A process and device for preparing alkyl nitrate

Abstract

The present invention belongs to the technical field of preparing alkyl nitrates by organic synthesis, and provides a process and device for preparing alkyl nitrates. The device comprises a mixed acid tank, a cycloalkanol tank, a microchannel nitration reactor, a separation tank, a washing tank, a waste acid tank and an acidic waste water tank; the microchannel nitration reactor has a nitric acid-sulfuric acid mixed acid pipe and a cycloalkanol pipeline; the mixed acid tank is connected to the nitric acid-sulfuric acid mixed acid pipe, and the cycloalkanol tank is connected to the cycloalkanol pipeline; the outlet of the microchannel nitration reactor is connected to the separation tank and the washing tank in sequence; the washing tank is connected to the cycloalkyl nitrate tank; the liquid outlet of the washing tank is also connected to the acidic waste water tank; the gas outlet of the separation tank is connected to the washing tank, and the liquid outlet is connected to the waste acid tank. The purity of the C3-C5 alkyl nitrate obtained by using the device is as high as 99.0% or more, and the process improves the production safety of the C3-C5 alkyl nitrate.

Description

Technical Field

[0001] The invention relates to the technical field of alkyl nitrate synthesis, and in particular to a process and a device for preparing C3-C5 alkyl nitrate. Background Art

[0002] As an important organic compound, alkyl nitrates can be used as solvents, automobile fuel additives or organic synthesis, but there are few methods for their synthesis. In particular, for the nitric esterification of short-chain C3-C4 alkyl alcohols, due to the large exothermic reaction, some C3-C4 alkyl alcohols contain secondary hydroxyl groups in their molecular structure, making their nitration more difficult. Currently, the reported preparation methods mainly use high-temperature nitration. For example, the document "Study on the Preparation Process of Isopropyl Nitrate" (Xi Meijue, Energetic Materials. 1998, (02)) uses the nitric esterification method to nitrate isopropyl alcohol at 100°C in the presence of urea and ammonium nitrate to produce isopropyl nitrate. The urea and ammonium nitrate added during the reaction process serve as stabilizers to prevent the decomposition of nitric acid at high temperature to produce a large amount of nitrogen oxide gas. This synthesis method has safety defects. First, the reaction temperature is high, and the raw materials need to be added slowly, resulting in low yield, high difficulty and danger in operation. Second, the waste acid contains residual urea and ammonium nitrate, which is complex in composition and cannot be recycled, increasing production and processing costs.

[0003] Patent CN 102557953 A "A method for preparing C4~C 10 The method for preparing alkyl straight-chain hydrocarbon monohydric alcohol nitrate is as follows: a protective agent, nitric acid and water are mixed to prepare a nitration mixture; the nitration mixture is placed at the bottom of a three-necked flask, a water separator, a dropping funnel and a thermometer are installed, and an oil bath is used for heating. When the nitration mixture is heated to 60-90°C, monohydric alcohol is added dropwise, and the obtained crude nitrate ester is purified and distilled to obtain C4-C 10 Alkyl straight-chain hydrocarbon monohydric alcohol nitrate. This patented method is similar to the document "Study on the Preparation Process of Isopropyl Nitrate", so its disadvantage is that the reaction operation is dangerous, and the later product still needs to be distilled and purified to meet the standards.

[0004] Patent CN 107721874A "A method for preparing nitrate compounds using microfluidic field reaction technology" uses a microchannel continuous synthesis method, with oxazole compounds as substrates, 1,4-dioxane as solvent, and tert-butyl nitrite as catalyst. The resulting mixed solution is pumped into a microchannel modular reaction device for reaction to prepare nitrate compounds. Ethyl acetate is used for post-treatment, and then ethanol is used for recrystallization to obtain the product. The advantage of this invention is that it avoids the use of concentrated sulfuric acid and concentrated nitric acid, but the disadvantage is also obvious. 1,4-dioxane, ethyl acetate, and ethanol in the reaction process have low flash points and strong volatility. 1,4-dioxane is miscible with water, which causes the problem of difficult wastewater treatment.

[0005] In summary, there are still many limitations on the synthesis of alkyl nitrates, mainly including: (1) the addition of stabilizers in the nitration process of C3-C4 alkyl alcohols makes the waste acid components complex and difficult to handle; (2) the use of nitric acid and sulfuric acid as nitrating agents in the mixed acid method results in a large exothermic reaction, a reaction rate that is difficult to control, and a large amount of nitrogen oxide gas that is easily generated, resulting in high emission and treatment costs; (3) the use of inert solvents to dilute the substrate to reduce the heat of reaction, and the product needs to be purified by separation in the later stage, which lengthens the production process and increases the cost. It is also worth pointing out that the descriptions of the synthesis of alkyl nitrates in the above literature and patents are all laboratory pilot processes, and the problems that may exist in pilot or large-scale production have not been solved. Therefore, the problem of industrial continuous and safe production of C3-C5 alkyl nitrates is the main problem to be solved by the present invention. Summary of the invention

[0006] In order to solve the problems in the synthesis process of C3-C5 alkyl nitrates in the prior art, the present invention provides a process and a device for preparing alkyl nitrates. The method is a safe and efficient synthesis process. The purity of C3-C5 alkyl nitrates obtained by using the device is as high as more than 99.0%. At the same time, the process improves the production safety of C3-C5 alkyl nitrates.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A C3-C5 alkyl nitrate preparation device comprises a mixed acid tank, a cycloalkanol tank, a microchannel nitration reactor, a separation tank, a washing tank, a waste acid tank, an acid waste water tank and a microchannel hydrocracking reactor;

[0009] The microchannel nitration reactor comprises a nitric acid and sulfuric acid mixed acid pipe and a cycloalkanol pipe; the mixed acid tank is connected to the nitric acid and sulfuric acid mixed acid pipe, and the cycloalkanol tank is connected to the cycloalkanol pipe;

[0010] The outlet of the microchannel nitration reactor is connected to a separation tank; the first outlet of the separation tank is connected to a washing tank; the washing tank is connected to a cycloalkyl nitrate tank; the outlet of the liquid in the washing tank is also connected to an acid waste water tank; the second outlet of the separation tank is connected to a waste acid tank;

[0011] The gas outlet of the separation tank, the liquid outlet of the cycloalkyl nitrate tank, and the nitrogen oxide gas outlet are all connected to the inlet of the microchannel hydrocracking reactor, and the outlet of the microchannel hydrocracking reactor is connected to the finished product tank.

