Synthesis method for sodium azide

Abstract

A synthesis method for sodium azide, comprising: using an aromatic alcohol as a raw material to prepare an alkyl nitrite of the aromatic alcohol; under alkaline conditions, reacting the alkyl nitrite with a hydrazine hydrate in a reduction reaction, to prepare sodium azide, the aromatic alcohol comprising one or more compounds having the structural formula represented as: (I), Ar being selected from any one of the following: substituted or unsubstituted C6-C20 aryl groups, and substituted or unsubstituted C3-C10 heteroaryl groups, R being selected from (II) and n being an integer of 1-3; in (III), R1 and R2 are the same or different, and are independently selected from any one of H and C1-C3 alkyl groups; when Ar is selected from substituted C6-C20 aryl groups or substituted C3-C10 heteroaryl groups, substituents of the substituted groups are selected from C1-C9 alkyl groups, and * represents a connection site.

Description

Synthesis method of sodium azide

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. 202410075293.3, filed on January 18, 2024, entitled “Method for the synthesis of sodium azide,” the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the field of chemical engineering technology, and in particular to a method for synthesizing sodium azide. Background Art

[0004] Sodium azide is a key raw material for the construction of high-energy chemicals and is the most widely used and widely used inorganic azide salt. For example, sodium azide is used as a filler in automotive airbags and emergency inflatable slides on passenger aircraft. Its diverse and active chemical properties make it a precursor for the synthesis of various organic azides, offering irreplaceable application value in chemistry, materials, and biology.

[0005] In the related art, currently, small molecule fatty alcohols are mainly used as raw materials to prepare the nitrites of these small molecule fatty alcohols, and then the nitrites of these small molecule fatty alcohols are reduced with hydrazine hydrate under alkaline conditions to synthesize sodium azide. The above reduction reaction has at least the following problems: First, the nitrite esters of these small-molecule fatty alcohols have a high solubility in aqueous phase and are easily hydrolyzed in alkaline aqueous solution to produce sodium nitrite. The hydrolysis rate can often reach more than 20%, which not only wastes raw materials but also increases a large amount of sodium nitrite as a by-product and increases the cost of separating sodium azide and the by-product sodium nitrite. Second, in order to suppress side reactions, the nitrite ester is usually added dropwise, and the reaction time can be several hours or even more than ten hours, which is inefficient. Third, the nitrite esters of these small-molecule fatty alcohols have a low boiling point, and the partial pressure in the gas phase space is high during the reaction. They are easily decomposed to produce highly active free radicals, which are extremely dangerous intermediates. More seriously, the product sodium azide itself is an extremely explosive substance, which will bring huge safety risks. In addition, industrial production will inevitably cause the emission of volatile organic compounds (VOCs), and nitrite esters quickly decompose into greenhouse gases such as nitric oxide and nitrous oxide in the atmosphere, all of which will pollute the environment.

[0006] Summary of the Invention

[0007] Based on this, it is necessary to provide a synthetic method of sodium azide.

[0008] A method for synthesizing sodium azide, comprising:

[0009] Using aromatic alcohol as a raw material to prepare the nitrite ester of the aromatic alcohol; and

[0010] Under alkaline conditions, the nitrite is subjected to a reduction reaction with hydrazine hydrate to prepare the sodium azide;

[0011] Wherein, the aromatic alcohol is selected from the group consisting of One or more compounds of the invention, wherein Ar is selected from the following substituted or unsubstituted C6 to C 20 Aryl and substituted or unsubstituted C3~C 10 Any of the heteroaryl groups, R is selected from n is an integer from 1 to 3;

[0012] Among them, In the embodiment, R1 and R2 are the same or different and are independently selected from any one of H and C1-C3 alkyl, and the substituted C6-C 20 Aryl and substituted C3~C 10 The substituents in the heteroaryl group are independently selected from C1 to C9 alkyl groups, and * represents the connection site between Ar and R.

[0013] Optionally, n is equal to 1, and R1 and R2 are selected from H or methyl, substituted C6~C 20 Aryl and substituted C3~C 10 Substituents in the heteroaryl group are independently selected from methyl or ethyl.

[0014] Optionally, the aromatic alcohol is selected from one or more of the following structural formulas:

[0015] Optionally, the process of preparing the nitrite ester of the aromatic alcohol using the aromatic alcohol as a raw material comprises:

[0016] The aromatic alcohol is subjected to an esterification reaction with nitrite in the presence of an inorganic acid to generate the nitrite.

[0017] Optionally, the nitrite is selected from one or a combination of sodium nitrite and potassium nitrite.

[0018] Optionally, the inorganic acid is selected from one of nitric acid and sulfuric acid or a combination thereof.

[0019] Optionally, the molar ratio of the nitrite to the aromatic alcohol is 1:1 to 1:1.1.

[0020] Optionally, the molar ratio of the nitrite to the inorganic acid is 1:1 to 1:1.1.

[0021] Optionally, the solvent used in the esterification reaction is selected from one of water and the aromatic alcohol or a combination thereof.

