System and process for preparing synthesis gas by reacting carbon dioxide and hydrogen

Abstract

This invention provides a system and process for producing syngas from carbon dioxide and hydrogen. The system includes n-stage reverse vapor shift (RPS) units connected in series, where n ≥ 3, used to sequentially perform n-stage RPS reactions on feed CO2 and H2 to obtain syngas. The process utilizes the aforementioned system to perform an n-stage RPS reaction on carbon dioxide and hydrogen to obtain syngas. The catalyst used in the n-stage RPS reaction is a Cr2O3 / MgAl2O4-TiO2 catalyst; the Cr2O3 / MgAl2O4-TiO2 catalyst is a catalyst formed by supporting Cr2O3 on a TiO2-modified MgAl2O4 spinel support. This system eliminates the need for circulation pipelines, decarbonization devices, and hydrogen separation devices; this system and process can achieve efficient and large-scale conversion of CO2 and H2 into syngas, meeting the needs of subsequent synthesis of high-value-added chemicals and oil products; the reaction temperature is low.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide conversion to syngas, specifically relating to a system and process for the reaction of carbon dioxide and hydrogen to produce syngas. Background Technology

[0002] my country has a massive coal-fired power, coal chemical, and steel industry cluster, resulting in enormous carbon dioxide emissions. To address current carbon emission processes, carbon reduction can be considered from two aspects: first, source reduction through improving existing technologies for energy conservation and emission reduction; and second, end-of-life carbon reduction by capturing and utilizing emitted CO2, i.e., CCUS technology. Therefore, the resource utilization of carbon dioxide is one of the effective ways to reduce carbon emissions. Reverse water vapor shift (RWGS) technology can convert CO2 into valuable CO, which can then be combined with H2 to synthesize oils or chemicals, representing a feasible approach to CO2 resource utilization.

[0003] Compared to electrochemical, photochemical, and biochemical conversion technologies, thermochemistry is the most efficient large-scale CO2 conversion technology. CO2 is the most stable end product of carbon combustion, and direct activation is difficult. Economic viability is key to CO2 conversion and utilization, and increasing the added value of products is crucial for the resource utilization of CO2. Theoretically, CO2 can react with H2 to produce chemicals and petroleum products, but technically it is very difficult to achieve, and even if it is achieved, its economic viability is hard to guarantee. C1 chemistry's main products include methanol, ethanol, ethylene glycol, petroleum products, olefins, and waxes. Among these, olefins and waxes have the highest added value. Although there is research in academia on the direct synthesis of CO2 and H2, the efficiency is very low and cannot meet industrial needs. Currently, industry can only produce chemicals and petroleum products through the syngas route of CO plus H2.

[0004] Current technology cannot efficiently react CO2 and H2 to synthesize chemicals or oils, nor can it efficiently react CO2 and H2 to generate syngas that can be directly used to prepare chemicals, not to mention its economic viability. Summary of the Invention

[0005] The first objective of this invention is to provide a system for the reaction of carbon dioxide and hydrogen to produce syngas, which can be used directly for the preparation of chemicals or petroleum products.

[0006] A second objective of this invention is to provide a process for the reaction of carbon dioxide and hydrogen to produce syngas, which enables the reaction of carbon dioxide and hydrogen to produce syngas, and the syngas produced can be directly used in the preparation of chemicals or petroleum products.

[0007] A third objective of this invention is to provide a synthesis gas prepared using the aforementioned process.

[0008] A fourth objective of this invention is to provide an application of the syngas prepared using the aforementioned process in the preparation of chemicals or petroleum products.

[0009] To achieve the first objective of this invention, a system for producing syngas from carbon dioxide and hydrogen is provided. The system includes n-stage reverse vapor shift units (RPF) arranged in series, where n ≥ 3, for sequentially performing n-stage RPF reactions on feed CO2 and H2 to obtain syngas.

[0010] The catalyst used in the n-stage reverse water-gas shift reaction is a Cr2O3 / MgAl2O4-TiO2 catalyst; the Cr2O3 / MgAl2O4-TiO2 catalyst is a catalyst formed by supporting Cr2O3 on a TiO2-modified MgAl2O4 spinel support;

[0011] The n-stage reverse water vapor conversion unit includes a first reverse water vapor conversion unit, a second reverse water vapor conversion unit, and a third reverse water vapor conversion unit;

[0012] The first reverse steam shift unit includes a first reverse steam shift reactor and a first dehydration device connected in sequence. The feed inlet of the first reverse steam shift reactor is provided with a CO2 inlet pipeline and an H2 inlet pipeline, which are used to introduce CO2 and H2 respectively to carry out a first-stage reverse steam shift reaction, and output a first syngas including CO, H2, CH4, water vapor and CO2. The feed inlet of the first dehydration device is connected to the discharge outlet of the first reverse steam shift reactor, and is used to dehydrate the first syngas from the first reverse steam shift reactor, and output a first dehydrated syngas.

[0013] The second reverse vapor shift unit includes a second reverse vapor shift reactor and a second dehydration device connected in sequence. The inlet of the second reverse vapor shift reactor is connected to the outlet of the first dehydration device for introducing first dehydrated syngas from the first dehydration device to perform a second-stage reverse vapor shift reaction using CO2 and H2 therein, and outputting second syngas including CO, H2, CH4, water vapor and CO2. The inlet of the second dehydration device is connected to the outlet of the second reverse vapor shift reactor for dehydrating the second syngas from the second reverse vapor shift reactor and outputting second dehydrated syngas.

[0014] The third reverse steam shift unit includes a third reverse steam shift reactor and a third dehydration device connected in sequence. The feed inlet of the third reverse steam shift reactor is connected to the discharge outlet of the second dehydration device, and is used to introduce the second dehydrated syngas from the second dehydration device to perform a three-stage reverse steam shift reaction using CO2 and H2 therein, and output a third syngas including CO, H2, CH4, water vapor and CO2. The feed inlet of the third dehydration device is connected to the discharge outlet of the third reverse steam shift reactor, and is used to dehydrate the third syngas from the third reverse steam shift reactor, and output a third dehydrated syngas.

[0015] Preferably, the first reverse steam-water shift unit further includes a first heat exchanger, the inlet of which is connected to the outlet of the CO2 inlet pipeline and the outlet of the H2 inlet pipeline, respectively, and the outlet of which is connected to the inlet of the first reverse steam-water shift reactor, for preheating the CO2 and H2 to be entering the first reverse steam-water shift reactor; and / or

[0016] The second reverse steam shift unit further includes a second heat exchanger, the inlet of which is connected to the outlet of the first dehydration device, and the outlet of which is connected to the inlet of the second reverse steam shift reactor, for preheating the first dehydrated syngas to be entered into the second reverse steam shift reactor; and / or

[0017] The third reverse water-gas shift unit also includes a third heat exchanger. The inlet of the third heat exchanger is connected to the outlet of the second dehydration device, and the outlet of the third heat exchanger is connected to the inlet of the third reverse water-gas shift reactor. It is used to preheat the second dehydrated syngas to be entered into the third reverse water-gas shift reactor.

[0018] Preferably, the first reverse steam shift reactor is a tubular reactor; and / or the first dehydration device is a gas-liquid separator; and / or

[0019] The second reverse steam shift reactor is a tubular reactor; and / or the second dehydration device is a gas-liquid separator; and / or

[0020] The third reverse steam shift reactor is a tubular reactor; and / or the third dehydration device is a gas-liquid separator.

