A process for the conversion of mixed c4's

Abstract

The application provides a mixed carbon four conversion method, comprising the following steps: step 1, full hydrogenation treatment is carried out on the mixed carbon four so that olefins in the mixed carbon four are converted into alkanes; step 2, the mixture after step 1 treatment is separated to obtain a normal butane component and an isobutane component respectively; and step 3, the normal butane component obtained in step 2 is subjected to oxidation treatment to obtain maleic anhydride. The method can realize closed loop conversion of the mixed carbon four to chemical materials, each component can be fully utilized, and almost no waste is produced. Meanwhile, the process conditions in the method are mild, easy to control, the flow is short, and the process is simple.

Description

Technical Field

[0001] This invention relates to the field of mixed C4 comprehensive utilization technology, and specifically to a method for converting mixed C4. Background Technology

[0002] Mixed C4 refers to liquefied petroleum gas (LPG) with a content of over 95% of butane (n-butane, isobutane), butene (1,3-butadiene, 1-butene, 2-butene (cis-2-butene, trans-2-butene), isobutene, etc.), mainly originating from catalytic cracking units in oil refineries, ethylene steam cracking units, and byproducts of methanol-to-olefins (MTO) processes.

[0003] In recent years, with the rapid increase in crude oil processing capacity and ethylene production, my country's petrochemical industry has seen a continuous expansion of mixed C4 resources. However, the comprehensive utilization of mixed C4 resources in my country started late, and the level of chemical utilization of mixed C4 is relatively backward. Even though there has been some progress in the comprehensive utilization of mixed C4 in recent years, overall, the utilization rate of mixed C4 resources in my country is still relatively low, especially in the initial stage of chemical utilization. Butadiene, n-butene, isobutene, n-butane, and isobutane in mixed C4 from refineries and ethylene cracking are all important organic chemical raw materials. Currently, the utilization of C4 resources in my country is mainly concentrated in olefins. Moreover, because the surplus C4 from various refining and chemical enterprises cannot be integrated and can only be processed separately, the scale of C4 utilization units in my country is relatively small, and the technological development capability is poor. Olefin resources alone cannot be fully utilized; for example, a considerable portion of n-butene and isobutene is still burned as fuel. Some refining and chemical enterprises, due to the low utilization rate of C4 resources, cannot fully consume the butadiene products separated from cracked C4 locally, and the surplus products need to be sold externally. Due to the high transportation costs, this results in a loss of economic benefits.

[0004] Currently, mixed C4 primarily originates from refinery catalytic cracking units and ethylene steam cracking units. Typical processing and utilization pathways include:

[0005] (1) The mixed C4 produced by the catalytic cracking unit is mostly used to produce methyl tert-butyl ether (MTBE) by etherifying isobutylene. MTBE is generally used as a blending component for high-octane gasoline. A few companies use a portion of C4 to produce methyl ethyl ketone (MEK).

[0006] (2) The mixed C4 produced by the cracking unit is mainly used to produce chemical products such as butadiene, MTBE, and 1-butene. Among them, the mixed C4 is first separated into butadiene by deep solvent extraction, which is mainly used for ABS resin and synthetic rubber. The mixed C4 after butadiene extraction is used to produce MTBE.

[0007] CN107722177A discloses a method for utilizing mixed C4 hydrocarbons: (1) under nitrogen, in the presence of an initiator and an organic solvent, copolymerizing part or all of the terminal olefins in the material containing mixed C4 hydrocarbons with maleic anhydride; (2) separating the product obtained in step (1) into a gas phase product and a liquid-solid mixture; based on the total weight of the gas phase product, the content of terminal olefins in the gas phase product is less than 1% by weight, and the content of 1,3-butadiene is less than 0.1% by weight; (3) subjecting the gas phase product obtained in step (2) to a steam cracking reaction, and returning the cracked gas to the material in step (1); (4) separating the liquid-solid mixture obtained in step (2) into a solid product containing a polymer with maleic anhydride functional groups; the mixed C4 hydrocarbons are a mixture containing C4 hydrocarbon compounds. The mixed C4 hydrocarbons can be converted into functional material raw materials for utilization. In this invention, the reaction of C4 terminal olefins with maleic anhydride produces a mixture that is difficult to separate and has a low yield. Therefore, the utilization rate of the mixed C4 in this invention is low, and the properties of the resulting polymer are difficult to control.

