Synthesis method of sodium azide

Abstract

The present application relates to the field of chemical and chemical technology, and in particular to a method for synthesizing sodium azide. It can solve the problems of long reaction time, low production efficiency, many by-products, large pollution emissions, and high safety hazards in the sodium azide preparation process in the related technology. A method for synthesizing sodium azide, comprising: using aromatic alcohol as a raw material to prepare nitrite ester of aromatic alcohol; under alkaline conditions, allowing nitrite ester to undergo a reduction reaction with hydrazine hydrate to prepare sodium azide; wherein the aromatic alcohol comprises: one or more compounds represented by the structural formula: #imgabs0#, wherein Ar is selected from the following substituted or unsubstituted C6~C 20 Aryl and substituted or unsubstituted C3~C 10 Any one of the heteroaryl groups, R is selected from #imgabs1#n is an integer of 1 to 3; wherein, in #imgabs2#, R1 and R2 are the same or different and are independently selected from any one of H and C1 to C3 alkyl groups; when Ar is selected from substituted C6 to C 20 Aryl or substituted C3~C 10 In the case of heteroaryl, the substituted substituent is selected from C1-C9 alkyl, and * indicates the attachment site.

Description

Technical Field

[0001] The present application relates to the field of chemical engineering technology, and in particular to a method for synthesizing sodium azide. Background Art

[0002] Sodium azide is an important raw material for the construction of high-energy chemicals and is also the inorganic azide salt with the largest amount and the widest application. For example, sodium azide can not only be used as a filler for automobile airbags and emergency inflatable slides on passenger planes, but also has rich and active chemical properties. It is a precursor for the synthesis of various organic azides and has irreplaceable application value in the fields of chemistry, materials and biology.

[0003] In the related art, currently, small molecular fatty alcohols are mainly used as raw materials to prepare the nitrites of these small molecular fatty alcohols, and then, the nitrites of these small molecular fatty alcohols are reduced with hydrazine hydrate under alkaline conditions to synthesize sodium azide. In the above reduction reaction, there are at least the following problems: first, the nitrites of these small molecular fatty alcohols have high solubility in the aqueous phase and are easily hydrolyzed in the alkaline aqueous solution to generate sodium nitrite, and the hydrolysis rate can often reach more than 20%, which not only causes a waste of raw materials, but also increases a large amount of by-product sodium nitrite, and increases the separation cost of sodium azide and by-product sodium nitrite; second, in order to In order to suppress side reactions, nitrite is usually added dropwise for feeding, and the reaction time can be several hours or even more than ten hours, which is inefficient. Thirdly, the nitrites of these small molecular fatty alcohols have a low boiling point, a high partial pressure in the gas phase space during the reaction, and are easily decomposed to produce highly active free radicals, which are extremely dangerous intermediates. What is more serious is that the product sodium azide itself is an extremely explosive substance, which will bring huge safety hazards. In addition, industrial production will inevitably cause the emission of volatile organic compounds (VOCs), and nitrites will quickly decompose into greenhouse gases such as nitric oxide and nitrous oxide in the atmosphere, which will pollute the environment. Summary of the invention

[0004] Based on this, it is necessary to provide a synthesis method of sodium azide to solve the problems in the related art that sodium azide is prone to produce by-products that are difficult to separate during the preparation process, the reaction speed is slow, and the nitrites of small molecular fatty alcohols cause greater safety hazards and environmental pollution.

[0005] The present application provides a method for synthesizing sodium azide, comprising:

[0006] Using aromatic alcohol as a raw material to prepare the nitrite ester of the aromatic alcohol;

[0007] Under alkaline conditions, allowing the nitrite to undergo a reduction reaction with hydrazine hydrate to prepare the sodium azide;

[0008] Wherein, the aromatic alcohol includes: the structural formula is expressed as: 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;

[0009] 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. When Ar is selected from substituted C6-C 20 Aryl and substituted C3~C 10 When any of the heteroaryl groups is present, the substituted substituent is selected from C1 to C9 alkyl groups, and * indicates the attachment site.

