Process method for preparing cyclopentane through catalytic hydrogenation of cyclopentene

Abstract

The invention belongs to the technical field of preparation of cyclopentane, and particularly relates to a process method for preparing cyclopentane through catalytic hydrogenation of cyclopentene. Comprising the following steps: S1, light component removal; s2, refining the cyclopentene; s3, full hydrogenation; s4, extractive distillation; s5, desorption is carried out; and S6, refining the extraction agent. A liquid material enters from the upper part of a full hydrogenation reactor, and hydrogen enters from four sides of an upper seal head of the reactor, and then enters a catalyst bed layer after being fully mixed with the hydrogen and the liquid material at the upper part of the reactor to complete mass transfer. By adopting the independently designed hydrogenation reactor, the olefin conversion rate can reach 99.9%. The cyclopentene product tower bottom material is used for hydrogenation reaction, so that the raw material utilization rate is increased; in a fixed bed reactor, carrying out hydrogenation reaction by using a nickel catalyst to prepare cyclopentane; according to the method, cyclopentene is converted into cyclopentane through hydrogenation reaction, and new hexane is separated through extractive distillation, so that high-purity cyclopentane is prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of cyclopentane preparation, and particularly relates to a process for catalytic hydrogenation of cyclopentene to prepare cyclopentane. Background Art

[0002] Cyclopentane is a cycloalkane and an organic compound with the molecular formula C5H10. It is a colorless and transparent liquid, insoluble in water, and soluble in most organic solvents such as ethanol, ether, benzene, carbon tetrachloride, acetone, etc. It is mainly used as a solvent and a standard substance for chromatographic analysis. The cyclopentane series of green new materials are a class of chemical materials with environmental protection characteristics, having low environmental impact and good sustainability characteristics. Therefore, in the current industrial research field, it is regarded as an important development direction. Especially in the fields of chemical engineering, materials science, and environmental protection, the research and development of cyclopentane series of green materials have far-reaching significance. Cyclopentane is mainly used in the refrigerator, freezer, and cold storage industries and pipeline insulation, etc., as a foaming agent for rigid polyurethane foam. Its ozone layer depletion potential and global warming potential are both zero, making it a new type of environmentally friendly foaming agent. Due to the absence of chlorine and fluorine, it has also been used as a refrigerant in recent years to replace the chlorine-containing and fluorine-containing refrigerants.

[0003] Currently, the methods for producing cyclopentane are roughly divided into two categories: The first category is to separate cyclopentane from the mixture, and the second category is to produce it by hydrogenation of cyclopentadiene. The first category of methods for producing cyclopentane is a relatively common method. However, since the boiling points of 2,2-dimethylbutane and cyclopentane in the mixture are close, separation is difficult, and the purity of the cyclopentane product obtained by ordinary distillation is difficult to reach above 99.8%. Moreover, when the content of 2,2-dimethylbutane is relatively high, the mass fraction of cyclopentane will even be less than 95%, failing to meet the cyclopentane quality index in "Industrial Cyclopentane" GB / T 18825-2002. For the second category of methods for producing cyclopentane, the product purity is relatively high. However, due to the special chemical properties and flammability and explosiveness of cyclopentadiene, strict safety measures must be adopted when using cyclopentadiene, resulting in high production costs and large losses. Moreover, when directly hydrogenating cyclopentadiene to produce cyclopentane, the service life of the hydrogenation catalyst is short and the cost is high. Patents CN1321625A, CN1911875A, CN102399121A, and CN104326856A all adopt the second category of methods.

[0004] There have been research reports on the hydrogenation of cyclopentadiene to prepare cyclopentane in China, but there is no mention of using the bottom material of the cyclopentene product tower for hydrogenation reaction to prepare cyclopentane; there have been research reports on the method of separating cyclopentane and neohexane by extractive distillation process in China, but it is not mentioned that the cyclopentane / neohexane mixed system is obtained by hydrogenation reaction of cyclopentene.

[0005] Based on this, we have proposed a process for catalytic hydrogenation of cyclopentene to prepare cyclopentane, hoping to solve the deficiencies in the existing technology. Summary of the Invention

[0006] The object of the present invention is to provide a process for the catalytic hydrogenation of cyclopentene to prepare cyclopentane in view of the existing problems.

[0007] The present invention is achieved by the following technical solutions:

[0008] A process for the catalytic hydrogenation of cyclopentene to prepare cyclopentane, comprising the following steps:

[0009] S1. Light component removal:

[0010] The crude cyclopentene material is added to a light component removal rectification column for rectification, and the bottom product is the treated crude cyclopentene for the next step of cyclopentene purification.

[0011] S2. Cyclopentene purification:

[0012] The crude cyclopentene material after light component removal is pumped to a cyclopentene rectification column for continuous rectification. The overhead product is the cyclopentene product, which is filled into barrels for storage.

[0013] The bottom material is the crude cyclopentane material containing a small amount of cyclopentene, which is pumped to the full hydrogenation process for full hydrogenation reaction.

