A multi-stage series reaction process and system for catalytic oxidative dehydrogenation of ethane to ethylene and acetic acid without diluent

Abstract

The present application relates to the preparation technology of ethylene and acetic acid in organic chemical industry, and particularly to a multi-stage series non-dilution process method and system for preparing ethylene and acetic acid by catalytic oxidation dehydrogenation of ethane. Compared with the existing disclosed technology, the method and system provided by the present application do not use nitrogen or water as a diluent in the raw material; the oxygen in any one reactor is close to complete conversion, that is, the oxygen content in the tail gas of each reactor is very low, and the process safety is high. The reactors can be multi-stage series, that is, the ethane single-pass conversion level of the device can be flexibly adjusted according to the needs, and the ratio of ethylene and acetic acid two products can be adjusted to better adapt to market changes. The method and system provided by the present application have high ethylene molar selectivity and low raw material consumption. The method and system provided by the present application have low energy consumption and less waste (mainly carbon monoxide and carbon dioxide).

Description

Technical Field

[0001] This invention relates to the technology for preparing ethylene and acetic acid in organic chemical industry, and in particular to a multi-stage series reaction process and system for producing ethylene and acetic acid by catalytic oxidative dehydrogenation of ethane without diluent in the raw materials. Background Technology

[0002] Ethylene is one of the world's largest consumer goods and chemicals, and the world's highest-produced organic chemical raw material. Known as the "mother of the petrochemical industry," it is a fundamental raw material for petrochemicals and a key indicator of a country's petrochemical industry level. In 2022, global ethylene production capacity reached 210 million tons, with an output of 197 million tons. Since Union Carbide Corporation in the United States developed and completed the first ethylene cracking plant in 1923, global ethylene production has relied primarily on steam cracking technology for nearly a century. Today, over 90% of global ethylene production is achieved through steam cracking. The development of steam cracking technology can be broadly divided into two stages based on the reactants: The first stage, from the birth of steam cracking technology to the beginning of this century, saw naphtha, with its price advantage and ease of storage and transportation, remain the primary feedstock for steam cracking. The second stage, since the US shale gas revolution began in 2010, has seen a significant increase in the supply and declining prices of low-carbon alkanes such as ethane, making steam cracking of ethane the most competitive ethylene production process. Furthermore, ethylene, as the highest-yielding organic chemical raw material, also has the highest global energy consumption for production (up to 2.0 × 10⁻⁶). 15 Ethane is an organic chemical product with the highest associated greenhouse gas emissions (kJ / year), so technological innovation in its production will have a profound impact on the global energy and environmental landscape. Although the ethane cracking process for ethylene has the lowest overall production cost, it is still a highly energy-intensive, highly polluting, and strongly endothermic process, typically requiring operating temperatures above 800℃ (Equation 1). Therefore, developing a more advanced new ethylene production process is of paramount strategic importance. Ethane catalytic oxidative dehydrogenation (ODHE) for ethylene production is a spontaneous energy-saving process that is not limited by thermodynamic equilibrium and can theoretically be carried out at room temperature (Equation 2). Given ethylene's crucial role in the national economy and the increasingly urgent global demand for environmental protection, developing a low-energy-consumption, low-carbon-emission directional ethane-to-ethylene conversion technology is essential.

[0003] Acetic acid (acetic acid) is not only used in food processing but is also an important intermediate in chemical production. It is primarily used to produce purified terephthalic acid (PTA), vinyl acetate, acetate esters, acetic anhydride, and chloroacetic acid, among other compounds. Acetic acid is used as an industrial solvent and raw material in pesticides, pharmaceuticals, and dyes, and has wide applications in textile printing and dyeing, photographic pharmaceuticals, and the rubber industry. Currently, the largest downstream demand for acetic acid is PTA, accounting for approximately 30% of total consumption, and it is a crucial raw material for the polyester industry. In 2020, China accounted for 53.4% ​​and 45.8% of global acetic acid production and consumption, respectively, making it the world's largest producer and consumer of acetic acid.

