Method and device for co-producing high-purity MTBE (methyl tert-butyl ether) and 1-butene by using isobutylene-poor mixed C4 as raw material

Abstract

The invention relates to the technical field of coal chemical industry, in particular to a method and a device for co-producing high-purity MTBE (Methyl Tert-Butyl Ether) and 1-butene by taking isobutene-poor mixed C4 as a raw material. The method mainly comprises the steps of etherification reaction, product separation and shunting, 1-butene refining and isomerization enrichment and circulation. Through heterogeneous enrichment and circulation, the effective concentration of isobutene entering the MTBE unit is remarkably improved, and the purity of the MTBE product is larger than or equal to 98%. Meanwhile, a 1-butene refining unit is optimized, and 1-butene with the purity being greater than or equal to 99.3% can be stably produced. According to the present invention, the low-value 2-butene is effectively utilized, the economic value of the raw material is improved, the etherification unit, the catalytic distillation unit, the separation unit, the isomerization unit and other units are integrated, the heat exchange network is optimized, and the energy consumption and the carbon emission are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal chemical industry, in particular to a method and device for co-production of high-purity MTBE and 1-butene by using poor isobutene mixed C4 as raw material. BACKGROUND

[0002] In the past decade, a large number of coal chemical plants have been put into operation. The yield of MTO by-product C4 accounts for about 13% of the total yield of olefins. The content of n-butene in MTO by-product C4 is as high as 85-90%, while the content of isobutene is generally 2-5%. At present, isobutene and 1-butene are widely used, and the application of 2-butene is less, and most of it is burned as liquefied gas, so how to improve the value of 2-butene has become a research hotspot in recent years.

[0003] 1-butene is an important raw material for coal chemical polyethylene plants, especially in recent years with the large-scale construction and production of polyolefin elastomer plants, the demand for 1-butene will further increase. 1-butene mainly comes from C4 separation. Isobutene and 1-butene are structural isomers, and the boiling point difference is 0.6℃, which is difficult to separate by distillation. High-purity 1-butene is generally obtained by etherification and then distillation. The by-product of the etherification reaction of the by-product C4 of coal chemical MTO is relatively high, and the purity of the product MTBE is 90-95%, which has low market recognition.

[0004] US patent application US5449851A, published on September 12, 1995, discloses a method for converting n-butene to isobutene by skeletal isomerization using ZSM-35 catalyst. The catalyst used is a mixed HZSM-35 / SiO2 catalyst containing 65% HZSM-35 and 35% SiO2, or a SiO2 supported HZSM-35 catalyst, which is prepared by mixing HZSM-35 with a SiO2 molar ratio of 20.3, or a catalyst prepared by introducing rare earth cations into the above HZSM-35 / SiO2. The conversion rate of n-butene is 10-35%, the selectivity of isobutene is 75-99%, and the yield of isobutene is 25-40% under the conditions of 325-500℃, N2 atmosphere and 156-177KPa total pressure. The method produces 0.1-0.7% of C5-C6+ heavy hydrocarbons as by-products, and the catalyst will be coked during the reaction process.

[0005] Chinese patent application CN105983435A, published on October 5, 2016, discloses a butene isomerization catalyst, its preparation method, and its application. It effectively improves the diffusion performance of ZSM-35 molecular sieve-based catalysts for the isomerization of n-butene to isobutene; meets the high acid center strength and density requirements of the butene isomerization reaction; suppresses byproducts generated by side reactions, such as propylene, pentene, and high-carbon-number olefins, and improves the catalyst's resistance to coking and deactivation; exhibits better product selectivity, conversion activity, and a longer active period in the isomerization reaction, extending the switching and regeneration cycle and facilitating long-term stable operation of the equipment; and simplifies the preparation process and reduces operating costs compared to traditional catalyst preparation methods.

[0006] Chinese patent application CN104557402A, published on April 29, 2015, discloses a method for producing isobutylene from n-butene via skeletal isomerization, comprising the following steps: a) loading an FER-type molecular sieve catalyst with a Si / Al molar ratio of 50-100 into a reactor and heating to 450-550°C under an inert gas atmosphere; b) introducing a mixed gas A consisting of at least one olefin with 4-5 carbon atoms and an inert gas; c) heating to 600-700°C, preferably 600-650°C, under an inert gas atmosphere; d) introducing a mixed gas B consisting of at least one olefin with 2-3 carbon atoms and an inert gas; e) adjusting to suitable isomerization reaction conditions under an inert gas atmosphere, introducing a n-butene-containing feedstock, and carrying out the isomerization reaction. This method has the advantages of high initial isobutylene yield and significantly shortened yield ramp-up period.

[0007] Chinese patent application CN103769204A, published on May 7, 2014, discloses a catalyst for the synthesis of isobutylene from a skeletal framework of n-butene. The catalyst consists of a modified all-potassium FER molecular sieve impregnated with boric acid and a binder. The weight content of the modified all-potassium FER molecular sieve in the final catalyst is 10-90%. A method for preparing the catalyst involves: modifying the all-potassium FER molecular sieve with boric acid, mixing it with a binder and water, molding the mixture, and then drying and calcining it to obtain the final catalyst. The n-butene skeletal isobutylene catalyst prepared by this method exhibits high initial isobutylene selectivity and yield.