[0022] Optionally, the esterification reaction is carried out at a temperature of 10° C. to 40° C. and for a time of 1 min to 10 min.

[0023] Optionally, the step of preparing the sodium azide by subjecting the nitrite to a reduction reaction with hydrazine hydrate under alkaline conditions comprises:

[0024] mixing hydrazine hydrate and an alkaline aqueous solution to obtain a mixed solution; and

[0025] The mixed solution and the nitrite are mixed, and the nitrite is subjected to a reduction reaction with hydrazine hydrate under heating and stirring.

[0026] Optionally, the molar ratio of the hydrazine hydrate to the alkali in the alkaline aqueous solution is 1:1.05 to 1:1.5.

[0027] Optionally, the molar ratio of the hydrazine hydrate to the nitrite is 1:0.5 to 1:1.5.

[0028] Optionally, the reduction reaction is carried out at a temperature of 10° C. to 80° C. and for a time of 1 min to 60 min.

[0029] Optionally, the preparation of the nitrite ester of the aromatic alcohol using the aromatic alcohol as a raw material and the reduction reaction are independently carried out in a continuous flow reactor or a batch reactor.

[0030] Optionally, the continuous flow reactor is any one of a tank reactor, a tubular reactor and a micro-channel reactor.

[0031] Optionally, the synthesis method further comprises: after allowing the nitrite to undergo a reduction reaction with hydrazine hydrate under alkaline conditions, performing liquid-liquid phase separation on the reaction product, and separating the sodium azide in the aqueous phase from the aqueous phase, thereby obtaining the sodium azide.

[0032] Optionally, after the liquid-liquid phase separation treatment, the process further comprises using the separated aromatic alcohol as a raw material to continue preparing the nitrite ester of the aromatic alcohol. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a schematic flow chart of a method for synthesizing sodium azide provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0035] Unless the context requires otherwise, throughout the specification and claims, the term "including" is to be interpreted as having an open, inclusive meaning, that is, "including, but not limited to." In the description of the specification, the terms "one embodiment," "some embodiments," "exemplary embodiments," "exemplarily," or "some examples" are intended to indicate that specific features, structures, materials, or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representations of the above terms do not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials, or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0036] “A and / or B” includes the following three combinations: A only, B only, and a combination of A and B.

[0037] As used herein, unless otherwise specified, "one or more" means one or more than two.

[0038] As used herein, the terms "for example," "such as," "example," and "for instance" are used for descriptive purposes to indicate that the preceding and following technical solutions are related in terms of their coverage, but should not be construed as limiting the preceding technical solution or the scope of protection herein. As used herein, unless otherwise specified, "A (such as B)" means that B is a non-limiting example of A, and it should be understood that A is not limited to B.

[0039] As used herein, "optionally," "optional," and "optional" mean optional or dispensable, meaning that the option is selected from either of two parallel options: "optional" or "optional." If a technical solution contains multiple "optional" clauses, each "optional" clause is considered independent unless otherwise specified and there are no conflicts or constraints.

[0040] Herein, descriptions such as “optionally contain” and “optionally include” mean “contain or not contain”. “Optional component X” means component X is present or not, or contains or not contains the component X.

[0041] In this document, the terms "first" and "second" in "the first aspect" and "the second aspect" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features.

[0042] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0044] In this article, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0045] In this document, "at least one" means more than one, such as one, two, or more than two. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layer" means at least two layers, such as two, three, etc., unless otherwise specifically defined. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise specifically defined.

[0046] Herein, when referring to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​within the numerical interval is considered continuous and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval refers only to integers within the numerical interval, including the two endpoint integers of the numerical range, and each integer between the two endpoints, is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for broad inclusion of numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0047] In this article, unless otherwise specified, the percentage content refers to mass percentage for solid-liquid mixing and solid-solid mixing, and refers to volume percentage for liquid-liquid mixing.

[0048] In this article, percentage concentrations, unless otherwise specified, refer to final concentrations, which are the percentage of an added ingredient in the system after the ingredient is added.

[0049] As used herein, % (w / w) and wt% both refer to weight percentage, % (v / v) refers to volume percentage, and % (w / v) refers to mass volume percentage.

[0050] In this article, when it comes to temperature parameters, unless otherwise specified, both constant temperature treatment and treatment within a certain temperature range are permitted. The constant temperature treatment allows the temperature to fluctuate within the precision range controlled by the instrument.

[0051] Herein, the term "room temperature" or "normal temperature" generally refers to 4°C to 35°C, for example, 20°C±5°C.