[0004] With the development and rapid expansion of the acetic acid industry, acetic acid production processes have undergone continuous iteration and updates. Based on different raw materials, acetic acid production routes can be divided into acetylene, ethanol, ethylene, butane or light oil routes, and methanol routes. The acetylene, ethanol, and ethylene raw material routes specifically involve oxidizing acetylene, ethanol, and ethylene to obtain acetaldehyde, which is then further oxidized to produce acetic acid. The methanol route, due to its mature technology and cost advantages, has become the main acetic acid production process, accounting for over 90% of total acetic acid production capacity. However, this process is cumbersome, has high investment costs, and the catalysts used contain toxic oxalates. Therefore, new process technologies are needed. In 1978, Thorsteinson et al. reported the direct oxidation of ethane to acetic acid under pressure using a Mo-V catalyst, thus initiating research on the selective oxidation of ethane to produce acetic acid. Publicly available information indicates that the selective oxidation of ethane to acetic acid utilizes ethane and oxygen (or air) in the air to directly produce acetic acid under pressure at 200–300°C. Water vapor is typically added to the reaction system to improve acetic acid selectivity. While the addition of water is beneficial for improving acetic acid selectivity, it inevitably increases separation energy consumption. One advantage of this invention is that no diluent, including water, is added to the feed gas. Using ethane as a raw material, acetic acid is produced simultaneously with the main ethylene product (Equation 3).

[0005] The process of direct dehydrogenation of ethane to ethylene:

[0006] C2H6=C2H4+H2,△ r H m =136kJ / mol………………………………………………Equation 1

[0007] Ethane oxidative dehydrogenation to ethylene process:

[0008] C2H6 + 0.5O2 = C2H4 + H2O, Δ r H m = -104 kJ / mol ………………………………………Equation 2

[0009] C2H6 + 1.5O2 = C2H4O2 + H2O, Δ r H m = -591kJ / mol…………………………………………Equation 3

[0010] ODHE has been extensively studied in recent decades. The introduction of oxygen thermodynamically supports the generation of deep oxidation products such as CO and CO2, but it also poses significant challenges to the safety of the process. Therefore, it is necessary not only to develop highly selective ODHE catalysts, but also to conduct research on new process technologies. Publicly available data indicates that at room temperature and pressure, the explosion limits of ethane in air (i.e., ethane + oxygen + nitrogen) are 3.0%-15.5%, while the explosion limits in oxygen (i.e., ethane + oxygen) expand to 3.0%-66.0%. In particular, since ODHE is usually a high-temperature, non-pressure process, ethane will inevitably have an even wider explosion limit in oxygen (see Table 1). If the ethane concentration in the ODHE process is below its lower explosive limit (i.e., less than 3%), its concentration in the feedstock will be too low to achieve a high ethylene space-time yield, which is obviously uneconomical. Therefore, the usual practice is to maintain the ethane concentration above its upper explosive limit. Since ODHE is a strongly exothermic process, as described in patents CN113860985A and CN113831207A, the conventional practice is to use a large amount of diluent (such as nitrogen) in the feedstock to reduce process safety risks and improve heat transfer efficiency. The aim is to balance process safety with important economic indicators affecting the ODHE process, such as ethylene selectivity, ethane conversion rate, and ethylene space-time yield. Patents CN105080575B, CN110963880A, and CN1109...

[0011] Methods using inert gases such as water vapor, nitrogen, and carbon dioxide as diluents are disclosed in CN106660901B, CN105727975B, etc. According to publicly available information, the addition of these diluents poses challenges to the separation and industrial application of this technology: Using water vapor as the diluent gas has the advantage of separating the diluent gas from the product gas through cooling, and the separation energy consumption is relatively lower than using nitrogen as the diluent. The disadvantage is that the presence of water vapor in the feed gas will greatly increase the selectivity of the by-product acetic acid, thereby reducing the effective utilization rate when the feed gas is used to produce ethylene. Using CO2 as the diluent gas will result in a large amount of CO2 being absorbed, desorbed, and then recycled back to the reactor, resulting in high energy consumption in the decarbonization unit. Furthermore, the desorbed CO2 is at atmospheric pressure, and the energy consumption and equipment investment for compressing and recycling it back to the reactor are relatively high. A large amount of CO2 needs to be introduced during start-up, and the source of the material is limited. Using nitrogen as the diluent gas has the advantage of improving the selectivity of ethylene, but it will result in a large amount of nitrogen being mixed with ethane and ethylene. If a cryogenic separation method is adopted, it is necessary to pressurize to a very high pressure (above 3.0 MPa) and cool to below -100°C. The compressor pressure ratio is large, and the required cold energy grade is high, resulting in a large number of equipment, high investment, and high separation energy consumption. Therefore, developing a new ODHE process that uses pure oxygen directly without any diluents in the raw materials is particularly important and challenging.

