A process for cracking C5 to separate and purify cyclopentene

Abstract

The present invention discloses a process for separating and refining cyclopentene by cracking C5. The cracked C5 undergoes pretreatment and olefin separation, cyclopentadiene selective hydrogenation, cyclopentene distillation and refining, and cyclopentane refining and separation to separate cyclopentene with a purity greater than 99.9% and cyclopentane with a purity greater than 99.9%, thereby maximizing the product value and achieving the maximum economic benefit of the process.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry, and particularly relates to a process for cracking C5 to separate and purify cyclopentene. Background Art

[0002] Cyclopentene is a high-value-added C5 component with a wide range of applications. It is an intermediate for a variety of fine chemical products and can be used to produce high-value-added pharmaceutical intermediates such as cyclopentanol, bromocyclopentane, chlorocyclopentane, and cyclopentanoic acid. Among the various methods for preparing cyclopentene, selective hydrogenation holds the greatest promise for industrialization. The current production capacity of C5 cracking is approximately 2 to 2.5 million tons, and the total capacity is expected to be approximately 2.5 to 3 million tons per year by 2025. C5 components account for approximately 15% of the petroleum cracking process to produce ethylene, and diolefins make up approximately 50% of the C5 mixture. Separation technology for isoprene and piperylene is mature and commercially available. C5 cracking contains over 20% dicyclopentadiene and over 15% cyclopentadiene. Dicyclopentadiene can be thermally cracked to produce cyclopentadiene, which can then be separated and purified after selective hydrogenation to yield cyclopentene. Separating and refining cyclopentene from C5 cracking can increase the economic value of C5 and enhance economic benefits.

[0003] Patent CN103342624A discloses a method for hydrogenating cyclopentadiene to produce high-purity cyclopentene. The palladium in the hydrogenation catalyst Pb / Al2O3 is the active component, and Al2O3 is the carrier. The palladium content accounts for 2.25-30% of the total catalyst mass. Patent CN106673938B discloses a method for hydrogenating cyclopentadiene to produce cyclopentene. A cyclopentadiene feedstock is mixed with a solvent as a hydrogenation reaction feedstock, then mixed with hydrogen and continuously passed through a fixed-bed reactor filled with a selective hydrogenation catalyst. The selective hydrogenation catalyst consists of amorphous nickel phosphide as the active component, an alumina carrier, and a cerium additive. The feedstock for this method is derived from the cracking of dicyclopentadiene and is free of Cl and S, making catalyst processing relatively simple. Patent CN 111875469B discloses a method for ultra-deep removal of carbon disulfide from isoprene products, but the desulfurization operating conditions are relatively harsh. At present, the dicyclopentadiene in the cracked C5 is mainly used to produce dicyclopentadiene resin, and cyclopentene is rarely produced. The added value of the product is low, resulting in waste of resources. At the same time, in the process of cracking C5 to extract diolefins to produce rubber, AlCl3 is used as an initiator, which introduces Cl into the cracked C5 tail oil. If this part of the C5 tail oil is to be used, it must be de-Clified. Summary of the Invention

[0004] The present invention aims to address the above-mentioned deficiencies and provide a process for cracking C5 to separate and purify cyclopentene. This process can adapt to a variety of feedstocks, produces cyclopentene through selective hydrogenation, and separates cyclopentane after full hydrogenation, thereby maximizing product value and achieving maximum economic benefits. To achieve the above-mentioned objectives, the present invention adopts the following technical solutions:

[0005] A process for cracking C5 to separate and purify cyclopentene comprises the following steps:

[0006] (a) Cracking C5 pretreatment and olefin separation: The cracked C5 feedstock is passed through a desulfurization tank 1 to remove CS2 and then enters a desulfurization tower 2. The dechlorinating agent in the bottom of the desulfurization tower 2 converts the small molecular Cl in the cracked C5 into large molecular Cl and is discharged along with the heavy components. At the same time, dicyclopentadiene is depolymerized to produce cyclopentadiene. A C4 light component is produced from the top of the desulfurization tower, and a cracked C5 rich in cyclopentadiene is produced as a side line. The side line component enters a first distillation tower 3 for separation, and isoprene and low-boiling point components are obtained at the top of the tower. The heavy components in the bottom of the tower and the normal pentane separated in the pentane separation tower 8 are mixed and sent to a second distillation tower 4 for cyclopentadiene separation. The top of the tower is light components such as isoprene, and the bottom of the tower is a mixture of cyclopentadiene, cyclopentene and cyclopentane.