[0021] To achieve the second objective of this invention, a process for preparing syngas by reacting carbon dioxide and hydrogen is provided, wherein the aforementioned system is used to perform an n-stage reverse water-gas shift reaction of carbon dioxide and hydrogen to obtain syngas; wherein n≥3;

[0022] The catalyst used in the n-stage reverse water-gas shift reaction is a Cr2O3 / MgAl2O4-TiO2 catalyst;

[0023] The Cr2O3 / MgAl2O4-TiO2 catalyst is a catalyst formed by supporting Cr2O3 on a TiO2-modified MgAl2O4 spinel support.

[0024] Preferably, the Cr2O3 content in the Cr2O3 / MgAl2O4-TiO2 catalyst is 2-8 wt%.

[0025] Preferably, the TiO2 content in the Cr2O3 / MgAl2O4-TiO2 catalyst is 5-16 wt%.

[0026] Preferably, in the Cr2O3 / MgAl2O4-TiO2 catalyst, the content of MgO is 20-30 wt% and the content of Al2O3 is 50-70 wt%.

[0027] Preferably, the reaction conditions for the nth-stage reverse water-steam shift reaction include:

[0028] The reaction pressure is 1.0-5.0 MPa, the reaction temperature is 450-550℃, and the space velocity is 5000-15000 h⁻¹. -1 .

[0029] Preferably, the composition of the raw gas includes a volume ratio of H2 to CO2 of 3-4.

[0030] Preferably, the process includes the following steps:

[0031] (1) CO2 and H2 are respectively fed to the first reverse water-gas shift reactor to carry out a first-stage reverse water-gas shift reaction, and the output is a first synthesis gas including CO, H2, CH4, water vapor and CO2;

[0032] (2) The first syngas obtained in step (1) is transported to the first dehydration device for dehydration, and the first dehydrated syngas is output;

[0033] (3) The first dehydrated syngas obtained in step (2) is transported to the second reverse water-gas shift reactor to carry out a second-stage reverse water-gas shift reaction, and the output is a second syngas including CO, H2, CH4, water vapor and CO2;

[0034] (4) The second syngas obtained in step (3) is transported to the second dehydration device for dehydration, and the second dehydrated syngas is output;

[0035] (5) The second dehydrated syngas obtained in step (4) is transported to the third reverse water-gas shift reactor to carry out a three-stage reverse water-gas shift reaction, and the output is a third syngas including CO, H2, CH4, water vapor and CO2;

[0036] (6) The third syngas obtained in step (5) is transported to the third dehydration device for dehydration, and the third dehydrated syngas is output;

[0037] Preferably, in step (1), before CO2 and H2 are conveyed to the first reverse water-gas shift reactor, they are first conveyed to the first heat exchanger for preheating; preferably, the preheating temperature is 200-400°C; and / or

[0038] In step (3), before the first dehydrated syngas obtained in step (2) is conveyed to the second reverse steam shift reactor, it is first conveyed to the second heat exchanger for preheating; preferably preheated to 200-400°C; and / or

[0039] In step (5), before the second dehydrated syngas obtained in step (4) is transported to the third reverse water-gas shift reactor, it is first transported to the third heat exchanger for preheating; preferably, it is preheated to 200-400℃.

[0040] To achieve a third objective of the present invention, a synthesis gas prepared according to the aforementioned process is also provided, wherein the synthesis gas has a CO2 content ≤ 5v%, a (H2-CO2) / (CO+CO2) modulus of 2.1-2.5, and a CH4 content ≤ 1v.

[0041] To achieve the fourth objective of this invention, an application of the syngas obtained according to the aforementioned process in the preparation of chemicals or petroleum products is also provided.

[0042] The beneficial effects of this invention are as follows:

[0043] The system and process for preparing syngas by reacting carbon dioxide and hydrogen according to the present invention can be used to prepare syngas by reacting carbon dioxide and hydrogen, and the conversion rate of CO2 is high, the quality of the syngas produced is good, wherein the CO2 content is ≤5v%, the (H2-CO2) / (CO+CO2) modulus is 2.1-2.5, and the CH4 content is ≤1v%, and it can be directly used for the preparation of chemicals or oils;

[0044] Furthermore, it can efficiently and on a large scale convert CO2 and H2 into syngas, meeting the needs of subsequent synthesis of high-value-added chemicals and oil products;

[0045] The reaction temperature is low; for a strongly endothermic reaction like the reverse water-gas shift reaction, a reaction temperature of 450-550℃ can be achieved.

[0046] The methanation side reaction on the wall can be suppressed using a standard 304 stainless steel reactor, eliminating the need for a reactor made of special materials. Attached Figure Description

[0047] Figure 1This is a schematic diagram of the system for preparing syngas by reacting carbon dioxide and hydrogen in one embodiment of the present invention;

[0048] Figure 2 This is a schematic diagram of the system for producing syngas by reacting carbon dioxide and hydrogen in another embodiment of the present invention. Detailed Implementation

[0049] The technical solution and its effects of the present invention will be further described below with reference to specific embodiments / examples. The following embodiments / examples are only for illustrating the content of the present invention, and the invention is not limited to the following embodiments or examples. Simple modifications made to the present invention based on the concept of the present invention are all within the scope of protection claimed by the present invention.

[0050] This invention provides a system for the reaction of carbon dioxide and hydrogen to produce syngas, such as... Figure 1 , 2 As shown, the system includes n-stage reverse vapor shift units arranged in series, where n ≥ 3, used to sequentially perform n-stage reverse vapor shift reactions on feed CO2 and H2 to obtain syngas; wherein,

[0051] The catalyst used in the n-stage reverse water-gas shift reaction is a Cr2O3 / MgAl2O4-TiO2 catalyst; the Cr2O3 / MgAl2O4-TiO2 catalyst is a catalyst formed by supporting Cr2O3 on a TiO2-modified MgAl2O4 spinel support;

[0052] The n-stage reverse water vapor conversion unit includes a first reverse water vapor conversion unit, a second reverse water vapor conversion unit, and a third reverse water vapor conversion unit;

[0053] The first reverse steam shift unit includes a first reverse steam shift reactor 1 and a first dehydration device 2 connected in sequence. The feed inlet of the first reverse steam shift reactor 1 is provided with a CO2 inlet pipeline 3 and an H2 inlet pipeline 4, which are used to introduce CO2 and H2 respectively to carry out a first-stage reverse steam shift reaction, and output a first synthesis gas including CO, H2, CH4, water vapor and CO2. The feed inlet of the first dehydration device 2 is connected to the discharge outlet of the first reverse steam shift reactor 1, and is used to dehydrate the first synthesis gas from the first reverse steam shift reactor 1, and output a first dehydrated synthesis gas.

[0054] The second reverse vapor shift unit includes a second reverse vapor shift reactor 5 and a second dehydration device 6 connected in sequence. The inlet of the second reverse vapor shift reactor 5 is connected to the outlet of the first dehydration device 2, for introducing the first dehydrated syngas from the first dehydration device 2 to perform a second-stage reverse vapor shift reaction using CO2 and H2 therein, and outputting a second syngas including CO, H2, CH4, water vapor and CO2. The inlet of the second dehydration device 6 is connected to the outlet of the second reverse vapor shift reactor 5, for dehydrating the second syngas from the second reverse vapor shift reactor 5, and outputting a second dehydrated syngas.

