Conversion method of mixed C4

Abstract

The present invention provides a mixed C4 conversion method, which comprises: 1, carrying out full hydrogenation treatment on mixed C4 so as to convert olefins in the mixed C4 into alkanes, step 2, separating the mixture treated in the step 1 to respectively obtain an n-butane component and an isobutane component; and step 3, carrying out oxidation treatment on the n-butane component obtained in the step 2 to obtain maleic anhydride. According to the method, closed-loop conversion of the mixed C4 to the chemical material can be realized, each component can be fully utilized, almost no waste is generated, and meanwhile, each process condition in the method is mild, easy to control, short in flow and simple in process.

Description

Technical Field

[0001] The invention relates to the technical field of comprehensive utilization of mixed carbon four, and in particular to a conversion method of mixed carbon four. Background Art

[0002] Mixed C4 refers to liquefied gas with a butane (n-butane, isobutane) and butene (1,3-butadiene, 1-butene, 2-butene (cis-2-butene, trans-2-butene), isobutene, etc.) content of more than 95%, mainly derived from the by-products of the catalytic cracking unit of the refinery, the ethylene steam cracking unit, and the methanol to olefins (MTO) process.

[0003] In recent years, with the rapid improvement of crude oil processing capacity and the continuous increase in ethylene production, the mixed C4 resources in my country's petrochemical industry have been expanding. 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, in general, the utilization rate of mixed C4 resources in my country is still relatively low, especially the chemical utilization is still in its early stages. Butadiene, n-butene, isobutylene, n-butane and isobutane in mixed C4 of refineries and ethylene cracking are all important organic chemical raw materials. At present, the utilization of C4 resources in my country is mainly concentrated in olefins, and because the surplus C4 of various refining and chemical enterprises cannot be integrated together and can only be processed separately, the scale of C4 utilization equipment in my country is small, the technical development capability is poor, and only olefin resources cannot be fully utilized. For example, a considerable part of n-butene and isobutylene are still burned as fuel. Due to the low utilization rate of C4 resources in some refining and chemical enterprises, the butadiene products separated by cracking C4 cannot be fully digested locally, and the surplus products need to be exported. Due to the high cost of export, economic benefits are lost.

[0004] At present, mixed C4 mainly comes from refinery catalytic cracking units and ethylene steam cracking units. Typical processing and utilization methods include:

[0005] (1) Mixed C4 produced by catalytic cracking units is mostly produced by etherification of isobutylene to produce methyl tert-butyl ether (MTBE), which is generally used as a high-octane gasoline blending component. A few companies use part of C4 to produce methyl ethyl ketone.

[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 firstly separated from 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: (1) copolymerizing part or all of the terminal olefins in a material containing mixed C4 with maleic anhydride under nitrogen, in the presence of an initiator and an organic solvent; (2) performing gas-liquid separation on the product obtained in step (1) to obtain 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) performing steam cracking reaction on the gas phase product obtained in step (2), and returning the cracked gas obtained to the material in step (1); (4) performing liquid-solid separation on the liquid-solid mixture obtained in step (2), and the obtained solid product is a polymer containing maleic anhydride functional groups; the mixed C4 is a mixture containing C4 hydrocarbon compounds. The mixed C4 can be converted into a functional material raw material for utilization. In the invention, the C4 terminal olefin reacts with maleic anhydride, and the product is a mixture, which is difficult to separate and has a low yield. Therefore, the utilization rate of the mixed C4 in the invention is low, and the performance of the obtained polymer is difficult to control.

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

[0009] The main purpose of the present invention is to provide a mixed carbon four conversion method to overcome the defect of low utilization rate of mixed carbon four in the prior art.

[0010] In order to achieve the above object, the present invention provides a mixed C4 conversion method, comprising the following steps:

[0011] Step 1, subjecting the mixed C4 to full hydrogenation treatment to convert olefins in the mixed C4 into alkanes;

[0012] Step 2, separating the mixture treated in step 1 to obtain a normal butane component and an isobutane component respectively;

[0013] Step 3, oxidizing 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 comprises step 4, reacting the maleic anhydride with isobutylene to obtain an isobutylene-maleic anhydride polymer.

[0015] In the mixed C4 conversion method of the present invention, the isobutylene is prepared by dehydrogenation reaction of the isobutane component.

