Device and process for continuously preparing isooctyl nitrate

Abstract

The device comprises a continuous feeding system, a spiral static mixer, a tubular reactor and a neutralization and separation system, the front end of the spiral static mixer is connected with the continuous feeding system, the rear end of the spiral static mixer is connected with a feeding port of the tubular reactor, and the tubular reactor is connected with the neutralization and separation system. And a discharge hole of the tubular reactor is connected with the neutralization and separation system. An SK type static mixing element is arranged in the front 50m of the tubular reactor, and an SV type static mixing element is arranged in the rear 20m of the tubular reactor, so that a micro-channel through which a reaction liquid flows and reacts is formed. The process is used for preparing the isooctyl nitrate through the mixed acid method, no additional organic solvent needs to be added, the requirement for the concentration of sulfuric acid and nitric acid is not too high, 65% nitric acid and 90% sulfuric acid can be used, the reaction is efficient and safe, follow-up treatment is simple, and the process is suitable for continuous production.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of isooctyl nitrate, and particularly relates to a device and a process for continuously preparing isooctyl nitrate. Background Art

[0002] Isooctyl nitrate (2-ethylhexyl nitrate) is an important cetane number improver that can significantly improve diesel combustion efficiency. Its traditional preparation method uses a mixed acid esterification method with a kettle reaction, in which isooctyl alcohol and concentrated nitric acid are esterified in the presence of excess concentrated sulfuric acid [Gao Hongshun et al., ZL 90105260.4; Liao Weilin et al., CN201610694917.5. ], which has the following defects: 1. Low mass and heat transfer efficiency. The kettle reaction relies on mechanical stirring, uneven mixing, and is prone to local overheating, which can trigger side reactions (such as oxidation and decomposition) and reduce product purity; 2. Poor safety. The reaction is highly exothermic, and it is difficult to accurately control the temperature during intermittent operation, which poses a risk of explosion. In order to avoid the use of excessive concentrated sulfuric acid, a synthesis technology of strong acid cation exchange resin as solid acid instead of concentrated sulfuric acid has also emerged [Fu Haiming, CN 201611179098.7; Zhang Lei et al., CN201810033847.8], but the solid acid needs to be separated, regenerated, and recycled, which limits its application. In recent years, the application of microchannel reactors in the preparation of isooctyl nitrate by mixed acid esterification has been widely recognized [Zhu Hongwei, Sun Bing, Zhao Lei, Liu Yujia, Wang Shiqiang, Xu Wei, CN 116283589 A; Chen Guangwen, Shen Jiani, Jiao Fengjun, Zhao Yuchao, Yuan Quan. CN 101462962B; Li Bindong, Liu Jianhua, Hu Yongke, Chen Lei, Chang Ting, CN 105330549A; Ma Bing, Shen Wei, Wang Yanhua, Zhang Mo, CN 113105333 A. ]. The microchannel preparation method is safe and efficient, but the manufacturing of its reactor is complex, demanding, and costly. Even 98% concentrated nitric acid needs to be used [Yin Fanghua, Yang Yan, Xu Ran, Li Xiaofang, CN 103980125A]. Therefore, developing a safe, efficient, and continuous production process and device still has important application value. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides a device and a process for continuously preparing isooctyl nitrate. The process is used for preparing isooctyl nitrate by a mixed acid method, does not require the addition of an organic solvent, has no excessively high requirements on the concentrations of sulfuric acid and nitric acid, and 65% nitric acid and 90% sulfuric acid can be used. The reaction is efficient and safe, and the subsequent treatment is simple, which is suitable for continuous production.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A device for continuously preparing isooctyl nitrate comprises a continuous feeding system, a spiral static mixer, a tubular reactor, and a neutralization and separation system. The front end of the spiral static mixer is connected to the continuous feeding system, the rear end of the spiral static mixer is connected to the feeding port of the tubular reactor, and the discharge port of the tubular reactor is connected to the neutralization and separation system.

[0006] Furthermore, the main body of the tubular reactor is a DN25×70m double-layer 316L stainless steel pipe with a built-in static mixing element.

[0007] Furthermore, an SK type static mixing element is installed in the first 50m of the tubular reactor, and an SV type static mixing element is installed in the last 20m of the tubular reactor to form a microchannel for the reaction liquid to flow through and react. Mass transfer and heat transfer are enhanced through the microstructure mixing unit, and the reaction rate is increased by more than 40%; the interlayer circulating water system is used for temperature control.

