A system and process for comprehensive utilization of hydrogen in a cyclohexanone esterification device

Abstract

The present invention discloses a system and process for the comprehensive utilization of hydrogen within a cyclohexanone esterification process plant, including the comprehensive utilization of tail hydrogen emitted from a benzene selective hydrogenation unit, the hydrogen source and emitted hydrogen from a cyclohexyl acetate hydrogenation unit, the hydrogen source and emitted tail hydrogen from a cyclohexane hydrorefining unit, and by-product hydrogen from a cyclohexanol dehydrogenation reaction unit. A system for treating and utilizing hydrogen within the plant is invented. Taking into account the composition of each emitted hydrogen or by-product hydrogen, the system utilizes mature, conventional technologies for low-cost treatment of the emitted hydrogen or by-product hydrogen, rather than employing TSA and / or PSA methods. This system achieves cascaded utilization of hydrogen within the cyclohexanone plant, reduces the amount of discharged hydrogen processed and the loss of valuable materials, reduces the amount of new hydrogen added to the plant, and reduces the production cost of cyclohexanone esterification process, thus having industrial application value.

Description

Technical Field

[0001] The present invention relates to the technical field of petrochemical industry, and in particular to a system and a process for comprehensive utilization of hydrogen in a cyclohexanone esterification device. Background Art

[0002] Cyclohexanone is an important chemical raw material, serving as an intermediate in the production of adipic acid, caprolactam, as well as pharmaceuticals, coatings, and dyes. It also plays a crucial role in the coatings and textile industries. Currently, the main methods for producing cyclohexanone include cyclohexane oxidation, phenol hydrogenation, cyclohexene hydration, and the currently commercialized cyclohexene esterification method. Cyclohexane oxidation suffers from low conversion and selectivity, numerous side reactions, and poor safety. Phenol hydrogenation, on the other hand, suffers from high phenol costs, making it less economically competitive. Cyclohexene hydration can be divided into direct and indirect hydration methods. The direct hydration method, pioneered by Asahi Kasei Corporation in Japan, involves selective hydrogenation of benzene to produce cyclohexene and a small amount of cyclohexane. The cyclohexene then undergoes hydration over a molecular sieve catalyst to directly produce cyclohexanol, which is then dehydrogenated to produce cyclohexanone. This method produces high-quality products, high atomic utilization, and minimal waste. However, the single-pass conversion rate of the cyclohexene hydration reaction is approximately 10%, and the high water-to-olefin ratio requires extensive recycling, resulting in high investment and energy consumption. The indirect hydration method uses carboxylic acid as a medium to generate carboxylic acid esters, which are then hydrolyzed to produce cyclohexanol. This method has low conversion rate and selectivity and has not yet been applied industrially.

[0003] In recent years, domestic research institutes have been vigorously developing and improving the cyclohexene esterification method for producing cyclohexanol and / or cyclohexanone (referred to as "esterification method cyclohexanone"). Esterification method cyclohexanone is the latest production process. As a green and low-cost cyclohexanol production method, it has good raw material adaptability. The document "Y. Zhu, L. Gao, L. Wen, et al., Cyclohexene esterification–hydrogenation for efficient production of cyclohexanol [J]. Green Chem., 2021, 23, 1185-1192." introduced this. For example, patents CN103657658A, CN103664528A, CN103664529A, CN103664531A, CN103664586A, CN106349011A, CN107434760A, CN107519881A, CN112892581A, and CN113019391A introduce methods for producing cyclohexanol and / or cyclohexanone by the cyclohexene esterification method.

[0004] The cyclohexene esterification process for producing cyclohexanol involves three steps: selective hydrogenation of benzene, cyclohexene esterification, and cyclohexyl acetate hydrogenation. Benzene selective hydrogenation was successfully developed by Asahi Kasei in Japan and has been industrially applied for nearly 30 years. Cyclohexene and carboxylic acid undergo esterification to form esters, which are then hydrogenated to form alcohols. Both esterification and hydrogenation exhibit high conversion rates and selectivity. Patents CN104907071B and CN107434767A demonstrate cyclohexyl ester conversion rates exceeding 99% and cyclohexanol selectivity exceeding 99%. The process generates virtually no waste, boasts high atom economy, and operates under relatively mild reaction conditions. It typically uses inexpensive acetic acid as a raw material, and the co-production of high-value-added ethanol significantly enhances the economic competitiveness of this technology, offering promising prospects for industrialization. If cyclohexanone is the target product, the addition of a cyclohexanol dehydrogenation step to produce cyclohexanone is recommended.

[0005] The cyclohexene esterification process has the following disadvantages: long process, corrosion in the production process, high operating pressure, and high hydrogen consumption per unit product. The hydrogen consumption per ton of cyclohexanone is 920-980 Nm 3 There are many hydrogen units or systems involved, and the requirements for hydrogen quality and pressure are different for each system. The main process steps and hydrogen-related characteristics are as follows:

[0006] 1) Benzene selective hydrogenation to cyclohexene unit: hydrogen consumption per ton of product is about 660-690 Nm 3 , and has very strict requirements on hydrogen quality, especially harmful components such as sulfur, carbon monoxide, and nitrogen organic compounds. The unit is equipped with hydrogen and raw benzene refining facilities to re-refine the raw materials entering the reactor to reduce the impurity content, such as: sulfur content is less than 1ppb; hydrogenation adopts a one-way process, the hydrogenation temperature is medium, but the operating pressure is high (reaction temperature 120-150℃, reaction pressure 4.5-5.5MPa(G)), the benzene conversion rate is about 40-50%, the cyclohexene selectivity is about 75-80%, and cyclohexane is the main by-product; the hydrogenation reaction product is flashed at a pressure of 0.4-0.5MPa(G) into gas-liquid two phases, and the flash liquid is extracted and distilled to recover benzene, pure cyclohexene or / and a mixture of cyclohexene and cyclohexane, and the flash gas is cooled to about 15℃, and the gas-liquid separation is used to obtain tail hydrogen. The emission per ton of product is about 10-20Nm 3 The hydrogen content is about 95%, and other components include water, methane, nitrogen, benzene, cyclohexene and cyclohexane. The content of harmful impurities is extremely low; for the discharged tail hydrogen, some is sent to the factory fuel pipeline network, and some is sent to the hydrogen recovery device.

[0007] 2) Cyclohexene addition esterification unit: Using pure "cyclohexene or cyclohexene mixture" obtained by selective hydrogenation of benzene and acetic acid as raw materials, the cyclohexene addition esterification reaction produces cyclohexyl acetate. The reaction conditions are generally mild, and a series of reactors are used to achieve a high yield. The reaction product undergoes a series of separation and purification to recover acetic acid and cyclohexene, and separate cyclohexane to obtain the product cyclohexyl acetate. This unit does not involve hydrogen utilization.

[0008] 3) Cyclohexyl acetate hydrogenation unit: Cyclohexyl acetate and hydrogen react over a copper-based catalyst to produce cyclohexanol and ethanol. This reaction is highly exothermic, operating at a high temperature of approximately 180-250°C and a high pressure of approximately 4.5-6.0 MPa(G). A fixed-bed reactor is employed. The cyclohexyl acetate conversion rate is approximately 99% per pass, with a selectivity for cyclohexanol exceeding 98%. Small amounts of ethane, cyclohexane, methylcyclopentanol, ethylcyclohexyl ether, and other ethyl esters are produced as byproducts. Theoretically, 2 mol of hydrogen are required for every mol of cyclohexyl acetate, resulting in a hydrogen consumption of approximately 460-500 Nm3 per ton of product. 3 In order to suppress side reactions, improve reaction selectivity and hydrogen utilization, in addition to increasing the reaction pressure, the reaction feed contains a large excess of hydrogen, the hydrogen-to-ester molar ratio is high (10-50:1), and the hydrogenation adopts a cyclic process. The hydrogen concentration of the circulating hydrogen in the reaction system is lower than that of the new hydrogen of the raw material. Considering the performance of the catalyst type, the quality requirements of the raw material hydrogen of this unit are much lower than those of the benzene selective hydrogenation unit. The conventional grade hydrogen of the factory can meet the requirements, and the content of harmful components such as CO and sulfur is mainly controlled.

[0009] 4) Cyclohexanol dehydrogenation unit: refined cyclohexanol undergoes dehydrogenation reaction under the action of catalyst to generate cyclohexanone and hydrogen. The by-product hydrogen is about 220-230Nm3 / ton of product. 3 The reactor is a tubular fixed bed, typically using copper catalysts. The reaction temperature is 210-270°C, and the reaction pressure is slightly positive. The effluent from the dehydrogenation reactor undergoes heat exchange cooling and gas-liquid separation to produce a crude alcohol and ketone liquid and a gas primarily composed of by-product hydrogen. The by-product hydrogen contains small amounts of water, impurities such as benzene, cyclohexene, cyclohexane, cyclohexanone, and cyclohexanol, and sometimes trace amounts of CO and methane, but is free of harmful components such as sulfides and nitrides.

[0010] 5) Cyclohexane hydrorefining unit: This unit hydrorefines the cyclohexane produced as a by-product of the benzene selective hydrogenation unit. The by-product cyclohexane can be separated from the cyclohexene addition esterification unit. A nickel catalyst is usually used to completely hydrogenate a small amount of benzene, cyclohexene, and methylcyclopentene in the cyclohexane into corresponding saturated alkanes in a trickle bed reactor. The hydrogenation conditions are relatively mild (reaction temperature 110-160°C, reaction pressure 1.5-2.0 MPa(G)), and a one-pass hydrogenation process is usually adopted. Compared with the above two hydrogenation units, this unit has the lowest requirements for hydrogen pressure and purity, but the sulfide, water, high-boiling point organic matter, etc. in the hydrogen cannot be too high. The hydrogenation process consumes little hydrogen, and only about 9-12 Nm3 of hydrogen is consumed per ton of product. 3 .