[0014] S3. Full hydrogenation:

[0015] The crude cyclopentane material is added to a hydrogenation raw material tank, and then pumped to a hydrogenation preheater for heating. The heated crude cyclopentane material and hydrogen enter a mixer for mixing and then enter a hydrogenation reactor for full hydrogenation.

[0016] S4. Extractive distillation:

[0017] The hydrogenation reaction product and the extractant are respectively added to an extractive distillation column for extractive distillation. The bottom product component is the extractant containing cyclopentane, which is sent to a desorption column for the next separation of cyclopentane and the extractant.

[0018] S5. Desorption:

[0019] The bottom liquid of the above extractive distillation column enters the desorption column, and cyclopentane product is rectified out. The outlet component is the extractant for recycling, which is returned to the extractive distillation column for recycling after heat exchange.

[0020] S6. Extractant purification:

[0021] The recycled extractant from the bottom of the above desorption column is purified after recycling. The extractant to be purified is sent to an extractant purification column for vacuum rectification, and the extractant is distilled out from the top of the column.

[0022] Further preferably, in step S1, the bottom temperature during light component removal is controlled at 55 - 70 °C, and the top temperature is controlled at 55 - 70 °C.

[0023] Further preferably, when refining cyclopentene in step S2, the temperature at the bottom of the column is controlled at 55.6 - 62.4 °C, and the temperature at the top of the column is controlled at 55.6 - 62.4 °C.

[0024] Further preferably, when the preheater is heating in step S3, it is heated to 160 - 220 °C. For the full hydrogenation, the flow is from top to bottom, with an excessive amount of hydrogen. The temperature of the hydrogenation catalyst bed layer is controlled at 190 - 260 °C, and the liquid-phase volume space velocity is controlled at 1.0 h -1 , the system pressure is controlled at 2.8 MPa, and the hydrogen-oil ratio is controlled at 2.0 - 8.0.

[0025] Further preferably, when performing extractive distillation in step S4, the operating temperature at the top of the column is controlled at 49.6 - 81.6 °C, and the operating temperature at the bottom of the column is 49.6 - 81.6 °C.

[0026] Further preferably, when performing rectification in the desorption column in step S5, the temperature at the top of the column is controlled at 52.3 - 158.1 °C, and the temperature at the bottom of the column is controlled at 52.3 - 158.1 °C.

[0027] Further preferably, when refining the extractant in step S6, the operating pressure is controlled at -0.09 - -0.06 MPa, the temperature at the top of the column is controlled at 82.8 - 94.6 °C, and the temperature at the bottom of the column is controlled at 82.8 - 94.6 °C.

[0028] Further preferably, the catalyst used for the full hydrogenation in step S3 is a nickel-based catalyst;

[0029] The preparation of the nickel-based catalyst includes the following steps:

[0030] (1) Immerse silica in a modifier, immerse the ultrasonic probe 3 - 5 cm below the liquid surface of the treating agent, perform ultrasonic treatment, and at the same time perform electron beam irradiation treatment. After treating for 1 - 3 h, filter and wash with deionized water 3 - 5 times, and then place it in a vacuum drying oven to dry at 40 - 50 °C for 5 - 8 h to obtain modified silica;

[0031] (2) Dissolve chitosan in a 1% dilute acetic acid solution, then add allyl methyl dimethoxysilane with a mass 0.3 - 0.6 times that of chitosan, stir and mix evenly, and perform a reflux reaction at 80 - 90 °C and 300 - 400 rpm for 10 - 12 h, then adjust the pH to 7. Then add modified silica with a mass 2 - 3 times that of chitosan, stir and mix evenly, adjust the pH to 12 - 13 with NaOH, continue stirring for 1 - 2 h, then filter and wash with deionized water 3 - 5 times, and place it in a vacuum drying oven to dry at 40 - 50 °C for 5 - 8 h to obtain the catalyst support for standby;

[0032] (3) Add NiSO4·6H2O to distilled water to prepare an aqueous solution of Ni 2+ with a concentration of 0.1 mol·L -1 While stirring, add the above catalyst support to the NiSO4·6H2O aqueous solution. After stirring at 400 - 600 rpm for 5 - 6 h, under nitrogen protection, slowly add the KBH4 solution dropwise while stirring at 100 - 200 rpm. After the reaction is completed, perform suction filtration, wash with water until neutral, then wash 3 - 5 times with absolute ethanol and store in absolute ethanol. When in use, dry to constant weight under nitrogen protection.

[0033] Further preferably, the components and their corresponding weight percentages in the treatment agent in step (1) are: 2 - 3% of γ-aminopropyltriethoxysilane, 2 - 3% of tannic acid, 5 - 6% of sodium dodecylbenzenesulfonate, and the balance is absolute ethanol.

[0034] The dose of electron beam irradiation treatment is 7 - 10 kGy.

[0035] Further preferably, the concentration of the KBH4 solution in step (4) is 2 - 3 mol·L -1 , and the dropping rate is 9 - 10 mL·min -1 .

