Production method of C5 monoolefine

Abstract

The invention provides a production method of C5 monoolefine, and belongs to the technical field of olefin production. According to the invention, rectification pretreatment is carried out on an m-pentadiene raw material, then two-stage hydrogenation control is adopted, and the per-pass conversion rate of the m-pentadiene is strictly controlled in the first-stage hydrogenation process, so that the yield of the 1-pentene is remarkably improved, and the purity reaches 99.9% or above; carrying out second-stage hydrogenation on the C5 fraction which is subjected to the first-stage hydrogenation and from which 1-pentene is separated, so that unconverted m-pentadiene in the raw material is converted into monoolefine, and controlling the conversion rate gt of the second-stage hydrogenation; and rectifying to obtain a 2-pentene product and a cyclopentene product.

Description

Technical Field

[0001] This invention relates to the field of olefin production technology, and specifically to a method for producing C5 monoolefins. Background Technology

[0002] A C5 monoolefin is an unsaturated hydrocarbon containing five carbon atoms (C5) and only one carbon-carbon double bond (C=C), with the molecular formula C5H. 10 Based on the number of carbon atoms in the main chain, C5 monoolefins can be classified into straight-chain C5 monoolefins, C5 monoolefins with one methyl branch, and C5 monoolefins with two methyl branches. Straight-chain C5 monoolefins include 1-pentene and 2-pentene. 1-Pentene is a fine chemical product; it is a key intermediate in the production of 1,2-pentanediol via epoxidation, which in turn produces the insecticide propiconazole. Propiconazole is a promising alternative to organophosphorus pesticides with minimal environmental impact. Meanwhile, 1,2-pentanediol is a multifunctional and widely used cosmetic ingredient, possessing the moisturizing properties, antibacterial, and solubilizing effects of diols. 2-Pentene is an important organic chemical raw material, used in the production of the coating solvent sec-amyl acetate, and can also be used to produce 2-pentanol and 3-pentanol via hydration, further producing 2-pentanone and 3-pentanone products.

[0003] The process of producing ethylene from naphtha steam cracking typically produces a considerable amount of C5 fraction (hereinafter referred to as C5 fraction), accounting for approximately 10% of ethylene production. Currently, the comprehensive utilization of C5 fraction mainly involves separating it to obtain higher-value dienes such as isoprene, isoprene, and dicyclopentadiene, as well as isopentene products. The remaining C5 material after separating the target products is called raffinate C5, accounting for approximately 10-15% of the C5 fraction feedstock. Raffinate C5 contains approximately 6-10% 1-pentene, 20% 2-pentene, and approximately 15% cyclopentene. Because the boiling points and volatility of the components in raffinate C5 are very similar, the 1-pentene, 2-pentene, and cyclopentene obtained through precision distillation have low purity, making it impossible to obtain 1-pentene, 2-pentene, and cyclopentene products with a purity of over 99.8%.

[0004] Invention patents CN101289363B and CN101289360B employ a combination of precision distillation and extractive distillation to obtain 1-pentene with a purity of 96.5-97.5% and 2-pentene with a purity of 98.5-99.5%, respectively. However, due to the very close boiling points of the components in the C5 fraction, a higher theoretical plate number, a higher reflux ratio, and a larger amount of extractant are required, resulting in higher energy consumption.

[0005] Invention patents CN106478354B, CN106478355B, CN106478353B, and CN106478356B disclose a method for separating 1-pentene from C5 by-product fractions. Using the by-product fraction from which dienes and isopentenenes have been removed during C5 separation as raw material, a combination of azeotropic distillation, simple distillation, and isomerization processes is employed to obtain 1-pentene and 2-pentene products. However, due to limitations in the availability of C5 fraction sources, this process can only serve as a complementary process to C5 separation and isopentenene production, and cannot be scaled up for large-scale production of 1-pentene. Furthermore, because the isomerization reaction of 2-methyl-1-butene, the main impurity in the C5 fraction, is limited by thermodynamic equilibrium conversion rates, 100% conversion cannot be achieved. Therefore, the purity of 1-pentene produced using this process is typically below 99.6%, failing to meet the requirement of 99.8% purity or higher for 1,2-pentanediol and polymer monomers.

