Controllable polyunsaturated hydrocarbon selective hydrogenation method and application

Abstract

The invention relates to the research field of polyunsaturated hydrocarbon selective hydrogenation, requests to protect a controllable polyunsaturated hydrocarbon selective hydrogenation method and application, and particularly relates to a method for removing acetylene from C2 and C3 fractions through selective hydrogenation and application. The catalyst mainly comprises hydrogen, carbon monoxide, acetylene, ethylene, ethane, propylene, propane, a small amount of propyne, propadiene and the like. In a catalytic hydrogenation reactor system, a hydrogenation inlet material is contacted with a catalytic hydrogenation catalyst, and under controllable reaction conditions, acetylene in the hydrogenation inlet material is completely hydrogenated to produce a hydrogenation effluent. In order to cope with the change of cracking gas of the cracking device, crude hydrogen and / or dry hydrogen are / is adopted as a regulation and control means to improve ethylene selectivity and operation stability.

Description

Technical Field

[0001] The invention relates to the research field of selective hydrogenation of polyunsaturated hydrocarbons, specifically to a method and application of selective hydrogenation of a C2C3 fraction to remove acetylene, and more specifically to an operating method of an acetylene catalytic hydrogenation unit in an olefin production process. Background Art

[0002] Ethylene is one of the most important basic raw materials for petrochemical industry, and ethylene products account for more than 75% of petrochemical products. Ethylene can be used to manufacture polyethylene, polyvinyl chloride, ethylene oxide / ethylene glycol, styrene, vinyl acetate, etc. These products can be used for packaging, construction, textiles, surfactants and other purposes. The production capacity of ethylene is a symbol of the development level of a country's petrochemical industry. There are many methods for producing ethylene, including steam cracking, catalytic cracking, coal / methanol to olefins, ethane cracking to ethylene, ethanol dehydration, etc. Among them, ethylene produced by steam cracking of petroleum hydrocarbons accounts for more than 90% of the world's total ethylene production. However, polyunsaturated hydrocarbons such as acetylene, propyne, and propadiene will be produced during the production of ethylene by hydrocarbon cracking. The presence of these polyunsaturated hydrocarbons will reduce the polymerization efficiency of downstream polymerization catalysts, affect the quality of polymerization products, and bring safety hazards to the production and processing of downstream products. The carbon distillate mainly composed of ethylene obtained by steam cracking of petroleum hydrocarbons (naphtha, light diesel, light hydrocarbons, etc.) contains about 0.5% to 2.5% acetylene. With the advancement of downstream process technology, the requirements for the acetylene content in ethylene products are becoming more and more stringent. In the 1960s, the acetylene content in ethylene was required to be less than 10ppm, in the 1970s it was required to be less than 2ppm, and since the late 1980s it has been required to be less than 1ppm. Currently, catalytic selective hydrogenation technology is mostly used in industrial production to remove acetylene contained in carbon distillation. This technology has the advantages of simple process flow, small ethylene loss and high ethylene yield.

[0003] The separation process of petroleum hydrocarbon steam cracking to produce ethylene is mainly divided into three major technologies, including sequential separation technology, pre-depropanization pre-hydrogenation technology, and pre-de-ethanization pre-hydrogenation technology. The pre-depropanization pre-hydrogenation technology has low comprehensive energy consumption, low cracking gas compressor power, is more suitable for large-scale ethylene devices, and is widely used. The present invention mainly relates to the selective hydrogenation process of acetylene in the pre-depropanization pre-hydrogenation technology. In the pre-depropanization pre-hydrogenation process, the carbon two carbon three fraction at the top of the depropanizer tower mainly contains hydrogen, carbon monoxide, acetylene, ethylene, ethane, and also includes carbon three components such as propylene, propane, propyne, and propadiene. In the acetylene selective hydrogenation process, there is also a selective hydrogenation reaction process of propyne and propadiene, as well as a side reaction process of ethylene and propylene hydrogenation to generate alkanes. In the pre-depropanization pre-hydrogenation process, the top carbon two carbon three fraction itself contains the hydrogen required for the reaction, as well as a high content of carbon monoxide that inhibits the hydrogenation activity, so the pre-hydrogenation process has the advantage of high selectivity.

[0004] Research on the pre-depropanization pre-hydrogenation reactor system usually focuses on developing catalysts with better performance. Acetylene hydrogenation catalysts usually use precious metals Pd, Ru, and Rh as active components, and are prepared by adding various additives including alkali metals, alkaline earth metals, etc., selecting suitable carriers including alumina, silica, etc., and impregnating, spraying, etc. Patent CN112679306 A discloses a selective hydrogenation method for a carbon two post-hydrogenation process using crude hydrogen as a hydrogen source. The reaction process conditions on a single-stage fixed bed reactor are: inlet temperature 65-130°C, pressure 1.5-3.0MPa, gas volume space velocity 1500-4000h1, ethylene volume content 70%-93% in the catalytic reaction material, acetylene volume content 0.6%-1.3%, carbon three fraction volume content 0.01%-0.5%, and the hydrogen-acetylene ratio in the reactor inlet material is 23. The hydrogenation method uses a catalyst containing at least Pd, Ag, Ni, and Cu, and the carrier uses alumina with a bimodal pore distribution structure. The loading of Ni, Cu and part of Pd adopts the microemulsion method, and most of Pd, Ni and Cu enter the macropores of the catalyst during loading. The loading of part of Pd adopts the supersaturated impregnation method, and most of Pd enters the small pores on the surface of the carrier due to the capillary siphon effect. The loading of Ag adopts the saturated impregnation method. The selective hydrogenation method of the invention has excellent anti-coking performance. Patent CN116020374A discloses an acetylene hydrogenation reactor and its temperature control method. The hydrocarbon gas feed pipeline containing alkynes is connected to the top of the reactor section; the first emergency cooler is arranged on the branch pipeline where the reactor section feed circulating water cooler is located and is located downstream of the reactor section feed circulating water cooler or connected to the reactor section feed circulating water cooler or is separately arranged on the third branch pipeline; a discharge pipeline is arranged at the bottom of the reactor section to connect the top of the reactor section 2; a second discharge pipeline is arranged at the bottom of the reactor section 2 to connect the top of the reactor section 3; regulating valves are arranged on the pipelines where all heaters and coolers are located, and they are all connected to the temperature control element, the quenching interlock signal and the parking interlock signal. By using the control method of the present invention, abnormal operating conditions can be eliminated as soon as possible, the reactor can quickly resume production, interlock shutdown caused by temperature runaway can be reduced or even eliminated, and the efficiency of the device can be increased.