[0036] Step S3 also includes obtaining cyclopentane containing a small amount of other C5 impurities and unreacted hydrogen after full hydrogenation. After passing through the hydrogenation reaction outlet cooler, it enters the hydrogenation material gas-liquid separation tank for separation. The liquid material after gas-liquid separation is controlled by a liquid level regulating valve to enter the buffer tank for hydrogenated material, and then is pumped to the extractive distillation process by a pump;

[0037] The gas after gas-liquid separation enters the hydrogen recycling and pressurizing system. After secondary gas-liquid separation and compression by a hydrogen compressor, it returns to the feed for recycling.

[0038] The present invention has the following advantages compared with the prior art:

[0039] 1. Compared with the existing domestic process technology route, in the present invention, the liquid material enters from the upper part of the full hydrogenation reactor, and hydrogen enters from four sides of the upper head of the reactor. Then, after the hydrogen and the liquid material are fully mixed in the upper part of the reactor to complete mass transfer, they enter the catalyst bed layer. By using a self-designed hydrogenation reactor, the olefin conversion rate can reach 99.9%. The process route of the present invention improves the utilization category of raw materials and at the same time improves the product quality, and is more suitable for industrial production compared with the existing domestic process technology route.

[0040] 2. The present invention utilizes the bottom material of the cyclopentene product column to carry out a hydrogenation reaction, improving the raw material utilization rate; in a fixed-bed reactor, a nickel-based catalyst is used for the hydrogenation reaction to prepare cyclopentane; cyclopentene is converted into cyclopentane through the hydrogenation reaction, and then neohexane is separated by extractive distillation to prepare high-purity cyclopentane.

[0041] 3. The present invention adopts a special nickel-based catalyst, which has advantages such as a large specific surface area, a reasonable pore structure distribution, and a high dispersion degree, and shows good activity in the hydrogenation reaction. In the preparation of the catalyst, first, silica is immersed in a treating agent, and then the combined action of ultrasonic waves and electron beams acts on the silica to improve the surface activity, increase the dispersion degree, and prevent its agglomeration. Allyl methyl dimethoxysilane is grafted onto the surface of chitosan to improve the compatibility between chitosan and the subsequent silica, increase the dispersion degree, and prevent agglomeration. At this time, the two are combined to obtain a catalyst support with multiple active sites, stable chemical properties, and good dispersion. Finally, an amorphous alloy catalyst prepared by the impregnation method is used, and Ni-B is uniformly dispersed on the surface of the support. The catalyst support significantly enhances the charge deficiency of Ni atoms, thereby promoting the adsorption effect of the active component Ni on the electron-rich C═C, enabling the catalyst to maintain extremely strong hydrogenation activity during the reaction process, and thus significantly improving the efficiency of the hydrogenation reaction. In addition, the catalyst of the present application has good chemical stability and can be reused repeatedly, greatly reducing the production cost. In addition, the present invention not only provides a process idea for the catalytic hydrogenation of cyclopentene to prepare cyclopentane, but the catalyst provided by it can be used in multiple fields and has good additional value. Brief Description of the Drawings

[0042] Figure 1 is the process flow chart of the present invention;

[0043] Figure 2 is the chromatogram of the cyclopentene product;

[0044] Figure 3 is the chromatogram of the cyclopentane product. Detailed Embodiments

[0045] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0046] Sample analysis conditions:

[0047] The analytical instrument is a Shimadzu GC-2010PRO gas chromatograph, and the correction area normalization method is used for quantification. A hydrogen flame ionization detector is adopted, and the chromatographic analysis conditions are as follows: The chromatographic column is an HP-1 capillary column; the initial column temperature: 25°C; the retention time is 15 min; the heating rate: 15°C / min to 180°C and then hold for 12 min; the inlet temperature: 25°C; the detector temperature: 250°C; the hydrogen flow rate: 40 ml / min; the nitrogen flow rate: 30 ml / min; the air flow rate: 400 ml / min.

[0048] The tests of the present invention are divided into pilot tests and semi-pilot tests.

[0049] Example 1

[0050] Pilot test

[0051] A process for preparing cyclopentane by catalytic hydrogenation of cyclopentene includes the following steps:

[0052] 1.1 Light component removal unit

[0053] The crude cyclopentene material is added to the light component removal rectification column, and atmospheric pressure batch rectification is carried out. The bottom temperature is controlled at 55 - 70°C, the top temperature is controlled at 55 - 70°C, and the bottom product is the treated crude cyclopentene for the next step of cyclopentene refining. The specific experimental results are shown in Table 1 below.

[0054] Table 1 Light component removal data

[0055] Batch 2-Pentene (%) Cyclopentene (%) Cyclopentane (%) Neohexane (%) Feedstock 0.07 67.97 31.76 0.19 Top-collected liquid 17.73 80.03 1.22 / Bottom-collected liquid / 69.13 28.39 2.34

[0056] 1.2 Cyclopentene refining unit

[0057] The crude cyclopentene material after light component removal is added to the cyclopentene rectification column, and atmospheric pressure batch rectification is carried out. The bottom temperature is controlled at 55.6 - 62.4°C, the top temperature is controlled at 55.6 - 62.4°C, the top product is the cyclopentene product, and the bottom material is the crude cyclopentane material containing a small amount of cyclopentene, which is sent to the full hydrogenation unit for full hydrogenation reaction. The specific experimental data are shown in Table 2 below.