[0016] The mixed C4 conversion method of the present invention further comprises subjecting the isobutane component to a normalization reaction, and then mixing the reaction product with the normal-butane component for oxidation treatment to obtain maleic anhydride.

[0017] In the mixed C4 conversion method of the present invention, the mixture treated in step 1 is separated by distillation, the isobutane component is extracted from the top of the distillation tower, and the normal butane component is extracted from the bottom of the distillation tower.

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

[0019] The mixed C4 conversion method of the present invention comprises the following steps: the molar ratio of the isobutylene to the maleic anhydride is 2:1-1:1, the reaction temperature of the maleic anhydride and the isobutylene is 50-70°C, and the reaction time is 2-4h.

[0020] The mixed C4 conversion method of the present invention comprises the following steps: the reaction of the maleic anhydride and the isobutylene is carried out under the action of an initiator, the initiator is an organic peroxide or an azo compound, and the amount of the initiator is 0.5-3wt% of the theoretical amount of the isobutylene-maleic anhydride polymer produced.

[0021] In order to achieve the above object, the present invention also provides a mixed C4 conversion method, comprising the following steps:

[0022] Step 1, subjecting the mixed C4 to full hydrogenation treatment to convert olefins in the mixed C4 into alkanes;

[0023] Step 2, separating the mixture treated in step 1 to obtain a normal butane component and an isobutane component respectively;

[0024] Step 3, dehydrogenating the isobutane component to obtain isobutene.

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

[0026] The mixed C4 conversion method of the present invention further comprises subjecting the n-butane component to an isomerization reaction, and then mixing the reaction product with the isobutane component to a dehydrogenation reaction to obtain isobutylene.

[0027] Beneficial effects of the present invention:

[0028] The present invention can convert mixed C4 into chemical raw materials such as n-butane, isobutane, maleic anhydride, isobutylene, etc., and the generated amount of each substance can be selected according to needs, which has the characteristics of flexibility and adjustability; in addition, the present invention can also convert mixed C4 into two raw materials, isobutylene and maleic anhydride, and then prepare copolymers through polar polymerization. Therefore, the method of the present invention can realize the closed-loop conversion of mixed C4 to chemical materials, each component can be fully utilized, and almost no waste is generated. At the same time, the process conditions in the method are mild, easy to control, the process is short, and the process is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a flow chart of mixed C4 conversion in one embodiment of the present invention. DETAILED DESCRIPTION

[0030] The technical scheme of the present invention is described in detail below. The following implementation modes are implemented on the premise of the technical scheme 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 implementation modes. The structures or experimental methods of specific conditions are not specified in the following implementation modes, and generally conventional conditions are followed.

[0031] The present invention provides a mixed C4 conversion method, such as Figure 1 As shown. Among them, the mixed C4 can come from a catalytic cracking unit, a coking unit, an ethylene steam cracking unit, a methanol to olefins unit, and an MTBE production unit. In one embodiment, the catalytic cracking unit, the coking unit, the ethylene steam cracking unit, and the methanol to olefins unit produce mixed C4 as a by-product, and the MTBE production unit produces etherified C4 as a by-product. Etherified C4 refers to the C4 component remaining after the etherification reaction of isobutylene.

[0032] The mixed C4 conversion method of the present invention can adjust the conversion product according to needs, has flexible process, strong adaptability and high industrial application value.

[0033] In a first embodiment, the conversion method of mixed C4 of the present invention comprises the following steps:

[0034] Step 1, subjecting the mixed C4 to full hydrogenation treatment to convert olefins in the mixed C4 into alkanes;

[0035] Step 2, separating the mixture treated in step 1 to obtain a normal butane component and an isobutane component respectively;

[0036] Step 3, oxidizing the n-butane component obtained in step 2 to obtain maleic anhydride.

[0037] In this way, 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, isobutylene, 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 is fully hydrotreated, that is, the olefins in the mixed C4 are hydrotreated, specifically, all the olefins in the mixed C4 are converted into alkanes by hydrogenation. Thus, the mixture after step 1 is substantially composed of alkanes, and mainly n-butane and isobutane.