[0011] As mentioned above, in the cyclohexanone production process by the esterification method, the hydrogen quality requirements of the hydrogen-using units are inconsistent. However, in the conventional design process, the hydrogen source for the benzene selective hydrogenation reaction unit, the esterification hydrogenation reaction unit and the cyclohexane hydrorefining unit is usually new hydrogen from the boundary area (i.e., fresh hydrogen). The advantage is that the hydrogen quality is stable and it is beneficial to production management. The disadvantage is that different qualities of hydrogen are not used in a targeted manner, and there is an excess of hydrogen quality and excessive pressure at local gas-using points.

[0012] Due to the purity limitations of the raw materials and hydrogen (usually containing small amounts of methane, nitrogen, etc.), as well as non-hydrogen components generated by side reactions, impurities accumulate in the reaction system or concentrate in the tail hydrogen, resulting in a decrease in hydrogen concentration and an increase in impurity content. For cyclohexyl acetate hydrogenation units in a cyclic process, to maintain the pressure and reaction efficiency of the hydrogenation reaction system, the hydrogen concentration in the recycle gas must be stabilized. In addition to replenishing new hydrogen to the hydrogenation reaction system, a portion (usually 1-5% of the recycle hydrogen) of the recycle hydrogen (called "purge gas") must be discharged from the reaction system. The purge gas is primarily composed of hydrogen, with a small portion of inert gases and other components corresponding to saturation pressure. For hydrogenation units in a once-through process, the composition of the tail hydrogen varies greatly depending on the reaction characteristics, raw material source, and catalyst performance. In the esterification process for producing cyclohexanone, each hydrogenation unit emits tail hydrogen, including purge gas, reaction tail hydrogen, and dissolved gas. These discharged hydrogens have varying hydrogen contents and impurity compositions.

[0013] The recovery (including purification) technology of vented gas or discharged tail hydrogen is already quite mature. For example: CN102703108A Fischer-Tropsch synthesis hydrogen-containing tail gas is purified by a pressure swing adsorption (abbreviated as "PSA") separation device to obtain hydrogen with a purity of 80-99%. CN104587797A uses a five-stage pressure swing adsorption to separate and refine hydrogen tail gas to obtain hydrogen with a molar purity of 99.95%. CN111232924A first uses membrane separation to concentrate hydrogen to 90%, and then uses pressure swing adsorption to concentrate hydrogen to greater than 99%. CN102718185 uses an ionic liquid supported liquid membrane to purify hydrogen, and the hydrogen purity can reach 90%. Process devices similar to this device, such as CN102942446A and CN105439816A, are used for acetate hydrogenation to ethanol devices. A PSA device is set up to recover hydrogen from the purge gas and recycle it to reduce reactant losses. However, the hydrogen recovery device is complex.

[0014] For the non-esterification cyclohexanone production method, there are mature technologies for hydrogen recovery and utilization. For example:

[0015] Regarding the tail hydrogen discharged from the benzene selective hydrogenation unit, Li Yingchun, Zhang Le, et al. Optimization design of the recycling system of hydrogen in cyclohexanol waste gas and chlor-alkali by-product hydrogen [J]. Henan Chemical Industry, 2019, 36(3): 33-36. A treatment method is proposed to purify the waste gas by combining low-temperature separation and temperature swing adsorption technology. CN105688591A provides a process for recycling hydrogen-containing tail gas from a cyclohexanol production device. The hydrogen-containing tail gas produced by the benzene partial hydrogenation unit is compressed to 0.7-0.8 MPa (G) by a compressor and cooled to 8-12°C and then separated to obtain crude hydrogen. The crude hydrogen is then adsorbed to obtain product hydrogen free of moisture and impurities, thereby realizing hydrogen recycling and recovering benzene, cyclohexene, and cyclohexane in the tail gas.

[0016] For the by-product hydrogen of the cyclohexanol dehydrogenation unit, most factories first cool and condense it in the dehydrogenation device to remove most of the organic matter, and then use PSA or temperature swing adsorption (abbreviated as "TSA") device for purification after compression and pressure increase. For example: CN205495345U discloses a device for purifying hydrogen in caprolactam tail gas, which uses a combination of TSA and PSA to separate cyclohexanone, cyclohexane and cyclohexanol in the tail gas hydrogen to obtain high-purity hydrogen. CN112023607A discloses a process for purifying hydrogen in tail gas, which includes cooling the tail gas with chilled water at 2 to 10°C to remove heavy aromatics, and then performing TSA and PSA in sequence to obtain purified hydrogen. The hydrogen yield is about 80%, and the analysis process requires steam. The device contains multiple temperature swing adsorption towers and multiple pressure swing adsorption towers, the device structure is complex, and the purification process is cumbersome.

[0017] Existing plants with similar or similar equipment typically discharge tail hydrogen from the benzene selective hydrogenation reaction, hydrogen emitted from the cyclohexyl acetate hydrogenation unit (including purge gas, low-fraction gas, and dissolved gas), tail hydrogen emitted from the cyclohexane hydrorefining unit, and by-product hydrogen from the cyclohexanol dehydrogenation unit. These hydrogen is either sent to the plant's hydrogen recovery unit for centralized purification, with the recovered hydrogen incorporated into the plant's hydrogen pipeline network, or simply discharged to a fuel pipeline network or flare network outside the plant boundary. Centralized purification in the hydrogen recovery unit typically utilizes a combined TSA (temperature swing adsorption) and PSA (pressure swing adsorption) adsorption unit, or membrane separation, because the hydrogen contains large organic molecules. Centralized purification in the hydrogen recovery unit typically combines and recovers hydrogen from different sources and compositions. This reduces investment costs and facilitates management, as does the relatively high volume of exhaust gas during regeneration. The hydrogen recovery rate is typically around 80%. The method of discharging hydrogen to the fuel pipeline or flare pipeline results in a waste of hydrogen and is usually used to treat hydrogen emissions with small flow and low concentration, such as low-fraction gas and dissolved gas.

[0018] Regarding cyclohexanone esterification plants, current research, both domestically and internationally, focuses on experimentally-based process conditions, catalyst preparation, and main product separation schemes. These include patents CN103664530A, CN103664531A, CN103664587B, CN103880598A, CN107434760A, CN108003017A, and CN109534954A. There is limited research on the in-plant hydrogenation process flow and the comprehensive application of hydrogen. CN114621051A and CN114621052A describe the process flow for cyclohexyl acetate hydrogenation, including the hydrogen circulation process and reaction product separation schemes. However, they do not address the optimization of hydrogen utilization across the entire plant, nor do they specify how to handle hydrogen emissions.

[0019] From the published literature, it is known that there has not been seen a method for hydrogen recovery and utilization in a cyclohexyl acetate hydrogenation unit that is exactly the same as that of the present invention, nor has there been any public report on the comprehensive and optimized utilization of hydrogen at the level of an esterification cyclohexanone device, and the cascade utilization of hydrogen within the device has not been achieved. Summary of the Invention

[0020] The cyclohexanone esterification process plant includes, but is not limited to, the following units or systems: a benzene selective hydrogenation unit (including a feedstock refining, hydrogenation reaction, and reaction product separation system), a cyclohexene esterification unit (including an esterification reaction and reaction product separation system), a cyclohexyl acetate hydrogenation unit (including an ester hydrogenation reaction, hydrogen circulation, and reaction product separation system); and a cyclohexanol dehydrogenation unit (including a cyclohexanol dehydrogenation, dehydrogenation product separation, and hydrogen compression system). The present invention proposes a process for the comprehensive utilization of hydrogen within a cyclohexanone esterification process plant, optimizing the processing and utilization of hydrogen within the plant and enabling low-cost processing and reuse of hydrogen within the plant. This process reduces the hydrogen consumption of the cyclohexanone plant, reduces the amount of hydrogen recovered from external transport, and reduces material losses, thereby enhancing the competitiveness of the cyclohexanone esterification process plant.

[0021] A system and process for comprehensive utilization of hydrogen in a cyclohexanone esterification process unit systematically optimizes the hydrogen treatment and application process within the unit. This is achieved through the following technical solutions:

[0022] A comprehensive hydrogen utilization system in a cyclohexanone esterification process device mainly comprises a benzene selective hydrogenation unit, a cyclohexene esterification addition unit, a cyclohexyl acetate hydrogenation unit, a cyclohexane hydrorefining unit, and a cyclohexanol dehydrogenation unit, characterized in that: a new hydrogen feed pipe is connected to the benzene selective hydrogenation unit and the cyclohexyl acetate hydrogenation unit respectively, the benzene selective hydrogenation unit is connected to the cyclohexene esterification addition unit; the cyclohexyl acetate pipeline of the cyclohexene esterification addition unit is connected to the cyclohexyl acetate hydrogenation unit, and the crude cyclohexane pipeline is connected to the cyclohexane hydrorefining unit; the cyclohexene acetate feed pipe ... The cyclohexanol pipeline of the cyclohexyl ester hydrogenation unit is connected to the cyclohexanol dehydrogenation unit, the purge gas pipeline of the cyclohexyl acetate hydrogenation unit is connected to the cyclohexane hydrorefining unit, and the analytical gas pipeline of the cyclohexyl acetate hydrogenation unit is connected to the factory fuel pipeline network; the tail hydrogen discharge pipeline of the cyclohexane hydrorefining unit is connected to the factory fuel pipeline network; the tail hydrogen discharge pipeline of the benzene selective hydrogenation unit, the by-product hydrogen pipeline of the cyclohexanol dehydrogenation unit, and the pure low-fraction gas pipeline of the cyclohexyl acetate hydrogenation unit are mixed before the inlet of the hydrogen compressor, and the hydrogen outlet pipeline of the hydrogen compressor is connected to the cyclohexyl acetate hydrogenation unit.