[0058] Table 2 Cyclopentene refining data

[0059] Batch Cyclopentene (%) Cyclopentane (%) Neohexane (%) Feedstock 69.13 28.39 2.34 Top-collected liquid 99.5 0.28 / Bottom-collected liquid 15.02 78.57 6.60

[0060] 1.3 Full hydrogenation unit

[0061] The hydrogenation reaction is an exothermic reaction, accompanied by a temperature rise during the reaction. Temperature and hydrogen-oil ratio have great effects on the reaction. Increasing the heating temperature promotes the forward progress of the reaction; increasing the hydrogen-oil ratio enables the cyclopentene in the raw material to fully contact and react with hydrogen, making the reaction more complete. During the experiment, by controlling the temperature, hydrogen-oil ratio, and space velocity, the conversion rate of cyclopentene was observed. The crude cyclopentane material was added to the hydrogenation raw material tank and then pumped to the hydrogenation preheater to be heated to 160 - 220 °C. The heated crude cyclopentane material and hydrogen entered the mixer simultaneously, and after mixing, they entered the hydrogenation reactor for full hydrogenation, with the material flowing in from the top and out from the bottom, and with excess hydrogen. The bed temperature of the hydrogenation catalyst was controlled not to exceed 260 °C, and the liquid hourly space velocity was controlled at 1.0 h -1 , the system pressure was controlled at 2.8 MPa, and the hydrogen-oil ratio was controlled at 2.0 - 8.0. Before the reaction started, the catalyst was activated with high-temperature H2.

[0062] 1.3.1 Influence of Temperature on Full Hydrogenation Reaction

[0063] The main purpose of the experiment was to use the hydrogenation catalyst to hydrogenate cyclopentene to produce cyclopentane. The hydrogenation reaction rate is related to temperature. The hydrogenation reaction is an exothermic reaction, accompanied by a temperature rise during the reaction. Increasing the reaction temperature can promote the reaction process, making the reaction more complete and further increasing the conversion rate. The heating temperature range in this experiment was 160 - 220 °C, the liquid hourly space velocity was 1.0 h -1 ; the hydrogen-oil ratio was 4.0; the reaction pressure was 2.8 MPa. The specific experimental data are shown in Table 3 below:

[0064] Table 3 Changes in the Content and Conversion Rate of Cyclopentene at Different Temperatures

[0065]

[0066]

[0067] It can be seen from Table 3 that as the temperature increases, the reaction rate accelerates, and the conversion rate of cyclopentene also gradually increases. The increase in temperature will increase the percentage of active molecules in the reaction, and the faster movement speed of the molecules makes the collisions between molecules more frequent and effective, further promoting the progress of the reaction. When the heating temperature is in the range of 160 - 220 °C, the conversion rate of cyclopentene shows a trend of first increasing and then leveling off. When the heating temperature reaches 190 °C, the conversion rate of cyclopentene can reach 99.9%.

[0068] 1.3.2 Influence of Hydrogen-Oil Ratio on Hydrogenation Reaction Performance

[0069] The conversion rate of the hydrogenation reaction is related to the hydrogen-oil ratio. When the hydrogen-oil ratio is low, the hydrogen flow rate is small and it cannot fully react with the cyclopentene in the raw material, resulting in a low conversion rate; when the hydrogen-oil ratio is high, the hydrogen flow rate is large, and the excessive hydrogen that has not reacted with the cyclopentene will increase the pressure and accelerate the liquid flow rate. Therefore, controlling the hydrogen-oil ratio is crucial for the experimental results. The range of the hydrogen-oil ratio in this experiment is 2.0 - 8.0, the heating temperature is 180 °C; the liquid-phase volume space velocity is 1 h -1 ; the reaction pressure is 2.8 MPa. The specific experimental data are shown in Table 4 below:

[0070] Table 4 Changes in the conversion rate and content of cyclopentene under different hydrogen-oil ratios

[0071] Hydrogen / oil ratio Cyclopentene (%) Cyclopentene conversion rate (%) 2.0 0.075 99.50 3.0 0.04 99.73 4.0 0.02 99.87 6.0 0.076 99.49 8.0 0.037 99.75

[0072] It can be seen from Table 4 that as the hydrogen-oil ratio increases, the conversion rate of cyclopentene shows a trend of first increasing and then decreasing. When the hydrogen-oil ratio is 4.0, the conversion rate of cyclopentene reaches the highest at 99.87%, and then continuing to increase the hydrogen-oil ratio, the conversion rate will slightly decrease. As the hydrogen-oil ratio rises, the hydrogen flow rate also increases, and the raw material can be more fully mixed and contacted with hydrogen, so that cyclopentene and hydrogen undergo a hydrogenation reaction. At the same time, the increase in the hydrogen flow rate will also promote the forward reaction and increase the conversion rate. When the hydrogen-oil ratio is further increased, at this time the hydrogen flow rate is too large, which may cause the residence time of hydrogen and cyclopentene in the raw material on the catalyst to be too short and the reaction time to be short, resulting in a decrease in the conversion rate.