[0052] the term

[0053] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0054] The term "alkyl" refers to a saturated hydrocarbon containing primary (normal) carbon atoms, secondary carbon atoms, tertiary carbon atoms, quaternary carbon atoms, or combinations thereof. Phrases containing this term, for example, "C1-C9 alkyl" refers to an alkyl group containing 1 to 9 carbon atoms, each occurrence of which can independently be C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl, or C9 alkyl. Suitable examples include, but are not limited to, methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, -CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-1-propyl (i-Bu, i-butyl, -CH2CH(CH3)2), 2-butyl (s-Bu, s-butyl, -CH(C H3)CH2CH3), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH3)3), 1-pentyl (n-pentyl, -CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), 2-methyl-2-butyl (-C(CH3)2CH2CH3), 3-methyl-2-butyl (-CH(CH3)CH(CH3)2), 3-methyl-1-butyl (- CH2CH2CH(CH3)2), 2-methyl-1-butyl (-CH2CH(CH3)CH2CH3), 1-hexyl (-CH2CH2CH2CH2CH2CH3), 2-hexyl (-CH(CH3)CH2CH2CH2CH3), 3-hexyl (-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl (-C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl (-CH(CH3)CH( )2), 2-methyl-3-pentyl (-CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2), 3,3-dimethyl-2-butyl (-CH(CH3)C(CH3)3 and octyl (-(CH2)7CH3).

[0055] "Aryl" refers to an aromatic hydrocarbon group derived from an aromatic ring compound by removing one or more hydrogen atoms. It can be a monocyclic aromatic group, a condensed aromatic group, or a polycyclic aromatic group. For polycyclic aromatic groups, at least one of them is an aromatic ring system. For example, "C6-C 20"Aryl" refers to an aromatic group containing 6 to 20 carbon atoms, each occurrence of which can be independently C6 aromatic, C 10 Aryl, C 14 Aryl, C 18 Aryl or C 20 Aryl. Suitable examples include, but are not limited to, benzene, biphenyl, naphthalene, anthracene, phenanthrene, perylene, triphenylene, and their derivatives. It is understood that multiple aryl groups may be interrupted by short non-aromatic units (e.g., <10% non-H atoms, such as C, N, or O atoms), specifically acenaphthene, fluorene, or 9,9-diarylfluorene, triarylamine, and diaryl ether systems, which are also included in the definition of aryl.

[0056] "Heteroaryl" means that at least one carbon atom in an aryl group is replaced by a non-carbon atom, which may be a nitrogen atom, an oxygen atom, or a sulfur atom. For example, "C3-C 10 The term "heteroaryl" refers to a heteroaryl group containing 3 to 10 carbon atoms, which, at each occurrence, is independently C3 heteroaryl, C4 heteroaryl, C5 heteroaryl, C6 heteroaryl, C7 heteroaryl or C8 heteroaryl. Suitable examples include, but are not limited to, furan, benzofuran, thiophene, benzothiophene, pyrrole, pyrazole, triazole, imidazole, oxazole, oxadiazole, thiazole, tetrazole, indole, carbazole, pyrroloimidazole, pyrrolopyrrole, thienopyrrole, thienothiophene, furopyrrole, furofuran, thienofuran, benzisoxazole, benzisothiazole, benzimidazole, pyridine, pyrazine, pyridazine, pyrimidine, triazine, quinoline, isoquinoline, o-naphthyridine, quinoxaline, phenanthridine, primidine, quinazoline and quinazolinone.

[0057] In view of the problems in the related art that sodium azide easily produces by-products during its preparation that are difficult to separate, has a slow reaction rate, and that the nitrites of small molecule fatty alcohols cause significant safety hazards and environmental pollution, some embodiments of the present application provide a method for synthesizing sodium azide, as shown in FIG1 , which includes the following steps S11 to S12:

[0058] S11, using aromatic alcohol as a raw material to prepare the nitrite ester of the aromatic alcohol;

[0059] Wherein, the aromatic alcohol can be selected from the structural formula represented by One or more compounds of the invention, wherein Ar is selected from substituted or unsubstituted C6 to C 20 Aryl and substituted or unsubstituted C3~C 10 Any of the heteroaryl groups, R is selected from n is an integer from 1 to 3;

[0060] Among them, In the embodiment, R1 and R2 are the same or different and are independently selected from any one of H and C1-C3 alkyl, and the substituted C6-C 20 Aryl and substituted C3~C 10 The substituents in the heteroaryl group are independently selected from C1 to C9 alkyl groups, and * represents the connection site between Ar and R.

[0061] Wherein, when the above Ar is selected from C6~C 20 When the aryl group is an aryl group, the aryl group can be phenyl, p-methylphenyl, phenanthrenyl, etc., when the above Ar is selected from C3 to C 10 When the heteroaryl group is a heteroaryl group, the heteroaryl group can be exemplified by 4-pyridyl, 3-pyridyl, 2-thienyl, etc. Here, the above-mentioned aromatic alcohol can be purchased through commercial channels or obtained by self-production. The embodiment of the present application does not specifically limit its acquisition method.

[0062] Similar to the preparation of nitrites of small molecule fatty alcohols using small molecule fatty alcohols as raw materials, the nitrites of aromatic alcohols prepared using aromatic alcohols as raw materials provided in the embodiments of the present application can also be prepared through similar reactions.