[0055] The third reverse steam shift unit includes a third reverse steam shift reactor 7 and a third dehydration device 8 connected in sequence. The inlet of the third reverse steam shift reactor 7 is connected to the outlet of the second dehydration device 6, and is used to introduce the second dehydrated syngas from the second dehydration device 6 to perform a three-stage reverse steam shift reaction using CO2 and H2 therein, and output a third syngas including CO, H2, CH4, water vapor and CO2. The inlet of the third dehydration device 8 is connected to the outlet of the third reverse steam shift reactor 7, and is used to dehydrate the third syngas from the third reverse steam shift reactor 7, and output a third dehydrated syngas.

[0056] Those skilled in the art will understand that the output third dehydrated syngas can be used as the product gas of this invention.

[0057] In this invention, "the catalyst used in the n-stage reverse water-gas shift reaction is a Cr2O3 / MgAl2O4-TiO2 catalyst" means that the catalyst used in each stage of the reverse water-gas shift reaction in the n-stage reverse water-gas shift reaction is a Cr2O3 / MgAl2O4-TiO2 catalyst.

[0058] Those skilled in the art will understand that, in order to further improve the quality of the product gas, the n-stage reverse water vapor conversion unit may further include a fourth reverse water vapor conversion unit.

[0059] The fourth reverse steam shift unit includes a fourth reverse steam shift reactor and a fourth dehydration device connected in sequence. The feed inlet of the fourth reverse steam shift reactor is connected to the discharge outlet of the third dehydration device 8, for introducing the second dehydrated syngas from the third dehydration device 8 to perform a four-stage reverse steam shift reaction using CO2 and H2 therein, and outputting a fourth syngas including CO, H2, CH4, water vapor and CO2. The feed inlet of the fourth dehydration device is connected to the discharge outlet of the fourth reverse steam shift reactor, for dehydrating the fourth syngas from the fourth reverse steam shift reactor, and outputting the fourth dehydrated syngas as product gas.

[0060] To further improve the quality of the product gas, an additional reverse water-gas conversion unit can be added.

[0061] The system for producing syngas from carbon dioxide and hydrogen according to the present invention eliminates the need for circulation pipelines, decarbonization devices, and hydrogen separation devices, and can produce syngas product gas that meets the requirements, enabling it to be directly used in the preparation of chemicals or oils.

[0062] In one embodiment, the first reverse steam shift unit further includes a first heat exchanger 9, the inlet of which is connected to the outlet of the CO2 inlet pipeline 3 and the H2 inlet pipeline 4, respectively, and the outlet of which is connected to the inlet of the first reverse steam shift reactor 1, for preheating the CO2 and H2 to be entering the first reverse steam shift reactor 1; and / or

[0063] The second reverse steam shift unit further includes a second heat exchanger 10, the inlet of which is connected to the outlet of the first dehydration device 2, and the outlet of which is connected to the inlet of the second reverse steam shift reactor 5, for preheating the first dehydrated syngas to be entered into the second reverse steam shift reactor 5; and / or

[0064] The third reverse water-gas shift unit also includes a third heat exchanger 11. The inlet of the third heat exchanger 11 is connected to the outlet of the second dehydration device 6, and the outlet of the third heat exchanger 11 is connected to the inlet of the third reverse water-gas shift reactor 7, for preheating the second dehydrated syngas to be entered into the third reverse water-gas shift reactor 7.

[0065] Those skilled in the art will understand that if a fourth reverse steam shift unit is provided, a fourth heat exchanger can also be provided at the feed inlet of the fourth reverse steam shift reactor to preheat the third dehydrated syngas to be entered into the fourth reverse steam shift reactor. And so on.

[0066] In one embodiment, the first reverse steam shift reactor 1 is a tubular reactor; and / or the first dehydration device 2 is a gas-liquid separator; and / or

[0067] The second reverse steam shift reactor 5 is a tubular reactor; and / or the second dehydration device 6 is a gas-liquid separator; and / or

[0068] The third reverse water-gas shift reactor 7 is a tubular reactor; and / or the third dehydration device 8 is a gas-liquid separator.

[0069] Those skilled in the art will understand that if a fourth reverse steam shift unit is provided, the fourth reverse steam shift reactor is a tubular reactor; and / or the fourth dehydration device is a gas-liquid separator. And so on.

[0070] The present invention also provides a process for preparing syngas by reacting carbon dioxide and hydrogen, wherein the aforementioned system is used to perform a reverse water-gas shift reaction on carbon dioxide and hydrogen to obtain syngas; wherein, n≥3;

[0071] The catalyst used in the n-stage reverse water-gas shift reaction is a Cr2O3 / MgAl2O4-TiO2 catalyst;

[0072] The Cr2O3 / MgAl2O4-TiO2 catalyst is a catalyst formed by supporting Cr2O3 on a TiO2-modified MgAl2O4 spinel support.

[0073] Those skilled in the art will understand that the term "modification" refers to doping, and "TiO2-modified MgAl2O4 spinel support" means a MgAl2O4 spinel support doped with TiO2.

[0074] In this invention, "the catalyst used in the n-stage reverse water-gas shift reaction is a Cr2O3 / MgAl2O4-TiO2 catalyst" means that the catalyst used in each stage of the reverse water-gas shift reaction in the n-stage reverse water-gas shift reaction is a Cr2O3 / MgAl2O4-TiO2 catalyst.

[0075] Those skilled in the art will understand that the reverse water-vapor shift reaction is an endothermic reaction, and the heat supply in this invention is provided by burning flammable gases such as CH4 or chemical synthesis purge gases.

[0076] The process for preparing syngas by reacting carbon dioxide and hydrogen according to the present invention can produce high-quality syngas that meets the requirements in a single-pass conversion without the need for recycling, decarbonization and hydrogen separation steps.

[0077] In one embodiment, the Cr2O3 content in the Cr2O3 / MgAl2O4-TiO2 catalyst is 2-8 wt%, such as 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, and 7.5 wt%.

[0078] Preferably, in the Cr2O3 / MgAl2O4-TiO2 catalyst, the TiO2 content is 5-16 wt%, such as 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%, 10.5 wt%, 11 wt%, 11.5 wt%, 12 wt%, 12.5 wt%, 13 wt%, 13.5 wt%, 14 wt%, 14.5 wt%, 15 wt%, and 15.5 wt%.

[0079] Preferably, in the Cr2O3 / MgAl2O4-TiO2 catalyst, the MgO content is 20-30 wt%, such as 20.5 wt%, 21 wt%, 21.5 wt%, 22 wt%, 22.5 wt%, 23 wt%, 23.5 wt%, 24 wt%, 24.5 wt%, 25 wt%, 25.5 wt%, 26 wt%, 26.5 wt%, 27 wt%, 27.5 wt%, 28 wt%, 28.5 wt%, 29 wt%, and 29.5 wt%.

[0080] The Al2O3 content is 50-70 wt%, for example, 50.5 wt%, 51 wt%, 51.5 wt%, 52 wt%, 52.5 wt%, 53 wt%, 53.5 wt%, 54 wt%, 54.5 wt%, 55 wt%, 55.5 wt%, 56 wt%, 56.5 wt%, 57 wt%, 57.5 wt%, 58 wt%, 58.5 wt%, 59 wt%, and 59.5 wt%.

