Multistage cascade reaction process method and system for preparing ethylene and acetic acid through catalytic oxidative dehydrogenation of ethane without diluent

Abstract

The invention relates to a preparation technology of ethylene and acetic acid in organic chemical industry, in particular to a multi-stage series non-dilution process method and system for preparing ethylene and acetic acid from ethane through catalytic oxidative dehydrogenation. Compared with the prior art, the method and the system provided by the invention have the advantages that nitrogen or water is not used as a diluent in the raw materials; oxygen in any reactor is almost completely converted, namely the oxygen content in tail gas of each reactor is very low, and the process safety is high. The reactors can be connected in series in a multi-stage manner, namely, the ethane one-way conversion level of the device can be flexibly regulated and controlled according to requirements, and meanwhile, the proportion of ethylene and acetic acid can be regulated and changed so as to better adapt to market changes. The method and the system provided by the invention have the advantages of high ethylene molar selectivity and low raw material unit consumption. The method and the system provided by the invention have the advantages of low production energy consumption and less production wastes (mainly referring to carbon monoxide and carbon dioxide).

Description

Technical Field

[0001] The present 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 method and system for preparing ethylene and acetic acid by catalytic oxidative dehydrogenation of ethane without diluent in the raw material. Background Art

[0002] Ethylene is one of the world's largest consumer goods and chemicals, and the world's highest-yielding organic chemical raw material. It is known as the "mother of the petrochemical industry", a basic raw material for petrochemicals, and an important indicator of a country's petrochemical industry level. In 2022, the global ethylene production capacity reached 210 million tons, with an output of 197 million tons. Since the development and completion of the first cracking ethylene unit by Union Carbide in 1923, global ethylene production has relied mainly on steam cracking technology for nearly a hundred years. Today, more than 90% of the world's ethylene is produced by steam cracking. Depending on the reaction raw materials, the development of steam cracking technology can be roughly divided into two stages: the first stage is from the birth of steam cracking technology to the beginning of this century, naphtha, which has a price advantage and is easy to store and transport, has always been the main raw material for steam cracking; the second stage is since the US shale gas revolution in 2010, due to the substantial increase in the supply of low-carbon alkanes such as ethane and the continuous decline in prices, steam cracking of ethylene using ethane as raw material has become the most competitive ethylene production process route. In addition, ethylene is currently the most productive organic chemical raw material, and it also consumes the most energy in production (production energy consumption is as high as 2.0×10 15 kJ / year) and the organic chemical product with the most associated greenhouse gases, so the innovation of its process technology will also have a profound impact on the global energy and environmental pattern. Although the comprehensive production cost of ethane cracking to ethylene is the lowest, the process is still a highly energy-intensive, highly polluting and strongly endothermic process, and the operating temperature usually needs to be above 800°C (Equation 1). Therefore, the development of a more advanced new process for ethylene production is of great strategic significance. The catalytic oxidative dehydrogenation of ethane (ODHE) to ethylene technology is a spontaneous energy-saving process that is not restricted by thermodynamic equilibrium and can theoretically be carried out at room temperature (Equation 2). Based on the important pillar status of ethylene in the national economy and the increasingly urgent global environmental protection needs, it will be very necessary to develop new technologies for the directional conversion of ethane to ethylene with low energy consumption and low carbon emissions.

[0003] Acetic acid (acetic acid) can not only be used in food processing, but also is an important chemical raw material intermediate. It is mainly used to produce purified terephthalic acid (PTA), vinyl acetate, acetate esters, acetic anhydride, chloroacetic acid and other compounds. It can be used as industrial solvents and raw materials for pesticides, medicines and dyes. It is widely used in fabric printing and dyeing, photographic drug manufacturing and rubber industry. At present, the largest downstream demand for acetic acid is PTA, accounting for about 30% of the total consumption, and it is an important chemical fiber raw material for the polyester industry. In 2020, China's acetic acid production and consumption accounted for 53.4% ​​and 45.8% of the world's total, respectively, making it the world's largest acetic acid producer and consumer.