[0012] As a further improvement of the present invention, the microchannel nitration reactor comprises a first reactor shell, a first cooling bath pipeline and a first internal pipeline, the first internal pipeline runs through the first reactor shell, and the first cooling bath pipeline is arranged between the first reactor shell and the first internal pipeline;

[0013] The nitric acid and sulfuric acid mixed acid pipe is located at the front end of the microchannel nitration reactor, the cycloalkyl alcohol pipe is located behind the inlet of the nitric acid and sulfuric acid mixed acid pipe, and the liquid flow directions of the cycloalkyl alcohol pipe inlet and the nitric acid and sulfuric acid mixed acid pipe inlet are countercurrent.

[0014] As a further improvement of the present invention, a gradient structure is formed at the connection between the nitric acid and sulfuric acid mixed acid pipe and the first internal pipe, and the gradient structure means that after the pipe diameter gradually decreases from the nitric acid and sulfuric acid mixed acid pipe to the first internal pipe, a uniform pipe diameter section is formed, and the pipe diameter gradually increases after the uniform pipe diameter section; the inlet of the cycloalkyl alcohol pipe is arranged at the connection between the gradually decreasing pipe diameter section of the first internal pipe and the uniform pipe diameter section, and the outlet direction of the cycloalkyl alcohol pipe is in a 45° convection direction with the gradient structure;

[0015] The cycloalkanol pipeline outlet is located at the bottom of the nitric acid and sulfuric acid mixed acid pipe, and both the cycloalkanol pipeline outlet and the nitric acid and sulfuric acid mixed acid pipe outlet are circular.

[0016] As a further improvement of the present invention, the microchannel hydrocracking reactor comprises a second reactor shell, a second cooling bath channel and a second internal pipe, the second internal pipe runs through the second reactor shell, and the second cooling bath channel is arranged between the second reactor shell and the second internal pipe; the surface material of the second internal pipe is nickel;

[0017] The microchannel hydrocracking reactor comprises a cycloalkyl nitrate pipeline, a nitrogen oxide gas pipeline and an N2 / H2 mixed gas pipeline; wherein the cycloalkyl nitrate pipeline is located at the front end of one side of the microchannel hydrocracking reactor and enters horizontally; the nitrogen oxide gas pipeline is located at the front lower end of the same side, enters vertically upward, and forms a 90° convection direction with the cycloalkyl nitrate pipeline; the N2 / H2 mixed gas pipeline is located at the middle and lower end of the microchannel hydrocracking reactor, enters vertically upward, and forms a 90° convection direction with the cycloalkyl nitrate pipeline.

[0018] As a further improvement of the present invention, the second internal pipeline structure is a bell-mouth structure; the cycloalkyl nitrate pipeline is connected to the large end of the bell-mouth structure.

[0019] As a further improvement of the present invention, the nitrogen oxide gas pipeline and the N2 / H2 mixed gas pipeline are both provided with multiple parallel inlets, the multiple parallel inlets are arranged side by side, and the diameters of the multiple parallel inlets decrease successively along the liquid flow direction.

[0020] As a further improvement of the present invention, the N2 / H2 mixed gas pipeline gas pump is connected to the hydrogen generator and the nitrogen generator respectively.

[0021] A process for preparing C3-C5 alkyl nitrate, based on the C3-C5 alkyl nitrate preparation device, comprises:

[0022] The mixed acid of nitric acid and sulfuric acid and C3-C4 cycloalkanol are introduced into the microchannel nitration reactor in the form of continuous flow to form a material flow, and a nitration reaction is carried out in the first internal pipeline to obtain C3-C4 cycloalkyl nitrate;

[0023] After separation and washing, C3-C4 cycloalkyl nitrate is introduced into a microchannel hydrocracking reactor, and after contacting with nitrogen oxide gas generated during nitration reaction in a microchannel nitration reactor in the front section of the microchannel hydrocracking reactor for deoxygenation, it is contacted with N2 / H2 mixed gas in the middle section of the microchannel hydrocracking reactor to react and catalyze the cracking of cycloalkyl, thereby finally obtaining C3-C5 alkyl nitrate;

[0024] After the waste gas is treated by subsequent equipment, the N2 / H2 mixed gas is discharged, and the nitrogen oxides are absorbed by water and converted into dilute HNO3 for recycling.

[0025] As a further improvement of the present invention, the feed temperature of the nitric acid-sulfuric acid mixed acid is 10-20°C, the feed rate is 300-800 mL / min, the feed temperature of the C3-C4 cycloalkanol is 15-30°C, and the feed rate is 200-350 mL / min;

[0026] The feed rate of the C3-C4 cycloalkyl nitrate is 220-400 mL / min, the feed rate of the nitrogen oxide gas is 20-30 mL / min, and the feed rate of the N2 / H2 mixed gas is 50-60 mL / min.

[0027] As a further improvement of the present invention, the circulating coolant used in the microchannel nitration reactor and the microchannel hydrocracking reactor is water, the temperature is 10-15°C and 70-90°C respectively, and the flow rate of the circulating coolant is 4-8L / min and 10-14L / min respectively.