[0008] Furthermore, the front end of the tubular reactor is connected to the spiral static mixer, and the rear end is connected to the neutralization and separation system. The inner diameter length of the tubular reactor can be adjusted according to the designed output. The larger the designed output, the larger the corresponding inner diameter length.

[0009] Furthermore, the static mixing element is made of ceramic or stainless steel, a common model, preferably stainless steel X-type stainless steel.

[0010] Furthermore, the continuous feeding system is composed of an isooctyl alcohol metering tank, a nitric acid metering tank, a sulfuric acid metering tank and three high-precision metering pumps. The high-precision metering pumps respectively meter the isooctyl alcohol, nitric acid and sulfuric acid in proportion and transport them into the spiral static mixer.

[0011] Furthermore, the neutralization and separation system includes a cooling tank, a neutralization water washing tank, and a dehydrator. The cooling tank is connected to the neutralization water washing tank, the neutralization water washing tank is connected to the dehydrator, and the dehydrator is connected to the finished product tank. The reaction liquid that flows through the tubular reactor and completes the reaction enters the neutralization and separation system, and undergoes layered acid removal, alkali solution neutralization, water washing, and freezing purification operations to obtain the product.

[0012] Furthermore, the waste acid after stratification in the cooling tank enters the waste acid receiving transfer tank for storage.

[0013] The present invention also provides a process for continuously preparing isooctyl nitrate using the device, the specific steps of which are:

[0014] The raw materials of isooctyl alcohol, nitric acid and sulfuric acid are respectively pumped into the spiral static mixer by three high-precision metering pumps, and then enter the tubular reactor after being mixed by the spiral static mixer, so that the isooctyl alcohol and nitric acid react continuously in the presence of sulfuric acid, and the reaction liquid is neutralized online, separated and purified to obtain the product isooctyl nitrate.

[0015] Furthermore, the temperature of the continuous reaction is 30-60° C., preferably 35° C. The retention time of the reaction solution in the tubular reactor is the residence time of the three raw materials after entering the tubular reactor through the static mixer, which is 1-30 minutes.

[0016] Furthermore, the raw materials isooctyl alcohol, nitric acid and sulfuric acid are all commercially available chemical products, the purity of isooctyl alcohol is greater than 99%, the concentration of nitric acid is 65-98%, and the concentration of sulfuric acid is 90-98%.

[0017] Furthermore, the molar ratio of the raw materials isooctyl alcohol, nitric acid and sulfuric acid is 1:1:1.5 to 1:1.1:2.3.

[0018] After the synthesis reaction in the present invention is completed, the post-treatment process is not particularly limited, and the product separation and purification can be carried out by the following method: after the reaction is completed, the waste acid is separated by cooling and stratification, and the residual acid is neutralized with alkali solution to remove the residual acid, and then washed with water to obtain the product.

[0019] Beneficial effects of the present invention: The present invention proposes a device and process for continuously preparing isooctyl nitrate, which is used for preparing isooctyl nitrate by mixed acid method, without adding organic solvent, and without excessively high requirements for the concentration of sulfuric acid and nitric acid, 65% nitric acid and 90% sulfuric acid can be used; the tubular reactor body of the continuous production device based on the tubular reactor of the present invention is a double-layer 316L stainless steel pipe of DN25×70m, the first 50m of which is equipped with SK type static mixing elements, and the rear 20m is equipped with SV type static mixing elements to form a microchannel for the reaction liquid to flow through and react, and the mass transfer and heat transfer are enhanced by the microstructure mixing unit, and the reaction rate is increased by more than 40%; the interlayer circulating water system is used for temperature control. The inner diameter length of the tubular reactor can be adjusted according to the designed output. The larger the designed output, the larger the corresponding inner diameter length. The device and process of the present invention are efficient and safe, and the subsequent treatment is simple, which is suitable for continuous production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 The present invention is a schematic diagram of the structure of the device for continuously preparing isooctyl nitrate. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1

[0024] like Figure 1 As shown, the device for continuously preparing isooctyl nitrate of this embodiment includes a continuous feeding system, a spiral static mixer, a tubular reactor, and a neutralization and separation system. The front end of the spiral static mixer is connected to the continuous feeding system, the rear end of the spiral static mixer is connected to the feed port of the tubular reactor, and the discharge port of the tubular reactor is connected to the neutralization and separation system.

