Low temperature alkylation process and apparatus using isomeric c5 and c4 as feedstocks
By using low-temperature alkylation with isomeric C5 and isomeric C4 as raw materials, the problems of increased acid consumption and sulfur content in refinery alkylation units have been solved. By making reasonable use of the isomerization unit, the production of gasoline blending components has been increased, liquefied petroleum gas consumption has been reduced, and low-cost gasoline quality upgrades have been achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2023-11-10
- Publication Date
- 2026-05-12
AI Technical Summary
Existing refinery alkylation units suffer from increased acid consumption, higher dry point of alkylated oil products, and increased sulfur content. Furthermore, existing refining methods involve large equipment investments and high energy consumption, and the C4 and C5 isomerization units are not being utilized properly, resulting in idle units.
Using isomeric C5 and isomeric C4 as raw materials, the alkylation reaction is carried out at low temperature after isomerization of C4 and C5 olefins, combined with concentrated sulfuric acid catalysis, to separate isobutane, n-butane and alkylated gasoline. The C4 isomerization and C5 isomerization units are rationally utilized to reduce equipment idle time.
It effectively reduced the content of dimethyl ether and 1,3-butadiene, decreased acid consumption and sulfur content, increased the production of gasoline blending components, reduced liquefied petroleum gas components, improved the quality of alkylate products, and achieved low-cost gasoline quality upgrade.
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Figure CN119979217B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of gasoline processing technology, and is a low-temperature alkylation method and apparatus using isomeric C5 and isomeric C4 as raw materials. Background Technology
[0002] With the introduction of various domestic standards for upgrading oil products, such as China VI and Beijing VI, gasoline product standards are gradually moving towards higher octane ratings, lower aromatics, lower olefins, and lower sulfur content. The reduction in environmental indicators such as olefin content, aromatics content, and benzene content will make blending gasoline more challenging.
[0003] The existing C5 olefin resources in refineries are mainly incorporated into gasoline products through direct blending, which leads to the waste of low-carbon olefins. Furthermore, the C4 feedstock in the alkylation unit contains relatively low olefin content, with an average isobutane content of around 50%. The alkylation process results in an excess of isobutane, which is then dumped from the tank farm at a rate of 3 to 5 t / h. This excess isobutane accumulates over time and must be sold as inefficient liquefied petroleum gas (LPG).
[0004] The refinery currently uses post-etherified C5 and isomeric C5 feedstocks containing approximately 35% to 40% C4 and C5 olefins as olefin feedstocks for alkylation units. This increases the load on the alkylation units and consumes excess isobutane liquefied petroleum gas (LPG). Furthermore, the increased production of alkylated petroleum products yields better octane ratings and blending properties than directly blending C5 olefins into gasoline. Alkylation of C5 olefins not only increases gasoline production and reduces LPG consumption but also lowers the olefin content of gasoline.
[0005] By changing the process, the industrial feedstock for alkylation units has been broadened, providing a low-cost technological route for upgrading the quality of gasoline products in refineries.
[0006] Since the alkylation unit began operation, the feedstock has exhibited excessively high levels of impurities such as dimethyl ether and dibutene, leading to increased acid consumption, higher dry point of alkylate products, and increased sulfur content. This severely impacts the high-load operation of the alkylation unit and restricts the processing of C5 olefin feedstock, hindering the full realization of the advantages of alkylation processing in increasing gasoline production and reducing gasoline olefin content. Therefore, it is crucial that the dimethyl ether and 1,3-butadiene from isomeric C4 and C5 olefins be kept at low levels after the isomerization unit. Consequently, there is an urgent need to optimize and improve the reaction feedstock of the alkylation unit to address the issues of increased acid consumption, higher dry point of alkylate products, and increased sulfur content in the alkylation process.