[0005] At present, the ethylene production capacity at home and abroad is increasing rapidly. With the increase in the scale of ethylene plants and the change in the raw materials of ethylene plants, the acetylene hydrogenation performance requirements of the C2 hydrogenation reactor system are getting higher and higher. The scale of ethylene plants has expanded from an average of about 300,000 tons / year in the 1960s and 1970s to the current average scale of more than 1 million tons / year, and the scale of a single ethylene plant has even reached 1.5 million tons / year. The increase in the scale of ethylene plants has put higher and higher requirements on the performance of acetylene selective hydrogenation in the C2 and C3 fractions. The catalytic selective hydrogenation process of acetylene hydrogenation requires good selectivity and stability, as well as operability, to meet the "safe, stable, full and excellent" operation requirements of ethylene plants. Summary of the invention

[0006] In the pre-depropanization pre-hydrogenation process, the catalytic hydrogenation reactor system usually adopts one-stage, two-stage or three-stage hydrogenation, and there is no spare reactor. When the feed of the C2C3 fraction is stable, the acetylene hydrogenation reactor system can operate smoothly. Due to changes in the production capacity of the ethylene unit, the switching of cracking raw materials, and changes in the operating conditions of the cracking process, the feed conditions of the catalytic hydrogenation reactor system vary greatly. Changes in feed conditions will affect the smooth operation of the catalytic hydrogenation reactor system, affecting ethylene selectivity and catalyst operating life. When the concentration of hydrogen or carbon monoxide in the C2C3 fraction changes significantly, the catalytic hydrogenation reactor system is prone to acetylene leakage or temperature runaway, affecting the continuous production of the ethylene unit and causing huge economic losses.

[0007] In order to solve the problems in the prior art, the present invention provides a controllable method and application of selective hydrogenation of polyunsaturated hydrocarbons. In the separation process of hydrocarbon cracking products, the carbon 2 and carbon 3 fractions from the top of the depropanizer tower mainly include hydrogen, carbon monoxide, acetylene, ethylene, ethane, propylene, propane, and a small amount of propyne, propadiene, etc. In the catalytic hydrogenation reactor system, the hydrogenation inlet material contacts the catalytic hydrogenation catalyst. Under appropriate reaction conditions, all the acetylene in the hydrogenation inlet material is hydrogenated to produce a hydrogenation effluent. In order to cope with the changes in the cracking gas of the cracking unit, crude hydrogen and / or dry hydrogen are used as a control method to improve ethylene selectivity and operational stability.

[0008] The first aspect of the present invention is to provide a method for selective hydrogenation of polyunsaturated hydrocarbons, the method comprising:

[0009] Using the C2C3 fraction extracted from the top of a depropanizer as a hydrogenation material raw material, and inputting crude hydrogen and / or dry hydrogen into the C2C3 fraction before entering a hydrogenation reactor according to changes in the hydrogen and / or carbon monoxide content in the C2C3 fraction, to obtain a hydrogenation material with hydrogen and / or carbon monoxide content within a target range;

[0010] The hydrogenated material is contacted with a catalytic hydrogenation catalyst to perform a hydrogenation reaction, and the acetylene in the hydrogenated material is subjected to a hydrogenation reaction to produce a hydrogenation effluent;

[0011] The crude hydrogen contains 80% to 100% by volume of hydrogen, 500 to 20,000 ppmv of carbon monoxide, and a balance gas;

[0012] The dry hydrogen contains 80% to 100% by volume of hydrogen and a balance of gas.

[0013] The balancing gas in the present invention includes but is not limited to methane.

[0014] In the present invention, the carbon 2-carbon 3 fraction extracted from the top of the depropanizer generally comes from: hydrocarbon cracking raw materials are subjected to high-temperature cracking to produce cracking gas, and the cracking gas enters the depropanizer for light and heavy component separation after the pre-processing steps such as quenching, compression, alkali washing, and drying, and the light component carbon 2-carbon 3 fraction is extracted from the top of the depropanizer. The hydrocarbon cracking raw materials are subjected to high-temperature cracking to produce cracking gas, and the cracking gas mixture enters the depropanizer for light and heavy component separation after the pre-processing steps such as quenching, compression, alkali washing, and drying. Preferably, before the cracking gas enters the depropanizer for light and heavy component separation, the cracking raw materials are subjected to arsenic removal treatment so that the cracking raw materials do not contain arsenic. Depending on the source of the cracking raw materials, a dechlorination treatment process can also be set. After various necessary treatment processes such as dearsenicization and dechlorination, the cracking raw materials enter the cracking furnace for high-temperature cracking, and the cracking raw materials will not damage the cracking furnace, and the cracking gas will not damage various hydrogenation catalysts used in the subsequent separation process, especially acetylene, propyne, and propadiene hydrogenation catalysts. Steam cracking raw materials generally include various hydrocarbons or mixed hydrocarbons such as naphtha, hydrogenated tail oil, and light hydrocarbons. In addition to the steam cracking process, the cracking gas obtained by catalytic cracking is also suitable for the cracking gas and its composition described in the present invention. The present invention does not impose any restrictions on the source of the cracking gas.

[0015] The composition of the cracked gas after cracking of different cracking raw materials will change. For example, compared with naphtha or heavier hydrocarbons, a higher concentration of light hydrocarbon cracking raw materials can produce cracked gas with a higher concentration of hydrogen and a lower concentration of carbon monoxide. Changing the cracking process conditions, such as changing the cracking temperature and cracking depth, will affect the product distribution of the cracking reaction and change the content of key components such as hydrogen, carbon monoxide, and acetylene in the cracked gas. After the cracking furnace has been running for a period of time, the coke produced by the cracking of hydrocarbons is deposited on the wall of the furnace tube, affecting heat transfer, increasing the system pressure, and even blocking the pipeline, so regular decoking is required. The furnace can be shut down for decoking, cutting off the feed and outlet cracking gas of the cracking furnace, or online decoking can be used, switching between different raw materials during decoking. The shutdown and charging of the cracking furnace, as well as the switching of cracking raw materials will cause changes in the content of hydrogen or carbon monoxide in the cracked gas, causing fluctuations in the carbon two hydrogenation reaction system.

[0016] In order to reduce the coking of the cracking furnace, it is often used to add coking inhibitors to the cracking raw materials. There are many types of coking inhibitors, such as sulfur-containing compounds such as mercaptans, dimethyl disulfide, diphenyl disulfide, etc. These operations can also control the carbon monoxide content in the cracking products. Carbon monoxide is a poison for carbon dihydrogenation catalysts. Controlling the sulfur content of the cracking furnace is conducive to properly controlling the reaction rate of the acetylene hydrogenation catalyst and preventing acetylene leakage or temperature runaway. General cracking raw materials such as naphtha contain sulfur, but some light cracking raw materials such as ethane, propane and other light hydrocarbons need to be appropriately injected with various organic sulfurs to inhibit the formation of carbon monoxide. The acetylene hydrogenation reactor will fluctuate before and after sulfur injection.

[0017] Usually, during the initial use of the acetylene hydrogenation catalyst, the activity of the fresh catalyst can be suppressed by directly injecting carbon monoxide into the cracking gas. Before the hydrogenation feed is transported to the catalytic hydrogenation reactor system, an appropriate amount of carbon monoxide can be added to the cracking gas. Oxygen-containing compounds such as methanol and ethanol can also be injected.