[0007] (b) Selective hydrogenation of cyclopentadiene: The cyclopentadiene hydrogenation adopts a low-temperature, low-pressure, high-space-velocity selective hydrogenation process. The cyclopentadiene mixture in the bottom of the second distillation tower 4 in step (a) is mixed with a gas regulator and then enters the cyclopentadiene selective hydrogenation reactor 5 from top to bottom. The selective hydrogenation reaction is carried out on a reduced Ni-S catalyst. Cyclopentadiene is selectively hydrogenated to produce cyclopentene. The hydrogenated components are subjected to gas-liquid separation.

[0008] (c) Cyclopentene distillation and purification: The liquid phase components in the hydrogenated material in step (b) are introduced into a cyclopentene separation tower 6, cyclopentene is separated from the top of the tower, and the remaining C5 mixed components are recombined in the bottom of the tower;

[0009] (d) Refining and separation of cyclopentane: The heavy components in the bottom of the cyclopentene separation tower 6 in step (c) are fed into a full hydrogenation reactor 7 for hydrogenation. The full hydrogenation reaction is carried out over a sulfurized Ni-Mo catalyst to hydrogenate the olefins in the saturated feedstock and remove sulfur and nitrogen impurities. The hydrogenated product is subjected to gas-liquid separation, and the liquid component is fed into a pentane separation tower 8 to separate n-pentane, isopentane, and cyclopentane. The n-pentane is circulated to the second distillation tower 4 for separation of cyclopentadiene.

[0010] The desulfurization agent in the desulfurization tank 1 of step (a) is composed of 3-8% triethanolamine, 33-48% acetone, 8-12% benzyl alcohol, 25-35% saturated Ca(OH)2, 3-8% reduced Cu, and the rest is ethanol.

[0011] The dechlorination agent in the bottom of the dechlorination tower 2 in step (a) is composed of an ethanol solution containing benzyltriethylammonium hydroxide, sodium methoxide and isotridecanol polyoxyethylene polyoxypropylene ether, which converts the small molecular Cl in the cracked C5 into large molecular Cl, and the Cl in C5 is discharged from the bottom of the tower along with the heavy components.

[0012] In the step (b), the catalyst used for the selective hydrogenation of cyclopentadiene is Ni-S catalyst, which is sulfurized at room temperature and then reduced at 400°C, and then cooled to the operating temperature. The reaction conditions are temperature 30-80°C, pressure 1.0-3.0 MPa, and space velocity 0.5-2.0 h -1 , gas-oil volume ratio 400~800:1.

[0013] In the step (b), the gas regulator for the cyclopentadiene selective hydrogenation reaction is a composite gas of H2, N2 and CO.

[0014] The cyclopentene separation tower 6 in step (c) has an operating pressure of 0.11-0.2 MPa, a temperature of 55-70° C., a reflux ratio of 10-28, and produces more than 99.9% cyclopentene at the top of the tower.

[0015] The catalyst used in the full hydrogenation of step (d) is Ni-Mo catalyst, which is used after sulfurization. The reaction conditions are temperature 160-260°C, pressure 2.0-4.0 MPa, and space velocity 0.5-2.0 h -1 , hydrogen-oil volume ratio 400~800:1.

[0016] In the step (d), the bottom temperature of the pentane separation tower 8 is 70-74°C, the top temperature is 62-66°C, the system pressure is 0.04-0.10 MPa, the reflux ratio is 1.4-2.8, the bottom material of the pentane separation tower 8 is pure cyclopentane, the mass content of cyclopentane in the bottom is not less than 99.9%, the top material is isopentane, and the side line produced normal pentane is returned to the second distillation tower 4 for separation of cyclopentadiene and piperylene.

