A method and system for diisobutylene production

Abstract

The application particularly relates to a diisobutylene preparation method and system, and belongs to the technical field of petroleum chemical industry.The method comprises the following steps: mixing isobutylene raw materials, inert components and deoxidized water and heating to a first temperature to obtain a premix; subjecting the premix to a first polymerization reaction to obtain a pre-preparation at a second temperature; cooling the pre-preparation to a third temperature, subjecting the pre-preparation to a second polymerization reaction to obtain a polymerization product; subjecting the polymerization product to catalytic distillation to obtain light polymerization product, azeotrope and heavy polymerization product; and subjecting the heavy polymerization product to first precise fractionation to obtain diisobutylene.The method can ensure that the isobutylene conversion rate is greater than or equal to 99.0%, and diisobutylene products with a mass fraction of 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene greater than or equal to 99.5% and an isobutylene yield greater than or equal to 99.0% are obtained.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering, and specifically relates to a method and system for preparing diisobutylene. Background Technology

[0002] The diisobutylene (DIB) mentioned in this invention is 2,4,4-trimethylpentene, comprising two components: 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene. As an important organic chemical raw material, diisobutylene can generate a series of fine chemical intermediates and is widely used in plastic additives, rubber additives, lubricants, antioxidants, surfactants, synthetic detergents, and other fields.

[0003] Currently, the main raw materials for producing diisobutylene products are steam cracking mixed C4 or FCC mixed C4. Isobutylene (IB) in the mixed C4 dimers to form DIB under the action of a solid acid catalyst. Besides the main reaction mentioned above, numerous side reactions also occur. For example, IB reacts with DIB to form a trimer (TIB), and IB further reacts with TIB to form a tetramer (TEB). Other examples include isobutylene and 1-butene dimerizing to form 2,2-dimethylhexene and 2,3-dimethylhexene, and isobutylene and 2-butene dimerizing to form 2,3,3-trimethylpentene, 2,3,4-trimethylpentene, 2,2,4-trimethylpentane, and 3,4,4-trimethylpentene, etc. The components in the resulting dimers are mainly low molecular weight compounds. The mass fractions of the C8 olefin component, dimer, trimer, and tetramer were 5.61%, 64.82%, 27.57%, and 2.00%, respectively. The mass fraction of the dimer in the resulting composite was only 64.82%, and the dimer contained a large number of isomers with similar boiling points. The target products, 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene, accounted for only 69.95% of the mass fraction of the dimer. Therefore, the production of diisobutylene using existing technology suffers from low product yield and low purity of diisobutylene in the product. Summary of the Invention

[0004] The purpose of this application is to provide a method and system for preparing diisobutylene, which solves the technical problems of low product yield and low product purity in existing diisobutylene preparation methods.

[0005] To address the aforementioned technical problems, embodiments of the present invention provide a method for preparing diisobutylene, comprising the following steps:

[0006] Isobutylene raw material, inert component and deoxygenated water are mixed and heated to a first temperature to obtain a premix;

[0007] The premix is ​​subjected to a first superposition reaction to obtain a preform at a second temperature;

[0008] The preform is cooled to a third temperature and subjected to a second superposition reaction to obtain a superposition compound;

[0009] The composite was subjected to catalytic distillation to obtain a light composite, a cyclic inert component, an azeotrope, and an overlap.

[0010] The overlapping material was subjected to a first precision fractionation to obtain diisobutylene;

[0011] in:

[0012] The isobutylene raw material is isobutylene with a mass fraction ≥ 99.0%;

[0013] The mass percentage of isobutylene in the preform is ≤20%;

[0014] The first temperature is 50-70℃, the second temperature is 70-90℃, and the third temperature is 50-65℃.

[0015] Optionally, the liquid hourly space velocity (LHSV) for both the first and second superposition reactions is 0.5-5.0 h⁻¹. -1 The reaction pressure of the first superposition reaction is 0.85-2.10 MPa, and the reaction pressure of the second superposition reaction is 0.80-2.00 MPa.

[0016] Optionally, the mass percentage of tert-butanol in the overlap is ≤0.01%.

[0017] Optionally, the following steps may also be included:

[0018] The lightly stacked material is condensed to obtain non-condensable gas and condensate;

[0019] The condensate is refluxed to the catalytic distillation;

[0020] The cyclic inert component is mixed with the premix.

[0021] Optionally, the mass ratio of the isobutylene feedstock to the recycled inert component is 1:(1-3).

[0022] Optionally, the following steps may also be included:

[0023] The azeotrope is subjected to a second precision fractionation to obtain a cycle inhibitor and a second azeotrope;

[0024] The cycle inhibitor is mixed with the premix;

[0025] The second azeotrope was split to obtain a first reflux and a second reflux;

[0026] The second reflux product is used as the raw material for the catalytic distillation;

[0027] in:

[0028] The mass ratio of the azeotrope to the isobutylene raw material is 5%-35%;

[0029] The cycling inhibitor is tert-butanol with a molar percentage ≥99.99%.