[0012] Table 1. Explosion limits of ethane in pure oxygen under various operating conditions

[0013]

[0014] In the method and system of the present invention, if there are multiple reactors, the reactors are connected in series. Existing public information indicates that the conventional connection method between reactors in the art is parallel connection. For example, CN110225900A discloses that its reaction unit "may include a or more reactors, for example, operating in parallel," and CN112142547A similarly discloses that the reactors are connected in parallel. Summary of the Invention

[0015] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a multi-stage series reaction process and system for the catalytic oxidative dehydrogenation of ethane to produce ethylene and acetic acid without diluent. No diluent is needed in the raw materials; only oxygen is required as the oxidant. A staged oxygen supplementation strategy and a multi-stage series reactor achieve high selectivity for ethylene conversion. Specifically, using oxygen without any diluent, ethane and oxygen are mixed in a certain proportion under safe operating conditions and continuously passed through a multi-stage series oxidative dehydrogenation catalyst bed to undergo a catalytic oxidative dehydrogenation reaction. Subsequent conventional multi-stage separation yields ethylene and acetic acid products that meet the national standards for industrial ethylene (GB / T 7715-2014) and industrial glacial acetic acid (GB / T1628-2020). The method and system provided by this invention ensure process safety and achieve very high ethylene product selectivity and space-time yield, ultimately reducing raw material consumption, production energy consumption, and equipment investment.

[0016] The inventors also recognized that in the ethane oxidation reaction, the use of a highly ethylene-selective catalyst as described in patent CN105080575B (application number CN2014101988672) and suitable reaction conditions (such as a low oxygen to ethane ratio) are crucial for heat control of the reaction process. As described below, the exothermic intensities of side reactions 1, 2, and 3 are 5.7 times, 8.3 times, and 13.7 times that of the main reaction, respectively. This is precisely one of the starting points of this invention.

[0017] Main reaction: C2H6 + 0.5O2 = C2H4 + H2O, Δ r H m = -104kJ / mol

[0018] Side reaction 1: C2H6 + 1.5O2 = C2H4O2 + H2O, Δ r H m = -591kJ / mol

[0019] Side reaction 2: C2H6 + 2.5O2 = 2CO + 3H2O, Δ r H m = -863kJ / mol

[0020] Side reaction 3: C2H6 + 3.5O2 = CO2 + 3H2O, Δ r H m = -1429kJ / mol

[0021] This invention is achieved through the following technical solution:

[0022] One of the technical solutions of the present invention is to provide a multi-stage series reaction process for the catalytic oxidative dehydrogenation of ethane to produce ethylene and acetic acid without diluent, wherein the feed gas does not contain diluent and the oxidant is oxygen.

[0023] Based on the above technical solution, further, the reactor is a fixed-bed reactor. If there are two or more reactors, the reactors are connected in series, and oxygen needs to be added before each reactor.

[0024] Based on the above technical solution, the method further includes the following steps:

[0025] 1) The ethane stream and oxygen stream are preheated separately and then mixed before entering the reactor together for oxidative dehydrogenation. If there are two or more reactors, the mixture is added at the outlet of the preceding reactor and then enters the subsequent reactor to continue the oxidative dehydrogenation reaction, yielding the final process product gas a.

[0026] 2) The final reaction product gas a from step 1) is subjected to quenching to remove acetic acid and water, yielding process product gas b after acid removal. The acetic acid in b is then recovered or treated to remove the acid water. The quenching, acetic acid and water removal, acetic acid recovery, or acid water treatment can be performed using any conventional technique in the art.

[0027] 3) The process product gas b described in step 2) is subjected to oxygen removal treatment to obtain process product gas c. The oxygen removal treatment can employ any conventional technique in the art, including but not limited to catalytic oxidation technology;

[0028] 4) The process product gas c described in step 3) is subjected to carbon dioxide removal treatment to obtain process product gas d. The carbon dioxide removal treatment can employ any conventional technique in the art, including but not limited to washing with organic amines followed by alkaline washing;

[0029] 5) The process product gas d described in step 4) is dried, subjected to multi-stage compression and cryogenic treatment to obtain process product gas e. The drying, multi-stage compression and cryogenic treatment can be performed using any conventional technique in the art.

[0030] 6) The process product gas e from step 5) is subjected to ethane removal treatment to obtain process product gas f at the top of the column and ethane at the bottom of the column. The so-called ethane removal treatment can employ any conventional technique in the art.

[0031] 7) The ethane described in step 6) is returned to the ethane preheater in step 1) of the present invention for preheating, and continues to undergo oxidative dehydrogenation reaction as a raw material.

[0032] 8) The process product gas f described in step 6) is subjected to ethylene distillation to obtain tail gas at the top of the column and ethylene product at the bottom. The ethylene distillation process can be performed using any conventional technique in the art.