[0008] Therefore, further research is needed in this field on conversion methods for mixed C4. Summary of the Invention

[0009] The main objective of this invention is to provide a method for converting mixed C4 to overcome the low utilization rate of mixed C4 in the prior art.

[0010] To achieve the above objectives, the present invention provides a method for the conversion of mixed C4, comprising the following steps:

[0011] Step 1: The mixed C4 is subjected to full hydrogenation treatment to convert the olefins in the mixed C4 into alkanes;

[0012] Step 2: Separate the mixture after Step 1 to obtain n-butane component and isobutane component respectively;

[0013] Step 3: Oxidize the n-butane component obtained in Step 2 to obtain maleic anhydride.

[0014] In one embodiment, the mixed C4 conversion method of the present invention further includes step 4, reacting the maleic anhydride with isobutylene to obtain an isobutylene-maleic anhydride polymer.

[0015] The method for converting mixed C4 according to the present invention, wherein the isobutylene is prepared by the dehydrogenation reaction of the isobutane component.

[0016] The method for converting mixed C4 according to the present invention further includes performing an ortho-configuration reaction on the isobutane component, and then mixing the reaction product with the n-butane component for oxidation treatment to obtain maleic anhydride.

[0017] The method for converting mixed C4 according to the present invention, wherein the mixture after step 1 is separated by distillation, wherein the isobutane component is collected from the top of the distillation column and the n-butane component is collected from the bottom of the distillation column.

[0018] The present invention discloses a method for converting mixed C4, wherein the mixed C4 originates from a catalytic cracking unit, a coking unit, an ethylene steam cracking unit, a methanol-to-olefins unit, or an MTBE production unit; the mixed C4 contains at least one of 1-butene, isobutene, 1,3-butadiene, n-butane, isobutane, cis-2-butene, and trans-2-butene.

[0019] The method for converting mixed C4 according to the present invention, wherein the molar ratio of isobutylene to maleic anhydride is 2:1-1:1, the reaction temperature of maleic anhydride and isobutylene is 50-70℃, and the reaction time is 2-4h.

[0020] The method for converting mixed C4 according to the present invention, wherein the reaction between maleic anhydride and isobutylene is carried out under the action of an initiator, wherein the initiator is an organic peroxide or an azo compound, and the amount of the initiator is 0.5-3 wt% of the theoretical amount of isobutylene-maleic anhydride polymer generated.

[0021] To achieve the above objectives, the present invention also provides a method for the conversion of mixed C4, comprising the following steps:

[0022] Step 1: The mixed C4 is subjected to full hydrogenation treatment to convert the olefins in the mixed C4 into alkanes;

[0023] Step 2: Separate the mixture after Step 1 to obtain n-butane component and isobutane component respectively;

[0024] Step 3: The isobutane component is subjected to a dehydrogenation reaction to obtain isobutene.

[0025] In one embodiment, the mixed C4 conversion method of the present invention further includes step 4, reacting the isobutylene with maleic anhydride to obtain an isobutylene-maleic anhydride polymer.

[0026] The method for converting mixed C4 according to the present invention further includes isomerizing the n-butane component, and then mixing the reaction product with the isobutane component to carry out a dehydrogenation reaction to obtain isobutene.

[0027] The beneficial effects of this invention are:

[0028] This invention can convert mixed C4 atoms into chemical raw materials such as n-butane, isobutane, maleic anhydride, and isobutylene, and the production amount of each substance can be selected as needed, exhibiting flexibility and adjustability. Furthermore, this invention can also convert mixed C4 atoms into isobutylene and maleic anhydride, which can then be used to prepare copolymers via polar polymerization. Therefore, the method of this invention can achieve closed-loop conversion of mixed C4 atoms into chemical materials, fully utilizing each component with almost no waste generation. Simultaneously, the process conditions are mild, easily controlled, and the process is short and simple. Attached Figure Description

[0029] Figure 1 This is a flowchart of the mixed C4 conversion process in one embodiment of the present invention. Detailed Implementation

[0030] The technical solution of the present invention will be described in detail below. The following embodiments are implemented under the premise of the technical solution of the present invention and a detailed implementation process is given. However, the protection scope of the present invention is not limited to the following embodiments. Structures or experimental methods that do not specify specific conditions in the following embodiments are generally performed under conventional conditions.

