesis of Propionic Acid.

[0147] Calculation of catalytic performance of examples of the present invention and comparative examples Carbon balance is defined and calculated as follows:

number

number

number

Claims

Claim 1 A gas phase process for producing a carboxylic acid or an alkyl ester, comprising: (a) providing a catalyst support, wherein the catalyst support includes a deposit of cobalt thiocyanate on at least a part of the catalyst support, and the catalyst support has a surface area of more than 5 m ２ / g, and providing; (b) heating the catalyst support to convert the cobalt thiocyanate thereon to cobalt sulfide to form a supported cobalt sulfide catalyst; (c) reacting an alkene gas, steam or an alkanol gas, and a carbon-containing gas in a reactor in the presence of the supported cobalt sulfide catalyst to form a product stream, wherein the carbon-containing gas comprises carbon monoxide or a mixture of carbon monoxide and carbon dioxide; wherein when steam is used as a reactant, the product stream comprises a carboxylic acid, and when an alkanol gas is used as a reactant, the product stream comprises an alkyl ester. Claim 2 The process according to claim 1, wherein the catalyst support comprising a deposit of cobalt thiocyanate on at least a portion of the catalyst support is formed by contacting an aqueous solution of a cobalt (II) salt with the catalyst support in the presence of thiocyanate anions and depositing the aqueous solution on at least a portion of the catalyst support. Claim 3 The process according to claim 1 or 2, further comprising dissolving cobalt thiosulfate in water to provide the aqueous solution of the cobalt (II) salt in the presence of thiocyanate anions. Claim 4 The process according to claim 1 or 2, wherein the aqueous solution does not contain cations other than cobalt (II) in an amount exceeding 0.1 molar equivalent relative to cobalt, and the aqueous solution does not contain anions other than thiocyanate anions in an amount exceeding 0.1 molar equivalent relative to thiocyanate. Claim 5 The process according to claim 1 or 2, wherein the catalyst support is heated at a temperature of 200°C to 550°C. Claim 6 The process according to claim 1 or 2, further comprising drying the catalyst support comprising a deposit of cobalt thiocyanate on at least a portion of the catalyst support at a temperature of 150°C or lower under inert conditions before heating the catalyst support in step (b). Claim 7 The process according to claim 1 or 2, further comprising passivating the supported cobalt sulfide catalyst with a diluted oxygen stream containing up to 2 volume percent of O at a temperature of 25 °C or lower. ２ and containing up to 2 volume percent of O. Claim 8 The process according to claim 1 or 2, wherein the bulk sulfur to cobalt atom ratio is 0.3 or more. Claim 9 The process according to claim 1 or 2, wherein the catalyst support comprises alumina, carbon, silicon carbide, silica, silica-alumina, hafnia, zirconia, titania, or a mixture thereof, or the cobalt content in the supported cobalt sulfide catalyst is 5 wt% to 50 wt% based on the total weight of the supported cobalt sulfide catalyst.

10. The surface area of the catalyst support is more than 10 m ２ / g to a maximum of 800 m ２ / g, the process according to claim 1 or 2.