[0033] 9) Treat the exhaust gas described in step 8). The exhaust gas treatment can employ any conventional technology in the art, including but not limited to flare treatment.

[0034] Based on the above technical solution, further, in step 1), the mixed raw materials entering the first reactor do not need to contain any diluent.

[0035] Based on the above technical solution, furthermore, the catalytic reaction of ethane oxidative dehydrogenation to ethylene is carried out in a multi-stage series reactor. The multi-stage series reactor includes the special case of having only one fixed-bed reactor. The reactor is a fixed-bed reactor, preferably a tubular fixed-bed reactor.

[0036] Based on the above technical solution, furthermore, the mass ratio of oxygen to the total amount of flammable and explosive substances at the reactor inlet is 0.01 to 0.55. The flammable and explosive substances mentioned in this invention include, but are not limited to, ethane, ethylene, carbon monoxide, and acetic acid. In the first reactor, it refers to ethane; in the second or subsequent series reactors, it refers to ethylene, acetic acid, CO, and unreacted residual ethane in the product. The inlet temperature of any fixed-bed reactor is 100℃ to 400℃, preferably 150℃ to 300℃; the inlet pressure of any fixed-bed reactor is 0.10 MPa to 1.0 MPa, preferably 0.20 to 0.70 MPa.

[0037] Based on the above technical solutions, furthermore, when there are two or more reactors, the single-pass conversion rate of ethane and the content of acetic acid products will increase significantly.

[0038] Based on the above technical solution, further, after acetic acid recovery in step 2), the acetic acid product meets the national standard for industrial glacial acetic acid (GB / T 1628-2020).

[0039] Based on the above technical solution, further, after the ethylene distillation treatment in step 7), the ethylene product conforms to the national standard for industrial ethylene (GB / T 7715-2014).

[0040] The second technical solution of the present invention provides a multi-stage series reaction process system for the catalytic oxidative dehydrogenation of ethane to ethylene and acetic acid without diluent, used in the above-mentioned process method, such as... Figure 1 As shown, it mainly includes:

[0041] Preheaters for preheating oxygen and ethane streams, including an oxygen preheater (801-1) and an ethane preheater (801-2);

[0042] A quenching unit (802-1) for rapidly cooling the process product gas from the last reactor, such as a quencher;

[0043] The hot mixed feedstock stream is passed through a reactor (803-1) packed with an ethane oxidative dehydrogenation catalyst, and a subsequent reactor (803-i), where i is 2-4, and can be 2, 3, or 4.

[0044] An acid removal unit (804) for removing acid water from the process product gas stream a, for example, an acid removal device;

[0045] A unit (805) for removing oxygen from the process gas product stream b, such as an oxygen removal device;

[0046] A unit (806) for removing CO2 from the process gas product stream c, such as a CO2 removal device;

[0047] A unit (807) for drying, multi-stage compression and cryogenic treatment of the process gas product stream d, such as a drying, multi-stage compression and cryogenic treatment device;

[0048] A unit (808) for removing ethane from the process gas product stream e, such as an ethane removal device;

[0049] Equipment (809) for ethylene distillation of the process gas product stream f.

[0050] Overall, the features and advantages of this invention are as follows, compared with the prior art:

[0051] a) Using the method and system provided by this invention, nitrogen or water is not used as a diluent in the raw materials; oxygen is almost completely converted in any reactor, that is, the oxygen content in the tail gas after each reactor is very low, the subsequent deoxygenation equipment unit is small, and the process safety is high.

[0052] b) The reactor can be connected in multiple stages, which means that the ethane single-pass conversion level and product selectivity of the unit can be flexibly adjusted as needed. That is, the ratio of ethylene and acetic acid products can be adjusted at the same time to better adapt to market changes.

[0053] c) Using the method and system provided by the present invention, the ethane oxidation reaction on the catalyst can be operated with high stability.

[0054] d) The method and system provided by this invention provide a particularly high product selectivity, especially for ethylene, and low raw material consumption.

[0055] e) The method and system provided by this invention have a short production route, simple product composition, low production energy consumption, and low carbon emissions (mainly carbon monoxide and carbon dioxide). Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the system structure of the multi-stage series non-dilution process for the catalytic oxidative dehydrogenation of ethane to ethylene of the present invention.

[0057] Figure 1 Explanation of the flow codes: a represents the effluent after the last reactor; b represents the process gas flow after acid removal from a; c represents the mixture flow after oxygen removal from b; d represents the gaseous mixture after acid removal from c, containing ethane, ethylene, and carbon monoxide; e represents the mixture flow after drying, multi-stage compression, and cryogenic treatment from d; f represents the mixture flow distilled from the top of the column, containing ethylene and carbon monoxide; tail gas represents the carbon monoxide distilled from the top of the column. Other flow codes are described in the attached diagram.