[0006] Invention patents CN103333042B and CN103333041B employ a selective hydrogenation method for isoprene to obtain a mixture of 1-pentene and 2-pentene, which are then separated to obtain a high-purity 1-pentene product. However, due to the poor selectivity of isoprene hydrogenation to 1-pentene, the hydrogenation product contains only 14.83% 1-pentene, and the purity of 1-pentene is 99.59%, which still does not meet the requirement of 99.8% purity for 1,2-pentanediol and polymer monomers. Summary of the Invention

[0007] To address the technical problem that the purity of 1-pentene produced from C5 fractions cannot meet requirements, this invention provides a method for producing C5 monoolefins. The method employs a two-stage hydrogenation control process, and strictly controls the single-pass conversion rate of isoprene during the first hydrogenation stage. This significantly improves the yield of 1-pentene while achieving a purity of over 99.9%.

[0008] A method for producing C5 monoolefins includes the following steps:

[0009] 1. The isoprene feedstock is distilled, and the bottom of the column yields a C5 fraction rich in isoprene, while the top of the column yields a light fraction containing isoprene, 2-methyl-1-butene, n-pentane, 2-methyl-2-butene and a small amount of trans-isoprene.

[0010] The main impurities in the isoprene feedstock are isoprene (boiling point 34.07℃), 2-methyl-1-butene (boiling point 31.16℃), n-pentane (boiling point 36.07℃), 2-methyl-2-butene (boiling point 38.57℃), and trace amounts of trans-2-pentene (boiling point 36.35℃) and cis-2-pentene (boiling point 36.94℃). To produce high-purity 1-pentene (boiling point 29.97℃), the isoprene feedstock needs to be distilled to separate isoprene, 2-methyl-1-butene, n-pentane, and most of the 2-methyl-2-butene from the top of the distillation column. Otherwise, because their boiling points are very close to those of 1-pentene, high-purity 1-pentene cannot be obtained through distillation. Step 1 is the pretreatment of the isoprene raw material, which separates isoprene, 2-methyl-1-butene, n-pentane, most of the 2-methyl-2-butene and a small amount of trans-isoprene, and also reduces the energy consumption of the subsequent product refining.

[0011] During the pretreatment process, the C5 fraction separated from the top of the column contains a certain amount of isoprene and isopentenene, which can be used as a raw material for the production of C5 petroleum resin. The bottom material of the column after selective hydrogenation (subsequent steps) contains 1-pentene, 2-pentene, cyclopentene (38.57℃), cyclopentane (49.25℃) and n-pentane, which are high-quality raw materials for the production of 1-pentene, 2-pentene and cyclopentene products.

[0012] 2. The C5 fraction rich in isoprene is fed together with hydrogen into an adiabatic bubbling bed hydrogenation reactor. The catalyst is Pd / Al2O3. A first-stage hydrogenation reaction is carried out, with the conversion rate controlled at 95-98%, yielding a first-stage hydrogenation reaction liquid. Here, the main purpose of controlling the conversion rate is to improve the selectivity of 1-pentene.

[0013] 3. The hydrogenated reaction solution was distilled, and 1-pentene was obtained at the top of the column.

[0014] The first-stage hydrogenation process employs an adiabatic bubbling bed hydrogenation reactor, enabling the hydrogenation feedstock to be converted to 1-pentene with high selectivity on the catalyst surface in a plug flow. Under suitable process conditions and with strict control of the single-pass conversion rate of isoprene below 98%, the yield of 1-pentene is significantly improved, the 1-pentene content in the first-stage hydrogenation reaction solution is 28-30%, and the purity of the 1-pentene product obtained by distillation is above 99.9%.

[0015] 4. The bottom liquid from step 3 and hydrogen gas are fed together into an adiabatic bubbling bed hydrogenation reactor. The catalyst is Pd / Al2O3. A two-stage hydrogenation reaction is carried out. The conversion rate of the two-stage hydrogenation is controlled to be >99.99% to obtain the two-stage hydrogenation reaction liquid.

[0016] 5. The second-stage hydrogenation reaction solution was distilled to obtain 2-pentene at the top of the column;

[0017] 6. The liquid in the bottom of the column from step 5 is distilled to obtain cyclopentene product at the top of the column and a heavy component rich in cyclopentane at the bottom of the column.

