MXPA97009588A - Carbonilation process catalyzed with iridio for the production of a carboxil acid - Google Patents

Abstract

A process for the production of a carboxylic acid having n + 1 carbon atoms comprises (a) carbonylating with carbon monoxide, in a first reaction zone, at elevated temperature and pressure, an alkyl alcohol having carbon nomos and / or a reactive derivative thereof, to produce a carboxylic acid having n + 1 of corbonum in a liquid reaction composition comprising product carboxylic acid, an iridium catalyst, an alkyl halide cocatalyst, water, a product carboxylic acid ester and alkyl alcohol, and optionally one or more promoters, (b) extract from the first reaction zone at least a portion of the liquid reaction oxture together with dissolved and / or entrained carbon monoxide, and pass at least one portion of carbon thus extracted to a second zone of reaction, (c) recirculate at least 1% of the carbon monoxide dissolved and / or entrained in the extracted reaction composition by additional carbonylation at elevated temperature and pressure in a second zone of reaction to produce thus carboxylic acid

Description

IRON CARBONILATION PROCESS FOR THE PRODUCTION OF A CARBOXYLIC ACID Field of the Invention The present invention relates to a process for the production of a carboxylic acid by carbonylation in liquid phase of an alkyl alcohol and / or a reactive derivative thereof, in the presence of an iridium catalyst, an alkyl halide co-catalyst and optionally one or more promoters. State of the Art The carbonylation processes in the presence of iridium catalysts are already known and are described, for example, in GB-A-1234121, US-A-3772380, DE-A-1767150, EP-A-0616997, EP -A-0618184, EP-A-0618183, EP-A-0643034, EP-A-0657386 and WO-A-95/31426. In the process with EP-A-0643034 promoters it is said that ionic contaminants such as, for example, (a) corrosion metals, in particular nickel, iron and chromium, and (b) phosphines or nitrogen-containing compounds or ligands. which can be quaternized in situ, should be kept to a minimum in the liquid reaction composition since they will have an adverse effect on the reaction by generating I "in the liquid reaction composition, which has a detrimental effect on the speed of the reaction. In the continuous liquid phase processes, a portion of the liquid reaction composition comprising a carboxylic acid, an iridium catalyst, an alkyl halide co-catalyst, water, an alkyl ester of the carboxylic acid, a promoter optional and residual carbon monoxide in the dissolved and / or entrained state, a product is extracted and recovered therefrom by one or more instantaneous vaporization steps and / or distillation EP-A-0685446 relates to a process for the preparation of acetic acid comprising carbonylar methanol with carbon monoxide in a first reactor in the presence of a rhodium catalyst. The reaction fluid containing dissolved carbon monoxide is passed from the first reactor to a second reactor wherein the dissolved carbon monoxide, without feeding further carbon monoxide, is further reacted before the reaction fluid is introduced into a reactor. instant vaporization zone. However, in this process the presence of iodide salts, for example, inorganic iodides such as lithium iodide or organic iodide salts such as a quaternary ammonium iodide, is essential to maintain catalyst stability at low partial pressures of carbon monoxide. and / or low water concentrations, while iodide salts such as those mentioned above generally have an adverse effect on the reaction rate for an iridium-catalyzed carbonylation process.