[0007] Chinese patent document CN105601460A discloses a method for refining alkylation feedstock. The method involves passing alkylation feedstock containing impurities through a water washing tower, dehydration tower, desulfurization tower, dechlorination tower, denitrification tower, deoxygenation and compound removal tower, preheater, and selective hydrogenation reactor to obtain refined alkylation feedstock. This method effectively removes impurities from the alkylation feedstock, significantly reducing the impurity content and preventing poisoning of the solid acid catalyst in subsequent alkylation reactions, thus improving the catalytic activity and lifespan of the alkylation solid acid catalyst. However, this method has the following drawbacks: (1) It requires eight additional towers and one hydrogenation reactor, resulting in a significant increase in equipment, high investment, and high energy consumption; (2) The C4 and C5 isomerization units are not utilized effectively, leading to idle equipment; (3) The patent uses a hydrogenation reactor, requiring the provision of new hydrogen resources, increasing feedstock costs. Summary of the Invention
[0008] This invention provides a low-temperature alkylation method and apparatus using isomeric C5 and isomeric C4 as raw materials, which overcomes the shortcomings of the prior art and can effectively solve the problems of increased acid consumption, increased dry point of alkylated oil products and increased sulfur content in existing alkylation processes.
[0009] One of the technical solutions of this invention is achieved through the following measures: a low-temperature alkylation method using isomeric C5 and isomeric C4 as raw materials, which is carried out according to the following steps:
[0010] In the first step, the C4 etherified carbon enters the C4 isomerization unit to undergo a C4 olefin isomerization reaction, yielding isomerized C4.
[0011] The second step involves the etherified C5 entering the C5 isomerization unit to undergo a C5 olefin isomerization reaction, yielding isomerized C5.
[0012] In the third step, the isomeric C4 and isomeric C5 are mixed and then fed into a low-temperature alkylation reaction unit. Under the catalysis of concentrated sulfuric acid, an alkylation reaction occurs, and the reaction products are separated to obtain isobutane, n-butane, and alkylated gasoline.
[0013] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions:
[0014] In the first step above, the process conditions for the C4 olefin isomerization reaction are: reaction temperature of 330℃ and reaction pressure of 0.3MPa.
[0015] In the second step above, the process conditions for the C5 olefin isomerization reaction are: reaction temperature of 335℃ and reaction pressure of 0.3MPa.
[0016] In the third step above, the feed ratio of isomeric C4 and isomeric C5 is 20:1 to 5.
[0017] In the third step above, the reaction temperature for the alkylation reaction is -4°C to 4°C.
[0018] In the third step above, during the alkylation reaction, the acid-to-hydrocarbon ratio is 2.0 to 3.5:1, and the concentration of concentrated sulfuric acid in the reaction cycle is maintained at no less than 90%.
[0019] In the third step above, the separated isobutane is returned to the low-temperature alkylation reaction unit for recycling as a coolant.
[0020] The second technical solution of the present invention is achieved through the following measures: a low-temperature alkylation device using isomeric C5 and isomeric C4 as raw materials, comprising a C4 isomerization unit, a C5 isomerization unit, a low-temperature alkylation reaction unit, and a distillation unit. The feed end of the C4 isomerization unit is fixedly connected to a post-etherified C4 feed line, the feed end of the C5 isomerization unit is fixedly connected to a post-etherified C5 feed line, the discharge end of the C4 isomerization unit is fixedly connected to the feed end of the low-temperature alkylation reaction unit via a first alkylation feed line, the discharge end of the C5 isomerization unit is fixedly connected to the first alkylation feed line via a second alkylation feed line, the discharge end of the low-temperature alkylation reaction unit is fixedly connected to the feed end of the distillation unit via a distillation line, the first discharge end of the distillation unit is fixedly connected to an isobutane line, the second discharge end of the distillation unit is fixedly connected to an n-butane line, and the first discharge end of the distillation unit is fixedly connected to an alkylated gasoline line.
[0021] The following are further optimizations and / or improvements to the second technical solution of the above invention:
[0022] A reflux line is fixedly connected between the aforementioned isobutane line and the first alkylation feed line between the second alkylation feed line and the low-temperature alkylation reaction unit.