[0058] Figure 1 Equipment numbering explanation: 801-1 represents an oxygen preheater; 801-2 represents an ethane preheater; 802-1 is a quench cooler connected to the last fixed-bed reactor and the acid water removal unit; 803-1 represents the first fixed-bed reactor; 803-i represents the i-th possible fixed-bed reactor; 804 represents the acid water removal unit; 805 represents the oxygen removal unit; 806 represents the CO2 removal unit; 807 represents the drying, multi-stage compression, and cryogenic separation equipment unit; 808 represents the ethane removal tower; 809 represents the ethylene distillation tower.

[0059] Figure 2 This is a schematic diagram of the system structure of the single-reactor non-dilution process for the catalytic oxidative dehydrogenation of ethane to ethylene of the present invention.

[0060] Figure 2 Explanation of the flow codes: a represents the effluent from the fixed-bed reactor (including but not limited to unconverted ethane, unconverted oxygen, ethylene, acetic acid, carbon monoxide, carbon dioxide, and water); b represents the process gas flow after acid removal from a; c represents the mixture flow from b after oxygen removal; d represents the gaseous mixture from c after acid removal, containing ethane, ethylene, and carbon monoxide; e represents the mixture flow from d after drying, multi-stage compression, and cryogenic treatment; f represents the mixture flow from the top of the column, containing ethylene and carbon monoxide; tail gas represents the carbon monoxide distilled from the top of the column. Other flow codes are described in the attached diagram.

[0061] Figure 2 Equipment numbering explanation: 801-1 represents an oxygen preheater; 801-2 represents an ethane preheater; 802-1 is a quench cooler connected to a fixed-bed reactor and an acid water removal unit; 803-1 represents a fixed-bed reactor; 804 represents an acid water removal unit; 805 represents an oxygen removal unit; 806 represents a CO2 removal unit; 807 represents a drying, multi-stage compression, and cryogenic separation equipment unit; 808 represents an ethane removal tower; 809 represents an ethylene distillation tower.

[0062] Figure 3 This is a schematic diagram of the system structure of the non-dilution process with two reactors connected in series for the catalytic oxidative dehydrogenation of ethane to ethylene according to the present invention.

[0063] Figure 3 Explanation of the flow codes: a represents the product gas after passing through the second reactor; b represents the process gas flow after acid removal from a; c represents the mixture flow after oxygen removal from b; d represents the gaseous mixture after acid removal from c, containing ethane, ethylene, and carbon monoxide; e represents the mixture flow after drying, multi-stage compression, and cryogenic treatment of d; f represents the mixture flow distilled from the top of the column, containing ethylene and carbon monoxide; tail gas represents the carbon monoxide distilled from the top of the column. Other flow codes are described in the attached diagram.

[0064] Figure 3 Equipment numbering explanation: 801-1 represents an oxygen preheater; 801-2 represents an ethane preheater; 802-1 is a quench cooler connected to the second fixed-bed reactor and the acid water removal unit; 803-1 represents the first fixed-bed reactor, and 803-2 represents the second fixed-bed reactor; 804 represents the acid water removal unit; 805 represents the oxygen removal unit; 806 represents the CO2 removal unit; 807 represents the drying, multi-stage compression, and cryogenic separation equipment unit; 808 represents the ethane removal tower; and 809 represents the ethylene distillation tower. Detailed Implementation

[0065] In the description of this invention, the number of reactors is expressed as "multi-stage", which also includes the case of using only one reactor.

[0066] In the description of this invention, "pressure" is a conventional term, but its true meaning is "pressure intensity," which refers to absolute pressure (absolute pressure).

[0067] In the description of this invention, the hierarchy is as follows: system → unit → device.

[0068] Unless otherwise specified, the devices or processing techniques used in the following embodiments are common devices or techniques in the art.

[0069] In the description of this invention, it should be further noted that the structures, proportions, and sizes illustrated in the accompanying drawings are presented in a concise manner and are only used to complement the content disclosed in the specification for those skilled in the art to understand and read. They are not intended to limit the conditions under which this invention can be implemented and therefore have no substantial technical significance. Any structural modifications, changes in proportions, or adjustments in size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention. Terms used in this invention to indicate orientation or positional relationships, such as "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "outer," refer to the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are only used to describe the sequence of devices and should not be construed as indicating or implying their relative importance.