[0023] The hydrogen compressor is arranged in the cyclohexanol dehydrogenation unit, and may be a by-product hydrogen compressor of the cyclohexanol dehydrogenation unit.

[0024] The cyclohexyl acetate hydrogenation unit is composed of a hydrogenation reactor, a feed heat exchanger, a feed heater, a high-fraction gas cooler, a purge gas cooler, a low-fraction gas cooler, a high-pressure separator, a high-pressure condensate tank, a low-pressure separator, a circulating hydrogen compressor, a purge gas purifier, and a low-fraction gas purifier.

[0025] A feed pipeline for a mixture of cyclohexyl acetate and circulating hydrogen is connected to a hydrogenation reactor; an effluent pipeline from the hydrogenation reactor is connected to a hot side inlet of a feed heat exchanger, which is connected to a high-pressure separator; the high-pressure separator tank is provided with a high-fraction liquid outlet, and a high-fraction gas outlet mainly containing hydrogen is provided on the top; the high-fraction gas outlet is connected to a high-fraction gas cooler, which is connected to a high-pressure condensate tank; a high-fraction condensate outlet mainly containing ethanol is provided at the bottom of the high-pressure condensate tank, a cold high-fraction gas outlet is provided on the top of the high-pressure condensate tank, and the cold high-fraction gas outlet is connected to a circulating hydrogen compressor; new hydrogen and recycled hydrogen pipelines are connected to a circulating hydrogen pipeline at the inlet of a circulating hydrogen compressor, and then to the inlet of a circulating hydrogen compressor, the outlet of the circulating hydrogen compressor is connected to a cyclohexyl acetate feed pipeline, and then to the cold side inlet of a feed heat exchanger, the cold side outlet of the feed heat exchanger is connected to a feed heater, and the outlet of the feed heater is connected to the hydrogenation reactor.

[0026] The top of the high-pressure condensate tank is also equipped with a purge gas outlet connected to the purge gas cooler. The gas phase outlet of the purge gas cooler is connected to the purge gas purification facility, and the liquid phase outlet of the purge gas cooler is connected to the high-pressure condensate tank. A small portion of the cold high-fraction gas is discharged from the hydrogen circulation system as purge gas to control the hydrogen concentration in the circulating hydrogen at the inlet of the circulating hydrogen compressor to be above 90%.

[0027] The high-liquid outlet at the bottom of the high-pressure separator tank is connected to the low-pressure separator. The top of the low-pressure separator is provided with a low-gas outlet mainly composed of hydrogen. The low-gas outlet is connected to the low-gas cooler. The gas phase outlet of the low-gas cooler is connected to the low-gas purification facility. The liquid phase outlet of the low-gas cooler is connected to the low-pressure separator.

[0028] A process for comprehensive utilization of hydrogen in a cyclohexanone esterification device:

[0029] The hydrogen source of the benzene selective hydrogenation unit adopts external supply of new hydrogen, and the tail hydrogen discharged from the hydrogenation reaction is sent to the hydrogen compression system of the cyclohexanol dehydrogenation unit;

[0030] The tail hydrogen discharged from the benzene selective hydrogenation unit is mixed with the by-product hydrogen from the cyclohexanol dehydrogenation unit and the pure low-fraction gas from the cyclohexyl acetate hydrogenation unit before the inlet of the hydrogen compressor of the cyclohexanol dehydrogenation unit, compressed by the hydrogen compressor, and then cooled and separated to obtain recycled hydrogen, which is then sent to the cyclohexyl acetate hydrogenation unit;

[0031] The hydrogen source of the cyclohexyl acetate hydrogenation unit is the recycled hydrogen from the cyclohexanol dehydrogenation unit, and the insufficient hydrogen is supplemented by new hydrogen supplied from outside;

[0032] The hydrogen discharged from the cyclohexyl acetate hydrogenation unit includes purge gas, low-fraction gas and dissolved gas. The purge gas and low-fraction gas are treated through an additional separation process and then sent to the cyclohexane hydrorefining unit and cyclohexanol dehydrogenation unit respectively.

[0033] The hydrogen source of the cyclohexane hydrorefining unit is the pure purge gas from the cyclohexyl acetate hydrogenation unit;

[0034] The tail hydrogen discharged from the cyclohexane hydrotreating unit is sent to the factory fuel pipeline or hydrogen recovery device.

[0035] The new hydrogen is fresh hydrogen supplied from outside the device, wherein the hydrogen gas volume fraction is greater than 95%, preferably greater than 99%, more preferably greater than 99.9%;

[0036] Furthermore, the mass fraction of sulfur in the new hydrogen is not greater than 0.1 ppm, and the volume fractions of CO and CO2 are both not greater than 10 ppm.

[0037] The benzene selective hydrogenation unit includes systems such as raw material refining, hydrogenation reaction and reaction product separation;

[0038] Furthermore, the new hydrogen is first refined in the unit to a sulfur mass fraction of no more than 0.3 ppb before entering the hydrogenation reactor.

[0039] Furthermore, the raw benzene is first refined in the unit to a sulfur mass fraction of no more than 1.0 ppb before entering the hydrogenation reactor.

[0040] Furthermore, the operating pressure of the benzene selective hydrogenation reaction is 4.0 to 6.0 MPa(G), preferably 4.5 to 5.5 MPa(G);

[0041] Furthermore, the operating temperature of the benzene selective hydrogenation reaction is 100-180°C, preferably 125-150°C.

[0042] The tail hydrogen discharged from the benzene selective hydrogenation unit is a gas obtained by flashing the reaction effluent of the hydrogenation reactor to obtain flash gas, cooling and separating the flash gas, and then sending it to the cyclohexanol dehydrogenation unit.

[0043] The reaction effluent of the hydrogenation reactor is flash-evaporated to obtain flash gas and flash liquid, which are then cooled and separated from the gas and liquid to remove most of the water, cyclohexene, benzene and cyclohexane to obtain tail hydrogen. The tail hydrogen has a high hydrogen volume fraction (about 95%), and other components include water, nitrogen, cyclohexane, cyclohexene and benzene. The content of harmful impurities is extremely low and can be reused in the device without special treatment. However, its flow rate is not large and the pressure is low, with an emission rate of about 10 to 20 Nm per ton of product. 3 If it is discharged into the fuel pipeline network, valuable hydrogen, benzene and cyclohexene will be lost.

[0044] Furthermore, the tail hydrogen discharge has a pressure of 0.3-0.8 MPa(G), preferably 0.4-0.6 MPa(G); this pressure is determined by the flash evaporation pressure. A low flash evaporation pressure is conducive to releasing more dissolved gases, but will increase the organic matter and water content in the flash gas and increase the cooling energy consumption when cooling the flash gas.

[0045] Furthermore, the temperature of the discharged tail hydrogen is 10-30° C., preferably 12-20° C. This refers to the temperature of the flash steam after cooling. A low temperature is conducive to better recovery of organic matter therein.

[0046] The by-product hydrogen of the cyclohexanol dehydrogenation unit is the by-product hydrogen produced when cyclohexanol is dehydrogenated to produce cyclohexanone. It is the reaction effluent of the cyclohexanol dehydrogenation reactor. After multiple heat exchange cooling and gas-liquid separation, the hydrogen is obtained, and most of the organic matter (such as cyclohexanone and cyclohexanol) is removed. The by-product hydrogen contains a small amount of impurities such as water, cyclohexene, cyclohexane, cyclohexanone and cyclohexanol, and does not contain other harmful impurities except for trace amounts of CO, and has the possibility of being reused in the device. The by-product hydrogen per ton of product is 220-235Nm 3 .

[0047] Furthermore, the by-product hydrogen has a temperature of 10-60° C., preferably 15-45° C. This is the temperature at which the by-product hydrogen is obtained after the reaction product is cooled and separated. A lower temperature is conducive to the recovery and removal of more organic matter. The temperature is determined by comprehensively considering the pressure drop of the reaction system, the power consumption of the compressor, and the consumption of the common refrigerant.

[0048] Furthermore, the by-product hydrogen has a pressure of 0.00 to 0.50 MPa(G), preferably 0.001 to 0.20 MPa(G), which is limited by the pressure of the cyclohexanol dehydrogenation reaction and is usually a slightly positive pressure.

[0049] The by-product hydrogen is mixed with the tail hydrogen discharged from the benzene selective hydrogenation unit and the pure low-fraction gas from the cyclohexyl acetate hydrogenation unit before the inlet of the hydrogen compressor of the cyclohexanol dehydrogenation unit, and then compressed by the hydrogen compressor to obtain compressed hydrogen.

[0050] The compressed hydrogen is then cooled and separated from the gas and liquid to further reduce the contents of water, cyclohexanol, cyclohexanone, cyclohexane, cyclohexene, etc. in the gas to obtain recycled hydrogen.