[0023] This invention effectively solves the problems of increased acid consumption, increased dry point of alkylated oil products, and increased sulfur content in the alkylation process. It realizes the rational utilization of C4 and C5 isomerization units, reduces equipment idleness, and provides high-quality raw materials for alkylation while increasing the production of MTBE and etherified gasoline, achieving multiple benefits and is an effective means of improving quality and efficiency. Attached Figure Description
[0024] Appendix Figure 1 This is a schematic diagram of the process flow of Embodiment 10 of the present invention.
[0025] The codes in the attached diagram are as follows: 1 is the C4 isomerization unit, 2 is the C5 isomerization unit, 3 is the low-temperature alkylation reaction unit, 4 is the distillation unit, 5 is the post-etherification C4 feed line, 6 is the post-etherification C5 feed line, 7 is the first alkylation feed line, 8 is the second alkylation feed line, 9 is the distillation line, 10 isobutane line, 11 isobutane line, 12 isobutane gasoline line, and 13 is the reflux line. Detailed Implementation
[0026] This invention is not limited to the following embodiments; specific implementation methods can be determined according to the technical solution of this invention and actual circumstances. Unless otherwise specified, all chemical reagents and chemical products mentioned in this invention are well-known and commonly used chemical reagents and chemical products in the prior art; unless otherwise specified, all percentages in this invention are mass percentages. Unless otherwise specified, all equipment and apparatus used in this invention are well-known and commonly used equipment and apparatus in the art.
[0027] The present invention will be further described below with reference to embodiments:
[0028] Example 1: As Figure 1 As shown, the low-temperature alkylation method using isomeric C5 and isomeric C4 as raw materials is carried out according to the following steps:
[0029] In the first step, the C4 etherified carbon enters the C4 isomerization unit 1 to undergo a C4 olefin isomerization reaction, yielding isomerized C4.
[0030] In the second step, the C5 etherified carbon enters C5 isomerization unit 2 to undergo C5 olefin isomerization reaction, yielding isomerized C5;
[0031] In the third step, the isomeric C4 and isomeric C5 are mixed and then fed into the low-temperature alkylation reaction unit 3. Under the catalysis of concentrated sulfuric acid, an alkylation reaction occurs, and the reaction products are separated to obtain isobutane, n-butane and alkylated gasoline.
[0032] Example 2: As an optimization of the above example, in the first step, the process conditions for the C4 olefin isomerization reaction are: reaction temperature of 330°C and reaction pressure of 0.3 MPa (G).
[0033] Example 3: As an optimization of the above example, in the second step, the process conditions for the C5 olefin isomerization reaction are: reaction temperature of 335°C and reaction pressure of 0.3 MPa (G).
[0034] Example 4: As an optimization of the above example, in the third step, the feed ratio of isomeric C4 and isomeric C5 is 20:1 to 5.
[0035] Example 5: As an optimization of the above example, in the third step, the reaction temperature of the alkylation reaction is -4°C to 4°C.
[0036] Example 6: As an optimization of the above example, in the third step, the acid-to-hydrocarbon ratio in the alkylation reaction is 2.0 to 3.5:1, and the mass concentration of concentrated sulfuric acid in the reaction cycle is maintained at no less than 90% (i.e., the water and hydrocarbon content shall not exceed 10%).
[0037] Example 7: As an optimization of the above example, in the third step, the separated isobutane is returned to the low-temperature alkylation reaction unit as a refrigerant for recycling 3.
[0038] Example 8: As Figure 1 As shown, the low-temperature alkylation device using isomeric C5 and isomeric C4 as raw materials includes a C4 isomerization unit 1, a C5 isomerization unit 2, a low-temperature alkylation reaction unit 3, and a distillation unit 4. The feed end of the C4 isomerization unit 1 is fixedly connected to a post-etherified C4 feed line 5. The feed end of the C5 isomerization unit 2 is fixedly connected to a post-etherified C5 feed line 6. The discharge end of the C4 isomerization unit 1 and the feed end of the low-temperature alkylation reaction unit 3 are fixedly connected to a first alkylation feed line 7. The discharge end of the C5 isomerization unit 2 and the first alkylation feed line 7 are fixedly connected to a second alkylation feed line 8. The discharge end of the low-temperature alkylation reaction unit 3 and the feed end of the distillation unit 4 are fixedly connected to a distillation line 9. The first discharge end of the distillation unit 4 is fixedly connected to an isobutane line 10. The second discharge end of the distillation unit 4 is fixedly connected to a n-butane line 11. The first discharge end of the distillation unit 4 is fixedly connected to an alkylated gasoline line 12.