[0070] In the description of this invention, for the sake of clarity of the process diagram, the heat exchange process is not specifically marked, such as the heat released during the ethane oxidative dehydrogenation reaction being recovered to heat various raw materials to achieve the purpose of preheating the raw materials.

[0071] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "connected" or "linked" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection, a direct connection, an indirect connection via an intermediate medium, internal communication between two components, or any combination of the above connections. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0072] Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0073] The following details the multi-stage tandem non-dilution process method and system for the catalytic oxidative dehydrogenation of ethane to ethylene according to the present invention.

[0074] Example 1

[0075] like Figure 2As shown, fresh ethane with a flow rate of 21.6 t / h and recycled ethane with a flow rate of 75.6 t / h are mixed and preheated. Oxygen with a flow rate of 11.5 t / h is preheated and thoroughly mixed with the ethane before entering a fixed-bed reactor for oxidative dehydrogenation. The fixed bed is a tubular fixed-bed reactor. The tubular fixed-bed reactor is divided into a hot side and a cold side. The mixed gas of ethane and oxygen enters the hot side of the reactor, which is filled with a ring-shaped catalyst, the active component of which is MoVTeNbO as described in patent CN2014101988672. Circulating molten salt is fed to the cold side of the reactor. After absorbing the exothermic reaction from the oxidative dehydrogenation, it is cooled by a heat exchanger and then recycled back to the cold side of the reactor. The molten salt can be any molten salt system known to those skilled in the art, preferably potassium or sodium nitrates and nitrites. Ethane and oxygen react in this reactor to produce ethylene, acetic acid, carbon monoxide, carbon dioxide, and water. The reactor effluent also contains unconverted ethane and trace amounts of oxygen. The flow rates are: ethylene 15.3 t / h, ethane 80.0 t / h, oxygen 1.3 t / h, acetic acid 1.2 t / h, CO 0.2 t / h, CO2 0.2 t / h, and water 10.5 t / h. The reactor inlet feed temperature is 190℃, and the molten salt operating temperature is 310℃.

[0076] After heat recovery from the reactor effluent (a), the product passes through an acid removal unit, a CO2 absorption unit, and subsequent cooling, drying, and multi-stage compression before entering an ethane separation and recycling unit and finally an ethylene distillation unit. The above separation process is conventional technology in this field. The final product is glacial acetic acid with a purity of 99.5% (national standard for industrial glacial acetic acid). <gb t1628-2020>) and polymer-grade ethylene products with a purity of 99.7% containing trace amounts of ethane (National Standard for Industrial Ethylene)<GB / T 7715-2014> ).

[0077] Through the process described in this embodiment, the oxygen conversion rate is 98.5%, the ethylene selectivity is 95.5%, the ethylene space-time production rate is 1.6 kg ethylene / kg catalyst / hour; the comprehensive energy consumption is 156 kg standard oil tonnes of ethylene, and the ethane feedstock consumption is 1.12 kg ethane / kg ethylene.

[0078] Example 2

[0079] like Figure 3 As shown, fresh ethane with a flow rate of 21.6 t / h and recycled ethane with a flow rate of 75.6 t / h are mixed and preheated. Oxygen with a flow rate of 11.5 t / h is preheated and thoroughly mixed with the ethane before entering a fixed-bed reactor for oxidative dehydrogenation. The fixed bed is a tubular fixed-bed reactor. The tubular fixed-bed reactor is divided into a hot side and a cold side. The mixed gas of ethane and oxygen enters the hot side of the reactor, which is filled with a ring-shaped catalyst, the active component of which is MoVTeNbO as described in patent CN2014101988672. Circulating molten salt is fed to the cold side of the reactor. After absorbing the exothermic reaction from the oxidative dehydrogenation, it is cooled by a heat exchanger and then recycled back to the cold side of the reactor. The molten salt can be any molten salt system known to those skilled in the art, preferably potassium or sodium nitrates and nitrites. Ethane and oxygen react in this reactor to produce ethylene, acetic acid, carbon monoxide, carbon dioxide, and water. The reactor effluent also contains unconverted ethane and trace amounts of oxygen. The inlet feed temperature of the first reactor is 190°C, and the molten salt operating temperature is 310°C. After preheating and thoroughly mixing the reactor effluent with supplemental oxygen at a flow rate of 11.5 t / h, it enters the hot side of a second tubular fixed-bed reactor. The hot side is packed with a ring-shaped catalyst, the active component of which is MoVTeNbO as described in patent CN201410198867. The second reactor uses the same circulating molten salt as the first reactor, with an inlet feed temperature of 190°C and a molten salt operating temperature of 310°C. The mixed product stream passing through the second tubular fixed-bed reactor includes ethylene, acetic acid, carbon monoxide, carbon dioxide, and water. The reactor effluent also contains unconverted ethane and trace amounts of oxygen. The flow rates are as follows: ethylene 28.0 t / h, ethane 64.7 t / h, oxygen 2.2 t / h, acetic acid 3.8 t / h, CO 0.7 t / h, CO2 0.7 t / h, and water 20.2 t / h.