[0017] The process for cracking C5 and separating and refining cyclopentene provided by the present invention has the following advantages:

[0018] In this method, the reduced Cu in the desulfurization tank is dissolved in benzyl alcohol. This, combined with Ca(OH)2 solution and triethanolamine in the presence of acetone, effectively removes CS2 from the C5 component, addressing CS2 poisoning of the Ni catalyst. Furthermore, this method introduces a dechlorinating agent, such as benzyltriethylammonium hydroxide and sodium methoxide, into the desulfurization column kettle. This converts small Cl molecules in the cracked C5 into large Cl molecules through molecular reconstruction. The large Cl molecules are then discharged from the reactor along with the heavy components, protecting the subsequent hydrogenation catalyst and preventing Cl poisoning.

[0019] In this method, n-pentane is recycled and used to separate cyclopentadiene from isopentadiene by utilizing the characteristic that n-pentane and cyclopentadiene form an azeotrope during distillation. This method differs from traditional extractive distillation and can save the process of extractant separation, reduce investment, and make the production process more environmentally friendly. At the same time, n-pentane serves as a diluent for the selective hydrogenation of cyclopentadiene and passes through the selective hydrogenation reactor together with the cyclopentadiene at one time without separation, which can solve the problem of large reaction exotherm and improve the selectivity of the cyclopentadiene hydrogenation reaction.

[0020] The Ni-S catalyst used in this method is a highly dispersed active Ni catalyst prepared through a chelate dispersion process. It is sulfurized with N2 containing CS2 and H2S at room temperature, then reduced at 180°C and 400°C before being cooled to room temperature for use. This catalyst exhibits excellent sulfur tolerance and cyclopentene selectivity. Saturation of the NiO catalyst with CS2 and H2S at room temperature improves the surface acidity and adsorption characteristics of the support, thereby reducing polymer formation and allowing the resulting polymer to escape from the active sites. This also reduces the interaction between olefins and nickel, altering the electronic environment around the nickel active sites and, consequently, the adsorption capacity of the active sites for adsorbed species. This not only improves the catalyst's selectivity but also enhances its resistance to carbon deposition.

[0021] The method adopts a gas regulator, and N2 and CO are mixed with H2 to prepare the gas regulator, which can effectively increase the selectivity of the reaction and improve the conversion rate and selectivity of cyclopentene.

[0022] This method differs from the traditional method of cracking C5 to separate cyclopentadiene and polymerizing it to prepare dicyclopentadiene resin. Instead, it depolymerizes the dicyclopentadiene in the cracked C5 to prepare cyclopentadiene, and then selectively hydrogenates the cyclopentadiene to make cyclopentene. The purity of the product cyclopentene is greater than 99.9%, which increases the added value of the product, improves product profits, and reduces pollution emissions.

[0023] The cracking C5 of this method removes alkynes and C4 components through a de-weighting tower, which solves the problem of excessive heat release during hydrogenation of alkynes and C4 under low temperature conditions, increases the hydrogenation selectivity of cyclopentadiene, and reduces catalyst coking. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention provides a schematic diagram of a process flow for cracking C5 to separate and purify cyclopentene.

[0025] Figure 1 The definitions of the tags are:

[0026] 1 is a desulfurization tank; 2 is a deweighting tower; 3 is a first distillation tower; 4 is a second distillation tower; 5 is a selective hydrogenation reactor; 6 is a cyclopentene separation tower; 7 is a full hydrogenation reactor; and 8 is a cyclopentane separation tower. DETAILED DESCRIPTION

[0027] The technical solution provided by the present invention is described in detail below with reference to the accompanying drawings and specific examples:

[0028] The raw materials are processed according to the process shown in the attached figure to separate cyclopentene, refined cyclopentane and other products. Raw material one comes from the cracked C5 of Zhongyuan Ethylene Plant, and raw material two comes from the C5 tail oil after the cracked C5 of Tianli Industrial to extract resin. Their properties are shown in Table 1:

[0029] Table 1. Raw material properties

[0030] Example 1

[0031] The raw materials are passed through a desulfurization tank, the composition of which is 5wt% triethanolamine, 36wt% acetone, 10wt% benzyl alcohol, 30wt% saturated Ca(OH)2, 5.5wt% reduced Cu and 13.5wt% ethanol. After removing CS2, the raw materials enter a desulfurization tower. A liquid phase dechlorination agent containing an ethanol solution of benzyltriethylammonium hydroxide, sodium methoxide and isotridecanol polyoxyethylene polyoxypropylene ether is introduced into the desulfurization tower kettle to convert the small molecular Cl in the cracked C5 into large molecular Cl and discharge it with the heavy component. At the same time, dicyclopentadiene is depolymerized to generate cyclopentadiene. A carbon four light component is extracted from the top of the desulfurization tower, and a cracked C5 rich in cyclopentadiene is extracted from the side line. The side line component enters the first distillation tower for separation, and isoprene is obtained from the top of the tower. The cyclopentadiene and low-boiling point components, the heavy components in the bottom of the tower and the normal pentane separated in the pentane separation tower are mixed and sent to the second distillation tower for cyclopentadiene separation. The top of the tower is light components such as isopentadiene, and the bottom of the tower is a mixture of cyclopentadiene, cyclopentene and cyclopentane. The cyclopentadiene mixture in the bottom of the second distillation tower is mixed with a gas regulator and then enters the cyclopentadiene selective hydrogenation reactor from top to bottom. The reactor is filled with a reduced Ni-S catalyst. The catalyst is sulfurized by passing N2 containing 2g / L CS2 and 8g / L H2S at room temperature until the catalyst no longer consumes S and stops sulfurization. Then H2 is passed at 400℃ for reduction and then cooled to the use temperature. The reaction conditions are temperature 30℃, pressure 3.0MPa, and space velocity 0.5h -1 , gas-oil volume ratio 400:1, gas regulator H2:N2:CO=7:2:1, cyclopentadiene is selectively hydrogenated to produce cyclopentene, the hydrogenated components are subjected to gas-liquid separation, the liquid components enter the cyclopentene separation tower, the operating pressure is 0.11MPa, the temperature is 70℃, the reflux ratio is 28, more than 99.9% of cyclopentene is separated from the top of the tower, and the tower bottom is recombined into the remaining C5 mixed components; the recombinant components in the cyclopentene separation tower bottom enter the full hydrogenation reactor for hydrogenation, the full hydrogenation reaction is a sulfided Ni-Mo catalyst, the reaction conditions are temperature 220℃, pressure 3.0MPa, space velocity 1.0h -1The volume ratio of hydrogen to oil is 600:1. The olefins in the saturated raw materials are hydrogenated to remove sulfur and nitrogen impurities. The products after hydrogenation are separated by gas-liquid separation. The liquid components enter the pentane separation tower. The bottom temperature is 70°C, the top temperature is 62°C, the system pressure is 0.10MPa, and the reflux ratio is 1.4. The bottom material of the pentane separation tower is pure cyclopentane, and the mass content of cyclopentane in the bottom is not less than 99.9%. The top material is isopentane. Normal pentane, isopentane, and cyclopentane are separated, and normal pentane is recycled to the second distillation tower for the separation of cyclopentadiene. Example 2