[0039] Example 9: As Figure 1 As shown, as an optimization of the above embodiment, a reflux line 13 is fixedly connected between the isobutane line 10, the second alkylation feed line 8, and the first alkylation feed line 7 between the low-temperature alkylation reaction unit 3.
[0040] As required, valves and instruments that enable the low-temperature alkylation device using isomeric C5 and isomeric C4 as raw materials are fixedly installed on each pipeline to ensure its normal operation. The C4 isomerization unit 1, C5 isomerization unit 2, low-temperature alkylation reaction unit 3 and distillation unit 4 all use existing reactors and equipment.
[0041] Depending on the requirements, the isomerization reaction of post-etherified C4 and post-etherified C5 olefins is carried out in the presence of an isomerization catalyst, which can be a conventional isomerization catalyst.
[0042] This invention provides a method and apparatus for low-temperature alkylation using isomeric C5 and isomeric C4 as raw materials. The method uses post-etherified C4 and post-etherified C5 as raw materials to undergo olefin isomerization reactions to obtain isomeric C4 and isomeric C5, respectively. The isomeric C4 and isomeric C5 are then fed into a low-temperature alkylation reaction unit 3 for reaction, and the reaction products are sent to a distillation unit 4 to be separated into n-butane, isobutane, and alkylated gasoline. Through the above process, the dimethyl ether and 1,3-butadiene content in the post-etherified C4 and post-etherified C5 are significantly reduced, and acid consumption, the dry point of the alkylated oil product, and sulfur content are all reduced. In this process, the C5 olefins in the isomeric C5 undergo a low-temperature alkylation reaction with the isobutane in the isomeric C4, which not only increases the production of gasoline blending components and reduces liquefied petroleum gas components, but also reduces the olefin content in the gasoline blending tank. This invention achieves the rational utilization of C4 isomerization unit 1 and C5 isomerization unit 2, reducing equipment idle time. When realizing olefin isomerization, C4 isomerization unit 1 and C5 isomerization unit 2 can decompose dimethyl ether in the feedstock, thereby increasing the production of MTBE and etherified gasoline while providing high-quality feedstock for alkylation, achieving multiple benefits in one go. It is an effective means of improving quality and efficiency.
[0043] Example 10: The low-temperature alkylation method using isomeric C5 and isomeric C4 as raw materials is carried out according to the following steps:
[0044] In the first step, the C4 etherified material enters C4 isomerization unit 1 for a C4 olefin isomerization reaction at 330°C and 0.3 MPa, yielding isomeric C4. The product isomeric C4 contains 24 mg / kg of dimethyl ether and 60 mL / m³ of 1,3-butadiene. 3 .
[0045] In the second step, the C5 etherified carbon enters C5 isomerization unit 2 for C5 olefin isomerization reaction at a temperature of 335℃ and a pressure of 0.3 MPa (G), yielding isomerized C5. The product isomerized C5 contains 0 mg / kg of dimethyl ether and 20 mL / m³ of 1,3-butadiene. 3 .
[0046] In the third step, 20 t / h of isomeric C4 feed and 3 t / h of isomeric C5 feed are mixed and then fed into low-temperature alkylation reaction unit 3, where alkylation occurs under the catalysis of concentrated sulfuric acid. The alkylation reaction temperature range is -4℃ to 4℃, the acid-to-hydrocarbon ratio is 2.5:1, and the reaction products are separated to obtain isobutane, n-butane, and alkylated gasoline. In this example, the conversion rate of the C5 olefin alkylation reaction is 98%, the product yield is 63%, the alkylation research octane number is 96, and the acid consumption is 115 kg / ton of alkylated gasoline.