[0051] The byproduct hydrogen from cyclohexanol dehydrogenation, or the purge gas emitted from the hydrogenation unit, is typically recovered and treated using a combined TSA and PSA system to remove water, organic matter, and other gases to produce high-purity hydrogen. However, in addition to consuming energy, this process also results in approximately 20% of the gas being lost during the regeneration process. The inventors have discovered that conventional processes involving pressurization, cooling, and gas-liquid separation can effectively reduce the organic and water content, particularly cyclohexanol and cyclohexanone, in the hydrogen produced. The present device primarily utilizes hydrogen at high pressure, which is beneficial for reducing the amount of organic matter in the compressed hydrogen. The inventors have also discovered that the recycled hydrogen produced through the aforementioned treatment measures, containing components such as water, light hydrocarbons, cyclohexane, cyclohexene, cyclohexanone, and cyclohexanol, is highly compatible with the hydrogenation reaction environment of the cyclohexyl acetate hydrogenation unit. Its presence is low in harmful impurities, presenting no significant adverse effects on the esterification hydrogenation and cyclohexane hydrorefining processes, nor on the quality of related products, and meeting the hydrogen quality requirements of the cyclohexyl acetate hydrogenation unit. The cyclohexane, cyclohexene, cyclohexanone and cyclohexanol in the recycled hydrogen eventually become part of the target product.

[0052] Furthermore, the recycled hydrogen has a temperature of 10-45°C, preferably 12-20°C. This refers to recycled hydrogen obtained by cooling compressed hydrogen. The lower the temperature, the lower the content of components such as cyclohexane, cyclohexanol, and cyclohexanone in the recycled hydrogen, thereby reducing the amount of these components circulating in the system. However, too low a cooling temperature will consume more energy.

[0053] Furthermore, the recycled hydrogen is connected to the circulating hydrogen system in the cyclohexyl acetate hydrogenation unit at a location before the hydrogen inlet of the circulating hydrogen compressor (abbreviated as "circulating hydrogen compressor") or after the hydrogen outlet of the circulating hydrogen compressor. Preferably, the recycled hydrogen is connected to the circulating hydrogen system before the hydrogen inlet of the circulating hydrogen compressor. Specifically, the recycled hydrogen can be connected to the buffer tank at the inlet of the circulating hydrogen compressor.

[0054] Furthermore, the pressure of the recycled hydrogen is 1.0 MPa, preferably 0.5 MPa, and more preferably 0.1 MPa higher than the pressure at the point of introduction. The point at which the recycled hydrogen is introduced into the circulating hydrogen system will affect the determination of the hydrogen outlet pressure of the hydrogen compressor in the cyclohexanol dehydrogenation unit. The present invention does not have any special requirements for the determination of the pressures of the compressed hydrogen and recycled hydrogen. Professional engineers in this field can calculate and determine them according to conventional engineering design or engineering knowledge to ensure that the recycled hydrogen can smoothly enter the circulating hydrogen system.

[0055] The invention relates to a process for comprehensive utilization of hydrogen in a cyclohexanone esterification device, and also includes a process for treating hydrogen discharged from a cyclohexyl acetate hydrogenation unit.

[0056] The reaction effluent of the hydrogenation reactor in the cyclohexyl acetate hydrogenation unit is heat exchanged with the reaction feed, cooled to 100-180°C, and then enters the high-pressure separator for gas-liquid separation to obtain high-pressure hydrogen-containing gas (referred to as "high-fraction gas") and high-pressure separation liquid (referred to as "high-fraction liquid"). The high-fraction gas is cooled and enters the high-pressure condensate tank for further gas-liquid separation to obtain cold high-fraction gas and high-fraction condensate. The cold high-fraction gas is divided into two paths: one path enters the circulating hydrogen compressor for pressure increase and circulation back to the hydrogenation reactor, and the other path is the purge gas.

[0057] The purge gas is a part of the circulating hydrogen gas discharged from the circulating hydrogen system in order to maintain the circulating hydrogen concentration in the hydrogenation reaction system and balance the impurity concentration. The main component of the purge gas is usually hydrogen. For the cyclohexyl acetate hydrogenation unit, the purge gas volume per ton of product is about 15 to 30 Nm 3 , which is related to the purity of new hydrogen, reaction by-products, reaction conditions, etc.; in addition to hydrogen, the purge gas also contains a small amount of ethanol, water, ethane, cyclohexane, cyclohexanol, as well as inert and harmful components brought by new hydrogen.

[0058] The purge gas is further cooled and subjected to gas-liquid separation to obtain "dry purge gas", which is then treated in purification process A to obtain pure purge gas, which is directly sent to the cyclohexane refining unit without pressurization. These measures are all aimed at controlling the content of components such as water, ethanol, and cyclohexane in the purge gas.

[0059] The high fraction liquid enters the low pressure separator for flash evaporation to obtain gas as low fraction gas and liquid as low fraction liquid.

[0060] The high-fraction condensate and the low-fraction liquid undergo distillation within this unit to separate the target product. During the subsequent separation process, light components such as hydrogen dissolved in the high-fraction condensate and the low-fraction liquid are released during distillation or evaporation to form dissolved gas. Because this dissolved gas contains relatively high amounts of impurities such as light hydrocarbons and ethanol and has a low flow rate, it is sent to the factory fuel pipeline network.

[0061] The low-fraction gas is further cooled and subjected to gas-liquid separation to obtain "dry low-fraction gas", which is then treated by purification process B to obtain pure low-fraction gas, which is then sent to the cyclohexanol dehydrogenation unit.

[0062] Furthermore, the gas-liquid separation operating pressure of the high-pressure separator is 1.0 MPa, preferably 0.5 MPa, and more preferably 0.1 MPa lower than the operating pressure of the hydrogenation reactor. The specific operating pressure is determined based on a comprehensive consideration of technical and economic factors, including the operating pressure of the upstream hydrogenation reactor, the circulating hydrogen flow rate, and the equipment and piping layout.

[0063] Furthermore, the pressure difference between the high-pressure separator and the high-pressure condensate tank is no greater than 0.5 MPa, preferably 0.1 MPa, and more preferably 0.05 MPa. This pressure difference is primarily determined by the pressure drop during the transportation of the high-pressure gas from the high-pressure separator, through the cooler, to the high-pressure condensate tank, combined with operational adjustability. A smaller pressure difference means a higher high-pressure gas pressure, which is more conducive to reducing the content of components such as water, light hydrocarbons, and ethanol in the gas. A higher high-pressure condensate tank pressure is more conducive to energy saving of the circulating hydrogen compressor.

[0064] Furthermore, the flash pressure of the low-pressure separator is 0.4-1.2 MPa(G), preferably 0.8-1.0 MPa(G). A high flash pressure in the low-pressure separator produces less flash gas, but a higher hydrogen concentration; a low flash pressure produces more flash gas, but a lower hydrogen concentration, and an increased organic matter concentration, particularly increasing the ethanol content. This pressure is determined based on the composition of the low-pressure gas and subsequent treatment of the low-pressure liquid.

[0065] Furthermore, the high-fraction gas is cooled to 30-60°C, preferably 40-50°C, before entering the high-pressure condensate tank. Lower cooling temperatures facilitate the removal of water and organic matter from the gas, resulting in cold high-fraction gas. However, this requires the use of a more expensive low-temperature refrigerant. Furthermore, the high-fraction condensate still needs to be heated for downstream separation. Circulating cooling water is typically used as the refrigerant to cool the high-fraction gas to 40-50°C.

[0066] Furthermore, the purge gas is cooled to 10-40° C., preferably 12-20° C. The purge gas is further cooled, and part of the water and organic matter in the gas is condensed into liquid, which is removed by gas-liquid separation.

[0067] Furthermore, the purification process, including purification process A and purification process B, can be an adsorption process, a gas absorption process or a combination thereof, preferably a gas absorption process.

[0068] Optionally, an adsorption process is used, and components such as ethanol, water and cyclohexanol in the purge gas are adsorbed by the adsorbent. When the adsorption is saturated, the adsorbent is regenerated and analyzed using circulating hydrogen in this unit at a temperature of not less than 150°C, and the analyzed gas is discharged to the fuel pipeline network.

[0069] Furthermore, the gas absorption process uses one or a mixture of cyclohexanone, cyclohexanol, and cyclohexyl acetate as the absorption liquid, which contacts the purge gas (or low-fraction gas) in the absorption tower to absorb most of the organic matter in the gas and become an absorption rich liquid.

[0070] Furthermore, the purge gas has a hydrogen purity of 90 mol% or more.

[0071] Furthermore, the purification process A and the purification process B may use the same principle or different principles, preferably using the same principle. The same principle means that both use the adsorption principle or the gas absorption principle, preferably the gas absorption principle, for ease of management and operation.

[0072] Specifically, the gas absorption process uses one or a mixture of cyclohexanone, cyclohexanol, and cyclohexyl acetate as the absorption liquid, preferably cyclohexanol containing 1-5% by mass of cyclohexanone or cyclohexanol containing 1-50% by mass of cyclohexyl acetate, and specifically can be one or a combination of the cyclohexanol light removal tower bottom liquid, cyclohexanone tower bottom liquid, cyclohexanol tower overhead distillate, and cyclohexyl acetate recovery tower overhead distillate in patent CN114763318A; the absorption liquid is sent to the top of the absorption tower and is in countercurrent contact with the purge gas (low-fraction gas for purification process B) in the tower, and water and part of the organic matter in the gas are absorbed and purified, further reducing the content of components such as water and ethanol in the purge gas (or low-fraction gas). The purified purge gas (or low-fraction gas) contains a small amount of cyclohexanol in addition to inert gases (such as nitrogen, methane, ethane); and the absorption liquid that has absorbed the organic matter and water in the gas becomes the absorption rich liquid.