[0018] After the cracking raw materials are cracked, quenched, and compressed, the composition of the cracking gas is relatively complex, including useful components such as ethylene and propylene, as well as a small amount of H 2 S, CO 2 , H 2 O and other non-hydrocarbon impurities. These non-hydrocarbon impurities will not only reduce the quality of products such as ethylene and propylene, but also affect the normal separation process. In industry, ethanolamine can be used to absorb and remove most of the acidic gases in the cracking gas, and then sodium hydroxide solution can be used to remove a small amount of H 2 S and CO 2 , so that the acid gas content in the cracked gas meets the requirements. Molecular sieves are often used as adsorbents for cracked gas drying in industry. Molecular sieve adsorbents have the advantages of high dehydration efficiency and long service life, and are most widely used in industry. Molecular sieves can also be used to remove polar impurities such as methanol that may be contained in the cracked gas to prevent these impurities from reducing the performance of subsequent acetylene hydrogenation catalysts.

[0019] From the above, it can be seen that at least one of the following conditions changes, including: changes in the composition of the hydrocarbon cracking feedstock, changes in cracking conditions, and changes in pre-treatment conditions, causes the hydrogen and / or carbon monoxide content in the C2C3 fraction to change.

[0020] According to the preferred technical solution of the present invention, the carbon two carbon three fraction contains hydrogen, carbon monoxide, acetylene, ethylene, ethane, propylene, propane, methane, and at least one of optional propyne and propadiene. The light component carbon two carbon three fraction is extracted from the top of the depropanizer, mainly including hydrogen, carbon monoxide, acetylene, ethylene, ethane, propylene, propane, and a small amount of propyne, propadiene, etc. The carbon two carbon three fraction enters the catalytic hydrogenation reactor system for selective hydrogenation reaction. Usually, the process of removing hydrogen and carbon monoxide from the cracked gas after alkali washing without distillation separation, that is, hydrogenation to remove alkynes is called a pre-hydrogenation process. For the pre-hydrogenation process flow, since the raw material contains carbon monoxide, the selectivity of the catalytic hydrogenation reaction system is higher, and the catalyst can usually be used for one maintenance cycle, no spare catalyst is set, and no regeneration facilities are equipped. However, there is a risk of temperature runaway or alkyne leakage in the pre-hydrogenation process flow, and there is only one control means for the inlet temperature. Changes in the content of hydrogen or carbon monoxide have a greater impact on the catalytic hydrogenation reactor system. Compared with the pre-hydrogenation process, the process of first separating the light fractions such as hydrogen and methane contained in the cracked gas and then hydrogenating the separated C2 and C3 fractions is called the post-hydrogenation process. The amount of hydrogen in the C2 post-hydrogenation process is quantitatively added according to the amount of acetylene in the feed, and can be adjusted according to actual conditions. The operation is controllable and there are many adjustment methods; however, the overall selectivity of the post-hydrogenation process is not high, and the catalyst needs to be switched and regenerated regularly.

[0021] According to a more preferred technical solution of the present invention, the volume content of acetylene in the carbon 2-carbon 3 fraction is 200-10000ppmv, the volume content of propyne and propadiene is 200-10000ppmv, the volume content of hydrogen is 5%-30%, and the volume content of carbon monoxide is 200-5000ppmv. In the pre-hydrogenation process, the volume content of acetylene in the carbon 2-carbon 3 fraction extracted from the top of the depropanizer tower is about 200-10000ppmv, the volume content of propyne and propadiene is about 2000-10000ppmv, the volume content of hydrogen is about 5%-30%, the volume content of carbon monoxide is about 200-5000ppmv, and it also contains more methane, ethylene, propylene, ethane and a small amount of propane. The presence of highly unsaturated hydrocarbons acetylene, propyne and propadiene will reduce the activity of the polymerization catalyst, increase the consumption of the polymerization catalyst, and deteriorate the properties of the polymer. Industrial production requires that the content of alkynes and dienes in polymerization-grade ethylene and polymerization-grade propylene be less than 2 ppmv; in the production of low-pressure polyethylene, the content of acetylene in ethylene is required to be less than 0.1 ppmv. The method of catalytic selective hydrogenation of the C2-C3 fraction extracted from the top of the depropanizer has the advantages of simple process flow, low energy consumption, and no environmental pollution. In the catalytic hydrogenation reactor system, all acetylene can be removed to obtain polymerization-grade ethylene, and part of propyne and propadiene can be removed to reduce the hydrogenation load in the subsequent C3 hydrogenation reactor system.

[0022] In the existing pre-hydrogenation process, when the feed of the catalytic hydrogenation reactor is determined, the reactor inlet temperature is the only means of adjustment. By adjusting the inlet temperature of each section of the reactor system, the conversion rate and selectivity of the multi-stage reactor can be changed. Generally, the reaction temperature conditions of the catalyst are determined by comprehensive judgment based on the performance of the catalyst itself, the operating time, and the raw material conditions.

[0023] Hydrocarbon cracking feedstocks usually include various hydrocarbons or mixtures such as naphtha, hydrogenated tail oil, and light hydrocarbons. In the original design of the ethylene production unit, the catalytic hydrogenation reactor system operates under relatively stable feedstock conditions, and the concentration of hydrogen or carbon monoxide in the cracking gas changes very little. However, affected by the supply of hydrocarbon feedstocks in the market, or by production changes in upstream refineries, the raw materials introduced into the cracking section may change frequently, as well as changes in cracking process conditions, switching operations of cracking furnaces, etc., which ultimately lead to changes in the concentration of hydrogen or carbon monoxide entering the catalytic hydrogenation reaction system, which is no longer consistent with the original design.

[0024] When the cracking feedstock is switched from heavier hydrocarbon feedstock to lighter hydrocarbon feedstock, the hydrogen concentration in the cracking gas will increase. The increase in hydrogen concentration in the cracking gas will lead to a decrease in the ethylene selectivity of the acetylene hydrogenation reaction at a constant inlet temperature. The rapid increase in olefin hydrogenation will lead to the possibility of temperature runaway in the catalytic hydrogenation reaction system. By increasing the carbon monoxide concentration in the cracking gas to suppress the activity of the catalyst and reduce the ability to hydrogenate olefins, the risk of temperature runaway in the acetylene hydrogenation reaction system can be reduced. Conversely, when the cracking feedstock is switched from lighter hydrocarbon feedstock to heavier hydrocarbon feedstock, the hydrogen concentration in the cracking gas will decrease. The decrease in hydrogen concentration in the cracking gas will lead to a decrease in the acetylene conversion rate of the acetylene hydrogenation reaction at a constant inlet temperature, and there is a risk of acetylene leakage, resulting in unqualified ethylene products. By increasing the hydrogen concentration in the cracking gas to increase the activity of the catalyst, the risk of acetylene leakage can be reduced and the stable operation of the carbon two hydrogenation reaction system can be maintained.

