Method for deep removal of isobutylene in mixed carbon four

Abstract

The present application belongs to the technical field of carbon four fraction separation, and particularly relates to a method for deeply removing isobutene in mixed carbon four. The method for deeply removing isobutene in mixed carbon four comprises the following steps: 1) an etherification unit; 2) a reaction rectification unit; and 3) a methanol recovery unit. The method deeply removes isobutene in the raw material mixed carbon four, so that the isobutene content in the carbon four after etherification is less than 100 ppm (wt), and the effective components butene-1, cis-butene-2 and trans-butene-2 in the subsequent reaction are not lost to a great extent, thereby meeting the requirement of the downstream oligomerization process on the isobutene content in the mixed butene feed being less than 300 ppm (wt).

Description

Technical Field

[0001] This invention belongs to the field of C4 fraction separation technology, specifically relating to a method for deep removal of isobutylene from mixed C4 fractions. Background Technology

[0002] Isononol (INA) is an important chemical raw material, mainly used in the production of diisononyl phthalate (DINP), a plasticizer for PVC. DINP is an excellent, general-purpose, non-toxic plasticizer, primarily used in polyvinyl chloride, vinyl chloride copolymers, cellulose acetate, ethyl cellulose, and synthetic rubber. DINP outperforms dioctyl phthalate (DOP), exhibiting superior heat resistance, light resistance, aging resistance, and electrical insulation. With increasing market demands for safety and environmental protection, DINP is gradually becoming an environmentally friendly alternative to DOP, leading to rapid demand growth and consequently, a surge in isononol consumption.

[0003] The main method route for the isononol unit is as follows: Figure 1 As shown, the feed requirements for the oligomerization unit are that the isobutylene content in the mixed butene (mainly butene-1, cis-butene-2, and trans-butene-2) is less than 300 ppm (wt), which requires that the isobutylene content in the post-etherified C4 is not greater than 100 ppm (wt).

[0004] The mixed C4 feedstock contains various butene isomers (mainly isobutylene, butene-1, cis-2-butene, and trans-2-butene), whose boiling points are very close. In particular, the boiling points of butene-1 (boiling point -6.26℃) and isobutylene (boiling point -6.9℃) differ by less than 1℃, making it impossible to remove isobutylene from the mixed C4 using conventional distillation methods. Currently, the commonly used method is to remove isobutylene through an etherification reaction with methanol, employing a fixed-bed etherification reaction followed by catalytic distillation. Traditional methods typically use a 10-layer reaction frame with randomly packed catalyst or a 10-layer bundled catalyst. Based on the current operating conditions of various production plants, the highest conversion rate of isobutylene in the mixed C4 feedstock is 99.5%, and the residual isobutylene content in the C4 after etherification is generally above 1000 ppm (wt), which does not meet the requirements for isononanol production. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides a method for deep removal of isobutylene from mixed C4, so that the isobutylene content in the C4 after etherification is less than 100 pmm (wt).

[0006] The method for deep removal of isobutylene from mixed C4 as described in this invention includes the following steps:

[0007] (1) Etherification unit

[0008] Methanol from the external tank area is mixed with mixed C4. After preheating, the mixture enters the reactor, where it reacts to achieve an isobutylene conversion rate of over 95%.

[0009] The operating parameters of the etherification unit are as follows: operating pressure 1.1~1.4 MPaG, operating temperature 40~60℃, alcohol-olefin molar ratio 1.02~1.05;

[0010] Etherification unit reaction mechanism:

[0011] Methanol is mixed with isobutylene from a C4 feedstock. In the first, second, and third stage reactors, under the catalysis of a large-pore, strongly acidic cation exchange resin, most of the isobutylene reacts with methanol to form methyl tert-butyl ether (MTBE). The reaction formula is as follows:

[0012] ;

[0013] This reaction is exothermic, with ΔH = -37 kJ / mol. It exhibits high selectivity, and side reactions can generate small amounts of isobutylene dimers (or oligomers) and dimethyl ether. Water introduced from the raw materials can generate small amounts of tert-butanol, etc. The reaction equation is as follows:

[0014] ,

[0015] ,

[0016] ;

[0017] The above-mentioned impurities have high octane numbers. A small amount remaining in the methyl tert-butyl ether product will not affect its performance. The remaining C4 components do not react with methanol and can be considered inert substances under the process conditions.