[0031] This invention provides a method for the conversion of mixed C4 atoms, such as... Figure 1 As shown. The mixed C4 can originate from a catalytic cracking unit, a coking unit, an ethylene steam cracking unit, a methanol-to-olefins unit, or an MTBE production unit. In one embodiment, the catalytic cracking unit, coking unit, ethylene steam cracking unit, and methanol-to-olefins unit produce mixed C4 as a byproduct, while the MTBE production unit produces post-etherified C4 as a byproduct. Post-etherified C4 refers to the C4 component remaining after the isobutylene is etherified.

[0032] The present invention provides a mixed C4 conversion method that allows for adjustment of the conversion products as needed, making the process flexible, highly adaptable, and of high industrial application value.

[0033] In a first embodiment, the method for converting mixed C4 atoms according to the present invention includes the following steps:

[0034] Step 1: The mixed C4 is subjected to full hydrogenation treatment to convert the olefins in the mixed C4 into alkanes;

[0035] Step 2: Separate the mixture after Step 1 to obtain n-butane component and isobutane component respectively;

[0036] Step 3: Oxidize the n-butane component obtained in Step 2 to obtain maleic anhydride.

[0037] Thus, the mixed C4 of the present invention can be converted into maleic anhydride and isobutane.

[0038] In one embodiment, the mixed C4 contains at least one of 1-butene, isobutene, 1,3-butadiene, n-butane, isobutane, cis-2-butene, and trans-2-butene. The present invention does not particularly limit the content of each substance in the mixed C4, and the mixed C4 produced as a by-product in the prior art can be used as the raw material of the present invention.

[0039] In step 1, the mixed C4 hydrocarbons undergo full hydrogenation, meaning the olefins in the mixed C4 hydrocarbons are hydrogenated. Specifically, all the olefins in the mixed C4 hydrocarbons are converted into alkanes through hydrogenation. Thus, the mixture after step 1 is primarily composed of alkanes, mainly n-butane and isobutane.

[0040] This invention does not specifically limit the hydrogenation process conditions. In one embodiment, the full hydrogenation process conditions are as follows: using the LY-2005 nickel-based hydrogenation catalyst from the Petrochemical Research Institute of China National Petroleum Corporation, inlet temperature 30-180℃, reaction pressure ≥1.5MPa, hydrogen-to-oil volume ratio 300-600:1, dilution ratio 2-10, and fresh space velocity 0.5-2.5h. -1 .

[0041] Step 2 involves separating the mixture after step 1 to obtain n-butane and isobutane components, respectively.

[0042] In one embodiment, the mixture after step 1 is separated by distillation, for example, in a distillation column. The isobutane component is collected from the top of the column, and the n-butane component is collected from the bottom. This invention utilizes the difference in boiling points between n-butane and isobutane to separate the alkane mixture obtained in step 1 using distillation. The isobutane component obtained from the top of the column mainly consists of isobutane and may contain small amounts of gaseous impurities; the n-butane component obtained from the bottom of the column mainly consists of n-butane and may contain small amounts of heavy components. The n-butane and isobutane components obtained by this invention can be used separately as chemical raw materials.

[0043] This invention does not specifically limit the structure of the distillation column; a conventional distillation column in the art is sufficient. In one embodiment, during distillation, the top temperature is 40-60°C, for example 50°C, and the operating pressure is 0.5-0.7 MPa, for example 0.6 MPa; the bottom temperature is 55-75°C, for example 65°C, and the operating pressure is 0.60-0.70 MPa, for example 0.65 MPa.

[0044] Step 3 involves oxidizing the n-butane component obtained in step 2 to obtain maleic anhydride.

[0045] In this invention, the method for oxidizing the n-butane component can be a fixed-bed oxidation method, a fluidized-bed oxidation method, or a circulating fluidized-bed oxidation method, in which n-butane is oxidized to maleic anhydride under the action of a catalyst. In one embodiment, a VPO catalyst (vanadium phosphorus oxygen catalyst) is used, with a reaction temperature of 350-400℃ and a space velocity of 1000-2000 h⁻¹. -1 Oxidation can be carried out under reaction pressure of 0.10-0.15 MPa, but the present invention is not limited to this, and any existing technology that can oxidize n-butane to maleic anhydride is acceptable.