[0030] Optionally, the molar ratio of the cycling inhibitor to the isobutylene feedstock is (0.05-0.10):1.

[0031] Optionally, the inert component includes any one or more combinations of butane components, pentane components, C4-C6 stable light hydrocarbons, and hydrocracked light naphtha.

[0032] Based on the same inventive concept, embodiments of the present invention also provide a diisobutylene preparation system applicable to any of the above methods, comprising a first superimposed reactor, a second superimposed reactor, a catalytic distillation column, and a diisobutylene separation column; the inlet of the first superimposed reactor is connected to a feed source, the outlet of the first superimposed reactor is connected to the inlet of the second superimposed reactor, and the outlet of the second superimposed reactor is connected to the inlet of the catalytic distillation column; the catalytic distillation column is provided with a first top outlet, a first bottom outlet, a first side outlet, and a second side outlet, the second side outlet being located on the upper sidewall of the catalytic distillation column, and the first bottom outlet being connected to the inlet of the diisobutylene separation column; the diisobutylene separation column is provided with a second top outlet and a second bottom outlet, the second top outlet being used to discharge diisobutylene.

[0033] Optionally, the austenitizing temperature is 810-900℃.

[0034] Optionally, it also includes an inhibitor separation tower, the inlet of which is connected to the first side outlet. The inhibitor separation tower is provided with a third top outlet and a third bottom outlet. The third bottom outlet is connected to the feed source through a second reflux branch pipe, and the third top outlet is connected to the catalytic distillation tower through a third reflux branch pipe. The second side outlet is connected to the feed source through a first reflux branch pipe.

[0035] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0036] This invention provides a method for preparing diisobutylene, comprising the following steps: mixing isobutylene raw material, an inert component, and deoxygenated water and heating to a first temperature to obtain a premix; subjecting the premix to a first superposition reaction to obtain a preform at a second temperature; cooling the preform to a third temperature and subjecting it to a second superposition reaction to obtain a superposition compound; subjecting the superposition compound to catalytic distillation to obtain a light superposition compound, a recycled inert component, an azeotrope, and an overlap compound; subjecting the overlap compound to a first precision fractionation to obtain diisobutylene; wherein: the isobutylene raw material is isobutylene with a mass fraction ≥99.0%; the mass percentage of isobutylene in the preform is ≤20%; the first temperature is 50-70℃, the second temperature is 70-90℃, and the third temperature is 50-65℃. This method uses high-purity isobutylene as raw material, avoiding the situation where a large number of by-reaction products with boiling points close to the target product are present when using steam cracking mixed C4 or FCC mixed C4 as raw material. Through two superposition reactions and two catalytic distillations, high-purity diisobutylene is prepared from high-purity isobutylene raw material.

[0037] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a flowchart of a method for preparing diisobutylene provided in an embodiment of the present invention;

[0040] Figure 2 This is a graph showing the relationship between the composition of the diisobutylene product prepared by a diisobutylene preparation method provided in this embodiment of the invention and the methanol / isobutylene molar ratio.

[0041] Figure 3 This is a graph showing the relationship between the composition of the diisobutylene product prepared by a diisobutylene preparation method provided in this embodiment of the invention and the isool / isobutylene molar ratio.

[0042] Figure 4 This is a schematic diagram of a diisobutylene preparation system provided in an embodiment of the present invention.

[0043] Figure label:

[0044] 10-First superimposed reactor; 11-Second superimposed reactor; 12-Catalytic distillation column; 121-First reflux branch; 13-Inhibitor separation column; 131-Second reflux branch; 132-Third reflux branch; 14-Diisobutylene separation column. Detailed Implementation

[0045] The present invention will be described in detail below with reference to specific embodiments and examples, thereby making the advantages and various effects of the present invention more clearly apparent. Those skilled in the art should understand that these specific embodiments and examples are for illustrative purposes only and are not intended to limit the present invention.

[0046] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of any conflict, this specification shall prevail. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of protection of this invention. For example, room temperature may refer to a temperature in the range of 10–35°C.