[0018] The reactor bed temperature is controlled by the feed preheating temperature and the reactor operating pressure.

[0019] (2) Reactive distillation unit

[0020] C4 from the reactor enters the feed / product heat exchanger to exchange heat with MTBE flowing from the bottom of the lower column of the reactive distillation column. After preheating, it enters the middle of the lower column of the reactive distillation column for distillation. The bottom of the column yields MTBE product with a purity of over 98.5%. The top C4 after distillation enters the bottom of the upper column of the reactive distillation column. The bottom MTBE product exchanges heat with the C4 feed and is then cooled by the MTBE product cooler before being sent out of the boundary area.

[0021] A stream of methanol undergoes partial impurity removal in a protective reactor, controlling the alkali content to be less than 0.1 ppm (wt). It then enters the first catalyst bed in the upper column of the reactive distillation column, where it reacts further with isobutylene from C4 rising from the bottom of the column to produce MTBE. The bottom liquid containing heavy components such as MTBE is pressurized by an intermediate pump and sent to the top of the lower column of the reactive distillation column. The C4 etherified from the top of the upper column of the reactive distillation column, containing less than 100 ppm (wt) of isobutylene, enters the condenser of the reaction column. The condensed C4 etherified is pressurized by a reflux pump, with part of it used as reflux in the reaction column and the other part sent to the methanol recovery unit.

[0022] The operating parameters are as follows:

[0023] Upper section of the reactive distillation column: operating pressure 0.4~0.47 MPaG, operating temperature 50~65℃.

[0024] Lower column of reactive distillation column: operating pressure 0.47~0.55MPaG, operating temperature 65~125℃;

[0025] Reaction mechanism:

[0026] Isobutylene in the mixed C4 feedstock reacts with methanol in a reactive distillation column under the action of an etherification catalyst to produce methyl tert-butyl ether. This reaction is reversible, and the equation is as follows:

[0027] C4H8+CH3OH→CH3-O-C4H9,

[0028] According to Raoult's Law, to make a reversible reaction proceed in the forward direction (to produce MTBE), one must either increase the concentration of the reactants on one side of the reaction or decrease the concentration of the products. In a reactive distillation column, the reaction and distillation processes occur simultaneously. As both processes proceed, MTBE is continuously generated and separated from the bottom of the column, ensuring that the generated MTBE is always at a low concentration. Therefore, the reaction always proceeds in the forward direction, i.e., towards the production of MTBE.

[0029] (3) Methanol recovery unit

[0030] The remaining C4 from the reactive distillation unit enters the C4 fraction cooler, and after cooling, it is sent to the bottom of the water washing tower, where it comes into countercurrent contact with the washing water from the top of the tower to wash away the methanol. The C4 fraction at the top of the tower, which contains less than 25 ppm (wt) of methanol, enters the C4 residual liquid collection tank to remove free water, and then is sent to the alkane-alkene separation unit.

[0031] The water containing methanol obtained at the bottom of the water washing tower is sent to the methanol recovery tower after exchanging heat with the bottom discharge of the methanol recovery tower. Methanol and water are separated. The gas phase at the top of the methanol recovery tower is condensed by the methanol condenser and enters the reflux tank. After being pressurized by the reflux pump, part of it is returned to the tower as reflux, and part is sent to the methanol feed tank. The water discharged from the bottom of the tower exchanges heat with the feed and is then cooled to 40°C before entering the water washing tower for recycling.