[0028] Compared with the prior art, the present invention has the following beneficial technical effects:

[0029] The present invention uses a microchannel nitration reactor, firstly mixes C3-C4 cycloalkanol and a mixed acid of nitric acid and sulfuric acid in a certain ratio for reaction, and obtains C3-C4 cycloalkyl nitrate. The method can avoid a large amount of heat release during the nitration and esterification of short-chain alkane alcohol in the reaction process, and at the same time reduce the influence of the oxidation side reaction caused by the thermal decomposition of nitric acid to produce insoluble nitrogen oxide gas on the reaction process, effectively reduce the gas pressure of the micro-reaction channel, and reduce the safety risks caused by the runaway temperature and high pressure caused by the uncontrolled reaction rate of the nitrate in the reaction process, so that the C3-C4 cycloalkanol can complete the nitration reaction under normal, safe and controllable conditions. The present invention uses a microchannel hydrogenation ring-opening reactor, firstly mixes and contacts the nitrogen oxide gas generated in the nitration process with C3-C4 cycloalkyl nitrate, fully utilizes the principle that NO in the waste gas reacts with O2 to generate NO2, and pre-treats the C3-C4 cycloalkyl nitrate to remove oxygen. Thereafter, the material flow is contacted and reacted with the N2 / H2 mixed gas, and the final product C3-C5 alkyl nitrate is finally obtained, with a content of more than 99.0%, and no distillation and purification treatment is required, with huge economic and environmental benefits. In addition, after the waste gas is treated by the subsequent device, the N2 / H2 mixed gas is harmless to the environment and can be directly discharged, while the nitrogen oxide is converted into dilute HNO3 by water absorption, which can be recycled as a raw material, and the waste gas emission is greatly reduced.

[0030] The position and shape of the microchannel nitration reactor pipe port access are selected and designed according to the physical properties and flow principle of the materials. First, the C3-C4 cycloalkanol pipe port and the mixed acid pipe port face each other, and the place where the materials collide is the narrowest part of the pipe, which ensures that the heat transfer distance at the reaction hot spot is the shortest, and the external cold bath amount is the largest, all the reaction heat can be transferred in time, and as the material flows backward, the pipe diameter becomes thicker from the thin side, the reaction pressure is released, and safety and controllability are achieved in the whole reaction process; secondly, the C3-C4 cycloalkanol pipe port is arranged at the lower end of the overall pipe, which is conducive to the filling of the pipe interior from top to bottom by the alkyl alcohol with a smaller density, and the diameter of the mixed acid pipe becomes thinner before the reaction collision point, ensuring that the alkyl alcohol material has sufficient impact and collision at the reaction point, ensuring full contact with the alkyl alcohol, so that the two-phase material is mixed quickly and thoroughly, and the nitration reaction rate and conversion rate are guaranteed.

[0031] The microchannel hydrogenation ring-opening reactor design of the present invention is selected and designed according to the reaction law. First, the front section of the microchannel hydrogenation ring-opening reactor is provided with a nitrogen oxide gas pipeline inlet, which is perpendicular to the C3-C4 cycloalkyl nitrate and placed at the bottom, and uses the waste gas to deoxygenate the C3-C4 cycloalkyl nitrate to ensure the feasibility of the back-end hydrogenation process. Compared with the traditional kettle hydrogenation reaction, its deoxygenation and hydrogenation ring-opening reaction can be realized continuously; secondly, the nitrogen oxide gas pipeline 12 inlet and the N2 / H2 mixed gas pipeline 15 inlet in the microchannel hydrogenation ring-opening reactor are arranged in a multi-inlet linear shape, and gas is continuously provided from top to bottom to ensure C3 The C3-C4 cycloalkyl nitrate ester flow can be contacted and reacted with a sufficient amount of oxygen compound gas or N2 / H2 mixed gas during the flow process to achieve the effect of complete deoxygenation and hydrogenation ring-opening reaction; finally, the second internal pipeline in the microchannel hydrogenation ring-opening reactor is designed to be conical, which is large at first and then small, to ensure that when the material flow contacts and reacts with the N2 / H2 mixed gas, the pressure generated by the narrowing of the pipeline diameter satisfies the pressure required for the hydrogenation ring-opening reaction, and the C3-C4 cycloalkyl nitrate is finally opened to obtain C3-C5 alkyl nitrate with high purity and no by-products produced by side reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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 embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0033] Figure 1 This is a schematic diagram of the process flow for synthesizing C3-C5 alkyl nitrates of the present invention;

[0034] Figure 2 Appearance structure diagram of microchannel nitrification reactor;

[0035] Figure 3 Top view of the microchannel nitrification reactor;

[0036] Figure 4 Side view of the microchannel nitrification reactor;

[0037] Figure 5 Appearance structure diagram of microchannel hydrogenation ring-opening reactor;

[0038] Figure 6 Top view of the microchannel hydrogenation ring-opening reactor;

[0039] Figure 7 Side view of the microchannel hydrogenation ring-opening reactor;

[0040] Figure 8 Front view of the microchannel hydrogenation ring-opening reactor;

[0041] Fig. 9 Gas chromatography analysis chart of C3-C5 alkyl nitrate obtained in Example 1 of the present invention;

[0042] Fig.10 Gas chromatography analysis chart of C3-C5 alkyl nitrate obtained in Example 2 of the present invention;

[0043] Fig.11 The gas chromatographic analysis chart of C3-C5 alkyl nitrate obtained in Example 3 of the present invention;

[0044] Fig.12 Gas chromatography analysis chart of C3-C5 alkyl nitrate obtained in Example 4 of the present invention;

[0045] Fig.13 The gas chromatographic analysis chart of C3-C5 alkyl nitrate prepared in Example 5 of the present invention;

[0046] Fig.14 This is the gas chromatographic analysis chart of C3-C5 alkyl nitrate obtained in Example 6 of the present invention. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0048] The theories or mechanisms described and disclosed in the present invention, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0049] In the present invention, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0050] In the present invention, unless otherwise specified, “comprising”, “including”, “containing”, “having” or similar terms cover the meanings of “consisting of” and “mainly consisting of”, for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a”.