[0063] For example, an aromatic alcohol can be subjected to an esterification reaction with a nitrite under acidic conditions to prepare a nitrite ester of the aromatic alcohol. The specific reaction equation can be expressed as:

[0064] S12. Under alkaline conditions, a reduction reaction is performed between nitrite and hydrazine hydrate to prepare sodium azide. The specific reaction equation can be expressed as:

[0065] In the synthesis method of sodium azide provided in the embodiment of the present application, the nitrite of the aromatic alcohol is prepared by using an aromatic alcohol instead of a small molecule fatty alcohol as a raw material. Compared with the related art in which a small molecule fatty alcohol is used as a raw material to prepare the nitrite of the small molecule fatty alcohol, in the reduction reaction of S12, nitrite and hydrazine hydrate, on the one hand, the nitrite of the aromatic alcohol makes the transition state more stable through the conjugation effect of the benzene ring, reduces the activation energy of the reaction, significantly increases the reaction rate, thereby shortening the reaction time and greatly improving the production efficiency; on the other hand, compared with the nitrite of the small molecule fatty alcohol, which is dissolved in the aqueous phase and easily hydrolyzed to form a nitrite by-product, the nitrite of the aromatic alcohol provided in the embodiment of the present application is The solubility in the aqueous phase is extremely low, which can significantly inhibit the hydrolysis of the nitrite ester of the aromatic alcohol (for example, in an alkaline aqueous solution of sodium hydroxide, the hydrolysis rate of the nitrite ester of the aromatic alcohol is less than 2%), thereby reducing the generation of nitrite by-products. Moreover, since the solubility of the aromatic alcohol in the aqueous phase is extremely low, there is no need to collect the aromatic alcohol in the aqueous phase, which can reduce the separation energy consumption. On the other hand, compared with the nitrite ester of small molecule fatty alcohols, the nitrite ester of the aromatic alcohol has a higher boiling point, for example, it can reach above 150°C, so the partial pressure in the gas phase space is lower, reducing the emission of VOCs, and it is not easy to decompose in the gas phase space to produce highly active free radicals, thereby improving the safety and stability of the reaction and reducing safety hazards.

[0066] In some embodiments, n is equal to 1, and R1 and R2 are selected from H or methyl, and the substituent when substituted is selected from methyl or ethyl.

[0067] In these embodiments, on one hand, the aromatic alcohol is a monohydric alcohol with a low melting point and is easy to handle; on the other hand, the aromatic alcohol is relatively cheap and easily available.

[0068] In some embodiments, the aromatic alcohol comprises one or more of the following structural formulas:

[0069] In these embodiments, is benzyl alcohol, 1-phenylethanol, It is 4-methylbenzyl alcohol. These aromatic alcohols are more commonly used and are easy to obtain.

[0070] The reaction conditions of the esterification reaction are not specifically limited. As long as the aromatic alcohol and sodium nitrite can undergo an esterification reaction under acidic conditions, all reaction conditions are within the scope of protection of this application.

[0071] In some embodiments, S11, using aromatic alcohol as a raw material to prepare nitrite ester of aromatic alcohol, may include:

[0072] Aromatic alcohols are reacted with nitrites in the presence of inorganic acids to produce nitrites.

[0073] In these embodiments, the inorganic acid is highly acidic and nonvolatile, allowing it to rapidly react with nitrite to form nitrous acid. This nitrous acid then undergoes an esterification reaction with the aromatic alcohol to form the nitrite ester of the aromatic alcohol. This process is fast and highly selective, resulting in complete conversion of the nitrite and rapid phase separation of the oil and water phases after completion of the reaction.

[0074] In some embodiments, the nitrite is sodium nitrite or potassium nitrite.

[0075] In some embodiments, the inorganic acid includes nitric acid and sulfuric acid.

[0076] In some embodiments, the molar ratio of nitrite to aromatic alcohol is 1:1 to 1:1.1.

[0077] In some embodiments, the molar ratio of nitrite to inorganic acid is 1:1 to 1:1.1.

[0078] In some embodiments, the solvent used in the esterification reaction includes: water and aromatic alcohol or a combination of both.

[0079] In some embodiments, the esterification reaction temperature is 10° C. to 40° C., and the reaction time is 1 min to 10 min.

[0080] In these embodiments, sodium nitrite or potassium nitrite is inexpensive, readily available, and relatively stable at room temperature. Nitric acid and sulfuric acid are highly acidic and, upon addition, instantly provide a large amount of hydrogen ions, thereby rapidly converting nitrite into nitrous acid, thereby initiating an esterification reaction between nitrous acid and aromatic alcohol. To completely convert nitrite, a slight excess of inorganic acid is generally required, and thus a molar ratio of nitrite to inorganic acid is employed of 1:1 to 1:1.1. To completely consume the generated nitrous acid by the aromatic alcohol, a slight excess of aromatic alcohol is generally required, and thus a molar ratio of nitrite to aromatic alcohol is employed of 1:1 to 1:1.1.