[0004] With the development of the acetic acid industry and the rapid expansion of its scale, the acetic acid production process has also been continuously updated. According to the different raw materials, the production process routes of acetic acid can be divided into acetylene, ethanol, ethylene, butane or light oil routes, and methanol routes. The acetylene, ethanol and ethylene raw material routes specifically oxidize acetylene, ethanol and ethylene to produce acetaldehyde, and then further oxidize acetaldehyde to produce acetic acid. The methanol route has become the main acetic acid production process at present with its mature technical advantages and cost advantages. The output of acetic acid produced by this method accounts for more than 90% of the total acetic acid production capacity, but the process is cumbersome, the investment cost is high, and the catalyst used contains iodine and is toxic. Therefore, it is necessary to find new process technologies. In 1978, Thorsteinson et al. reported the use of Mo-V catalysts to directly oxidize ethane to produce acetic acid under pressurized conditions, thus opening up the study of ethane selective oxidation to prepare acetic acid. Existing public information shows that the selective oxidation of ethane to acetic acid is to use ethane and oxygen in the air (or air) to directly generate acetic acid at 200-300°C and under pressure. Water vapor is usually added to the reaction system to improve the selectivity of acetic acid. Although the addition of water is beneficial to improve the selectivity of acetic acid, it is bound to increase the separation energy consumption. One advantage of the present invention is that no diluent including water is added to the raw gas, and ethane is used as the raw material to produce acetic acid while mainly obtaining ethylene products (Equation 3).

[0005] Direct dehydrogenation of ethane to ethylene process:

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

[0007] Ethane oxidative dehydrogenation process to ethylene:

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

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

[0010] ODHE has been extensively studied in recent decades. The introduction of oxygen thermodynamically supports the formation of deep oxidation products such as CO and CO2, but it also poses a great challenge to the safety of the process. Therefore, it is necessary not only to develop highly selective ODHE catalysts, but also to conduct new process research. Public data show that at normal temperature and pressure, the explosion limit of ethane in air (i.e., ethane + oxygen + nitrogen) is 3.0%-15.5%, while the explosion limit in oxygen (i.e., ethane + oxygen) is expanded to 3.0%-66.0%. In particular, ODHE is usually a high-temperature and non-normal pressure process, so ethane in oxygen will inevitably have a wider explosion limit (see Table 1). If the ethane concentration in the ODHE process is lower than its lower explosion limit (i.e., less than 3%), its concentration in the raw material will be too low, and a high ethylene space-time yield cannot be obtained, which is obviously uneconomical. Therefore, the usual practice is to keep the ethane concentration above its upper explosion limit. Because ODHE is a highly exothermic process, as described in patents CN113860985A and CN113831207A, a large amount of diluent (such as nitrogen) must be used in the raw material to reduce the process safety risk and improve the heat transfer efficiency. That is, the purpose is to take into account important indicators that affect the economic efficiency of the ODHE process, such as ethylene selectivity, ethane conversion rate, and ethylene space-time yield, while maintaining process safety. Patents CN105080575B, CN110963880A, CN1109

[0011] 63879A, CN106660901B, CN105727975B, etc. all disclose methods of using inert gases such as water vapor, nitrogen, carbon dioxide, etc. as diluents. According to the existing public information, the addition of these diluents has brought challenges to the separation and industrial application of this technology: the advantage of using water vapor as a diluent gas is that the diluent gas and the product gas can be separated by cooling, and the separation energy consumption is relatively low compared to using nitrogen as a diluent. The disadvantage is that the presence of water vapor in the raw gas will greatly increase the selectivity of the by-product acetic acid, thereby reducing the effective utilization rate of the raw material when producing ethylene; using CO2 as a diluent gas will cause a large amount of CO2 to be recycled back to the reactor after absorption and desorption. The decarbonization unit has high energy consumption, and the desorbed CO2 is a normal pressure gas. The energy consumption and equipment investment of compressing and recycling it back to the reactor are relatively high. A large amount of CO2 needs to be introduced during startup, and its material source is limited; the advantage of using nitrogen as a diluent gas is that it is conducive to improving the selectivity of ethylene, but it will cause a large amount of nitrogen to be mixed with ethane and ethylene. If a deep cold separation method is used, it needs to be pressurized to a very high pressure (above 3.0MPa) and cooled to below -100°C. The compressor has a large pressure ratio and the required cooling capacity is of high quality, resulting in a large number of equipment, high investment, and high separation energy consumption. Therefore, it is particularly important and challenging to develop a new ODHE process that directly uses pure oxygen without any diluent in the raw material.