[0032] The raw material one and the raw material two are mixed in a mass fraction of 1:1 and then passed through a desulfurization tank. The desulfurization tank composition is 3wt% triethanolamine, 48wt% acetone, 8wt% benzyl alcohol, 35wt% saturated Ca(OH)2, 3wt% reduced Cu and 3wt% ethanol. After removing CS2, it enters a desulfurization tower. A liquid phase dechlorination agent containing an ethanol solution of benzyltriethylammonium hydroxide, sodium methoxide and isotridecanol polyoxyethylene polyoxypropylene ether is introduced into the desulfurization tower kettle to convert the small molecule Cl in the cracked C5 into a large molecule Cl and discharge it with the heavy component. At the same time, dicyclopentadiene is depolymerized to generate cyclopentadiene. The carbon four light component is extracted from the top of the desulfurization tower, and the cracked C5 rich in cyclopentadiene is extracted from the side line. The side line component enters the first distillation tower for separation, and the top of the tower is obtained. The isoprene and low-boiling point components are separated, and the heavy components in the bottom of the tower and the normal pentane separated in the pentane separation tower are mixed and sent to the second distillation tower for cyclopentadiene separation. The top of the tower is light components such as isopentadiene, and the bottom of the tower is a mixture of cyclopentadiene, cyclopentene and cyclopentane; the cyclopentadiene mixture in the bottom of the second distillation tower is mixed with a gas regulator and then enters the cyclopentadiene selective hydrogenation reactor from top to bottom. The reactor is filled with a reduced Ni-S catalyst. The catalyst is sulfurized by passing N2 containing 2g / L CS2 and 8g / L H2S at room temperature until the catalyst no longer consumes S and stops sulfurization. Then H2 is passed at 400℃ for reduction, and then the temperature is lowered to the use temperature. The reaction conditions are temperature 80℃, pressure 1.0MPa, and space velocity 2.0h -1 , gas-oil volume ratio 800:1, gas regulator H2:N2:CO=5:3:2, cyclopentadiene is selectively hydrogenated to produce cyclopentene, the hydrogenated components are subjected to gas-liquid separation, the liquid component enters the cyclopentene separation tower, the operating pressure is 0.2MPa, the temperature is 55℃, the reflux ratio is 10, more than 99.9% of cyclopentene is separated from the top of the tower, and the tower bottom is recombined into the remaining C5 mixed components; the recombinant components in the cyclopentene separation tower bottom enter the full hydrogenation reactor for hydrogenation, the full hydrogenation reaction is a sulfurized Ni-Mo catalyst, the reaction conditions are temperature 260℃, pressure 2.0MPa, space velocity 2.0h -1The volume ratio of hydrogen to oil is 800:1. The olefins in the saturated raw materials are hydrogenated to remove sulfur and nitrogen impurities. The products after hydrogenation are separated by gas-liquid separation. The liquid components enter the pentane separation tower. The bottom temperature is 72°C, the top temperature is 64°C, the system pressure is 0.07MPa, and the reflux ratio is 2.1. The bottom material of the pentane separation tower is pure cyclopentane, and the mass content of cyclopentane in the bottom is not less than 99.9%. The top material is isopentane. Normal pentane, isopentane, and cyclopentane are separated, and normal pentane is recycled to the second distillation tower for the separation of cyclopentadiene. Example 3

[0033] The raw material is passed through a desulfurization tank, the composition of which is 8wt% triethanolamine, 33wt% acetone, 12wt% benzyl alcohol, 25wt% saturated Ca(OH)2, 8wt% reduced Cu and 14wt% ethanol. After removing CS2, it enters a desulfurization tower. A liquid phase dechlorination agent containing an ethanol solution of benzyltriethylammonium hydroxide, sodium methoxide and isotridecanol polyoxyethylene polyoxypropylene ether is introduced into the desulfurization tower kettle to convert the small molecular Cl in the cracked C5 into large molecular Cl and discharge it with the heavy component. At the same time, dicyclopentadiene is depolymerized to generate cyclopentadiene. The carbon four light component is extracted from the top of the desulfurization tower, and the cracked C5 rich in cyclopentadiene is extracted from the side line. The side line component enters the first distillation tower for separation, and isoprene and The low-boiling point components, the heavy components in the bottom of the tower and the normal pentane separated from the pentane separation tower are mixed and sent to the second distillation tower for cyclopentadiene separation. The top of the tower is light components such as isopentadiene, and the bottom of the tower is a mixture of cyclopentadiene, cyclopentene and cyclopentane. The cyclopentadiene mixture in the bottom of the second distillation tower is mixed with a gas regulator and then enters the cyclopentadiene selective hydrogenation reactor from top to bottom. The reactor is filled with a reduced Ni-S catalyst. The catalyst is sulfurized by passing N2 containing 2g / L CS2 and 8g / L H2S at room temperature until the catalyst no longer consumes S and stops sulfurization. Then H2 is passed at 400℃ for reduction and then the temperature is lowered to the use temperature. The reaction conditions are temperature 40℃, pressure 2.0MPa, and space velocity 1.0h -1 , gas-oil volume ratio 600:1, gas regulator H2:N2:CO=3:3:4, cyclopentadiene is selectively hydrogenated to produce cyclopentene, the hydrogenated components are subjected to gas-liquid separation, the liquid components enter the cyclopentene separation tower, the operating pressure is 0.15MPa, the temperature is 63℃, the reflux ratio is 18, more than 99.9% of cyclopentene is separated from the top of the tower, and the tower bottom is recombined into the remaining C5 mixed components; the recombinant components in the cyclopentene separation tower bottom enter the full hydrogenation reactor for hydrogenation, the full hydrogenation reaction is a sulfurized Ni-Mo catalyst, the reaction conditions are temperature 160℃, pressure 4.0MPa, space velocity 0.5h -1The volume ratio of hydrogen to oil is 400:1. The olefins in the saturated raw materials are hydrogenated to remove sulfur and nitrogen impurities. The products after hydrogenation are separated by gas-liquid separation. The liquid components enter the pentane separation tower. The bottom temperature is 74°C, the top temperature is 66°C, the system pressure is 0.04MPa, and the reflux ratio is 2.8. The bottom material of the pentane separation tower is pure cyclopentane, and the mass content of cyclopentane in the bottom is not less than 99.9%. The top material is isopentane. Normal pentane, isopentane and cyclopentane are separated, and normal pentane is recycled to the second distillation tower for the separation of cyclopentadiene.