[0081] In some embodiments, under alkaline conditions, reducing a nitrite with hydrazine hydrate to prepare sodium azide may include:

[0082] mixing hydrazine hydrate and an alkaline aqueous solution to obtain a mixed solution; and

[0083] The mixed solution and nitrite are mixed, and the nitrite and hydrazine hydrate are subjected to a reduction reaction under heating and stirring.

[0084] In these embodiments, the alkaline aqueous solution can be an aqueous sodium hydroxide solution, which has two functions: first, it quickly converts the intermediate product generated by the reaction of nitrite and hydrazine hydrate into sodium azide, preventing the decomposition of nitrite into gaseous by-products; and second, it reduces the hydrogen ion concentration in water and converts hydrogen azide into sodium azide.

[0085] In some embodiments, the molar ratio of hydrazine hydrate to the base in the alkaline aqueous solution is 1:1.05 to 1:1.5.

[0086] In some embodiments, the molar ratio of hydrazine hydrate to nitrite is 1:0.5 to 1:1.5.

[0087] In some embodiments, the reduction reaction temperature is 10° C. to 80° C., and the time is 1 min to 60 min.

[0088] In these embodiments, the alkaline aqueous solution can be exemplified by a slight sodium hydroxide aqueous solution. Sodium hydroxide not only participates in the reaction but also stabilizes the product sodium azide. By slightly overdosing sodium hydroxide, the formation of highly toxic and explosive hydrazine acid can be avoided. By limiting the molar ratio of hydrazine hydrate to nitrite within the range of 1:0.5 to 1:1.5, the reaction selectivity can be improved while avoiding a large amount of hydrazine hydrate residue, thereby reducing the difficulty of removing hydrazine hydrate. By controlling the reduction reaction temperature to 10°C to 100°C and the time to 1 min to 60 min, the reaction time can be further reduced while ensuring the reaction selectivity, thereby improving efficiency.

[0089] In some embodiments, the preparation of the nitrite ester of the aromatic alcohol using the aromatic alcohol as a raw material and the above-mentioned reduction reaction are independently carried out in a continuous flow reactor or a batch reactor.

[0090] In these embodiments, the preparation of the nitrite ester of the aromatic alcohol using the aromatic alcohol as the raw material and the above-mentioned reduction reaction are two separate steps that can be carried out in a continuous flow reactor or a batch reactor.

[0091] When the preparation of the nitrite ester of the aromatic alcohol using the aromatic alcohol as the raw material and the above-mentioned reduction reaction are carried out in a continuous flow reactor, these two steps can also be carried out continuously.

[0092] In some embodiments, the continuous flow reactor is any one of a tank reactor, a tubular reactor, and a microchannel reactor.

[0093] The batch reactor may be a batch reactor.

[0094] In some embodiments, the synthesis method further comprises: after allowing the nitrite to undergo a reduction reaction with hydrazine hydrate under alkaline conditions, performing liquid-liquid phase separation on the reaction product, and separating the sodium azide in the aqueous phase from the aqueous phase to obtain sodium azide.

[0095] In these embodiments, after a nitrite ester is reduced with hydrazine hydrate under alkaline conditions, the reaction product can be separated into an upper organic phase and a lower aqueous phase. The aqueous phase can be separated by liquid-liquid phase separation, and the sodium azide in the aqueous phase can be separated and purified to obtain sodium azide of high purity. In the above synthesis method, since the solubility of the nitrite ester of the aromatic alcohol in the aqueous phase is extremely low, the hydrolysis of the nitrite ester of the aromatic alcohol can be significantly inhibited, thereby reducing the formation of nitrite by-products. Therefore, the purity of the sodium azide in the aqueous phase is relatively high, and sodium azide with a purity greater than 99% can be obtained through simple separation and purification.

[0096] In some embodiments, after the liquid-liquid phase separation treatment, the separated aromatic alcohol is further used as a raw material for preparing nitrite esters of aromatic alcohol.

[0097] In these embodiments, after a reduction reaction between nitrite and hydrazine hydrate under alkaline conditions, the reaction product can be phase-separated into an upper organic phase and a lower aqueous phase. Most of the aromatic alcohol is present in the upper organic phase. The aromatic alcohol can be separated by liquid-liquid phase separation. The purity of the aromatic alcohol in the upper organic phase is greater than 95%. Therefore, it can be directly used to continue to prepare nitrite of aromatic alcohol without separation and purification, thereby realizing the recycling of aromatic alcohol and reducing the waste of alcohol raw materials.

[0098] In order to objectively evaluate the technical effects of the embodiments of the present application, the present application will be described in detail and exemplarily through the following embodiments.

[0099] In the following examples, all raw materials can be purchased commercially, and in order to maintain the reliability of the experiments, the raw materials used in the following examples have the same physical and chemical parameters or are prepared by the same processing method.