[0047] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0048] The technical solution of this application embodiment is to solve the above-mentioned technical problems, and the general idea is as follows:

[0049] According to a typical embodiment of the present invention, a method for preparing diisobutylene is provided, comprising the following steps:

[0050] S1. Mix isobutylene raw material, inert component and deoxygenated water and heat to a first temperature to obtain a premix;

[0051] S2. The premix is ​​subjected to a first superposition reaction to obtain a preform at a second temperature;

[0052] S3. Cool the preform to a third temperature and undergo a second superposition reaction to obtain the superposition compound;

[0053] S4. The composite is subjected to catalytic distillation to obtain a light composite, a circulating inert component, an azeotrope, and an overlapping composite;

[0054] S5. The overlapping material is subjected to a first precision fractionation to obtain diisobutylene;

[0055] in:

[0056] The isobutylene raw material is isobutylene with a mass fraction ≥ 99.0%;

[0057] The mass percentage of isobutylene in the preform is ≤20%;

[0058] The first temperature is 50-70℃, the second temperature is 70-90℃, and the third temperature is 50-65℃.

[0059] Overall, the above preparation method obtains high-purity diisobutylene from isobutylene raw material with a mass fraction of ≥99.0% via steps S1-S5. Specifically, step S1 yields a preheated premix raw material; step S2 allows for the initial conversion of isobutylene, with the conversion rate stabilized at 45-65% by controlling the above parameters, thus ensuring that the mass percentage of isobutylene in the preform is ≤20%; step S3 yields the composite. Since the mass percentage of isobutylene in the preform is ≤20%, the temperature rise of the composite reaction in step S3 is relatively small, thereby avoiding the need for external circulation and other measures. To reduce the reactor temperature rise and avoid introducing byproducts, step S4 separates the composite into light composite, circulating inert component, azeotrope, and overlapping composite. The light composite includes C2 and C3 components and a small amount of C4 component. The circulating inert component has a composition that is basically the same as the inert component. The overlapping composite includes dimer, trimer, and tetramer. The azeotrope includes dimer and tert-butanol. Further step S5 separates the trimer and tetramer from the dimer in the overlapping composite to obtain diisobutylene and heavy components with the composition of 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene.

[0060] Specifically, the chelation reaction mechanism of isobutylene is as follows:

[0061]

[0062] The heat of reaction for the dimerization of isobutylene to form isooctene is -82.8 kJ / mol, which is more than twice that of the etherification reaction of isobutylene with methanol to form MTBE (-39.7 kJ / mol). Therefore, the isobutylene dimerization reaction is more prone to catalyst bed overheating due to the stronger exothermic reaction than the etherification reaction, leading to high-temperature catalyst deactivation. Since the acidic cation exchange resin catalysts commonly used in dimerization reactions suffer severe deactivation due to polymer chain scission at temperatures exceeding 120°C, the maximum heat resistance temperature of acidic cation exchange resin catalysts D-005, D-006, QRE-01, and their equivalent dimerization catalysts is 120°C. Therefore, certain measures must be taken to reduce the temperature rise of the reactor in the dimerization reaction to prevent catalyst deactivation.

[0063] The widely used method for controlling reactor temperature rise is external circulation cooling. This method involves cooling a portion of the reacted material in an external cooler before circulating it back into the reactor to achieve circulating cooling. The disadvantage of this method is that a large amount of dimer is back-mixed into the reactor inlet in the circulating reaction products, which increases the yield of by-reaction products such as the dimer reacting with isobutylene to form trimer, and the trimer reacting with isobutylene to form tetramer, thus reducing the yield of the target product.

[0064] This invention dilutes the concentration of isobutylene in the feed of the superimposed reactor by adding an inert component in step S1, thereby moderating the reaction intensity and reducing the reactor temperature rise. The inert component is stable and does not react with isobutylene to generate byproducts. This avoids the problem of increased byproducts such as trimers and tetramers caused by external cooling to remove the heat of reaction and then returning the recycled dimers and other reaction products to the reactor, resulting in a significant improvement in the quality of the product generated from the reaction.

[0065] The advantages of catalytic distillation in this invention are: the dimer concentration can be kept at a low level in the reaction zone of the distillation equipment, thereby inhibiting subsequent polymer reactions; in addition, catalytic distillation can directly use the heat of reaction for the separation process, thereby reducing energy consumption; at the same time, the reaction temperature is easy to control, there are no obvious hot spots, and no cooling equipment is required.

[0066] As an optional implementation, the liquid hourly space velocity of both the first and second superposition reactions is 0.5-5.0 h⁻¹, the reaction pressure of the first superposition reaction is 0.85-2.10 MPa, and the reaction pressure of the second superposition reaction is 0.80-2.00 MPa.

[0067] The reason for controlling the above numerical range is that the isobutylene superposition reaction is a liquid-phase reaction carried out under the action of a catalyst. Within this pressure range, it can be ensured that the first superposition reaction and the second superposition reaction are carried out in the liquid phase. When the content of lighter components such as propane in the circulating inert component is high, the reaction pressure approaches the upper limit. When the content of heavier components such as pentane in the circulating inert component is low, the reaction pressure approaches the lower limit.