[0012] Table 1. Upper explosion limit of ethane in pure oxygen under various working conditions

[0013]

[0014] In the method and system of the present invention, if there are multiple reactors, the connection relationship between the reactors is in series. Existing public information shows that the conventional connection mode between reactors in the art is parallel connection, such as CN110225900A discloses that its reaction unit "may include one or more reactors, for example, operated in parallel", and CN112142547A also discloses that the connection relationship between the reactors is parallel connection. Summary of the invention

[0015] In view of the shortcomings of the prior art described above, the object of the present invention is to provide a multi-stage series reaction process method and system for catalytic oxidative dehydrogenation of ethane to produce ethylene and acetic acid without diluent, wherein no diluent is required in the raw material, only oxygen is used as the oxidant, and the strategy of adding oxygen in stages and the reactors are connected in series to achieve high selectivity for conversion into ethylene, that is, oxygen without any diluent is used, ethane and oxygen are mixed in a certain proportion under safe operating conditions, and then continuously pass through the multi-stage series oxidative dehydrogenation catalyst bed to produce catalytic oxidative dehydrogenation reaction, and then undergo subsequent conventional multi-stage separation to finally obtain ethylene products 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 the present invention can ensure process safety on the one hand, and the selectivity of ethylene products and the time-space yield of ethylene products on the other hand are very high, and finally achieve the purpose of reducing raw material unit consumption, production energy consumption and equipment investment.

[0016] The inventors also recognize that in the ethane oxidation reaction, the use of a high ethylene selectivity catalyst as described in patent CN105080575B (application number CN2014101988672) and suitable reaction conditions (such as a low oxygen to ethane ratio) are crucial to the heat control of the reaction process. For the four reactions described below, the exothermic intensity of side reaction 1, side reaction 2 and side reaction 3 is 5.7 times, 8.3 times and 13.7 times that of the main reaction, respectively. This is exactly a starting point of the present invention.

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

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

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

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

[0021] The present invention is achieved through the following technical solutions:

[0022] One of the technical solutions of the present invention is to provide a multi-stage series reaction process for catalytic oxidative dehydrogenation of ethane to produce ethylene and acetic acid without diluent, wherein the raw 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 the number of reactors is 2 or more, the reactors are connected in series, and oxygen needs to be added before each reactor.

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

[0025] 1) The ethane stream and the oxygen stream are preheated and mixed, and then enter the reactor together to undergo oxidative dehydrogenation reaction. If there are two or more reactors, the mixed stream is mixed with the added oxygen at the outlet of the preceding reactor and enters the subsequent reactor to continue the oxidative dehydrogenation reaction to obtain the final reaction process product gas a;

[0026] 2) The final reaction product gas a described in step 1) is subjected to rapid cooling treatment to remove acetic acid and water, and obtain a process product gas b from which acid water is removed. The acetic acid therein is recovered or subjected to acid water treatment. The rapid cooling treatment, removal of acetic acid and water, recovery of acetic acid or acid water treatment can be carried out by any conventional technology in the art;

[0027] 3) removing oxygen from the process product gas b in step 2) to obtain a process product gas c. The oxygen removal process may be carried out using any conventional technology 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 a carbon dioxide removal treatment to obtain a process product gas d. The carbon dioxide removal treatment can be carried out by any conventional technology in the art, including but not limited to washing with an organic amine first and then washing with an alkali;

[0029] 5) drying, multi-stage compression and cryogenic treatment of the process product gas d described in step 4) to obtain the process product gas e. The drying, multi-stage compression and cryogenic treatment can adopt any conventional technology in the art;

[0030] 6) The process product gas e in step 5) is subjected to ethane removal treatment to obtain process product gas f at the top of the tower and ethane at the bottom of the tower. The so-called ethane removal treatment can be carried out by any conventional technology in the art.

[0031] 7) The ethane described in step 6) is returned to the ethane preheater of 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 treatment to obtain tail gas at the top of the tower and ethylene product at the bottom of the tower. The ethylene distillation treatment can be carried out using any conventional technology in the art.

[0033] 9) treating the tail gas in step 8). The tail gas treatment may be carried out by any conventional technique in the art, including but not limited to flare treatment.

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

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

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

[0037] Based on the above technical solution, further, when the number of reactors is 2 or more, the ethane single-pass conversion rate and the acetic acid product content will be significantly increased.

[0038] Based on the above technical scheme, further, after step 2) acetic acid is recovered, 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 meets the national standard for industrial ethylene (GB / T 7715-2014).