[0051] In the present invention, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0052] Cyclopropanol or cyclobutanol is a cycloalkane alcohol molecule that consists of three or four interconnected carbon atoms, each with one to two hydrogen atoms (or none). The small size of the ring produces significant ring strain in the structure. Under certain conditions, these three-membered or four-membered ring skeletons can easily participate in ring-opening reactions to form the corresponding straight-chain skeleton structures. This is due to the sp 3 Hybridization, the normal angle between molecular orbitals is 109°28', so when forming small cycloalkanes, the bond angle within the molecule will deviate from the normal bond angle, thus generating angle tension. 3 The hybrid orbitals cannot meet head-on on the line between the two carbon atoms to achieve maximum overlap, and the electron cloud overlap between CCs is poor. Therefore, three- and four-membered rings are not as stable as open chains and are prone to ring-opening reactions.

[0053] Since both three- and four-membered rings can undergo ring-opening reactions, and for branched cycloalkanes, catalytic hydrogenation occurs at a position with less steric resistance to form more stable forked chain compounds. Therefore, selecting appropriate cycloalkanols for nitration and then ring-opening to prepare the corresponding alkyl nitrates is a process route for preparing C3-C5 alkyl nitrates, for example:

[0054]

[0055] Therefore, the present invention provides a safe and efficient process for synthesizing C3-C5 alkyl nitrates, comprising:

[0056] The nitric acid and sulfuric acid mixed acid and C3-C4 cycloalkanol are introduced into the microchannel nitration reactor 4 in the form of continuous flow to form a material flow, and the nitration reaction is carried out in the first internal pipeline to obtain C3-C4 cycloalkyl nitrate. After separation and washing, the material is introduced into the microchannel hydrocracking reactor 20 again, and after contacting and deoxygenating with the nitrogen oxide gas generated during the nitration reaction in the front section, it is contacted and reacted with the N2 / H2 mixed gas in the middle section to catalyze the cracking of the cycloalkyl, and finally obtain C3-C5 alkyl nitrate. When the production is completed, the hydrogen generator 24 is turned off, the nitrogen generator is kept open, and the microchannel nitration reverse hydrogenation ring opener is purged with nitrogen to discharge all materials.

[0057] The principle is: a mixed acid of nitric acid and sulfuric acid and C3-C4 cycloalkanol are introduced into a microchannel nitration reactor in the form of continuous flow through an acid pump and an alcohol pump respectively, and a nitration reaction is carried out in a first internal pipeline to obtain C3-C4 cycloalkyl nitrates. The material is then separated and washed and then contacted with a H2 gas flow in a microchannel hydrocracking reactor to react, thereby promoting the ring opening of the cycloalkyl group and converting it into a corresponding straight chain (or branched) structure to obtain the final alkyl nitrate.

[0058] The purity of the C3-C5 alkyl nitrate obtained by the method is as high as over 99.0%, and the process improves the production safety of the C3-C5 alkyl nitrate.

[0059] In order to realize the above-mentioned process of safely and efficiently synthesizing C3-C5 alkyl nitrates, the equipment parameters provided in the embodiment of the present invention are not the only choice. As long as the above-mentioned processing process flow is met, the relevant parameters of the equipment can be appropriately adjusted.

[0060] As an optional embodiment, the feed temperature of the nitric acid and sulfuric acid mixed acid is 10-20°C, and the feed rate is 300-800 mL / min, and the feed temperature of C3-C4 cycloalkanol is 15-30°C, and the feed rate is 200-350 mL / min.

[0061] As an optional embodiment, the feed rate of the C3-C4 cycloalkyl nitrate is 220-400 mL / min, the feed rate of the nitrogen oxide gas is 20-30 mL / min, and the feed rate of the N2 / H2 mixed gas is 50-60 mL / min.

[0062] like Figure 1 As shown, the present invention also provides a C3-C5 alkyl nitrate preparation device based on the method, comprising: a mixed acid tank 1, a cycloalkanol tank 3, a microchannel nitration reactor 4, a separation tank 6, a washing tank 5, a waste acid tank 7 and an acid wastewater tank 8;

[0063] like Figure 2 As shown, the microchannel nitration reactor 4 has a nitric acid and sulfuric acid mixed acid pipe 41 and a cycloalkanol pipe 42; the mixed acid tank 1 is connected to the nitric acid and sulfuric acid mixed acid pipe 41, and the cycloalkanol tank 3 is connected to the cycloalkanol pipe 42;

[0064] The outlet of the microchannel nitration reactor 4 is connected to a separation tank 6 and a washing tank 5 in sequence; the washing tank 5 is connected to a cycloalkyl nitrate tank 10 .

[0065] The liquid outlet of the washing tank 5 is also connected to the acidic wastewater tank 8; the gas outlet of the separation tank 6 and the liquid outlet of the cycloalkyl nitrate tank 10 are both connected to the inlet of the microchannel hydrocracking reactor 20, and the outlet of the microchannel hydrocracking reactor 20 is connected to the finished product tank 23.

[0066] Furthermore, if Figure 2 to Figure 4 As shown, the microchannel nitration reactor 4 includes a first reactor shell, a first cooling bath pipe 44 and a first internal pipe. The first internal pipe runs through the first reactor shell, and the first cooling bath pipe 44 is arranged between the first reactor shell and the first internal pipe. The microchannel nitration reaction has a phenomenon of instantaneous heat release because the effective reaction space is small. Therefore, the first cooling bath pipe 44 can control the internal temperature of the reactor to avoid a large amount of heat release affecting the reaction.