[0073] Furthermore, for purification process A, the operating pressure of the absorption tower is no less than 0.5 MPa, preferably 0.1 MPa, and more preferably 0.05 MPa, lower than the operating pressure of the high-pressure condensate tank. The gas absorption process should be performed at the highest possible operating pressure to improve the absorption effect and reduce the organic content in the hydrogen after absorption.

[0074] The inventors have calculated and experimented carefully, and the purge gas is processed by the method given by the present invention, and the organic matter in the hydrogen after the process is controlled (such as cyclohexanol, ethanol, and cyclohexanone content is no more than 50ppm (Vol)), there is no free water in the hydrogen, and other harmful components are low in content, which will not adversely affect the nickel catalytic hydrogenation process in the cyclohexane refining unit. Cyclohexanol and cyclohexanone content are low in the hydrogen, and the hydrogen flow rate is small, and the amount finally dissolved in cyclohexane is extremely low, which hardly affects the quality of cyclohexane. A small amount of light components such as ethanol and ethane in the hydrogen is distilled off at the top of the cyclohexane distillation tower and enters light oil. In particular, the by-product hydrogen of the cyclohexanol dehydrogenation unit is used as a partial hydrogen source for the cyclohexyl acetate unit, which is conducive to reducing the content of harmful components (such as sulfur, nitrogen, etc.) in the circulating hydrogen and the purge gas, and is more conducive to implementing the inventive method. When implementing the technical method of the present invention, the hydrogen concentration of the purge gas should be lower than that of the new hydrogen. The same hydrogenation refining effect can be achieved by appropriately increasing the hydrogenation pressure and / or slightly increasing the reaction temperature, and increasing the discharge tail hydrogen flow rate.

[0075] Specifically, under normal operating conditions, the amount of hydrogen in the purge gas of the esterification hydrogenation system (15 to 30 Nm3 ), which is more than the amount of hydrogen required for cyclohexane refining hydrogenation (9 to 12 Nm 3 ); The esterification hydrogenation reaction pressure is much higher than the operating pressure of the cyclohexane refining hydrogenation process (1.2-1.8 MPa under normal circumstances), and the purge gas does not need to be compressed and can be directly used in the cyclohexane refining hydrogenation process.

[0076] Furthermore, the low fraction gas is cooled to 10-50° C., preferably 12-20° C. By further cooling the low fraction gas, part of the water and organic matter therein is condensed into liquid, which is removed by gas-liquid separation; and the low temperature is also conducive to the next purification process.

[0077] Purification Process A and Purification Process B serve the same purpose: to further remove organic matter and other components from the gas. The gas contacts the cyclohexanol absorption solution within the absorption tower, and components such as ethanol in the gas enter the cyclohexanol solution. Adsorption and gas absorption processes are both common chemical operations in the chemical industry. Their principles and process flows are detailed in "Yuan Weikang, Wang Jingkang, et al., Handbook of Chemical Engineering, Volume 2, Part 12, Gas Absorption [M]. Part 18, Adsorption and Ion Exchange [M]. Chemical Industry Press, 2019." Gas absorption processes are well known to professional engineers in this field. Operating at the highest possible operating pressure is crucial. Lowering the temperature of the absorption and circulating absorption solutions, or increasing the absorption solution flow rate, can improve absorption effectiveness. Professional engineers can reasonably determine the operating pressure of the absorption process based on the upstream gas pressure, process, and equipment requirements. They can also determine the detailed absorption process flow, absorption solution flow rates, temperatures, and other operating conditions based on absorption requirements and physical properties.

[0078] Specifically, the ethanol and cyclohexanol contents in the purge gas after treatment by purification process A (pure purge gas) are controlled to be no more than 25 ppm (Vol) and 50 ppm (Vol), respectively; excessive cyclohexanol and ethanol content in the purge gas has a certain impact on the catalyst performance and causes loss of high-value ethanol and cyclohexanol products; after the hydrorefining unit reaction, ethanol and cyclohexanol are mainly enriched in cyclohexane, and in the separation tower, ethanol and cyclohexanol will enter light oil and cyclohexane, respectively.

[0079] Specifically, the low-fraction gas treated by purification process B is controlled so that the ethanol and cyclohexanol contents in the treated low-fraction gas (pure low-fraction gas) do not exceed 150 ppm (Vol) and 300 ppm (Vol), respectively; when the pure low-fraction gas is compressed, cooled, and subjected to gas-liquid separation in the cyclohexanol dehydrogenation unit, most of the cyclohexanol and a portion of the ethanol in the low-fraction gas enter the crude alcohol ketone solution as condensate, the ethanol in the solution eventually enters the light component, and the cyclohexanol is recovered; the cyclohexanol and ethanol remaining in the low-fraction gas are returned together to the ester hydrogenation unit.

[0080] Furthermore, the pure low-fraction gas is sent to the cyclohexanol dehydrogenation unit and mixed with other hydrogen before the inlet of the hydrogen compressor, and is recycled after compression and liquid separation.

[0081] Furthermore, the temperature of the absorption liquid is not higher than 45°C, preferably not higher than 35°C, and more preferably not higher than 30°C; this low temperature is conducive to absorption. In addition to considering the absorption requirements and energy consumption, the temperature is determined in combination with the fluidity of the absorption liquid.

[0082] Furthermore, the absorbed rich liquid is sent to the corresponding refining facilities of this unit for treatment, such as the ethanol-cyclohexanol separation tower in patent CN114763318A for refining.

[0083] The tail hydrogen discharged from the cyclohexane hydrotreating unit is sent to the fuel pipeline network or the hydrogen recovery device; the tail hydrogen discharged from the cyclohexane hydrotreating unit is the inert gas and other impurities brought by the new hydrogen concentrated in the device, the non-condensable gas dissolved in the material during the process, and the low-boiling point components produced as by-products of the reaction process, including nitrogen, methane, ethane, CO, CO2, and other organic gases in the production process. The hydrogen concentration is low and it is difficult to be treated by conventional processes and is recycled within the device.

[0084] Compared with conventional technologies, the present invention has the following beneficial effects:

[0085] The technology of the present invention is based on the characteristics and quality requirements of each hydrogen usage point in the cyclohexanone esterification process device, combined with the composition of each discharged hydrogen or by-product hydrogen, and does not adopt the TSA and / or PSA method. Instead, it adopts mature and conventional technology to low-cost treatment of the discharged hydrogen or by-product hydrogen, thereby realizing the cascade utilization of hydrogen in the cyclohexanone device, reducing the amount of discharged hydrogen to be processed and the loss of valuable materials, reducing the amount of new hydrogen added to the device, and reducing the production cost of cyclohexanone esterification process, and has industrial application value.

[0086] In this manual, MPa(G) refers to gauge pressure, Nm 3 It refers to the volume of gas at 0 degrees Celsius and 1 standard atmosphere; ppm is usually the concentration expressed as the mass of the solute as parts per million of the mass of the total solution, ppb is usually the concentration expressed as the mass of the solute as parts per billion of the mass of the total solution, ppm(Vol) and ppm(mol) represent the concentrations of parts per million by volume and mole, respectively, %(wt) represents the concentration as a percentage by mass, and %(Vol) represents the concentration as a percentage by volume; these are all well-known technologies, units or symbols.

[0087] In the description of the present invention, it should be understood that the term "ton of product" specifically refers to each ton of cyclohexanone product; "dry purge gas", "pure purge gas", "dry low-fraction gas", "pure low-fraction gas", etc. only indicate the relative degree of water and organic matter in the gas, and cannot be understood as the concept of "free" or "pure". BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 This is a schematic diagram of a hydrogen comprehensive utilization system in a cyclohexanone esterification device of the present invention.

[0089] Figure 2 This is a simplified flow chart of the hydrogen process for Comparative Example 1.

[0090] Figure 3 The figure is a schematic diagram of hydrogen treatment in a cyclohexyl acetate hydrogenation system in a cyclohexanone esterification process unit of the present invention.

[0091] R01-hydrogenation reactor, E01-feed heat exchanger, E02-feed heater, E03-high-fraction gas cooler, E04-purge gas cooler, E05-low-fraction gas cooler, V01-high-pressure separator, V02-high-pressure condensate tank, V03-low-pressure separator, K01-circulating hydrogen compressor, X01-purge gas purifier, X02-low-fraction gas purifier.

[0092] S01-cyclohexyl acetate, S02-reaction feed after heat exchange, S03-new hydrogen, S04-circulating hydrogen after compression, S05-reactor feed, S06-reactor effluent, S07-reaction effluent after heat exchange, S08-high-fraction gas, S09-cold high-fraction gas, S10-circulating hydrogen, S11-purge gas, S12-purge gas condensate, S13-dry purge gas, S14-pure purge gas, S15-high-fraction condensate, S20-high-fraction liquid, S21-low-fraction gas, S22-low-fraction gas condensate, S23-dry low-fraction gas, S24-pure low-fraction gas, S25-low-fraction liquid, S31-recycled hydrogen.

[0093] CM: represents refrigerant inlet, including but not limited to circulating cooling water or low-temperature cooling water; CMR: represents refrigerant outlet, including but not limited to circulating cooling return water or low-temperature cooling return water; HM: represents heat medium inlet, including but not limited to steam; HMR: represents heat medium outlet, including but not limited to steam condensate.