[0025] Similarly, when the carbon monoxide concentration in the cracking gas increases, the acetylene conversion rate of the acetylene hydrogenation reaction at a constant inlet temperature will decrease, and there will be a risk of acetylene leakage, resulting in unqualified ethylene products. By increasing the hydrogen concentration in the cracking gas to improve the activity of the catalyst, the risk of acetylene leakage can be reduced and the stable operation of the carbon two hydrogenation reaction system can be maintained. Conversely, when the carbon monoxide concentration in the cracking gas decreases, the ethylene selectivity of the acetylene hydrogenation reaction at a constant inlet temperature will decrease, and the rapid increase in olefin hydrogenation will cause the acetylene hydrogenation reaction system to have a risk of temperature runaway. By increasing the carbon monoxide concentration in the cracking gas to improve the selectivity of the catalyst and reduce the ability to hydrogenate olefins, the risk of temperature runaway in the acetylene hydrogenation reaction system can be reduced and the operation can be maintained stable.

[0026] Hydrogen and carbon monoxide are the two most critical parameters that affect the stable operation of the pre-depropanization pre-hydrogenation reaction system. The use of fast gas chromatography can quickly and accurately determine the hydrogen and carbon monoxide content in the carbon 2 carbon 3 fraction, as well as the hydrogen and carbon monoxide content in the hydrogenation inlet material, so as to adjust the amount of controllably added hydrogen or carbon monoxide. Adjusting the content of hydrogen or carbon monoxide in the carbon 2 carbon 3 fraction can be achieved by increasing or decreasing the flow rate of controllably added crude hydrogen or dry hydrogen. The controllably added crude hydrogen or dry hydrogen becomes an adjustment means for the selective hydrogenation reactor system, and is no longer limited to only the adjustment means of the hydrogenation reactor inlet temperature. The controllably added crude hydrogen consists of about 80% to 100% volume content of hydrogen, 500 to 20000 ppmv of carbon monoxide, and balance methane, etc. The controllably added dry hydrogen consists of about 80% to 100% volume content of hydrogen, and balance methane, etc. Crude hydrogen and dry hydrogen are mainly produced by the ethylene plant, and can also be introduced from outside the plant. In the ethylene plant, crude hydrogen is generally removed by methanation reaction until the carbon monoxide content is less than 5ppmv to become dry hydrogen. Low-temperature methanation catalysts are usually used, and medium-high temperature or high-temperature methanation catalysts can also be used.

[0027] According to a preferred technical solution of the present invention, the input of crude hydrogen and / or dry hydrogen is adjusted according to the following changes in the hydrogen and / or carbon monoxide content in the C2C3 fraction:

[0028] (1) for every 5% increase in the volume content of hydrogen in the C2C3 fraction, crude hydrogen is introduced into the C2C3 fraction, so that the volume content of carbon monoxide in the hydrogenated material increases by 0 to 200 ppmv, preferably by 50 to 150 ppmv, compared with the C2C3 fraction;

[0029] (2) for every 200 ppmv increase in the carbon monoxide content in the C2C3 fraction, dry hydrogen is introduced into the C2C3 fraction so that the hydrogen content of the hydrogenated material increases by 0 to 5% by volume, preferably by 2 to 4% by volume, compared with the hydrogen content in the C2C3 fraction;

[0030] (3) When the hydrogen content in the C2C3 fraction is reduced, dry hydrogen is introduced into the C2C3 fraction to supplement the hydrogenated material with 50% to 150% of the reduced amount of hydrogen;

[0031] (4) when the carbon monoxide content in the C2C3 fraction is reduced, crude hydrogen is introduced into the C2C3 fraction so that 50% to 150% of the reduced amount of carbon monoxide is supplemented in the hydrogenated material;

[0032] (5) When the content of one of carbon monoxide and hydrogen in the C2C3 fraction increases and the content of the other decreases, firstly make adjustments according to (1) or (2) based on the increased content, then calculate the decrease in the decreased content and make adjustments according to (3) or (4).

[0033] According to a preferred technical solution of the present invention, the volume content of hydrogen in the hydrogenation material is 5% to 30%, and the volume content of carbon monoxide is 200 to 5000 ppmv.

[0034] According to a preferred technical solution of the present invention, the change in the content of hydrogen and / or carbon monoxide in the C2C3 fraction is determined by monitoring the content of hydrogen and / or carbon monoxide in the C2C3 fraction; and / or,

[0035] The change in the content of hydrogen and / or carbon monoxide in the hydrogenated material is determined by monitoring the content of hydrogen and / or carbon monoxide in the hydrogenated material, preferably monitoring the content of hydrogen and / or carbon monoxide at the inlet of the reactor.

[0036] By the method of the present invention, the catalytic hydrogenation reactor system can be operated at a substantially stable reaction temperature. The reaction temperature is controlled by increasing or decreasing the temperature of the hydrogenation inlet material in the C2C3 fraction heat exchange unit before contacting the catalytic hydrogenation catalyst.

[0037] Catalysts all have corresponding temperature ranges, and the reaction temperature range of catalysts is between the qualified temperature and the runaway temperature. The qualified temperature is the temperature of acetylene at the outlet of the catalytic hydrogenation reactor system at the qualified index. After passing through the catalytic hydrogenation reactor system, the acetylene content in the reaction effluent exceeds the specifications of the product ethylene. For example, when the acetylene content in the reaction effluent exceeds 2ppmv, it no longer meets the specification requirements of the ethylene product. In this case, it is called acetylene leakage. The runaway temperature is the temperature at which ethylene reacts rapidly in the catalytic hydrogenation reactor system. The situation in which the bed temperature increases rapidly and cannot be stabilized and controlled is called runaway. During runaway, a large amount of hydrogenation reaction occurs on the catalyst, and the reaction heat cannot be removed in time. Rapid cooling is required to suppress the reaction.

[0038] The inlet temperature is controlled according to the hydrogen or carbon monoxide content in the hydrogenation inlet material, and the inlet temperature is adjusted according to the catalyst operation time and the ethylene selectivity. The inlet temperature also depends on the flow rate of the hydrogenation inlet material, the inlet acetylene concentration, the presence of pollutants or poisons, and the performance of the hydrogenation catalyst itself.

[0039] Control the temperature of the hydrogenation inlet material to reduce or prevent temperature runaway or acetylene leakage. In the C2C3 fraction heat exchange unit, the temperature of the hydrogenation inlet material is controlled by adjusting the flow of the heating or cooling medium of the heat exchanger, adjusting the flow of the bypass of the heat exchange unit, and other means. All existing adjustment methods are applicable to the present invention.

[0040] According to a preferred technical solution of the present invention, the temperature of the hydrogenated material is adjusted according to the content of hydrogen and / or carbon monoxide in the hydrogenated material; preferably, the temperature of the hydrogenated material is adjusted by heat exchange.

[0041] According to a more preferred technical solution of the present invention, the temperature of the hydrogenated material is reduced by 0 to 4°C, preferably 1 to 3°C, for every 5% increase in the volume content of the hydrogen in the hydrogenated material;

[0042] For every 5% volumetric decrease in the hydrogen content in the hydrogenated material, the temperature of the hydrogenated material increases by 0-4°C, preferably 1-3°C.