[0008] None of the above involve the production of 1-butene, and the butene conversion rate is low. In order to improve the utilization rate of C4 2-butene, a by-product of MTO, improve the quality of MTBE products from coal chemical MTBE units, and produce high-value-added 1-butene, it is necessary to develop a new process technology to improve the utilization rate of C4 feedstock. Summary of the Invention

[0009] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for co-producing high-purity MTBE and 1-butene using a mixture of isobutylene and C4 as raw materials. This method isomerizes butene-2 ​​to isobutylene, improving the utilization rate of C4 in MTO, increasing the economic value of C4, and simultaneously improving the purity of MTBE. Furthermore, to address the poor stability of existing isomer catalysts, catalyst improvements have been made, increasing the isobutylene yield and extending catalyst life. The heat exchange network has been optimized, reducing steam consumption, energy consumption, and carbon emissions.

[0010] Another objective of this invention is to provide an apparatus for co-producing high-purity MTBE and 1-butene using a mixture of isobutylene and C4 as raw materials, which significantly improves the purity of MTBE and significantly reduces the MSBE content.

[0011] This invention is achieved using the following technical solution: The method for co-producing high-purity MTBE and 1-butene using isobutylene-poor mixed C4 as raw material includes the following steps: (1) Etherification reaction step: The isobutylene-poor mixed C4 feedstock is combined with the returned isobutylene-rich C4 stream, and then fed into the MTBE unit together with methanol for etherification reaction to generate a product containing MTBE and an etherified C4 rich in n-butene. (2) Product separation and diversion steps: Separate the MTBE product from the MTBE unit and divert the C4 after etherification into a first part of the material and a second part of the material; (3) 1-Butene refining step: The first part of the material is sent to the 1-butene refining unit for separation and purification to obtain 1-butene product; (4) Isomerization enrichment and recycling steps: The second part of the material is fed into the butene isomerization unit, so that the n-butene in it undergoes a skeletal isomerization reaction to generate isobutene, and a C4 stream rich in isobutene is obtained. The isobutene-rich C4 stream is then returned to step (1) and combined with fresh raw materials. The purpose is to increase the effective concentration of isobutene in the mixed raw materials entering the MTBE unit, thereby improving the purity of the final MTBE product.

[0012] Specifically, in the MTBE unit: fresh C4 and recycled isobutylene-rich C4 from outside the boundary, along with excess methanol, enter the etherification reactor. In the etherification reactor, isobutylene and methanol in the C4 react to produce MTBE. After the conversion rate reaches 95%, it enters the catalytic distillation column. In the catalytic distillation column, the downward-flowing liquid material undergoes heat and mass transfer and continues the etherification reaction under the action of a catalyst. The catalyst is a modular catalyst, which can simultaneously carry out the reaction and distillation. Most of the MTBE is removed from the bottom of the catalytic distillation column, and the unreacted C4 and methanol azeotrope rises to the top of the column in a vapor phase. Finally, it is collected from the top of the column and enters the C4 water washing column.

[0013] After etherification, C4 and water are contacted countercurrently in a C4 water washing tower. The water-washed C4 fraction at the top of the tower is divided into two streams: one goes to the 1-butene refining unit and the other goes to the butene isomerization unit.

[0014] The methanol-containing water material at the bottom of the tower enters the methanol recovery tower, where methanol and water are separated. The methanol recovered at the top of the tower is returned to the etherification reactor for recycling, while the water discharged from the bottom of the tower enters the C4 water washing tower for recycling.

[0015] 1-Butene Refining Unit: Some of the C4 ethers from the MTBE unit first enter the 1-butene refining feed heat exchanger to exchange heat with the isomerized product material from the coiled tube heat exchanger. After heat exchange, it enters the n-butane removal tower, where the C4 heavy components are removed. The material after the C4 heavy components are removed enters the isobutane removal tower. In the isobutane removal tower, the light components such as isobutane are collected from the top of the tower and exit the boundary area together with the C4 heavy components. The product 1-butene is collected from the bottom of the isobutane removal tower.

[0016] Butene isomerization unit: Part of the post-etherified C4 from the MTBE unit serves as the feedstock for the isomerization unit. This feedstock first enters a coiled tube heat exchanger to exchange heat with the material from the isomerization reactor, vaporizes, and heats up. Then, it enters an electric heater to be heated to the required temperature and directly enters the isomerization reactor. In the isomerization reactor, 1-butene and 2-butene are isomerized into isobutene. The isomerized product is cooled by heat exchange in the coiled tube heat exchanger and then enters a 1-butene refining feed heat exchanger for further cooling. It then enters a compressor buffer tank, where the C4 component is separated from other heavy components. The isomerized heavy components leave the boundary region, while the isomerized light components are mainly isobutene-rich C4. The isobutene-rich C4 enters the compressor, is compressed and pressurized, and then enters the etherification reactor for further reaction.