[0034] Table 2. Product properties before and after desulfurization and dechlorination pretreatment

[0035]

[0036] As can be seen from Table 1, after the cracked C5 feedstock is pretreated, CS2 and total Cl in the product can be effectively removed. When the cyclopentadiene selective hydrogenation catalyst processes the pretreated feedstock, S and Cl are not absorbed and enriched on the selective hydrogenation catalyst. This shows that the pretreatment process can effectively remove CS2 and Cl in the cracked C5, can adapt to different feedstocks, and protect the cyclopentadiene selective hydrogenation catalyst.

[0037] Table 3. Properties of products after hydrogenation

[0038]

[0039] Table 4. Properties of products after separation and purification

[0040]

[0041] As can be seen from Tables 3 and 4, after the cracking of C5 undergoes raw material pretreatment, C5 olefin separation, cyclopentadiene selective hydrogenation refining, cyclopentene distillation refining, and cyclopentane refining and separation, the purity of the generated cyclopentene is greater than 99.9%, the purity of cyclopentane is greater than 99.9%, dicyclopentadiene and cyclopentadiene are converted into cyclopentene and cyclopentane, and the products can meet the quality requirements of national standards. After the cracking of C5 is treated by this process, the products have high added value and the process benefits are maximized.

Claims

1. A process for cracking C5 to separate and purify cyclopentene, characterized by: The raw materials come from ethylene cracking C5. The raw materials undergo pretreatment and olefin separation, cyclopentadiene selective hydrogenation, cyclopentene distillation and refining, cyclopentane refining and separation to produce cyclopentene and cyclopentane. The specific process includes the following steps: (a) Cracking C5 pretreatment and olefin separation: The cracking C5 raw material is passed through the desulfurization tank (1) to remove CS2 and then enters the desulfurization tower (2). The dechlorinating agent in the bottom of the desulfurization tower (2) converts the small molecular Cl in the cracking C5 into large molecular Cl and discharges it with the heavy components. At the same time, dicyclopentadiene is depolymerized to generate cyclopentadiene. The C4 light component is extracted from the top of the desulfurization tower, and the cracking C5 rich in cyclopentadiene is extracted from the side line. The side line component enters the first distillation tower (3) for separation. Isoprene and low boiling point components are obtained at the top of the tower. The heavy components in the bottom of the tower and the normal pentane separated by the pentane separation tower (8) are mixed and sent to the second distillation tower (4) for cyclopentadiene separation. The top of the tower is the light components such as isopentadiene, and the bottom of the tower is the mixture of cyclopentadiene, cyclopentene and cyclopentane. (b) Selective hydrogenation of cyclopentadiene: The cyclopentadiene hydrogenation adopts a low-temperature, low-pressure, high-space-velocity selective hydrogenation process. The cyclopentadiene mixture in the bottom of the second distillation tower (4) in step (a) is mixed with a gas regulator and then enters the cyclopentadiene selective hydrogenation reactor (5) from top to bottom. The selective hydrogenation reaction is carried out on a reduced Ni-S catalyst. Cyclopentadiene is selectively hydrogenated to produce cyclopentene, and the hydrogenated components are subjected to gas-liquid separation. (c) Distillation and purification of cyclopentene: the liquid phase components in the hydrogenated material in step (b) are introduced into a cyclopentene separation tower (6), cyclopentene is separated from the top of the tower, and the bottom of the tower is recombined to form the remaining C5 mixed components; (d) Purification and separation of cyclopentane: The heavy components in the bottom of the cyclopentene separation tower (6) in step (c) enter the full hydrogenation reactor (7) for hydrogenation. The full hydrogenation reaction is carried out using a sulfurized Ni-Mo catalyst to hydrogenate the olefins in the saturated feedstock and remove the sulfur and nitrogen impurities therein. The hydrogenated product is subjected to gas-liquid separation, and the liquid phase component enters the pentane separation tower (8) to separate n-pentane, isopentane, and cyclopentane. The n-pentane is circulated to the second distillation tower (4) for separation of cyclopentadiene.