[0043] According to a more preferred technical solution of the present invention, the temperature of the hydrogenated material increases by 0 to 2°C, preferably 0.5 to 1.5°C, for every 100 ppmv increase in the carbon monoxide content in the hydrogenated material;

[0044] For every 100 ppmv decrease in the carbon monoxide content in the hydrogenated material, the temperature of the hydrogenated material is reduced by 0-2°C, preferably 0.5-1.5°C.

[0045] By adopting the above method, the catalytic hydrogenation reactor system has a variety of controllable operating conditions, has high ethylene selectivity and operating stability, and has neither temperature runaway nor alkyne leakage. By adopting the method of the present invention, a stable concentration of hydrogen or carbon monoxide in the hydrogenation inlet material can be obtained in time. The control means of the catalytic hydrogenation reactor system is increased from a single reaction inlet temperature control to hydrogen concentration, carbon monoxide concentration, and inlet temperature control.

[0046] The process flow of pre-hydrogenation of C2 usually adopts one or more stages of hydrogenation, and can adopt the reaction type of isothermal bed or adiabatic bed, and the number of reactor stages or heat exchange types can be arbitrarily combined. Reasonable control of the acetylene conversion rate of each stage in the multi-stage hydrogenation can obtain better ethylene selectivity and operation cycle, and the acetylene conversion rate in the first hydrogenation reaction bed is usually controlled at 25% to 70%. Under the condition that the acetylene content in the C2C3 fraction is lower than 0.3%, one-stage hydrogenation can be adopted, and the acetylene conversion rate reaches 100%. For the pre-depropanization pre-hydrogenation process, wherein the C2C3 fraction also includes methylacetylene and propadiene, the conversion rate of methylacetylene and propadiene in the hydrogenation reaction system is about 20% to 100%, and the preferred conversion rate of methylacetylene and propadiene in the hydrogenation reaction system is about 40% to 90%. According to the preferred technical scheme of the present invention, when the acetylene content in the C2C3 fraction is lower than 0.3% by volume, one-stage hydrogenation is adopted;

[0047] When the acetylene content in the C2C3 fraction is higher than 0.3% by volume, the method comprises a first stage hydrogenation and at least one stage hydrogenation downstream of the first stage hydrogenation, wherein the acetylene conversion rate after the first stage hydrogenation reaction is between 25% and 70%; and / or, after the methylacetylene and propadiene contained in the hydrogenated material are subjected to hydrogenation reaction, the conversion rate of methylacetylene and propadiene in the hydrogenation effluent is between 20% and 100%, preferably between 40% and 90%.

[0048] According to the preferred technical solution of the present invention, the conditions of the hydrogenation reaction include: the hydrogenation reaction temperature is 20-120°C, and / or the reaction pressure is 1.0-4.0 MPa, and / or the catalyst gas phase volume space velocity is 2000-20000h -1 and / or,

[0049] The acetylene content in the hydrogenation effluent is less than or equal to 5 ppmv, preferably less than or equal to 2 ppmv, more preferably less than or equal to 0.5 ppmv, most preferably less than or equal to 0.1 ppmv.

[0050] According to the preferred technical solution of the present invention, the catalytic hydrogenation catalyst includes an active component, an auxiliary agent and a carrier, wherein the active component is a metal element of Group VIIIB, preferably at least one of Pd, Ru and Rh, and / or the active component is 0.003% to 0.3% of the total weight of the carrier in terms of the weight of the metal element; the auxiliary active component is one or more of Ag, Bi, Ga, K, La, F, In, Ni, Pt, Pb, Zn, Fe, Si, Ce and Sn; and / or the carrier is an inorganic carrier, preferably at least one of alumina, silicon oxide and activated carbon. The adsorption capacity of acetylene, propyne and propadiene on these catalysts is stronger than that of ethylene and propylene, and selective hydrogenation can be performed to generate more ethylene and propylene, and less ethane, propane and oligomers. The commercial pre-depropanization pre-hydrogenation catalyst BC-H-21 (composed of Pd-auxiliary agent / alumina) can be used.

[0051] The second aspect of the present invention is to provide a method for producing olefins by cracking and separating hydrocarbon raw materials, comprising:

[0052] The hydrocarbon cracking feedstock is cracked to produce cracking gas, which is subjected to a pre-processing step, including cooling, compression, alkali washing, and drying, and then enters a depropanizer to separate light and heavy components; the light component is extracted from the top of the depropanizer to obtain a C2C3 fraction, and the C2C3 fraction is subjected to a hydrogenation reaction using the selective hydrogenation method described in the first aspect to obtain a hydrogenation effluent.

[0053] As mentioned above, the hydrocarbon cracking feedstock includes at least one hydrocarbon or a mixture of naphtha, hydrogenated tail oil, and light hydrocarbons.

[0054] At least one of the following conditions is changed, including: a change in the composition of the hydrocarbon cracking feedstock, a change in the cracking conditions, and a change in the pre-processing conditions, so that the content of hydrogen and / or carbon monoxide in the C2C3 fraction changes.

[0055] By adopting the above method, the catalytic hydrogenation reactor system has a variety of controllable operating conditions, high ethylene selectivity and operating stability, and neither temperature runaway nor acetylene leakage.

[0056] Compared with the prior art, the advantages of the present invention are:

[0057] With respect to pre-depropanization and pre-hydrogenation, the present invention adopts controllable crude hydrogen and / or dry hydrogen as a control means to cope with changes in the hydrogen and / or carbon monoxide content in the C2C3 fraction, thereby improving ethylene selectivity and operational stability without temperature runaway or acetylene leakage.

[0058] The control method of the present invention is more direct and targeted, and has the advantages of fast response, simplicity, directness, stability and controllability. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The accompanying drawings are used to further understand the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation of the present invention.

[0060] Attached Figure 1 :A controllable selective hydrogenation method for polyunsaturated hydrocarbons. The process diagram schematically describes the process of producing olefins from hydrocarbon feedstocks through a cracking and separation process. It includes: 1 cracking feedstock; 2 hydrocarbon cracking unit; 3 cracking gas; 4 depropanizer feed; 5 depropanizer; 6 C2C3 fraction; 7 C4 and above fraction; 8 heat exchange unit; 9 hydrogenation inlet material; 10 catalytic hydrogenation reactor system; 11 hydrogenation effluent; 20 crude hydrogen; 30 dry hydrogen.

