阅读说明：本技术 使用微通道反应器由羟基乙腈连续化制备甘氨酸的方法 (Method for continuously preparing glycine from hydroxyacetonitrile by using microchannel reactor ) 是由 杨仁俊 龚文照 张伟 赫瑞元 赵广 李鑫 韩萌 毋楠 袁秋华 李伟斌 于 2019-10-08 设计创作，主要内容包括：本发明提供了一种使用微通道反应器由羟基乙腈连续化制备甘氨酸的方法,其以羟基乙腈与碳源、氨源为原料,经预热与混合后,在微通道反应器内依次进行合成海因和海因水解反应,得到甘氨酸水溶液,再经汽提、蒸发浓缩、结晶、分离、脱色、干燥得到甘氨酸产品。与现有方法相比,本方法实现了以羟基乙腈为原料快速连续化制备甘氨酸,同时具有反应时间短、副产物少、甘氨酸收率高、制备成本低的优点。(The invention provides a method for continuously preparing glycine from hydroxyacetonitrile by using a microchannel reactor. Compared with the prior art, the method realizes the rapid and continuous preparation of the glycine by using the hydroxyacetonitrile as the raw material, and has the advantages of short reaction time, less by-products, high yield of the glycine and low preparation cost.)

1. A method for continuously preparing glycine from hydroxyacetonitrile by using a microchannel reactor is characterized in that the hydroxyacetonitrile, a carbon source and an ammonia source are used as raw materials, hydantoin synthesis and hydantoin hydrolysis reaction are sequentially carried out in a microchannel reactor assembly after preheating and mixing to obtain a glycine aqueous solution, a glycine product is obtained after steam stripping, evaporative concentration, crystallization, separation, decoloration and drying, and the microchannel reactor assembly is formed by connecting at least two sub-reactors in series.

2. The method according to claim 1, characterized in that the method is in particular:

(1) mixing hydroxyacetonitrile with a carbon source and an ammonia source, conveying the mixture to a primary microchannel reactor, and performing synthetic reaction at the temperature of 80-130 ℃ and the pressure of 0.5-5 Mpa to obtain reaction mixed liquid;

(2) conveying the reaction mixed liquid obtained in the step (1) to a secondary microchannel reactor, controlling the temperature to be 120-180 ℃ and the pressure to be 0.5-5 Mpa, and carrying out hydrolysis reaction to obtain hydrolysis reaction liquid;

(3) sending the hydrolysis reaction liquid in the step (2) to a stripping tower, and recovering ammonia and carbon dioxide for recycling to obtain a glycine aqueous solution;

(4) and (4) evaporating, concentrating, crystallizing, separating, decoloring and drying the glycine aqueous solution obtained in the step (3) to obtain glycine.

3. The method of claim 2, wherein the carbon source is one or more of ammonium carbonate, ammonium bicarbonate, and/or carbon dioxide, and the ammonia source is one or more of ammonium carbonate, ammonium bicarbonate, aqueous ammonia, and/or liquid ammonia.

4. The method of claim 3, wherein the carbon and ammonia sources are ammonium carbonate and ammonium bicarbonate, respectively, and the molar ratio of the hydroxyacetonitrile to the ammonium carbonate, ammonium bicarbonate, and water is 1: 3-10: 2-7: 40 to 100.

5. The process of claim 2 wherein the primary microchannel reactor residence time of step (1) is from 15 to 60 minutes.

6. The process of claim 2 wherein the secondary microchannel reactor residence time of step (2) is from 30 to 120 minutes.

7. The method of claim 2, wherein the primary microchannel reactor and the secondary microchannel reactor are made of one or more of titanium alloy, zirconium alloy, hastelloy.

8. The process of claim 2 wherein the primary and secondary microchannel reactors have an inner diameter of 0.1mm to 1mm and a wall thickness of 0.2mm to 1.1 mm.

9. The method according to claim 2, wherein the ammonia gas and the carbon dioxide separated in the stripping tower in the step (3) are returned to the blending kettle and recycled as raw materials.

10. The method as claimed in claim 2, wherein the primary crystallization mother liquor in the step (4) is returned to the secondary microchannel reactor in the step (2), the generated solid is heated and dissolved, decolored by activated carbon and filtered, and then is subjected to secondary crystallization, and the secondary crystallization mother liquor is returned to the three-effect evaporator.