[0100] Example 1

[0101] The synthesis method of sodium azide in Example 1 is as follows:

[0102] (1) A 35 wt% aqueous sodium nitrite solution and benzyl alcohol are mixed and dispersed in a batch reactor, and a 65% mass fraction aqueous nitric acid solution is added. The mixture is reacted at 20°C for 10 minutes. After the reaction is completed, the phases are separated, and the upper oil phase is a 90 wt% pure benzyl alcohol nitrite solution, and the remaining component is the benzyl alcohol raw material. In the above reaction, the molar ratio of sodium nitrite to benzyl alcohol is 1:1.05, and the molar ratio of sodium nitrite to nitric acid is 1:1.02.

[0103] (2) 85% by mass of hydrazine hydrate and 30% by mass of sodium hydroxide aqueous solution are mixed in a batch reactor, and the 90% by mass of nitrite synthesized in step (1) is added dropwise at a constant rate for 10 minutes. After the addition is completed, the mixture is reacted at 40° C. for 10 minutes. After the reaction is completed, the phases are separated. The lower aqueous phase is a 26.5% by mass sodium azide solution containing 0.3% by mass of sodium nitrite (the sodium nitrite is generated by hydrolysis of nitrite in sodium hydroxide solution). After separation and purification, a sodium azide product with a purity greater than 99% is obtained, with a yield of 96% and a hydrolysis rate of nitrite of 1.1%. The upper oil phase contains benzyl alcohol with a purity of 94%. Nitrite can be synthesized again through step (1) without separation and purification, and recycled. In the above reaction, the molar ratio of hydrazine hydrate to sodium hydroxide is 1:1.1, and the molar ratio of hydrazine hydrate to nitrite is 1:1.1; the specific reaction parameters are shown in Table 1 below.

[0104] Example 2

[0105] The synthesis method of sodium azide in Example 2 is basically the same as the synthesis method of sodium azide in Example 1, except that:

[0106] In step (1), the nitrite used is potassium nitrite, and the inorganic acid used is sulfuric acid with a mass fraction of 60%.

[0107] In step (2), the molar ratio of hydrazine hydrate to nitrite was 1:1.5, and the reaction time was 60 min. The final yield of sodium azide was 96%, and the hydrolysis rate of nitrite was 1.9%. The specific reaction parameters are shown in Table 1 below.

[0108] Example 3

[0109] The synthesis method of sodium azide in Example 3 is basically the same as the synthesis method of sodium azide in Example 1, except that:

[0110] In step (1), the esterification reaction temperature is 40° C. and the reaction time is 1 min. In the above reaction, the molar ratio of sodium nitrite to benzyl alcohol is 1:1.1, and the molar ratio of sodium nitrite to nitric acid is 1:1.1.

[0111] In step (2), the molar ratio of hydrazine hydrate to nitrite was 1:0.5, the nitrite was added to the reactor all at once, and the reaction time was 1 min. The final yield of sodium azide was 49%, and the hydrolysis rate of nitrite was 0.3%. The specific reaction parameters are shown in Table 1 below. In this example, the molar amount of benzyl alcohol nitrite added was only 50% of that of hydrazine hydrate. Therefore, the yield of sodium azide calculated based on hydrazine hydrate was low. If calculated based on nitrite, the yield of sodium azide was 98%.

[0112] Example 4

[0113] The synthesis method of sodium azide in Example 4 is basically the same as the synthesis method of sodium azide in Example 1, except that:

[0114] In step (1), the esterification reaction temperature is 10° C. and the time is 10 min.

[0115] In step (2), the molar ratio of hydrazine hydrate to sodium hydroxide was 1:1.2. The final yield of sodium azide was 95%, and the hydrolysis rate of nitrite was 1.4%. The specific reaction parameters are shown in Table 1 below.

[0116] Example 5

[0117] The synthesis method of sodium azide in Example 5 is basically the same as the synthesis method of sodium azide in Example 1, except that:

[0118] In step (2), the molar ratio of hydrazine hydrate to sodium hydroxide was 1:1.5. The final yield of sodium azide was 94%, and the hydrolysis rate of nitrite was 1.8%. The specific reaction parameters are shown in Table 1 below. As shown in Examples 4 and 5, increasing the molar amount of sodium hydroxide can improve the stability of sodium azide, but will also increase the hydrolysis rate of nitrite.

[0119] Example 6

[0120] The synthesis method of sodium azide in Example 6 is basically the same as the synthesis method of sodium azide in Example 1, except that:

[0121] In step (2), the molar ratio of hydrazine hydrate to sodium hydroxide was 1:1.05, the reaction temperature was 10°C, and the reaction time was 60 min. The final yield of sodium azide was 97%, and the hydrolysis rate of nitrite was 0.8%. The specific reaction parameters are shown in Table 1 below. Compared with Example 1, lowering the temperature was beneficial for increasing the yield and reducing the hydrolysis rate, but the reaction time was extended by 40 min compared with Example 1.