Therefore, there remains a need for an improved process for the use of carbon monoxide in the liquid phase carbonylation of an alkyl alcohol and / or a reactive derivative thereof in the presence of an iridium catalyst, a co-catalyst of alkyl halide, water and optionally one or more promoters. SUMMARY OF THE INVENTION In accordance with the present invention there is provided a process for the production of a carboxylic acid having n + 1 carbon atoms, which process comprises (a) carbonylating with carbon monoxide, in a first reaction zone, a elevated temperature and pressure, an alkyl alcohol having n carbon atoms and / or a reactive derivative thereof, to produce a carboxylic acid having n + 1 carbon atoms in a liquid reaction composition comprising carboxylic acid product, a catalyst of iridium, an alkyl halide cocatalyst, water, an ester of the product carboxylic acid and the alkyl alcohol, and optionally one or more promoters, (b) extracting from the first reaction zone at least a portion of the liquid reaction composition together with dissolved and / or entrained carbon monoxide, and passing at least a portion of the liquid reaction and carbon monoxide composition thus extra It gives a second reaction zone(c) reacting at least 1% of the carbon monoxide dissolved and / or entrained in the extracted reaction composition by additional carbonylation at elevated temperature and pressure in a second reaction zone to thereby produce more product carboxylic acid. The advantages that derive from the operation of the process of the present invention include (i) an increase in the amount of carbon monoxide consumed which translates into a lower flow of non-condensable gases in the outlet stream of the second zone. reaction and, therefore, in a lower need to process the exhaust gases and (ii) a higher carbon monoxide consumption as well as a higher acetic acid yield. The process of the present invention solves the technical problem defined above by subjecting the liquid reaction composition extracted from a first reaction zone, together with dissolved and / or entrained carbon monoxide, to other conditions of elevated temperature and pressure to consume monoxide. carbon and produce more carboxylic acid product. Detailed Description of the Invention In step (b) of the process of the present invention, at least a portion of the liquid reaction composition, together with dissolved and / or entrained carbon monoxide, is extracted from the first reaction zone, and at least a portion of the extracted liquid and carbon monoxide dissolved and / or entrained is passed to a second reaction zone. Preferably, virtually all of the liquid reaction composition, together with dissolved and / or entrained carbon monoxide, extracted from the first reaction zone, is passed to the second zone of. reaction. The second reaction zone can be operated at a reaction temperature of 100 to 300 ° C, preferably of 150 to 230 ° C. The second reaction zone can be operated at a higher temperature than the first reaction zone, usually at a temperature of up to 30 ° C higher. The second reaction zone can be operated at a reaction pressure of the order of 10 to 200 bar gauge, preferably 15 to 100 bar gauge. Preferably, the reaction pressure in the second reaction zone is equal to or lower than the reaction pressure in the first reaction zone. The residence time of the liquid reaction composition in the second reaction zone is suitably from 5 to 300 seconds, preferably from 10 to 100 seconds. In the second reaction zone carbon monoxide can be introduced in addition to that introduced into the second reaction zone as dissolved and / or entrained carbon monoxide. Said additional carbon monoxide may be combined with the first liquid reaction composition before introduction into the second reaction zone and / or may be fed separately to one or more points within the second reaction zone. Said additional carbon monoxide may contain impurities such as, for example, H2, N2, C02 and CH4. The additional carbon monoxide may be constituted by the high-pressure outlet gas of the first reaction zone which would advantageously allow the first reaction zone to be operated at a higher CO pressure, the resulting higher flux being fed into < ie lop? y ^ o r¡e carbu-.u to the second reaction zone. In addition, the need to carry out a treaty or to evacuate the gas from it should not be eliminated. The additional carbon may be constituted by another stream containing carbon monoxide such as, for example, a stream rich in carbon monoxide from another plant. The advantage of using a second reaction zone is that carbon monoxide can be used in a stream rich in carbon monoxide in the second reaction zone without disturbing the operation of the first reaction zone. In the second reaction zone, preferably more than 10%, more particularly more than 25%, even more especially more than 50%, for example at least 95%, of the carbon monoxide dissolved and / or entrained in the reaction composition are consumed. extracted from the first reaction zone. Preferably, and in order to avoid a significant increase in the volatility of the iridium catalyst and / or optional promoter, the amount of carbon monoxide in the second liquid composition extracted from the second reaction zone should not be reduced to too low values, generally for keep at least 20% by volume of the dissolved and / or entrained gases, which may be constituted by carbon monoxide entrained and / or dissolved without reacting and / or by car-H-carbon monoxide. . This also helps reduce the formation