[0081] In one embodiment, the reaction conditions for the n-stage reverse water-gas shift reaction include:

[0082] The reaction pressure is 1.0-5.0 MPa, such as 1.5 MPa, 2.0 MPa, 2.5 MPa, 3.0 MPa, 3.5 MPa, 4.0 MPa and 4.5 MPa;

[0083] The reaction temperature is 450-550℃, such as 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃ and 540℃;

[0084] Airspeed is 5000-15000 h -1 For example, 6000h -1 7000h -1 8000h -1 9000h -1 10000 h -1 11000h -1 12000h-1 13000h -1 and 14000h -1 .

[0085] In this invention, "the reaction conditions of the n-stage reverse water-gas shift reaction" refers to the reaction conditions of each stage of the reverse water-gas shift reaction in the n-stage reverse water-gas shift reaction.

[0086] Those skilled in the art will understand that space velocity refers to the volumetric space velocity of the feed gas, which is expressed as the volume of feed gas per hour divided by the volume of the catalyst bed.

[0087] Reverse steam shift (CO2 + H2 = CO + H2O) technology can efficiently convert CO2 into CO, which can then be used to produce chemicals via the syngas route. CO2 shift technology can serve as an intermediate step in the conversion of CO2 into chemicals, acting as a bridge connecting CO2 to high-value-added chemicals. Currently, surplus hydrogen from processes such as propane dehydrogenation and coke oven gas can be used. With future technological advancements, the use of green hydrogen will become a reality, and the application of CO2 shift technology will have a broader prospect. Syngas produced from CO2 and H2 via CO2 shift reaction is the feedstock gas for downstream chemical synthesis, making economic efficiency particularly important. Furthermore, as an endothermic reaction, CO2 conversion in CO2 shift reaction generally requires high temperatures due to thermodynamic limitations. However, in this application, a high CO2 conversion rate can be achieved in the CO2 shift reaction at only 450-550℃, breaking conventional thinking and providing a new approach to achieving high CO2 conversion rates in CO2 shift reactions.

[0088] In conventional syngas production processes, the reactor walls catalyze methanation side reactions. Suppressing these side reactions typically requires reactors made of special materials. However, this invention, through the use of a catalyst, effectively suppresses methanation side reactions on the reactor walls even when using ordinary 304 stainless steel reactors.

[0089] In one embodiment, the composition of the feed gas includes a volume ratio of H2 to CO2 of 3-4, such as 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8 and 3.9.

[0090] In one embodiment, the process includes the following steps:

[0091] (1) CO2 and H2 are respectively fed to the first reverse water-gas shift reactor 1 to carry out a first-stage reverse water-gas shift reaction, and the output is a first synthesis gas including CO, H2, CH4, water vapor and CO2;

[0092] (2) The first syngas obtained in step (1) is transported to the first dehydration device 2 for dehydration, and the first dehydrated syngas is output.

[0093] (3) The first dehydrated syngas obtained in step (2) is transported to the second reverse water-gas shift reactor 5 for a second-stage reverse water-gas shift reaction, and the output is a second syngas including CO, H2, CH4, water vapor and CO2;

[0094] (4) The second syngas obtained in step (3) is transported to the second dehydration device 6 for dehydration, and the second dehydrated syngas is output;

[0095] (5) The second dehydrated syngas obtained in step (4) is transported to the third reverse water-gas shift reactor 7 for a three-stage reverse water-gas shift reaction, and the output is a third syngas including CO, H2, CH4, water vapor and CO2;

[0096] (6) The third syngas obtained in step (5) is transported to the third dehydration device 8 for dehydration and the third dehydrated syngas is output.

[0097] Those skilled in the art will understand that the process may further include the following steps:

[0098] (7) The third dehydrated syngas obtained in step (6) is transported to the fourth reverse water-gas shift reactor to carry out a four-stage reverse water-gas shift reaction, and the output is a fourth syngas including CO, H2, CH4, water vapor and CO2;

[0099] (8) The fourth syngas obtained in step (7) is transported to the fourth dehydration device for dehydration, and the fourth dehydrated syngas is output as the product gas. And so on.

[0100] In one embodiment, in step (1), CO2 and H2 are preheated in the first heat exchanger 9 before being fed to the first reverse steam shift reactor 1; preferably preheated to 200-400°C, such as 250°C, 300°C, and 350°C; and / or

[0101] In step (3), before the first dehydrated syngas obtained in step (2) is conveyed to the second reverse water-gas shift reactor 5, it is first conveyed to the second heat exchanger 10 for preheating; preferably preheated to 200-400℃, such as 250℃, 300℃ and 350℃; and / or

[0102] In step (5), before the second dehydrated syngas obtained in step (4) is transported to the third reverse water-gas shift reactor 7, it is first transported to the third heat exchanger 11 for preheating; preferably preheated to 200-400℃, such as 250℃, 300℃ and 350℃.

[0103] Those skilled in the art will understand that in step (7), before the third dehydrated syngas obtained in step (6) is transported to the fourth reverse water-gas shift reactor, it is first transported to the fourth heat exchanger for preheating; preferably, it is preheated to 200-400°C, such as 250°C, 300°C, and 350°C. And so on.

[0104] The present invention also provides a synthesis gas prepared according to the aforementioned process, wherein the synthesis gas has a CO2 content ≤ 5v%, a (H2-CO2) / (CO+CO2) modulus of 2.1-2.5, and a CH4 content ≤ 1v.

[0105] Those skilled in the art will understand that if the syngas has a high carbon dioxide content, it cannot be used in the preparation of other high-value-added chemicals. To use it in the preparation of high-value-added chemicals, further carbon removal (CO2 removal) and H2 separation are required, which is a complex and costly process. The syngas obtained by this invention requires no recycling, carbon removal, or H2 separation during preparation and before subsequent use, resulting in a simple process. It is low-cost and easily scalable for efficient large-scale synthesis.

[0106] The present invention also provides the application of the syngas obtained according to the aforementioned process in the preparation of chemicals or petroleum products.

[0107] The system and process for preparing syngas by reacting carbon dioxide and hydrogen according to the present invention can be used to prepare syngas by reacting carbon dioxide and hydrogen. The syngas produced is of good quality, wherein the CO2 content is ≤5v%, the (H2-CO2) / (CO+CO2) modulus is 2.1-2.5, and the CH4 content is ≤1v%. It can be directly used for the preparation of chemicals or oils.

[0108] Furthermore, it can efficiently and on a large scale convert CO2 and H2 into syngas, meeting the needs of subsequent synthesis of high-value-added chemicals and oil products;

[0109] The reaction temperature is low; for a strongly endothermic reaction like the reverse water-gas shift reaction, a reaction temperature of 450-550℃ can be achieved.

[0110] The methanation side reaction on the wall can be suppressed using a standard 304 stainless steel reactor, eliminating the need for a reactor made of special materials.

[0111] The present invention will be further illustrated below with specific embodiments and comparative examples.