[0025] The main body of the tubular reactor is a DN25×70m double-layer 316L stainless steel tube with a built-in static mixing element. Specifically, the first 50m of the tubular reactor is equipped with an SK-type static mixing element, and the last 20m of the tubular reactor is equipped with an SV-type static mixing element to form a microchannel for the reaction liquid to flow through and react. The microstructure mixing unit is used to enhance mass transfer and heat transfer, and the reaction rate is increased by more than 40%. The static mixing element is made of ceramic or stainless steel, a general model, preferably stainless steel X-type stainless steel. The interlayer circulating water system is used for temperature control.

[0026] The front end of the tubular reactor is connected to the spiral static mixer, and the rear end is connected to the neutralization and separation system. The inner diameter length of the tubular reactor can be adjusted according to the designed output. The larger the designed output, the larger the corresponding inner diameter length.

[0027] The continuous feeding system consists of an isooctyl alcohol metering tank, a nitric acid metering tank, a sulfuric acid metering tank and three high-precision metering pumps. The high-precision metering pumps respectively meter the isooctyl alcohol, nitric acid and sulfuric acid in proportion and transport them into the spiral static mixer. The neutralization and separation system includes a cooling tank, a neutralization water washing tank and a dehydrator. The cooling tank is connected to the neutralization water washing tank, the neutralization water washing tank is connected to the dehydrator, and the dehydrator is connected to the finished product tank. The reaction liquid that flows through the tubular reactor and completes the reaction enters the neutralization and separation system, and undergoes stratified acid removal, alkali solution neutralization, water washing, and freezing purification operations to obtain the product. Furthermore, the waste acid after stratification in the cooling tank enters the waste acid receiving transfer tank for storage.

[0028] Example 2

[0029] The process for continuously preparing isooctyl nitrate using the device of Example 1 is as follows:

[0030] In a reaction device of a tubular reactor (DN25×70m) whose main body is a built-in static mixing element (50m SK and 20m SV), isooctyl alcohol, 98% nitric acid and 98% sulfuric acid are continuously input into a spiral static mixer in a molar ratio of 1:1:1.5 through high-precision metering pumps, respectively, and enter into a tubular reactor after being mixed by the spiral static mixer. The reaction temperature is controlled at 30°C by jacket circulating water, and the flow rate is adjusted to control the retention time for 1 minute; after the reaction is completed in the tubular reactor, the reaction liquid enters a neutralization and separation system, cools and stands for 0.5h, and releases waste acid after phase separation; sodium carbonate solution is added to neutralize to pH=8; the oil layer is then washed with water to pH=7; and the product isooctyl nitrate is obtained through freezing purification, with a purity of ≥99.8% (GC detection) and a yield of ≥99.4%. The production capacity of a single set of equipment can reach 3,000 tons / year.

[0031] Example 3

[0032] The process for continuously preparing isooctyl nitrate using the device of Example 1 is as follows:

[0033] In a reaction device of a tubular reactor (DN25×70m) whose main body is a built-in static mixing element (50m SK and 20m SV), isooctyl alcohol, 65% nitric acid and 98% sulfuric acid are continuously input into a spiral static mixer at a molar ratio of 1:1.1:1.8 through high-precision metering pumps, respectively, and enter into a tubular reactor after being mixed by the spiral static mixer. The reaction temperature is controlled at 45°C by jacket circulating water, and the flow rate is adjusted to control the retention time of 15 minutes; after the reaction is completed in the tubular reactor, the reaction liquid enters a neutralization and separation system, cools and stands for 0.5h, and releases waste acid after phase separation; sodium carbonate solution is added to neutralize to pH=8; the oil layer is then washed with water to pH=7; and the product isooctyl nitrate is obtained through freezing purification, with a purity of ≥99.5% (GC detection) and a yield of ≥99.3%. The production capacity of a single set of equipment can reach 2,000 tons / year.

[0034] Example 4

[0035] The process for continuously preparing isooctyl nitrate using the device of Example 1 is as follows:

[0036] In a reaction device of a tubular reactor (DN25×70m) whose main body is a built-in static mixing element (50m SK and 20m SV), isooctyl alcohol, 65% nitric acid and 93% sulfuric acid are continuously input into a spiral static mixer in a molar ratio of 1:1.1:2 through high-precision metering pumps, respectively, and enter into a tubular reactor after being mixed by the spiral static mixer. The reaction temperature is controlled at 60°C by jacket circulating water, and the flow rate is adjusted to control the retention time for 20 minutes; after the reaction is completed in the tubular reactor, the reaction liquid enters a neutralization and separation system, cools and stands for 0.5h, and releases waste acid after phase separation; sodium carbonate solution is added to neutralize to pH=8; the oil layer is then washed with water to pH=7; the product isooctyl nitrate is obtained by freeze purification and drying, with a purity of ≥99.4% (GC detection) and a yield of ≥99%, and the production capacity of a single set of equipment can reach 1,800 tons / year.