[0080] After heat recovery from the reactor effluent (a), the product passes through an acid removal unit, a CO2 absorption unit, and subsequent cooling, drying, and multi-stage compression before entering an ethane separation and recycling unit and finally an ethylene distillation unit. The above separation process is conventional technology in this field. The final product is glacial acetic acid with a purity of 99.8% (national standard for industrial glacial acetic acid). <gb t1628-2020>It also includes polymer-grade ethylene products with a purity of 99.9% containing trace amounts of ethane, conforming to the national standard for industrial ethylene (GB / T 7715-2014).

[0081] Through the process described in this embodiment, the oxygen conversion rate is 99.1%, the ethylene selectivity is 92.5%, the ethylene space-time production rate is 1.2 kg ethylene / kg catalyst / hour; the comprehensive energy consumption is 110 kg standard oil / ton of ethylene, and the ethane feedstock consumption is 1.16 kg ethane / kg ethylene.

[0082] Example 3

[0083] like Figure 2 As shown, fresh ethane with a flow rate of 22.7 t / h and recycled ethane with a flow rate of 62.3 t / h are mixed and preheated. Oxygen with a flow rate of 16.5 t / h is preheated and thoroughly mixed with the ethane before entering a fixed-bed reactor for oxidative dehydrogenation. The fixed bed is a tubular fixed-bed reactor. The tubular fixed-bed reactor is divided into a hot side and a cold side. The mixed gas of ethane and oxygen enters the hot side of the reactor, which is filled with a ring-shaped catalyst, the active component of which is MoVTeNbO as described in patent CN2014101988672. Circulating molten salt is fed to the cold side of the reactor. After absorbing the exothermic reaction from the oxidative dehydrogenation, it is cooled by a heat exchanger and then recycled back to the cold side of the reactor. The molten salt can be any molten salt system known to those skilled in the art, preferably potassium or sodium nitrates and nitrites. Ethane and oxygen react in this reactor to produce ethylene, acetic acid, carbon monoxide, carbon dioxide, water, and methane. The reactor effluent also contains unconverted ethane and trace amounts of oxygen. The reactor inlet feed temperature is 190°C, and the molten salt operating temperature is 310°C. The mixed product stream from the tubular fixed-bed reactor includes ethylene, acetic acid, carbon monoxide, carbon dioxide, and water. The reactor effluent also contains unconverted ethane and oxygen. The flow rates are: ethylene 20.2 t / h, ethane 62.3 t / h, oxygen 2.91 t / h, acetic acid 1.6 t / h, CO 0.30 t / h, CO2 0.27 t / h, and water 13.9 t / h.

[0084] After recovering the heat from the reactor effluent (a), the product passes through an acid removal unit, an oxygen removal unit, a CO2 absorption unit, and subsequent cooling, drying, and multi-stage compression before entering an ethane separation and recycling unit, an ethylene distillation unit, and finally a methane removal and recycling unit. The above separation process is conventional technology in this field. Finally, a glacial acetic acid product with a purity of 99.8% (national standard for industrial glacial acetic acid) is obtained. <gb t1628-2020>It also includes polymer-grade ethylene products with a purity of 99.9% containing trace amounts of ethane, conforming to the national standard for industrial ethylene (GB / T 7715-2014).

[0085] Through the process described in this embodiment, the oxygen conversion rate is 98.2%, the ethylene selectivity is 93.6%, the ethylene space-time production rate is 1.3 kg ethylene / kg catalyst / hour, the comprehensive energy consumption is 90 kg standard oil / ton of ethylene, and the ethane feedstock consumption is 1.13 kg ethane / kg ethylene.

