Ruthenium metal complex, and catalyst composition, method and system for synthesis of acetic acid through methanol carbonylation

Abstract

The present invention relates to the field of chemical engineering, and relates to a ruthenium metal complex, and a catalyst composition, method and system for synthesis of an acetic acid through methanol carbonylation. The catalyst composition of the present invention comprises: a ruthenium metal complex having a structure of [RuP2X2Y2] and a rhodium catalyst, wherein P is selected from carbonyl (CO), a carbonyl-containing compound, and hydroxyl; X is selected from halogen, hydrogen, and -NRaRb; Y is selected from carbonyl (CO), a carbonyl-containing compound, hydroxyl, halogen, hydrogen, and NRa'Rb'; and Ra, Rb, Ra', and Rb' are each independently selected from H, C1-C10 alkyl, and Li.

Description

Catalyst compositions, methods, and systems for the synthesis of acetic acid from ruthenium metal complexes and methanol carbonylation. Technical Field

[0001] This invention belongs to the field of chemical synthesis, specifically relating to catalyst compositions, methods, and systems for the synthesis of acetic acid from ruthenium metal complexes and methanol carbonylation. Background Technology

[0002] The rhodium catalyst technology for low-pressure methanol carbonylation to acetic acid typically contains 6-10 wt% water in the reaction solution to maintain catalyst activity. Reducing the water content significantly decreases the space-time yield of the catalyst and increases side reactions. Water in the reaction solution is also introduced into the distillation system during acetic acid production, leading to increased steam consumption in the distillation system. Therefore, there is an urgent need in the art to provide a method for the methanol carbonylation synthesis of acetic acid that reduces production costs, steam consumption, and water content in the reaction vessel. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a ruthenium metal complex, a catalyst composition, a method, and a system for the synthesis of acetic acid by methanol carbonylation.

[0004] Specifically, the present invention provides a ruthenium metal complex of Formula I:

[0005] In Formula I, P is selected from carbonyl (CO), carbonyl-containing compounds, and hydroxyl groups; X is selected from halogens, hydrogen, and -NRaRb; Y is selected from carbonyl (CO), carbonyl-containing compounds, hydroxyl groups, halogens, C1-C6 alkyl groups, hydrogen, and NRa'Rb'; Ra, Rb, Ra', and Rb' are each independently selected from H, C1-C10 alkyl groups, and Li.

[0006] In one or more embodiments, the ruthenium metal complex has the structure shown in Formula II:

[0007] In Formula II, P, X, and Y are defined as described in claim 1.

[0008] This invention also provides ruthenium metal complexes selected from the group consisting of:

[0009] The present invention also provides a catalyst composition comprising the ruthenium metal complex and rhodium catalyst described in any embodiment herein.

[0010] In one or more embodiments, the rhodium catalyst is selected from one or more of rhodium acetate, rhodium monoiodocarbonyl, rhodium diiodocarbonyl, rhodium diiodocarbonyl, rhodium triiodocarbonyl, rhodium triiodotricarbonyl, rhodium triiodide, rhodium tetraiodide, and rhodium pentaiodide.

[0011] In one or more embodiments, the mass ratio of rhodium to ruthenium in the catalyst composition is (10-100):1.

[0012] In one or more embodiments, the catalyst composition further includes a lithium-ion promoter.

[0013] The present invention also provides a method for preparing acetic acid by methanol carbonylation, the method comprising: reacting CO with a reaction solution containing a rhodium catalyst, a ruthenium metal complex as described in any embodiment herein, an iodine co-catalyst, a lithium-ion auxiliary agent, methanol, methyl acetate, acetic acid and water in a carbonylation reaction.

[0014] In one or more embodiments, the iodine cocatalyst is an iodine-containing compound, preferably selected from one or more of iodomethane, hydrogen iodide, and lithium iodide.

[0015] In one or more embodiments, the lithium-ion additive is a lithium-ion-containing compound, preferably selected from one or more of lithium iodide, lithium acetate, lithium phosphate, lithium formate, and lithium propionate.

[0016] In one or more embodiments, the ruthenium content in the reaction solution is 50-3000 ppm.

[0017] In one or more embodiments, the water content in the reaction solution is 0.5-4 wt%.

[0018] In one or more embodiments, the lithium ion concentration in the reaction solution is 1000-15000 ppm.