Technical Field

The invention relates to the field of fine chemical engineering, in particular to a method for continuously preparing glycine from hydroxyacetonitrile by using a microchannel reactor.

Background

Glycine is also known as Glycine, Glycine, formula C₂H₅NO₂And the molecular weight of 75.07 is the amino acid with the simplest structure, and the amino acid is used as an important fine chemical intermediate and widely applied to the fields of pesticides, medicines, foods, feeds, daily chemicals, organic synthesis and the like. China is the largest glycine production and consumption country in the world, and the market scale of glycine exceeds 35 million tons. However, several glycine production methods of the prior art still have some disadvantages. For example:

(1) a hydrolysis method: the glycine is prepared from natural proteins such as gelatin or silk by hydrolyzing, separating, refining, filtering, and drying. The method has the advantages of high consumption of protein raw materials and high production cost. Has been replaced by synthetic methods.

(2) Chloroacetic acid method: dissolving a catalyst urotropine in ammonia water, dropwise adding chloroacetic acid under the conditions of good stirring and 30-50 ℃, raising the temperature to 72-78 ℃ after feeding is finished, preserving the temperature for 3 hours, then cooling, and recrystallizing twice by using ethanol or methanol to obtain glycine with the purity of about 95%. The method has the advantages of poor product quality, difficult wastewater treatment, large environmental protection pressure and high production cost. Is the mainstream process for producing glycine in China and is completely eliminated abroad.

(3) The schterek method: mixing formaldehyde aqueous solution, sodium cyanide (or potassium cyanide) and ammonium chloride, reacting at low temperature, adding acetic acid to separate out methylene aminoacetonitrile after the reaction is finished, dissolving in ethanol, adding sulfuric acid to convert the methylene aminoacetonitrile into aminoacetonitrile sulfate, adding stoichiometric barium hydroxide to generate barium sulfate and glycine, filtering, and concentrating and crystallizing the filtrate to obtain the glycine. The method has long process route, complex desalting operation of reaction post-treatment and harsh operating conditions. Has been replaced by the improved schltrek method and the direct hydantoin method.

(4) Modified schterek method: in order to improve the quality of glycine, reduce the production cost and reduce the environmental pollution, an improved Scherrer's method using hydrocyanic acid to replace sodium cyanide or potassium cyanide is developed abroad, the reaction uses hydrocyanic acid, formaldehyde, ammonia and carbon dioxide as raw materials, and the reaction liquid is carried out in a tubular reactor. Glycine is precipitated at low temperature, the mother liquor is recycled, and the balance is moved towards the direction of a target product by changing the concentration of a by-product in a reaction system, so that the aim of improving the reaction yield is fulfilled. However, the hydrocyanic acid used as a raw material in the method is extremely toxic and volatile, and cannot be transported for a long distance, so that the popularization and the application of the hydrocyanic acid are restricted.

(5) The aminoacetonitrile method is that hydroxyacetonitrile reacts with ammonia water to obtain aminoacetonitrile, inorganic base is added for alkaline hydrolysis, inorganic acid is added for neutralization to obtain glycine reaction liquid, glycine is obtained through the steps of concentration, decoloration, crystallization and the like, and mother liquid is recycled; however, the method has the defects of more side reactions, high product separation difficulty, long post-desalting process and the like.

(6) Direct hydantoin method: the hydroxyacetonitrile is an addition product of hydrocyanic acid and formaldehyde, and the stability of the hydroxyacetonitrile is obviously improved compared with the hydrocyanic acid and an aqueous solution thereof. Hydroxyl acetonitrile is used as a main raw material to react with an ammonia source and a carbon source (ammonia water and carbon dioxide or ammonium bicarbonate) under the conditions of good stirring and certain temperature to synthesize hydantoin, and then the hydantoin is hydrolyzed under the conditions of certain temperature and pressure to obtain glycine, wherein the chemical reaction formula is as follows:

the process has the advantages of high atom utilization rate, high product quality, cleanness, environmental protection and the like, has great application prospect, but the problems of back mixing and long production period of the existing direct hydantoin method adopting a tank reactor can only realize intermittent tank type production, and industrial continuity is not realized, so that a method for preparing dry glycine more efficiently, quickly and continuously is urgently needed.