[0068] As an optional implementation, the mass percentage of tert-butanol in the overlap is ≤0.01%.

[0069] The reason for controlling the above numerical range is that when the mass percentage of tert-butanol in the overlap is high, it will affect the purity of the diisobutylene product.

[0070] As an optional implementation, the following steps are also included:

[0071] S6. The lightly stacked material is condensed to obtain non-condensable gas and condensate;

[0072] S7. The condensate is refluxed to the catalytic distillation;

[0073] S8. The cyclic inert component is mixed with the premix.

[0074] Through steps S6-S8, the reuse of light components and the recycling of inert components are achieved, avoiding the drawbacks of continuously using large quantities of fresh inert components. Specifically, in step S6, the light composite is condensed and separated into non-condensable gas and condensate. The non-condensable gas serves as the light component for further processing at the boundary of catalytic distillation. Then, in step S7, the condensate is returned to the distillation column of the catalytic distillation for mass and heat transfer, and the isobutylene in the condensate undergoes further chelation reaction. Then, in step S8, the recycled inert component is returned to be mixed with the premix and used as a recycled feedstock to replenish the inert components, thus achieving the recycling of inert components and avoiding the drawbacks of continuously using large quantities of fresh inert components.

[0075] Specifically, the circulating inert component is extracted from the upper sidewall of the distillation column used in catalytic distillation. Its advantages are: on the one hand, it relatively reduces the total mass of the light aggregate, thereby relatively reducing the load on the light aggregate during condensation in the catalytic distillation process; on the other hand, the temperature of the circulating inert component is 55-80℃, which can transfer heat to the lower temperature isobutylene raw material and deoxygenated water after mixing with the premix, thereby increasing the temperature of the premix and relatively reducing the heat load required to heat to the first temperature, thus reducing the energy consumption of the entire preparation method by 5%-10%.

[0076] As an optional implementation, the mass ratio of the isobutylene feedstock to the recycled inert component is 1:(1-3).

[0077] The reason for controlling the above ratio range is that the addition of inert components dilutes the concentration of isobutylene in the feed of the first superposition reaction. By controlling the mass ratio of the above components, the mass percentage of isobutylene in the feed of the first superposition reaction can be reduced to the range of 25%-50%, which moderates the reaction intensity and allows the heat of reaction to be transferred to the inert components, thereby reducing the temperature rise of the reactor bed in the first superposition reaction.

[0078] As an optional implementation, the following steps are also included:

[0079] S9. The azeotrope is subjected to a second precision fractionation to obtain a cycle inhibitor and a second azeotrope;

[0080] S10. Mix the cycle inhibitor with the premix;

[0081] S11, the second azeotrope is split to obtain a first reflux and a second reflux;

[0082] S12. The second reflux is used as the raw material for the catalytic distillation;

[0083] in:

[0084] The mass ratio of the azeotrope to the isobutylene raw material is 5%-35%;

[0085] The cycling inhibitor is tert-butanol with a molar percentage ≥99.99%.

[0086] Because isobutylene undergoes a rapid polymerization reaction, uncontrolled reactions can lead to the formation of numerous byproducts, such as polymers, resulting in a decrease in the diisobutylene yield. Therefore, steps S9-S12 involve recycling the inhibitor, which, combined with the deoxygenated water from step S1, further inhibits the reaction and improves the inhibitor's utilization rate. Specifically, in step S9, the azeotrope is separated in a second precision distillation column. The pressure of the second precision distillation is controlled to be lower than that of the catalytic distillation, reducing the molar percentage of tert-butanol in the azeotrope from 70-80% to 60-70%. This results in tert-butanol with a molar percentage ≥99.99% (i.e., the circulating inhibitor) at the bottom of the column, and a second azeotrope of diisobutylene and tert-butanol with a molar composition of 60.0%-70.0% (i.e., the second azeotrope) at the top of the column. In step S10, the circulating inhibitor is refluxed to be mixed with the premix to replenish the inhibitor from the first superposition reaction, thus achieving inhibitor recycling and improving inhibitor utilization. In step S11, the second azeotrope is split to obtain a first reflux and a second reflux. The first reflux is sent to the third catalytic distillation column for further reaction. In step S12, the second reflux is refluxed to the catalytic distillation column as a raw material for catalytic distillation, thereby achieving effective utilization of the material while ensuring no side reactions occur.