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

[0041] A preheater for preheating oxygen logistics and ethane logistics, comprising an oxygen preheater (801-1) and an ethane preheater (801-2);

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

[0043] Used for hot mixed feedstock flow to pass through a reactor (803-1) filled with ethane oxidative dehydrogenation catalyst, and a subsequent possible reactor (803-i), where i is 2-4, and 2, 3 and 4 are preferred;

[0044] An acid water removal unit (804) for removing acid water from the process product gas stream a, such as an acid water 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 drying, multi-stage compression and cryogenic treatment equipment;

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

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

[0050] In general, the characteristics and advantages of the present invention are as follows:

[0051] a) By using the method and system provided by the present invention, no nitrogen or water is used as a diluent in the raw material; oxygen in any reactor is nearly completely converted, 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 reactors can be connected in series in multiple stages, which means that the ethane single-pass conversion level and product selectivity of the device 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) By using the method and system provided by the present invention, the ethane oxidation reaction can be operated highly stably on the catalyst.

[0054] d) The method and system provided by the present invention have particularly high product selectivity, especially high ethylene selectivity, and low raw material consumption.

[0055] e) The method and system provided by the present invention have a short production route, a simple product composition, low production energy consumption, and low carbon (mainly carbon monoxide and carbon dioxide) emissions. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0057] Figure 1 Explanation of logistics numbers: a represents the output after the last reactor; b represents the process gas flow after the acid water is removed from a; c represents the mixed flow after b passes through the oxygen removal device; d represents the gas phase mixture after c is treated by the deacidification device, including ethane, ethylene, and carbon monoxide; e represents the mixed flow after d passes through the drying, multi-stage compression and cryogenic treatment equipment; f represents the mixed flow distilled from the top of the tower, including ethylene and carbon monoxide; tail gas represents carbon monoxide distilled from the top of the tower. For other logistics, please refer to the text description of the attached figure.

[0058] Figure 1 Explanation of equipment numbers: 801-1 represents an oxygen preheater; 801-2 represents an ethane preheater; 802-1 represents 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 fixed bed reactor that may exist; 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.

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

[0060] Figure 2 Explanation of logistics numbers: a represents the output 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 stream after the acid water is removed from a; c represents the mixed stream after b passes through the oxygen removal device; d represents the gas phase mixture after c is treated by the deacidification device, including ethane, ethylene and carbon monoxide; e represents the mixed stream after d passes through the drying, multi-stage compression and cryogenic treatment equipment; f represents the mixed stream distilled from the top of the tower, including ethylene and carbon monoxide; tail gas represents the carbon monoxide distilled from the top of the tower. For other logistics, please refer to the text description of the attached figure.

[0061] Figure 2 Explanation of equipment numbers: 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 The present invention is a schematic diagram of the system structure of a non-dilution process of two reactors in series for catalytic oxidative dehydrogenation of ethane to produce ethylene.

[0063] Figure 3 Explanation of logistics numbers: a represents the product gas after the second reactor; b represents the process gas flow after the acid water is removed from a; c represents the mixed flow after b passes through the oxygen removal device; d represents the gas phase mixture after c is treated by the deacidification device, including ethane, ethylene, and carbon monoxide; e represents the mixed flow after d passes through the drying, multi-stage compression and cryogenic treatment equipment; f represents the mixed flow distilled from the top of the tower, including ethylene and carbon monoxide; tail gas represents carbon monoxide distilled from the top of the tower. For other logistics, please refer to the text description of the attached figure.

[0064] Figure 3 Explanation of equipment numbers: 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 connected to the acid water removal unit; 803-1 represents the first fixed bed reactor, 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; 809 represents the ethylene distillation tower. DETAILED DESCRIPTION

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

[0066] In the description of the present invention, pressure is a commonly used term, and its real meaning is "pressure intensity", which indicates absolute pressure (absolute pressure).

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

[0068] In the following embodiments, unless otherwise specified, the devices, equipment or processing technologies used are all commonly used devices or commonly used technologies in the art.

[0069] In the description of the present invention, it is necessary to further explain that the structures, proportions and sizes shown in the drawings of the present specification are all expressed in a concise manner, and are only used to match the contents disclosed in the specification so that people familiar with the technology can understand and read them, but are not used to limit the limiting conditions that the present invention can be implemented, so they have no technical substantive significance. Any structural modification, proportional relationship change or size adjustment, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope of the technical content disclosed by the present invention. The terms used in the present invention to indicate the orientation or position relationship, such as "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., refer to the orientation or position relationship based on the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to describe the order of the equipment before and after, and cannot be understood as indicating or implying their relative importance.