[0018] The second-stage hydrogenation also uses an adiabatic bubbling bed hydrogenation reactor. The C5 fraction that has undergone the first-stage hydrogenation and separated 1-pentene is subjected to second-stage hydrogenation to convert the unconverted isoprene in the feedstock into monoolefins. The conversion rate of the second-stage hydrogenation is controlled to be >99.99%. The 2-pentene and cyclopentene products are obtained by distillation.

[0019] The hydrogenation process exhibits distinct parallel and tandem reaction characteristics. Parallel hydrogenation of isoprene yields 1-pentene and 2-pentene. Since 1-pentene exhibits higher hydrogenation activity compared to 2-pentene, its tandem side reaction involves the re-hydrogenation of 1-pentene to produce the byproduct n-pentane. Furthermore, 1-pentene undergoes hydroisomerization to 2-pentene at a faster rate than the re-hydrogenation. Therefore, to improve the yield of 1-pentene, the hydrogen-to-oil molar ratio must be strictly controlled, and the catalyst bed temperature must be effectively controlled through the recycling of hydrogenation products to ensure the inherent safety of the hydrogenation process. Under suitable process conditions and with the single-pass conversion of isoprene strictly controlled below 98%, the yield of 1-pentene is significantly improved, with the 1-pentene content in the hydrogenation solution ranging from 28% to 30%.

[0020] The C5 fraction, after a first-stage hydrogenation process that separates 1-pentene, undergoes a second-stage hydrogenation to convert unconverted isoprene into mono-olefins. Unlike the first-stage hydrogenation, the second-stage hydrogenation aims to minimize n-pentane formation while achieving an isoprene conversion rate of over 99.99%, thus facilitating the production of 2-pentene with a purity of approximately 98.5% and cyclopentene with a purity of over 99.9%.

[0021] Preferably, in step 1, the theoretical number of distillation plates is 130-180, the operating pressure is 1.1-3.0 bar, the bottom temperature is 50-70°C, the top temperature is 40-50°C, and the reflux ratio is 8-30.

[0022] Preferably, in step 2, the molar feed ratio of hydrogen to diene in the material is 1.0–1.3:1, and the mass hourly space velocity (HHSV) is 2–8 hr. -1 The reaction pressure is 3–8 bar, the reaction temperature is 30–90 °C, and the mass ratio of hydrogenated liquid circulation to fresh feed is 8–15:1.

[0023] Preferably, in step 3, the theoretical number of distillation plates is 120-150, the operating pressure is 1.0-3.0 bar, the bottom temperature is 55-80°C, the top temperature is 40-60°C, and the reflux ratio is 10-30.

[0024] Preferably, in step 4, the molar feed ratio of hydrogen to diene in the material is 1.0–1.3:1, and the mass hourly space velocity (HHSV) is 2–8 hr. -1 The reaction pressure is 3–8 bar, the reaction temperature is 30–90 °C, and the mass ratio of hydrogenated liquid circulation to fresh feed is 8–15:1.

[0025] Preferably, in step 5, the theoretical number of distillation plates is 120-150, the operating pressure is 1.0-3.0 bar, the bottom temperature is 56-85°C, the top temperature is 42-62°C, and the reflux ratio is 10-30.

[0026] Preferably, the theoretical number of plates for the total distillation in step 6 is 120 to 150, the operating pressure is 0.0 to 1.5 bar, the bottom temperature is 60 to 70°C, the top temperature is 44 to 65°C, and the reflux ratio is 5 to 15.

[0027] The method for producing C5 monoolefins provided by this invention significantly improves hydrogenation selectivity and the purity of 1-pentene products, with 1-pentene product purity reaching over 99.9%, 2-pentene product purity reaching 98.5%, meeting downstream purity requirements, and cyclopentene product purity reaching 99.9%. At the same time, the catalyst bed temperature is easy to control, improving the inherent safety of the hydrogenation reaction, and effectively reducing purification energy consumption and production costs. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to specific embodiments. The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described to better illustrate the principles and practical applications of the invention, and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

[0029] In this invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art.

[0030] Examples 1-10

[0031] The isoprene feedstock is fed into a distillation column for distillation. The theoretical number of trays in the distillation column is 130–180. The operating pressure is 1.1–3.0 bar, the bottom temperature is 50–70°C, the top temperature is 40–50°C, and the reflux ratio is 8–30.