[0019] In one or more embodiments, the rhodium content in the reaction solution is 300-4000 ppm.

[0020] In one or more embodiments, the iodine content in the reaction solution is 2-40 wt%.

[0021] In one or more embodiments, the methanol content in the reaction solution is 0-1 wt%.

[0022] In one or more embodiments, the methyl acetate content in the reaction solution is 0.1-4 wt%.

[0023] In one or more embodiments, the acetic acid content in the reaction solution is 60-90 wt%.

[0024] In one or more embodiments, the method includes:

[0025] The reaction solution is obtained by mixing methanol with the methanol-rich absorbent solution.

[0026] The reaction solution is preheated and then passed into one or more reactors in series with CO to carry out a carbonylation reaction, yielding an initial acetic acid solution.

[0027] The initial acetic acid solution was flash-evaporated to obtain a gas phase containing acetic acid;

[0028] The gas phase containing acetic acid is purified to obtain refined acetic acid.

[0029] In one or more embodiments, the tail gas from the carbonylation reaction is washed with pure methanol to obtain the rich liquid methanol.

[0030] In one or more embodiments, the refining process includes sequentially removing light components, dehydrating, and removing heavy components from a gas phase containing acetic acid.

[0031] In one or more embodiments, the operating pressure of each reactor is 2.5-3.5 MPaG.

[0032] In one or more embodiments, the operating temperature of each reactor is 180-300°C.

[0033] In one or more embodiments, the CO inlet pressure is 3.0-4 MPaG.

[0034] In one or more embodiments, during the flash evaporation step, the partial pressure of carbon monoxide in the gas phase is maintained at ≥0.02 MPaG.

[0035] The present invention also provides a system for preparing acetic acid by methanol carbonylation, the system comprising:

[0036] A reactor or multiple reactors in series are used to perform a carbonylation reaction on a reaction liquid and CO to obtain an initial acetic acid solution;

[0037] A flash evaporator is used to flash evaporate an initial acetic acid solution to obtain a gas phase containing acetic acid.

[0038] The light component removal tower, dehydration tower, and heavy component removal tower are used to sequentially remove light components, dehydrate, and remove heavy components from the acetic acid-containing gas phase to obtain refined acetic acid.

[0039] In one or more embodiments, the system further includes one or more of the following devices:

[0040] The raw material preheater is located at the front end of the reactor and is used to preheat the reaction liquid;

[0041] A high-pressure absorption tower is installed at the top of the reactor to absorb the reactor's exhaust gas.

[0042] An external circulation heat transfer device, coupled to the reactor, is used to transfer heat from the reactor via external circulation.

[0043] The formaldehyde removal device is located at the top of the light component removal tower and is used to absorb aldehydes in the light components removed by the light component removal tower.

[0044] A low-pressure absorption tower is installed at the top of the light-duty gas removal tower to absorb the exhaust gas from the light-duty gas removal tower.

[0045] A catalyst trap, located between the flash evaporator and the light-duty removal tower, is used to trap the catalyst.

[0046] The present invention has the following beneficial effects:

[0047] This invention incorporates a ruthenium metal complex and lithium-ion promoter as a co-catalyst for a rhodium catalyst in the traditional methanol carbonylation synthesis of acetic acid process. This reduces the water content in the reaction solution while maintaining catalyst activity. The water content in the reaction solution can be reduced to 0.5-4% wt%, while the rhodium catalyst concentration can be increased to 1000-4000 ppm. The space-time yield of the catalyst can be increased to over 35 mol / (L·hr), and the catalyst is less prone to precipitation loss. The consumption of rhodium element in the catalyst can be as low as 0.01-0.03 g / t acetic acid. Attached Figure Description

[0048] Figure 1 is a schematic diagram of a system for synthesizing acetic acid by methanol carbonylation in some embodiments of the present invention.

[0049] The reference numerals in the attached drawings are explained as follows: 1-First reactor, 2-Flash evaporator, 3-Light weight removal tower, 4-Dehydration tower, 5-Heavy weight removal tower, 6-High pressure absorption tower, 7-External circulation heat transfer device, 8-Phase separator, 9-Low pressure absorption tower, 10-Second reactor, 11-Flash reboiler, 12-Formaldehyde removal device, 13-Catalyst trap. Detailed Implementation

[0050] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0051] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0052] In this document, the terms “contains,” “includes,” “containing,” and similar terms encompass the meanings of “basically composed of” and “composed of.” For example, when this document discloses “A contains B and C,” “A is basically composed of B and C” and “A is composed of B and C” should be considered as having been disclosed in this document.