[0067] Furthermore, if Figure 3 As shown, the nitric acid and sulfuric acid mixed acid pipe 41 is located at the front end of the microchannel nitration reactor 4, and the cycloalkyl alcohol pipeline 42 is located after the nitric acid and sulfuric acid mixed acid pipe 41, and the liquid flows of the two are in a 45° angle convection direction. The materials are mixed more fully, the reaction efficiency is improved, and the 45° angle convection will not affect the overall flow direction of the nitric acid and sulfuric acid mixed acid.

[0068] Furthermore, the N2 / H2 mixed gas pipeline 15 is connected to a hydrogen generator 24 and a nitrogen generator 25.

[0069] Further, as an optional solution, the nitric acid and sulfuric acid mixed acid pipe 41 forms a gradual structure at the connection with the first internal pipe. The gradual structure means that after the diameter of the nitric acid and sulfuric acid mixed acid pipe 41 gradually decreases to the first internal pipe, there is a uniform pipe diameter section, and then it gradually increases; the inlet of the cycloalkyl alcohol pipe 42 is set at the connection between the gradually decreasing section of the first internal pipe diameter and the uniform pipe diameter section. The C3-C4 cycloalkyl alcohol pipe mouth and the mixed acid pipe mouth are facing each other, and the place where the materials collide is the narrowest part of the pipe, which ensures that the heat transfer distance at the reaction hot spot is the shortest, and the external cold bath volume is the largest, all the reaction heat can be transferred in time, and as the material flows backward, the pipe diameter changes from thin to thick, the reaction pressure is released, and the whole reaction process is safe and controllable.

[0070] The outlet of the cycloalkanol pipeline 42 is located in the uniform pipe diameter section, and the outlet direction of the cycloalkanol pipeline 42 forms a 45° convection direction with the gradient structure.

[0071] Furthermore, if Figure 4 As shown, the outlet of the cycloalkanol pipeline 42 is located at the bottom of the nitric acid and sulfuric acid mixed acid pipeline 41, and both the outlet of the cycloalkanol pipeline 42 and the outlet of the nitric acid and sulfuric acid mixed acid pipeline 41 are circular. The C3-C4 cycloalkanol pipe port is arranged at the lower end of the overall pipeline, which is conducive to the filling of the interior of the pipeline from bottom to top by the alkyl alcohol with a smaller density, and the diameter of the mixed acid pipeline changes from thick to thin before the reaction collision point, ensuring sufficient impact and collision on the alkyl alcohol material at the reaction point, ensuring full contact with the alkyl alcohol, so that the two-phase materials are mixed quickly and thoroughly, and the nitration reaction rate and conversion rate are guaranteed.

[0072] The specific raw materials are described as follows: nitric acid and sulfuric acid mixed acid and C3~C4 cycloalkanol are introduced into the microchannel nitration reactor 4 in the form of continuous flow to form a material flow, and a nitration reaction is carried out in the first internal pipeline to obtain C3~C4 cycloalkyl nitrate. The principle is that C5 cycloalkyl nitrate cannot open the ring, while C3~C4 cycloalkyl can open the ring to generate C3~C4 straight-chain alkyl. If the C3~C4 ring has an alkyl side chain, such as methyl, a C4~C5 straight-chain alkyl can be formed. Therefore, C3~C4 cycloalkyl alcohol is used to prepare C3~C5 alkyl nitrate.

[0073] The microchannel hydrocracking reactor 20 includes a second reactor shell, a second cooling bath channel 17 and a second internal pipe. The second internal pipe runs through the second reactor shell. The second cooling bath channel 17 is arranged between the second reactor shell and the second internal pipe. The surface material of the second internal pipe of the second reactor is nickel.

[0074] Furthermore, the second internal pipeline structure is a cone; the microchannel hydrocracking reactor 20 has a cycloalkyl nitrate pipeline 11, a nitrogen oxide gas pipeline 12 and an N2 / H2 mixed gas pipeline 15; wherein, the cycloalkyl nitrate pipeline 11 is located at the front end of one side of the microchannel hydrocracking reactor 20, and the nitrogen oxide gas pipeline 12 is located at the front lower end of the same side, enters vertically upward, and forms a 90° convection direction with the cycloalkyl nitrate pipeline 11; the N2 / H2 mixed gas pipeline 15 is located at the middle and lower end of the microchannel hydrocracking reactor 20, enters vertically upward, and also forms a 90° convection direction with the cycloalkyl nitrate pipeline 11.

[0075] Furthermore, if Figures 6 to 8 As shown, the microchannel hydrocracking reactor 20 includes three material pipeline inlets: a cycloalkyl nitrate pipeline 11 inlet, a nitrogen oxide gas pipeline 12 inlet and a N 2 / The inlet of H2 mixed gas pipeline 15. The nitrogen pipeline 13 and the hydrogen pipeline 14 are mixed and connected. 2 / H2 mixed gas pipeline 15. Among them, the inlet of the cycloalkyl nitrate pipeline 11 is located at the front end of one side of the microchannel hydrocracking reactor 20, and enters horizontally, the inlet of the nitrogen oxide gas pipeline 12 is located at the front lower end of the same side of the microchannel hydrocracking reactor 20, and enters vertically upward, the two are in a 90° angle convection direction, and the horizontal distance is 2 to 4 mm, and the inlet of the N2 / H2 mixed gas pipeline 15 is located at the lower part of the microchannel hydrocracking reactor 20, and enters vertically upward, which is about 12 to 16 mm horizontally backward than the inlet of the nitrogen oxide gas pipeline 12.

[0076] A nitrogen oxide gas pipeline inlet is set at the front section of the microchannel hydrogenation ring-opening reactor, which is perpendicular to the C3-C4 cycloalkyl nitrate and placed at the bottom. The exhaust gas is used to deoxygenate the C3-C4 cycloalkyl nitrate to ensure the feasibility of the back-end hydrogenation process. Compared with the traditional kettle hydrogenation reaction, its deoxygenation and hydrogenation ring-opening reaction can be realized continuously.