[0017] MTBE cell operating conditions: In the etherification reactor, the alcohol-to-olefin molar ratio of the fresh feed is controlled at 1.1-2, the reactor inlet temperature is 40-45℃, the outlet temperature is 55-75℃, and the operating pressure is 0.8-0.9 MPaG. The reacted material enters a catalytic distillation column, where the top temperature is controlled at 60-70℃, the bottom temperature at 125-140℃, the top pressure at 0.5-0.7 MPaG, the bottom pressure at 0.55-0.75 MPaG, and the reflux ratio is controlled between 0.5 and 3. The material from the top of the catalytic distillation column enters a C4 water washing column, which operates at approximately 40℃, with a top pressure of 0.6-0.9 MPaG and a bottom pressure of 0.8-1.1 MPaG. The methanol-containing aqueous solution then enters the methanol recovery tower, where the top temperature is 80-110℃, the bottom temperature is 105-140℃, the top pressure is 0.05-0.3MPaG, the bottom pressure is 0.1-0.4MPaG, and the reflux ratio is controlled at 3-20.

[0018] Operating conditions for the 1-butene refining unit: The C4 etherified material from the water washing tower first enters the 1-butene refining feed heat exchanger. The cold material (C4 etherified) has an inlet temperature of 35-45°C and is heated to 55-80°C before exiting. After heat exchange, the material enters the n-butane removal tower, where the top temperature is 50-65°C, the bottom temperature is 60-80°C, the top pressure is 0.5-0.8 MPaG, the bottom pressure is 0.6-0.9 MPaG, and the reflux ratio is 5-50. The material after the removal of heavy components enters the isobutane removal tower, where the top temperature is also 50-65°C, the bottom temperature is 60-80°C, the top pressure is 0.5-0.8 MPaG, the bottom pressure is 0.6-0.9 MPaG, and the reflux ratio ranges from 5-150.

[0019] Operating conditions for butene isomer units: Another portion of the C4 etherified material enters a coiled-tube heat exchanger. Its cold feed (isomer feed) inlet temperature is 35-45℃, and it is heated to 150-250℃ before flowing out. It then enters an electric heater, where it is further heated to the required reaction temperature of 350-410℃ before entering the isomerization reactor. The isomerization reaction is carried out at 350-410℃ and 0.1-0.3 MPaG. The reaction product is cooled by the coiled-tube heat exchanger (hot feed inlet temperature 350-410℃, outlet temperature 150-200℃) and then further cooled by the 1-butene refining feed heat exchanger (hot feed inlet temperature 150-200℃, outlet temperature 60-90℃). The cooled product enters a compressor buffer tank, which operates at a temperature of 60-90℃ and a pressure of 0.05-0.3 MPaG. The separated isobutylene-rich C4 then enters the compressor, where the inlet temperature is 40-60℃, the inlet pressure is 0.05-0.3MPaG, and the outlet pressure is increased to 0.8-1.0MPaG.

[0020] The aforementioned lean isobutylene mixed C4 feedstock is a by-product of the MTO unit, wherein the isobutylene content is 2-5 wt% and the n-butene content is 85-90 wt%.

[0021] The MTBE unit includes an etherification reactor and a catalytic distillation column connected in sequence; the methanol entrained in the post-etherification C4 is recovered through a water washing tower and a methanol recovery tower and recycled back to the etherification reactor for use.

[0022] Through the cycle of step (4), the concentration of isobutylene in the mixed raw materials entering the MTBE unit is increased to more than 15%, and the purity of the MTBE product reaches more than 98%.

[0023] The 1-butene refining unit includes a n-butane removal tower and an isobutane removal tower connected in sequence. The first part of the material first enters the n-butane removal tower to remove heavy components, and then enters the isobutane removal tower to remove light components. 1-Butene product is obtained from the bottom of the isobutane removal tower.

[0024] The butene isomerization unit includes a coiled tube heat exchanger, an electric heater, an isomerization reactor, and a compressor system connected in sequence; the high-temperature isomerization product discharged from the isomerization reactor exchanges heat with the second part of the material entering the butene isomerization unit and the first part of the material entering the 1-butene refining unit in sequence.

[0025] Before entering the compressor, the isomers undergo gas-liquid separation in the compressor buffer tank to remove the heavy components generated in the reaction.

[0026] The catalyst used in the butene isomer unit is a modified ZSM-35 molecular sieve catalyst.

[0027] The preparation method of the modified ZSM-35 molecular sieve catalyst includes the following steps: a) Preparation of template agent: Mix raw materials of Al2O3, SiO2, MgO, Na2O, K2O, R, and H2O in a molar ratio of 1:(5-35):(0.01-10):(1-50):(1-50):(1-50):(50-3000) and age them at a temperature of 50 to 120°C for 2 to 5 days to obtain template agent; wherein R is at least one of alkanolamine, alcohol, diol, triol, ethylenediamine, cyclohexylamine, pyridine, or pyrrolidine.