[0053] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0054] Unless otherwise specified, percentages refer to mass percentages and proportions refer to mass ratios in this article.

[0055] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the invention to those embodiments or examples. Rather, all alternatives, modifications, and equivalents of the methods and materials described herein are covered within the scope defined by the claims.

[0056] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0057] This invention provides a ruthenium metal complex of Formula I:

[0058] In Formula I, P is selected from carbonyl (CO), carbonyl-containing compounds, and hydroxyl groups; X is selected from halogens, hydrogen, and -NRaRb; Y is selected from carbonyl (CO), carbonyl-containing compounds, hydroxyl groups, halogens, hydrogen, and NRa'Rb'; Ra, Rb, Ra', and Rb' are each independently selected from H, C1-C10 alkyl groups, and Li.

[0059] In some embodiments, the ruthenium metal complex has the structure shown in Formula II:

[0060] In Formula II, P, X, and Y are defined as described in claim 1.

[0061] Preferably, P is selected from CO; preferably, X is selected from halogens and CO, with halogens preferably being I. Preferably, Y is selected from CO, halogens, C1-C6 alkyl groups and NRa'Rb'; Ra' and Rb' are each independently selected from H, C1-C10 alkyl groups and Li.

[0062] In some embodiments, the ruthenium metal complex comprises:

[0063] This invention provides a catalyst composition comprising the ruthenium metal complex of this invention and a rhodium catalyst. Preferably, the rhodium catalyst is selected from one or more of rhodium acetate, rhodium monoiodoxycarbonyl, rhodium diiodoxycarbonyl, rhodium diiodoxycarbonyl, rhodium triiodoxycarbonyl, rhodium triiodoxytricarbonyl, rhodium triiodide, rhodium tetraiodide, and rhodium pentaiodide. Preferably, in the catalyst composition, the mass ratio of rhodium to ruthenium is (10-100):1, for example, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, or 90:1. Preferably, the catalyst composition further comprises a lithium-ion promoter.

[0064] The system for synthesizing acetic acid by methanol carbonylation of the present invention includes one or more reactors (e.g., two reactors in series), a flash evaporator, a light component removal tower, a dehydration tower, and a heavy component removal tower. The system may also include one or more components selected from a feed preheater, a low-pressure absorption tower, a high-pressure absorption tower, an external circulation heat transfer unit, a catalyst trap, and a formaldehyde removal unit. The feed can be methanol and rich-liquid methanol used to absorb tail gas. Before entering the reactor, the feed is preheated in the feed preheater (e.g., from room temperature to 70-180°C) to obtain a reaction solution. The obtained reaction solution and CO are passed into one or more reactors to perform a carbonylation reaction on methanol and / or methanol reaction derivatives to obtain an initial acetic acid solution. The initial acetic acid solution is passed into a flash evaporator for flash evaporation, separating an acetic acid-containing gas phase. The acetic acid-containing gas phase is then passed through a light component removal tower, a dehydration tower, and a heavy component removal tower, where the light component is removed, the water is removed, and the heavy component is removed sequentially to obtain purified acetic acid.

[0065] The present invention provides a method for preparing acetic acid by methanol carbonylation, the method comprising: performing a carbonylation reaction on CO with a reaction solution containing a rhodium catalyst, the ruthenium metal complex of the present invention, an iodine co-catalyst, a lithium ion auxiliary agent, methanol, methyl acetate, acetic acid and water.

[0066] In some implementations, the method includes the steps of:

[0067] The reaction solution is obtained by mixing methanol with the methanol-rich absorbent solution.

[0068] The reaction solution is preheated and then passed into one or more reactors in series with CO to carry out a carbonylation reaction, yielding an initial acetic acid solution.

[0069] The initial acetic acid solution was flash-evaporated to obtain a gas phase containing acetic acid;

[0070] The gas phase containing acetic acid is purified to obtain refined acetic acid.