[0073] 1.3.3 Summary of the full hydrogenation reaction

[0074] In this experiment, a catalyst was used to catalytically hydrogenate cyclopentene to cyclopentane. The experimental device used an adiabatic fixed-bed reactor, the feeding method was from top to bottom, and the reaction pressure was controlled at 2.8 MPa. The catalyst was loaded with a volume of 300 ml. Before the experiment, the catalyst was activated with high-temperature hydrogen. During the experiment, the experimental results were regulated by changing conditions such as temperature and hydrogen-oil ratio, and the content changes of each component in the product were observed to determine the optimal process conditions. From the experimental results, it can be seen that this catalyst can catalytically hydrogenate cyclopentene. Combining the experimental data, the recommended process for full hydrogenation is a heating temperature of 190 - 210 °C, a reaction pressure of 2.8 MPa, a liquid-phase volume space velocity of 1.0 h -1 , and a hydrogen-oil ratio of 4.0:1. At this time, the conversion rate of cyclopentene is above 99%.

[0075] 1.4 Extractive distillation unit

[0076] The hydrogenation reaction product and the extractant are separately added to an extractive distillation column for extractive distillation. The operating temperature at the top of the column is controlled at about 49.6 - 81.6 °C, and the operating temperature at the bottom of the column is about 49.6 - 81.6 °C. The bottom product composition is the extractant containing cyclopentane, which is sent to a desorption column for the next separation of cyclopentane and the extractant. The specific experimental results are shown in Table 5 below.

[0077] Table 5 Extractive Distillation Data

[0078] Batch DMF (%) Cyclopentane (%) Neohexane (%) Feedstock 86.86 12.12 0.96 Top-collected liquid / 10.97 88.79 Bottom-collected liquid 87.44 12.46 /

[0079] 1.5 Desorption Unit

[0080] The bottom liquid of the above extractive distillation column is fed into a desorption column for distillation. The top temperature is controlled at 52.3 - 158.1 °C, and cyclopentane product is distilled out. The bottom temperature is controlled at 52.3 - 158.1 °C, and the bottom product composition is the recycled extractant. The specific experimental results are shown in Table 6 below.

[0081] Table 6 Desorption Column Distillation Data

[0082] Batch DMF (%) Cyclopentane (%) Feedstock 87.44 12.46 Top-collected liquid / 98.86 Bottom-collected liquid 99.98 /

[0083] 1.6 Extractant Refining Unit

[0084] The recycled extractant at the bottom of the above desorption column needs to be purified after recycling for a period of time. The extractant to be purified is sent to an extractant refining column for vacuum distillation. The operating pressure is controlled at -0.09 - -0.06 MPa, the top temperature is controlled at 82.8 - 94.6 °C, and the extractant is distilled out from the top. The bottom temperature is controlled at 82.8 - 94.6 °C, and the bottom product composition is mainly heavy components. The specific experimental results are shown in Table 7 below.

[0085] Table 7 Extractant Refining Data

[0086]

[0087]

[0088] 1.7 Material Balance in Small-Scale Experiments

[0089] Table 8 Material Balance Table for Small-Scale Projects

[0090]

[0091] To sum up, the optimal process conditions for the hydrogenation reaction were determined in the small-scale experiments. The optimal process conditions for the hydrogenation reaction are: the heating temperature is 190 - 210 °C, the reaction pressure is 2.8 MPa, the liquid hourly space velocity is 1.0 h -1 , and the hydrogen-oil ratio is 4.0:1. At this time, the conversion rate of cyclopentene is above 99%.

[0092] Meanwhile, the process conditions of the rectification unit were determined through bench-scale experiments. According to the product analysis results, cyclopentene products meeting the enterprise standards and cyclopentane products meeting the national standards were obtained. The applicability of the process in industrial production was preliminarily evaluated through bench-scale experiments, the optimal process conditions were explored, and the production cost and safety were preliminarily evaluated, laying a foundation for the subsequent pilot-scale stage.

[0093] Example 2

[0094] Pilot-scale experiment

[0095] A process for preparing cyclopentane by catalytic hydrogenation of cyclopentene includes the following steps:

[0096] 2.1 Light component removal unit

[0097] The crude cyclopentene material enters the light component removal tower and is continuously rectified. The operating pressure is controlled at about 0.05 MPa (gauge pressure), the bottom temperature of the tower is controlled at 55.0 - 70.0 °C, the top temperature of the tower is controlled at 55.0 - 70.0 °C, and the bottom product is the treated crude cyclopentene which goes to the cyclopentene purification. The specific test results are shown in Table 9 below.

[0098] Table 9 Light component removal data

[0099] Batch 2-Pentene (%) Cyclopentene (%) Cyclopentane (%) Neohexane (%) Feedstock 0.06 66.97 32.76 0.18 Top-collected liquid 17.74 80.12 1.12 / Bottom-collected liquid / 69.27 28.25 2.36

[0100] 2.2 Cyclopentene purification unit

[0101] The crude cyclopentene material after light component removal is pumped to the cyclopentene rectification tower and is continuously rectified. The operating pressure is controlled at about 0.05 MPa (gauge pressure), the bottom temperature of the tower is controlled at 55.6 - 62.4 °C, the top temperature of the tower is controlled at 55.6 - 62.4 °C, and the top product is the cyclopentene product which is filled into barrels for storage. The bottom material is the crude cyclopentane material containing a small amount of cyclopentene and is pumped to the full hydrogenation process for full hydrogenation reaction.