[0028] b) Preparation of mixed gel: Polyethylene glycol (PEG), silicon source, aluminum source, water, alkali source and template agent obtained in step a) are mixed to prepare a silica-alumina sol-template agent mixture; wherein, the weight ratio of PEG:silicon source:aluminum source:water:alkali source:template agent is (0.02-10):(0.05-10):(0.05-10):(1-100):(0.01-10):(0.05-10).

[0029] c) Hydrothermal crystallization: The silica-alumina sol-template mixture obtained in step b) is crystallized at 100 to 250°C for 3 to 12 days to obtain ZSM-35 molecular sieve raw powder.

[0030] d) Molding and activation: The ZSM-35 molecular sieve obtained in step c) is subjected to ammonium exchange and then calcined to obtain the desired isomerization catalyst.

[0031] The method for co-producing high-purity MTBE and 1-butene using lean isobutylene mixed C4 as raw material also includes a control step: the relative yield of MTBE and 1-butene is controlled by adjusting the flow ratio of the first part of the material and the second part of the material in step (2).

[0032] The apparatus corresponding to the method for co-producing high-purity MTBE and 1-butene using lean isobutylene mixed C4 as raw material includes an etherification reactor. The etherification reactor 1 is connected to a C4 water washing tower via a catalytic distillation column. The catalytic distillation column is connected to a coiled tube heat exchanger and a 1-butene refining feed heat exchanger via the C4 water washing tower. The coiled tube heat exchanger is connected to a heterogeneous reactor via an electric heater. The heterogeneous reactor is connected to the 1-butene refining feed heat exchanger via the coiled tube heat exchanger. The coiled tube heat exchanger is connected to a compressor buffer tank via the 1-butene refining feed heat exchanger. The compressor is connected to the 1-butene refining feed heat exchanger via the compressor buffer tank. The C4 water washing tower is connected to a n-butane removal tower via the 1-butene refining feed heat exchanger. The n-butane removal tower is connected to an isobutane removal tower via a pipeline. The C4 water washing tower is connected to a methanol recovery tower via a pipeline. A methanol feed pipeline is connected to the etherification reactor. The methanol recovery tower is connected to the methanol feed pipeline via a methanol recovery pipeline.

[0033] The bottom of the isobutane removal tower is connected to a 1-butene discharge pipe, the top of the isobutane removal tower is provided with a C4 component discharge pipe, and the n-butane removal tower is connected to the C4 component discharge pipe through a pipe.

[0034] The heterogeneous reactor is connected to a coiled tube heat exchanger via a pipe, and the coiled tube heat exchanger is connected to a 1-butene refining feed heat exchanger via a pipe.

[0035] The 1-butene refining feed heat exchanger is connected to the compressor via a compressor buffer tank, and the bottom of the compressor buffer tank is provided with a heterogeneous heavy component discharge pipe.

[0036] The etherification reactor is connected to a C4 feed pipe, and the compressor is connected to the C4 feed pipe through an isobutylene-rich C4 pipe.

[0037] The bottom of the catalytic distillation column is equipped with an MTBE discharge pipe.

[0038] Compared with the prior art, the beneficial effects of the present invention are: (1) By performing butene isomerization on some of the post-etherified C4, the resulting isobutylene-rich C4 is returned to the etherification unit, effectively increasing the isobutylene concentration in the raw material. This results in the MTBE product purity increasing from 90-95% in the traditional process to over 98%, greatly improving product quality and market competitiveness. At the same time, through the optimized 1-butene refining unit, high-purity 1-butene products with a purity of over 99.3% can be stably produced, meeting the needs of high-end chemical applications.

[0039] (2) This invention is particularly suitable for processing C4 esters with low isobutylene content and high n-butene content, such as C4 esters produced as a byproduct of MTO. Through the butene isomerization unit, 2-butene, which is traditionally difficult to utilize efficiently and is mostly burned as liquefied petroleum gas, is converted into high-value isobutylene, significantly improving the economic value of the raw materials and realizing the full and high-value-added utilization of C4 resources. By splitting the post-etherification C4 esters, one part enters the isomerization unit and the other part enters the 1-butene refining unit. By adjusting the opening of the regulating valves of each line and flexibly adjusting the splitting ratio according to the market demand for 1-butene, the output of MTBE and 1-butene can be flexibly adjusted within the same unit, enabling enterprises to respond quickly to market changes and maximize economic benefits.

[0040] (3) In the 1-butene refining unit, this invention adopts a sequence of first removing heavy components (removing n-butane) and then removing light components (removing isobutane), which reduces equipment investment and energy consumption. Through two-stage heat exchange using a coiled tube heat exchanger and a 1-butene refining feed heat exchanger, the heat of the isomer products is utilized in stages, effectively reducing the steam consumption of the 1-butene refining unit and the energy consumption of the entire system. In the isomerization unit, the heavy components are directly separated using a compressor buffer tank, eliminating the need for a separate heavy component removal tower, simplifying the process, and reducing equipment investment.