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

[0071] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, or a detachable connection, or an integral connection, or a mechanical connection, or an electrical connection, or a direct connection, or an indirect connection through an intermediate medium, or the internal connection of two elements, or a combination of any of the above connections. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0072] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0073] The following is a detailed description of the multi-stage series non-dilution process method and system for 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 21.6t / h and recycled ethane with a flow rate of 75.6t / h are mixed and preheated, and oxygen with a flow rate of 11.5t / h is preheated and fully mixed with ethane and then enters the fixed bed reactor together for oxidative dehydrogenation reaction, and the fixed bed is a shell-and-tube fixed bed reactor. The shell-and-tube fixed bed reactor is divided into a hot side and a cold side, and a mixed gas composed of ethane and oxygen enters the hot side of the shell-and-tube fixed bed reactor, and the hot side is filled with an annular catalyst, and its active component is MoVTeNbO described in patent CN2014101988672; the circulating molten salt is sent to the cold side of the shell-and-tube fixed bed reactor, and after absorbing the heat released by the oxidative dehydrogenation reaction, it is cooled by a heat exchanger as a circulating molten salt and circulated back to the cold side of the shell-and-tube fixed bed reactor. The molten salt can be selected from any molten salt system known to those skilled in the art, preferably potassium and sodium nitrates and nitrites. Ethane and oxygen react in the reactor to produce ethylene, acetic acid, carbon monoxide, carbon dioxide and water. The reactor discharge also contains unconverted ethane and trace oxygen, including 15.3 t / h of ethylene flow, 80.0 t / h of ethane flow, 1.3 t / h of oxygen, 1.2 t / h of acetic acid, 0.2 t / h of CO, 0.2 t / h of CO2 and 10.5 t / h of water. The reactor inlet feed temperature is 190 ° C, and the molten salt operating temperature is 310 ° C.

[0076] After the heat of the reactor discharge a is recovered, it passes through the acid water removal unit, the CO2 absorption unit, and the subsequent cooling and drying, multi-stage compression, and then enters the ethane separation and circulation unit and the final ethylene distillation unit. The above separation process belongs to the conventional technology in this field. Finally, a glacial acetic acid product with a purity of 99.5% (national standard for industrial glacial acetic acid) can be obtained. <gb t1628-2020>) and 99.7% purity polymer grade ethylene products containing very small amounts of ethane (National Standard for Industrial Ethylene<GB / T 7715-2014> ).

[0077] After the process described in this embodiment, the oxygen conversion rate is 98.5%, the ethylene selectivity is 95.5%, the ethylene space-time yield is 1.6 kg ethylene / kg catalyst / hour; the comprehensive energy consumption is 156 kg standard oil tons of ethylene, and the unit consumption of ethane raw material is 1.12 kg ethane / kg ethylene.

[0078] Example 2

[0079] like Figure 3 As shown, fresh ethane with a flow rate of 21.6t / h and recycled ethane with a flow rate of 75.6t / h are mixed and preheated, and oxygen with a flow rate of 11.5t / h is preheated and fully mixed with ethane and then enters the fixed bed reactor together for oxidative dehydrogenation reaction, and the fixed bed is a shell-and-tube fixed bed reactor. The shell-and-tube fixed bed reactor is divided into a hot side and a cold side, and a mixed gas composed of ethane and oxygen enters the hot side of the shell-and-tube fixed bed reactor, and the hot side is filled with an annular catalyst, and its active component is MoVTeNbO described in patent CN2014101988672; the circulating molten salt is sent to the cold side of the shell-and-tube fixed bed reactor, and after absorbing the heat released by the oxidative dehydrogenation reaction, it is cooled by a heat exchanger as a circulating molten salt and circulated back to the cold side of the shell-and-tube fixed bed reactor. The molten salt can be selected from any molten salt system known to those skilled in the art, preferably potassium and sodium nitrates and nitrites. Ethane and oxygen react in the reactor to produce ethylene, acetic acid, carbon monoxide, carbon dioxide and water, and the reactor discharge also contains unconverted ethane and trace oxygen. The inlet feed temperature of the first reactor is 190°C, and the molten salt operating temperature is 310°C. The above reactor discharge is preheated and fully mixed with the added oxygen at a flow rate of 11.5t / h, and then enters the hot side of the second tubular bed fixed bed reactor, which is filled with an annular catalyst, and its active component is MoVTeNbO described in patent CN201410198867. The second reactor has 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 flow passing through the second tubular bed fixed bed reactor includes ethylene, acetic acid, carbon monoxide, carbon dioxide and water. The reactor output also contains unconverted ethane and trace oxygen. The ethylene flow rate is 28.0 t / h, the ethane flow rate is 64.7 t / h, the oxygen flow rate is 2.2 t / h, the acetic acid flow rate is 3.8 t / h, CO is 0.7 t / h, CO2 is 0.7 t / h and water is 20.2 t / h.