[0010] Optionally, 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.

[0011] Optionally, the aromatic alcohol comprises: one or more of the following structural formulas:

[0012]

[0013] Optionally, the method of using aromatic alcohol as a raw material to prepare the nitrite ester of the aromatic alcohol comprises:

[0014] The aromatic alcohol and nitrite are subjected to an esterification reaction in the presence of an inorganic acid to generate the nitrite.

[0015] Optionally, the esterification reaction satisfies at least one of the following conditions:

[0016] (1) The nitrite is sodium nitrite or potassium nitrite;

[0017] (2) The inorganic acid includes nitric acid and sulfuric acid;

[0018] (3) The molar ratio of the nitrite to the aromatic alcohol is 1:1 to 1:1.1;

[0019] (4) The molar ratio of the nitrite to the inorganic acid is 1:1 to 1:1.1;

[0020] (5) The solvent used in the esterification reaction includes: water and one or a combination of the aromatic alcohol;

[0021] (6) The temperature of the esterification reaction is 10°C to 40°C, and the time is 1 min to 10 min.

[0022] Optionally, the step of preparing the sodium azide by subjecting the nitrite to a reduction reaction with hydrazine hydrate under alkaline conditions comprises:

[0023] mixing hydrazine hydrate and an alkaline aqueous solution to obtain a mixed solution;

[0024] The mixed solution and the nitrite are mixed, and the nitrite is subjected to a reduction reaction with hydrazine hydrate under heating and stirring.

[0025] Optionally, the reduction reaction satisfies at least one of the following conditions:

[0026] (1) The molar ratio of the hydrazine hydrate to the alkali in the alkaline aqueous solution is 1:1.05 to 1:1.5;

[0027] (2) the molar ratio of the hydrazine hydrate to the nitrite is 1:0.5 to 1:1.5;

[0028] (3) 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 by using the aromatic alcohol as a raw material and the reduction reaction are carried out independently 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 microchannel reactor.

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

[0033] Compared with the related art, this application has the following technical effects:

[0034] In the synthesis method of sodium azide provided in the embodiment of the present application, aromatic alcohol is used as a raw material to prepare the nitrite of aromatic alcohol instead of small molecule fatty alcohol. Compared with the use of small molecule fatty alcohol as a raw material to prepare the nitrite of small molecule fatty alcohol in the related art, in the reduction reaction of nitrite and hydrazine hydrate, on the one hand, the nitrite of aromatic alcohol makes the transition state more stable through the conjugation effect of the benzene ring, reduces the activation energy of the reaction, and 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 small molecule fatty alcohol that is dissolved in the aqueous phase and easily hydrolyzed to generate nitrite by-products, the aromatic alcohol provided in the embodiment of the present application The solubility of the nitrite in the aqueous phase is extremely low, which can significantly inhibit the hydrolysis of the nitrite of the aromatic alcohol (for example, the hydrolysis rate of the nitrite 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 of small molecular fatty alcohols, the nitrite 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, which reduces 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.

[0035] 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 of separating the alcohol raw materials and energy consumption, and can directly recycle the separated aromatic alcohols to achieve energy saving and efficiency improvement, so it has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic flow chart of a method for synthesizing sodium azide provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0038] Unless the context requires otherwise, throughout the specification and claims, the term "including" is to be interpreted as 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" and the like 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 representation of the above terms does 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.

[0039] “A and / or B” includes the following three combinations: A only, B only, and a combination of A and B.

[0040] Herein, unless otherwise specified, "one or more" means one or more than or equal to two.

[0041] In this document, "for example", "such as", "example", "for example", etc. are used for descriptive purposes, indicating that the previous and subsequent technical solutions are related in terms of the content covered, but should not be understood as limiting the previous technical solution, nor can they be understood as limiting the scope of protection of this document. In this document, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0042] In this article, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel options of "yes" or "no". If there are multiple "options" in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "option" is independent.