[0071] The reaction solution contains a rhodium catalyst, a ruthenium metal complex, iodomethane as a co-catalyst, lithium-ion additives, methyl acetate, acetic acid, methanol, and water. In the reaction solution, the ruthenium content is 50-3000 ppm, the water content is 0.5-4 wt%, the lithium-ion concentration is 1000-15000 ppm, the rhodium content is 300-4000 ppm, the iodine content is 2-40 wt%, the methyl acetate content is 0.1-4 wt%, the acetic acid content is 60-90 wt%, and the methanol content is ≤1 wt%. The methanol in the reaction solution can be pure methanol or rich methanol obtained by washing the tail gas from the carbonylation reaction with pure methanol. The methanol carbonylation system of this invention includes a high-pressure tail gas absorption process and a low-pressure tail gas absorption process. Fresh methanol can enter the high-pressure absorption tower and the low-pressure absorption tower respectively to wash the iodomethane and organic matter in the tail gas. The washed rich methanol is then used as raw material in the first reactor.

[0072] Available rhodium catalysts include one or more selected from rhodium acetate, rhodium monoiodoxycarbonyl, rhodium diiodoxycarbonyl, rhodium diiodoxycarbonyl, rhodium triiodoxycarbonyl, rhodium triiodoxytricarbonyl, rhodium triiodide, rhodium tetraiodide, and rhodium pentaiodide.

[0073] Available iodine co-catalysts can be organic or inorganic iodine, such as iodomethane, hydrogen iodide, lithium iodide, etc.

[0074] Available lithium-ion additives include one or more selected from lithium iodide, lithium acetate, lithium phosphate, lithium formate, and lithium propionate.

[0075] Carbon monoxide is introduced into both the first and second reactors. The introduced carbon monoxide can originate from the high-pressure exhaust gas from either the first or second reactor, or from the tail gas from the high-pressure absorption tower. The tail gas from the reactors is cooled before entering the high-pressure absorption tower. The CO inlet pressure is 3.0-4 MPaG.

[0076] One of the beneficial effects of this invention is that it can reduce CO consumption. The amount of CO consumed per ton of acetic acid can be reduced to 395-405 Nm³. 3 .

[0077] In this invention, the reactor is preferably a gas-liquid mixing reactor without mechanical stirring. In this invention, setting up multiple reactors can consume CO and methanol or methyl acetate in the initial acetic acid solution, improving the conversion rate of the raw materials. The operating pressure of each reactor is 2.5-3.5 MPaG, preferably 2.7-3.2 MPaG, the operating temperature is 180-300℃, preferably 190-220℃, and the partial pressure of CO is ≥0.3 MPaG.

[0078] In some embodiments, the system of the present invention includes a first reactor and a second reactor. A portion of the initial acetic acid solution obtained from the reaction in the first reactor (which contains dissolved and / or entrained carbon monoxide and other gaseous products) is passed into the second reactor to continue the carbonylation reaction with CO. The mass ratio of the reaction liquid entering the second reactor to the initial methanol in the first reactor can be (7-10):1. Two types of CO can be introduced into the second reactor: fresh CO and the tail gas from the first reactor.

[0079] In some embodiments, the initial acetic acid solution obtained from the first and second reactors is passed into a flash evaporator. The gaseous substances obtained by flash evaporation include condensable and non-condensable components. The condensable and non-condensable components enter a light phase removal tower. The non-condensable component at the top of the light phase removal tower enters a low-pressure absorption tower. The liquid condensed at the top enters a phase separator; part of the light phase is refluxed, and part is returned to the reaction. The heavy phase—iodomethane—is returned to the reactor to continue participating in the reaction. Crude acetic acid is extracted from the middle of the light phase removal tower and enters a dehydration tower. The non-condensable component (tail gas) is passed into the low-pressure absorption tower for absorption. The carbon monoxide content in the non-condensable component is ≥35% mol. The carbon monoxide content in the low-pressure tail gas is 30-80% mol.

[0080] The exhaust gas contains gases that do not participate in the reaction (e.g., H2, CO2, CH4, N2). If there is extensive recirculation, these gases will accumulate, and a portion can be returned to the reaction, maximizing the utilization of CO in the exhaust gas. The condensable component is crude acetic acid. Flash evaporators can be two or more connected in series. In the flash evaporator, the partial pressure of carbon monoxide in the gas phase is maintained ≥0.02 MPaG, thereby reducing the loss of rhodium catalyst.

