A method and device for recovering normal butane from isooctane oil as raw material for producing maleic anhydride

Abstract

The present invention discloses a method for recovering normal butane in isooctane oil as a raw material for producing maleic anhydride, comprising: the product after alkylation reaction enters a debutanizer for separation, the upper section of the debutanizer extracts mixed butane and enters a butane separation tower for separation by increasing the operating temperature of the debutanizer bottom, and the lower section of the butane separation tower extracts normal butane and sends it to a maleic anhydride reaction device; a part of the isobutane extracted from the top of the butane separation tower is returned to the alkylation reactor, and the other part is mixed with the isooctane product extracted from the bottom of the debutanizer; the isopentane extracted from the bottom of the butane separation tower is mixed with the isooctane product extracted from the bottom of the debutanizer. The present invention significantly reduces the production cost of the maleic anhydride process by recovering normal butane in the isooctane product of the alkylation process as a raw material for the maleic anhydride process; and by blending the surplus isobutane C4 and isopentane C5 in the maleic anhydride process raw materials into the isooctane product, the quality and yield of the isooctane product after the normal butane is extracted are guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of chemical product production, and in particular to a method and a device for recovering normal butane in isooctane oil as a raw material for producing maleic anhydride. Background Art

[0002] BDO (1,4-butanediol) is the main raw material for biodegradable plastics. Currently, there are two mature production processes in China: the maleic anhydride method using maleic anhydride as the raw material and the acetylene aldehyde method using acetylene as the main raw material.

[0003] Although the acetylene aldehyde method has certain cost advantages, it is restricted by raw materials and is mostly used in coal chemical projects. In comparison, although the benzene-based maleic anhydride technology is earlier and more mature, the price of benzene is higher than that of n-butane most of the time. More than 75% of the production cost of maleic anhydride is raw material costs. In addition, the unit output of the n-butane method is theoretically greater than that of the benzene method. Considering that the n-butane method has less toxicity and environmental pollution, the latter is obviously more advantageous. How to obtain cheap n-butane resources is an issue that needs to be considered when producing maleic anhydride using the n-butane method. Summary of the invention

[0004] The object of the present invention is to provide a method and device for recovering n-butane in isooctane oil as a raw material for producing maleic anhydride, so as to solve the problem of shortage and high price of n-butane raw material in anhydride device.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for recovering normal butane in isooctane oil as a raw material for producing maleic anhydride, comprising: the product after alkylation reaction enters a debutanizer for separation; by increasing the operating temperature of the debutanizer bottom, the upper section of the debutanizer produces mixed butane and enters a butane separation tower for separation; the lower section of the butane separation tower produces normal butane and is sent to a maleic anhydride reaction device; a part of the isobutane produced from the top of the butane separation tower is returned to an alkylation reactor, and the other part is mixed with the isooctane product produced from the bottom of the debutanizer; the isopentane produced from the bottom of the butane separation tower is mixed with the isooctane product produced from the bottom of the debutanizer.

[0007] Preferably, a material mixer is provided at the bottom of the debutanizer, and the material mixer is used to evenly mix the isobutane produced from the top of the butane separation tower, the isooctane product produced from the bottom of the debutanizer, and the isopentane produced from the bottom of the butane separation tower.

[0008] Preferably, the debutanizer tower top operating pressure is 0.4-0.68 MPa, the tower bottom temperature is 160-200° C., and the reflux ratio is 1.6-2.4.

[0009] Preferably, the operating pressure at the top of the butane separation tower is controlled at 0.38-0.58 MPa, the temperature at the bottom of the tower is controlled at 50-70° C., and the reflux ratio is controlled at 2-3.2.

[0010] A device for recovering normal butane from isooctane oil as a raw material for producing maleic anhydride, comprising an alkylation reactor, a debutanizer, and a butane separation tower connected in sequence, wherein:

[0011] The product after the reaction in the alkylation reactor enters the debutanizer through the material line;

[0012] The upper material extraction line of the debutanizer is connected to the butane separation tower, the top material extraction line returns to the alkylation reactor, and the bottom material extraction line is connected to the mixer;

[0013] The bottom production line of the butane separation tower is connected to the mixer, the top production line is connected to the alkylation reactor and the mixer respectively, and the lower production line produces normal butane.

[0014] Preferably, the mixer is an SV+SK type mixer, wherein the SV type unit is a cylinder assembled from corrugated plates of a certain specification, with a maximum dispersion degree of 1-2 μm, and liquid-liquid phase and gas-gas phase non-uniformity coefficients ≤1-5%; the SK type unit is welded from single-channel left and right twisted spiral sheets, and is used for small flow rates and high-viscosity media mixed with impurities or with a viscosity of ≤106 centipoise.