[0041] (4) The improved ZSM-35 molecular sieve catalyst used in this invention, through a specific preparation method, lowers the isomerization reaction temperature and effectively reduces catalyst coking during the reaction process, thereby extending the catalyst's service life and ensuring long-term stable operation of the equipment. This process organically integrates MTBE production, butene isomerization, and 1-butene refining. Methanol and water are recycled through a recovery system, reducing material consumption and waste emissions, which aligns with the green, energy-saving, and environmentally friendly development direction of modern chemical industry. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the apparatus of the present invention for co-producing high-purity MTBE and 1-butene using a mixture of isobutylene-poor C4 as raw materials; In the diagram: 1. Etherification reactor; 2. Catalytic distillation column; 3. C4 water washing column; 4. Methanol recovery column; 5. 1-Butene refining feed heat exchanger; 6. Butane removal column; 7. Isobutane removal column; 8. Tube heat exchanger; 9. Electric heater; 10. Isomerization reactor; 11. Compressor buffer tank; 12. Compressor; 13. C4 feed pipeline; 14. Methanol feed pipeline; 15. Methanol recovery pipeline; 16. Isobutene-rich C4 pipeline; 17. MTBE discharge pipeline; 18. 1-Butene discharge pipeline; 19. C4 component discharge pipeline; 20. Isomerized heavy component discharge pipeline. Detailed Implementation

[0043] To make the objectives and technical solutions of this invention clearer, the invention will be further described in detail below.

[0044] like Figure 1 As shown, the apparatus used in this embodiment is an apparatus for co-producing high-purity MTBE and 1-butene using lean isobutylene mixed C4 as feedstock. It includes an etherification reactor 1, which is connected to a C4 water washing tower 3 via a catalytic distillation column 2. The catalytic distillation column 2 is connected to a coiled-tube heat exchanger 8 and a 1-butene refining feed heat exchanger 5 via the C4 water washing tower 3. The coiled-tube heat exchanger 8 is connected to a heterogeneous reactor 10 via an electric heater 9. The heterogeneous reactor 10 is connected to the 1-butene refining feed heat exchanger 5 via the coiled-tube heat exchanger 8. The 1-butene refining feed heat exchanger 5 is connected to the compressor buffer tank 11. The compressor 12 is connected to the 1-butene refining feed heat exchanger 5 via the compressor buffer tank 11. The C4 water washing tower 3 is connected to the n-butane removal tower 6 via the 1-butene refining feed heat exchanger 5. The n-butane removal tower 6 is connected to the isobutane removal tower 7 via a pipeline. The C4 water washing tower 3 is connected to the methanol recovery tower 4 via a pipeline. The etherification reactor 1 is connected to the methanol feed pipeline 14. The methanol recovery tower 4 is connected to the methanol feed pipeline 14 via the methanol recovery pipeline 15. The bottom of the isobutane removal tower 7 is connected to the 1-butene discharge pipeline 18. The top of the isobutane removal tower 7 is equipped with a C4 component discharge pipeline 19. The n-butane removal tower 6 is connected to the C4 component discharge pipeline 19 via a pipeline. The isomerization reactor 10 is connected to the coiled tube heat exchanger 8 via a pipeline. The coiled tube heat exchanger 8 is connected to the 1-butene refining feed heat exchanger 5 via a pipeline. The 1-butene refining feed heat exchanger 5 is connected to the compressor 12 via a compressor buffer tank 11, and the bottom of the compressor buffer tank 11 is equipped with an isomer heavy component discharge pipe 20. The etherification reactor 1 is connected to a C4 feed pipe 13, and the compressor 12 is connected to the C4 feed pipe 13 via an isobutylene-rich C4 pipe 16. The bottom of the catalytic distillation column 2 is equipped with an MTBE discharge pipe 17.

[0045] Example 1 Fresh C4 and recycled isobutylene-rich C4 from outside the boundary area, along with excess methanol, enter the etherification reactor at a reaction pressure of 0.85 MPaG and a reaction temperature of 55°C. In the etherification reactor, isobutylene and methanol in the C4 react to produce MTBE. After a conversion rate of 95%, the MTBE enters a catalytic distillation column at an operating pressure of 0.55 MPaG and a reaction temperature of 60°C. In the catalytic distillation column, the downward-flowing liquid phase undergoes heat and mass transfer and continues the etherification reaction under the action of a catalyst. The catalyst is a modular catalyst, allowing for simultaneous reaction and distillation. Most of the MTBE is removed from the bottom of the catalytic distillation column, and the unreacted C4 and methanol azeotrope rises to the top of the column in a vapor phase. Finally, the MTBE is collected from the top and enters a C4 water washing column at an operating pressure of 0.6 MPaG and an operating temperature of 40°C.

[0046] After etherification, C4 and water are contacted countercurrently in a C4 water washing tower. The water-washed C4 fraction at the top of the tower is divided into two streams: one half goes to the 1-butene refining unit and the other half goes to the butene isomerization unit.

[0047] The methanol-containing water material at the bottom of the tower enters the methanol recovery tower, with an operating pressure of 0.1 MPaG and an operating temperature of 120°C, where methanol and water are separated. The methanol recovered at the top of the tower is returned to the etherification reactor for recycling, while the water discharged from the bottom of the tower enters the C4 water washing tower for recycling.