[0102] Table 10 Cyclopentene purification data

[0103] Batch Cyclopentene (%) Cyclopentane (%) Neohexane (%) Feedstock 69.27 28.25 2.36 Top-collected liquid 99.5 0.32 / Bottom-collected liquid 14.91 78.48 6.61

[0104] 2.3 Full hydrogenation unit

[0105] The crude cyclopentane material enters the hydrogenation material buffer tank and then is pumped to the hydrogenation preheater to be heated to 160 - 220 °C. The heated crude cyclopentane material and hydrogen enter the mixer simultaneously and then enter the hydrogenation reactor for full hydrogenation. Hydrogen is in excess, the bed temperature of the hydrogenation catalyst is controlled at 190 - 260 °C, the liquid hourly space velocity is controlled at 1.0 h -1 ⁻¹, the system pressure is controlled at 2.8 MPa, and the hydrogen-oil ratio is controlled at 2.0 - 8.0. Before the reaction starts, the catalyst is activated with high-temperature H₂.

[0106] 2.3.1 Influence of Temperature on the Full Hydrogenation Reaction

[0107] The main purpose of the experiment is to use a hydrogenation catalyst to hydrogenate cyclopentene to form cyclopentane. The hydrogenation reaction rate is related to temperature. The hydrogenation reaction is an exothermic reaction, and the temperature rises during the reaction. Increasing the reaction temperature can promote the reaction process, making the reaction more complete and further increasing the conversion rate.

[0108] The heating temperature range for this experiment is 160 - 220 °C, the liquid hourly space velocity is 1.0 h -1 ; the hydrogen-oil ratio is 4.0; the reaction pressure is 2.8 MPa. The specific experimental data are as follows:

[0109] Table 11 Changes in the Conversion Rate and Content of Cyclopentene at Different Temperatures

[0110]

[0111]

[0112] It can be seen from Table 11 that as the temperature increases, the reaction rate accelerates, and the conversion rate of cyclopentene also gradually increases. The increase in temperature will increase the percentage of active molecules in the reaction, and the faster movement speed of the molecules makes the collisions between molecules more frequent and effective, further promoting the progress of the reaction. When the heating temperature is 160 - 220 °C, the conversion rate of cyclopentene shows a trend of first increasing and then leveling off. When the heating temperature reaches 190 °C, the conversion rate of cyclopentene can reach 99.9%.

[0113] 2.3. Influence of Hydrogen-Oil Ratio on the Performance of Hydrogenation Reaction

[0114] The conversion rate of the hydrogenation reaction is related to the hydrogen-oil ratio. When the hydrogen-oil ratio is low, the hydrogen flow rate is small, and it cannot completely react with the cyclopentene in the raw material, resulting in a low conversion rate; when the hydrogen-oil ratio is high, the hydrogen flow rate is large, and the excess hydrogen that has not reacted with cyclopentene will increase the pressure and accelerate the liquid flow rate. Therefore, controlling the hydrogen-oil ratio is crucial for the experimental results.

[0115] The hydrogen-oil ratio range for this experiment is 2.0 - 8.0, the heating temperature is 190 °C; the liquid hourly space velocity is 1 h -1 ; the reaction pressure is 2.8 MPa. The specific experimental data are as follows:

[0116] Table 12 Changes in the Conversion Rate and Content of Cyclopentene at Different Hydrogen-Oil Ratios

[0117] Hydrogen / oil ratio Cyclopentene (%) Cyclopentene conversion rate (%) 2.0 0.063 99.58 3.0 0.02 99.87 4.0 0.01 99.93 6.0 0.01 99.93 8.0 0.02 99.87

[0118] As can be seen from Table 12, as the hydrogen-oil ratio increases, the conversion rate of cyclopentene first increases and then decreases. When the hydrogen-oil ratio is 4.0, the conversion rate of cyclopentene reaches the highest at 99.9%, and then continues to increase the hydrogen-oil ratio, the conversion rate will slightly decrease. As the hydrogen-oil ratio increases, the flow rate of hydrogen also increases, and the raw materials can be more fully mixed and contacted with hydrogen, so that the hydrogenation reaction of cyclopentene and hydrogen occurs. At the same time, the increase in the hydrogen flow rate will also promote the forward reaction and increase the conversion rate. When the hydrogen-oil ratio is further increased, the hydrogen flow rate is too large at this time, which may cause the residence time of hydrogen and cyclopentene in the raw materials on the catalyst to be too short, and the reaction time is short, resulting in a decrease in the conversion rate.