[0047] Example 11: The low-temperature alkylation method using isomeric C5 and isomeric C4 as raw materials is carried out according to the following steps:
[0048] In the first step, the C4 etherified material enters C4 isomerization unit 1 for a C4 olefin isomerization reaction at 330°C and 0.3 MPa, yielding isomeric C4. The product isomeric C4 contains 24 mg / kg of dimethyl ether and 60 mL / m³ of 1,3-butadiene. 3 .
[0049] In the second step, the C5 etherified carbon enters C5 isomerization unit 2 for C5 olefin isomerization reaction at a temperature of 335℃ and a pressure of 0.3 MPa (G), yielding isomerized C5. The product isomerized C5 contains 0 mg / kg of dimethyl ether and 20 mL / m³ of 1,3-butadiene. 3 .
[0050] In the third step, 20 t / h of isomeric C4 feed and 1.5 t / h of isomeric C5 feed are mixed and then fed into low-temperature alkylation reaction unit 3. Under the catalysis of concentrated sulfuric acid, alkylation occurs. The alkylation reaction temperature range is -4℃ to 4℃, the acid-to-hydrocarbon ratio is 2:1, and the reaction products are separated to obtain isobutane, n-butane, and alkylated gasoline. In this example, the conversion rate of the C5 olefin alkylation reaction is 98%, the product yield is 63%, the alkylation research octane number is 96.5, and the acid consumption is 110 kg / ton of alkylated gasoline.
[0051] Example 12: The low-temperature alkylation method using isomeric C5 and isomeric C4 as raw materials is carried out according to the following steps:
[0052] In the first step, the C4 etherified material enters C4 isomerization unit 1 for a C4 olefin isomerization reaction at 330°C and 0.3 MPa, yielding isomeric C4. The product isomeric C4 contains 24 mg / kg of dimethyl ether and 60 mL / m³ of 1,3-butadiene. 3 .
[0053] In the second step, the C5 etherified carbon enters C5 isomerization unit 2 for C5 olefin isomerization reaction at a temperature of 335℃ and a pressure of 0.3 MPa (G), yielding isomerized C5. The product isomerized C5 contains 0 mg / kg of dimethyl ether and 20 mL / m³ of 1,3-butadiene. 3 .
[0054] In the third step, 20 t / h of isomeric C4 feed and 5 t / h of isomeric C5 feed are mixed and then fed into low-temperature alkylation reaction unit 3, where alkylation occurs under the catalysis of concentrated sulfuric acid. The alkylation reaction temperature range is -4℃ to 4℃, the acid-to-hydrocarbon ratio is 3:1, and the reaction products are separated to obtain isobutane, n-butane, and alkylated gasoline. In this example, the conversion rate of the C5 olefin alkylation reaction is 98%, the product yield is 63%, the alkylation research octane number is 95.6, and the acid consumption is 118 kg / ton of alkylated gasoline.
[0055] Comparative example: The method of directly mixing post-etherified C4 and post-etherified C5 and then subjecting them to low-temperature alkylation was adopted. The specific steps are as follows:
[0056] The post-etherified C4 and post-etherified C5 are directly mixed and fed into low-temperature alkylation reaction unit 3, with a feed rate of 23 t / h for post-etherified C4 and 1.5 t / h for post-etherified C5. Alkylation occurs under the catalysis of concentrated sulfuric acid. The alkylation reaction temperature range is -4℃ to 4℃, with an acid-to-hydrocarbon ratio of 3:1. Alkylated gasoline is obtained after the reaction. The conversion rate of C5 olefins in the alkylation reaction is 96%, the alkylation research octane number is 95.0, and the acid consumption is 132 kg / ton of alkylated gasoline.
[0057] After implementing the low-temperature alkylation method using isomeric C5 and isomeric C4 as raw materials, the levels of dimethyl ether and 1,3-butadiene in the post-etherified C4 and C5 are significantly reduced, effectively solving problems such as increased acid consumption, higher dry point of alkylate oil products, and increased sulfur content. Under isobutane surplus conditions, the olefin content in the C5 olefin feedstock is between 35% and 40%. For every ton of C5 olefin feedstock processed, approximately 0.38 tons of isobutane are consumed, increasing the production of alkylate oil by 0.72 tons (excluding unreacted C5 alkanes). The C5 olefins in the unit complete the alkylation reaction under low-temperature sulfuric acid catalysis, making rational use of isobutane resources, converting inefficient liquefied petroleum gas into efficient alkylate oil, increasing the yield of alkylate oil products, and forming a low-cost process technology route for upgrading the quality of China VI B gasoline.