[0037] Example 5

[0038] The process for continuously preparing isooctyl nitrate using the device of Example 1 is as follows:

[0039] In a reaction device of a tubular reactor (DN25×70m) whose main body is a built-in static mixing element (50m SK and 20m SV), isooctyl alcohol, 65% nitric acid and 90% sulfuric acid are continuously input into a spiral static mixer in a molar ratio of 1:1.1:2.3 through high-precision metering pumps, respectively, and enter into a tubular reactor after being mixed by the spiral static mixer. The reaction temperature is controlled at 60°C by jacket circulating water, and the flow rate is adjusted to control the retention time for 30 minutes; after the reaction is completed in the tubular reactor, the reaction liquid enters a neutralization and separation system, cools and stands for 0.5h, and releases waste acid after phase separation; sodium carbonate solution is added to neutralize to pH=8; the oil layer is then washed with water to pH=7; the product isooctyl nitrate is obtained by freeze purification and drying, with a purity of ≥99.4% (GC detection) and a yield of ≥99%, and the production capacity of a single set of equipment can reach 1500 tons / year.

[0040] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A device for continuously preparing isooctyl nitrate, characterized in that: The invention comprises a continuous feeding system, a spiral static mixer, a tubular reactor, and a neutralization and separation system. The front end of the spiral static mixer is connected to the continuous feeding system, the rear end of the spiral static mixer is connected to the feeding port of the tubular reactor, and the discharging port of the tubular reactor is connected to the neutralization and separation system.

2. The device for continuously preparing isooctyl nitrate according to claim 1, characterized in that: The main body of the tubular reactor is a DN25×70m double-layer 316L stainless steel pipe with a built-in static mixing element.

3. The device for continuously preparing isooctyl nitrate according to claim 2, characterized in that: The first 50 m of the tubular reactor is equipped with a SK type static mixing element, and the last 20 m of the tubular reactor is equipped with a SV type static mixing element, so as to form a microchannel for the reaction liquid to flow through and react.

4. The device for continuously preparing isooctyl nitrate according to claim 2, characterized in that: The static mixing element is made of ceramic or stainless steel.

5. The device for continuously preparing isooctyl nitrate according to claim 1, characterized in that: The continuous feeding system consists of an isooctyl alcohol metering tank, a nitric acid metering tank, a sulfuric acid metering tank and three high-precision metering pumps. The high-precision metering pumps respectively meter the isooctyl alcohol, nitric acid and sulfuric acid in proportion and transport them into the spiral static mixer.

6. The device for continuously preparing isooctyl nitrate according to claim 1, characterized in that: The neutralization and separation system comprises a cooling tank, a neutralization water washing tank and a dehydrator.

7. A process for continuously preparing isooctyl nitrate using the device described in any one of claims 1 to 6, characterized in that: The raw materials of isooctyl alcohol, nitric acid and sulfuric acid are respectively pumped into the spiral static mixer by three high-precision metering pumps, and then enter the tubular reactor after being mixed by the spiral static mixer, so that the isooctyl alcohol and nitric acid react continuously in the presence of sulfuric acid, and the reaction liquid is neutralized, separated and purified online to obtain the product.

8. The process for continuously preparing isooctyl nitrate according to claim 7, characterized in that: Said The temperature of the continuous reaction is 30-60° C., and the residence time of the reaction liquid in the tubular reactor is 1-30 minutes.

9. The process for continuously preparing isooctyl nitrate according to claim 7, characterized in that: The raw materials of isooctyl alcohol, nitric acid and sulfuric acid are all commercially available chemical products. The purity of isooctyl alcohol is greater than 99%, the concentration of nitric acid is 65-98%, and the concentration of sulfuric acid is 90-98%.

10. The process for continuously preparing isooctyl nitrate according to claim 7, characterized in that: The molar ratio of the raw materials isooctyl alcohol, nitric acid and sulfuric acid is 1:1:1.5 to 1:1.1:2.3.

Images