[0087] Preferably, the cycling inhibitor comprises any one or more combinations of methanol, ethanol, isopropanol, and tert-butanol (TBA). Alcohols are highly polar and readily adsorb onto the active sites of the catalyst, reacting with sulfonic acid groups in the following reactions:

[0088]

[0089] Due to SO3 - ROH2 + The acidity of isobutylene is weaker than that of H+, thus reducing the activity of the resin catalyst and the polymerization rate, which is beneficial for inhibiting the formation of trimers and tetramers. In addition, since isobutylene also undergoes etherification reactions with non-tertiary alcohols such as methanol and ethanol, and the etherification reaction rate is faster than the isobutylene dimerization reaction rate, this further reduces the formation of polymers, increasing the mass fraction of dimers in the final reaction product to >80% and reducing the mass fraction of tetramers to <0.1%, resulting in a significant improvement in product quality.

[0090] Using methanol and ethanol as inhibitors, respectively, the relationship between the composition of the isobutylene dimerization reaction products and the molar ratio of alcohol to olefin in the presence of Amberlyst 35 cation exchange resin catalyst is shown in the figure. Figure 2 and Figure 3 .Depend on Figure 2 and Figure 3 It is evident that as the alcohol-to-olefin ratio increases, the mass fraction of the composite in the product continuously decreases. When the alcohol-to-olefin ratio is 1, the mass fraction of the composite almost drops to 0. When small molecule alcohols such as methanol and ethanol are used as inhibitors, the alcohol-to-olefin ratio is generally between 0.2 and 0.6. Under these substoichiometric conditions, the reaction product is mainly a mixture of trimethylpentene and MTBE or ETBE. When large molecule alcohols such as isopropanol and sec-butanol are used as inhibitors, their activity in the etherification reaction with isobutylene is low, and the thermodynamic equilibrium conversion rate is low. The alcohol consumed in the etherification reaction is correspondingly reduced. Even when the alcohol / olefin ratio is as low as 0.05, there will be enough alcohol adsorbed on the active site of the catalyst, maintaining a high dimerization selectivity. When tertiary alcohols (such as TBA) are selected as inhibitors, they cannot undergo etherification with isobutylene due to steric hindrance, thus the final reaction product does not contain ether-containing oxygenated compounds.

[0091] In this invention, the deoxygenated water added in step S1 is specifically injected into the isobutanol raw material. Under the action of an acidic cation exchange resin catalyst, the deoxygenated water undergoes a hydration reaction with isobutene to generate tert-butanol, as shown in the following reaction formula:

[0092]

[0093] The reaction of IB with H2O to produce TBA is a reversible reaction. When the tert-butanol content in the system is too low, the TBA content in the system can be increased by appropriately increasing the amount of deoxygenated water added. Conversely, when the tert-butanol content in the system is too high, the TBA content in the system can be reduced by appropriately decreasing the amount of water added. In addition, by intermittently or continuously injecting water into the system to compensate for the tert-butanol carried away by the products of catalytic distillation and the first precision fractionation, the tert-butanol content in the entire circulating system can be kept constant.

[0094] On the other hand, since the above-mentioned azeotrope includes tert-butanol and diisobutene, if the azeotrope is directly recycled to the reaction section, the excessive diisobutene will react with the isobutene in the raw material to form a trimer, and the trimer will then react with the isobutene to form a tetramer, thereby reducing the yield of the diisobutene product. Therefore, tert-butanol should be separated from the azeotrope of diisobutene and tert-butanol.

[0095] Because azeotropes containing diisobutylene and tert-butanol are sensitive to pressure—for example, at pressures of 0.1 MPa, 0.2 MPa, 0.8 MPa, and 1.0 MPa, the azeotropic temperatures of the azeotropes are 77.63℃, 97.34℃, 146.28℃, and 155.61℃, respectively, and the azeotropic compositions (mass fractions) of tert-butanol are 0.5508, 0.6086, 0.6896, and 0.6924, respectively—tert-butanol can be separated from diisobutylene by changing the pressure.

[0096] The azeotrope is separated by a second precision distillation to obtain a circulating inhibitor and a second azeotrope. Specifically, the pressure of the second precision distillation column is lower than that of the catalytic distillation column. Due to the pressure change, the composition of tert-butanol in the azeotrope decreases, thus obtaining high-purity tert-butanol at the bottom of the column. This portion of tert-butanol is recycled as a circulating inhibitor to be mixed with the premix and continues to act as an inhibitor for the first superposition reaction. The azeotrope of diisobutylene and tert-butanol with a lower molar composition of tert-butanol obtained at the top of the column is the second azeotrope. This portion of the azeotrope is split to obtain a first reflux and a second reflux. The first reflux is refluxed back into the second precision distillation column, and the second reflux is returned to the catalytic distillation column as feedstock for the catalytic distillation column.

[0097] As an optional implementation, the molar ratio of the cycling inhibitor to the isobutylene feedstock is (0.05-0.10):1.