[0046] The maleic anhydride (maleic anhydride) obtained by the method of this invention can be used alone as a chemical raw material.

[0047] In one embodiment, the method for converting mixed C4 atoms according to the present invention further includes step 4, reacting maleic anhydride with isobutylene to obtain an isobutylene-maleic anhydride polymer. Thus, the present invention can convert mixed C4 atoms into an isobutylene-maleic anhydride polymer. The isobutylene-maleic anhydride polymer obtained by the method of the present invention is a pure polymer with a product yield of approximately 90%.

[0048] In one embodiment, isobutylene and maleic anhydride of the present invention are copolymerized at a molar ratio of 1:1 to obtain an alternating copolymer of isobutylene and maleic anhydride. In another embodiment, to ensure complete reaction of the maleic anhydride, the molar ratio of isobutylene to maleic anhydride is 2:1 to 1:1.

[0049] The polymerization reaction of isobutylene and maleic anhydride in this invention is carried out in a solvent environment under the action of an initiator. This invention does not particularly limit the types of initiators and solvents; conventional initiators and solvents used in polymerization reactions in the art are acceptable. In one embodiment, the initiator of this invention is an organic peroxide or an azo compound, and the mass of the initiator in the reaction system is 0.5-3% of the theoretical mass of the isobutylene-maleic anhydride polymer produced.

[0050] In one embodiment, the solvent for the polymerization reaction of the present invention is an organic ester, such as at least one selected from ethyl formate, methyl acetate, ethyl acetate, methyl propionate, isopropyl acetate, methyl isobutyrate, ethyl propionate, propyl acetate, methyl butyrate, butyl formate, methyl isobutyrate, butyl acetate, ethyl n-butyrate, isoamyl formate, isoamyl acetate, isoamyl butyrate, ethyl butyrate, butyl butyrate, isobutyl butyrate, isoamyl butyrate, methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, methyl carbonate, dimethyl carbonate, and diethyl carbonate. The amount of solvent used is, for example, such that the theoretical product, the isobutylene-maleic anhydride polymer, accounts for 10%-20% of the mass of the reaction system.

[0051] In one embodiment, the polymerization reaction in step 4 of the present invention is carried out at a temperature of 50-70°C for 2-4 hours.

[0052] This invention does not specifically limit the source of isobutylene, and it can be a commercially available product. However, preferably, the isobutylene is prepared by dehydrogenation of the isobutane component obtained in this invention. Thus, the mixed C4 atoms are hydrogenated and separated, the resulting n-butane is oxidized to maleic anhydride, the resulting isobutane is dehydrogenated to obtain isobutylene, and the maleic anhydride and isobutylene are polymerized to obtain an isobutylene-maleic anhydride polymer. The mixed C4 conversion method of this invention enables the full and effective utilization of each C4 component with almost no waste, and the resulting isobutylene-maleic anhydride polymer has high chemical value.

[0053] In actual production, isobutylene can be selected as a chemical raw material on its own, or it can be polymerized with maleic anhydride to prepare isobutylene-maleic anhydride polymer, depending on the needs.

[0054] In this invention, the isobutane component undergoes a dehydrogenation reaction, for example, in a circulating fluidized bed reactor, a fixed bed reactor, or a moving bed reactor.

[0055] In one embodiment, the dehydrogenation reaction of the isobutane component is carried out in a fixed-bed tubular reactor at a pressure of atmospheric pressure or above and a temperature between 500°C and 600°C. However, the present invention is not limited to this, and any method that enables the dehydrogenation reaction of the isobutane component is acceptable.

[0056] In one embodiment, the present invention utilizes the reversibility of the normal isomerization reaction to isomerize the n-butane component into isobutane, or to normalize the isobutane component into n-butane. This allows for flexible adjustment of the amounts of n-butane and isobutane produced, as well as the amounts of maleic anhydride and isobutene produced, thereby adapting it to industrial needs.