[0015] Preferably, the lower production line of the butane separation tower is connected to the maleic anhydride process.

[0016] In summary, the technical solution of the present invention has the following beneficial effects:

[0017] 1) By recovering 5-8% of n-butane from the isooctane product of the alkylation process, it can be used as a raw material for the maleic anhydride process, greatly reducing the production cost of the maleic anhydride process.

[0018] 2) By recovering the surplus isobutane C4 and isopentane C5 in the maleic anhydride process raw materials and using them for blending with isooctane products, the quality of the isooctane products is guaranteed, while the output of the isooctane products does not decrease significantly and may even increase. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structure of the alkylation process-maleic anhydride process and a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention, but this does not constitute a limitation on the protection scope of the present invention.

[0021] A method for recovering normal butane in isooctane oil as a raw material for producing maleic anhydride comprises first feeding a raw material mixed with C4 into an alkylation reactor R101, and alkylating isobutane and butene in the mixed C4 under the catalysis of 98% sulfuric acid to generate isooctane in the reactor. Since normal butane in the mixed C4 does not participate in the alkylation reaction, and the isobutane participating in the reaction is excessive, the alkylation oil contains normal butane, excessive isobutane and reaction byproduct C5-C16 components, and the composition of the isooctane product is shown in Table 1. The isooctane product is extracted from the lower end of the alkylation reactor R101 and fed to a debutanizer T101 for separation.

[0022] Table 1 Isooctane product composition

[0023] composition Isobutane%(m / m) n-Butane%(m / m) Isopentane%(m / m) C6-C7 %(m / m) Isooctane%(m / m) C8-C14%(m / m) ≥C15%(m / m) Isooctane Products 0.2 7.8 4.1 9.2 51.5 25.4 1.8

[0024] In debutanizer T101, isobutane is extracted from the top of debutanizer T101; isooctane product is extracted from the bottom of debutanizer T101; mixed butane is extracted from the debutanizer T101 line and sent to the maleic anhydride process butane separation tower T102 for separation. Since the boiling point of n-butane is lower than that of isooctane, if it is necessary to recover n-butane at the bottom of the tower, it is necessary to further increase the operating temperature at the bottom of the tower and evaporate n-butane to the upper section of the tower for extraction. Preferably, the operating pressure at the top of debutanizer T101 is controlled to be 0.4-0.68MPa, the bottom temperature is 160-200℃, and the reflux ratio is 1.6-2.4, which can effectively recover 5-8% n-butane in the isooctane product.

[0025] In the butane separation tower T102, n-butane is produced from the lower section of the butane separation tower T102 and sent to the maleic anhydride reaction unit; isobutane is produced from the top of the butane separation tower T102; it is mixed with the isobutane produced from the top of the debutanizer T101, part of which is returned to the alkylation reactor R101, and the other part is mixed with the isooctane product produced from the bottom of the debutanizer T101; the isopentane produced from the bottom of the butane separation tower T102 is mixed with the isooctane product produced from the bottom of the debutanizer T101.

[0026] Preferably, the top operating pressure of the butane separation tower T102 is controlled at 0.38-0.58 MPa, the bottom temperature is controlled at 50-70° C., and the reflux ratio is controlled at 2-3.2.

[0027] In order to ensure the mixing effect, SV+SK mixer M101 is used to improve the mixing effect of isooctane, isobutane and isopentane to ensure stable and reliable product quality.

[0028] The SV type unit is a cylinder assembled from corrugated plates of certain specifications, with a maximum dispersion of 1-2μm and a liquid-liquid phase and gas-gas phase non-uniformity coefficient of ≤1-5%. It is suitable for liquid-liquid, liquid-gas, gas-gas mixed emulsification, reaction, absorption, extraction, and enhanced heat transfer processes with a viscosity of ≤102 centipoise. The SK type unit is welded from a single-channel left and right twisted spiral sheet, and is particularly suitable for small flow rates and high-viscosity media mixed with impurities or with a viscosity of ≤106 centipoise.

[0029] Isooctane and C4 / C5 enter the mixer M101 from the SK unit side. The SK unit improves the dispersion performance by adjusting the number of spiral blades, welding angle and mixer length, and initially disperses the materials entering the mixer M101 evenly. Then, the corrugated plate filler of the SV unit is used to further disperse and mix the materials to ensure the uniformity of the mixing of the isooctane product and C4 / C5, and to ensure the quality of the mixed isooctane product.