[0032] The top fraction of the column contains light components including isoprene, 2-methyl-1-butene, n-pentane, 2-methyl-2-butene, and a small amount of trans-isoprene, while the bottom fraction is a C5 fraction rich in isoprene. Table 1-1 shows the operating conditions, and Table 1-2 shows the composition of the isoprene feedstock, the top fraction, and the bottom fraction.

[0033] Table 1-1 Operating conditions for Examples 1-10

[0034] Operating pressure (bar) Tower bottom temperature (°C) Tower top temperature (°C) reflux ratio Example 1 1.1 50 40 8﹕1 Example 2 3.0 70 50 30﹕1 Example 3 1.5 55 43 10﹕1 Example 4 2.3 58 45 25﹕1 Example 5 1.8 56 43 15﹕1 Example 6 2.5 65 44 20﹕1 Example 7 1.6 56 45 23﹕1 Example 8 2.4 63 46 18﹕1 Example 9 2.0 60 44 22﹕1 Example 10 2.2 61 45 21﹕1

[0035] Table 1-2 GC analysis results of typical isopentadiene feedstock, top and bottom fractions from Examples 1-10

[0036] Components Raw materials / wt% C5 fraction was collected from the top of the column (wt%) C5 fraction extracted from the bottom of the column / wt% 2-Methyl-1-butene 0.12 12.37 0.00 n-Pentane 0.15 15.46 0.00 Isoprene 0.15 15.46 0.00 trans-pentene-2 0.08 8.25 0.00 cispentene-2 0.05 5.15 0.00 2-Methyl-2-butene 0.60 43.30 0.18 trans-m-pentadiene 47.68 0.00 48.15 cyclopentadiene 0.28 0.00 0.28 cis-m-pentadiene 25.76 0.00 26.01 cyclopentene 17.53 0.00 17.70 cyclopentane 4.74 0.00 4.74 2,2-Dimethylbutane 0.36 0.00 0.36 Other C5 2.40 0.00 2.40

[0037] Examples 11-20

[0038] The hydrogenation reaction was carried out in an adiabatic bubbling bed tubular reactor with dimensions of φ25mm × 1500mm. The reactor was loaded with 100mL of catalyst, with Pd as the active component and Al2O3 as the support, and the Pd content was 0.30wt%. Inert ceramic balls were packed at the bottom of the reactor. Fresh catalyst was activated with hydrogen before feeding. Platinum resistance thermometers were installed at the top, middle, and bottom of the catalyst bed. The feed rate was controlled by a feed pump, and the system pressure was regulated by a back pressure valve.

[0039] Pretreated isoprene feedstock, mixed with hydrogen, enters the catalyst bed from the bottom of the reactor for hydrogenation under set reaction conditions. The hydrogenated material enters a gas-liquid separator from the top of the hydrogenation reactor; the liquid phase enters a product storage tank; unreacted hydrogen is depressurized by a regulating valve, metered by a wet gas meter, and then vented, or compressed and returned to the reaction system. The hydrogenation products obtained in the examples were analyzed by chromatography, and the conversion rate and product selectivity were calculated. The reaction conditions for each example are shown in Table 2-1, and the results are shown in Table 2-2.

[0040] Table 2-1 Operating conditions for Examples 11-20

[0041] <![CDATA[Mass space velocity (hr -1 )]]> Reaction temperature (°C) Pressure (bar) H2 / diene molar ratio Example 11 2.0 30 3.0 1.00:1 Example 12 8.0 90 8.0 1.30:1 Example 13 6.0 35 4.0 1.10:1 Example 14 4.5 40 5.6 1.25:1 Example 15 4.0 55 6.0 1.15:1 Example 16 5.5 70 5.5 1.20:1 Example 17 4.2 45 5.5 1.12:1 Example 18 5.0 38 5.0 1.14:1 Example 19 5.5 60 5.5 1.00:1 Example 20 5.6 46 6.0 1.20:1

[0042] Table 2-2 GC analysis results of typical first-stage hydrogenation feedstocks and hydrogenation reaction solutions in Examples 11-20