[0061] The hydrocarbon cracking feedstock 1 can be any hydrocarbon, which can be a light hydrocarbon feedstock or a heavy hydrocarbon feedstock, including ethane, propane, butane, naphtha, diesel, etc. The hydrocarbon cracking feedstock 1 is operated in the cracking unit 2 at a certain temperature, pressure, and space velocity to produce cracking gas 3. The cracking gas 3 includes one or more cracking products, such as but not limited to ethylene, propylene, butene, ethane, propane, hydrogen, carbon monoxide, acetylene, methylacetylene, propadiene, methane, acidic gas, etc. The cracking gas 3 is subjected to a heat recovery cooling process in a quenching unit and steam and heavy hydrocarbon components are removed, and then the acidic gas is removed by compression, alkali washing or amine washing, and then enters the subsequent separation system after drying. The tower feed mixture 4 is distilled and separated in the front depropanizer 5, and the light component carbon 2 carbon 3 fraction 6 is produced from the top of the tower, and the heavy components 7 of carbon 4 and above carbon 4 are produced from the bottom of the tower. The carbon 2 carbon 3 fraction 6 at the top of the tower is adjusted in temperature by the heat exchange unit 8 and enters the catalytic hydrogenation reactor system 10 for hydrogenation and deacetylation reaction. The hydrogenation inlet material 9 includes hydrogen, carbon monoxide, acetylene, methylacetylene, propadiene, ethylene, propylene, and saturated hydrocarbons of C2C3. Under the action of the catalytic hydrogenation catalyst, all the acetylene in the hydrogenation feed is hydrogenated, and methylacetylene and propadiene are partially hydrogenated to generate hydrogenation effluent 11, which enters the ethylene distillation system to obtain ethylene products. Crude hydrogen 20 or dry hydrogen 30 is mainly used to adjust the hydrogen or carbon monoxide content in the C2C3 fraction 6.

[0062] The catalytic hydrogenation reactor system 10 includes one or more hydrogenation reactors. The catalytic hydrogenation reactor system 10 can use any known catalyst for selective hydrogenation of acetylene, which is widely available. The catalytic hydrogenation reactor system 10 also includes one or more analyzers, such as a gas chromatograph, to measure the hydrogen concentration and carbon monoxide concentration in the carbon 2-carbon 3 fraction 6 and the hydrogenation inlet material 9, and can also measure the concentrations of various components such as acetylene, ethylene, and propylene. The acetylene hydrogenation reaction must be carried out within a reasonable temperature window, and neither acetylene leakage nor temperature runaway occurs. The only adjustment method in the past was to adjust the reaction temperature of the hydrogenation inlet material 9. The present invention changes the hydrogen or carbon monoxide concentration in the hydrogenation inlet material 9 by adjusting the flow rate of crude hydrogen 20 and dry hydrogen 30. The operating performance of the catalytic hydrogenation reactor system 10 can be adjusted by adjusting the temperature, carbon monoxide concentration, and hydrogen concentration in the catalytic hydrogenation reactor system 10. DETAILED DESCRIPTION

[0063] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0064] In the present invention, the method for detecting the specific composition of the hydrogenation feedstock and the hydrogenation effluent is: using FID and TCD detectors, and adopting an external standard method or area normalization to analyze the composition.

[0065] The calculation method of acetylene conversion is:

[0066]

[0067] The ethylene selectivity is calculated as:

[0068]

[0069] The conversion of propyne and propadiene is calculated as follows:

[0070]

[0071] In the following examples, the gas phase space velocity is the volume space velocity; and the reaction pressure is the gauge pressure.

[0072] Comparative Example 1:

[0073] The hydrogenation feedstock ( Figure 1The feed mixture 4 is distilled and separated in the front depropanizer 5, and the light component C2C3 fraction 6 is taken out from the top of the tower and contacts with the BC-H-21 hydrogenation catalyst (composed of Pd-promoter / alumina) in the fixed bed reactor at a gas phase volume space velocity of 10000h -1 , the reaction pressure is 3.5MPa gauge pressure. The volume composition of key components hydrogen, carbon monoxide, acetylene, ethylene, propyne and propadiene is as follows, wherein the inlet acetylene content is 4000ppmv, the inlet propyne and propadiene content is 5000ppmv, and the inlet ethylene volume content is 38%. The temperature of hydrogenation inlet material 9 is 60 degrees. Under such conditions, the acetylene conversion rate is 100%, the ethylene selectivity is 70%, and the MAPD (propyne and propadiene) conversion rate is 40%.

[0074] The hydrogenation feedstocks in the embodiments and comparative examples of the present invention are all from Figure 1 The feed mixture 4 is rectified and separated in the front depropanizer 5, and the light component C2C3 fraction 6, that is, all C2C3 fraction 6, is extracted from the top of the tower, and the specific composition is:

[0075] The hydrogen content is 16%, the carbon monoxide content is 1000 ppmv, the methane content is 24%, the ethane content is 6%, the ethylene content is 38%, the acetylene content is 0.4%, the propane content is 2%, the propylene content is 13%, and the propyne and propadiene content are 0.5%.

[0076] Comparative Example 2:

[0077] The hydrogenation feedstock including hydrogen, carbon monoxide, ethylene, ethane, acetylene, propylene, propane, propyne and propadiene is contacted with a BC-H-21 hydrogenation catalyst (composed of Pd-promoter / alumina) in a fixed bed reactor at a gas phase volume space velocity of 10000 h -1 , the reaction pressure is 3.5MPa. The volume composition of key components hydrogen, carbon monoxide, acetylene, ethylene, propyne and propadiene is shown in Table 1, wherein the inlet acetylene content is 4000ppmv, the inlet propyne and propadiene content is 5000ppmv, and the inlet ethylene volume content is 38%. When the hydrogen content is 10% higher than that of Comparative Example 1 and the contents of other key components are substantially unchanged, in order to prevent hydrogen from rapidly increasing the ethylene reaction and causing the reactor to overheat, the catalyst performance in the case of Comparative Example 1 is substantially maintained by lowering the reaction temperature to 50 degrees.

[0078] Embodiment 1:

[0079] The hydrogenation feedstock including hydrogen, carbon monoxide, ethylene, ethane, acetylene, propylene, propane, propyne and propadiene is contacted with a BC-H-21 hydrogenation catalyst (composed of Pd-promoter / alumina) in a fixed bed reactor at a gas phase volume space velocity of 10000 h -1, the reaction pressure is 3.5MPa. The volume composition of key components hydrogen, carbon monoxide, acetylene, ethylene, propyne and propadiene is as shown in Table 1, wherein the inlet acetylene content is 4000ppmv, the inlet propyne and propadiene content is 5000ppmv, and the inlet ethylene volume content is 38%. When the hydrogen content in the hydrogenation inlet material increases by 10%, the content of other key components does not change substantially. In order to avoid reactor temperature runaway and maintain good catalytic performance, the inlet temperature is reduced in small amounts, and the crude hydrogen flow in the crude hydrogen 20 is increased, and the carbon monoxide volume content in the crude hydrogen 20 used is 3000ppmv. By adopting this operation, it is possible to avoid temperature runaway, while improving ethylene selectivity, improving propyne and propadiene conversion, and maintaining complete conversion of acetylene.

[0080] Embodiment 2:

[0081] The hydrogenation feedstock including hydrogen, carbon monoxide, ethylene, ethane, acetylene, propylene, propane, propyne and propadiene is contacted with a BC-H-21 hydrogenation catalyst (composed of Pd-promoter / alumina) in a fixed bed reactor at a gas phase volume space velocity of 10000 h -1 , the reaction pressure is 3.5MPa. The volume composition of key components hydrogen, carbon monoxide, acetylene, ethylene, propyne and propadiene is as shown in Table 1, wherein the inlet acetylene content is 4000ppmv, the inlet propyne and propadiene content is 5000ppmv, and the inlet ethylene volume content is 38%. When the hydrogen content in the hydrogenation inlet material is reduced by 10%, the content of other key components does not change substantially. In order to avoid acetylene leakage in the reactor, the feed inlet temperature is increased in small amounts, and the hydrogen flow in the dry hydrogen 30 is increased. The volume content of hydrogen in the dry hydrogen is 95%, and the volume content of methane is 5%. By adopting this operation, the complete conversion of acetylene can be maintained, and the temperature runaway can be avoided. The conversion rate of propyne and propadiene can also be increased, and the ethylene selectivity is slightly increased.