[0098] The reason for controlling the above-mentioned ratio range is that when the amount of circulating inhibitor is too low, it cannot effectively reduce the formation of trimers and tetramers. When the amount of circulating inhibitor is too high, it will not only increase the energy consumed during inhibitor separation, but also cause a large amount of inhibitor to enter the bottom of the catalytic distillation column, where it mixes with the superimposed material during the first precision fractionation. During the separation process, the mixed inhibitor forms an azeotrope with diisobutylene, resulting in the inability to obtain high-purity diisobutylene in the first precision fractionation. Therefore, controlling the molar ratio within the above-mentioned range prevents the adverse effects caused by being too high or too low.

[0099] As an optional implementation, the inert component includes any one or more combinations of butane components, pentane components, C4-C6 stable light hydrocarbons, and hydrocracked light naphtha.

[0100] Please refer to Figure 4According to another typical embodiment of the present invention, a diisobutylene preparation system suitable for any of the above methods is provided, comprising a first superimposed reactor 10, a second superimposed reactor 11, a catalytic distillation column 12, and a diisobutylene separation column 14; the inlet of the first superimposed reactor 10 is connected to a feed source, the outlet of the first superimposed reactor 10 is connected to the inlet of the second superimposed reactor 11, and the outlet of the second superimposed reactor 11 is connected to the inlet of the catalytic distillation column 12; the catalytic distillation column 12 is provided with a first top outlet, a first bottom outlet, a first side outlet, and a second side outlet, the second side outlet being located on the upper sidewall of the catalytic distillation column 12, and the first bottom outlet being connected to the inlet of the diisobutylene separation column 14; the diisobutylene separation column 14 is provided with a second top outlet and a second bottom outlet, the second top outlet being used to discharge diisobutylene. A first superposition reactor 10 is provided to carry out a first superposition reaction, a second superposition reactor 11 is provided to carry out a second superposition reaction, a catalytic distillation column 12 is provided to carry out catalytic distillation, and a diisobutylene separation column 14 is provided to carry out a first precision fractionation. The first top outlet of the catalytic distillation column 12 is used to discharge light superposition material, the first bottom outlet is used to discharge superposition material, the first side outlet is used to extract azeotropic material, and the second side outlet is used to extract circulating inert components. The second top outlet of the diisobutylene separation column 14 is used to discharge diisobutylene, and the second bottom outlet is used to discharge heavy components.

[0101] It should be noted that the first superposition reactor 10 is preferably a water-cooled tubular reactor. The water-cooled tubular reactor is similar to a shell-and-tube cooler, with the catalyst packed in the tubes and the isobutylene feedstock flowing through them. Under the action of the catalyst, a superposition reaction occurs, releasing heat. The shell-side medium can be the second reflux, which absorbs the reaction heat in the tubes of the first superposition reactor 10 before entering the catalytic distillation column, saving energy. The shell-side medium can also be circulating water or other cooling media to remove the reaction heat. This reactor has a wide axial temperature distribution range. In the initial stage, the highest bed temperature can be designed to be around 1 / 3 of the way from the inlet. As the catalyst activity decreases, the highest temperature gradually moves upward. When it reaches about 3 / 4 of the height from the inlet, the catalyst activity no longer meets the design requirements, and catalyst replacement needs to be considered. The water-cooled tubular reactor can effectively reduce the reactor temperature rise, which is beneficial for suppressing the formation of trimers and tetramers.

[0102] It should be noted that the second composite reactor 11 is preferably an expanded bed reactor. Under the action of the rising fluid, the catalyst particles in the expanded bed reactor have irregular rotation and slight disturbance, the pressure drop of the entire bed is small, and the temperature distribution of the entire reactor is relatively uniform. This allows the catalyst bed to be controlled to operate within a suitable temperature range, which is also beneficial for suppressing the formation of trimers and tetramers.

[0103] As an optional implementation, an inhibitor separation tower 13 is also included. The inlet of the inhibitor separation tower 13 is connected to the first side outlet. The inhibitor separation tower 13 has a third top outlet and a third bottom outlet. The third bottom outlet is connected to the feed source through a second reflux branch pipe 131, and the third top outlet is connected to the catalytic distillation tower 12 through a third reflux branch pipe 132. The second side outlet is connected to the feed source through a first reflux branch pipe 121. By setting up the inhibitor separation tower 13, the circulating inhibitor in the azeotrope is separated. The second azeotrope is discharged through the third top outlet, and the circulating inhibitor is discharged through the third bottom outlet.

[0104] The present application will now be described in detail with reference to embodiments, comparative examples and experimental data.

[0105] Example 1

[0106] This embodiment provides a method for preparing diisobutylene, including the following steps:

[0107] S1. The mass flow rate is 3000 kg / h. -1 Isobutylene raw material, 30 kg / h -1 Inert components and 18 kg.h -1 The deoxygenated water was mixed and heated to 60°C to obtain a premix.