[0043] Components Raw materials / wt% Hydrogenation liquid / wt% 1-Pentene 0.00 29.15 2-Methyl-1-butene 0.00 0.00 n-Pentane 0.00 0.44 Isoprene 0.00 0.00 trans-pentene-2 0.00 29.59 cispentene-2 0.00 14.80 2-Methyl-2-butene 0.18 0.18 trans-m-pentadiene 48.15 0.47 cyclopentadiene 0.28 0.00 cis-m-pentadiene 26.01 0.25 cyclopentene 17.70 17.52 cyclopentane 4.74 4.89 2,2-Dimethylbutane 0.36 0.34 Other C5 2.40 2.36

[0044] Examples 21-30

[0045] The hydrogenation reaction solution is fed into a distillation column for rectification. Utilizing the boiling point differences among the components in the hydrogenation feed, 1-pentene is separated in a distillation column with 120–150 theoretical plates. The reboiler temperature is 55–80°C, the top temperature is 40–60°C, the reflux ratio is 10–30, and the operating pressure is 1.0–3.0 bar. Table 3-1 shows the operating conditions, and Table 3-2 shows the composition of the hydrogenation feed, the top of the column, and the reboiler.

[0046] Table 3-1 Operating conditions for Examples 21-30

[0047] Operating pressure (bar) Tower bottom temperature (°C) Tower top temperature (°C) reflux ratio Example 21 1.0 55 40 10﹕1 Example 22 3.0 80 60 30﹕1 Example 23 1.5 60 43 15﹕1 Example 24 2.3 68 45 25﹕1 Example 25 1.8 66 43 15﹕1 Example 26 2.5 65 55 20﹕1 Example 27 1.6 64 50 23﹕1 Example 28 2.4 63 46 18﹕1 Example 29 2.0 60 44 22﹕1 Example 30 2.2 61 45 21﹕1

[0048] Table 3-2 GC analysis results of typical first-stage hydrogenation reaction liquid, top of column, and bottom of column in Examples 21-30

[0049] Components Raw materials / wt% Top of the tower 1-pentene product / wt% C5 fraction in the bottom of the column / wt% 1-Pentene 29.15 99.93 0.03 n-Pentane 0.44 0.03 0.61 Isoprene 0.00 0.00 0.00 trans-pentene-2 29.59 0.02 41.76 cispentene-2 14.80 0.02 20.88 2-Methyl-2-butene 0.18 0.00 0.25 trans-m-pentadiene 0.47 0.00 0.67 cyclopentadiene 0.00 0.00 0.00 cis-m-pentadiene 0.25 0.00 0.36 cyclopentene 17.52 0.00 24.73 cyclopentane 4.89 0.00 6.90 2,2-Dimethylbutane 0.34 0.00 0.48 Other C5 2.36 0.00 3.33

[0050] Examples 31-40

[0051] The two-stage hydrogenation reaction was carried out in an adiabatic bubbling bed tubular reactor with dimensions of φ25mm × 1500mm. The reactor was loaded with 100mL of catalyst, with Pd as the active component and Al2O3 as the support, and the Pd content was 0.30wt%. Inert ceramic balls were packed at the bottom of the reactor. Fresh catalyst was activated with hydrogen before feeding. Platinum resistance thermometers were installed at the top, middle, and bottom of the catalyst bed. The feed rate was controlled by a feed pump, and the system pressure was regulated by a back pressure valve.

[0052] The C5 fraction from the bottom of the reactor in step 3 is mixed with the hydrogenation liquid, then mixed with hydrogen gas, and enters the catalyst bed from the bottom of the reactor for hydrogenation reaction, which proceeds according to the set reaction conditions. The hydrogenated material enters a gas-liquid separator from the top of the hydrogenation reactor; the liquid phase enters the product storage tank; and unreacted hydrogen gas is depressurized by a regulating valve, metered by a wet gas meter, and then vented, or compressed and returned to the reaction system. The hydrogenation reaction products obtained in the examples were analyzed by chromatography, and the conversion rate and product selectivity were calculated. The reaction conditions for each example are shown in Table 4-1, and the results are shown in Table 4-2.