[0040] The present invention does not particularly limit the hydrogenation process conditions. In one embodiment, the full hydrogenation process conditions are: using LY-2005 nickel-based hydrogenation catalyst from China Petroleum and Chemical Research Institute, inlet temperature 30-180°C, reaction pressure ≥1.5MPa, hydrogen-oil volume ratio 300-600:1, dilution ratio 2-10, fresh reaction space velocity 0.5-2.5h -1 .

[0041] Step 2 is: separating the mixture treated in step 1 to obtain a normal butane component and an isobutane component respectively.

[0042] In one embodiment, the mixture after the treatment in step 1 is separated by distillation, for example, in a distillation tower, the isobutane component is extracted from the top of the distillation tower, and the normal butane component is extracted from the bottom of the distillation tower. The present invention utilizes the difference in boiling points between normal butane and isobutane, and the alkane mixture obtained in step 1 can be separated by distillation. The isobutane component obtained at the top of the tower is mainly isobutane, which may contain a small amount of gas impurities; the normal butane component obtained at the bottom of the tower is mainly normal butane, which may contain a small amount of heavy components. The normal butane component and the isobutane component obtained by the present invention can be used separately as chemical raw materials.

[0043] The present invention does not particularly limit the structure of the distillation tower, and any conventional distillation tower in the art can be used. In one embodiment, during the distillation, the tower top temperature is 40-60°C, such as 50°C, the operating pressure is 0.5-0.7MPa, such as 0.6MPa, the tower bottom temperature is 55-75°C, such as 65°C, and the operating pressure is 0.60-0.70MPa, such as 0.65MPa.

[0044] Step 3 is: subjecting the n-butane component obtained in step 2 to oxidation treatment to obtain maleic anhydride.

[0045] In the present invention, the method for oxidizing the n-butane component can be a n-butane fixed bed oxidation method, a n-butane fluidized bed oxidation method or a circulating fluidized bed oxidation method, and 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, the reaction temperature is 350-400°C, the space velocity is 1000-2000h -1 The oxidation is carried out under the conditions of a reaction pressure of 0.10-0.15 MPa, but the present invention is not limited thereto, and any prior art that can oxidize n-butane to maleic anhydride can be used.

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

[0047] In one embodiment, the conversion method of mixed C4 of the present invention further comprises step 4, reacting maleic anhydride with isobutylene to obtain isobutylene-maleic anhydride polymer. In this way, the present invention can convert mixed C4 into 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 about 90%.

[0048] In one embodiment, the isobutylene and maleic anhydride of the present invention are copolymerized in a molar ratio of 1:1 to obtain an alternating copolymer of isobutylene and maleic anhydride. In one embodiment, in order to completely react the maleic anhydride, the molar ratio of isobutylene to maleic anhydride is 2:1-1:1.

[0049] The polymerization reaction of isobutylene and maleic anhydride of the present invention is carried out under the action of an initiator in a solvent environment. The present invention does not particularly limit the types of initiators and solvents, and conventional initiators and solvents used for polymerization reactions in the art can be used. In one embodiment, the initiator of the present 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 mass of the theoretical product isobutylene-maleic anhydride polymer.

[0050] In one embodiment, the solvent of the polymerization reaction of the present invention is an organic ester, for example, at least one of 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 butyrate, isoamyl formate, isoamyl acetate, 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 the solvent used is, for example, such that the amount of theoretical product isobutylene-maleic anhydride polymer generated accounts for 10%-20% of the mass of the reaction system.

[0051] In one embodiment, the polymerization reaction temperature in step 4 of the present invention is 50-70° C., and the reaction time is 2-4 hours.

[0052] The present invention does not particularly limit the source of isobutylene, which can be a commercially available product. However, preferably, isobutylene is prepared by dehydrogenation reaction of the isobutane component obtained by the present invention. In this way, the mixed C4 is hydrogenated and separated, and the obtained n-butane is oxidized to maleic anhydride, and the obtained isobutane is dehydrogenated to obtain isobutylene, and maleic anhydride and isobutylene are polymerized to obtain isobutylene-maleic anhydride polymer. The conversion method of the mixed C4 of the present invention can make the various components of the C4 fully and effectively utilized, and almost no waste is generated, and the obtained isobutylene-maleic anhydride polymer has a higher chemical value.

[0053] In actual production, isobutylene can be selected as a chemical raw material alone or polymerized with maleic anhydride to prepare isobutylene-maleic anhydride polymer.