[0032] The operating parameters of the water washing tower are as follows: operating pressure 0.9~1.2MPaG, operating temperature 40℃;

[0033] The operating parameters of the methanol recovery tower are as follows: operating pressure 0.15 MPaG, operating temperature 87~125℃;

[0034] The first bed of the catalyst is filled with catalytic reaction modules.

[0035] Preferably, step (1) specifically includes the following steps:

[0036] Methanol and mixed C4 are mixed in the tank area outside the boundary zone. After preheating, the mixture enters the first-stage reactor. After the reaction in the first-stage reactor, part of the material is cooled by the first-stage cooler and then circulated back to the inlet of the first-stage reactor by the first-stage circulation pump to control the temperature of the first-stage reactor. The other part of the material enters the second-stage reactor to continue the reaction. After the reaction in the second-stage reactor, part of the material is cooled by the second-stage cooler and then circulated back to the inlet of the second-stage reactor by the second-stage circulation pump to control the temperature of the second-stage reactor. The other part of the material enters the third-stage reactor to continue the reaction and circulation, so that the conversion rate of isobutylene reaches more than 95%.

[0037] The parameters of the first-stage reactor are as follows: operating pressure 1.1~1.4MPaG, inlet temperature 46.2℃, outlet temperature 60℃, alcohol-olefin molar ratio 1.02~1.05;

[0038] The parameters for the two-stage reactor are as follows: operating pressure 1.3 MPaG, inlet temperature 52℃, outlet temperature 57.6℃, and alcohol-to-olefin molar ratio 1.02~1.05.

[0039] The parameters of the three-stage reactor are as follows: operating pressure 1.2 MPaG, inlet temperature 57.6℃, outlet temperature 59.6℃, and alcohol-olefin molar ratio 1.02~1.05.

[0040] Preferably, the first catalyst bed has a longitudinal dimension of 2800 mm and is divided into 10 sections along the longitudinal direction.

[0041] Preferably, the catalytic reaction module is CDM-140, manufactured by Dandong Mingzhu Special Resin Co., Ltd., and contains D005-II resin catalyst with a loading amount ≥200 kg / m³. 3Traditional resin etherification catalysts are packed between open-window flow-guiding packing materials, wrapped with wire mesh and sewn together to prevent the catalyst from being exposed, and then mixed with open-window flow-guiding packing materials with special structures. Because the packing materials have good radial diffusion capabilities, they can effectively improve the gas-liquid mass transfer capability in the catalytic reaction, efficiently separate the reaction products, and thus continuously promote the reaction in the forward direction.

[0042] Preferably, in step (1), before the methanol is mixed with the mixed C4, it is buffered by a methanol feed tank, pressurized by a methanol feed pump, and metered by a metering pump.

[0043] Preferably, in step (1), before mixing C4 and methanol, the mixture is buffered in a C4 feed tank, pressurized by a C4 feed pump, metered by a metering pump, and the isobutylene content is detected online.

[0044] This invention employs a three-stage fixed-bed etherification, reactive distillation, and methanol recovery process. Through the etherification reaction of isobutylene and methanol, as well as deep etherification, the isobutylene content in the post-etherified C4 is less than 100 ppm (wt). Furthermore, this invention incorporates the following more refined controls and improvements:

[0045] ① For the mixed C4 feed, a mass flow meter, regulating valve, and online analyzer (for analyzing the isobutylene content in the feed) are installed. For the methanol feed, a mass flow meter and regulating valve are installed. The quality of the methanol feed is strictly controlled, and the molar ratio of methanol to isobutylene in the mixed C4 is controlled between 1.02 and 1.05. Within this range, side reactions are minimized.