of by-products, for example, methane. According to one embodiment of the present invention, the first and second reaction zones are maintained in separate reaction vessels with means for extracting from the first reaction vessel and passing the liquid reaction composition of the first reaction vessel to the second reaction vessel. with carbon monoxide dissolved and / or entrained. Said second separate reaction vessel may comprise a section of pipe between the first reaction vessel and an instantaneous vaporization valve of the liquid reaction composition. Preferably, the pipe is filled with liquid. Normally, the ratio of the length to the diameter of the pipe can be approximately 12: 1, although length / diameter ratios higher and lower than said value can be used. Alternatively, in such embodiment, the first reaction vessel can be operated as a liquid-filled retro-mix reactor in fluid communication with the second reaction vessel which can be operated as a bubble column reactor with a retro-mix limited. The design of the second reaction zone is suitably such that the back-mixing in the second reaction zone is minimized or substantially eliminated., whose design would not be fully achieved by a stirred tank reactor. In another embodiment of the present invention, the second reaction zone may comprise a relatively quiet reaction zone within a reactor in whose main body the first reaction zone is maintained. Said arrangement may comprise, for example, a reactor distributed in a first reaction zone forming a major proportion of the reactor space and having agitation means therein and a second smaller reaction zone that does not have agitation means , the second reaction zone being in liquid communication with the first reaction zone. The first reaction zone may comprise a conventional liquid phase carbonylation reaction zone. The pressure of the carbonylation reaction in the first reaction zone is suitably 15 to 200 bar gauge, preferably 15 to 100 bar gauge, more preferably 15 to 50 bar gauge and especially 18 to 35 bar gauge. The temperature of the carbonylation reaction in the first reaction zone is suitably 100 to 300 ° C, preferably 150 to 220 ° C. In the process of the present invention, the product carboxylic acid comprises a C2 to C ?? carboxylic acid / preferably a C¿ to C6 carboxylic acid and more particularly a C2 to C3 carboxylic acid and especially is acetic acid. Preferably, the alkyl alcohol carbonylation reactant is a primary or secondary alkyl alcohol, more preferably a primary alcohol. Suitably, the alkyl alcohol has from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, more preferably 1 to 2 carbon atoms and especially methanol. Suitable reactive derivatives of the alkyl alcohol include the ester of the alcohol and the carboxylic acid product, for example methyl acetate; the corresponding dialkyl ether, for example dimethyl ether; and the corresponding alkyl halide, for example methyl iodide. In the case of ether or ester reactants, the use of water as a co-reactant is required. A mixture of alkyl alcohol and reactive derivatives thereof can be used as reactants in the process of the present invention, for example a mixture of methanol and methyl acetate. Preferably, methanol and / or methyl acetate are used as reactants. At least part of the alkyl alcohol and / or reactive derivative thereof will become, and therefore be present as, the corresponding ester with the product carboxylic acid in the liquid carbonylation reaction composition by reaction with the product carboxylic acid or solvent. Preferably, the alkyl ester concentrations in the liquid reaction compositions in the first and second reaction zones are independently from 1 to 70% by weight, more preferably from 2 to 50% by weight, more particularly from 3 to 35% by weight . Water can be formed in situ in the liquid reaction compositions, for example, by the esterification reaction between the alkyl alcohol reactant and the carboxylic acid product. Water can be independently introduced to the first and second carbonylation reaction zones together with or separately from other components of the liquid reaction composition. The water can be separated from the other components of the reaction compositions extracted from the reaction zones and can be recycled in controlled amounts to maintain the required concentration of water in the liquid reaction compositions. Preferably, the water concentrations in the liquid reaction compositions in the first and second reaction zones are independently of the order of 0.1 to 20% by weight, more preferably 1 to 15% by weight and especially 1 to 10. % in weigh. Preferably, the alkyl halide in the carbonylation reaction has an alkyl moiety corresponding to the alkyl moiety of the alkyl alcohol reactant. More preferably, the alkyl halide is methyl halide. Preferably, the alkyl halide is an iodide or bromide, more particularly an iodide. Preferably, the alkyl halide concentrations in the liquid carbonylation reaction compositions in the first and second reaction zones are independently from 1 to 20% by weight, preferably from 2 to 16% by weight. The iridium catalyst in the liquid carbonylation reaction compositions in the first and second reaction zones can comprise any iridium-containing compound that is soluble in the liquid reaction compositions. The iridium catalyst can be added to the liquid reaction compositions in any suitable form which is dissolved in the liquid reaction compositions or which can be converted to a soluble form. Preferably, the iridium can be used as