[0053] Table 4-1 Operating conditions for Examples 31-40

[0054] Mass air velocity (hr⁻¹) Reaction temperature (°C) Pressure (bar) H2 / diene molar ratio Example 31 2.0 30 3.0 1.00:1 Example 32 8.0 90 8.0 1.30:1 Example 33 6.0 35 4.0 1.10:1 Example 34 4.5 40 4.6 1.25:1 Example 35 4.0 55 5.0 1.15:1 Example 36 5.5 70 5.5 1.20:1 Example 37 4.2 45 5.5 1.12:1 Example 38 5.0 38 6.0 1.14:1 Example 39 5.5 60 5.5 1.00:1 Example 40 5.6 46 6.0 1.20:1

[0055] Table 4-2 GC analysis results of typical two-stage hydrogenation feedstocks and hydrogenation reaction solutions in Examples 31-40

[0056] Components Raw materials / wt% Hydrogenation liquid / wt% 1-Pentene 0.03 0.050 n-Pentane 0.61 0.820 Isoprene 0.00 0.000 trans-pentene-2 41.76 42.290 cispentene-2 20.88 21.150 2-Methyl-2-butene 0.25 0.250 trans-m-pentadiene 0.67 0.000 cyclopentadiene 0.00 0.000 cis-m-pentadiene 0.36 0.000 cyclopentene 24.73 24.500 cyclopentane 6.90 7.13 2,2-Dimethylbutane 0.48 0.48 Other C5 3.33 3.33

[0057] Examples 41-50

[0058] 2-Pentene is separated in a distillation column with 120–150 theoretical plates. The reboiler temperature is 56–85°C, the top temperature is 42–62°C, the reflux ratio is 10–30, and the operating pressure is 1.0–3.0 bar. Table 5-1 shows the operating conditions, and Table 5-2 shows the composition of the hydrogenated liquid feedstock, the top layer, and the reboiler in the distillation column.

[0059] Table 5-1 Operating conditions for Examples 41-50

[0060] Operating pressure (bar) Tower bottom temperature (°C) Tower top temperature (°C) reflux ratio Example 41 1.0 56 42 10﹕1 Example 42 3.0 85 62 30﹕1 Example 43 1.5 60 45 15﹕1 Example 44 2.3 68 52 25﹕1 Example 45 1.8 62 47 15﹕1 Example 46 2.5 70 55 20﹕1 Example 47 1.6 60 45 25﹕1 Example 48 2.4 66 50 18﹕1 Example 49 2.0 64 46 22﹕1 Example 50 2.2 61 45 21﹕1

[0061] Table 5-2 GC analysis results of typical two-stage hydrogenation reaction solutions, top and bottom of the column in Examples 41-50

[0062] Components Raw materials / wt% Top of the tower 2-pentene product / wt% C5 fraction in the bottom of the column / wt% 1-Pentene 0.050 0.08 0.00 n-Pentane 0.820 1.41 0.00 Isoprene 0.000 0.00 0.00 trans-pentene-2 42.286 65.68 0.00 cispentene-2 21.143 32.83 0.00 2-Methyl-2-butene 0.020 0.00 0.03 trans-m-pentadiene 0.000 0.00 0.02 cyclopentadiene 0.000 0.00 0.00 cis-m-pentadiene 0.000 0.00 0.01 cyclopentene 24.500 0.00 68.88 cyclopentane 7.13 0.00 20.05 2,2-Dimethylbutane 0.48 0.00 1.35 Other C5 3.33 0.00 9.36

[0063] Examples 51-60

[0064] The cyclopentene product is distilled by feeding the bottom product from the above-mentioned column into a distillation column. The theoretical plate number of the distillation column is 80–120. The operating pressure is 0.0–1.5 bar, the bottom temperature is 60–70 °C, the top temperature is 44–65 °C, and the reflux ratio is 5–15. Cyclopentene is obtained at the top of the column, and a heavy component rich in cyclopentane is obtained at the bottom. Table 6-1 shows the operating conditions, and Table 6-2 shows the composition of the hydrogenated liquid feedstock, the top portion, and the bottom portion of the distillation column.