Disclosure of Invention

The invention aims to solve the technical problem of the prior art for preparing glycine by a direct hydantoin method, and provides a more efficient and rapid continuous method for preparing glycine, which comprises the following steps: the method comprises the steps of taking hydroxy acetonitrile, a carbon source and an ammonia source as raw materials, preheating and mixing, sequentially carrying out hydantoin synthesis and hydantoin hydrolysis reaction in a microchannel reactor assembly to obtain a glycine aqueous solution, carrying out steam stripping, evaporative concentration, crystallization, separation, decolorization and drying to obtain a glycine product, wherein the microchannel reactor assembly is formed by connecting at least two sub-reactors in series.

Preferably, the method specifically comprises the following steps:

(1) mixing hydroxyacetonitrile with a carbon source and an ammonia source, conveying the mixture to a primary microchannel reactor, and performing synthetic reaction at the temperature of 80-130 ℃ and the pressure of 0.5-5 Mpa to obtain reaction mixed liquid;

(2) conveying the reaction mixed liquid obtained in the step (1) to a secondary microchannel reactor, controlling the temperature to be 120-180 ℃ and the pressure to be 0.5-5 Mpa, and carrying out hydrolysis reaction to obtain hydrolysis reaction liquid;

(3) sending the hydrolysis reaction liquid in the step (2) to a stripping tower, and recovering ammonia and carbon dioxide for recycling to obtain a glycine aqueous solution;

(4) and (4) evaporating, concentrating, crystallizing, separating, decoloring and drying the glycine aqueous solution obtained in the step (3) to obtain a glycine product.

Preferably, the carbon source is one or more of ammonium carbonate, ammonium bicarbonate and/or carbon dioxide, and the ammonia source is one or more of ammonium carbonate, ammonium bicarbonate, ammonia water and/or liquid ammonia.

Preferably, the carbon source and the ammonia source are ammonium carbonate and ammonium bicarbonate respectively, and the molar ratio of the hydroxyacetonitrile to the ammonium carbonate, the ammonium bicarbonate and the water is 1: 3-10: 2-7: 40 to 100.

Preferably, the residence time of the first-stage microchannel reactor in the step (1) is 15-60 minutes.

Preferably, the residence time of the secondary microchannel reactor in the step (2) is 30-120 minutes.

Preferably, the material of the primary microchannel reactor and the secondary microchannel reactor is one or more of titanium alloy, zirconium alloy and hastelloy.

Preferably, the inner diameter of the first-stage micro-channel reactor and the second-stage micro-channel reactor is 0.1 mm-1 mm, and the wall thickness is 0.2 mm-1.1 mm.

Preferably, the ammonia gas and the carbon dioxide obtained by the separation in the stripping tower in the step (3) are returned to the batching kettle and recycled as raw materials.

Preferably, the primary crystallization mother liquor in the step (4) is returned to the secondary microchannel reactor in the step (2), the generated solid is heated and dissolved, decolored by active carbon and filtered, and then secondary crystallization is carried out, and the secondary crystallization mother liquor is returned to the triple-effect evaporator.

Compared with the prior art, the method realizes the rapid and continuous preparation of the glycine by using the hydroxyacetonitrile as the raw material, and has the advantages of short reaction time, less byproducts, high yield of the glycine and low preparation cost.

Drawings

FIG. 1 is a process flow diagram in an embodiment of the invention;

FIG. 2 is a schematic diagram of one embodiment of a microchannel reactor assembly of the present invention.

Detailed Description

In order to make the technical solutions of the present invention better understood by those skilled in the art, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art can modify the process parameters appropriately to achieve the desired results with reference to the disclosure herein. It is expressly intended that all such alterations and modifications which are obvious to those skilled in the art are deemed to be incorporated herein by reference, and that the techniques of the invention may be practiced and applied by those skilled in the art without departing from the spirit, scope and range of equivalents of the invention.

The invention provides a method for continuously preparing glycine from hydroxyacetonitrile by using a microchannel reactor, which is characterized in that the hydroxyacetonitrile, a carbon source and an ammonia source are used as raw materials, hydantoin synthesis and hydantoin hydrolysis reaction are sequentially carried out in a microchannel reactor assembly after preheating and mixing to obtain a glycine aqueous solution, and a glycine product is obtained through steam stripping, evaporation concentration, crystallization, separation, decoloration and drying, wherein the microchannel reactor assembly is formed by at least connecting two sub-reactors in series.