[0094] The accompanying drawings are used to provide further understanding of 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. DETAILED DESCRIPTION

[0095] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only schematic diagrams of the embodiments of the present invention; the equipment or pipelines, or the number of units in the drawings, do not represent that the factory equipment is configured with only these equipment or the number of equipment in the drawings.

[0096] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0097] A comprehensive hydrogen utilization system in an esterification cyclohexanone device mainly consists of a benzene selective hydrogenation unit, a cyclohexene esterification addition unit, a cyclohexyl acetate hydrogenation unit, a cyclohexane hydrogenation refining unit, and a cyclohexanol dehydrogenation unit. The new hydrogen feed pipe is connected to the benzene selective hydrogenation unit and the cyclohexyl acetate hydrogenation unit respectively, and the benzene selective hydrogenation unit is connected to the cyclohexene esterification addition unit; the cyclohexyl acetate pipeline of the cyclohexene esterification addition unit is connected to the cyclohexyl acetate hydrogenation unit, and the crude cyclohexane pipeline is connected to the cyclohexane hydrorefining unit; the cyclohexanol pipeline of the cyclohexyl acetate hydrogenation unit is connected to the cyclohexanol dehydrogenation unit, the purge gas pipeline of the cyclohexyl acetate hydrogenation unit is connected to the cyclohexane hydrorefining unit, and the analytical gas pipeline of the cyclohexyl acetate hydrogenation unit is connected to the factory fuel pipeline network; the tail hydrogen discharge pipeline of the cyclohexane hydrorefining unit is connected to the factory fuel pipeline network; the tail hydrogen discharge pipeline of the benzene selective hydrogenation unit, the by-product hydrogen pipeline of the cyclohexanol dehydrogenation unit, and the pure low-fraction gas pipeline of the cyclohexyl acetate hydrogenation unit are mixed before the inlet of the hydrogen compressor, and the hydrogen outlet pipeline of the hydrogen compressor is connected to the cyclohexyl acetate hydrogenation unit.

[0098] Example 1

[0099] The specific embodiments of the present invention are described in detail below in conjunction with the technical solutions and the accompanying drawings. A 100,000 ton / year cyclohexanone esterification plant is used as an example to further illustrate the technology of the present invention.

[0100] Raw benzene: benzene content ≥99.95% (wt), sulfur content ≤1.0ppm, thiophene ≤0.1ppm;

[0101] New hydrogen: hydrogen content ≥99.9% (Vol), CO2 <10ppm (Vol), CO <10ppm (Vol), sulfur <0.1ppm, CH4 <50ppm (Vol), H2O <10mg / m 3 .

[0102] 1) Benzene selective hydrogenation unit

[0103] First, new hydrogen is refined to obtain reaction hydrogen with a total sulfur content of no more than 0.1 ppb and a CO+CO2 content of no more than 20 ppm. The hydrogen is compressed and then reacted with refined benzene in a series hydrogenation reactor equipped with a catalyst to selectively hydrogenate benzene to produce cyclohexene. The reaction is carried out at a pressure of 4.5-5.0 MPaG and a temperature of 125-145°C. The benzene conversion rate is about 42%, the cyclohexene selectivity is about 80%, and cyclohexane is mainly produced as a by-product. The hydrogenation adopts a one-pass process. The hydrogenation reaction effluent enters a flash tank where gas-liquid separation is performed at 0.4 MPa (G), yielding an oil phase containing benzene, cyclohexene, and cyclohexane, and a gas phase containing hydrogen. The gas phase is cooled to approximately 15°C before undergoing gas-liquid separation, recovering organic matter as a liquid and producing tail hydrogen. The tail hydrogen contains approximately 95% hydrogen, with other components including water, methane, nitrogen, benzene, cyclohexene, and cyclohexane. Harmful impurities such as sulfides and nitrogen oxides are less than 1 ppm. The tail hydrogen is then fed to the hydrogen compression system of the cyclohexanol dehydrogenation unit for compression, treatment, and reuse. The oil phase containing benzene, cyclohexene, and cyclohexane enters the next process, extractive distillation, to recover the benzene for recycling. The resulting cyclohexene and cyclohexane mixture is then fed to the cyclohexene esterification unit.

[0104] New hydrogen comes from outside the boundary area, with a flow rate of 8350Nm 3 / h (equivalent to 100% hydrogen, the same below);

[0105] This unit emits tail hydrogen with a hydrogen content of 95% (Vol) and a hydrogen flow rate of 182.5Nm 3 / h.

[0106] 2) Cyclohexene esterification unit

[0107] Pure "cyclohexene or cyclohexene mixture" from the benzene selective hydrogenation unit and externally supplied raw acetic acid undergo an esterification reaction with acetic acid in a series of esterification reactors under the action of a catalyst and high pressure and medium temperature conditions to produce cyclohexyl acetate. The reaction product is refined through a complex separation process to obtain the cyclohexyl acetate product, and the acetic acid is recovered and recycled to obtain cyclohexane from which the acetic acid and ester components are removed. This unit does not involve the use of hydrogen.

[0108] 3) Cyclohexyl acetate hydrogenation unit

[0109] The cyclohexyl acetate and recycled hydrogen mixture (S05) heated to 190°C after heat exchange enters a fixed-bed reactor (R01) equipped with a copper-based catalyst in parallel. In this reactor (R01), the cyclohexyl acetate undergoes a selective hydrogenation reaction under the action of the catalyst and hydrogen. The reaction effluent (S06) contains cyclohexanol and ethanol produced by the reaction, ethane as a by-product, and unreacted hydrogen and ester. The reaction temperature is 180-210°C and the reaction pressure is 5.1-5.2 MPaG. It is a highly exothermic reaction. The heat released by the reaction is removed by a cooling medium (CM) in the shell side. The single-pass conversion rate of cyclohexyl acetate is approximately 99%, the selectivity for cyclohexanol is greater than 99%, and small amounts of ethane, cyclohexane, methylcyclopentanol, ethyl acetate, and ethylcyclohexyl ether are by-products. The reaction effluent also contains a certain amount of unreacted cyclohexyl carboxylate and a small amount of high-boiling products. The hydrogen-ester molar ratio is high (20:1), and the hydrogenation adopts a cyclic process.

[0110] The effluent of the hydrogenation reactor (S06) passes through the reaction effluent / raw material heat exchanger (E01) and is cooled to about 130°C. The cooled reaction effluent (S07) enters the high-pressure separator (V01) and is subjected to gas-liquid separation at a pressure of 4.8 to 5.0 MPaG. A high-fraction liquid (S20) mainly composed of ethanol and cyclohexanol is separated at the bottom of the high-pressure separator tank (V01), and a high-fraction gas (S08) mainly composed of hydrogen is separated at the top; the high-fraction gas is cooled to 45°C by circulating cooling water (S09), enters the high-pressure condensate tank (V02), and is further subjected to gas-liquid separation at a pressure of 4.8 to 5.0 MPaG. A high-fraction condensate (S15) mainly composed of ethanol is separated at the bottom of the high-pressure condensate tank (V02); the high-pressure condensate Cold high-fraction gas is separated from the top of the liquid tank (V02). Most of the cold high-fraction gas is used as circulating hydrogen (S10) and fed to the circulating compressor (K01). A small portion of the cold high-fraction gas is discharged from the hydrogen circulation system as purge gas (S11) to control the hydrogen concentration of the circulating hydrogen at the inlet of the circulating hydrogen compressor to be above 90%. The new hydrogen (S03) and the recycled hydrogen (S31) are mixed with the circulating hydrogen (S10) at the inlet of the circulating hydrogen compressor and compressed to 5.5 MPaG in the circulating hydrogen compressor (K01) to produce compressed circulating hydrogen (S04). This is then mixed with the incoming cyclohexyl acetate (S01), heat exchanged in E01, and heated to 190°C, close to the hydrogenation reaction temperature, in the feed heater (E02) before entering the hydrogenation reactor (R01). The recycled hydrogen (S31) comes from the hydrogen compressed and processed in the cyclohexanol dehydrogenation unit.

[0111] The purge gas (S11) is cooled to 12°C by low-temperature cooling water in the purge gas cooler (E04), and gas-liquid separation is performed at a pressure of 4.8-5.0 MPaG to obtain a high-fraction condensate (S) of the purge gas condensate (S12) mainly composed of ethanol, and a "dry purge gas" (S13) mainly composed of hydrogen; the dry purge gas (S13) is sent to the purification process A (X01).

[0112] The high-fraction liquid (S20) separated at the bottom of the high-pressure separator tank enters the low-pressure separator (V03) and undergoes adiabatic flash evaporation at a pressure of 0.8-1.0 MPaG (temperature of approximately 75°C). A low-fraction liquid (S25) composed primarily of cyclohexanol and ethanol is obtained from the bottom of the tank, and a low-fraction gas (S21) composed primarily of hydrogen is separated from the top. The low-fraction gas (S21) is cooled to 12°C in the low-fraction gas cooler (E05) using low-temperature cooling water. The dry low-fraction gas (S23) obtained through gas-liquid separation is the low-fraction gas condensate (S22), which flows to the low-pressure separator (V03) by gravity and mixes with the flash liquid in the tank to form the low-fraction liquid (S25). The dry low-fraction gas (S23) is then sent to purification process B (X02).

[0113] The hydrogenation reaction liquid product consisting of high-fraction condensate and low-fraction condensate is subjected to continuous distillation through a series of distillation towers to separate the ester hydrogenation product into various components or target products, including ethanol, cyclohexanol, light and heavy impurities generated by side reactions, and unreacted cyclohexyl acetate.