[0112] Example 1 (S1)

[0113] A system for producing syngas from carbon dioxide and hydrogen, such as Figure 1As shown, the system includes n-stage reverse vapor shift units arranged in series, n=3, including a first reverse vapor shift unit, a second reverse vapor shift unit, and a third reverse vapor shift unit, used to sequentially perform three-stage reverse vapor shift reactions on the feed CO2 and H2 to obtain syngas; wherein, the heat is provided by the combustion of CH4;

[0114] The first reverse vapor shift unit includes a first reverse vapor shift reactor 1 and a first dehydration device 2 connected in sequence. The inlet of the first reverse vapor shift reactor 1 is provided with a CO2 inlet pipeline 3 and an H2 inlet pipeline 4, which are used to introduce CO2 and H2 respectively to carry out a first-stage reverse vapor shift reaction, and output a first syngas including CO, H2, CH4, water vapor and CO2. The inlet of the first dehydration device 2 is connected to the outlet of the first reverse vapor shift reactor 1, and is used to dehydrate the first syngas from the first reverse vapor shift reactor 1, and output a first dehydrated syngas. The first reverse vapor shift unit also includes a first heat exchanger 9, the inlet of the first heat exchanger 9 is connected to the outlet of the CO2 inlet pipeline 3 and the outlet of the H2 inlet pipeline 4 respectively, and the outlet of the first heat exchanger 9 is connected to the inlet of the first reverse vapor shift reactor 1, and is used to preheat the CO2 and H2 to be entering the first reverse vapor shift reactor 1.

[0115] The second reverse vapor shift unit includes a second reverse vapor shift reactor 5 and a second dehydration device 6 connected in sequence. The inlet of the second reverse vapor shift reactor 5 is connected to the outlet of the first dehydration device 2, for introducing the first dehydrated syngas from the first dehydration device 2 to perform a second-stage reverse vapor shift reaction using CO2 and H2 therein, and outputting a second syngas including CO, H2, CH4, water vapor and CO2. The inlet of the second dehydration device 6 is connected to the outlet of the second reverse vapor shift reactor 5, for dehydrating the second syngas from the second reverse vapor shift reactor 5, and outputting a second dehydrated syngas. The second reverse vapor shift unit also includes a second heat exchanger 10, the inlet of which is connected to the outlet of the first dehydration device 2, and the outlet of which is connected to the inlet of the second reverse vapor shift reactor 5, for preheating the first dehydrated syngas to be introduced into the second reverse vapor shift reactor 5.

[0116] The third reverse steam shift unit includes a third reverse steam shift reactor 7 and a third dehydration device 8 connected in sequence. The inlet of the third reverse steam shift reactor 7 is connected to the outlet of the second dehydration device 6, for introducing the second dehydrated syngas from the second dehydration device 6 to perform a three-stage reverse steam shift reaction using CO2 and H2, and outputting a third syngas including CO, H2, CH4, water vapor and CO2. The inlet of the third dehydration device 8 is connected to the outlet of the third reverse steam shift reactor 7, for dehydrating the third syngas from the third reverse steam shift reactor 7, and outputting the third dehydrated syngas as product gas. The third reverse steam shift unit also includes a third heat exchanger 11, the inlet of which is connected to the outlet of the second dehydration device 6, and the outlet of which is connected to the inlet of the third reverse steam shift reactor 7, for preheating the second dehydrated syngas to be introduced into the third reverse steam shift reactor 7.

[0117] The first reverse steam shift reactor 1, the second reverse steam shift reactor 5, and the third reverse steam shift reactor 7 are tubular reactors;

[0118] The first dehydration device 2, the second dehydration device 6, and the third dehydration device 8 are gas-liquid separators.

[0119] A process for preparing syngas from carbon dioxide and hydrogen involves using the aforementioned system to perform an n-stage reverse water-gas shift reaction between carbon dioxide and hydrogen to obtain syngas; where n = 3.

[0120] In the n-stage reverse water-gas shift reaction, the catalyst used is a Cr2O3 / MgAl2O4-TiO2 catalyst;

[0121] The Cr2O3 / MgAl2O4-TiO2 catalyst is a catalyst formed by supporting Cr2O3 on a TiO2-modified MgAl2O4 spinel support; in the Cr2O3 / MgAl2O4-TiO2 catalyst, the content of Cr2O3 is 5 wt%, the content of TiO2 is 7.5 wt%, the content of MgO is 25 wt%, and the content of Al2O3 is 62.5 wt%.

[0122] The reaction conditions for the nth-stage reverse water-gas shift reaction include:

[0123] The reaction pressure was 2.0 MPa, the reaction temperature was 500℃, and the space velocity was 10000 h⁻¹. -1 ;

[0124] The composition of the feed gas includes a volume ratio of H2 to CO2 of 77 / 23.

[0125] The process includes the following steps:

[0126] (1) CO2 and H2 are preheated to 300°C and then fed to the first reverse water-gas shift reactor 1 for a first-stage reverse water-gas shift reaction, and the output is a first synthesis gas including CO, H2, CH4, water vapor and CO2;

[0127] (2) The first syngas obtained in step (1) is fed into the first dehydration device 2 and dehydrated at 20°C to output the first dehydrated syngas; wherein,

[0128] The gas composition of the first dehydrated syngas includes CO2 / H2 / CO / CH4 = 12.6 v% / 73.6 v% / 13.6 v% / 0.2 v%, and the conversion rate of CO2 in the first reverse water-gas shift reactor 1 is 51.9%.

[0129] (3) The first dehydrated syngas obtained in step (2) is preheated to 300°C and then sent to the second reverse water vapor shift reactor 5 for a second-stage reverse water vapor shift reaction, and the output is a second syngas including CO, H2, CH4, water vapor and CO2;

[0130] (4) The second syngas obtained in step (3) is transported to the second dehydration device 6 for dehydration at 20°C, and the second dehydrated syngas is output; wherein,

[0131] The gas composition of the second dehydrated syngas includes CO2 / H2 / CO / CH4 = 7.7v% / 72v% / 19.9v% / 0.4v%, and the conversion rate of CO2 in the second reverse water-gas shift reactor 5 is 41.8%.

[0132] (5) The second dehydrated syngas obtained in step (4) is preheated to 300°C and then transported to the third reverse water-gas shift reactor 7 for a three-stage reverse water-gas shift reaction, and the output is a third syngas including CO, H2, CH4, water vapor and CO2;

[0133] (6) The third syngas obtained in step (5) is transported to the third dehydration device 8 for dehydration at 20°C, and the third dehydrated syngas is output; wherein,

[0134] The gas composition of the third dehydrated synthesis gas, which is the product gas, includes CO2 / H2 / CO / CH4 = 5v% / 71.1v% / 23.3v% / 0.6v%, (H2-CO2) / (CO+CO2) = 2.3; the conversion rate of CO2 in the third reverse water-gas shift reactor 7 is 37.6%;

[0135] The total CO2 conversion rate in the three-stage reverse water-gas shift reaction is 82.5%.

[0136] Example 2 (S2)

[0137] The only difference from Example 1 is:

[0138] In the Cr2O3 / MgAl2O4-TiO2 catalyst, the content of Cr2O3 is 2wt%, the content of TiO2 is 5wt%, the content of MgO is 23wt%, and the content of Al2O3 is 70wt%.

[0139] The gas composition of the first dehydrated syngas includes CO2 / H2 / CO / CH4 = 12.4v% / 73.9v% / 13.4v% / 0.3v%, and the conversion rate of CO2 in the first reverse water-gas shift reactor 1 is 51.5%.

[0140] The gas composition of the second dehydrated syngas includes CO2 / H2 / CO / CH4 = 7.5v% / 72.7v% / 19.3v% / 0.5v%, and the conversion rate of CO2 in the second reverse water-gas shift reactor 5 is 41.5%.

[0141] The gas composition of the third dehydrated synthesis gas, which is the product gas, includes 4.8 v% / 72.3 v% / 22.2 v% / 0.7 v%, (H2-CO2) / (CO+CO2) = 2.5; the conversion rate of CO2 in the third reverse water-gas shift reactor 7 is 38.1%;

[0142] The total CO2 conversion rate in the three-stage reverse water-gas shift reaction is 82.8%.