[0048] 1-Butene Refining Unit: Part of the C4 etherified material from the MTBE unit first enters the 1-butene refining feed heat exchanger to exchange heat with the isomerized product material from the coiled tube heat exchanger. After heat exchange, the temperature reaches 60°C and then enters the n-butane removal tower. The operating pressure is 0.6 MPaG and the operating temperature is 65°C. In the n-butane removal tower, the C4 heavy components are removed. The material after the C4 heavy components are removed enters the isobutane removal tower. The operating pressure is 0.5 MPaG and the operating temperature is 60°C. In the isobutane removal tower, the light components such as isobutane are collected from the top of the tower and exit the boundary area together with the C4 heavy components. The product 1-butene is collected from the bottom of the isobutane removal tower.

[0049] Using the heat exchange network of this invention, the 1-butene unit consumes 5.32 tons of low-pressure steam to produce 1 ton of 1-butene, and the energy consumption of the 1-butene unit is 377.89 standard oil / t butene-1, which effectively reduces carbon emissions.

[0050] Butene isomerization unit: Partially etherified C4 from the MTBE unit serves as the feedstock for the isomerization unit. This feedstock first enters a coiled tube heat exchanger to exchange heat with the material from the isomerization reactor, vaporizing and heating to 200°C. It then enters an electric heater to be heated to 400°C before directly entering the isomerization reactor. The reaction pressure is 0.2 MPaG, and the reaction temperature is 395°C. In the isomerization reactor, 1-butene and 2-butene are isomerized into isobutene. The isomerized product is cooled by heat exchange in the coiled tube heat exchanger and then enters a 1-butene refining feed heat exchanger for further cooling before entering a compressor buffer tank. The operating pressure is 0.15 MPaG, and the operating temperature is 70°C. In the compressor buffer tank, the C4 component is separated from other heavy components. The isomerized heavy components exit the boundary region, while the isomerized light components are mainly isobutene-rich C4. The isobutene-rich C4 enters the compressor at an outlet pressure of 1.0 MPaG and is then compressed and pressurized before entering the etherification reactor for further reaction.

[0051] The preparation method of the modified ZSM-35 molecular sieve catalyst includes the following steps: a) Preparation of template agent: The raw materials Al2O3, SiO2, MgO, Na2O, K2O, R, and H2O in a molar ratio of 1:15:2:10:10:10:800 are mixed and aged at 80°C for 3 days to obtain the template agent; wherein R is a mixture of ethanolamine, ethanol, ethylene glycol, glycerol, ethylenediamine, cyclohexylamine, pyridine, and pyrrolidine in a molar ratio of 1:1:1:1:1:1:1:1:1; b) Preparation of mixed gel: Polyethylene glycol (PEG), sodium silicate, sodium aluminate, water, sodium hydroxide and the template agent obtained in step a) are mixed to prepare a silica-alumina sol-template mixture; wherein the weight ratio of PEG:sodium silicate:sodium aluminate:water:sodium hydroxide:template agent is 0.4:1:0.25:20:0.02:0.5.

[0052] c) Hydrothermal crystallization: The silica-alumina sol-template mixture obtained in step b) is crystallized at 180°C for 8 days to obtain ZSM-35 molecular sieve raw powder.

[0053] d) Molding and activation: The ZSM-35 molecular sieve obtained in step c) is subjected to ammonium (ammonium nitrate) exchange and then calcined at 550℃ to obtain the desired isomerization catalyst.

[0054] By altering the distribution ratio of the isomeric catalyst group and implementing specific treatments, the regulation of acidic sites was modified, the reaction temperature was lowered, catalyst lifetime was extended, and the tendency for catalyst coking was reduced, resulting in a catalyst regeneration cycle of 45 days. Simultaneously, the conversion rate of 2-butene to isobutene was increased, while the conversion rate of 1-butene to isobutene was decreased, leading to greater selectivity for n-butene skeletal isomerization, allowing for more 2-butene isomerization while retaining the effective component, 1-butene. The 2-butene conversion rate was 44%, the isobutene selectivity was 95%, and the isobutene yield was 41.8%; the 1-butene conversion rate was 40%, the isobutene selectivity was 94%, and the isobutene yield was 37.6%; the average isobutene yield was approximately 40.4%.

[0055] The composition of fresh C4 in Example 1 is shown in Table 1. The composition of MTBE obtained in Example 1 is shown in Table 2. The composition of butene-1 obtained in Example 1 is shown in Table 3.

[0056] Example 2 The procedure was performed according to Example 1, except that the composition of the C4 feedstock was different. The composition of the fresh C4 feedstock is shown in Table 1. The isobutylene content in the C4 feedstock was 5 wt%, the trans-2-butene content was 35.1 wt%, and other parameters remained unchanged. The composition of the MTBE obtained in Example 2 is shown in Table 2. The composition of butene-1 obtained in Example 2 is shown in Table 3.

[0057] Example 3 The procedure was followed as in Example 1, using the same raw materials. When the market demand for 1-butene was strong and the profit margin for 1-butene was greater than that for MTBE, the flow rates of the two pipelines were adjusted via regulating valves. 70% of the flow was sent to the 1-butene refining unit, and 30% to the butene isomerization unit. The composition of the MTBE obtained in Example 3 is shown in Table 2. The composition of the butene-1 obtained in Example 3 is shown in Table 3.