[0080] After the heat of the reactor discharge a is recovered, it passes through the acid water removal unit, the CO2 absorption unit, and the subsequent cooling and drying, multi-stage compression, and then enters the ethane separation and circulation unit and the final ethylene distillation unit. The above separation process belongs to the conventional technology in this field. Finally, a glacial acetic acid product with a purity of 99.8% (industrial glacial acetic acid national standard <gb t1628-2020>) and polymerization-grade ethylene products with a purity of 99.9% and containing very small amounts of ethane, which comply with 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 yield is 1.2 kg ethylene / kg catalyst / hour; the comprehensive energy consumption is 110 kg standard oil / ton ethylene, and the unit consumption of ethane raw material is 1.16 kg ethane / kg ethylene.

[0082] Example 3

[0083] like Figure 2 As shown, fresh ethane with a flow rate of 22.7t / h and recycled ethane with a flow rate of 62.3t / h are mixed and preheated, and oxygen with a flow rate of 16.5t / h is preheated and fully mixed with ethane and then enters the fixed bed reactor together for oxidative dehydrogenation reaction, and the fixed bed is a shell-and-tube fixed bed reactor. The shell-and-tube fixed bed reactor is divided into a hot side and a cold side, and a mixed gas composed of ethane and oxygen enters the hot side of the shell-and-tube fixed bed reactor, and the hot side is filled with an annular catalyst, and its active component is MoVTeNbO described in patent CN2014101988672; the circulating molten salt is sent to the cold side of the shell-and-tube fixed bed reactor, and after absorbing the heat released by the oxidative dehydrogenation reaction, it is cooled by a heat exchanger as a circulating molten salt and circulated back to the cold side of the shell-and-tube fixed bed reactor. The molten salt can be selected from any molten salt system known to those skilled in the art, preferably potassium and sodium nitrates and nitrites. Ethane and oxygen react in the reactor to produce ethylene, acetic acid, carbon monoxide, carbon dioxide, water and methane, and the reactor discharge also contains unconverted ethane and trace oxygen. The reactor inlet feed temperature is 190°C, and the molten salt operating temperature is 310°C. The mixed product flow passing through the tubular bed fixed bed reactor includes ethylene, acetic acid, carbon monoxide, carbon dioxide, water, and the reactor discharge also contains unconverted ethane and oxygen. The ethylene flow rate is 20.2t / h, the ethane flow rate is 62.3t / h, the oxygen flow rate is 2.91t / h, the acetic acid flow rate is 1.6t / h, the CO flow rate is 0.30t / h, the CO2 flow rate is 0.27t / h and the water flow rate is 13.9t / h.

[0084] After the heat of the reactor discharge a is recovered, it passes through the acid water removal unit, oxygen removal unit, CO2 absorption unit, and subsequent cooling and drying, multi-stage compression, and then enters the ethane separation and circulation unit, ethylene distillation unit, and finally methane removal and circulation. The above separation process belongs to the conventional technology in this field. Finally, a glacial acetic acid product with a purity of 99.8% (industrial glacial acetic acid national standard <gb t1628-2020>) and polymerization-grade ethylene products with a purity of 99.9% and containing very small amounts of ethane, which comply with 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 yield is 1.3 kg ethylene / kg catalyst / hour, the comprehensive energy consumption is 90 kg standard oil / ton ethylene, and the unit consumption of ethane raw material 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 present invention. Anyone familiar with the art may 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be included in the claims of the present invention.< / gb> < / gb> < / gb>

Claims

1. A multi-stage series reaction process for preparing ethylene and acetic acid by catalytic oxidative dehydrogenation of ethane without diluent, characterized in that: The raw gas of the process method does not contain a diluent and the oxidant is oxygen.