[0143] Example 3 (S3)

[0144] The only difference from Example 1 is:

[0145] The Cr2O3 / MgAl2O4-TiO2 catalyst contains 8 wt% Cr2O3, 16 wt% TiO2, 26 wt% MgO, and 50 wt% Al2O3.

[0146] The gas composition of the first dehydrated syngas includes CO2 / H2 / CO / CH4 = 12.8v% / 73.2v% / 13.8v% / 0.2v%, and the conversion rate of CO2 in the first reverse water-gas shift reactor 1 is 51.1%.

[0147] The gas composition of the second dehydrated syngas includes CO2 / H2 / CO / CH4 = 7.2v% / 72.9v% / 19.5v% / 0.4v%, and the conversion rate of CO2 in the second reverse water-gas shift reactor 5 is 41.7%.

[0148] The gas composition of the third dehydrated synthesis gas, which is the product gas, includes CO2 / H2 / CO / CH4 = 4.7v% / 72.4v% / 22.3v% / 0.6v%, (H2-CO2) / (CO+CO2) = 2.5; the conversion rate of CO2 in the third reverse water-gas shift reactor 7 is 38.4%;

[0149] The total CO2 conversion rate in the three-stage reverse water-gas shift reaction is 83.0%.

[0150] Example 4 (S4)

[0151] The only difference from Example 1 is:

[0152] The reaction conditions for the nth-stage reverse water-gas shift reaction include:

[0153] The reaction pressure was 5.0 MPa, the reaction temperature was 550 °C, and the space velocity was 15000 h⁻¹. -1 .

[0154] The gas composition of the first dehydrated syngas includes CO2 / H2 / CO / CH4 = 11.8 v% / 72.2 v% / 15.7 v% / 0.3 v%, and the conversion rate of CO2 in the first reverse water-gas shift reactor 1 is 53.2%.

[0155] The gas composition of the second dehydrated syngas includes CO2 / H2 / CO / CH4 = 6.9v% / 70.9v% / 21.5v% / 0.7v%, and the conversion rate of CO2 in the second reverse water-gas shift reactor 5 is 42.1%.

[0156] The gas composition of the third dehydrated synthesis gas, which is the product gas, includes CO2 / H2 / CO / CH4 = 4.6v% / 69.8v% / 24.7v% / 0.9v%, (H2-CO2) / (CO+CO2) = 2.2; the conversion rate of CO2 in the third reverse water-gas shift reactor 7 is 38.5%;

[0157] The total CO2 conversion rate in the three-stage reverse water-gas shift reaction is 83.5%.

[0158] Example 5 (S5)

[0159] The only difference from Example 1 is:

[0160] The reaction conditions for the nth-stage reverse water-gas shift reaction include:

[0161] The reaction pressure was 1.0 MPa, the reaction temperature was 450℃, and the space velocity was 5000 h⁻¹. -1 ;

[0162] The gas composition of the first dehydrated syngas includes CO2 / H2 / CO / CH4 = 12.3v% / 73.1v% / 14.5v% / 0.1v%, and the conversion rate of CO2 in the first reverse water-gas shift reactor 1 is 52.1%.

[0163] The gas composition of the second dehydrated syngas includes CO2 / H2 / CO / CH4 = 7.2v% / 72.1v% / 20.4v% / 0.3v%, and the conversion rate of CO2 in the second reverse water-gas shift reactor 5 is 41.9%.

[0164] The gas composition of the third dehydrated synthesis gas, which is the product gas, includes CO2 / H2 / CO / CH4 = 4.8v% / 70.0v% / 24.7v% / 0.5v%, (H2-CO2) / (CO+CO2) = 2.2; the conversion rate of CO2 in the third reverse water-gas shift reactor 7 is 39.2%;

[0165] The total CO2 conversion rate in the three-stage reverse water-gas shift reaction is 82.4%.

[0166] Example 6 (S6)

[0167] The only difference from Example 1 is:

[0168] The composition of the feed gas includes H2 and CO2 in a volume ratio of 80 / 20.

[0169] The gas composition of the first dehydrated syngas includes CO2 / H2 / CO / CH4 = 11.9 v% / 76.6 v% / 11.3 v% / 0.2 v%, and the conversion rate of CO2 in the first reverse water-gas shift reactor 1 is 52.5%.

[0170] The gas composition of the second dehydrated syngas includes CO2 / H2 / CO / CH4 = 7.2v% / 74.2v% / 18.2v% / 0.4v%, and the conversion rate of CO2 in the second reverse water-gas shift reactor 5 is 42.7%.

[0171] The gas composition of the third dehydrated synthesis gas, which is the product gas, includes CO2 / H2 / CO / CH4 = 4.7v% / 72.4v% / 22.3v% / 0.6v%, (H2-CO2) / (CO+CO2) = 2.5; the conversion rate of CO2 in the third reverse water-gas shift reactor 7 is 37.2%;

[0172] The total CO2 conversion rate in the three-stage reverse water-gas shift reaction is 83.5%.

[0173] Example 7 (S7)

[0174] The only difference from Example 1 is:

[0175] The composition of the feed gas includes a volume ratio of H2 to CO2 of 75 / 25.

[0176] The gas composition of the first dehydrated syngas includes CO2 / H2 / CO / CH4 = 13.8 v% / 72.3 v% / 13.6 v% / 0.3 v%, and the conversion rate of CO2 in the first reverse water-gas shift reactor 1 is 50.5%.

[0177] The gas composition of the second dehydrated syngas includes CO2 / H2 / CO / CH4 = 8.1v% / 71.2v% / 20.1v% / 0.6v%, and the conversion rate of CO2 in the second reverse water-gas shift reactor 5 is 40.5%.

[0178] The gas composition of the third dehydrated synthesis gas, which is the product gas, includes CO2 / H2 / CO / CH4 = 5.0 v% / 69.1 v% / 25.0 v% / 0.9 v%, (H2-CO2) / (CO+CO2) = 2.1; the conversion rate of CO2 in the third reverse water-gas shift reactor 7 is 38.3%;

[0179] The total CO2 conversion rate in the three-stage reverse water-gas shift reaction is 82.2%.

[0180] Example 8 (S8)

[0181] The only difference from Example 1 is:

[0182] A system for producing syngas from carbon dioxide and hydrogen, such as Figure 2 As shown, n=4; the system includes n-stage reverse steam shift units arranged in series, and also includes a fourth reverse steam shift unit, used to sequentially perform three-stage reverse steam shift reactions on the feed CO2 and H2 to obtain syngas; wherein,

[0183] The fourth reverse steam shift unit includes a fourth reverse steam shift reactor and a fourth dehydration device connected in sequence. The feed inlet of the fourth reverse steam shift reactor is connected to the discharge outlet of the third dehydration device 8, for introducing the second dehydrated syngas from the third dehydration device 8 to perform a four-stage reverse steam shift reaction using CO2 and H2 therein, and outputting a fourth syngas including CO, H2, CH4, water vapor and CO2. The feed inlet of the fourth dehydration device is connected to the discharge outlet of the fourth reverse steam shift reactor, for dehydrating the fourth syngas from the fourth reverse steam shift reactor, and outputting the fourth dehydrated syngas as product gas.