The method specifically comprises the following steps (1): firstly, mixing hydroxyacetonitrile with a carbon source and an ammonia source, then conveying the mixture to a primary microchannel reactor, and carrying out synthetic reaction at the temperature of 80-130 ℃ and the pressure of 0.5-5 Mpa to obtain reaction mixed liquid; step (2), conveying the reaction mixed liquor obtained in the step (1) to a secondary microchannel reactor, controlling the temperature to be 120-180 ℃ and the pressure to be 0.5-5 Mpa, and carrying out hydrolysis reaction to obtain hydrolysis reaction liquor; step (3), sending the hydrolysis reaction liquid obtained in the step (2) to a stripping tower, and recycling ammonia gas and carbon dioxide to obtain a glycine aqueous solution; and (4) evaporating, concentrating, crystallizing, separating, decoloring and drying the glycine aqueous solution obtained in the step (3) to obtain glycine.

According to the invention, the carbon source is one or more of ammonium carbonate, ammonium bicarbonate and/or carbon dioxide, and the ammonia source is one or more of ammonium carbonate, ammonium bicarbonate, ammonia water and/or liquid ammonia. The carbon source and the ammonia source are respectively ammonium carbonate and ammonium bicarbonate, and the molar ratio of the hydroxyacetonitrile to the ammonium carbonate, the ammonium bicarbonate and the water is 1: 3-10: 2-7: 40-100, more preferably 1: 3-10: 2-7: 50-80 parts. Wherein the residence time of the primary microchannel reactor in the step (1) is 15-60 minutes, more preferably 15-40 minutes, and the residence time of the secondary microchannel reactor in the step (2) is 35-80 minutes. The material of the first-stage micro-channel reactor and the second-stage micro-channel reactor is one or more of titanium alloy, zirconium alloy and hastelloy, and ammonia gas and carbon dioxide obtained by separation in the stripping tower in the step (3) are conveyed back to the batching kettle and recycled as raw materials. And (3) returning the primary crystallization mother liquor in the step (4) to the secondary microchannel reactor in the step (2), heating and dissolving generated solids, decoloring with active carbon, filtering, and then performing secondary crystallization, returning the secondary crystallization mother liquor to the triple-effect evaporator, then crystallizing through the crystallization kettle I, returning the primary crystallization mother liquor obtained by feeding the primary crystallization mother liquor into the centrifuge I to the microchannel reactor, feeding the rest of the primary crystallization mother liquor into the decoloring kettle to be mixed with the active carbon for decoloring, feeding the mixture into a filter press for filter pressing treatment, feeding the obtained waste active carbon into an incinerator, feeding large materials obtained by filter pressing into the crystallization kettle II for crystallization, then feeding the large materials into the centrifuge II for centrifugal treatment, feeding the obtained secondary crystallization mother liquor into the triple-effect evaporator for treatment, and drying the rest of the materials to.

The reaction mechanism of the invention is

Referring to fig. 2, a schematic diagram of an embodiment of the microchannel reactor assembly of the present invention is shown, wherein the microchannel reactor assembly includes a first-stage microchannel reactor 4 and a second-stage microchannel reactor 5, and the first-stage microchannel reactor or the second-stage microchannel reactor has the same structure and is made of a slender elbow, and has an inner diameter of 0.1mm to 1mm and a wall thickness of 0.2mm to 1.1 mm.

In the present invention, unless otherwise specified, scientific and technical terms used herein have the meanings that are commonly understood by those skilled in the art. The main compounds present in the present invention are explained below:

hydroxy acetonitrile: also known as glycolonitrile, of the formula HOCH₂CN, which is generally a colorless oily liquid, is a hydrocyanic acid derivative and is also the simplest cyanohydrin.

Hydantoin: also known as Hydantoin, English Hydantoin, formula C₃H₄N₂O₂Molecular weight 100.08.

Glycine: also called Glycine, English Glycine, abbreviation Gly, chemical formula C₂H₅NO₂The amino acid is an amino acid having the simplest structure, is also an amino acid not essential to the human body, and is generally a white monoclinic or hexagonal crystal or a white crystalline powder.

In order to make those skilled in the art better understand the technical solution of the present invention, the following detailed description of the present invention is provided with reference to specific embodiments.