[0046] ② The reaction heat is promptly removed through external circulation in the first, second, and third stage etherification reactors, controlling the reaction temperature in the reactors to below 60℃ and avoiding numerous side reactions. Pipelines allow the three reactors to be connected in series or in parallel. The series / parallel connection sequence of the three reactors can be flexibly adjusted according to the activity of the catalyst in each reactor. Each reactor stage can be disconnected individually. The first and second stage reactors can be connected in series or in parallel. When connected in series, either reactor can be switched to the first reactor via pipelines. This allows for the simultaneous connection of two or three reactors in series, enabling online catalyst replacement and ensuring maximum utilization of the catalyst in each reactor. It also guarantees high catalyst activity and a conversion rate of no less than 95% for the etherification reaction.

[0047] ③ The reactive distillation column adopts a reaction-separation method. The lower section of the upper column of the reactive distillation column is equipped with a reaction section, which separates the reaction product MTBE while reacting. This continuously breaks the equilibrium of the reaction between isobutylene and methanol, and moves it in the forward reaction direction, ensuring that as much isobutylene as possible is removed.

[0048] The reaction section of the reactive distillation column uses 2800mm*10-segment catalytic reaction modules. These modules are CDM-140 series open-window guided flow catalytic distillation modules manufactured by Dandong Mingzhu Special Resin Co., Ltd. Each module contains D005-II resin catalyst, with a catalyst loading of ≥200kg / m³. 3 Traditional resin etherification catalysts are packed between open-window flow-guiding packing materials, wrapped with wire mesh and sewn together to prevent the catalyst from being exposed, and then mixed with open-window flow-guiding packing materials with special structures. This process has excellent dual functions of catalytic reaction and component separation, as well as good radial diffusion and gas-liquid mass transfer capabilities, which allows the reaction equilibrium to be broken better and continuously, maximizing the forward reaction direction.

[0049] ④ While the catalytic reaction module enables deep etherification of isobutylene, it also has drawbacks. Under traditional operating conditions—controlling the reactive distillation column top pressure at approximately 0.62 MPaG and temperature at around 60°C—numerous side reactions occur, specifically the reaction of butene-1 with methanol to produce MSBE. This is because the overall residence time of the material in the catalytic reaction module is longer than that of traditional reaction frame-packed or bundled catalysts, and the temperature gradient within the module is smaller, keeping the catalyst at a relatively high temperature. MSBE is a side reaction more likely to occur in high-temperature zones. Therefore, the reactive distillation column should be operated with pressure and temperature reduction to minimize side reactions and reduce butene-1 loss, ensuring that the isobutylene content in the C4 product after etherification is below 100 ppm (wt) and the purity of the MTBE product at the bottom is greater than 98.5 wt.%.

[0050] Compared with the prior art, the beneficial effects of the present invention are:

[0051] This invention can deeply remove isobutylene from the mixed C4 raw materials, so that the isobutylene content in the C4 after etherification is less than 100 ppm (wt), and with minimal loss of the effective components of subsequent reactions, butene-1, cis-butene-2, and trans-butene-2, it meets the requirement of the downstream oligomerization process that the isobutylene content in the mixed butene feed is less than 300 ppm (wt). Attached Figure Description

[0052] Figure 1 This is a flowchart of the isononol plant;

[0053] Figure 2 This is a schematic diagram of the etherification unit equipment of the present invention;

[0054] Figure 3 This is a schematic diagram of the reactive distillation unit equipment of the present invention;

[0055] Figure 4 This is a schematic diagram of the methanol recovery unit equipment of the present invention;

[0056] In the diagram, 1 is the first-stage reactor; 2 is the second-stage reactor; 3 is the third-stage reactor; 4 is the lower column of the reactive distillation column; 5 is the upper column of the reactive distillation column; 6 is the water washing column; and 7 is the methanol recovery column. Detailed Implementation

[0057] The technical solution of the present invention will now be clearly and completely described in conjunction with the accompanying drawings and embodiments. Example

[0058] The method for deep removal of isobutylene from mixed C4 as described in this invention specifically includes the following steps:

[0059] (1) Etherification unit

[0060] Methanol and mixed C4 are mixed in the tank area outside the boundary zone. After preheating, the mixture enters the first-stage reactor. After the reaction in the first-stage reactor, part of the material is cooled by the first-stage cooler and then circulated back to the inlet of the first-stage reactor by the first-stage circulation pump to control the temperature of the first-stage reactor. The other part of the material enters the second-stage reactor to continue the reaction. After the reaction in the second-stage reactor, part of the material is cooled by the second-stage cooler and then circulated back to the inlet of the second-stage reactor by the second-stage circulation pump to control the temperature of the second-stage reactor. The other part of the material enters the third-stage reactor to continue the reaction and circulation, so that the conversion rate of isobutylene reaches more than 95%.

[0061] The parameters of the first-stage reactor are as follows: operating pressure 1.1~1.4MPaG, inlet temperature 46.2℃, outlet temperature 60℃, alcohol-olefin molar ratio 1.02~1.05;

[0062] The parameters for the two-stage reactor are as follows: operating pressure 1.3 MPaG, inlet temperature 52℃, outlet temperature 57.6℃, and alcohol-to-olefin molar ratio 1.02~1.05.

[0063] The parameters of the three-stage reactor are as follows: operating pressure 1.2 MPaG, inlet temperature 57.6℃, outlet temperature 59.6℃, alcohol-olefin molar ratio 1.02~1.05;

[0064] (2) Reactive distillation unit

[0065] C4 from the three-stage reactor 3 enters the feed / product heat exchanger and exchanges heat with MTBE flowing out from the bottom of the lower column 4 of the reactive distillation column. After preheating, it enters the middle of the lower column 4 of the reactive distillation column for distillation. 98.7% MTBE product is obtained in the bottom of the column. The C4 from the top of the column after distillation enters the bottom of the upper column 5 of the reactive distillation column. The MTBE product in the bottom of the column exchanges heat with the C4 feed and is then cooled by the MTBE product cooler before being sent out of the boundary area.

[0066] A stream of methanol undergoes partial impurity removal in a protective reactor, controlling the alkali content to be less than 0.1 ppm (wt). It then enters the first catalyst bed of the upper column 5 of the reactive distillation column, where it reacts further with isobutylene from C4 rising from the bottom of the column to produce MTBE. The bottom liquid containing heavy components such as MTBE is pressurized by an intermediate pump and sent to the top of the lower column 4 of the reactive distillation column. The C4 etherified from the top of the upper column 5 of the reactive distillation column, containing less than 100 ppm (wt) of isobutylene, enters the condenser of the reaction column. The condensed C4 etherified is pressurized by a reflux pump, with part of it used as reflux in the reaction column and the other part sent to the methanol recovery unit.

[0067] The operating parameters are as follows:

[0068] Upper column 5 of the reactive distillation column: operating pressure 0.4~0.47 MPaG, operating temperature 50~65℃.

[0069] Lower column 4 of the reactive distillation column: operating pressure 0.47~0.55MPaG, operating temperature 65~125℃;

[0070] (3) Methanol recovery unit

[0071] The remaining C4 from the reactive distillation unit enters the C4 fraction cooler, and after cooling, it is sent to the bottom of the water washing tower 6, where it comes into countercurrent contact with the washing water from the top of the tower to wash away the methanol. The C4 fraction at the top of the tower, which contains less than 25 ppm (wt) of methanol, enters the C4 residual liquid collection tank to remove free water, and then is sent to the alkane-alkene separation unit.

[0072] The water containing methanol obtained at the bottom of the water washing tower 6 is sent to the methanol recovery tower 7 after exchanging heat with the bottom discharge of the methanol recovery tower 7. The methanol and water are separated. The gas phase at the top of the methanol recovery tower 7 is condensed by the methanol condenser and enters the reflux tank. After being pressurized by the reflux pump, part of it is returned to the tower as reflux, and part of it is sent to the methanol feed tank. The water discharged from the bottom of the tower exchanges heat with the feed and is then cooled to 40°C before entering the water washing tower 6 for recycling.