[0108] The isobutylene raw material is isobutylene with a mass fraction of ≥99.0%.

[0109] S2. The premix is ​​fed into the first superposition reactor 10 to carry out the first superposition reaction, and a preform at 80°C is obtained.

[0110] The liquid hourly space velocity (LHSV) for the first superposition reaction was 1.0 h⁻¹. -1 The reaction pressure for the first superposition reaction is 1.6 MPa.

[0111] S3. Cool the preform to 55°C and pass it into the second superposition reactor 11 to carry out the second superposition reaction to obtain the superposition compound.

[0112] The liquid hourly space velocity (LHSV) for the second superposition reaction was 1.0 h⁻¹. -1 The reaction pressure for the second superposition reaction is 1.5 MPa.

[0113] S4. The composite is fed into catalytic distillation column 12 for catalytic distillation. A light composite is obtained at the first top outlet, an azeotrope is extracted at the first side outlet, a circulating inert component is extracted at the second side outlet, and a composite is obtained at the first bottom outlet.

[0114] The mass ratio of the azeotrope extracted from the first outlet to the isobutylene raw material is 5%-35%.

[0115] S5. The superimposed material is passed into diisobutylene separation tower 14 for the first precision fractionation, and 2808 kg / h of diisobutylene is obtained at the second top outlet. -1 219 kg / h was obtained at the second bottom outlet. -1 Recombination components.

[0116] S6. The lightly stacked material is condensed to obtain 21 kg·h. -1 Non-condensable gases and condensates.

[0117] S7. Return the condensate to the distillation column of the catalytic distillation.

[0118] S8. The circulating inert component is introduced into the first reflux branch pipe 121 and mixed with the premix.

[0119] Among them, the mass ratio of isobutylene raw material to recycled inert component is controlled to be 1:(1-3).

[0120] S9. The azeotrope is passed into the inhibitor separation tower 13 for a second precision fractionation. The circulating inhibitor is obtained at the third bottom outlet, and the second azeotrope is obtained at the third top outlet.

[0121] The molar ratio of the controlled cycle inhibitor to isobutylene feedstock is (0.05-0.10):1.

[0122] S10. The circulation inhibitor is introduced into the second reflux branch 131 and mixed with the premix.

[0123] S11, the second azeotrope is split to obtain the first reflux and the second reflux.

[0124] S12. The second reflux product is fed into the catalytic distillation column 12 through the third reflux branch pipe 132 as the feedstock for catalytic distillation. The feed and discharge data are shown in Table 1, and the reaction parameters of each unit are shown in Table 2.

[0125] Table 1. Feed and discharge data in Example 1

[0126]

[0127] Table 2 shows the reaction parameters of each device in Example 1.

[0128]

[0129] In summary, in this embodiment, the isobutylene conversion rate is 99.3%, the diisobutylene product yield is 92.1%, and the mass fraction of 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene in the diisobutylene product is 99.6%. However, when using existing technologies to produce diisobutylene, the yields of the two components are generally less than 80%, and the purity of 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene in the product is generally less than 95.0%. Compared with existing methods, the method provided by this invention can increase the diisobutylene yield by at least 10 percentage points, and the purity of 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene in the product can reach over 99.5%.

[0130] Appendix Figure 2 and Figure 3 Detailed explanation:

[0131] like Figure 2 and Figure 3 The figures show the relationship between the composition of the diisobutylene product prepared by the diisobutylene preparation method provided in this embodiment of the invention and the molar ratio of methanol / isobutylene, and the relationship between the composition of the diisobutylene product prepared by the diisobutylene preparation method provided in this embodiment of the invention and the molar ratio of isool / isobutylene, respectively. As can be seen from the figures, the composition of the diisobutylene product prepared by the diisobutylene preparation method provided in this embodiment of the invention... Figure 2 and Figure 3 It is evident that as the alcohol-to-olefin ratio increases, the mass fraction of the composite in the product continuously decreases. When the alcohol-to-olefin ratio is 1, the mass fraction of the composite almost drops to 0. When small molecule alcohols such as methanol and ethanol are used as inhibitors, the alcohol-to-olefin ratio is generally between 0.2 and 0.6. Under these substoichiometric conditions, the reaction product is mainly a mixture of trimethylpentene and MTBE or ETBE. When large molecule alcohols such as isopropanol and sec-butanol are used as inhibitors, their activity in the etherification reaction with isobutylene is low, and the thermodynamic equilibrium conversion rate is low. The alcohol consumed in the etherification reaction is correspondingly reduced. Even when the alcohol / olefin ratio is as low as 0.05, there will be enough alcohol adsorbed on the active site of the catalyst, maintaining a high dimerization selectivity. When tertiary alcohols (such as TBA) are selected as inhibitors, they cannot undergo etherification with isobutylene due to steric hindrance, thus the final reaction product does not contain ether-containing oxygenated compounds.