[0030] By recovering 5-8% of n-butane from the isooctane product of the alkylation process, it can be used as a raw material for the maleic anhydride process, greatly reducing the production cost of the maleic anhydride process.

[0031] By recovering the surplus isobutane C4 and isopentane C5 in the maleic anhydride process raw materials and using them for blending with isooctane products, the quality of the isooctane products is guaranteed while ensuring that the output of the isooctane products does not decrease significantly or even increases.

[0032] The following examples are used to illustrate a method for recovering normal butane from isooctane oil as a raw material for producing maleic anhydride.

[0033] Example 1

[0034] The raw material mixed with C4 is sent to the alkylation reactor R101, and the isobutane and butene in the mixed C4 are alkylated in the reactor under the catalysis of 98% sulfuric acid to produce isooctane. The isooctane product is extracted from the lower end of the alkylation reactor R101 and sent to the debutanizer T101 for separation.

[0035] In debutanizer T101, the operating pressure at the top of the tower is 0.55MPa, the bottom temperature is 174.33℃, and the reflux ratio is 2. The normal butane in the isooctane product is separated as much as possible and sent to the subsequent process. According to the difference in boiling points between butane and isooctane products, the isooctane product is produced at the bottom of the debutanizer, and the normal butane content in the isooctane product is 1.05. High-purity isobutane is produced at the top of the tower, and normal isobutane and about 2.5% of C5 mixture are produced on the side of the debutanizer and sent to the maleic anhydride process butane separation tower T102 for further separation.

[0036] In the butane separation tower T102, the tower top operating pressure is 0.45MPa, the tower bottom temperature is 60℃, and the reflux ratio is 2.4. According to the difference in boiling points between n-isobutane and C5, the n-butane produced from the side of the butane separation T101 is sent to the maleic anhydride reactor R102 as the raw material of the maleic anhydride process. High-purity isobutane is produced from the top of the butane separation tower T102, mixed with the isobutane produced from the top of the debutanizer T101, part of which is returned to the alkylation reactor R101, and the other part is mixed with the isooctane product produced from the bottom of the debutanizer T101; isopentane is produced from the bottom of the butane separation tower T102.

[0037] Isopentane, isobutane and isooctane taken out from the bottom of debutanizer T101 are sent to SK+SV mixer M101 for mixing. C4 / C5 enters the mixer from the SK unit side. The SK unit improves the dispersion performance by adjusting the number of spiral sheets, welding angle and mixer length. The materials entering the mixer M101 are initially dispersed evenly, and then further dispersed and mixed through the corrugated plate filler of the SV unit to ensure the mixing uniformity of the isooctane product and C4 / C5, and the quality of the mixed isooctane product. The vapor pressure of the isooctane product after blending and mixing is 40-65kpa.

[0038] Comparative Example 1

[0039] The raw material mixed with C4 is sent to the alkylation reactor R101, and the isobutane and butene in the mixed C4 are alkylated in the reactor under the catalysis of 98% sulfuric acid to produce isooctane. The isooctane product is extracted from the lower end of the alkylation reactor R101 and sent to the debutanizer T101 for separation.

[0040] In the debutanizer T101, the operating pressure at the top of the tower is 0.55MPa, the temperature at the bottom of the tower is 152.84℃, and the reflux ratio is 2.4. According to the difference in boiling points between butane and isooctane products, high-purity isobutane is produced from the top of the tower, and isooctane products are produced from the bottom of the debutanizer. The content of normal butane in the isooctane product is 7.05%.

[0041] The comparison of process parameters and results between Comparative Example 1 and Example 1 is shown in Table 1.

[0042] Table 1

[0043] Serial number Key Parameters Example 1 Comparative Example 1 1 T101 tower top operating pressure (MPaG) 0.55 0.55 2 T101 tower bottom temperature (℃) 174.33 152.84 3 C5 content in T101 side-sampling mixed butane (wt%) 1.49 1.30 4 The content of n-butane in the isooctane product at the bottom of T101 tower (wt%) 1.05 7.05 5 Isobutane content of isooctane product at the bottom of T101 tower (wt%) 0 0.02 6 T101 tower top isobutane concentration (%) 89.47 91.18

[0044] It can be seen from Table 1 that the bottom operating temperature of debutanizer T101 is increased from 152.84℃ to 174.33℃. When other operating conditions remain unchanged, the n-butane content of the bottom product decreases from 7.05% to 1.05%, that is, 6% of the n-butane in the bottom isooctane product is recovered as raw material for maleic anhydride process.