[0077] like Figure 6 and Figure 7 As shown, both the nitrogen oxide gas pipeline 12 and the N2 / H2 mixed gas pipeline 15 are provided with multiple parallel inlets. The multiple parallel inlets are arranged side by side, and the diameters of the multiple parallel inlets decrease in sequence along the liquid flow direction. For example, the nitrogen oxide gas pipeline 12 is provided with three parallel inlets, and the diameters of the three inlets decrease in sequence from left to right, and the N2 / H2 mixed gas pipeline 15 is provided with four parallel inlets, and the diameters of the four inlets decrease in sequence from left to right. The inlet of the nitrogen oxide gas pipeline 12 and the inlet of the N2 / H2 mixed gas pipeline 15 in the microchannel hydrogenation ring-opening reactor are both arranged in a multi-inlet linear type, and gas is continuously supplied from bottom to top, ensuring that the C3~C4 cycloalkyl nitrate ester flow can be in contact with a sufficient amount of oxygen compound gas or N2 / H2 mixed gas during the flow process to achieve the effect of complete deoxygenation and hydrogenation ring-opening reaction; the second internal pipeline in the microchannel hydrogenation ring-opening reactor is designed to be conical, first large and then small, ensuring that when the material flow is in contact with the N2 / H2 mixed gas, the pressure generated by the narrowing of the pipeline diameter satisfies the pressure required for the hydrogenation ring-opening reaction, and the C3~C4 cycloalkyl nitrate is finally opened to obtain C3~C5 alkyl nitrate with high purity and no by-products generated by side reactions.

[0078] Furthermore, the circulating coolant used in the microchannel nitration reactor 4 and the microchannel hydrocracking reactor 20 is water, and the temperature is 10-15°C and 70-90°C, respectively, and the flow rate of the circulating coolant is 4-8 L / min and 10-14 L / min, respectively.

[0079] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0080] Example 1

[0081] At room temperature, nitric acid and sulfuric acid mixed acid and cyclopropyl alcohol are introduced into a special microchannel nitration reactor 4 in the form of continuous flow through an acid pump and an alcohol pump, respectively, and a nitration reaction is carried out in the front synthesis section of the reactor to obtain cyclopropyl nitrate. The feed temperature of nitric acid and sulfuric acid mixed acid is 20°C, the feed rate is 740mL / min, the feed temperature of cyclopropyl alcohol is 15°C, the feed rate is 280mL / min, the temperature of circulating cooling water in the reactor is 12°C, and the flow rate is 4.5L / min. After the cyclopropyl nitrate is separated and washed in the later stage, it is introduced into the microchannel hydrogenation ring-opening reactor again, and after being deoxygenated by nitrogen oxide gas in the front section, it contacts with the N2 / H2 mixed gas in the middle section to produce a ring-opening reaction, and finally the corresponding n-propyl nitrate is obtained. The feed rate of cyclopropyl nitrate is 240 mL / min, the feed rate of nitrogen oxide gas is 20 mL / min, the feed rate of N2 / H2 mixed gas is 52 mL / min, the temperature of circulating cooling water in the reactor is 73°C, and the flow rate is 12.8 L / min.

[0082] Fig. 9 The gas chromatographic analysis chart of n-propyl nitrate obtained in Example 1 of the present invention is as follows; the yield is 97.41% and the purity is 99.85%.

[0083] Example 2

[0084] At room temperature, nitric acid and sulfuric acid mixed acid and 1-methylcyclopropyl alcohol are introduced into a special microchannel nitration reactor 4 in the form of continuous flow through an acid pump and an alcohol pump respectively, and a nitration reaction is carried out in the front synthesis section of the reactor to obtain 1-methyl-cyclopropyl nitrate. The feed temperature of nitric acid and sulfuric acid mixed acid is 20°C, the feed rate is 640mL / min, the feed temperature of 1-methylcyclopropyl alcohol is 30°C, the feed rate is 220mL / min, the circulating cooling water temperature in the reactor is 14°C, and the flow rate is 6L / min. After the 1-methyl-cyclopropyl nitrate is separated and washed in the later stage, it is introduced into the microchannel hydrogenation ring-opening reactor again, and after being deoxygenated by nitrogen oxide gas in the front section, it contacts with the N2 / H2 mixed gas in the middle section to generate a ring-opening reaction, and finally the corresponding 1-methyl-n-propyl nitrate is obtained. The feed rate of 1-methyl-cyclopropyl nitrate is 270 mL / min, the feed rate of nitrogen oxide gas is 30 mL / min, the feed rate of N2 / H2 mixed gas is 60 mL / min, the temperature of circulating cooling water in the reactor is 81°C, and the flow rate is 13 L / min.

[0085] Fig.10 The gas chromatographic analysis chart of 1-methyl-n-propyl nitrate obtained in Example 2 of the present invention is as follows; the yield is 98.55% and the purity is 99.43%.

[0086] Example 3

[0087] At room temperature, nitric acid and sulfuric acid mixed acid and hydroxymethyl cyclopropane alcohol are introduced into a special microchannel nitration reactor 4 in the form of continuous flow through an acid pump and an alcohol pump, respectively, and a nitration reaction is carried out in the front synthesis section of the reactor to obtain cyclopropane methyl nitrate. The feed temperature of nitric acid and sulfuric acid mixed acid is 12°C, the feed rate is 500mL / min, the feed temperature of hydroxymethyl cyclopropane alcohol is 25°C, the feed rate is 280mL / min, the circulating cooling water temperature in the reactor is 10°C, and the flow rate is 7L / min. After the cyclopropane methyl nitrate is separated and washed in the later stage, it is introduced into the microchannel hydrogenation ring-opening reactor again, and after being deoxygenated by nitrogen oxide gas in the front section, it contacts with the N2 / H2 mixed gas in the middle section to generate a ring-opening reaction, and finally the corresponding n-butyl nitrate is obtained. The feed rate of cyclopropane methyl nitrate is 400 mL / min, the feed rate of nitrogen oxide gas is 30 mL / min, the feed rate of N2 / H2 mixed gas is 60 mL / min, the temperature of circulating cooling water in the reactor is 70°C, and the flow rate is 14 L / min.