a chloride-free compound, such as acetates, which are soluble in one or more of the components of the liquid reaction compositions, for example water and / or acetic acid, and can thus be added to the reaction as solutions in it. Examples of suitable iridium-containing compounds that can be added to the liquid reaction compositions include the following: IrCl3, lRl3, IrBr3, [Ir (CO) 2I] 2, [Ir (CO) 2Cl] 2, [Ir (CO) 2Br ] 2, [Ir (CO) 2I2] "Hp [Ir (CO) 2Br2]" Hp [Ir (CO) 4I2] "Hp [Ir (CH3) I3 (CO) 2]" Hp Ir4 (CO) 12, IrCl3 .4H20, IrBr3.4H20, Ir3 (CO) 12, iridium metal, lr203, Ir02, Ir (acac) (C0) 2, lr (acac) 3, iridium acetate [Ir30 (0Ac) 6 (H20) 3] [ OAc], and hexachloroiridic acid [H2IrCl6], preferably chloride-free iridium complexes, such as acetates, oxalates and acetoacetates. Preferably, the iridium catalyst concentrations in the liquid reaction compositions in the first and second reaction zones are independently of the order of 100 to 6000 ppm by weight iridium. Preferably, the liquid reaction compositions of the first and second reaction zones further comprise, as a promoter, one or more of osmium, rhenium, ruthenium, cadmium, mercury, zinc, gallium, indium and tungsten and more preferably a promoter chosen from ruthenium and osmium, the promoter being especially ruthenium. The promoter can comprise any compound containing promoter metal that is soluble in the liquid reaction compositions. The promoter can be added to the liquid reaction compositions in any suitable form which is dissolved in the liquid reaction compositions or which can be converted to a soluble form. Preferably, the promoter compound can be used as chloride-free compounds, such as acetates, which are soluble in one or more of the components of the liquid reaction compositions, for example, water and / or acetic acid, and thus they can be added to the reaction as solutions therein. Examples of suitable ruthenium-containing compounds that can be used include ruthenium chloride (III), ruthenium chloride (III) trihydrate, ruthenium chloride (IV), ruthenium bromide (III), ruthenium iodide (III), ruthenium metal, ruthenium oxides, ruthenium (III) format, [Ru (C0) 3I3] "Hp tetra (aceto) chloro-ruthenium (II , III), ruthenium (III) acetate, ruthenium propionate (III), ruthenium butyrate (III), ruthenium-pentacarbonyl, triruthenium-dodecacarbonyl and ruthenium-halocarbonyl compounds such as dichlorotricarbonyl ruthenium (II) dimer, dibromotricarbo-nilrutenium (II ) dimer and other organo-ruthenium complexes such as tetrachlorobis (4-cymene) diruthenium (II), tetraclo-robis (benzene) dirruthenium (II), dichloro (cycloocta-1,5-diene) ruthenium (II) polymer and tris (acetylacetonate) ruthenium (III).

Examples of suitable osmium-containing compounds which may be used include osmium (III) hydrated and anhydrous chlorides, osmium metal, osmium tetraoxide, triosmium-dodecarbonyl, pentachloro-μ-nitroso-diosmium and mixed osmium-halocarbonyl such as tricarbonyl dichloride dimer. ro-osmium (II) and other complexes, organ-osmium. Examples of suitable rhenium-containing compounds that can be used include the following compounds: Re2 (CO) 10, Re (C0) 5Cl, Re (C0) 5 Br, Re (C0) 5l, ReCl3.xH20, ReCl5.yH. 20 and [. { Re (C0) 4l} 2] . Examples of suitable cadmium-containing compounds that can be used as promoter sources include Cd (0Ac) 2, Cdl2, CdBr2, CdCl2, Cd (0H) 2 and cadmium acetylacetonate. Examples of suitable mercury-containing compounds that can be used as promoter sources include Hg (0Ac) 2, Hgl2, HgBr2, HgCl2, Hg2I2, and Hg2Cl2. Examples of suitable zinc-containing compounds that can be used as promoter sources include Zn (0Ac) 2, Zn (0H) 2, Znl 2, ZnBr 2, ZnCl 2 and zinc acetylacetonate. Examples of suitable gallium-containing compounds that can be used as promoter sources include gallium acetylacetonate, gallium acetate, GaCl 3, GaBr 3, Gal 3, Ga 2 Cl 4 and Ga (0H) 3. Examples of suitable indium-containing compounds that can be used as promoter sources include indium acetylacetonate, indium acetate, InCl3, InBr3, Inl3, Inl and In (OH) 3. Examples of suitable tungsten containing compounds that can be used as promoter sources include the following: W (C0) e, WC14, C16, WBr5, WI2 or C9H12W (CO) 3 and any tungsten chloro-, bromo- or iodine compound -carbonyl. Preferably, the promoter-containing compounds are free of impurities that provide or generate in situ ionic iodides, which can cause inhibition of the reaction, for example, alkali metal salts or alkaline earth metal salts or salts of other metals. Preferably, the promoter is present in an effective amount up to the limit of its solubility in the liquid reaction compositions and / or in any of the recycled liquid process streams to the carbonylation reaction zones from the acid recovery stage. acetic. The promoter is suitably present in the liquid reaction compositions in a molar ratio of each promoter (when present): iridium in the range of [0.1 to 100]: 1, preferably [more than 0.5] .1, more preferably [more than 1]: 1, in particular [up to 20]: 1 and still more especially [up to 15]: 1 and even more preferably [up to 10]: 1. It has been found that the beneficial effect of a promoter, such as ruthenium, is greater than the concentration of water that provides the maximum carbonylation rate at any defined concentration of methyl acetate and methyl iodide. A suitable promoter concentration is from 400 to 5,000 ppm. The carboxylic acid can be used as a solvent for the carbonylation reaction. Although in general it is preferable to operate the process in the substantial