[0045] Example 2

[0046] The raw material mixed with C4 is sent to the alkylation reactor R101, and the isobutane and butene in the mixed C4 are alkylated in the reactor under the catalysis of 98% sulfuric acid to produce isooctane. The isooctane product is extracted from the lower end of the alkylation reactor R101 and sent to the debutanizer T101 for separation.

[0047] In debutanizer T101, the top operating pressure is 0.5MPa, the bottom temperature is 160℃, and the reflux ratio is 2, so as to separate the normal butane from the isooctane product as much as possible and send it to the subsequent process. According to the difference in boiling points between butane and isooctane products, the isooctane product is produced at the bottom of the debutanizer, and the normal butane content in the isooctane product is 3%. High-purity isobutane is produced at the top of the tower, and normal isobutane and about 2.5% of C5 mixture are produced from the side of the debutanizer and sent to the maleic anhydride process butane separation tower T102 for further separation.

[0048] In the butane separation tower T102, the tower top operating pressure is 0.45MPa, the tower bottom temperature is 60℃, and the reflux ratio is 2.4. According to the difference in boiling points between n-isobutane and C5, the n-butane produced from the side of the butane separation T101 is sent to the maleic anhydride reactor R102 as the raw material of the maleic anhydride process. High-purity isobutane is produced from the top of the butane separation tower T102, mixed with the isobutane produced from the top of the debutanizer T101, part of which is returned to the alkylation reactor R101, and the other part is mixed with the isooctane product produced from the bottom of the debutanizer T101; isopentane is produced from the bottom of the butane separation tower T102.

[0049] Isopentane, isobutane and isooctane taken out from the bottom of debutanizer T101 are sent to SK+SV mixer M101 for mixing. C4 / C5 enters the mixer from the SK unit side. The SK unit improves the dispersion performance by adjusting the number of spiral sheets, welding angle and mixer length. The materials entering the mixer M101 are initially dispersed evenly, and then further dispersed and mixed through the corrugated plate filler of the SV unit to ensure the mixing uniformity of the isooctane product and C4 / C5 and the quality of the mixed isooctane product. The vapor pressure of the isooctane product after blending and mixing is 40-65KPa.

[0050] Example 3

[0051] The raw material mixed with C4 is sent to the alkylation reactor R101, and the isobutane and butene in the mixed C4 are alkylated in the reactor under the catalysis of 98% sulfuric acid to produce isooctane. The isooctane product is extracted from the lower end of the alkylation reactor R101 and sent to the debutanizer T101 for separation.

[0052] In debutanizer T101, the top operating pressure is 0.5MPa, the bottom temperature is 165℃, and the reflux ratio is 1.6, so as to separate the normal butane in the isooctane product as much as possible and send it to the subsequent process. According to the difference in boiling points between butane and isooctane products, the isooctane product is produced at the bottom of the debutanizer, and the normal butane content in the isooctane product is 2%. High-purity isobutane is produced at the top of the tower, and normal isobutane and about 5% of C5 mixture are produced on the side of the debutanizer, and sent to the maleic anhydride process butane separation tower T102 for further separation.

[0053] In the butane separation tower T102, the tower top operating pressure is 0.45MPa, the tower bottom temperature is 62°C, and the reflux ratio is 3.2. According to the difference in boiling points between n-isobutane and C5, the n-butane produced from the side of the butane separation tower T102 is sent to the maleic anhydride reactor R102 as the raw material for the maleic anhydride process. High-purity isobutane is produced from the top of the butane separation tower T102, mixed with the isobutane produced from the top of the debutanizer T101, part of which is returned to the alkylation reactor R101, and the other part is mixed with the isooctane product produced from the bottom of the debutanizer T101; isopentane is produced from the bottom of the butane separation tower T102.

[0054] Isopentane, isobutane and isooctane taken out from the bottom of debutanizer T101 are sent to SK+SV mixer M101 for mixing. C4 / C5 enters the mixer from the SK unit side. The SK unit improves the dispersion performance by adjusting the number of spiral sheets, welding angle and mixer length. The materials entering the mixer M101 are initially dispersed evenly, and then further dispersed and mixed through the corrugated plate filler of the SV unit to ensure the mixing uniformity of the isooctane product and C4 / C5 and the quality of the mixed isooctane product. The vapor pressure of the isooctane product after blending and mixing is 40-65KPa.

[0055] Example 4

[0056] The raw material mixed with C4 is sent to the alkylation reactor R101, and the isobutane and butene in the mixed C4 are alkylated in the reactor under the catalysis of 98% sulfuric acid to produce isooctane. The isooctane product is extracted from the lower end of the alkylation reactor R101 and sent to the debutanizer T101 for separation.