[0043] Herein, descriptions such as "optionally contain", "optionally include", etc., mean "contain or not contain". "Optional component X" means component X exists or does not exist, or means containing or not containing the component X.

[0044] In this document, the terms "first", "second", etc. in "the first aspect", "the second aspect", etc. 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.

[0045] 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 a central 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 a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0046] 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 belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0047] 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.

[0048] In this document, "at least one" means more than one, such as one, two and more than two. "Multiple" or "several" means at least two, such as two, three, etc., and "multilayer" means at least two layers, such as two layers, three layers, etc., unless otherwise clearly and specifically defined. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0049] Herein, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be 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 the numerical interval only refers to the integers in 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 combined. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all sub-ranges 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 broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0050] In this article, the percentage content, unless otherwise specified, refers to mass percentage for solid-liquid mixing and solid-solid mixing, and volume percentage for liquid-liquid mixing.

[0051] In this article, when it comes to percentage concentration, unless otherwise specified, it refers to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of the component.

[0052] Herein, %(w / w) and wt% both refer to weight percentage, %(v / v) refers to volume percentage, and %(w / v) refers to mass volume percentage.

[0053] In this article, when it comes to temperature parameters, unless otherwise specified, both constant temperature treatment and treatment within a certain temperature range are allowed. The constant temperature treatment allows the temperature to fluctuate within the accuracy range of instrument control.

[0054] Herein, the term "room temperature" or "normal temperature" generally refers to 4°C to 35°C, for example, 20°C±5°C.

[0055] the term

[0056] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0057] The term "alkyl" refers to a saturated hydrocarbon containing primary (normal) carbon atoms, or secondary carbon atoms, or tertiary carbon atoms, or quaternary carbon atoms, or a combination thereof. Phrases containing this term, for example, "C1-C9 alkyl" refers to an alkyl containing 1 to 9 carbon atoms, and each occurrence may be independently 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).

[0058] "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 rings, at least one 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 derivatives thereof. It is understood that multiple aromatic groups may also be interrupted by short non-aromatic units (e.g., <10% non-H atoms, such as C, N or O atoms), such as acenaphthene, fluorene, or 9,9-diarylfluorene, triarylamine, diaryl ether system should also be included in the definition of aromatic group.

[0059] "Heteroaryl" means that at least one carbon atom in an aryl group is replaced by a non-carbon atom, such as a nitrogen atom, an oxygen atom, or a sulfur atom. 10 The term "heteroaryl" refers to a heteroaryl group containing 3 to 10 carbon atoms, which, at each occurrence, may be 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, furanofuran, thienofuran, benzisoxazole, benzisothiazole, benzimidazole, pyridine, pyrazine, pyridazine, pyrimidine, triazine, quinoline, isoquinoline, o-naphthyridine, quinoxaline, phenanthridine, primary idine, quinazoline and quinazolinone.

[0060] Based on the above technical problems, some embodiments of the present application provide a method for synthesizing sodium azide, such as Figure 1 As shown, the method includes the following steps S11) to S12):

[0061] S11), using aromatic alcohol as a raw material to prepare the nitrite ester of the aromatic alcohol;

[0062] Wherein, the aromatic alcohol may include: 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;

[0063] 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. When Ar is selected from substituted C6-C 20 Aryl and substituted C3~C 10When any of the heteroaryl groups is present, the substituted substituent is selected from C1 to C9 alkyl groups, and * indicates the attachment site.

[0064] Wherein, when the above Ar is selected from C6~C 20 When the aryl group is an aryl group, the aryl group may be phenyl, p-methylphenyl, phenanthryl, etc., and 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 aromatic alcohol can be purchased through commercial channels or obtained by self-production, and the embodiment of the present application does not specifically limit its acquisition method.

[0065] Similar to the preparation of nitrites of small molecule fatty alcohols using small molecule fatty alcohols as raw materials, the preparation of nitrites of aromatic alcohols using aromatic alcohols as raw materials provided in the embodiments of the present application can also be prepared by a similar reaction.