[0073] The operating parameters of water washing tower 6 are as follows: operating pressure 0.9~1.2MPaG, operating temperature 40℃;

[0074] The operating parameters of methanol recovery tower 7 are as follows: operating pressure 0.15 MPaG, operating temperature 87~125℃;

[0075] The first bed of the catalyst is filled with catalytic reaction modules.

[0076] The first catalyst bed has a longitudinal dimension of 2800 mm and is divided into 10 sections along the longitudinal direction.

[0077] The catalytic reaction module is CDM-140, manufactured by Dandong Mingzhu Special Resins Co., Ltd.

[0078] Comparative Example

[0079] The difference between this comparative example and the embodiment is that, in step (2), the catalyst in the first bed of the reactive distillation unit is a bundled catalyst, the bundle is filled with D005-II resin catalyst, produced by Dandong Mingzhu Special Resin Co., Ltd., the bundle is φ320mm, the height is 500mm, the longitudinal dimension of the first bed of the catalyst is 2800mm, and 10 layers are set in the longitudinal direction.

[0080] In step (2), the operating parameters are as follows: upper column of the reactive distillation column: operating pressure 0.62~0.67MPaG, operating temperature 53.8~57.7℃; lower column of the reactive distillation column: operating pressure 0.67~0.72MPaG, operating temperature 57.7~136.1℃.

[0081] Apart from the above, all other steps are the same as in the embodiments.

[0082] Results Comparison

[0083] The composition of the raw material mixture C4 in the examples and comparative examples is shown in Table 1 below.

[0084] Table 1. Raw material mixture C4 components

[0085]

[0086] The C4 composition of the ether discharged from the top of the reactive distillation column in the examples and comparative examples is shown in Tables 2 and 3 below.

[0087] Table 2. Etherified C4 Components of Examples

[0088]

[0089] Table 3 Comparative Ether-Based Carbon Four Components Table

[0090]

[0091] As can be seen from Tables 1-3, the isobutylene content in C4 after ether discharge from the top of the reactive distillation column of the present invention is below 100 ppm (wt), while the isobutylene content in C4 after ether discharge from the top of the reactive distillation column using a bundled catalyst is much higher than 100 ppm (wt).

Claims

1. A method for deep removal of isobutylene from mixed C4 compounds, characterized in that, Includes the following steps: (1) Etherification unit Methanol from the external tank area is mixed with mixed C4, and the molar ratio of isobutylene in methanol and mixed C4 is controlled between 1.02 and 1.