[0086] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be included in the claims of the present invention.< / gb> < / gb> < / gb>

Claims

1. A multi-stage tandem reaction process for the catalytic oxidative dehydrogenation of ethane to ethylene and acetic acid without diluent, characterized in that, The process method uses oxygen as the oxidant and the raw gas does not contain a diluent. The process includes the following steps: 1) The ethane stream and oxygen stream are preheated separately and then mixed together before entering the reactor to undergo an oxidative dehydrogenation reaction, resulting in the final process product gas a. If there are two or more reactors, the mixture is mixed with the added oxygen at the outlet of the preceding reactor to obtain a mixed stream, which enters the subsequent reactor to continue the oxidative dehydrogenation reaction, resulting in the final process product gas a. The mass ratio of oxygen to the total mass of flammable and explosive substances at the reactor inlet is 0.01 to 0.55:1; the flammable and explosive substances include ethane, ethylene, carbon monoxide, and acetic acid. The active component of the catalyst used in the oxidative dehydrogenation reaction is MoVTeNbO; 2) The final reaction product gas a described in step 1) is subjected to rapid cooling to remove acetic acid and water, and process product gas b with acid water removed is obtained. The acetic acid in the gas is then recovered or treated with acid water. 3) Deoxygenate the process product gas b described in step 2) to obtain process product gas c; 4) The process product gas c described in step 3) is subjected to carbon dioxide removal treatment to obtain process product gas d; 5) The process product gas d described in step 4) is dried, multi-stage compressed, and cryogenically treated to obtain process product gas e; 6) The process product gas e from step 5) is subjected to ethane removal treatment to obtain process product gas f at the top of the column and ethane at the bottom of the column; 7) The ethane described in step 6) is returned to the ethane preheater in step 1) for preheating, and used as a raw material to continue the oxidative dehydrogenation reaction; 8) The process product gas f described in step 6) is subjected to ethylene distillation to obtain tail gas at the top of the column and ethylene product at the bottom of the column; 9) Treat the exhaust gas described in step 8) as waste gas.

2. The process method according to claim 1, characterized in that, The reactors in the process are fixed-bed reactors, with two or more reactors connected in series, and oxygen needs to be added before each reactor.

3. The process method according to claim 1 or 2, characterized in that, The inlet temperature of any fixed-bed reactor is 150℃~300℃; the inlet pressure of any fixed-bed reactor is 0.10~1.0 MPa.

4. The process method according to claim 3, characterized in that, The inlet pressure of any fixed-bed reactor is 0.20-0.70 MPa.

5. The process method according to claim 1, characterized in that, In step 3), the deoxygenation treatment includes catalytic oxidation technology; In step 4), the carbon dioxide removal treatment includes washing with organic amines followed by washing with alkali. In step 9), the waste gas treatment includes flare treatment.

6. The process method according to claim 1, characterized in that, After step 2), the acetic acid product conforms to the national standard GB / T 1628-2020 for industrial glacial acetic acid. After the ethylene distillation process in step 8), the ethylene product conforms to the national standard GB / T 7715-2014 for industrial ethylene.

7. A process for the catalytic oxidative dehydrogenation of ethane to ethylene and acetic acid without diluent, characterized in that, The catalytic reaction for the oxidative dehydrogenation of ethane to ethylene is carried out in a reactor, which is a single fixed-bed reactor. The process method uses oxygen as the oxidant and the raw gas does not contain a diluent. The process includes the following steps: 1) The ethane stream and oxygen stream are preheated separately and then mixed together before entering the reactor to undergo an oxidative dehydrogenation reaction, yielding the final process product gas a. The mass ratio of oxygen to the total mass of flammable and explosive substances at the reactor inlet is 0.01 to 0.55:1; the flammable and explosive substances include ethane, ethylene, carbon monoxide, and acetic acid. The active component of the catalyst used in the oxidative dehydrogenation reaction is MoVTeNbO; 2) The final reaction product gas a described in step 1) is subjected to rapid cooling to remove acetic acid and water, and process product gas b with acid water removed is obtained. The acetic acid in the gas is then recovered or treated with acid water. 3) Deoxygenate the process product gas b described in step 2) to obtain process product gas c; 4) The process product gas c described in step 3) is subjected to carbon dioxide removal treatment to obtain process product gas d; 5) The process product gas d described in step 4) is dried, multi-stage compressed, and cryogenically treated to obtain process product gas e; 6) The process product gas e from step 5) is subjected to ethane removal treatment to obtain process product gas f at the top of the column and ethane at the bottom of the column; 7) The ethane described in step 6) is returned to the ethane preheater in step 1) for preheating, and used as a raw material to continue the oxidative dehydrogenation reaction; 8) The process product gas f described in step 6) is subjected to ethylene distillation to obtain tail gas at the top of the column and ethylene product at the bottom of the column; 9) Treat the exhaust gas described in step 8) as waste gas.

8. The process method according to claim 7, characterized in that, The fixed-bed reactor is a tubular fixed-bed reactor.

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