[0088] Fig.11 The gas chromatographic analysis chart of n-butyl nitrate obtained in Example 3 of the present invention is as follows; the yield is 99.02% and the purity is 99.86%.

[0089] Example 4

[0090] At room temperature, nitric acid and sulfuric acid mixed acid and cyclobutanol are introduced into a special microchannel nitration reactor 4 in the form of continuous flow through an acid pump and an alcohol pump, respectively, and a nitration reaction is carried out in the front synthesis section of the reactor to obtain cyclobutyl nitrate. The feed temperature of nitric acid and sulfuric acid mixed acid is 20°C, the feed rate is 900mL / min, the feed temperature of cyclobutanol is 15°C, the feed rate is 350mL / min, the temperature of circulating cooling water in the reactor is 10°C, and the flow rate is 8L / min. After the cyclobutyl nitrate is separated and washed in the later stage, it is introduced into the microchannel hydrogenation ring-opening reactor again, and after being deoxygenated by nitrogen oxide gas in the front section, it contacts with the N2 / H2 mixed gas in the middle section to produce a ring-opening reaction, and finally the corresponding n-butyl nitrate is obtained. The feed rate of cyclobutyl nitrate is 330 mL / min, the feed rate of nitrogen oxide gas is 20 mL / min, the feed rate of N2 / H2 mixed gas is 57 mL / min, the temperature of circulating cooling water in the reactor is 70°C, and the flow rate is 10 L / min.

[0091] Fig.12 The gas chromatographic analysis chart of n-butyl nitrate obtained in Example 4 of the present invention is as follows; the yield is 98.78% and the purity is 99.87%.

[0092] Example 5

[0093] At room temperature, nitric acid and sulfuric acid mixed acid and 2-methyl-cyclobutanol are introduced into a special microchannel nitration reactor 4 in the form of continuous flow through an acid pump and an alcohol pump, respectively, and a nitration reaction is carried out in the front synthesis section of the reactor to obtain 2-methyl-cyclobutyl nitrate. The feed temperature of nitric acid and sulfuric acid mixed acid is 16°C, the feed rate is 620mL / min, the feed temperature of 2-methyl-cyclobutanol is 20°C, the feed rate is 300mL / min, the circulating cooling water temperature in the reactor is 10°C, and the flow rate is 6.5L / min. After the 2-methyl-cyclobutyl nitrate is separated and washed in the later stage, it is introduced into the microchannel hydrogenation ring-opening reactor again, and after being deoxygenated by nitrogen oxide gas in the front section, it contacts with the N2 / H2 mixed gas in the middle section to produce a ring-opening reaction, and finally the corresponding 1-ethyl-n-propyl nitrate is obtained. The feed rate of 2-methyl-cyclobutyl nitrate is 400 mL / min, the feed rate of nitrogen oxide gas is 26 mL / min, the feed rate of N2 / H2 mixed gas is 53 mL / min, the temperature of circulating cooling water in the reactor is 90°C, and the flow rate is 14 L / min.

[0094] Fig.13 The gas chromatographic analysis chart of 1-ethyl-n-propyl nitrate obtained in Example 5 of the present invention is as follows; the yield is 99.39% and the purity is 99.56%.

[0095] Example 6

[0096] At room temperature, nitric acid and sulfuric acid mixed acid and 3-methyl-cyclobutanol are introduced into a special microchannel nitration reactor 4 in the form of continuous flow through an acid pump and an alcohol pump, respectively, and a nitration reaction is carried out in the front synthesis section of the reactor to obtain 3-methyl-cyclobutyl nitrate. The feed temperature of nitric acid and sulfuric acid mixed acid is 18°C, the feed rate is 750mL / min, the feed temperature of 3-methyl-cyclobutanol is 30°C, the feed rate is 350mL / min, the circulating cooling water temperature in the reactor is 15°C, and the flow rate is 7L / min. After the 3-methyl-cyclobutyl nitrate is separated and washed in the later stage, it is introduced into the microchannel hydrogenation ring-opening reactor again, and after being deoxygenated by nitrogen oxide gas in the front section, it contacts with the N2 / H2 mixed gas in the middle section to produce a ring-opening reaction, and finally the corresponding 1-methyl-n-butyl nitrate is obtained. The feed rate of 3-methyl-cyclobutyl nitrate is 300 mL / min, the feed rate of nitrogen oxide gas is 30 mL / min, the feed rate of N2 / H2 mixed gas is 50 mL / min, the temperature of circulating cooling water in the reactor is 90°C, and the flow rate is 12 L / min.

[0097] Fig.14 The gas chromatographic analysis chart of 1-methyl-n-butyl nitrate obtained in Example 6 of the present invention is shown in Figure 6. The yield is 99.21% and the purity is 99.42%.