05. After the mixed raw material is preheated, it enters the reactor. After the reaction is carried out in the reactor, the isobutylene conversion rate reaches more than 95%. The operating parameters for the etherification unit are as follows: Operating pressure: 1.1~1.4 MPaG Operating temperature 40~60℃ The molar ratio of alcohol to olefin is 1.02~1.05; (2) Reactive distillation unit C4 from the reactor enters the feed / product heat exchanger to exchange heat with MTBE flowing from the bottom of the lower column of the reactive distillation column. After preheating, it enters the middle of the lower column of the reactive distillation column for distillation. The bottom of the column yields MTBE product with a purity of over 98.5%. The top C4 after distillation enters the bottom of the upper column of the reactive distillation column. The bottom MTBE product exchanges heat with the C4 feed and is then cooled by the MTBE product cooler before being sent out of the boundary area. A stream of methanol undergoes partial impurity removal in a protective reactor, controlling the alkali content to be less than 0.1 ppm (wt). It then enters the first catalyst bed in the upper column of the reactive distillation column, where it reacts further with isobutylene from C4 rising from the bottom of the column to produce MTBE. The bottom liquid containing heavy components such as MTBE is pressurized by an intermediate pump and sent to the top of the lower column of the reactive distillation column. The C4 etherified from the top of the upper column of the reactive distillation column, containing less than 100 ppm (wt) of isobutylene, enters the condenser of the reaction column. The condensed C4 etherified is pressurized by a reflux pump, with part of it used as reflux in the reaction column and the other part sent to the methanol recovery unit. The operating parameters are as follows: Upper section of the reactive distillation column: operating pressure 0.4~0.47 MPaG, operating temperature 50~65℃. Lower column of reactive distillation column: operating pressure 0.47~0.55MPaG, operating temperature 65~125℃; (3) Methanol recovery unit The remaining C4 from the reactive distillation unit enters the C4 fraction cooler, and after cooling, it is sent to the bottom of the water washing tower, where it comes into countercurrent contact with the washing water from the top of the tower to wash away the methanol. The C4 fraction at the top of the tower, which contains less than 25 ppm (wt) of methanol, enters the C4 residual liquid collection tank to remove free water, and then is sent to the alkane-alkene separation unit. The water containing methanol obtained at the bottom of the water washing tower is sent to the methanol recovery tower after exchanging heat with the bottom discharge of the methanol recovery tower. Methanol and water are separated. The gas phase at the top of the methanol recovery tower is condensed by the methanol condenser and enters the reflux tank. After being pressurized by the reflux pump, part of it is returned to the tower as reflux, and part is sent to the methanol feed tank. The water discharged from the bottom of the tower exchanges heat with the feed and is then cooled to 40°C before entering the water washing tower for recycling. The operating parameters of the water washing tower are as follows: operating pressure 0.9~1.2MPaG, operating temperature 40℃; The operating parameters of the methanol recovery tower are as follows: operating pressure 0.15 MPaG, operating temperature 87~125℃; The first bed of the catalyst is filled with a catalytic reaction module; Step (1) specifically includes the following steps: Methanol and mixed C4 are mixed in the tank area outside the boundary zone. After preheating, the mixture enters the first-stage reactor. After the reaction in the first-stage reactor, part of the material is cooled by the first-stage cooler and then circulated back to the inlet of the first-stage reactor by the first-stage circulation pump to control the temperature of the first-stage reactor. The other part of the material enters the second-stage reactor to continue the reaction. After the reaction in the second-stage reactor, part of the material is cooled by the second-stage cooler and then circulated back to the inlet of the second-stage reactor by the second-stage circulation pump to control the temperature of the second-stage reactor. The other part of the material enters the third-stage reactor to continue the reaction and circulation, so that the conversion rate of isobutylene reaches more than 95%. The parameters of the first-stage reactor are as follows: operating pressure 1.1~1.4MPaG, inlet temperature 46.2℃, outlet temperature 60℃, alcohol-olefin molar ratio 1.02~1.05; The parameters for the two-stage reactor are as follows: operating pressure 1.3 MPaG, inlet temperature 52℃, outlet temperature 57.6℃, and alcohol-to-olefin molar ratio 1.02~1.

05. The parameters of the three-stage reactor are as follows: operating pressure 1.2 MPaG, inlet temperature 57.6℃, outlet temperature 59.6℃, alcohol-olefin molar ratio 1.02~1.05; The catalytic reaction module is CDM-140.

2. The method for deep removal of isobutylene from mixed C4 as described in claim 1, characterized in that, The first catalyst bed has a longitudinal dimension of 2800 mm and is divided into 10 sections along the longitudinal direction.

3. The method for deep removal of isobutylene from mixed C4 as described in claim 1, characterized in that, In step (1), before the methanol and mixed C4 are mixed, the methanol is buffered by the methanol feed tank, pressurized by the methanol feed pump, and metered by the metering pump.

4. The method for deep removal of isobutylene from mixed C4 as described in claim 1, characterized in that, In step (1), before mixing C4 and methanol, the mixture is buffered in a C4 feed tank, pressurized by a C4 feed pump, metered by a metering pump, and the isobutylene content is detected online.

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