[0057] In debutanizer T101, the top operating pressure is 0.55MPa, the bottom temperature is 175℃, and the reflux ratio is 1.6, so as to separate the normal butane in the isooctane product as much as possible and send it to the subsequent process. According to the difference in boiling points between butane and isooctane products, the isooctane product is produced at the bottom of the debutanizer, and the normal butane content in the isooctane product is 1%. High-purity isobutane is produced at the top of the tower, and normal isobutane and about 3% of C5 mixture are produced on the side of the debutanizer, and sent to the maleic anhydride process butane separation tower T102 for further separation.

[0058] In the butane separation tower T102, the tower top operating pressure is 0.45MPa, the tower bottom temperature is 56°C, and the reflux ratio is 2. According to the difference in boiling points between n-isobutane and C5, the n-butane produced from the side of the butane separation T101 is sent to the maleic anhydride reactor R102 as the raw material for the maleic anhydride process. High-purity isobutane is produced from the top of the butane separation tower T102, mixed with the isobutane produced from the top of the debutanizer T101, part of which is returned to the alkylation reactor R101, and the other part is mixed with the isooctane product produced from the bottom of the debutanizer T101; isopentane is produced from the bottom of the butane separation tower T102.

[0059] Isopentane, isobutane and isooctane taken out from the bottom of debutanizer T101 are sent to SK+SV mixer M101 for mixing. C4 / C5 enters the mixer from the SK unit side. The SK unit improves the dispersion performance by adjusting the number of spiral sheets, welding angle and mixer length. The materials entering the mixer M101 are initially dispersed evenly, and then further dispersed and mixed through the corrugated plate filler of the SV unit to ensure the mixing uniformity of the isooctane product and C4 / C5 and the quality of the mixed isooctane product. The vapor pressure of the isooctane product after blending and mixing is 40-65KPa.

Claims

1. A method for recovering normal butane from isooctane oil as a raw material for producing maleic anhydride, comprising: the product after the alkylation reaction is fed into a debutanizer for separation, characterized in that: By increasing the operating temperature of the bottom of the debutanizer, the upper section of the debutanizer produces mixed butane and enters the butane separation tower for separation, and the lower section of the butane separation tower produces normal butane and is sent to the maleic anhydride reaction device; a part of the isobutane produced from the top of the butane separation tower is returned to the alkylation reactor, and the other part is mixed with the isooctane product produced from the bottom of the debutanizer; the isopentane produced from the bottom of the butane separation tower is mixed with the isooctane product produced from the bottom of the debutanizer; the material production line at the top of the debutanizer is returned to the alkylation reactor; a material mixer is provided at the bottom of the debutanizer, and the material mixer is used to evenly mix the isobutane produced from the top of the butane separation tower, the isooctane product produced from the bottom of the debutanizer, and the isopentane produced from the bottom of the butane separation tower; The debutanizer tower has a top operating pressure of 0.4-0.68 MPa and a bottom temperature of 165-200°C; The debutanizer reflux ratio is 1.6-2.4; The top operating pressure of the butane separation tower is controlled at 0.38-0.58 MPa, the bottom temperature is controlled at 50-70° C., and the reflux ratio is controlled at 2-3.

2.

2. A method for recovering normal butane from isooctane oil as a raw material for producing maleic anhydride as claimed in claim 1, characterized in that: The following device is used, including an alkylation reactor, a debutanizer, and a butane separation tower connected in sequence, wherein: The product after the reaction in the alkylation reactor enters the debutanizer through the material line; The upper material extraction line of the debutanizer is connected to the butane separation tower, and the bottom material extraction line is connected to the mixer; The bottom production line of the butane separation tower is connected to the mixer, the top production line is connected to the alkylation reactor and the mixer respectively, and the lower production line produces normal butane.

3. A method for recovering normal butane from isooctane oil as a raw material for producing maleic anhydride as claimed in claim 2, characterized in that: The mixer is an SV+SK type mixer, wherein the SV type unit is a cylinder assembled from corrugated plates of a certain specification, with a maximum dispersion degree of 1-2 μm, and liquid-liquid phase and gas-gas phase non-uniformity coefficients ≤1-5%; the SK type unit is welded from single-channel left and right twisted spiral sheets, and is used for small flow rates and high-viscosity media mixed with impurities or with a viscosity of ≤106 centipoise.

4. A method for recovering normal butane from isooctane oil as a raw material for producing maleic anhydride as claimed in claim 2, characterized in that: The lower section production line of the butane separation tower is connected to the maleic anhydride process.

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