2. A process for cracking C5 to separate and purify cyclopentene according to claim 1, characterized in that: The desulfurization agent in the desulfurization tank (1) of step (a) is composed of 3-8% triethanolamine, 33-48% acetone, 8-12% benzyl alcohol, 25-35% saturated Ca(OH)2, 3-8% reduced Cu, and the rest is ethanol.

3. The process for separating and refining cyclopentene by cracking C5 according to claim 1, characterized in that: In the step (a), the dechlorinating agent in the bottom of the deweighting tower (2) is composed of an ethanol solution containing benzyltriethylammonium hydroxide, sodium methoxide and isotridecanol polyoxyethylene polyoxypropylene ether, which converts the small molecular Cl in the cracked C5 into large molecular Cl, and the Cl in the C5 is discharged from the bottom of the tower along with the heavy components.

4. The process for separating and refining cyclopentene by cracking C5 according to claim 1, wherein: In the step (b), the catalyst used for the selective hydrogenation of cyclopentadiene is Ni-S catalyst, which is sulfurized at room temperature and then reduced at 400°C, and then cooled to the operating temperature. The reaction conditions are temperature 30-80°C, pressure 1.0-3.0 MPa, and space velocity 0.5-2.0 h -1 , gas-oil volume ratio 400~800:

1.

5. The process for separating and refining cyclopentene by cracking C5 according to claim 1, characterized in that: In the step (b), the reaction gas regulator is a composite gas prepared by mixing H2, N2 and CO.

6. The process for cracking C5 to separate and purify cyclopentene according to claim 1, characterized in that: In the step (c), the cyclopentene separation tower (6) has an operating pressure of 0.11-0.2 MPa, a temperature of 55-70° C., a reflux ratio of 10-28, and obtains more than 99.9% of cyclopentene at the top of the tower.

7. The process for cracking C5 to separate and purify cyclopentene according to claim 1, characterized in that: The catalyst used in the full hydrogenation of step (d) is Ni-Mo catalyst, which is used after sulfurization. The reaction conditions are temperature 160-260°C, pressure 2.0-4.0 MPa, and space velocity 0.5-2.0 h -1 , hydrogen-oil volume ratio 400~800:

1.

8. The process for cracking C5 to separate and purify cyclopentene according to claim 1, characterized in that: The bottom temperature of the pentane separation tower (8) in step (d) is 70-74°C, the top temperature is 62-66°C, the system pressure is 0.04-0.10 MPa, the reflux ratio is 1.4-2.8, the bottom material of the pentane separation tower (8) is pure cyclopentane, the mass content of cyclopentane in the bottom is not less than 99.9%, the top material is isopentane, and the side-line produced normal pentane is returned to the second distillation tower (4) for separation of cyclopentadiene and isopentadiene.

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