[0054] In the present invention, the dehydrogenation reaction of the isobutane component is carried out in, for example, 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, the reaction pressure is normal pressure or above, and the reaction temperature is between 500° C. and 600° C. However, the present invention is not limited thereto, as long as the isobutane component can be dehydrogenated.

[0056] In one embodiment, the present invention can utilize the reversibility of the normal isomerization reaction to isomerize the normal butane component into isobutane, or normalize the isobutane component into normal butane. In this way, the production amount of normal butane and isobutane can be flexibly adjusted, and the production amount of maleic anhydride and isobutylene can also be adjusted, thereby adapting it to industrial needs.

[0057] Specifically, the isomerization of the n-butane component into isobutane can be carried out using a UOP or AXENS proprietary catalyst. However, the present invention is not limited thereto, as long as the n-butane component can be isomerized into isobutane.

[0058] Specifically, the isobutane component is converted into normal butane using the Butamer process and proprietary catalyst of UOP. However, the present invention is not limited thereto, as long as the isobutane component can be converted into normal butane.

[0059] In a second embodiment, the conversion method of mixed C4 of the present invention comprises the following steps:

[0060] Step 1, subjecting the mixed C4 to full hydrogenation treatment to convert olefins in the mixed C4 into alkanes;

[0061] Step 2, separating the mixture treated in step 1 to obtain a normal butane component and an isobutane component respectively;

[0062] Step 3, dehydrogenating the isobutane component to obtain isobutene.

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

[0064] The treatment processes of step 1 and step 2 are similar to those of the first embodiment, and will not be described in detail here. In step 3, the dehydrogenation reaction of the isobutane component is also described in detail in the first embodiment, and will not be described in detail here.

[0065] In one embodiment, the mixed C4 conversion method of the present invention further comprises 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 also be subjected to an isomerization reaction as needed, and then the reaction product is mixed with the isobutane component for a dehydrogenation reaction to obtain isobutylene. In this way, the mixed C4 can be completely converted into isobutylene after treatment. The n-butane isomerization reaction process has been described above and will not be repeated here.

[0068] In summary, the present invention provides a flexibly adjustable mixed C4 conversion method, which neither generates waste, but all components can be converted 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 fully hydrogenated using LY-2005 nickel-based hydrogenation catalyst from PetroChina Petrochemical Research Institute, with a first stage inlet temperature of 30°C, a second stage inlet temperature of 150°C, a reaction pressure of 1.7 MPa, a hydrogen-to-oil volume ratio of 300:1, a dilution ratio of 6, and a fresh reaction space velocity of 1.0 h -1 . All olefins in C4 are converted into two alkanes, isobutane and n-butane. Isobutane and n-butane are separated by pressure distillation in a distillation tower. High-purity isobutane is produced from the top of the tower, and n-butane heavy components are produced from the bottom of the tower. The top temperature is 50°C, the operating pressure is 0.6MPa, and the bottom temperature is 65°C, and the operating pressure is 0.65MPa. The volume concentration of n-butane in the separated n-butane mixed gas (gases other than n-butane are mainly air) is 3% to 4%. VPO catalyst is used, the reaction temperature is 300°C, and the space velocity is 1500h -1Oxidation can be carried out under the conditions of 0.10MPa reaction pressure to directly produce maleic anhydride; isobutane is directly dehydrogenated at 500°C using a Cr-based isobutane dehydrogenation catalyst to produce isobutylene. Maleic anhydride and isobutylene in equal molar ratios are added to butyl acetate for dissolution. After the reaction temperature reaches 60°C, azobisisobutyronitrile with a theoretical mass of 2% of the target product is added to the reactor and reacted at 60°C for 4h. The mixed solution after the reaction is separated and dried to obtain pure isobutylene-maleic anhydride copolymer. Among them, mixed carbon four A comes from oil refining gas fraction, and the composition of carbon four is shown in Table 1 below.