[0119] 2.3.3 Summary of the full hydrogenation reaction

[0120] In this experiment, a catalyst was used to catalytically hydrogenate cyclopentene to cyclopentane. The reaction pressure was controlled at 2.8 MPa, and the catalyst was activated with high-temperature hydrogen before starting. During the experiment, the experimental results were regulated by changing conditions such as temperature and hydrogen-oil ratio, and the content changes of each component in the product were observed to determine the optimal process conditions. It can be seen from the experimental results that the catalyst can catalytically hydrogenate cyclopentene. Combining the experimental data, the recommended process for full hydrogenation is that the heating temperature is 190 - 210 °C, the catalyst bed temperature is 220.9 - 246.7 °C, the reaction pressure is 2.8 MPa, the liquid hourly space velocity is 1.0 h -1 , and the hydrogen-oil ratio is 4.0:1. At this time, the conversion rate of cyclopentene is above 99.9%.

[0121] 2.4 Extractive distillation unit

[0122] The above hydrogenation reaction liquid and extractant are respectively fed into the extractive distillation column for continuous extractive distillation. The top operating pressure is controlled at 0.002 MPa (gauge pressure), the top operating temperature is controlled at about 49.6 - 81.6 °C, the bottom operating temperature is about 49.6 - 81.6 °C, and the bottom discharge component is the extractant containing cyclopentane, which is pumped to the desorption column for separation of cyclopentane and extractant. The specific experimental results are shown in Table 13 below.

[0123] Table 13 Extractive distillation data

[0124] Batch DMF (%) Cyclopentane (%) Neohexane (%) Feedstock 86.70 12.31 0.99 Top-collected liquid / 10.97 88.79 Bottom-collected liquid 87.56 12.44 /

[0125] 2.5 Desorption unit

[0126] The bottom liquid of the above extractive distillation column is fed into the desorption column for continuous distillation. The operating pressure is controlled at 0.05 MPa (gauge pressure), the top temperature is controlled at 52.3 - 158.1 °C, and the cyclopentane product is distilled and filled into barrels for storage; the bottom temperature is controlled at 52.3 - 158.1 °C, and the discharge component is the recycled extractant, which is returned to the extractive distillation column for recycling after heat exchange. The specific experimental results are shown in Table 14 below.

[0127] Table 14 Desorption Tower Rectification Data

[0128] Batch DMF (%) Cyclopentane (%) Feedstock 87.56 12.44 Top-collected liquid / 99.5 Bottom-collected liquid 99.98 /

[0129] 2.6 Extractant Refining Unit

[0130] After the circulating extractant at the bottom of the above-mentioned desorption tower has been circulating for a period of time, it needs to be purified. The bottom liquid is sent to the extractant refining tower through a pipeline branch by a bottom pump for vacuum rectification. The operating pressure is controlled at -0.09 MPa (gauge pressure), the top temperature is controlled at 82.8 - 94.6 °C, and the extractant is distilled out from the top and sent to the extractant feed buffer tank for standby through a pump; the bottom temperature is controlled at 82.8 - 94.6 °C, and the discharged components are mainly heavy components, which are packed in barrels. The specific experimental results are shown in Table 15 below.

[0131] Table 15 Desorption Tower Rectification Data

[0132] Batch DMF (%) Cyclopentane (%) Feedstock 87.56 12.44 Top-collected liquid / 99.5 Bottom-collected liquid 99.98 /

[0133] 2.7 Pilot Test Material Balance

[0134] Table 16 Pilot Project Material Balance Table

[0135]

[0136] Note: The extractant is added once and used cyclically.

[0137] To sum up, due to the relatively large hydrogen-oil ratio in this hydrogenation reaction, it is difficult for a general reactor to solve the mass transfer problem. In the design of this reactor, liquid materials enter from the upper part of the reactor, and hydrogen enters from four sides of the upper head of the reactor. Then, after the hydrogen and liquid materials are fully mixed in the upper part of the reactor to complete mass transfer, they enter the catalyst bed. By using a self-designed hydrogenation reactor, the olefin conversion rate can reach 99.9%. By using atmospheric pressure and extraction multi-column continuous rectification, the separation and purification of products are realized, and cyclopentene and cyclopentane products meeting the standards are obtained.

[0138] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A process for preparing cyclopentane by catalytic hydrogenation of cyclopentene, characterized in that: The steps include: S1, light weight: The crude cyclopentene material is added to the light removal distillation tower for distillation, and the treated crude cyclopentene discharged from the bottom of the tower is used for the next step of cyclopentene refining; S2, Cyclopentene Refining: The crude cyclopentene material after light removal is pumped to the cyclopentene distillation tower for continuous distillation, and the cyclopentene product is obtained by discharging from the top of the tower and stored in barrels; The bottom material is crude cyclopentane material containing a small amount of cyclopentene, which is pumped to the full hydrogenation process for full hydrogenation reaction; S3, full hydrogenation: The crude cyclopentane material is added to the hydrogenation feed tank, and then pumped to the hydrogenation preheater for heating. The heated crude cyclopentane material and hydrogen are simultaneously mixed in the mixer and then enter the hydrogenation reactor for full hydrogenation; S4, Extraction Distillation: The hydrogenation reaction product and the extractant are respectively added to an extractive distillation tower for extractive distillation, and the output component of the tower bottom is an extractant containing cyclopentane, which is sent to a desorption tower for the next step of separation of cyclopentane and the extractant; S5, desorption: The bottom liquid of the extractive distillation tower is fed into a desorption tower to distill out the cyclopentane product, and the output component is a recycled extractant, which is returned to the extractive distillation tower for recycling after heat exchange; S6. Extraction agent refining: The extractant circulating in the bottom of the desorption tower is purified after recycling, and the extractant that needs to be purified is sent to the extractant refining tower for vacuum distillation, and the extractant is evaporated from the top of the tower.