[0058] In summary, the low-temperature alkylation method of the present invention using isomeric C5 and isomeric C4 as raw materials effectively reduces the dimethyl ether and 1,3-butadiene in post-etherified C4 and post-etherified C5, effectively solving problems such as increased acid consumption, increased dry point of alkylated oil products, and increased sulfur content. It not only increases the production of gasoline blending components and reduces liquefied petroleum gas components, but also reduces the olefin content in the gasoline blending pool. While increasing the production of MTBE and etherified gasoline, it provides high-quality raw materials for alkylation, achieving multiple benefits and is an effective means of improving quality and efficiency.
[0059] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.
Claims
1. A low-temperature alkylation method using isomeric C5 and isomeric C4 as raw materials, characterized in that... Follow these steps: In the first step, the C4 etherified carbon enters the C4 isomerization unit to undergo a C4 olefin isomerization reaction, yielding isomerized C4. The second step involves the etherified C5 entering the C5 isomerization unit to undergo a C5 olefin isomerization reaction, yielding isomerized C5. The third step involves mixing isomeric C4 and isomeric C5 and then entering a low-temperature alkylation reaction unit. Under the catalysis of concentrated sulfuric acid, an alkylation reaction occurs, and the reaction products are separated to obtain isobutane, n-butane, and alkylated gasoline. In the first step, the process conditions for the isomerization reaction of C4 olefins are: reaction temperature of 330℃ and reaction pressure of 0.3MPa; In the second step, the process conditions for the C5 olefin isomerization reaction are: reaction temperature of 335℃ and reaction pressure of 0.3MPa. In the third step, the feed ratio of isomeric C4 and isomeric C5 is 20:(1~5), and the reaction temperature of the alkylation reaction is -4℃ to 4℃.
2. The low-temperature alkylation method using isomeric C5 and isomeric C4 as raw materials according to claim 1, characterized in that... In the third step, during the alkylation reaction, the acid-to-hydrocarbon ratio is (2.0~3.5):1, and the concentration of concentrated sulfuric acid in the reaction cycle is maintained at no less than 90%.
3. The low-temperature alkylation method using isomeric C5 and isomeric C4 as raw materials according to claim 2, characterized in that... In the third step, the separated isobutane is returned to the low-temperature alkylation reaction unit as a refrigerant for recycling.
4. A low-temperature alkylation apparatus for implementing the method according to any one of claims 1 to 3, using isomeric C5 and isomeric C4 as raw materials, characterized in that... It includes a C4 isomerization unit, a C5 isomerization unit, a low-temperature alkylation reaction unit, and a distillation unit. The feed end of the C4 isomerization unit is fixedly connected to a post-etherification C4 feed line, the feed end of the C5 isomerization unit is fixedly connected to a post-etherification C5 feed line, the discharge end of the C4 isomerization unit is fixedly connected to the feed end of the low-temperature alkylation reaction unit by a first alkylation feed line, the discharge end of the C5 isomerization unit is fixedly connected to the first alkylation feed line by a second alkylation feed line, the discharge end of the low-temperature alkylation reaction unit is fixedly connected to the feed end of the distillation unit by a distillation line, the first discharge end of the distillation unit is fixedly connected to an isobutane line, the second discharge end of the distillation unit is fixedly connected to an n-butane line, and the first discharge end of the distillation unit is fixedly connected to an alkylated gasoline line.
5. The low-temperature alkylation apparatus using isomeric C5 and isomeric C4 as raw materials according to claim 4, characterized in that... A reflux line is fixedly connected between the isobutane line, the second alkylation feed line, and the first alkylation feed line between the low-temperature alkylation reaction unit.