[0072] Table 1

[0073]

[0074]

[0075] Example 2

[0076] 11 kg of mixed C4B was fully hydrogenated using LY-2005 nickel-based hydrogenation catalyst from PetroChina Petrochemical Research Institute, with a first stage inlet temperature of 30 °C, a second stage inlet temperature of 150 °C, a reaction pressure of 1.7 MPa, a hydrogen-to-oil volume ratio of 300:1, a dilution ratio of 6, and a fresh reaction space velocity of 1.0 h -1 . All olefins in C4 are converted into two alkanes, isobutane and n-butane. Isobutane and n-butane are separated by pressurized distillation in a distillation tower. High-purity isobutane is produced from the top of the tower, and n-butane heavy components are produced from the bottom of the tower. The top temperature is 50°C, the operating pressure is 0.6MPa, the bottom temperature is 65°C, and the operating pressure is 0.65MPa. The isobutane obtained adopts UOP's Butamer process and catalyst. It is normalized to n-butane in the presence of hydrogen; the volume concentration of n-butane in the obtained n-butane mixed gas (gas other than n-butane is mainly air) is 3% to 4%. VPO catalyst is used, the reaction temperature is 350°C, and the space velocity is 1000h -1 and a reaction pressure of 0.15 MPa to oxidize and prepare maleic anhydride;

[0077] 11 kg of mixed C4 B' was fully hydrogenated using LY-2005 nickel-based hydrogenation catalyst from PetroChina Petrochemical Research Institute, with a first stage inlet temperature of 30 °C, a second stage inlet temperature of 150 °C, a reaction pressure of 1.7 MPa, a hydrogen-to-oil volume ratio of 300:1, a dilution ratio of 6, and a fresh reaction space velocity of 1.0 h -1. All olefins in C4 are converted into two alkanes, isobutane and n-butane. Isobutane and n-butane are separated by pressure distillation in a distillation tower. High-purity isobutane is produced from the top of the tower, and n-butane heavy components are produced from the bottom of the tower. The top temperature is 50°C, the operating pressure is 0.6MPa, and the bottom temperature is 65°C, and the operating pressure is 0.65MPa. The obtained n-butane is converted into isobutane using UOP or AXENS proprietary catalysts. Isobutane is directly dehydrogenated to produce isobutylene at 600°C using a Cr-based isobutane dehydrogenation catalyst.

[0078] Maleic anhydride and isobutylene in a molar ratio of 1:2 were added to isoamyl acetate for dissolution. After the reaction temperature reached 70°C, 3% of the target product theoretically generated by mass of benzoyl peroxide was added to the reactor for reaction at 70°C for 3 hours. The mixed solution after the reaction was separated and dried to obtain pure isobutylene-maleic anhydride copolymer. Among them, mixed carbon four B was derived from a catalytic cracking unit, and mixed carbon four B' was derived from an ethylene cracking unit, and the composition was shown in Table 2.

[0079] Table 2

[0080]

[0081] Example 3

[0082] 12 kg of etherified C4 was fully hydrogenated using LY-2005 nickel-based hydrogenation catalyst from PetroChina Petrochemical Research Institute, with a first stage inlet temperature of 40°C, a second stage inlet temperature of 140°C, a reaction pressure of 1.5 MPa, a hydrogen-to-oil volume ratio of 600:1, a dilution ratio of 8, and a fresh reaction space velocity of 2.0 h -1 . All olefins in C4 are converted into two alkanes, isobutane and n-butane. Isobutane and n-butane are separated by pressurized distillation in a distillation tower. High-purity isobutane is produced from the top of the tower, and n-butane heavy components are produced from the bottom of the tower. The top temperature is 50°C, the operating pressure is 0.6MPa, and the bottom temperature is 65°C, and the operating pressure is 0.65MPa. The isobutane obtained is normalized to n-butane by using UOP's Butamer process and proprietary catalyst, and controlling a certain reaction temperature and reaction pressure in the presence of hydrogen. The volume concentration of n-butane in the obtained n-butane mixed gas (gas other than n-butane is mainly air) is 3% to 4%. VPO catalyst is used, the reaction temperature is 320°C, and the space velocity is 1500h -1 Directly oxidize to prepare maleic anhydride under the conditions of reaction pressure of 0.13 MPa;

[0083] 12 kg of etherified C4 was fully hydrogenated using LY-2005 nickel-based hydrogenation catalyst from PetroChina Petrochemical Research Institute, with a first stage inlet temperature of 40°C, a second stage inlet temperature of 140°C, a reaction pressure of 1.5 MPa, a hydrogen-to-oil volume ratio of 600:1, a dilution ratio of 8, and a fresh reaction space velocity of 2.0 h -1. All olefins in C4 are converted into two alkanes, isobutane and n-butane. Isobutane and n-butane are separated by pressure distillation in a distillation tower. High-purity isobutane is produced from the top of the tower, and n-butane heavy components are produced from the bottom of the tower. The top temperature is 50°C, the operating pressure is 0.6MPa, and the bottom temperature is 65°C, and the operating pressure is 0.65MPa. The obtained n-butane is converted into isobutane using UOP or AXENS proprietary catalysts. All isobutane is directly dehydrogenated to produce isobutylene at 550°C using a Cr-based isobutane dehydrogenation catalyst.