[0066] For example, aromatic alcohol and nitrite can be subjected to esterification reaction under acidic conditions to prepare nitrite ester of aromatic alcohol. The specific reaction equation can be expressed as:

[0067]

[0068] S12), under alkaline conditions, nitrite and hydrazine hydrate are subjected to reduction reaction to prepare sodium azide. The specific reaction equation can be expressed as:

[0069]

[0070] In the synthesis method of sodium azide provided in the embodiment of the present application, aromatic alcohols are used as raw materials to prepare nitrites of aromatic alcohols instead of small molecule fatty alcohols. Compared with the use of small molecule fatty alcohols as raw materials to prepare nitrites of small molecule fatty alcohols in the related art, in S12), in the reduction reaction of nitrites with hydrazine hydrate, on the one hand, the nitrites of aromatic alcohols 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 and greatly improving the production efficiency; on the other hand, compared with the nitrites of small molecule fatty alcohols that are dissolved in the aqueous phase and easily hydrolyzed to form nitrite by-products, the nitrites of aromatic alcohols provided in the embodiment of the present application are 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, thereby reducing 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, therefore, 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.

[0071] In some embodiments, the above 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.

[0072] In these embodiments, on one hand, the aromatic alcohol is a monohydric alcohol, which has a relatively low melting point and is easy to handle; on the other hand, the aromatic alcohol is relatively cheap and readily available.

[0073] In some embodiments, the aromatic alcohol comprises: one or more of the following structural formulas:

[0074] In these embodiments, is benzyl alcohol, 1-phenylethanol, It is 4-methylbenzyl alcohol. These aromatic alcohols are more commonly used and are convenient and easy to obtain.

[0075] The reaction conditions of the above esterification reaction are not specifically limited, and all reaction conditions that can cause the aromatic alcohol and sodium nitrite to undergo esterification reaction under acidic conditions are within the protection scope of the present application.

[0076] In some embodiments, S11), using aromatic alcohol as a raw material to prepare nitrite of aromatic alcohol may include:

[0077] The aromatic alcohol and nitrite are subjected to an esterification reaction in the presence of an inorganic acid to generate nitrite.

[0078] In these embodiments, the inorganic acid is highly acidic and non-volatile, and can react quickly with nitrite to generate nitrous acid, and the generated nitrous acid then undergoes an esterification reaction with aromatic alcohol to generate nitrite ester of aromatic alcohol. The process has a fast reaction rate and high selectivity, and nitrite can be completely converted. After the reaction is completed, the oil-water two-phase separation speed is fast.

[0079] In some embodiments, the esterification reaction satisfies at least one of the following conditions:

[0080] (1) The nitrite is sodium nitrite or potassium nitrite;

[0081] (2) Inorganic acids include: nitric acid and sulfuric acid;

[0082] (3) the molar ratio of nitrite to aromatic alcohol is 1:1 to 1:1.1;

[0083] (4) the molar ratio of nitrite to inorganic acid is 1:1 to 1:1.1;

[0084] (5) The solvent used in the esterification reaction includes: one or a combination of water and aromatic alcohol;

[0085] (6) The esterification reaction temperature is 10°C to 40°C, and the reaction time is 1 min to 10 min.

[0086] In these embodiments, sodium nitrite or potassium nitrite is cheap and easy to obtain, and its properties are relatively stable at room temperature; nitric acid and sulfuric acid are highly acidic, and can instantly provide a large amount of hydrogen ions after being added, thereby quickly converting nitrite into nitrous acid, thereby initiating an esterification reaction between nitrous acid and aromatic alcohol. In order to completely convert nitrite, usually the inorganic acid needs to be slightly excessive, so the molar ratio of nitrite to inorganic acid is 1:1 to 1:1.1; in order to completely consume the generated nitrous acid by aromatic alcohol, usually the aromatic alcohol needs to be slightly excessive, so the molar ratio of nitrite to aromatic alcohol is 1:1 to 1:1.1.