[0132] Finally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0133] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0134] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing diisobutylene, characterized in that, Includes the following steps: Isobutylene raw material, inert component and deoxygenated water are mixed and heated to a first temperature to obtain a premix; The premix is ​​subjected to a first superposition reaction to obtain a preform at a second temperature; The preform is cooled to a third temperature and subjected to a second superposition reaction to obtain a superposition compound; The composite was subjected to catalytic distillation to obtain a light composite, a cyclic inert component, an azeotrope, and an overlap. The overlapping material was subjected to a first precision fractionation to obtain diisobutylene; The circulating inert component is extracted from the upper sidewall of the distillation column used for catalytic distillation and refluxed to be mixed with the premix. The azeotrope is separated in a second precision distillation column. The pressure of the second precision distillation is controlled to be lower than that of the catalytic distillation, so that the molar percentage of tert-butanol in the azeotrope is reduced from 70%-80% to 60%-70%. Thus, tert-butanol with a molar percentage ≥99.99% is obtained at the bottom of the column, which is the recycling inhibitor. At the top of the column, an azeotrope of diisobutylene and tert-butanol with a molar composition of 60.0%-70.0% is obtained, which is the second azeotrope. The cycle inhibitor is mixed with the premix; The second azeotrope was split to obtain a first reflux and a second reflux; The second reflux material, after recovering the heat of reaction from the first superposition reaction, is used as the feed for the catalytic distillation; in: The isobutylene raw material is isobutylene with a mass fraction ≥ 99.0%; The mass percentage of isobutylene in the preform is ≤20%; The first temperature is 50-70℃, the second temperature is 70-90℃, and the third temperature is 50-65℃; the reaction pressure of the first superposition reaction is 0.85-2.10 MPa, and the reaction pressure of the second superposition reaction is 0.80-2.00 MPa. The inert components include any one or more combinations of butane components, pentane components, C4-C6 stable light hydrocarbons and hydrocracked light naphtha. The mass ratio of the azeotrope to the isobutylene raw material is 5%-35%; The molar ratio of the cycling inhibitor to the isobutylene feedstock is (0.05-0.10):1; The mass ratio of the isobutylene feedstock to the recycled inert component is 1:(1-3), which reduces the mass percentage of isobutylene in the first superposition reaction feed to 25%-50%.

2. The method for preparing diisobutylene according to claim 1, characterized in that, The liquid hourly space velocity (LHSV) for both the first and second superposition reactions is 0.5–5.0 h⁻¹. -1 .

3. The method for preparing diisobutylene according to claim 1, characterized in that, The mass percentage of tert-butanol in the overlap is ≤0.01%.

4. The method for preparing diisobutylene according to claim 1, characterized in that, It also includes the following steps: The lightly stacked material is condensed to obtain non-condensable gas and condensate; The condensate is refluxed to the catalytic distillation.

5. A diisobutylene preparation system applicable to the method described in any one of claims 1-4, characterized in that, It includes a first superimposed reactor (10), a second superimposed reactor (11), a catalytic distillation column (12), and a diisobutylene separation column (14); The inlet of the first composite reactor (10) is connected to the feed source, the outlet of the first composite reactor (10) is connected to the inlet of the second composite reactor (11), and the outlet of the second composite reactor (11) is connected to the inlet of the catalytic distillation tower (12). The catalytic distillation column (12) is provided with a first top outlet, a first bottom outlet, a first side outlet and a second side outlet. The second side outlet is located on the side wall of the upper part of the catalytic distillation column (12). The first bottom outlet is connected to the inlet of the diisobutylene separation column (14). The diisobutylene separation tower (14) is provided with a second top outlet and a second bottom outlet, the second top outlet being used to discharge diisobutylene; The first superimposed reactor (10) is a water-cooled tubular reactor with a catalyst in the tube side. Isobutylene feedstock flows through the tube side and undergoes a superimposed reaction under the action of the catalyst, releasing heat. The shell side medium is the second reflux. The second reflux absorbs the reaction heat in the tube side of the first superimposed reactor before entering the catalytic distillation tower. The second superimposed reactor (11) is an expanded bed reactor.

6. The diisobutylene preparation system according to claim 5, characterized in that, It also includes an inhibitor separation tower (13), the inlet of which is connected to the first side outlet. The inhibitor separation tower (13) is provided with a third top outlet and a third bottom outlet. The third bottom outlet is connected to the feed source through a second reflux branch pipe (131), and the third top outlet is connected to the catalytic distillation tower (12) through a third reflux branch pipe (132). The second side outlet is connected to the material supply source through the first return branch pipe (121).

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