[0084] Maleic anhydride and isobutylene in a molar ratio of 1:1 were added to isoamyl acetate for dissolution. After the reaction temperature reached 70°C, 1% of the theoretical mass of the target product, azobisisobutyronitrile, was added to the reactor for reaction at 70°C for 2 hours. The mixed solution after the reaction was separated and dried to obtain a pure isobutylene-maleic anhydride copolymer. Among them, the composition of the carbon four C after etherification is shown in Table 3 below.

[0085] Table 3

[0086] Analyze Project unit 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 Others (methanol / dimethyl ether) ％(v) 0.54

[0087] The conversion method of the mixed C4 of the present invention can adjust the conversion product as required. Almost all of the conversion can be made into normal butane, isobutane, maleic anhydride and isobutylene as required, with high conversion rate and high purity of the obtained product. In addition, when preparing isobutylene-maleic anhydride copolymer, the copolymer product is about 90% and the copolymer purity is almost 100%.

[0088] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A mixed C4 conversion method, characterized in that: The steps include: Step 1, subjecting the mixed C4 to full hydrogenation treatment to convert olefins in the mixed C4 into alkanes; Step 2, separating the mixture treated in step 1 to obtain a normal butane component and an isobutane component respectively; Step 3, oxidizing the n-butane component obtained in step 2 to obtain maleic anhydride.

2. The mixed C4 conversion method according to claim 1, characterized in that: The method further comprises step 4, reacting the maleic anhydride with isobutylene to obtain an isobutylene-maleic anhydride polymer.

3. The mixed C4 conversion method according to claim 2, characterized in that: The isobutylene is prepared by dehydrogenation reaction of the isobutane component.

4. The method for converting mixed C4 according to claim 1, characterized in that: The method also includes subjecting the isobutane component to a normalization reaction, and then mixing the reaction product with the normal butane component for oxidation treatment to obtain maleic anhydride.

5. The mixed C4 conversion method according to claim 1, characterized in that: The mixture treated in step 1 is separated by distillation, the isobutane component is extracted from the top of the distillation tower, and the normal butane component is extracted from the bottom of the distillation tower.

6. The mixed C4 conversion method 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, and an MTBE production unit; the mixed C4 contains at least one of 1-butene, isobutylene, 1,3-butadiene, n-butane, isobutane, cis-2-butene, and trans-2-butene.

7. The mixed C4 conversion method according to claim 2, characterized in that: The molar ratio of the isobutylene to the maleic anhydride is 2:1-1:1, the reaction temperature of the maleic anhydride and the isobutylene is 50-70° C., and the reaction time is 2-4 hours.

8. The mixed C4 conversion method according to claim 2, characterized in that: The reaction of the maleic anhydride and the isobutylene is carried out under the action of an initiator, the initiator is an organic peroxide or an azo compound, and the amount of the initiator used is 0.5-3wt% of the theoretical amount of the isobutylene-maleic anhydride polymer produced.

9. A mixed C4 conversion method, characterized in that: The steps include: Step 1, subjecting the mixed C4 to full hydrogenation treatment to convert olefins in the mixed C4 into alkanes; Step 2, separating the mixture treated in step 1 to obtain a normal butane component and an isobutane component respectively; Step 3, dehydrogenating the isobutane component to obtain isobutene.

10. The mixed C4 conversion method according to claim 9, characterized in that: The method further comprises step 4, reacting the isobutylene with maleic anhydride to obtain an isobutylene-maleic anhydride polymer.

11. The mixed C4 conversion method according to claim 9, characterized in that: The method further comprises subjecting the n-butane component to an isomerization reaction, and then mixing the reaction product with the isobutane component to carry out a dehydrogenation reaction to obtain isobutene.

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