[0122] Example 7

[0123] The synthesis method of sodium azide in Example 7 is basically the same as the synthesis method of sodium azide in Example 1, except that:

[0124] In step (2), the molar ratio of hydrazine hydrate to sodium hydroxide was 1:1.05, the reaction temperature was 80°C, and the reaction time was 15 min. The final yield of sodium azide was 86%, and the hydrolysis rate of nitrite was 1.9%. The specific reaction parameters are shown in Table 1 below. Compared with Example 1, increasing the reaction temperature was beneficial to increasing the reaction rate, but the yield decreased and the hydrolysis rate increased.

[0125] Example 8

[0126] The synthesis method of sodium azide in Example 8 is basically the same as the synthesis method of sodium azide in Example 1, except that:

[0127] In step (1), the reaction is carried out in a continuous tubular reactor at a reaction temperature of 20° C. and a residence time of 1 minute. After completion of the reaction, the yield of benzyl nitrite is 96% and the purity is 90 wt%.

[0128] In step (2), the reduction reaction is carried out in a continuous reactor, and the nitrite synthesized in step (1) with a mass fraction of 90% is added to the mixed solution of hydrazine hydrate and sodium hydroxide in three batch additions; the final yield of sodium azide is 91%, and the hydrolysis rate of nitrite is 1.1%; the specific reaction parameters are shown in Table 1 below.

[0129] Example 9

[0130] The synthesis method of sodium azide in Example 9 is basically the same as the synthesis method of sodium azide in Example 1, except that:

[0131] In step (1), benzyl alcohol was replaced with 1-phenylethanol; in step (2), 90% by mass of the nitrite synthesized in step (1) was added to a mixed solution of hydrazine hydrate and sodium hydroxide; the final yield of sodium azide was 89%, and the hydrolysis rate of the nitrite was 0.9%; the specific reaction parameters are shown in Table 1 below. Compared with Example 1, replacing the raw material from benzyl alcohol with 1-phenylethanol can reduce the hydrolysis rate of the nitrite, but it also reduces the yield of sodium azide.

[0132] Example 10

[0133] The synthesis method of sodium azide in Example 10 is basically the same as the synthesis method of sodium azide in Example 1, except that:

[0134] In step (1), 4-methylbenzyl alcohol was used instead of benzyl alcohol; in step (2), 90% by mass of the nitrite synthesized in step (1) was added to a mixed solution of hydrazine hydrate and sodium hydroxide; the final yield of sodium azide was 87%, and the hydrolysis rate of the nitrite was 1%; the specific reaction parameters are shown in Table 1 below. Compared with Example 1, replacing the raw material from benzyl alcohol with 4-methylbenzyl alcohol can reduce the hydrolysis rate of the nitrite, but it also reduces the yield of sodium azide.

[0135] Comparative Example 1

[0136] The synthesis method of sodium azide in Comparative Example 1 is substantially the same as that in Example 1, except that:

[0137] In step (1), a small molecule fatty alcohol, isopropyl alcohol, is used to replace benzyl alcohol to synthesize isopropyl nitrite.

[0138] In step (2), 90% by mass of isopropyl nitrite synthesized in step (1) is added to a mixed solution of hydrazine hydrate and sodium hydroxide; the final yield of sodium azide is only 6.2%, and the hydrolysis rate of nitrite is 3.1%. The specific reaction parameters are shown in Table 1 below. Compared with Example 1, after replacing the raw material from benzyl alcohol with isopropyl alcohol, the reaction rate is sharply reduced, resulting in a sodium azide yield of 96% to 6.2% within 20 minutes; and the nitrite hydrolysis rate is increased, reaching 3.1% when the nitrite conversion rate is only 10%.

[0139] Table 1

[0140] As shown in Table 1, the aromatic alcohol provided in the embodiment of the present application can be applied to batch reaction or continuous reaction. Compared with the synthesis of sodium azide using isopropyl alcohol as a raw material in Comparative Example 1, the intermediate product nitrite is synthesized by first esterifying the aromatic alcohol with sodium nitrite in the presence of an inorganic acid, and then the nitrite and hydrazine hydrate are reduced. On the one hand, the nitrite (such as benzyl nitrite) can make the transition state more stable through the conjugation effect of the benzene ring, reduce the activation energy of the reaction, and significantly increase the reaction rate, thereby shortening the reaction time of the intermittent stirring process from several hours to less than 20 minutes, greatly improving the production efficiency; and if a continuous reaction process is used, the volume of the reactor can be greatly reduced. Secondly, since the solubility of the nitrite of the aromatic alcohol in the aqueous phase is extremely low, the hydrolysis side reaction can be significantly suppressed, so that the hydrolysis rate of the nitrite is controlled to be less than 2%; and the concentration of the aromatic alcohol in the aqueous phase after the reaction is extremely low, there is no need to recover the alcohol in the aqueous phase, which greatly reduces the separation energy consumption. Thirdly, the boiling point of nitrite esters of aromatic alcohols is usually higher than 150°C, and the partial pressure in the gas phase is extremely low, which is beneficial to reducing VOCs emissions and improving process safety.