[0114] For the purification process A (X01) of dry off gas, the hydrogen volume concentration of dry off gas (S13) is above 90%, and the volume flow rate is 268.8Nm 3 / h, gas absorption tower process, the operating pressure of the absorption tower is 4.7-4.9MPaG, the absorption liquid is the distillate from the top of the alcohol tower, the composition is cyclohexanol containing cyclohexanone (mass fraction is 3%), the flow rate is 100kg / h, and the absorption liquid is cooled to 25°C and added from the top of the absorption tower, and contacts with the dry purge gas entering from the bottom of the absorption tower in the tower, and mass transfer and heat transfer occur. The tower bottom obtains the absorption rich liquid absorbing ethanol and the like, and the top of the tower obtains the pure purge gas (S14) with the ethanol and cyclohexanol contents not higher than 25ppm (Vol) and 50ppm (Vol), respectively. The pure purge gas (S14) is sent to the cyclohexane hydrorefining unit.

[0115] For the purification process B (X02) of dry low fraction gas, the hydrogen volume concentration of dry low fraction gas (S23) is about 80%, and the volume flow rate is 100Nm 3 / h, gas absorption tower process, the operating pressure of the absorption tower is 0.7-0.8MPaG, the absorption liquid is the distillate from the top of the alcohol tower, the composition is cyclohexanol containing cyclohexanone (mass fraction is 3%), the flow rate is 300kg / h, and the absorption liquid is cooled to 25°C and added from the top of the absorption tower. It contacts with the dry low-fraction gas entering from the bottom of the absorption tower in the tower, and mass transfer and heat transfer occur. The tower bottom obtains the absorption rich liquid that absorbs organic matter such as ethanol, and the top of the tower obtains pure low-fraction gas (S24) with ethanol and cyclohexanol contents not higher than 150ppm (Vol) and 300ppm (Vol), respectively. The pure low-fraction gas (S24) is sent to the cyclohexanol dehydrogenation unit.

[0116] The hourly hydrogen consumption of the hydrogenation reaction in this unit is 6300Nm 3 / h, of which the amount of new hydrogen from outside the boundary area is 3142.5Nm 3 / h, and the recycled hydrogen from the cyclohexanol dehydrogenation unit is 3157.5Nm 3 / h.

[0117] The unit emits tail hydrogen:

[0118] The pure exhaust gas flow rate is 268.8Nm 3 / h, containing 0.01kg / h of ethanol and 0.06kg / h of cyclohexanol.

[0119] Exhaust pure low-pressure gas, flow rate is 100.0Nm 3 / h, containing 0.03kg / h of ethanol and 0.13kg / h of cyclohexanol.

[0120] The amount of dissolved gas discharged is 50Nm 3 / h, containing 2.5kg / h of ethanol.

[0121] 4) Cyclohexanol dehydrogenation unit

[0122] The cyclohexanol obtained from the top of the alcohol column and / or the refined cyclohexanol from the cyclohexanol storage tank is subjected to heat exchange in a series of heat exchangers and evaporated in an evaporator to obtain gaseous alcohol. The gaseous alcohol is then heated to 220-240°C before entering a tube-in-tube fixed-bed dehydrogenation reactor. Under the catalysis of a zinc-copper catalyst, the alcohol is dehydrogenated to produce cyclohexanone and hydrogen. The reaction temperature is 220-240°C, the reaction pressure is slightly positive, the single-pass conversion rate of cyclohexanol is 50%, and the selectivity of cyclohexanone is 99%. The reaction is endothermic, and heat is provided to the reactor by heat transfer oil to maintain the required reaction temperature. The effluent from the dehydrogenation reactor is cooled and condensed through multiple heat exchanges to obtain liquid crude cyclohexanone and cyclohexanol crude alcohol-ketone liquid and gas mainly composed of by-product hydrogen; the by-product hydrogen of this unit, the tail hydrogen discharged from the benzene selective hydrogenation unit, and the pure low-fraction gas from the cyclohexyl acetate hydrogenation unit are mixed in the hydrogen compressor inlet buffer tank and then enter the hydrogen compressor. The compressor outlet pressure is 5.5 MPaG. The compressed hydrogen is cooled to 12°C in a hydrogen cooler and then separated to obtain recycled hydrogen. The recycled hydrogen contains a small amount of water, impurities such as benzene, cyclohexene, cyclohexane, cyclohexanone and cyclohexanol, and does not contain harmful components such as sulfides and nitrides, and is sent to the cyclohexyl acetate hydrogenation unit.

[0123] The amount of hydrogen produced by the dehydrogenation reaction in this unit is 2875Nm 3 / h;

[0124] The amount of tail hydrogen discharged from the benzene selective hydrogenation unit: 187.5Nm 3 / h;

[0125] Pure low-gas volume from cyclohexyl acetate hydrogenation unit: 100 Nm3 / h;

[0126] The amount of recycled hydrogen sent from this unit to the cyclohexyl acetate hydrogenation unit: 3157.5Nm 3 / h.

[0127] 5) Cyclohexane hydrorefining unit

[0128] Cyclohexane is a byproduct of the selective hydrogenation of benzene in the benzene selective hydrogenation unit and is separated from the cyclohexene addition esterification unit. After deacidification and dehydration, the qualified cyclohexane is preheated to 100°C in a feed heater and fed to the top of the cyclohexane hydrogenation reactor. In a trickle bed reactor, small amounts of benzene, cyclohexene, and methylcyclopentene in the cyclohexane are completely hydrogenated to the corresponding saturated alkanes. Using a nickel catalyst, the reaction temperature is 100-120°C, and the reaction pressure is 1.5-2.0 MPaG. A one-pass hydrogenation process is employed. Hydrogen and oil-phase cyclohexane are added from the top of the reactor, and hydrogenation tail gas is continuously discharged from the bottom of the reactor to prevent the accumulation of inert gases. The hydrogenation reaction product is also discharged from the bottom of the reactor and distilled in a cyclohexane refining tower. A light oil containing methylcyclopentane and other components is fractionated from the top of the tower, and the target product cyclohexane is obtained in the bottom of the tower. The resulting refined cyclohexane has a purity of no less than 99.9% by weight, with benzene and cyclohexene contents both less than 100 ppm. The hydrogen-containing tail gas discharged from the bottom of the reactor and the dissolved hydrogen and light components discharged from the tail gas condenser of the cyclohexane refining tower are all discharged into the fuel pipeline network.

[0129] The hydrogen for this unit reaction comes from the treated purge gas of the cyclohexyl acetate hydrogenation unit in the device, with a flow rate of 268.8 Nm 3 / h.

[0130] The tail hydrogen emission of this unit is: 193.8Nm 3 / h, of which cyclohexane 5.30kg / h is discharged to the fuel pipeline network.

[0131] Comparative Example 1

[0132] The production scale, unit composition, main process flow of each unit, raw materials and specifications of Comparative Example 1 are the same as those of Example 1. The main differences are described below.

[0133] 1) Benzene selective hydrogenation unit

[0134] The process and process conditions are the same as those in Example 1; the new hydrogen also comes from outside the boundary area, and the flow rate is also the same as in Example 1; this unit discharges tail hydrogen with a hydrogen content of 95% (Vol) and a flow rate of 187.5Nm 3 / h, which is also the same as in Example 1.

[0135] Different from Example 1:

[0136] This unit emits tail hydrogen, which is centrally processed by the hydrogen recovery device.

[0137] 2) Cyclohexene esterification unit

[0138] Exactly the same; this unit does not involve hydrogen utilization.

[0139] 3) Cyclohexyl acetate hydrogenation unit

[0140] The overall process and operating conditions are the same, except for the following differences from Example 1:

[0141] The hourly hydrogen consumption of the hydrogenation reaction in this unit is 6300Nm 3 / h, all new hydrogen from outside the boundary area (6300Nm 3 / h).

[0142] The "dry off-gas" obtained through the same process and operating conditions is discharged to a hydrogen recovery device without being treated by a gas absorption process.

[0143] The "dry low-fraction gas" obtained through the same process and operating conditions is discharged to the fuel pipeline network without being treated by the gas absorption process.

[0144] The unit emits tail hydrogen:

[0145] The pure exhaust gas flow rate is 268.8Nm 3 / h, containing 0.27kg / h of ethanol and 0.03kg / h of cyclohexanol.

[0146] Exhaust pure low-pressure gas, flow rate is 100.0Nm 3 / h, containing 0.63kg / h of ethanol and 0.07kg / h of cyclohexanol.

[0147] The amount of dissolved gas discharged is 50Nm 3 / h, containing 2.5kg / h of ethanol.

[0148] 4) Cyclohexanol dehydrogenation unit,

[0149] The process and operating conditions of this unit are exactly the same as those of the corresponding unit in Example 1. The difference is that this unit does not compress or cool the hydrogen used in other units. The by-product hydrogen in this unit is treated according to the process and conditions described in Example 1 and then sent to the hydrogen recovery unit.

[0150] By-product hydrogen volume of this unit: 2825Nm 3 / h;

[0151] The amount of hydrogen sent to the hydrogen recovery device by this unit: 2825Nm 3 / h, of which cyclohexanol + cyclohexanone is about 2.2kg / h.

[0152] 5) Cyclohexane hydrorefining unit

[0153] The process and operating conditions of this unit are exactly the same as those of the corresponding unit in Example 1, the difference being the source of hydrogen for the hydrogenation reaction.