absence of added iodide salt, i.e., a salt that generates or dissociates an iodide ion, it may be possible, under certain conditions, to tolerate said salt. Therefore, ionic contaminants such as, for example, (a) corrosion metals, in particular nickel, iron and chromium and (b) phosphines or nitrogen-containing compounds or ligands, which can be quaternized in situ, should be kept to a minimum or eliminated in the liquid reaction composition, since they may generally have an adverse effect on the reaction by generating I "in the liquid reaction composition which has an adverse effect on the reaction rate It has been found that some metallic corrosion contaminants such as, for example, molybdenum, are less susceptible to IP generation. corrosion which have an adverse effect on the reaction rate can be minimized by using suitable corrosion-resistant construction materials Similarly, contaminants such as alkali metal iodides, for example lithium iodide, should be kept to a minimum. Corrosion metal and other ionic impurities can be reduced by the use of an indoor resin bed. suitable ion exchange, to treat the reaction composition, or preferably a recycle stream of catalyst. Said process is described in US 4007130. Preferably, the ionic contaminants are maintained below a concentration at which they would generate less than 500 ppm I, preferably less than 250 ppm IP in the liquid reaction composition. The reactant carbon for the carbonylation reaction may be essentially pure or may contain inert impurities such as carbon dioxide, methane, nitrogen, noble gases, water and paraffinic hydrocarbons C to C 4. The presence of hydrogen in carbon monoxide and generated in The pressure of the water gas displacement reaction is preferably kept low, for example, at a partial pressure of less than 1 bar, since its presence can result in the formation of hydrogenation products. The reaction is suitably from 1 to 70 bar, preferably from 1 to 35 bar and more particularly from 1 to 15 bar. or it can be recovered from the second reaction zone and optionally together or separately from the first reaction zone by instantaneous separation. In the instantaneous separation, the liquid reaction composition is passed to an instantaneous vaporization zone via an instantaneous vaporization valve. The instantaneous separation zone may be an adiabatic flash vaporization vessel or may have additional heating means. In the flash separation zone, a liquid fraction comprising the majority of the iridium catalyst and most of the optional promoters is separated from a vapor fraction comprising carboxylic acid, carbonylatable reactant, water and halide carbonylation co-catalyst. of alkyl, the liquid fraction being recycled to the first reaction zone and the vapor fraction being passed to one or more distillation zones. In the distillation zones, the product carboxylic acid is separated from other components that are recycled to the first and / or second reaction zone. The carboxylic acid produced by the process according to the present invention can be further purified by conventional methods, for example, by further distillation to remove impurities such as water, unreacted carbonylation reactant and / or ester derivative thereof and carboxylic acids byproducts of higher Boiling point. DESCRIPTION OF THE DRAWINGS The invention will now be illustrated by means of the following Examples and with reference to the attached Figures. Figures 1 and 2 are schematic diagrams of the apparatus used in the Examples. Figures 3 to 5 are representations of different arrangements of the secondary reaction zones. With reference to Figure 3, A is a first reaction zone comprising a primary reactor incorporating a stirrer and / or jet mixer and / or other agitation means and B is a second reaction zone comprising a secondary tubular reactor (or pipe) in communication with an instantaneous vaporization valve. With reference to Figure 4, A 'is a first reaction zone comprising a primary reactor operated filled with liquid and incorporating a stirrer and / or jet mixer and / or other agitation means. B 'is a second reaction zone comprising a secondary tubular reactor (or pipe) disposed above the primary reactor. The secondary reactor can be operated partially filled with liquid with the liquid-filled portion in communication with an instantaneous vaporization valve and with the gaseous space in communication with a high pressure outlet gas valve (not shown). Alternatively, the secondary reactor can be operated filled with liquid, thereby eliminating the need to have a high pressure outlet gas system. With reference to Figure 5, A "is a first reaction zone comprising a primary reactor incorporating a stirrer and / or jet mixer and / or other agitation means B" is a second reaction zone comprising a portion divided from the first reaction zone and in liquid communication with it. Divided portion B "communicates with an instantaneous vaporization valve EXAMPLES Example 1 APPARATUS AND METHOD The apparatus used is shown in Figures 1 and 2. With reference to Figure 1, the apparatus comprises a stirred primary carbonation reactor (1) , a secondary carbonization reactor (2), an instantaneous vaporization tank (3) and a purification system (not illustrated), all built with zirconium 702. In practice, commercial quality methanol, which has been used to wash the exit gas, it is carbonylated in the 6 liter reactor (1) in the presence of the iridium carbonylation catalyst and a promoter, at a pressure of 24-32 bar gauge and at a temperature of 181-195 ° C).