[0082] Comparative Example 3:

[0083] The hydrogenation feedstock including hydrogen, carbon monoxide, ethylene, ethane, acetylene, propylene, propane, propyne and propadiene is contacted with a BC-H-21 hydrogenation catalyst (composed of Pd-promoter / alumina) in a fixed bed reactor at a gas phase volume space velocity of 10000 h -1 , reaction pressure is 3.5MPa.The volume composition of key components hydrogen, carbon monoxide, acetylene, ethylene, propyne and propadiene is as shown in Table 1, wherein, the inlet acetylene content is 4000ppmv, the inlet propyne and propadiene content is 5000ppmv, and the inlet ethylene volume content is 38%.Wherein the carbon monoxide content is 500ppmv higher than Comparative Example 1, and the contents of other key components do not change substantially.In order to prevent the reactor from leaking acetylene, by raising the reaction temperature to 65 degrees, the catalyst performance under the situation of Comparative Example 1 is substantially maintained.

[0084] Embodiment 3:

[0085] The hydrogenation feedstock including hydrogen, carbon monoxide, ethylene, ethane, acetylene, propylene, propane, propyne and propadiene is contacted with a BC-H-21 hydrogenation catalyst (composed of Pd-promoter / alumina) in a fixed bed reactor at a gas phase space velocity of 10000 h -1 , the reaction pressure is 3.5MPa. The volume composition of key components hydrogen, carbon monoxide, acetylene, ethylene, propyne and propadiene is as shown in Table 1, wherein the inlet acetylene content is 4000ppmv, the inlet propyne and propadiene content is 5000ppmv, and the inlet ethylene volume content is 38%. When the carbon monoxide content in the hydrogenation inlet material increases by 500ppmv, the content of other key components does not change substantially. In order to prevent the reactor from leaking acetylene, the reaction temperature is increased to 62 degrees in small amounts, and the hydrogen flow in the dry hydrogen 30 is increased. The volume content of hydrogen in the dry hydrogen is 95%, and the volume content of methane is 5%. Adopting this operation, it can be ensured that acetylene is fully converted while improving ethylene selectivity.

[0086] Embodiment 4:

[0087] The hydrogenation feedstock including hydrogen, carbon monoxide, ethylene, ethane, acetylene, propylene, propane, propyne and propadiene is contacted with a BC-H-21 hydrogenation catalyst (composed of Pd-promoter / alumina) in a fixed bed reactor at a gas phase space velocity of 10000 h -1 , reaction pressure is 3.5MPa.The volume composition of key components hydrogen, carbon monoxide, acetylene, ethylene, propyne and propadiene is as shown in Table 1, wherein, inlet acetylene content is 4000ppmv, inlet propyne and propadiene content is 5000ppmv, and inlet ethylene volume content is 38%.When the carbon monoxide content in the hydrogenation inlet material is reduced by 500ppmv, the content of other key components does not change substantially.In order to avoid the reactor temperature flying, and maintain good catalytic performance, the inlet temperature is reduced in a small amount, and the crude hydrogen flow in the crude hydrogen 20 is increased, and the carbon monoxide volume content in the crude hydrogen 20 adopted is 3000ppmv.Adopt this operation, can improve ethylene selectivity, improve propyne and propadiene conversion, maintain acetylene complete conversion simultaneously.

[0088] Example 5

[0089] The hydrogenation feedstock including hydrogen, carbon monoxide, ethylene, ethane, acetylene, propylene, propane, propyne and propadiene is contacted with a BC-H-21 hydrogenation catalyst (composed of Pd-promoter / alumina) in a fixed bed reactor at a gas phase space velocity of 10000 h -1, the reaction pressure is 3.5MPa. The volume composition of key components hydrogen, carbon monoxide, acetylene, ethylene, propyne and propadiene is as shown in Table 1, wherein the inlet acetylene content is 4000ppmv, the inlet propyne and propadiene content is 5000ppmv, and the inlet ethylene volume content is 38%. When the carbon monoxide content in the hydrogenation inlet material increases by 300ppmv, the content of hydrogen decreases by 5%, and the content of other key components does not change substantially. In order to prevent the reactor from leaking acetylene, the hydrogen flow in the dry hydrogen 30 needs to be increased, and the reaction temperature is increased to 62 degrees by a small amount. The volume content of hydrogen in the dry hydrogen is 95%, and the volume content of methane is 5%. Adopting this operation, it can ensure that acetylene is fully converted, avoid temperature runaway, and improve ethylene selectivity at the same time.

[0090] Example 6

[0091] The hydrogenation feedstock including hydrogen, carbon monoxide, ethylene, ethane, acetylene, propylene, propane, propyne and propadiene is contacted with a BC-H-21 hydrogenation catalyst (composed of Pd-promoter / alumina) in a fixed bed reactor at a gas phase space velocity of 10000 h -1 , the reaction pressure is 3.5MPa. The volume composition of key components hydrogen, carbon monoxide, acetylene, ethylene, propyne and propadiene is as shown in Table 1, wherein the inlet acetylene content is 4000ppmv, the inlet propyne and propadiene content is 5000ppmv, and the inlet ethylene volume content is 38%. When the carbon monoxide content in the hydrogenation inlet material is reduced by 300ppmv and the hydrogen content is increased by 5%, the content of other key components does not change substantially. In order to avoid the reactor temperature runaway and maintain good catalytic performance, the inlet temperature is reduced in small amounts, and the crude hydrogen flow in the crude hydrogen 20 is increased, and the carbon monoxide volume content in the crude hydrogen 20 used is 3000ppmv. By adopting this operation, it is possible to improve ethylene selectivity, avoid temperature runaway, improve propyne and propadiene conversion, and maintain complete conversion of acetylene.

[0092] Table 1: Comparative Examples and Examples

[0093]

[0094]

[0095] Table 2

[0096]

[0097] As can be seen from Tables 1 and 2, by adopting the technical solution of the present invention, the ethylene selectivity and operational stability can be improved by adjusting the controllable introduction of crude hydrogen and / or dry hydrogen, ensuring that the outlet acetylene hydrogenation is qualified and avoiding the occurrence of temperature runaway.