2. The process for preparing cyclopentane by catalytic hydrogenation of cyclopentene according to claim 1, characterized in that: During the light removal in step S1, the bottom temperature of the tower is controlled at 55-70°C, and the top temperature of the tower is controlled at 55-70°C.

3. The process for preparing cyclopentane by catalytic hydrogenation of cyclopentene according to claim 1, characterized in that: During the cyclopentene refining described in step S2, the tower bottom temperature is controlled at 55.6-62.4°C, and the tower top temperature is controlled at 55.6-62.4°C.

4. The process for preparing cyclopentane by catalytic hydrogenation of cyclopentene according to claim 1, characterized in that: The preheater in step S3 is heated to 160-220°C. During full hydrogenation, the hydrogen is inlet and outlet from the top, and the hydrogen is excessive. The bed temperature of the hydrogenation catalyst is controlled to be 190-260°C, and the liquid phase volume space velocity is controlled to be 1.0h -1 , the system pressure is controlled at 2.8MPa, and the hydrogen-to-oil ratio is controlled at 2.0-8.

0.

5. The process for preparing cyclopentane by catalytic hydrogenation of cyclopentene according to claim 1, characterized in that: During the extractive distillation in step S4, the tower top operating temperature is controlled at 49.6-81.6°C, and the tower bottom operating temperature is 49.6-81.6°C.

6. The process for preparing cyclopentane by catalytic hydrogenation of cyclopentene according to claim 1, characterized in that: During the desorption tower distillation described in step S5, the tower top temperature is controlled at 52.3-158.1°C, and the tower bottom temperature is controlled at 52.3-158.1°C.

7. The process for preparing cyclopentane by catalytic hydrogenation of cyclopentene according to claim 1, characterized in that: During the extraction agent purification in step S6, the operating pressure is controlled at -0.09 to -0.06 MPa, the tower top temperature is controlled at 82.8 to 94.6°C, and the tower bottom temperature is controlled at 82.8 to 94.6°C.

8. The process for preparing cyclopentane by catalytic hydrogenation of cyclopentene according to claim 1, characterized in that: The catalyst used in the full hydrogenation in step S3 is a nickel-based catalyst; The preparation of the nickel-based catalyst comprises the following steps: (1) immersing silicon dioxide in a modifier, immersing an ultrasonic probe 3 to 5 cm below the surface of the treating agent, performing ultrasonic treatment, and simultaneously performing electron beam irradiation treatment. After treatment for 1 to 3 hours, the silicon dioxide is filtered and washed with deionized water for 3 to 5 times, and then placed in a vacuum drying oven at 40 to 50° C. for 5 to 8 hours to obtain modified silicon dioxide; (2) Dissolve chitosan in a 1% dilute acetic acid solution, then add allylmethyldimethoxysilane in an amount of 0.3 to 0.6 times the mass of chitosan, stir and mix, and then adjust the pH to 7 at 80 to 90° C. and 300 to 400 rpm for 10 to 12 hours. Then add modified silicon dioxide in an amount of 2 to 3 times the mass of chitosan, stir and mix, and adjust the pH to 12 to 13 with NaON, continue stirring for 1 to 2 hours, and then filter and wash with deionized water for 3 to 5 times, and then place in a vacuum drying oven at 40 to 50° C. and dry for 5 to 8 hours to obtain a catalyst carrier for use; (3) Add NiSO4·6H2O to distilled water to prepare Ni 2+ The concentration is 0.1 mol·L -1 The catalyst carrier is added to the NiSO4·6H2O aqueous solution while stirring, and stirred at 400-600rpm for 5-6h. Then, KBH4 solution is added dropwise at 100-200rpm while stirring under nitrogen protection. After the reaction is completed, the mixture is filtered and washed with water until neutral, and then washed with anhydrous ethanol for 3-5 times and stored in anhydrous ethanol. When used, it is dried to constant weight under nitrogen protection.

9. A process for preparing cyclopentane by catalytic hydrogenation of cyclopentene according to claim 8, characterized in that: The components and corresponding weight percentages of the treating agent in step (1) are: 2-3% of γ-aminopropyltriethoxysilane, 2-3% of tannic acid, 5-6% of sodium dodecylbenzene sulfate, and the balance is anhydrous ethanol. The dose of electron beam irradiation treatment is 7 to 10 kGy.

10. The process for preparing cyclopentane by catalytic hydrogenation of cyclopentene according to claim 8, characterized in that: The concentration of the KBH4 solution in step (4) is 2 to 3 mol·L -1 , the dropping speed is 9~10mL·min -1 .

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