[0065] Table 6-1 Operating conditions for Examples 51-60

[0066] Operating pressure (bar) Tower bottom temperature (°C) Tower top temperature (°C) reflux ratio Example 51 0.0 60 44 5﹕1 Example 52 1.5 70 65 15﹕1 Example 53 0.1 62 50 8﹕1 Example 54 0.3 65 52 12﹕1 Example 55 0.4 62 60 9﹕1 Example 56 0.5 65 55 10﹕1 Example 57 0.3 63 56 11﹕1 Example 58 0.4 66 50 10﹕1 Example 59 0.3 64 56 9﹕1 Example 60 0.2 62 54 10﹕1

[0067] Table 6-2 GC analysis results of distillation feedstock, top and bottom of column in typical steps of Example 51-60

[0068] Components Raw materials / wt% Top cyclopentene product / wt% C5 fraction in the bottom of the column / wt% 1-Pentene 0.00 0.00 0.00 n-Pentane 0.00 0.00 0.00 Isoprene 0.00 0.00 0.00 trans-pentene-2 0.00 0.00 0.00 cispentene-2 0.00 0.00 0.00 2-Methyl-2-butene 0.02 0.02 0.00 trans-m-pentadiene 0.02 0.03 0.00 cyclopentadiene 0.00 0.00 0.00 cis-m-pentadiene 0.01 0.01 0.00 cyclopentene 68.88 99.91 0.10 cyclopentane 20.05 0.03 65.10 2,2-Dimethylbutane 1.35 0.00 4.39 Other C5 9.36 0.00 30.42

[0069] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing C5 monoolefins, characterized in that, Includes the following steps: Step 1: The isoprene feedstock is distilled, and the bottom of the column yields a C5 fraction rich in isoprene, while the top of the column yields a light fraction containing isoprene, 2-methyl-1-butene, n-pentane, 2-methyl-2-butene and a small amount of trans-isoprene. Step 2: The C5 fraction rich in isoprene is introduced into the isothermal bubbling bed hydrogenation reactor along with hydrogen gas. The catalyst is Pd / Al2O3. A first-stage hydrogenation reaction is carried out. The conversion rate of the first-stage hydrogenation is controlled at 95-98%, and a first-stage hydrogenation reaction liquid is obtained. Step 3: Distill a section of the hydrogenation reaction solution to obtain 1-pentene at the top of the column; Step 4: The bottom liquid from Step 3 and hydrogen gas are fed together into an adiabatic bubbling bed hydrogenation reactor. The catalyst is Pd / Al2O3. A two-stage hydrogenation reaction is carried out, and the conversion rate of the two-stage hydrogenation is controlled to be >99.99% to obtain the two-stage hydrogenation reaction liquid. Step 5: The second-stage hydrogenation reaction solution is distilled to obtain 2-pentene at the top of the column; Step 6: Distill the bottom liquid from Step 5 to obtain cyclopentene product at the top of the column and a heavy component rich in cyclopentane at the bottom of the column.

2. The method for producing C5 monoolefins according to claim 1, characterized in that, In step 1, the theoretical number of distillation plates is 130–180, the operating pressure is 1.1–3.0 bar, the bottom temperature is 50–70°C, the top temperature is 40–50°C, and the reflux ratio is 8–30.

3. The method for producing C5 monoolefins according to claim 1, characterized in that, In step 2, the molar feed ratio of hydrogen to diene in the feed is 1.0–1.3:1, and the mass hourly space velocity (HHSV) is 2–8 hr. -1 The reaction pressure is 3–8 bar, the reaction temperature is 30–90 °C, and the mass ratio of hydrogenated liquid circulation to fresh feed is 8–15:

1.

4. The method for producing C5 monoolefins according to claim 1, characterized in that, In step 3, the theoretical number of distillation plates is 120-150, the operating pressure is 1.0-3.0 bar, the bottom temperature is 55-80℃, the top temperature is 40-60℃, and the reflux ratio is 10-30.

5. The method for producing C5 monoolefins according to claim 1, characterized in that, In step 4, the molar feed ratio of hydrogen to diene in the feed is 1.0–1.3:1, and the mass hourly space velocity (HHSV) is 2–8 hr. -1 The reaction pressure is 3–8 bar, the reaction temperature is 30–90 °C, and the mass ratio of hydrogenated liquid circulation to fresh feed is 8–15:

1.

6. The method for producing C5 monoolefins according to claim 1, characterized in that, In step 5, the theoretical number of distillation plates is 120–150, the operating pressure is 1.0–3.0 bar, the bottom temperature is 56–85°C, the top temperature is 42–62°C, and the reflux ratio is 10–30.

7. The method for producing C5 monoolefins according to claim 1, characterized in that, Step 6, the total distillation has a theoretical plate number of 120-150, an operating pressure of 0.0-1.5 bar, a bottom temperature of 60-70°C, a top temperature of 44-65°C, and a reflux ratio of 5-15.