The reactor (1) is equipped with an agitator / propeller (4) and with a deflection cage (not shown) to ensure intimate mixing of the liquid and gaseous reactants. The carbon monoxide is supplied from a commercial plant or from pressurized bottles to the reactor via a sprayer (5) disposed below the agitator (4). To minimize the entry of iron into the reactor, the carbon monoxide is passed through a carbon filter (not shown). A jacket (not shown), through which hot oil circulates, allows the reaction liquid to be maintained in the reactor at a constant reaction temperature. The liquid reaction composition is analyzed by near infrared analysis or by gas phase chromatography. For inert purging, the high-pressure exhaust gas is separated from the reactor via line (6). It is then passed through a condenser (not shown) before the pressure drops to 1.48 bar gauge through the valve (7) to be then fed to the washing system. The liquid reaction composition is extracted from the carbonylation reactor (1) to the reassuring well (8) and is directed via the line (9) into the instantaneous vaporization tank (3) under the control of the reactor level. In the flash tank, the liquid reaction composition is vaporized to a pressure of 1.48 bar gauge. The resulting mixture of vapor and liquid is separated; the catalyst rich liquid is returned to the reactor via line (10) and pump (11) and the vapor is passed through a separator of solid or liquid particles (12) of the gases and then sent directly as steam to the system of recovery of acetic acid (13). The secondary reactor (2) is connected to the instantaneous vaporization line (9) and coupled with isolation valves so that the flow leaving the reactor either passes directly to the flash valve or directly through the secondary reactor (2) towards the flash valve. The second reactor (2) comprises a pipe of 2.5 cm in diameter and 30 cm in length and, together with the associated pipes, has a volume of about 11% of the first reactor. The pipe is located in parallel with the instantaneous vaporization line (9) and is provided with an additional carbon monoxide supply via line 14. The secondary reactor is operated at the same pressure as the primary reactor. The acetic acid is recovered from the vapor entering the acetic acid recovery system (13). With reference to Figure 2, the apparatus incorporates features 1 to 14 of Figure 1 and further incorporates line 15 and control valve 16 (the by-pass line of the secondary reactor has not been shown to provide clarity) . The modification is necessary so that the high pressure (HP) outlet gas can be fed directly to the second reaction zone. Alternatively, a compressor may be used to feed the HP exhaust gas to the second reaction zone. This is mainly so that the second reaction zone can operate at a lower pressure than that of the first reaction zone. To achieve greater clarity, the CRS line to the reactor, which includes the pump (11), has not been illustrated. Example 1 Using the apparatus and method described with reference to Figure 1, methanol was carbonized in the primary carbonylation reactor (1) at 192.8 ° C and a total pressure of 30.9 bar gauge. A liquid reaction composition was extracted from the reactor through line (9). The liquid reaction composition of the primary reactor (1) comprised about 7% by weight of methyl iodide, 15% by weight of methyl acetate, 5% by weight of water, 73% by weight of acetic acid, 1180 ppm of iridium and 1,640 ppm ruthenium. Next, the liquid reaction composition extracted from the reactor was diverted to the second reactor (2). The liquid reaction composition was further carbonylated in the second reactor at a temperature in the intermediate part of 190 ° C and a total pressure of 30 ° C., 9 bar gauge with a residence time of 40-50 seconds. The liquid reaction composition of the second reactor (2) was passed to the flash vessel (3) operated at a pressure of 1.48 bar gauge. The results are shown in Table 1. The results show that 63 g / hour of carbon monoxide was converted into the second reaction zone, which is a significant proportion (approximately 93%) of the 68 g / hour of monoxide carbon that, according to estimation by means of a reference experiment, dissolved and / or entrained in the first liquid reaction composition. Example 2 The process of Example 1 was repeated except that the temperature in the intermediate part of the second reactor was maintained at 185 ° C. The results are shown in Table 1.