[0087] In some embodiments, under alkaline conditions, reducing a nitrite with hydrazine hydrate to prepare sodium azide may include:

[0088] mixing hydrazine hydrate and an alkaline aqueous solution to obtain a mixed solution;

[0089] The mixed solution and nitrite are mixed, and the nitrite is subjected to a reduction reaction with hydrazine hydrate under heating and stirring.

[0090] In these embodiments, the alkaline aqueous solution can be a sodium hydroxide aqueous solution, which has two functions: first, it quickly converts the intermediate product generated by the reaction of nitrite and hydrazine hydrate into sodium azide to prevent nitrite from decomposing into gaseous by-products; second, it reduces the hydrogen ion concentration in water and converts hydrogen azide into sodium azide.

[0091] In some embodiments, the reduction reaction satisfies at least one of the following conditions:

[0092] (1) The molar ratio of hydrazine hydrate to the alkali in the alkaline aqueous solution is 1:1.05 to 1:1.5;

[0093] (2) The molar ratio of hydrazine hydrate to nitrite is 1:0.5 to 1:1.5;

[0094] (3) The temperature of the reduction reaction is 10°C to 80°C, and the time is 1 min to 60 min.

[0095] In these embodiments, the alkaline aqueous solution can be exemplified by a slight sodium hydroxide aqueous solution, which not only participates in the reaction but also plays a role in stabilizing the product sodium azide. By slightly overdosing sodium hydroxide, the generation 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, a large amount of hydrazine hydrate residue can be avoided while improving the reaction selectivity, thereby reducing the difficulty of removing hydrazine hydrate. By controlling the temperature of the reduction reaction to 10°C to 100°C and the time to 1min to 60min, the reaction time can be reduced and the efficiency can be improved while ensuring the reaction selectivity.

[0096] In some embodiments, the preparation of nitrite ester of aromatic alcohol using aromatic alcohol as raw material and the above reduction reaction are carried out independently in a continuous flow reactor or a batch reactor.

[0097] In these embodiments, the preparation of nitrite ester of aromatic alcohol using aromatic alcohol as raw material and the above reduction reaction can be carried out as two separate steps in a continuous flow reactor or a batch reactor.

[0098] When the preparation of the nitrite ester of the aromatic alcohol using the aromatic alcohol as the raw material and the above reduction reaction are carried out in a continuous flow reactor, the two steps can also be carried out continuously.

[0099] In some embodiments, the continuous flow reactor is any one of a tank reactor, a tubular reactor, and a microchannel reactor.

[0100] The batch reactor may be a batch reactor.

[0101] In some embodiments, the synthesis method further comprises: after allowing nitrite to undergo a reduction reaction with hydrazine hydrate under alkaline conditions, liquid-liquid phase separation treatment is performed on the reaction product, and sodium azide in the aqueous phase is separated from the aqueous phase to obtain sodium azide.

[0102] In these embodiments, after the nitrite and hydrazine hydrate are subjected to a reduction reaction under alkaline conditions, the reaction product can be phase-separated into an upper organic phase and a lower aqueous phase. The aqueous phase can be separated by liquid-liquid phase separation, and sodium azide in the aqueous phase can be separated and purified to obtain sodium azide with a high purity. In the above synthesis method, since the solubility of the nitrite of the aromatic alcohol in the aqueous phase is extremely low, the hydrolysis of the nitrite of the aromatic alcohol can be significantly inhibited, thereby reducing the generation 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 by simple separation and purification.

[0103] 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.

[0104] In these embodiments, after nitrite and hydrazine hydrate undergo a reduction reaction under alkaline conditions, the reaction product can be 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 achieving the recycling of aromatic alcohol and reducing the waste of alcohol raw materials.

[0105] 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.

[0106] In the following examples, all raw materials can be purchased from commercial sources, and in order to maintain the reliability of the experiments, the raw materials used in the following examples all have the same physical and chemical parameters or are prepared by the same processing method.