[0057] Specifically, the isomerization of the n-butane component to isobutane can be achieved using proprietary catalysts from UOP or AXENS. However, this invention is not limited to these methods; any catalyst capable of isomerizing the n-butane component to isobutane is acceptable.

[0058] Specifically, the isobutane component is n-configured to n-butane using UOP's Butamer process and proprietary catalyst. However, this invention is not limited to this; any method that enables the isobutane component to be n-configured to n-butane is acceptable.

[0059] In a second embodiment, the method for converting mixed C4 atoms according to the present invention includes the following steps:

[0060] Step 1: The mixed C4 is subjected to full hydrogenation treatment to convert the olefins in the mixed C4 into alkanes;

[0061] Step 2: Separate the mixture after Step 1 to obtain n-butane component and isobutane component respectively;

[0062] Step 3: The isobutane component is subjected to a dehydrogenation reaction to obtain isobutene.

[0063] Thus, the method of the present invention can convert almost all of the C4 components into n-butane and isobutene.

[0064] The processing techniques in steps 1 and 2 are similar to those in the first embodiment, and will not be described again here. The dehydrogenation reaction of the isobutane component in step 3 was also described in detail in the first embodiment, and will not be described again here.

[0065] In one embodiment, the method for converting mixed C4 according to the present invention further includes step 4, reacting the isobutylene with maleic anhydride to obtain an isobutylene-maleic anhydride polymer.

[0066] The reaction process of isobutylene and maleic anhydride has been described in detail in the first embodiment and will not be repeated here.

[0067] In another embodiment, the n-butane component can be isomerized as needed, and then the reaction product can be mixed with the isobutane component for dehydrogenation to obtain isobutene. In this way, the mixed C4 can be completely converted into isobutene after processing. The n-butane isomerization process has been described above and will not be repeated here.

[0068] In summary, this invention provides a flexible and adjustable method for converting mixed C4, which generates no waste, converts all components into high-value chemical products, and can be adjusted according to market needs.

[0069] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0070] Example 1

[0071] 14 kg of mixed C4A was subjected to a full hydrogenation reaction using the LY-2005 nickel-based hydrogenation catalyst from the Petrochemical Research Institute of China National Petroleum Corporation. The inlet temperature was 30 °C for the first stage and 150 °C for the second stage. The reaction pressure was 1.7 MPa, the hydrogen-to-oil volume ratio was 300:1, the dilution ratio was 6, and the fresh space velocity was 1.0 h⁻¹. -1 In the C4 distillation process, all olefins are converted into isobutane and n-butane. The isobutane and n-butane are then separated by pressurized distillation in a column. High-purity isobutane is collected from the top of the column, while heavy n-butane is collected from the bottom. The column temperature is 50°C, and the operating pressure is 0.6 MPa; the bottom temperature is 65°C, and the operating pressure is 0.65 MPa. The resulting n-butane mixture (mainly air, excluding n-butane) has a n-butane volume concentration of 3%–4%. A VPO catalyst is used, and the reaction temperature is 300°C with a space velocity of 1500 h⁻¹. -1Oxidation under a reaction pressure of 0.10 MPa can directly produce maleic anhydride; isobutane is directly dehydrogenated at 500℃ using a Cr-based isobutane dehydrogenation catalyst to produce isobutene. Maleic anhydride and isobutene in an equimolar ratio are dissolved in butyl acetate. After the reaction temperature reaches 60℃, 2% (by theoretical mass) of the target product azobisisobutyronitrile is added to the reactor and reacted at 60℃ for 4 hours. The resulting mixture is separated and dried to obtain pure isobutene-maleic anhydride copolymer. The mixed C4A is derived from refinery gas fractions, and the composition of C4 is shown in Table 1 below.