[0058] While ensuring product quality, the company's efficiency has been improved.

[0059] Example 4 The procedure was followed as in Example 1, using the same raw materials. When MTBE market demand was strong and MTBE profits exceeded those of 1-butene, the flow rates of the two pipelines were adjusted via regulating valves. 30% of the MTBE was sent to the 1-butene refining unit, and 70% to the butene isomerization unit. The composition of the MTBE obtained in Example 4 is shown in Table 2. The composition of the butene-1 obtained in Example 4 is shown in Table 3. This improved enterprise efficiency while ensuring product quality.

[0060] Comparative Example 1 The raw material composition is the same as in Example 1. According to Chinese Patent CN101544532A, the etherification reactor operates at a pressure of 0.9 MPaG and a temperature of 65°C; the catalytic distillation column operates at a pressure of 0.55 MPaG and a temperature of 60°C; the C4 water washing column operates at a pressure of 0.6 MPaG and a temperature of 40°C; the methanol recovery column operates at a pressure of 0.1 MPaG and a temperature of 120°C; the n-butane removal column operates at a pressure of 0.6 MPaG and a temperature of 65°C; and the isobutane removal column operates at a pressure of 0.5 MPaG and a temperature of 60°C.

[0061] The 1-butene unit consumes 5.43 tons of low-pressure steam to produce 1 ton of 1-butene, and the energy consumption of the 1-butene unit is 385.6 standard oil / t butene-1.

[0062] The composition of fresh C4 in Comparative Example 1 is shown in Table 1, the composition of MTBE obtained in Comparative Example 1 is shown in Table 2, and the composition of butene-1 obtained in Comparative Example 1 is shown in Table 3.

[0063] MTBE has a purity of 92 wt%, which is less than 98 wt%. Due to its low purity, it cannot be sold as a chemical product and can only be used as a gasoline additive, which affects its downstream applications. In addition, 2-butene accounts for more than 60 wt% of the total C4 feedstock. This portion of C4 cannot be effectively utilized and can only be sold as liquefied petroleum gas, which reduces the company's profits.

[0064] Comparative Example 2 The raw material composition was the same as in Example 1, according to CN105983435A. In a 1L stirred tank at 100 rpm, 20 mL of sodium aluminate (industrial grade, Sichuan Leshan Runhe Catalytic New Materials Co., Ltd., Na2O 150 g / L, Al2O3 100 g / L) and 600 mL of water were added, followed by the slow addition of 110 g of silica gel (industrial grade, Qingdao Haiyang Chemical Co., Ltd.). The mixture was stirred for 1 hour, and then 30 mL of sodium hydroxide solution (industrial grade, Sichuan Leshan Runhe Catalytic New Materials Co., Ltd., Na2O 300 g / L) was slowly added to form a colloidal solution. 60 mL of pyridine (analytical grade, Beijing Chemical Reagent Co., Ltd.) was added as a template agent, and the mixture was stirred until homogeneous to obtain the reaction mixture. The reaction mixture was heated to 150°C and crystallized under autogenous pressure for 120 hours, after which the crystallization reaction was stopped. The solid product was separated by filtration; the obtained product, a white powder, was ZSM-35 molecular sieve.

[0065] Add 200 mL of water to the wet filter cake, and while stirring, simultaneously add sodium aluminate solution (as above) and aluminum sulfate solution (industrial grade, Sichuan Leshan Runhe Catalytic New Materials Co., Ltd., Al2O3 90 g / L). Control the dropping rates of the sodium aluminate solution and aluminum sulfate solution to make the pH of the material 9. Add 90 mL of sodium aluminate and 82 mL of aluminum sulfate. After filtration and washing with water, dry at 110 °C for 0.5 hours, extrude into four-leaf clover strips, and place them in a muffle furnace equipped with a vacuum pump to calcine and solidify under negative pressure at 300 °C for 0.5 hours. The negative pressure in the muffle furnace cavity is -0.05 MPa.

[0066] Ion exchange was performed using 1L of 5wt% ammonium nitrate solution at 90℃, repeated three times for 1 hour each time. After filtration, the catalyst was dried at 120℃ for 2 hours. The solution was diluted with 1mL of 1wt% chloroplatinic acid solution in 100mL of water and sprayed evenly onto the catalyst for adsorption and impregnation for 0.5 hours. After drying at 120℃ for 1 hour, the catalyst was placed in a muffle furnace equipped with a vacuum pump and activated under negative pressure at 580℃ for 2 hours. The negative pressure of the muffle furnace was -0.05MPa, thus obtaining the isomer catalyst.

[0067] The conversion rate of butene was 36.65%, the selectivity of isobutene was 93.3%, and the yield of isobutene was 34.2%.

[0068] The composition of fresh C4 in Comparative Example 2 is shown in Table 1, the composition of MTBE obtained in Comparative Example 2 is shown in Table 2, and the composition of butene-1 obtained in Comparative Example 2 is shown in Table 3.