[0107] Example 1

[0108] The synthesis method of sodium azide in Example 1 is as follows:

[0109] (1) A 35 wt% sodium nitrite aqueous solution and benzyl alcohol are mixed and dispersed in a batch reactor, and a 65% mass fraction nitric acid aqueous solution is added, and the reaction is carried out at 20° C. for 10 minutes. After the reaction is completed, the phases are separated, and the upper oil phase is a 90 wt% purity benzyl alcohol nitrite ester solution, and the remaining component is a 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.

[0110] (2) Mix 85% hydrazine hydrate and 30% sodium hydroxide aqueous solution in an intermittent reactor, add 90% nitrite synthesized in step (1) by constant speed dropwise addition, the dropwise addition time is 10 min, react at 40° C. for 10 min, and separate the phases after the reaction. The lower aqueous phase is a sodium azide solution with a mass fraction of 26.5%, and contains 0.3% 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% can be obtained, the yield is 96%, and the hydrolysis rate of nitrite is 1.1%; the upper oil phase is benzyl alcohol with a purity of 94%, and nitrite can be synthesized again through step (1) without separation and purification, and recycled. Wherein, 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.

[0111] Example 2

[0112] The synthesis method of sodium azide in Example 2 is substantially the same as the synthesis method of sodium azide in Example 1, except that:

[0113] In step (1), the nitrite used is potassium nitrite, and the inorganic acid used is sulfuric acid with a mass fraction of 60%.

[0114] In step (2), the molar ratio of hydrazine hydrate to nitrite is 1:1.5, and the reaction time is 60 min; the final yield of sodium azide is 96%, and the hydrolysis rate of nitrite is 1.9%; the specific reaction parameters are shown in Table 1 below.

[0115] Example 3

[0116] The synthesis method of sodium azide in Example 3 is substantially the same as the synthesis method of sodium azide in Example 1, except that:

[0117] In step (1), the esterification reaction temperature is 40° C. and the 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.

[0118] In step (2), the molar ratio of hydrazine hydrate to nitrite is 1:0.5, nitrite is added to the reactor at one time, and the reaction time is 1 min; the final yield of sodium azide is 49%, and the hydrolysis rate of nitrite is 0.3%; the specific reaction parameters are shown in Table 1. In this embodiment, the molar amount of nitrite added to benzyl alcohol is only 50% of that of hydrazine hydrate, so the yield of sodium azide calculated based on hydrazine hydrate is low. If calculated based on nitrite, the yield of sodium azide is 98%.

[0119] Example 4

[0120] The synthesis method of sodium azide in Example 4 is substantially the same as the synthesis method of sodium azide in Example 1, except that:

[0121] In step (1), the temperature of the esterification reaction is 10° C. and the time is 10 min.

[0122] In step (2), the molar ratio of hydrazine hydrate to sodium hydroxide is 1:1.2. The final yield of sodium azide is 95%, and the hydrolysis rate of nitrite is 1.4%; the specific reaction parameters are shown in Table 1 below.

[0123] Example 5

[0124] The synthesis method of sodium azide in Example 5 is substantially the same as the synthesis method of sodium azide in Example 1, except that:

[0125] In step (2), the molar ratio of hydrazine hydrate to sodium hydroxide is 1:1.5. The final yield of sodium azide is 94%, and the hydrolysis rate of nitrite is 1.8%; the specific reaction parameters are shown in Table 1 below. It can be seen from Examples 4 and 5 that increasing the molar amount of sodium hydroxide can improve the stability of sodium azide, but will increase the hydrolysis rate of nitrite.