[0081] A portion of the liquid phase from flash evaporation returns to the reactor to continue the reaction, while the remainder is sent to the reboiler at the bottom of the flash evaporator for reheating and vaporization. Typically, only one reboiler is installed, with a reboiler temperature of 120-150℃. The reboiler inlet is at the bottom of the flash evaporator, and the outlet is also at the flash evaporator. The gas phase from the reboiler and the flash evaporation together enter the light component removal tower. The volume ratio of the secondary vaporization to the liquid phase from the first flash evaporation in the flash evaporator's reboiler is (1-50):100. The vapor phase vaporized by the reboiler is the second vaporization amount. A catalyst trap can also be installed after the flash evaporator to recover the catalyst from the flash evaporator's gas phase.

[0082] The crude acetic acid obtained from the flash distillation tower is fed into the light phase removal tower, and the top product of the light phase removal tower is further refluxed to the reactor. The light and heavy phase liquids from the phase separator are first fed into the aldehyde removal unit to remove the byproduct aldehydes, and then returned to the reactor.

[0083] In some embodiments, a portion of the initial acetic acid solution is taken from one or more reactors and fed into an external circulation heat transfer device to remove the heat of reaction before being reintroduced into the reactor to continue the reaction. The initial acetic acid solution removed from the first reactor is typically returned to the first reactor. The second reactor typically does not have an external circulation heat transfer device, but it may also have one. The initial acetic acid solution removed from the second reactor is returned to the second reactor. The outlet temperature of the external circulation heat transfer device is 130-190°C, preferably 150-180°C.

[0084] In this paper, the operating pressure of the light-weight removal tower is 0.05-0.15 MPaG, and the operating temperature is 80-160℃. The operating pressure of the dehydration tower is 0.15-0.5 MPaG, and the operating temperature is 130-200℃. The operating pressure of the heavy-weight removal tower is 0.03-0.2 MPaG, and the operating temperature is 90-180℃.

[0085] At low water content, rhodium complexes are more prone to precipitation. These precipitated solids can redissolve upon return to the reactor. Therefore, this invention primarily achieves a high concentration of rhodium catalyst at low water content by adding a certain amount of lithium-ion promoter and ruthenium metal complex to the reaction solution. The addition of lithium-ion promoter and ruthenium metal complex maintains a higher rhodium concentration without precipitation, thereby maintaining the activity of the entire reactor and ensuring high catalyst activity under low water conditions. This method reduces losses caused by catalyst instability and solves the problems of high water content and high steam consumption in the distillation process.

[0086] In this invention, setting up multiple reactors allows the reaction to continue, further converting the intermediate product into acetic acid and improving the single-pass conversion rate.

[0087] Catalysts are prone to precipitation in flash evaporators. This invention maintains a certain CO partial pressure in the flash evaporator while maintaining a certain lithium compound concentration in the liquid phase, which helps to suppress the precipitation of rhodium complexes.

[0088] In addition, reducing the flash evaporation amount of the reaction solution and lowering the water content in the reaction solution helps to reduce the amount of catalyst entrained in the flash vapor phase, which is beneficial to further reduce catalyst consumption.

[0089] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Percentages and parts are by weight unless otherwise stated.

[0090] In the examples and comparative examples described herein, the operating pressure of the light component removal tower is 0.1 MPaG, and the operating temperature is 120°C. The operating pressure of the dehydration tower is 0.3 MPaG, and the operating temperature is 165°C. The operating pressure of the heavy component removal tower is 0.15 MPaA, and the operating temperature is 135°C.

[0091] Preparation Example 1

[0092] Add 10g of ruthenium iodide, 200g of acetic acid aqueous solution (80wt%), 20g of iodomethane (80wt%), and 20g of lithium acetate (80wt%) to a dissolving vessel. Then, replace the ruthenium iodide with CO and maintain the pressure at 0.5MPaG. Heat to 160-180℃, stir at 20-50 rpm, and maintain for 24-48 hours to obtain the following ruthenium metal complex:

[0093] Preparation Example 2

[0094] Add 10g of ruthenium iodide hydrate (10wt% ruthenium content) and 300g of acetic acid aqueous solution (80wt%) to a dissolving vessel, followed by 20g of iodomethane (80wt%) and 20g of lithium acetate (80wt%). Then, replace the ruthenium hydrate with CO and maintain the pressure at 0.5MPaG. Heat to 160-180℃, stir at 20-50 rpm, and maintain for 24-48 hours to obtain the following ruthenium metal complex:

[0095] Example 1

[0096] This embodiment uses the system shown in Figure 1 to synthesize acetic acid via methanol carbonylation:

[0097] The raw material methanol and the rich liquid methanol after tail gas absorption are fed into the first reactor 1 with carbon dioxide for a carbonylation reaction. In the first reactor, CO undergoes a carbonylation reaction with a liquid reaction composition comprising the ruthenium metal complex prepared in Preparation Example 1, a rhodium catalyst (rhodium diiodocarboxylate), a lithium ion promoter lithium iodide, an iodomethane co-catalyst, methyl acetate, acetic acid, methanol, and water. The reaction solution contains 3.5 wt% water, 0.2% methanol, 0.5% methyl acetate, 75% acetic acid, 200 ppm ruthenium, 1300 ppm rhodium, 6500 ppm lithium ions, and 12 wt% iodine (total organic and inorganic iodine). The CO inlet pressure is 3.3 MPaG.

[0098] A portion of the liquid reaction composition (containing dissolved and / or entrained carbon monoxide and other gases) is taken from the first reactor and fed into the second reactor to consume a portion of the dissolved and / or entrained carbon monoxide or newly added carbon monoxide. The mass ratio of the reaction liquid entering the second reactor to the initial methanol in the first reactor can be 9:1. The operating pressure in both the first and second reactors is 3.1 MPaG, the operating temperature is 210℃, and the partial pressure of CO is ≥0.3 MPaG. A portion of the liquid-phase reaction composition taken from the first reactor is fed into a reaction heat transfer device to remove the heat of reaction. The outlet temperature of the external circulation heat transfer device is 160℃. In addition, a portion of the liquid-phase reaction composition is taken from the second reactor and fed into a flash separator, where it is flash-separated into gas and liquid phases. The volume ratio of the secondary vaporization in the flash reboiler to the liquid phase entering the flash separator is 15:100. The gas phase contains condensable and non-condensable components. The condensable components include acetic acid, methyl acetate, iodomethane, and water. The non-condensable components include carbon monoxide, carbon dioxide, methane, hydrogen, and nitrogen. The non-condensable components are ultimately absorbed in a low-pressure absorption tower, with a CO content ≥35%mol. The flash-evaporated liquid phase includes acetic acid, ruthenium metal complex, rhodium catalyst, iodine compounds, lithium compounds, methanol, methyl acetate, and water. A portion of the liquid phase is returned to the first reactor to continue the reaction, while the other portion enters the flash reboiler for reheating and vaporization. The partial pressure of carbon monoxide in the flash vapor phase is maintained at ≥0.02 MPaG, and the temperature inside the flash reboiler is 135℃.

[0099] The flash vapor enters the catalyst collection device 13 for further catalyst recovery. The treated gas then enters the light phase removal tower, where condensable and non-condensable components are separated at the top. The non-condensable component enters the low-pressure absorption tower, while the condensable component enters the phase separator. Part of the light phase is refluxed back to the light phase removal tower, and part is returned to the first reactor. The heavy phase, iodomethane, is returned to the first reactor to continue the reaction. The carbon monoxide content in the low-pressure tail gas is 70% mol. Acetic acid, methyl acetate, iodomethane, and water are separated at the top of the tower and returned to the first reactor after pressurization. A portion of the liquid is also sent to the aldehyde removal device 12 to remove aldehydes, which are byproducts of the side reaction. After removing the aldehydes, the liquid is returned to the first reactor. The crude acetic acid in the light phase removal tower 3 enters the dehydration tower 4, where water is further removed at the top. The aqueous acetic acid at the top of the dehydration tower is returned to the reactor, while the acetic acid in the reactor goes to the heavy phase removal tower 5 for further removal of propionic acid and other heavy components. The product acetic acid is extracted from the top of the tower.

[0100] Example 2

[0101] This embodiment uses the system shown in Figure 1 to synthesize acetic acid via methanol carbonylation:

[0102] The raw material methanol and the rich liquid methanol after tail gas absorption are fed into the first reactor with carbon dioxide for a carbonylation reaction. In the first reactor, CO undergoes a carbonylation reaction with a liquid reaction composition comprising the ruthenium metal complex obtained in Preparation Example 2, the rhodium catalyst diiododicarbonyl rhodium, the lithium ion promoter lithium iodide, the iodomethane co-catalyst, methyl acetate, acetic acid, methanol, and water. The reaction solution contains 2.5 wt% water, 0.5% methanol, 0.5% methyl acetate, 78% acetic acid, 800 ppm ruthenium, 1600 ppm rhodium, 6500 ppm lithium ions, and 10 wt% iodine (total organic and inorganic iodine). The CO inlet pressure is 3.8 MPaG.