[0184] The fourth reverse water-gas shift unit also includes a fourth heat exchanger. The inlet of the fourth heat exchanger is connected to the outlet of the third dehydration device, and the outlet of the fourth heat exchanger is connected to the inlet of the fourth reverse water-gas shift reactor. It is used to preheat the third dehydrated syngas to be entered into the fourth reverse water-gas shift reactor.

[0185] The fourth reverse steam shift reactor is a tubular reactor;

[0186] The fourth dehydration device is a gas-liquid separator.

[0187] A process for preparing syngas from carbon dioxide and hydrogen involves using the aforementioned system to perform an n-stage reverse water-gas shift reaction between carbon dioxide and hydrogen to obtain syngas; where n = 4.

[0188] The process also includes the following steps:

[0189] (7) The third dehydrated syngas obtained in step (6) is preheated to 300°C and then sent to the fourth reverse water-gas shift reactor to carry out a four-stage reverse water-gas shift reaction, and outputs a fourth syngas including CO, H2, CH4, water vapor and CO2;

[0190] (8) The fourth synthesis gas obtained in step (7) is transported to the fourth dehydration equipment for dehydration, and the fourth dehydrated synthesis gas is output as product gas.

[0191] The gas composition of the fourth dehydrated synthesis gas, which is the product gas, includes CO2 / H2 / CO / CH4 = 3.3v% / 70.7v% / 25.2v% / 0.8v%, (H2-CO2) / (CO+CO2) = 2.4; the conversion rate of CO2 in the fourth reverse water-gas shift reactor is 35.5%;

[0192] The total CO2 conversion rate in the 4-stage reverse water-gas shift reaction is 88.7%.

[0193] Comparative Example 1 (D1)

[0194] The only difference from Example 1 is:

[0195] In the n-stage reverse water-gas shift reaction, the catalyst used is a NiO / MgAl2O4-TiO2 catalyst formed by replacing Cr2O3 in the Cr2O3 / MgAl2O4-TiO2 catalyst with an equal amount of NiO.

[0196] The Cr2O3 / MgAl2O4-TiO2 catalyst is a catalyst formed by supporting NiO on a TiO2-modified MgAl2O4 spinel support; in the NiO / MgAl2O4-TiO2 catalyst, the content of NiO is 5 wt%, the content of TiO2 is 7.5 wt%, the content of MgO is 25 wt%, and the content of Al2O3 is 62.5 wt%.

[0197] The gas composition of the first dehydrated syngas includes CO2 / H2 / CO / CH4 = 23.2 v% / 55.8 v% / 10.7 v% / 10.3 v%, and the conversion rate of CO2 in the first reverse water-gas shift reactor 1 is 47.5%.

[0198] The gas composition of the second dehydrated syngas includes CO2 / H2 / CO / CH4 = 17.2v% / 52.2v% / 15.2v% / 15.4v%, and the conversion rate of CO2 in the second reverse water-gas shift reactor 5 is 32.5%.

[0199] The gas composition of the third dehydrated synthesis gas, which is the product gas, includes CO2 / H2 / CO / CH4 = 12.3v% / 50.7v% / 18.3v% / 18.7v%, (H2-CO2) / (CO+CO2) = 1.3; the conversion rate of CO2 in the third reverse water-gas shift reactor 7 is 28.7%;

[0200] The total CO2 conversion rate in the three-stage reverse water-gas shift reaction is 75.1%.

[0201] Comparative Example 2 (D2)

[0202] The only difference from Example 1 is as follows:

[0203] A system for producing syngas by reacting carbon dioxide and hydrogen, comprising only a first reverse water-gas shift unit;

[0204] A process for producing syngas from carbon dioxide and hydrogen, wherein the reaction conditions for the reverse water-gas shift reaction include:

[0205] The reaction pressure was 2 MPa, the reaction temperature was 700℃, and the space velocity was 10000 h⁻¹. -1 ;

[0206] The process includes the following steps:

[0207] (1) CO2 and H2 are preheated to 300°C and then fed to the first reverse water-gas shift reactor 1 for a first-stage reverse water-gas shift reaction, and the output is a first synthesis gas including CO, H2, CH4, water vapor and CO2;

[0208] (2) The first syngas obtained in step (1) is fed into the first dehydration device 2 and dehydrated at 20°C to output the first dehydrated syngas; wherein,

[0209] The gas composition of the first dehydrated syngas includes CO2 / H2 / CO / CH4 = 13.6 v% / 60.6 v% / 15.6 v% / 10.2 v%, (H2-CO2) / (CO+CO2) = 1.6; the conversion rate of CO2 is 65.5%.

[0210] The gas composition, (H2-CO2) / (CO+CO2) modulus, and total CO2 conversion rate of the obtained synthesis gas in Examples 1-8 (S1-8) and Comparative Examples 1-2 (D1-2) are shown in Table 1.

[0211] Table 1 shows the gas composition, (H2-CO2) / (CO+CO2) modulus, and total CO2 conversion rate of the syngas obtained in S1-8 and D1-2.

[0212]

[0213] Note: In Table 1, the standard for direct-use syngas refers to the standard for syngas that can be directly used in the production of chemicals or oils.

[0214] Based on the comparison of Examples 1-8 and Comparative Examples 1-2, and the data in Table 1, it can be seen that the system and process of the present invention can perform a reverse water-gas shift reaction on CO2 and H2, and achieve a high conversion rate of CO2, thereby obtaining syngas that can be directly used to produce chemicals or oils.

[0215] A comparison of Example 1 and Comparative Example 1 shows that, under the same conditions and system, if a NiO / MgAl2O4-TiO2 catalyst is used to replace the Cr2O3 / MgAl2O4-TiO2 catalyst of this application for the reverse water-gas shift reaction of CO2 and H2, the resulting syngas contains excessively high levels of CO2 and CH4, failing to meet the standards for syngas directly used in the production of chemicals or oils. Therefore, it cannot be used directly for the production of chemicals or oils. Further removal of carbon dioxide and cryogenic separation of CH4 are required for its use, which is a complex and costly process.

[0216] A comparison of Example 1 and Comparative Example 2 shows that, under the same conditions, if only a first-order reverse water-gas shift reaction is performed on CO2 and H2, the resulting syngas contains excessively high levels of CO2 and CH4, failing to meet the standards for syngas directly used in the production of chemicals or oils. Therefore, it cannot be used directly for this purpose. Further removal of carbon dioxide and cryogenic separation of CH4 are required for its use in the production of chemicals or oils, resulting in a complex and costly process.