[0126] Example 6

[0127] The synthesis method of sodium azide in Example 6 is substantially the same as the synthesis method of sodium azide in Example 1, except that:

[0128] In step (2), the molar ratio of hydrazine hydrate to sodium hydroxide is 1:1.05, the reaction temperature is 10°C, and the reaction time is 60 min. The final yield of sodium azide is 97%, and the hydrolysis rate of nitrite is 0.8%; the specific reaction parameters are shown in Table 1 below. Compared with Example 1, lowering the temperature is beneficial to increasing the yield and reducing the hydrolysis rate, but the reaction time is extended by 40 min compared with Example 1.

[0129] Example 7

[0130] The synthesis method of sodium azide in Example 7 is substantially the same as the synthesis method of sodium azide in Example 1, except that:

[0131] In step (2), the molar ratio of hydrazine hydrate to sodium hydroxide is 1:1.05, the reaction temperature is 80°C, and the reaction time is 15 min. The final yield of sodium azide is 86%, and the hydrolysis rate of nitrite is 1.9%; the specific reaction parameters are shown in Table 1 below. Compared with Example 1, increasing the reaction temperature is beneficial to increasing the reaction rate, but the yield is reduced and the hydrolysis rate is increased.

[0132] Example 8

[0133] The synthesis method of sodium azide in Example 8 is substantially the same as the synthesis method of sodium azide in Example 1, except that:

[0134] 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 min. After the reaction is completed, the yield of benzyl nitrite is 96% and the purity is 90 wt%.

[0135] In step (2), the reduction reaction is carried out in a continuous reactor, and the nitrite with a mass fraction of 90% synthesized in step (1) 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.

[0136] Example 9

[0137] The synthesis method of sodium azide in Example 9 is substantially the same as the synthesis method of sodium azide in Example 1, except that:

[0138] In step (1), 1-phenylethanol is used to replace benzyl alcohol; in step (2), 90% of the mass fraction of nitrite synthesized in step (1) is added to a mixed solution of hydrazine hydrate and sodium hydroxide; the final yield of sodium azide is 89%, and the hydrolysis rate of nitrite is 0.9%; the specific reaction parameters are shown in Table 1. Compared with Example 1, replacing the raw material from benzyl alcohol with 1-phenylethanol can reduce the hydrolysis rate of nitrite, but will reduce the yield of sodium azide.

[0139] Example 10

[0140] The synthesis method of sodium azide in Example 10 is substantially the same as the synthesis method of sodium azide in Example 1, except that:

[0141] In step (1), 4-methylbenzyl alcohol is used to replace benzyl alcohol; in step (2), 90% of the mass fraction of the nitrite synthesized in step (1) is added to a mixed solution of hydrazine hydrate and sodium hydroxide; the final yield of sodium azide is 87%, and the hydrolysis rate of nitrite is 1%; the specific reaction parameters are shown in Table 1. Compared with Example 1, replacing the raw material from benzyl alcohol with 4-methylbenzyl alcohol can reduce the hydrolysis rate of nitrite, but will reduce the yield of sodium azide.

[0142] Comparative Example 1

[0143] The synthesis method of sodium azide in Comparative Example 1 is substantially the same as the synthesis method of sodium azide in Example 1, except that:

[0144] In step (1), a small molecule fatty alcohol, i.e., isopropanol, is used to replace benzyl alcohol to synthesize isopropanol nitrite.

[0145] In step (2), 90% of the mass fraction of isopropyl nitrite synthesized in step (1) is added to the 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. Compared with Example 1, after the raw material is replaced by isopropyl alcohol from benzyl alcohol, the reaction rate is sharply reduced, resulting in the yield of sodium azide from 96% to 6.2% within 20 minutes; and the hydrolysis rate of nitrite is increased, and the hydrolysis rate has reached 3.1% when the conversion rate of nitrite is only 10%.