[0103] A portion of the liquid reaction composition (containing dissolved and / or entrained carbon monoxide and other gases) is taken from the first reactor and fed into the second reactor to consume some of the dissolved and / or entrained carbon monoxide or newly added carbon monoxide. The mass ratio of the reaction liquid to methanol entering the second reactor can be 8:1. The operating pressure in both the first and second reactors is 2.8 MPaG, the operating temperature is 195℃, and the partial pressure of CO is ≥0.3 MPaG. A portion of the liquid-phase reaction composition taken from the first reactor enters a reaction heat transfer device to remove the heat of reaction. The outlet temperature of the external circulation heat transfer device is 155℃. In addition, a portion of the liquid-phase reaction composition is taken from the second reactor and fed into a flash separator, where it is flash-separated into gas and liquid phases. The volume ratio of the secondary vaporization to the liquid phase from the first flash in the flash reboiler is 10:100. The gas phase contains condensable and non-condensable components. The condensable components include acetic acid, methyl acetate, iodomethane, and water. The non-condensable components include carbon monoxide, carbon dioxide, methane, hydrogen, and nitrogen. The non-condensable components are ultimately absorbed in a low-pressure absorption tower, with a CO content ≥35%mol. The flash liquid phase includes acetic acid, ruthenium metal complex, rhodium catalyst, iodine compounds, lithium compounds, methanol, methyl acetate, and water. A portion of the liquid phase returns to the reaction zone to continue the reaction, while the other portion enters the flash reboiler for reheating and vaporization. The partial pressure of carbon monoxide in the flash vapor phase is maintained at ≥0.02 MPaG, and the temperature in the flash reboiler is 140℃.

[0104] The flash vapor enters the light component removal tower. At the top of the tower, condensable and non-condensable components are separated. The condensable components include acetic acid, methyl acetate, iodomethane, and water. After pressurization and liquefaction, the condensable components are returned to the first reactor for further reaction. The non-condensable components are absorbed in a low-pressure absorption tower. The carbon monoxide content in the low-pressure tail gas is 70% mol. Crude acetic acid from the bottom of the light component removal tower is sent to a dehydration tower for further dehydration. Dilute acetic acid containing water and iodine is returned from the top of the dehydration tower to the first reactor. Acetic acid from the bottom of the dehydration tower is sent to a heavy component removal tower for further removal of propionic acid and other heavy components. Product acetic acid is extracted from the top of the heavy component removal tower.

[0105] Comparative Example 1

[0106] The method of Example 1 was repeated, except that no ruthenium metal complex was added to the reaction solution.

[0107] Comparative Example 2

[0108] The method of Example 2 was repeated, except that no ruthenium metal complex was added to the reaction solution.

[0109] Test case

[0110] The reactor temperature, water content of the reaction solution, catalyst consumption, steam consumption, and space-time yield of acetic acid for Examples 1-2 and Comparative Examples 1-2 are shown in Tables 1-4. Three sets of parallel experiments were performed for each example and comparative example.

[0111] The Karl Fischer method was used to test the water content in the reaction solution.

[0112] The method for testing the consumption of rhodium catalyst is atomic absorption spectrometry.

[0113] The consumption of distillation steam was tested using a pilot plant.

[0114] Table 1: Reaction solution composition, acetic acid yield, and steam consumption in Example 1

[0115] Table 2: Composition of reaction solution, acetic acid yield and steam consumption of Comparative Example 1

[0116] Table 3: Reaction solution composition, acetic acid yield and steam consumption in Example 2

[0117] Table 4: Reaction solution composition, acetic acid yield and steam consumption of Comparative Example 2

Claims

1. The ruthenium metal complex shown in Formula I: In formula I, P is selected from the group consisting of carbonyl (CO), carbonyl-containing compound and hydroxyl; X is selected from the group consisting of halogen, hydrogen and -NRaRb; Y is selected from the group consisting of carbonyl (CO), carbonyl-containing compound, hydroxyl, halogen, C1-C6 alkyl, hydrogen and NRa’Rb’; Ra, Rb, Ra’ and Rb’ are each independently selected from the group consisting of H, C1-C10 alkyl and Li.