This Example demonstrates that the CO dissolved and / or entrained in the liquid composition is consumed at 185 ° C. Example 3 The process of Example 1 was repeated except that no external heat was supplied to the second reactor. The results are shown in Table 1. This Example demonstrates that, in the absence of external heat, dissolved and / or entrained CO is consumed in the liquid composition. Example 4 The process of Example 1 was repeated except that more carbon monoxide (containing <2% v / v of impurities) was fed to the second reactor at 35 g / h. The results are shown in Table 1. This Example demonstrates that at 190 ° C the dissolved and / or entrained CO is consumed in the liquid composition and in the additional CO feed. Example 5 The process of Example 1 was repeated except that more carbon monoxide (containing <2% v / v of impurities) was fed to the second reactor at 65 g / h. The results are shown in Table l. This Example demonstrates that at 190 ° C the dissolved and / or entrained CO is consumed in the liquid composition and in the additional CO feed. Example 6 The process of Example 1 was repeated except that more carbon monoxide (containing <2% v / v of impurities) was fed to the second reactor at 100 g / h. The results are shown in Table 1. This Example demonstrates that at 190 ° C the dissolved and / or entrained CO is consumed in the liquid composition and in the additional CO feed.

TABLE 1 * not registered.

Examples 7 to 11 The primary reactor (1) was operated at a total pressure of 27.6 bar gauge. The second reaction zone (2) was operated at a pressure of 27 bar gauge using the control valve (16). This pressure difference constituted the driving force that allowed the supply of the HP exhaust gas along line (15) to the interior of the second reaction zone. The temperature in the second reaction zone was controlled in a manner similar to that indicated for Examples 4-6. The liquid reaction composition of the primary reactor (1) was similar to that of Examples 1 to 6, ie 5% by weight of water, 7% by weight of methyl iodide and 15% by weight of methyl acetate. The concentrations of iridium and ruthenium were as illustrated in Table 2. Example 7 was a repeat of Example 1, but in this case the amount of carbon monoxide dissolved and / or entrained in the extracted liquid reaction composition was estimated. of the primary reactor (1) was 114 g / hour. In Example 7, there was a conversion of carbon monoxide of 91% in the second reaction zone. In Examples 8 to 10, variable amounts of HP exhaust gas were directed to the second reaction zone (2) through line (15). The concentration of carbon monoxide in this stream was about 75% v / v for each Example. Example 11 was designed to determine the effects of the impure carbon monoxide feed to the second reaction zone (2). This stream contained 70% v / v carbon monoxide, 25% v / v nitrogen and 5% v / v hydrogen. The results of Examples 7 to 11 are given in Table 2. TABLE 2

Claims (26)

1. NOVELTY OF THE INVENTION Having described the present invention is declared as a novelty and, therefore, the content of the following is claimed as property: CLAIMS 1. - A process for the production of a carboxylic acid having n + 1 carbon atoms , characterized in that it comprises (a) carbonylating with carbon monoxide, in a first reaction zone, at elevated temperature and pressure, an alkyl alcohol having n carbon atoms and / or a reactive derivative thereof, to produce a carboxylic acid which has n + 1 carbon atoms in a liquid reaction composition comprising product carboxylic acid, an iridium catalyst, an alkyl halide co-catalyst, water, an ester of the product carboxylic acid and the alkyl alcohol, and optionally one or more promoters, (b) extract from the first reaction zone at least a portion of the liquid reaction composition together with dissolved and / or entrained carbon monoxide , and passing at least a portion of the liquid reaction composition and carbon monoxide thus extracted to a second reaction zone, and (c) reacting at least 1% of the carbon monoxide dissolved and / or entrained in the reaction composition. extracted by additional carbonylation at elevated temperature and pressure in a second reaction zone to thereby produce more product carboxylic acid.
2. 2. A process according to claim 1, characterized in that virtually all of the liquid reaction composition, together with dissolved and / or entrained carbon monoxide, extracted from the first reaction zone is passed to the second reaction zone.