2. The process according to claim 1, characterized in that: The reactor in the process method is a fixed bed reactor. If the number of reactors is 2 or more, the reactors are connected in series, and oxygen needs to be added before each reactor.

3. The process according to claim 1, characterized in that: The process comprises the following steps: 1) The ethane stream and the oxygen stream are preheated and mixed respectively, and then enter the reactor together to undergo oxidative dehydrogenation reaction to obtain the process product gas a of the final reaction; if there are two or more reactors, the mixed stream is mixed with the added oxygen at the outlet of the preceding reactor to obtain a mixed stream, and enters the subsequent reactor to continue the oxidative dehydrogenation reaction to obtain the process product gas a of the final reaction; 2) subjecting the final reaction product gas a described in step 1) to rapid cooling treatment to remove acetic acid and water, and obtaining a process product gas b from which acid water is removed, wherein the acetic acid is recovered or subjected to acid water treatment; 3) deoxygenating the process product gas b described in step 2) to obtain a process product gas c; 4) removing carbon dioxide from the process product gas c described in step 3) to obtain a process product gas d; 5) drying, multi-stage compressing and cryogenically treating the process product gas d described in step 4) to obtain the process product gas e; 6) removing ethane from the process product gas e in step 5) to obtain a process product gas f at the top of the tower and ethane at the bottom of the tower; 7) returning the ethane described in step 6) to the ethane preheater of step 1) for preheating and continuing the oxidative dehydrogenation reaction as a raw material; 8) subjecting the process product gas f described in step 6) to ethylene distillation to obtain tail gas at the top of the tower and ethylene product at the bottom of the tower; 9) treating the tail gas in step 8).

4. The process according to claim 1 or 3, characterized in that: In step 1), the mixed raw material entering the first reactor does not need to contain any diluent.

5. The process according to claim 1, 2 or 3, characterized in that: The catalytic reaction of ethane oxidative dehydrogenation to ethylene is carried out in a multi-stage series reactor, and the multi-stage series reactor includes a special case of only one fixed bed reactor. The reactor is a fixed bed reactor, preferably a shell-and-tube fixed bed reactor.

6. The process according to claim 1, 2 or 3, characterized in that: The mass ratio of oxygen to the total amount of flammable and explosive substances at the reactor inlet is 0.01 to 0.55:1, and the flammable and explosive substances include ethane, ethylene, carbon monoxide and acetic acid; the inlet temperature of any fixed bed reactor is 100°C to 400°C, preferably 150°C-300°C; the inlet pressure of any fixed bed reactor is 0.10 to 1.0 MPa, preferably 0.20-0.70 MPa.

7. The process according to claim 1, 2 or 5, characterized in that: When there are two or more reactors, the ethane single-pass conversion rate and the acetic acid product content will increase significantly.

8. The process according to claim 3, characterized in that: In step 2), the deoxidation treatment includes catalytic oxidation technology; In step 4), the carbon dioxide removal treatment includes first washing with an organic amine and then washing with an alkali; In step 9), the waste gas treatment includes flare treatment.

9. The process according to claim 3, characterized in that: After the acetic acid is recovered in step 2), the acetic acid product meets the national standard for industrial glacial acetic acid (GB / T 1628-2020); After the ethylene distillation treatment in step 7), the ethylene product meets the national standard for industrial ethylene (GB / T 7715-2014).

10. A system for a multi-stage series reaction of ethane catalytic oxidative dehydrogenation to produce ethylene and acetic acid without diluent used in the process method according to any one of claims 1 to 9, characterized in that: Mainly include: Preheaters (801-1 and 801-2) for preheating oxygen and ethane streams; For hot mixing the raw material flow through the reactor (803-1) filled with ethane oxidative dehydrogenation catalyst, and the subsequent possible reactor (803-i), wherein i is 2-4; A quenching unit (802) and an acid water removal unit (804) for quenching the process product gas stream a and removing acid water; An oxygen removal unit (805) for removing oxygen from the process product gas stream b; A unit (806) for removing CO2 from the process gas product stream c; A unit (807) for drying, multi-stage compression and cryogenic treatment of the process gas product stream d; A unit (808) for removing ethane from the process gas product stream e; and a unit (809) for performing ethylene distillation treatment on the process gas product stream f.

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