2. The ruthenium metal complex of claim 1, wherein, The ruthenium metal complex has the following formula II: In formula II, P, X and Y are defined as in claim 1.

3. A ruthenium metal complex selected from the group consisting of:

4. A catalyst composition characterized in that, The catalyst composition comprises the ruthenium metal complex of any one of claims 1-3 and a rhodium catalyst; preferably, the rhodium catalyst is selected from one or more of rhodium acetate, iodo-carbonyl rhodium, di-iodo-di-carbonyl rhodium, di-iodo-mono-carbonyl rhodium, tri-iodo-mono-carbonyl rhodium, tri-iodo-di-carbonyl rhodium, tri-iodo-tri-carbonyl rhodium, tri-iodide rhodium, tetra-iodide rhodium and penta-iodide rhodium; preferably, the mass ratio of rhodium element to ruthenium element in the catalyst composition is (10-100):1; preferably, the catalyst composition further comprises a lithium ion promoter.

5. A process for the preparation of acetic acid by carbonylation of methanol, characterized in that, The method comprises subjecting CO to a reaction solution comprising a rhodium catalyst, the ruthenium metal complex of any one of claims 1-3, an iodine promoter, a lithium ion promoter, methanol, methyl acetate, acetic acid and water to a carbonylation reaction.

6. The method of claim 5, wherein, The method has one or more of the following features: The iodine promoter is an iodine-containing compound, preferably selected from one or more of methyl iodide, hydrogen iodide and lithium iodide; The lithium ion promoter is a lithium ion-containing compound, preferably selected from one or more of lithium iodide, lithium acetate, lithium phosphate, lithium formate and lithium propionate; The ruthenium element content in the reaction solution is 50-3000 ppm; The water content in the reaction solution is 0.5-4 wt%; The lithium ion concentration in the reaction solution is 1000-15000 ppm; The rhodium element content in the reaction solution is 300-4000 ppm; The iodine content in the reaction solution is 2-40 wt%; The methanol content in the reaction solution is 0-1 wt%; The methyl acetate content in the reaction solution is 0.1-4 wt%; The acetic acid content in the reaction solution is 60-90 wt%.

7. The method of claim 5, wherein, The method comprises: mixing methanol with a methanol-rich solution to obtain a reaction solution; preheating the reaction solution and introducing CO into a reactor or a plurality of reactors connected in series to perform a carbonylation reaction to obtain an initial acetic acid solution; subjecting the initial acetic acid solution to flash evaporation to obtain an acetic acid-containing gas phase; subjecting the acetic acid-containing gas phase to refining to obtain refined acetic acid.

8. The method of claim 7, wherein, The method has one or more of the following features: using pure methanol to wash the tail gas of the carbonylation reaction to obtain the rich-liquid methanol; the refining comprises subjecting the acetic acid-containing gas phase to light component removal, dehydration and heavy component removal in sequence; the operating pressure of each reactor is 2.5-3.5 MPaG; the operating temperature of each reactor is 180-300℃; the introduction pressure of CO is 3.0-4 MPaG; in the flash evaporation step, the carbon monoxide partial pressure of the gas phase is ≥0.02 MPaG.

9. A system for the production of acetic acid by carbonylation of methanol, characterized in that, The system comprises: a reactor or a plurality of reactors connected in series for subjecting a reaction solution and CO to a carbonylation reaction to obtain an initial acetic acid solution; a flash evaporator for flash evaporating the initial acetic acid solution to obtain a gas phase containing acetic acid; a light component removal column, a dehydration column and a heavy component removal column for sequentially removing light components, water and heavy components from the gas phase containing acetic acid to obtain refined acetic acid.

10. The system of claim 9, wherein, The system further comprises one or more of the following devices: a raw material preheater arranged at the front end of the reactor for preheating the reaction liquid; a high-pressure absorption tower arranged at the top of the reactor for absorbing the tail gas of the reactor; an external circulation heat remover coupled with the reactor for external circulation heat removal of the reactor; an aldehyde removal device arranged at the top of the light component removal column for absorbing aldehyde substances in the light components removed by the light component removal column; a low-pressure absorption tower arranged at the top of the light component removal column for absorbing the tail gas of the light component removal column; a catalyst trap arranged between the flash evaporator and the light component removal column for trapping catalysts.

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