[0072] Table 1

[0073]

[0074]

[0075] Example 2

[0076] 11 kg of mixed C4B was subjected to a full hydrogenation reaction using the LY-2005 nickel-based hydrogenation catalyst from the Petrochemical Research Institute of China National Petroleum Corporation. The inlet temperature was 30°C for the first stage and 150°C for the second stage. The reaction pressure was 1.7 MPa, the hydrogen-to-oil volume ratio was 300:1, the dilution ratio was 6, and the fresh space velocity was 1.0 h⁻¹. -1 All olefins in C4 hydrocarbons are converted into isobutane and n-butane. Isobutane and n-butane are then separated by pressurized distillation in a distillation column. High-purity isobutane is collected from the top of the column, and heavy n-butane is collected from the bottom. The column temperature is 50°C, operating pressure is 0.6 MPa, and the bottom temperature is 65°C, operating pressure is 0.65 MPa. The obtained isobutane is subjected to the Butamer process and catalyst of UOP. It is then n-structured to n-butane under hydrogen conditions. The resulting n-butane mixture (mainly air, excluding n-butane) has a n-butane volume concentration of 3%–4%. A VPO catalyst is used, and the reaction temperature is 350°C and the space velocity is 1000 h⁻¹. -1 Maleic anhydride was prepared by oxidation under a reaction pressure of 0.15 MPa.

[0077] 11 kg of mixed C4 B' was subjected to a full hydrogenation reaction using the LY-2005 nickel-based hydrogenation catalyst from the Petrochemical Research Institute of China National Petroleum Corporation. The inlet temperature of the first stage was 30 °C, the inlet temperature of the second stage was 150 °C, the reaction pressure was 1.7 MPa, the hydrogen-to-oil volume ratio was 300:1, the dilution ratio was 6, and the fresh space velocity was 1.0 h⁻¹. -1In the C4 distillation process, all olefins are converted into isobutane and n-butane. The isobutane and n-butane are then separated by pressurized distillation in a distillation column. High-purity isobutane is collected from the top of the column, while the heavy n-butane component is collected from the bottom. The column temperature is 50°C, and the operating pressure is 0.6 MPa; the bottom temperature is 65°C, and the operating pressure is 0.65 MPa. The obtained n-butane is then converted into isobutane using a proprietary catalyst from UOP or AXENS. Isobutane is then directly dehydrogenated at 600°C using a Cr-based isobutane dehydrogenation catalyst to produce isobutene.

[0078] Maleic anhydride and isobutylene in a molar ratio of 1:2 were dissolved in isoamyl acetate. After the reaction temperature reached 70°C, benzoyl peroxide (3% by mass of the theoretically generated target product) was added to the reactor and reacted at 70°C for 3 hours. The resulting mixture was then separated and dried to obtain pure isobutylene-maleic anhydride copolymer. The mixed C4B was derived from a catalytic cracking unit, and the mixed C4B' was derived from an ethylene cracking unit. The composition is shown in Table 2.

[0079] Table 2

[0080]

[0081] Example 3

[0082] 12 kg of etherified C4 carbon was subjected to a full hydrogenation reaction using the LY-2005 nickel-based hydrogenation catalyst from the Petrochemical Research Institute of China National Petroleum Corporation. The inlet temperature was 40°C for the first stage and 140°C for the second stage. The reaction pressure was 1.5 MPa, the hydrogen-to-oil volume ratio was 600:1, the dilution ratio was 8, and the fresh space velocity was 2.0 h⁻¹. -1 In the C4 process, all olefins are converted into isobutane and n-butane. The isobutane and n-butane are then separated by pressurized distillation in a distillation column. High-purity isobutane is collected from the top of the column, and heavy n-butane is collected from the bottom. The column temperature is 50°C, operating pressure is 0.6 MPa, and the bottom temperature is 65°C, operating pressure is 0.65 MPa. The obtained isobutane is then converted to n-butane using UOP's Butamer process and proprietary catalyst, under controlled reaction temperature and pressure in a hydrogen-exposed state. The resulting n-butane mixture (mainly air, excluding n-butane) has a n-butane volume concentration of 3%–4%. A VPO catalyst is used, and the reaction temperature is 320°C and the space velocity is 1500 h⁻¹. -1 Maleic anhydride was prepared by direct oxidation under a reaction pressure of 0.13 MPa.