[0069] Table 1: Composition of fresh C4 in Examples 1-4 and Comparative Examples 1-2

[0070] Table 2: Composition of MTBE in Examples 1-4 and Comparative Examples 1-2

[0071] Note: Product content minus C5.

[0072] Table 3: Composition of butene-1 in Examples 1-4 and Comparative Examples 1-2

[0073] As shown in Table 2, the purity of the MTBE product using the present invention is greater than 98 wt%, while the purity of the MTBE product using a non-present invention route is 92 wt%. The present invention completely solves the problem of low purity of MTBE product when using C4 raw materials with poor isobutylene. As shown in Table 3, the purity of the 1-butene product using the present invention is greater than 99.3 wt%, which meets the application requirements of the high-end chemical market.

Claims

1. A method for co-production of high purity MTBE and 1-butene from a poor isobutene mixed C4 as raw material, characterized in that, The method comprises the following steps: (1) etherification reaction step: combine the poor isobutene mixed C4 raw material with the returned isobutene-rich C4 stream, and then send them into the MTBE unit together with methanol for etherification reaction to generate a product containing MTBE and an etherized C4 rich in n-butene; (2) product separation and distribution step: separate the MTBE product from the MTBE unit, and distribute the etherized C4 into a first part and a second part; (3) 1-butene refining step: send the first part into the 1-butene refining unit to separate and purify to obtain the 1-butene product; (4) isomerization enrichment and circulation step: send the second part into the butene isomerization unit to make the n-butene therein undergo skeletal isomerization to generate isobutene, thereby obtaining the isobutene-rich C4 stream, and return the isobutene-rich C4 stream to step (1) to be combined with the fresh raw material, so as to increase the effective concentration of isobutene in the mixed raw material entering the MTBE unit, thereby improving the purity of the final MTBE product.

2. The method of claim 1, wherein, The poor isobutene mixed C4 raw material is the by-product C4 of the MTO device, wherein the isobutene content is 2-5 wt%, and the n-butene content is 85-90 wt%.

3. The method of claim 1, wherein, The MTBE unit comprises an etherification reactor (1) and a catalytic rectification tower (2) connected in sequence; the methanol entrained in the etherized C4 is recovered by a water washing tower and a methanol recovery tower, and is recycled to the etherification reactor (1) for use.

4. The method of claim 1, wherein, Through the circulation of step (4), the concentration of isobutene in the mixed raw material entering the MTBE unit is increased to more than 15%, and the purity of the MTBE product reaches more than 98%.

5. The method of claim 1, wherein, The 1-butene refining unit comprises a n-butane removal tower (6) and an i-butane removal tower (7) connected in sequence, the first part enters the n-butane removal tower (6) first to remove heavy components, and then enters the i-butane removal tower (7) to remove light components, and the 1-butene product is obtained from the bottom of the i-butane removal tower (7).

6. The method of claim 1, wherein, The butene isomerization unit comprises a coil heat exchanger (8), an electric heater (9), an isomerization reactor (10) and a compressor system connected in sequence; the high-temperature isomerization product discharged from the isomerization reactor (10) is sequentially heat-exchanged with the second part entering the butene isomerization unit and the first part entering the 1-butene refining unit.

7. The method of claim 6, wherein, The isomerization product is subjected to gas-liquid separation in the compressor buffer tank (11) before entering the compressor, so as to remove the heavy components generated in the reaction.

8. The method of claim 1, wherein, The catalyst used in the butene isomerization unit is a modified ZSM-35 molecular sieve catalyst.

9. The method of claim 1, wherein, The method further comprises a regulation step: by adjusting the flow ratio of the first part and the second part in step (2), the relative yield of MTBE and 1-butene is regulated.

10. A device for co-production of high-purity MTBE and 1-butene using the process of any one of claims 1-9 as a method for co-production of high-purity MTBE and 1-butene using a poor isobutene mixed C4 as raw material, characterized in that, It includes etherification reactor (1), etherification reactor (1) is connected with carbon four water washing tower (3) through catalytic rectifying tower (2), catalytic rectifying tower (2) is connected with coiled tube heat exchanger (8) and 1-butene refining feed heat exchanger (5) through carbon four water washing tower (3), coiled tube heat exchanger (8) is connected with isomerization reactor (10) through electric heater (9), isomerization reactor (10) is connected with 1-butene refining feed heat exchanger (5) through coiled tube heat exchanger (8), coiled tube heat exchanger (8) is connected with compressor buffer tank (11) through 1-butene refining feed heat exchanger (5), compressor (12) is connected with 1-butene refining feed heat exchanger (5) through compressor buffer tank (11), carbon four water washing tower (3) is connected with de-n-butane column (6) through 1-butene refining feed heat exchanger (5), de-n-butane column (6) is connected with de-isobutane column (7) through pipeline, carbon four water washing tower (3) is connected with methanol recovery column (4) through pipeline, etherification reactor (1) is connected with methanol feed pipeline (14), methanol recovery column (4) is connected with methanol feed pipeline (14) through methanol recovery pipeline (15).

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