Claims

1. A system for producing syngas by reacting carbon dioxide and hydrogen, characterized in that, The system includes n-stage reverse vapor shift units (RPF) arranged in series, where n ≥ 3, used to sequentially perform n-stage reverse vapor shift reactions on feed CO2 and H2 to obtain syngas; wherein... The catalyst used in the n-stage reverse water-gas shift reaction is a Cr2O3 / MgAl2O4-TiO2 catalyst; the Cr2O3 / MgAl2O4-TiO2 catalyst is a catalyst formed by supporting Cr2O3 on a TiO2-modified MgAl2O4 spinel support; in the Cr2O3 / MgAl2O4-TiO2 catalyst, the content of Cr2O3 is 2-8 wt%, the content of TiO2 is 5-16 wt%, the content of MgO is 20-30 wt%, and the content of Al2O3 is 50-70 wt%. The n-stage reverse water vapor conversion unit includes a first reverse water vapor conversion unit, a second reverse water vapor conversion unit, and a third reverse water vapor conversion unit; The first reverse steam shift unit includes a first reverse steam shift reactor (1) and a first dehydration device (2) connected in sequence. The feed inlet of the first reverse steam shift reactor (1) is provided with a CO2 inlet pipeline (3) and an H2 inlet pipeline (4) for introducing CO2 and H2 respectively to carry out a first-stage reverse steam shift reaction, and outputting a first synthesis gas including CO, H2, CH4, water vapor and CO2. The feed inlet of the first dehydration device (2) is connected to the discharge outlet of the first reverse steam shift reactor (1) for dehydrating the first synthesis gas from the first reverse steam shift reactor (1) and outputting a first dehydrated synthesis gas. The second reverse steam shift unit includes a second reverse steam shift reactor (5) and a second dehydration device (6) connected in sequence; the inlet of the second reverse steam shift reactor (5) is connected to the outlet of the first dehydration device (2) for introducing the first dehydrated syngas from the first dehydration device (2) to utilize the CO2 and H2 therein for a second-stage reverse steam shift reaction, and outputting a second syngas including CO, H2, CH4, water vapor and CO2; the inlet of the second dehydration device (6) is connected to the outlet of the second reverse steam shift reactor (5) for dehydrating the second syngas from the second reverse steam shift reactor (5) and outputting the second dehydrated syngas. The third reverse steam shift unit includes a third reverse steam shift reactor (7) and a third dehydration device (8) connected in sequence. The feed inlet of the third reverse steam shift reactor (7) is connected to the discharge outlet of the second dehydration device (6) to introduce the second dehydrated syngas from the second dehydration device (6) to utilize the CO2 and H2 therein for a three-stage reverse steam shift reaction, and output a third syngas including CO, H2, CH4, water vapor and CO2. The feed inlet of the third dehydration device (8) is connected to the discharge outlet of the third reverse steam shift reactor (7) to dehydrate the third syngas from the third reverse steam shift reactor (7) and output the third dehydrated syngas.

2. The system according to claim 1, characterized in that, The first reverse steam-water conversion unit further includes a first heat exchanger (9), the inlet of which is connected to the outlet of the CO2 inlet pipeline (3) and the H2 inlet pipeline (4), respectively, and the outlet of which is connected to the inlet of the first reverse steam-water conversion reactor (1), for preheating the CO2 and H2 to be entered into the first reverse steam-water conversion reactor (1); and / or The second reverse steam shift unit further includes a second heat exchanger (10), the inlet of which is connected to the outlet of the first dehydration device (2), and the outlet of which is connected to the inlet of the second reverse steam shift reactor (5), for preheating the first dehydrated syngas to be entered into the second reverse steam shift reactor (5); and / or The third reverse water-gas shift unit also includes a third heat exchanger (11), the inlet of which is connected to the outlet of the second dehydration device (6), and the outlet of which is connected to the inlet of the third reverse water-gas shift reactor (7), for preheating the second dehydrated syngas to be entered into the third reverse water-gas shift reactor (7).

3. The system according to claim 1 or 2, characterized in that, The first reverse steam shift reactor (1) is a tubular reactor; and / or the first dehydration device (2) is a gas-liquid separator; and / or The second reverse steam shift reactor (5) is a tubular reactor; and / or the second dehydration device (6) is a gas-liquid separator; and / or The third reverse water-gas shift reactor (7) is a tubular reactor; and / or the third dehydration device (8) is a gas-liquid separator.

4. A process for preparing syngas by reacting carbon dioxide and hydrogen, characterized in that, Using the system described in any one of claims 1-3, carbon dioxide and hydrogen undergo an n-stage reverse water-gas shift reaction to obtain syngas.

5. The process according to claim 4, characterized in that, The reaction conditions for the nth-stage reverse water-gas shift reaction include: The reaction pressure is 1.0-5.0 MPa, the reaction temperature is 450-550 ℃, and the space velocity is 5000-15000 h⁻¹. -1 .

6. The process according to claim 5, characterized in that, The composition of the raw gas includes H2 and CO2 in a volume ratio of 3-4.

7. The process according to any one of claims 4-6, characterized in that, Includes the following steps: (1) CO2 and H2 are respectively fed to the first reverse water-gas shift reactor (1) to carry out a first-stage reverse water-gas shift reaction, and the output includes CO, H2, CH4, water vapor and CO2 as the first synthesis gas; (2) The first syngas obtained in step (1) is transported to the first dehydration device (2) for dehydration, and the first dehydrated syngas is output; (3) The first dehydrated syngas obtained in step (2) is transported to the second reverse water-gas shift reactor (5) for a second-stage reverse water-gas shift reaction, and the output is a second syngas including CO, H2, CH4, water vapor and CO2; (4) The second syngas obtained in step (3) is sent to the second dehydration device (6) for dehydration, and the second dehydrated syngas is output; (5) The second dehydrated syngas obtained in step (4) is transported to the third reverse water-gas shift reactor (7) for a three-stage reverse water-gas shift reaction, and the output is a third syngas including CO, H2, CH4, water vapor and CO2; (6) The third syngas obtained in step (5) is transported to the third dehydration device (8) for dehydration and the third dehydrated syngas is output.

8. The process according to claim 7, characterized in that, The first reverse water-gas shift unit also includes a first heat exchanger (9). The inlet of the first heat exchanger (9) is connected to the outlet of the CO2 inlet pipeline (3) and the H2 inlet pipeline (4), respectively. The outlet of the first heat exchanger (9) is connected to the inlet of the first reverse water-gas shift reactor (1) for preheating the CO2 and H2 to be entered into the first reverse water-gas shift reactor (1). In step (1), CO2 and H2 are first sent to the first heat exchanger (9) for preheating before being sent to the first reverse water-gas shift reactor (1).

9. The process according to claim 8, characterized in that, In step (1), preheat to 200-400 ℃.

10. The process according to claim 7, characterized in that, The second reverse water-gas shift unit also includes a second heat exchanger (10), the inlet of the second heat exchanger (10) is connected to the outlet of the first dehydration device (2), and the outlet of the second heat exchanger (10) is connected to the inlet of the second reverse water-gas shift reactor (5) for preheating the first dehydrated syngas to be entered into the second reverse water-gas shift reactor (5); In step (3), before the first dehydrated syngas obtained in step (2) is transported to the second reverse water-gas shift reactor (5), it is first transported to the second heat exchanger (10) for preheating.

11. The process according to claim 10, characterized in that, In step (3), preheat to 200-400 ℃.

12. The process according to claim 7, characterized in that, The third reverse water-gas shift unit also includes a third heat exchanger (11), the inlet of which is connected to the outlet of the second dehydration device (6), and the outlet of which is connected to the inlet of the third reverse water-gas shift reactor (7), for preheating the second dehydrated syngas to be entered into the third reverse water-gas shift reactor (7). In step (5), before the second dehydrated syngas obtained in step (4) is transported to the third reverse water-gas shift reactor (7), it is first transported to the third heat exchanger (11) for preheating.

13. The process according to claim 12, characterized in that, In step (5), preheat to 200-400 ℃.

14. The synthesis gas obtained by the process according to any one of claims 4-6 and 8-13, characterized in that, The synthesis gas contains CO2 with a content of ≤5 v%, a (H2-CO2) / (CO+CO2) modulus of 2.1-2.5, and CH4 with a content of ≤1 v%.

15. The use of the syngas obtained by the process according to any one of claims 4-14 in the preparation of chemicals or petroleum products.

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