[0083] 12 kg of etherified C4 carbon was subjected to a full hydrogenation reaction using the LY-2005 nickel-based hydrogenation catalyst from the Petrochemical Research Institute of China National Petroleum Corporation. The inlet temperature was 40°C for the first stage and 140°C for the second stage. The reaction pressure was 1.5 MPa, the hydrogen-to-oil volume ratio was 600:1, the dilution ratio was 8, and the fresh space velocity was 2.0 h⁻¹. -1All olefins in C4 hydrocarbons are converted into isobutane and n-butane. The isobutane and n-butane are then separated by pressurized distillation in a distillation column. High-purity isobutane is collected from the top of the column, and heavy n-butane is collected from the bottom. The column temperature is 50°C, operating pressure is 0.6 MPa, and the bottom temperature is 65°C, operating pressure is 0.65 MPa. The obtained n-butane is then converted into isobutane using a proprietary catalyst from UOP or AXENS. All isobutane is then directly dehydrogenated at 550°C using a Cr-based isobutane dehydrogenation catalyst to produce isobutene.

[0084] Maleic anhydride and isobutylene were dissolved in isoamyl acetate at a molar ratio of 1:1. After the reaction temperature reached 70℃, 1% (by theoretical mass) of the target product azobisisobutyronitrile was added to the reactor and reacted at 70℃ for 2 hours. The resulting mixture was then separated and dried to obtain pure isobutylene-maleic anhydride copolymer. The composition of C4 after etherification is shown in Table 3 below.

[0085] Table 3

[0086] Analysis Project unit Post-ether C4 methane ％(v) — Ethane ％(v) — propane ％(v) — Isobutane ％(v) 41.43 n-Butane ％(v) 10.14 pentane ％(v) 0.51 ethylene ％(v) — propylene ％(v) 0.23 trans-2-butene ％(v) 18.27 n-Butene ％(v) 15.5 Isobutylene ％(v) 0.27 cis-2-butene ％(v) 13.01 1,3-Butadiene ％(v) 0.1 Other (methanol / dimethyl ether) ％(v) 0.54

[0087] The present invention provides a mixed C4 conversion method that allows for adjustment of the conversion products as needed. It can convert almost all of the product into n-butane, isobutane, maleic anhydride, and isobutene, achieving high conversion rates and high product purity. Furthermore, when preparing an isobutene-maleic anhydride copolymer, the copolymer product yield is approximately 90%, and the copolymer purity is almost 100%.

[0088] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for converting mixed C4 atoms, characterized in that, Includes the following steps: Step 1: The mixed C4 is subjected to full hydrogenation treatment to convert the olefins in the mixed C4 into alkanes; Step 2: Separate the mixture after Step 1 to obtain n-butane component and isobutane component respectively; Step 3: Oxidize the n-butane component obtained in Step 2 to obtain maleic anhydride; The isobutane component obtained in step 2 is subjected to a dehydrogenation reaction to prepare isobutene; Step 4: React the maleic anhydride with isobutylene to obtain an isobutylene-maleic anhydride polymer.

2. The method for converting mixed C4 carbon atoms according to claim 1, characterized in that, It also includes performing an ortho-configuration reaction on the isobutane component, and then mixing the reaction product with the n-butane component for oxidation treatment to obtain maleic anhydride.

3. The method for converting mixed C4 carbon atoms according to claim 1, characterized in that, The mixture after step 1 is separated by distillation, with the isobutane component being collected from the top of the distillation column and the n-butane component being collected from the bottom of the distillation column.

4. The method for converting mixed C4 carbon atoms according to claim 1, characterized in that, The mixed C4 is derived from a catalytic cracking unit, a coking unit, an ethylene steam cracking unit, a methanol-to-olefins unit, or an MTBE production unit; the mixed C4 contains at least one of 1-butene, isobutene, 1,3-butadiene, n-butane, isobutane, cis-2-butene, and trans-2-butene.

5. The method for converting mixed C4 according to claim 1, characterized in that, The molar ratio of isobutylene to maleic anhydride is 2:1 to 1:1, the reaction temperature of maleic anhydride and isobutylene is 50-70℃, and the reaction time is 2-4h.

6. The method for converting mixed C4 according to claim 1, characterized in that, The reaction between maleic anhydride and isobutylene is carried out under the action of an initiator, which is an organic peroxide or an azo compound, and the amount of the initiator is 0.5-3 wt% of the theoretical amount of isobutylene-maleic anhydride polymer.

7. The method for converting mixed C4 according to claim 1, characterized in that, It also includes isomerizing the n-butane component, and then mixing the reaction product with the isobutane component to carry out a dehydrogenation reaction to obtain isobutene.

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