[0141] In summary, the embodiments of the present application can solve the problems of low selectivity, low efficiency and low safety in the sodium azide synthesis process in the related technology by replacing the raw materials from small molecule fatty alcohols with aromatic alcohols, while also reducing the difficulty and energy consumption of separating the alcohol raw materials, and can directly recycle the separated aromatic alcohols to achieve energy saving and efficiency improvement, so it has good application prospects.

[0142] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0143] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A method for synthesizing sodium azide, characterized in that, Comprising: Preparing the nitrite of the aromatic alcohol using the aromatic alcohol as a raw material; And Under alkaline conditions, subjecting the nitrite to a reduction reaction with hydrazine hydrate to prepare the sodium azide; Among them, the aromatic alcohol is selected from those represented by the structural formula one or more of the compounds, wherein Ar is selected from substituted or unsubstituted C6-C 20 aryl and substituted or unsubstituted C3-C 10 any one of heteroaryl, and R is selected from n is an integer from 1 to 3; Among them, in wherein R1 and R2 are the same or different and are each independently selected from any one of H and C1-C3 alkyl, and the substituted C6-C 20 aryl and substituted C3-C 10 substituents in heteroaryl are independently selected from C1-C9 alkyl, and * represents the bonding site of Ar and R.

2. The synthesis method according to claim 1, wherein n is equal to 1, and R1 and R2 are selected from H or methyl, and the substituents of the substituted C6-C 20 aryl and the substituted C3-C 10 substituents in heteroaryl are independently selected from methyl or ethyl.

3. The synthesis method according to claim 1 or 2, characterized in that, Ar is selected from any one of phenyl, p-methylphenyl, phenanthryl, 4-pyridyl, 3-pyridyl, and 2-thienyl.

4. The synthesis method according to any one of claims 1 to 3, characterized in that, The aromatic alcohol is selected from one or more of the following structural formulas:

5. The synthesis method according to any one of claims 1 to 4, characterized in that, The preparing the nitrite of the aromatic alcohol using the aromatic alcohol as a raw material includes: Subjecting the aromatic alcohol to an esterification reaction with a nitrite in the presence of an inorganic acid to form the nitrite.

6. The synthesis method according to claim 5, characterized in that, The nitrite is selected from one or a combination of sodium nitrite and potassium nitrite.

7. The synthesis method according to claim 5 or 6, characterized in that The inorganic acid is selected from one or a combination of nitric acid and sulfuric acid.

8. The synthesis method according to any one of claims 5 to 7, characterized in that, The molar ratio of the nitrite to the aromatic alcohol is 1:1 to 1:1.

1.

9. The synthesis method according to any one of claims 5 to 8, characterized in that, The molar ratio of the nitrite to the inorganic acid is 1:1 to 1:1.

1.

10. The synthesis method according to any one of claims 5 to 9, characterized in that, The solvent used in the esterification reaction is selected from one or a combination of water and the aromatic alcohol.

11. The synthesis method according to any one of claims 5 to 10, characterized in that, The temperature of the esterification reaction is 10°C to 40°C, and the time is 1 min to 10 min.

12. The synthesis method according to any one of claims 1 to 11, characterized in that, The under alkaline conditions, subjecting the nitrite to a reduction reaction with hydrazine hydrate to prepare the sodium azide includes: Mixing hydrazine hydrate and an alkaline aqueous solution to obtain a mixed solution; and Mixing the mixed solution and the nitrite, and subjecting the nitrite to a reduction reaction with hydrazine hydrate under heating and stirring.

13. The synthesis method according to claim 12, characterized in that, The molar ratio of hydrazine hydrate to the base in the alkaline aqueous solution is 1:1.05 to 1:1.

5.

14. The synthesis method according to claim 12 or 13, characterized in that, The molar ratio of hydrazine hydrate to the nitrite is 1:0.5 to 1:1.

5.

15. The synthesis method according to any one of claims 12 to 14, characterized in that, The temperature of the reduction reaction is 10°C to 80°C, and the time is 1 min to 60 min.

16. The synthesis method according to any one of claims 12 to 15, characterized in that The alkaline aqueous solution is a sodium hydroxide aqueous solution.

17. The synthesis method according to any one of claims 1 to 16, characterized in that The preparing the nitrite of the aromatic alcohol using the aromatic alcohol as a raw material and the reduction reaction are each independently carried out in a continuous flow reactor or a batch reactor.

18. The synthesis method according to claim 17, characterized in that, The continuous flow reactor is any one of a kettle reactor, a tubular reactor, and a microchannel reactor.

19. The synthesis method according to any one of claims 1 to 18, characterized in that, The synthesis method further includes: after subjecting the nitrite to a reduction reaction with hydrazine hydrate under alkaline conditions, performing liquid-liquid phase separation on the reaction product, and separating the sodium azide in the aqueous phase from the aqueous phase to obtain the sodium azide.

20. The synthesis method according to claim 19, characterized in that, After the liquid-liquid phase separation treatment, it further includes using the separated aromatic alcohol as a raw material to continue preparing the nitrite of the aromatic alcohol.

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