3. 3. A process according to claim 1 or 2, characterized in that methanol and / or methyl acetate are carbonized with carbon monoxide in the first reaction zone.
4. 4. - A process according to any of the preceding claims, characterized in that the concentrations of the product carboxylic acid ester and the alkyl alcohol, in the first and second reaction zones, are independently of the order of 3 to 35% by weight.
5. 5. - A process according to any of the preceding claims, characterized in that the water concentrations in the liquid reaction compositions, in the first and second reaction zones, are independently of the order of 1 to 10% by weight.
6. 6. - A process according to any of the preceding claims, characterized in that the concentrations of alkyl halide in the liquid reaction compositions, in the first and second reaction zones, are independently of the order of 2 to 16% by weight.
7. 7. - A process according to any of the preceding claims, characterized in that the iridium catalyst concentrations in the liquid reaction compositions of the first and second reactors are from 100 to 6,000 ppm by weight iridium.
8. 8. - A process according to any of the preceding claims, characterized in that the liquid reaction compositions further comprises, as a promoter, one or more of ruthenium and osmium.
9. 9. A process according to claim 8, characterized in that the promoter is present in the liquid reaction compositions in a molar ratio of each promoter to iridium of [up to 10]: 1.
10. 10. - A process according to any of the preceding claims, characterized in that it is carried out in the substantial absence of added iodide salt.
11. 11. - A process according to any of the preceding claims, characterized in that, in the first reaction zone, the temperature of the carbonylation reaction is 150 to 220 ° C and the pressure is 15 to 50 bar gauge.
12. 12. - A process according to any of the preceding claims, characterized in that, in the second reaction zone, the reaction temperature is 150 to 30 ° C and the pressure is 15 to 100 bar gauge.
13. 13. - A process according to any of the preceding claims, characterized in that the residence time of the liquid reaction composition in the second reaction zone is from 5 to 300 seconds.
14. 14. - A process according to any of the preceding claims, characterized in that in the second reaction zone carbon monoxide is introduced in addition to that introduced into the zone as dissolved and / or entrained carbon monoxide.
15. 15. A process according to claim 14, characterized in that the additional carbon monoxide is high-pressure exit gas of the first reaction zone.
16. 16. - A process according to any of the preceding claims, characterized in that in the second reaction zone consumes more than 25% of the carbon monoxide dissolved and / or entrained in the reaction composition extracted from the first reaction zone.
17. 17. - A process according to any of the preceding claims, characterized in that at least 95% of the carbon monoxide dissolved and / or entrained in the reaction composition extracted from the first reaction zone is consumed in the second reaction zone.
18. 18. - A process according to any of the preceding claims, characterized in that the amount of carbon monoxide in the second liquid composition - extracted from the second reaction zone is reduced to maintain at least 20% by volume of the dissolved and / or entrained gases and consists of entrained and / or unreacted dissolved carbon monoxide and / or additional carbon monoxide.
19. 19. A process according to any of the preceding claims, characterized in that the first and second reaction zones are maintained in separate reaction vessels with means for extracting from the first reaction vessel and passing the liquid reaction composition of the reaction vessel to the second reaction vessel. first reaction vessel with dissolved and / or entrained carbon monoxide.
20. 20. A process according to claim 19, characterized in that the second reaction vessel comprises a pipe section between the first reaction vessel and an instantaneous vaporization valve of the liquid reaction composition.
21. 21. A process according to claim 19, characterized in that the first reaction vessel is operated as a back-mixing reactor filled with liquid and in fluid communication with the second reaction vessel.
22. 22. - A process according to claim 21, characterized in that the second reactor is operated as a bubble column reactor with limited retro-mixing.
23. 23. A process according to any of claims 1 to 18, characterized in that the second reaction zone comprises a relatively quiet reaction zone within a reactor in whose main body the first reaction zone is housed.
24. 24. A process according to claim 23, characterized in that the reactor is divided into a first reaction zone that constitutes a main proportion of the reaction space and that has means of agitation therein and a second reaction zone smaller than not it has agitation means, the second reaction zone being in liquid communication with the first reaction zone.
25. 25. A process according to any of the preceding claims, characterized in that the partial pressure of the carbon monoxide in the first and second reaction zones is independently of the order of 1 to 15 bar.
26. 26. - A process according to any of the preceding claims, characterized in that the product carboxylic acid is acetic acid.