[0154] Hydrogen consumption of hydrogenation reaction in this unit: 150Nm 3 / h, all from new hydrogen outside the boundary area (150Nm 3 / h);

[0155] The tail hydrogen emission of this unit is: 75Nm 3 / h, of which 2.15kg / h of cyclohexane is discharged into the fuel pipeline network.

[0156] The main parameters of Example 1 and Comparative Example 1 are compared in Table 1. It can be seen from Table 1 that after adopting the invention technology, the tail hydrogen or by-product hydrogen discharged from the 100,000 tons per year cyclohexanone device is processed at a low cost, and the hydrogen is circulated or cascaded in the device, without the need to convert 3326Nm 3 / h hydrogen is sent to the factory hydrogen recovery unit for treatment. The hydrogen recovered by the hydrogen recovery unit is regenerated and the hydrogen released by the analysis is about 3326*20%=665Nm 3 / h, gas is charged at 1 yuan / Nm 3 According to calculations, this item alone can save approximately 5.32 million yuan annually.

[0157] Table 1 Comparison of main parameters between Example 1 and Comparative Example 1

[0158]

[0159] The above description is merely an embodiment of the present application and does not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, it is not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A hydrogen comprehensive utilization system in a cyclohexanone esterification process device, mainly consisting of a benzene selective hydrogenation unit, a cyclohexene esterification addition unit, a cyclohexyl acetate hydrogenation unit, a cyclohexane hydrorefining unit, and a cyclohexanol dehydrogenation unit, characterized in that: The new hydrogen feed pipe is connected to the benzene selective hydrogenation unit and the cyclohexyl acetate hydrogenation unit respectively, and the benzene selective hydrogenation unit is connected to the cyclohexene esterification addition unit; the cyclohexyl acetate pipeline of the cyclohexene esterification addition unit is connected to the cyclohexyl acetate hydrogenation unit, and the crude cyclohexane pipeline is connected to the cyclohexane hydrorefining unit; the cyclohexanol pipeline of the cyclohexyl acetate hydrogenation unit is connected to the cyclohexanol dehydrogenation unit, the purge gas pipeline of the cyclohexyl acetate hydrogenation unit is connected to the cyclohexane hydrorefining unit, and the parsed gas pipeline of the cyclohexyl acetate hydrogenation unit is connected to the factory fuel pipeline network; the tail hydrogen discharge pipeline of the cyclohexane hydrorefining unit is connected to the factory fuel pipeline network; the tail hydrogen discharge pipeline of the benzene selective hydrogenation unit, the by-product hydrogen pipeline of the cyclohexanol dehydrogenation unit, and the pure low-fraction gas pipeline of the cyclohexyl acetate hydrogenation unit are mixed before the inlet of the hydrogen compressor, and the hydrogen outlet pipeline of the hydrogen compressor is connected to the cyclohexyl acetate hydrogenation unit; The cyclohexyl acetate hydrogenation unit is composed of a hydrogenation reactor, a feed heat exchanger, a feed heater, a high-gas cooler, a purge gas cooler, a low-gas cooler, a high-pressure separator, a high-pressure condensate tank, a low-pressure separator, a circulating hydrogen compressor, a purge gas purifier, and a low-gas purifier; A feed pipeline for a mixture of cyclohexyl acetate and circulating hydrogen is connected to a hydrogenation reactor; a hydrogenation reactor effluent pipeline is connected to a hot side inlet of a feed heat exchanger, which is connected to a high-pressure separator; a high-pressure separator tank is provided with a high-fraction liquid outlet, and a high-fraction gas outlet mainly composed of hydrogen is provided on the top; the high-fraction gas outlet is connected to a high-fraction gas cooler, which is connected to a high-pressure condensate tank; a high-fraction condensate outlet mainly composed of ethanol is provided at the bottom of the high-pressure condensate tank, and a cold high-fraction gas outlet is provided on the top of the high-pressure condensate tank, which is connected to a circulating hydrogen compressor; new hydrogen and recycled hydrogen pipelines are connected to a circulating hydrogen pipeline at the inlet of a circulating hydrogen compressor, and then to the inlet of a circulating hydrogen compressor, and the outlet of the circulating hydrogen compressor is connected to a cyclohexyl acetate feed pipeline, and then to the cold side inlet of a feed heat exchanger, and the cold side outlet of the feed heat exchanger is connected to a feed heater, and the outlet of the feed heater is connected to the hydrogenation reactor; The top of the high-pressure condensate tank is also provided with a purge gas outlet connected to the purge gas cooler, the gas phase outlet of the purge gas cooler is connected to the purge gas purification facility, and the liquid phase outlet of the purge gas cooler is connected to the high-pressure condensate tank.

2. A process for comprehensive utilization of hydrogen in a cyclohexanone esterification process device, The hydrogen source for the benzene selective hydrogenation unit is fresh hydrogen supplied from outside; The exhaust hydrogen from the benzene selective hydrogenation unit, the by-product hydrogen from the cyclohexanol dehydrogenation unit, and the pure low-fraction gas from the cyclohexyl acetate hydrogenation unit are mixed before the hydrogen compressor inlet, compressed, cooled, and separated to obtain recycled hydrogen, which is then sent to the cyclohexyl acetate hydrogenation unit. The hydrogen source of the cyclohexyl acetate hydrogenation unit adopts the recycled hydrogen, and the insufficient part is supplemented by new hydrogen supplied from outside; The purge gas from the cyclohexyl acetate hydrogenation unit is sent to the cyclohexane hydrorefining unit after process treatment; The hydrogen source for the cyclohexane hydrorefining unit is the pure purge gas obtained by treatment in the cyclohexyl acetate hydrogenation unit; The tail hydrogen discharged from the cyclohexane hydrotreating unit is sent to the factory fuel pipeline network or hydrogen recovery device; The reaction effluent of the hydrogenation reactor of the cyclohexyl acetate hydrogenation unit is heat exchanged with the reaction feed, cooled to 100-180° C., and then enters a high-pressure separator for gas-liquid separation at a pressure close to the hydrogenation reaction pressure to obtain high-fraction gas and high-fraction liquid; the high-fraction gas is cooled and enters a high-pressure condensate tank for gas-liquid separation again at a pressure close to the operating pressure of the high-pressure separator to obtain cold high-fraction gas and high-fraction condensate; the cold high-fraction gas is divided into two paths: one path enters a circulating hydrogen compressor for pressure boosting and circulation back to the hydrogenation reactor, and the other path is purge gas; The high-fraction liquid enters the low-pressure separator for flash evaporation, and the gas-liquid separation obtains the gas as the low-fraction gas and the liquid as the low-fraction liquid; The high fraction condensate and low fraction condensate are further separated and refined in the cyclohexane hydrorefining unit; The purge gas is further cooled and subjected to gas-liquid separation to obtain "dry purge gas", which is then treated in purification process A to obtain "pure purge gas", which is directly sent to the cyclohexane hydrorefining unit without pressurization; The low-fraction gas is further cooled and subjected to gas-liquid separation to obtain "dry low-fraction gas", which is then treated by purification process B to obtain "pure low-fraction gas" and sent to the hydrogen compressor inlet of the cyclohexanol dehydrogenation unit.

3. The process according to claim 2, characterized in that The hydrogen gas volume fraction in the new hydrogen is greater than 95%.

4. The process according to claim 2, wherein: The gas separated by flash evaporation from the hydrogenation reactor of the benzene selective hydrogenation unit is cooled and separated to obtain discharged tail hydrogen with a pressure of 0.3-0.8 MPa and a temperature of 10-30° C., which is then sent to a hydrogen compressor.

5. The process according to claim 2, wherein: The reaction effluent of the dehydrogenation reactor of the cyclohexanol dehydrogenation unit is subjected to heat exchange, cooling and liquid separation to obtain by-product hydrogen; the recycled hydrogen has a temperature of 10-45°C; the recycled hydrogen is connected to the circulating hydrogen system in the cyclohexyl acetate hydrogenation unit, and can be connected to the circulating hydrogen system before the hydrogen inlet or after the hydrogen outlet of the circulating hydrogen compressor.

6. The process according to claim 2, characterized in that The pressure difference between the operating pressure of the cyclohexyl acetate hydrogenation reactor and the operating pressure of the high-pressure separator is not greater than 0.5 MPa; the pressure difference between the operating pressure of the high-pressure separator and the operating pressure of the high-pressure condensate tank is not greater than 0.5 MPa; the flash pressure of the low-pressure separator is 0.4-1.2 MPa; the temperature of the high-fraction gas after cooling is 20-60°C; the purge gas is further cooled to 10-40°C; the low-fraction gas is further cooled to 10-40°C.

7. The process according to claim 2, characterized in that The purification process A and the purification process B are one or a combination of an adsorption process and a gas absorption process; in the gas absorption process, one and / or a mixture of cyclohexanone, cyclohexanol, and cyclohexyl acetate is used as the absorption liquid, which contacts with the purge gas or low-fraction gas in the absorption tower to absorb most of the organic matter in the gas and become an absorption-rich liquid.

8. The process according to claim 7, characterized in that The absorption rich liquid discharged from the gas absorption process is returned to the corresponding refining facilities of the cyclohexane hydrorefining unit for treatment.

9. The process according to claim 7, characterized in that The pure purge gas has a hydrogen purity of more than 90%, and the ethanol and cyclohexanol contents thereof do not exceed 25ppm and 50ppm respectively; the pure low-concentration gas has an ethanol and cyclohexanol contents not exceeding 150ppm and 300ppm respectively.

Images