[0098] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0099] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A C3~C5 alkyl nitrate preparation device, characterized in that: It comprises a mixed acid tank (1), a cycloalkanol tank (3), a microchannel nitration reactor (4), a separation tank (6), a washing tank (5), a waste acid tank (7), an acid waste water tank (8) and a microchannel hydrocracking reactor (20); The microchannel nitration reactor (4) comprises a nitric acid and sulfuric acid mixed acid pipe (41) and a cycloalkanol pipe (42); the mixed acid tank (1) is connected to the nitric acid and sulfuric acid mixed acid pipe (41), and the cycloalkanol tank (3) is connected to the cycloalkanol pipe (42); The outlet of the microchannel nitration reactor (4) is connected to a separation tank (6); the first outlet of the separation tank (6) is connected to a washing tank (5); the washing tank (5) is connected to a cycloalkyl nitrate tank (10); the outlet of the liquid of the washing tank (5) is also connected to an acid waste water tank (8); the second outlet of the separation tank (6) is connected to a waste acid tank (7); The gas outlet of the separation tank (6), the liquid outlet of the cycloalkyl nitrate tank (10), and the nitrogen oxide gas outlet are all connected to the inlet of the microchannel hydrocracking reactor (20), and the outlet of the microchannel hydrocracking reactor (20) is connected to the finished product tank (23); The microchannel nitration reactor (4) comprises a first reactor shell, a first cooling bath pipeline (44) and a first internal pipeline, the first internal pipeline runs through the first reactor shell, and the first cooling bath pipeline (44) is arranged between the first reactor shell and the first internal pipeline; The nitric acid and sulfuric acid mixed acid pipe (41) is located at the front end of the microchannel nitration reactor (4), and the cycloalkanol pipe (42) is located after the inlet of the nitric acid and sulfuric acid mixed acid pipe (41). The liquid flow directions of the inlet of the cycloalkanol pipe (42) and the inlet of the nitric acid and sulfuric acid mixed acid pipe (41) are countercurrent. The connection between the nitric acid and sulfuric acid mixed acid pipe (41) and the first internal pipe forms a gradual structure, wherein the gradual structure means that the pipe diameter gradually decreases from the nitric acid and sulfuric acid mixed acid pipe (41) to the first internal pipe, and then forms a uniform pipe diameter section, and the pipe diameter gradually increases after the uniform pipe diameter section; the inlet of the cycloalkanol pipe (42) is arranged at the connection between the section where the pipe diameter gradually decreases and the uniform pipe diameter section of the first internal pipe, and the outlet direction of the cycloalkanol pipe (42) is at a 45° angle to the convection direction of the gradual structure; The outlet of the cycloalkanol pipeline (42) is located at the bottom of the nitric acid and sulfuric acid mixed acid pipeline (41), and the outlet of the cycloalkanol pipeline (42) and the outlet of the nitric acid and sulfuric acid mixed acid pipeline (41) are both circular; The microchannel hydrocracking reactor (20) comprises a second reactor shell, a second cooling bath channel (17) and a second internal pipe, wherein the second internal pipe runs through the second reactor shell, and the second cooling bath channel (17) is arranged between the second reactor shell and the second internal pipe; the surface material of the second internal pipe is nickel; The microchannel hydrocracking reactor (20) comprises a cycloalkyl nitrate pipeline (11), a nitrogen oxide gas pipeline (12) and an N2 / H2 mixed gas pipeline (15); wherein the cycloalkyl nitrate pipeline (11) is located at the front end of one side of the microchannel hydrocracking reactor (20) and enters horizontally; the nitrogen oxide gas pipeline (12) is located at the front lower end of the same side and enters vertically upward, forming a countercurrent direction of 90° with the cycloalkyl nitrate pipeline (11); and the N2 / H2 mixed gas pipeline (15) is located at the middle lower end of the microchannel hydrocracking reactor (20) and enters vertically upward, forming a countercurrent direction of 90° with the cycloalkyl nitrate pipeline (11).

2. The C3~C5 alkyl nitrate preparation device according to claim 1, characterized in that: The second internal pipeline structure is a bell-mouth structure; the cycloalkyl nitrate pipeline (11) is connected to the large end of the bell-mouth structure.

3. The C3~C5 alkyl nitrate preparation device according to claim 1, characterized in that: The nitrogen oxide gas pipeline (12) and the N2 / H2 mixed gas pipeline (15) are both provided with a plurality of parallel inlets, the plurality of parallel inlets are arranged side by side, and the diameters of the plurality of parallel inlets decrease successively along the liquid flow direction.

4. The C3~C5 alkyl nitrate preparation device according to claim 1, characterized in that: The gas pump of the N2 / H2 mixed gas pipeline (15) is respectively connected to the hydrogen generator (24) and the nitrogen generator (25).

5. A process for preparing C3~C5 alkyl nitrate, based on the C3~C5 alkyl nitrate preparation device according to any one of claims 1 to 4, characterized in that: include: Introducing a nitric acid-sulfuric acid mixture and a C3-C4 cycloalkanol into a microchannel nitration reactor (4) in the form of continuous flow to form a material flow, and performing a nitration reaction in a first internal pipe to produce a C3-C4 cycloalkyl nitrate; After separation and washing, the C3~C4 cycloalkyl nitrate is introduced into a microchannel hydrocracking reactor (20), and after being contacted with nitrogen oxide gas generated during the nitration reaction of the microchannel nitration reactor (4) in the front section of the microchannel hydrocracking reactor (20) to remove oxygen, it is contacted with N2 / H2 mixed gas in the middle section of the microchannel hydrocracking reactor (20) to react, catalyzing the cracking of the cycloalkyl, and finally obtaining C3~C5 alkyl nitrate; After the waste gas is treated by subsequent equipment, the N2 / H2 mixed gas is discharged, and the nitrogen oxides are absorbed by water and converted into dilute HNO3 for recycling.

6. The process for preparing C3-C5 alkyl nitrate according to claim 5, characterized in that: The feed temperature of the nitric acid-sulfuric acid mixed acid is 10-20°C, and the feed rate is 300-800 mL / min; the feed temperature of the C3-C4 cycloalkanol is 15-30°C, and the feed rate is 200-350 mL / min; The feed rate of the C3-C4 cycloalkyl nitrate is 220-400 mL / min, the feed rate of the nitrogen oxide gas is 20-30 mL / min, and the feed rate of the N2 / H2 mixed gas is 50-60 mL / min.

7. The process for preparing C3-C5 alkyl nitrate according to claim 5, characterized in that: The circulating coolant used inside the microchannel nitration reactor (4) and the microchannel hydrocracking reactor (20) is water, with temperatures of 10-15°C and 70-90°C, respectively, and flow rates of the circulating coolant of 4-8 L / min and 10-14 L / min, respectively.

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