[0098] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0099] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0100] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for selective hydrogenation of polyunsaturated hydrocarbons, the method comprising: Using the C2C3 fraction extracted from the top of a depropanizer as a hydrogenation material raw material, and inputting crude hydrogen and / or dry hydrogen into the C2C3 fraction before entering a hydrogenation reactor according to changes in the hydrogen and / or carbon monoxide content in the C2C3 fraction, to obtain a hydrogenation material with hydrogen and / or carbon monoxide content within a target range; The hydrogenated material is contacted with a catalytic hydrogenation catalyst to perform a hydrogenation reaction, and the acetylene in the hydrogenated material is subjected to a hydrogenation reaction to produce a hydrogenation effluent; The crude hydrogen contains 80% to 100% by volume of hydrogen, 500 to 20,000 ppmv of carbon monoxide, and a balance gas; The dry hydrogen contains 80% to 100% by volume of hydrogen and a balance of gas.

2. The selective hydrogenation method according to claim 1, characterized in that: The C2C3 fraction contains hydrogen, carbon monoxide, acetylene, ethylene, ethane, propylene, propane, methane, and optionally at least one of propyne and propadiene; preferably, The volume content of acetylene in the C2C3 fraction is 200-10000 ppmv, the volume content of propyne and propadiene is 200-10000 ppmv, the volume content of hydrogen is 5%-30%, and the volume content of carbon monoxide is 200-5000 ppmv.

3. The selective hydrogenation method according to claim 1, characterized in that: The input of crude hydrogen and / or dry hydrogen is adjusted according to the following changes in the hydrogen and / or carbon monoxide content in the C2C3 fraction: (1) for every 5% increase in the volume content of hydrogen in the C2C3 fraction, crude hydrogen is introduced into the C2C3 fraction, so that the volume content of carbon monoxide in the hydrogenated material increases by 0 to 200 ppmv, preferably by 50 to 150 ppmv, compared with the C2C3 fraction; (2) for every 200 ppmv increase in the carbon monoxide content in the C2C3 fraction, dry hydrogen is introduced into the C2C3 fraction so that the hydrogen content of the hydrogenated material increases by 0 to 5% by volume, preferably by 2 to 4% by volume, compared with the hydrogen content in the C2C3 fraction; (3) When the hydrogen content in the C2C3 fraction is reduced, dry hydrogen is introduced into the C2C3 fraction to supplement the hydrogenated material with 50% to 150% of the reduced amount of hydrogen; (4) when the carbon monoxide content in the C2C3 fraction is reduced, crude hydrogen is introduced into the C2C3 fraction so that 50% to 150% of the reduced amount of carbon monoxide is supplemented in the hydrogenated material; (5) When the content of one of carbon monoxide and hydrogen in the C2C3 fraction increases and the content of the other decreases, firstly make adjustments according to (1) or (2) based on the increased content, then calculate the decrease in the decreased content and make adjustments according to (3) or (4).

4. The selective hydrogenation method according to claim 1, characterized in that: The volume content of hydrogen in the hydrogenation material is 5% to 30%, and the volume content of carbon monoxide is 200 to 5000 ppmv.

5. The selective hydrogenation method according to claim 1, characterized in that: Determining the change in the content of hydrogen and / or carbon monoxide in the C2C3 fraction by monitoring the content of hydrogen and / or carbon monoxide in the C2C3 fraction; and / or, The change in the content of hydrogen and / or carbon monoxide in the hydrogenated material is determined by monitoring the content of hydrogen and / or carbon monoxide in the hydrogenated material, preferably monitoring the content of hydrogen and / or carbon monoxide at the reactor inlet.

6. The selective hydrogenation method according to claim 1, characterized in that: The temperature of the hydrogenated material is adjusted according to the content of hydrogen and / or carbon monoxide in the hydrogenated material; preferably, the temperature of the hydrogenated material is adjusted by heat exchange.

7. The selective hydrogenation method according to claim 6, characterized in that: For every 5% increase in the volume content of hydrogen in the hydrogenated material, the temperature of the hydrogenated material decreases by 0 to 4°C, preferably 1 to 3°C; For every 5% volumetric decrease in the hydrogen content in the hydrogenated material, the temperature of the hydrogenated material increases by 0-4°C, preferably 1-3°C.

8. The selective hydrogenation method according to claim 6, characterized in that: For every 100 ppmv increase in the carbon monoxide content in the hydrogenated material, the temperature of the hydrogenated material increases by 0 to 2°C, preferably 0.5 to 1.5°C; For every 100 ppmv decrease in the carbon monoxide content in the hydrogenated material, the temperature of the hydrogenated material is reduced by 0-2°C, preferably 0.5-1.5°C.

9. The selective hydrogenation method according to any one of claims 1 to 8, characterized in that: When the acetylene content in the C2C3 fraction is less than 0.3% by volume, one-stage hydrogenation is adopted; When the acetylene content in the C2C3 fraction is higher than 0.3% by volume, a first stage hydrogenation and at least one stage hydrogenation downstream of the first stage hydrogenation are included, wherein the acetylene conversion rate after the first stage hydrogenation reaction is between 25% and 70%; and / or, After the methylacetylene and propadiene contained in the hydrogenation material are subjected to hydrogenation reaction, the conversion rate of methylacetylene and propadiene in the hydrogenation effluent is 20% to 100%, preferably 40% to 90%.

10. The selective hydrogenation method according to any one of claims 1 to 8, characterized in that: The conditions of the hydrogenation reaction include: a hydrogenation reaction temperature of 20 to 120° C., and / or a reaction pressure of 1.0 to 4.0 MPa, and / or a catalyst gas phase volume space velocity of 2000 to 20000 h -1 and / or, The acetylene content in the hydrogenation effluent is less than or equal to 5 ppmv, preferably less than or equal to 2 ppmv, more preferably less than or equal to 0.5 ppmv, most preferably less than or equal to 0.1 ppmv.

11. The selective hydrogenation method according to any one of claims 1 to 8, characterized in that: The catalytic hydrogenation catalyst comprises an active component, a co-active agent and a carrier, wherein the active component is a metal element of Group VIIIB, preferably at least one of Pd, Ru and Rh, and / or the active component, calculated by weight of the metal element, is 0.003% to 0.3% of the total weight of the carrier; the co-active component is one or more of Ag, Bi, Ga, K, La, F, In, Ni, Pt, Pb, Zn, Fe, Si, Ce and Sn; and / or the carrier is an inorganic carrier, preferably at least one of alumina, silicon oxide and activated carbon.

12. A method for producing olefins by cracking and separating hydrocarbon raw materials, comprising: The hydrocarbon cracking feedstock is cracked to produce cracking gas, the cracking gas is subjected to a pre-processing step, the pre-processing step includes cooling, compression, alkali washing, and drying, and then enters a depropanizer to separate light and heavy components; the light component is extracted from the top of the depropanizer to obtain a carbon 2-carbon 3 fraction, and the carbon 2-carbon 3 fraction is subjected to a hydrogenation reaction using the selective hydrogenation method described in any one of claims 1 to 11 to obtain a hydrogenation effluent; Preferably, the hydrocarbon cracking feedstock comprises at least one hydrocarbon or a mixture of naphtha, hydrogenated tail oil, and light hydrocarbons; and / or, At least one of the following changes: Changes in the composition of hydrocarbon cracking feedstock, cracking conditions, and pre-treatment conditions result in changes in the content of hydrogen and / or carbon monoxide in the C2C3 fraction.

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