[0146] Table 1

[0147]

[0148] As shown in Table 1, the aromatic alcohol provided in the embodiment of the present application can be applied to intermittent reaction or continuous reaction. Compared with the synthesis of sodium azide using isopropanol 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, 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 20min, greatly improving the production efficiency; and if a continuous reaction process is used, the volume of the reactor can be greatly reduced. On the second hand, due to the extremely low solubility of the nitrite of the aromatic alcohol in the aqueous phase, the hydrolysis side reaction can be significantly inhibited, 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, and there is no need to recover the alcohol in the aqueous phase, which greatly reduces the separation energy consumption. Thirdly, the boiling point of nitrites of aromatic alcohols is usually higher than 150°C, and the partial pressure in the gas phase is extremely low, which is beneficial to reduce VOCs emissions and improve process safety.

[0149] 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 of separating the alcohol raw materials and energy consumption, and can directly recycle the separated aromatic alcohols to achieve energy saving and efficiency improvement, so it has good application prospects.

[0150] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0151] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A method for synthesizing sodium azide, characterized in that: include: The aromatic alcohol and nitrite are subjected to an esterification reaction in the presence of an inorganic acid to generate nitrite; Under alkaline conditions, allowing the nitrite to undergo a reduction reaction with hydrazine hydrate to prepare the sodium azide; Wherein, the aromatic alcohol includes: the structural formula is expressed as: One or more compounds of the invention, wherein Ar is selected from the following substituted or unsubstituted C6~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; 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. When Ar is selected from substituted C6~C 20 Aryl and substituted C3~C 10 When any one of the heteroaryl groups is present, the substituted substituent is selected from C1 to C9 alkyl, and * indicates the attachment site.

2. The synthesis method according to claim 1, characterized in that n is equal to 1, and R1 and R2 are selected from H or methyl, and the substituted substituents are selected from methyl or ethyl.

3. The synthesis method according to claim 1, characterized in that The aromatic alcohol includes one or more of the following structural formulas: , and .

4. The synthesis method according to claim 1, characterized in that The esterification reaction satisfies at least one of the following conditions: (1) The nitrite is sodium nitrite or potassium nitrite; (2) The inorganic acid includes nitric acid and sulfuric acid; (3) The molar ratio of the nitrite to the aromatic alcohol is 1:1 to 1:1.1; (4) The molar ratio of the nitrite to the inorganic acid is 1:1 to 1:1.1; (5) The solvent used in the esterification reaction includes: water and one or a combination of the aromatic alcohol; (6) The temperature of the esterification reaction is 10°C to 40°C, and the time is 1 min to 10 min.

5. The synthesis method according to claim 1, characterized in that The method of preparing the sodium azide by causing the nitrite to undergo a reduction reaction with hydrazine hydrate under alkaline conditions comprises: mixing hydrazine hydrate and an alkaline aqueous solution to obtain a mixed solution; The mixed solution and the nitrite are mixed, and the nitrite is subjected to a reduction reaction with hydrazine hydrate under heating and stirring.

6. The synthesis method according to claim 5, characterized in that The reduction reaction satisfies at least one of the following conditions: (1) The molar ratio of the hydrazine hydrate to the alkali in the alkaline aqueous solution is 1:1.05 to 1:1.5; (2) The molar ratio of the hydrazine hydrate to the nitrite is 1:0.5 to 1:1.5; (3) The temperature of the reduction reaction is 10°C to 80°C, and the time is 1 min to 60 min.

7. The synthesis method according to any one of claims 1 to 6, characterized in that The esterification reaction and the reduction reaction are independently carried out in a continuous flow reactor or a batch reactor.

8. The synthesis method according to claim 7, characterized in that The continuous flow reactor is any one of a tank reactor, a tubular reactor and a micro-channel reactor.

9. The synthesis method according to any one of claims 1 to 6, characterized in that The synthesis method further comprises: after the nitrite and hydrazine hydrate undergo a reduction reaction under alkaline conditions, the reaction product is subjected to liquid-liquid phase separation treatment, and the sodium azide in the aqueous phase is separated from the aqueous phase to obtain the sodium azide.

10. The synthesis method according to claim 9, characterized in that After the liquid-liquid phase separation treatment, the method further includes using the separated aromatic alcohol as a raw material to prepare the nitrite ester of the aromatic alcohol.

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