Glyoxylic acid is an organic compound with the molecular formula of c2h2o3, which is composed of an aldehyde group (-cho) and a carboxyl group (-cooh). Its structural formula is hoccooh, CAS 298-12-4, and its molecular weight is 74.04. Light yellow transparent liquid. Soluble in water, slightly soluble in ethanol, ether, benzene, etc. It is a toxic substance with irritation and corrosiveness. The oral LD50 of rats is 70mg/kg. Operators should pay attention to wearing labor protection articles, and wash with plenty of water when touching the skin. It can be used to synthesize vanillin, ethyl vanillin, jasmonaldehyde (capsaicin), p-methoxybenzaldehyde (anisaldehyde), etc. These spices are widely used in food, daily necessities, cosmetics and other fields. It can also be used in the production of water purifying agent hydroxy phosphorus carboxylic acid, as polymer crosslinking agent, electroplating additive and high-efficiency element fertilizer (ethylenediamine di-o-hydroxyphenyl large sodium ferric acetate eddha FENa), etc. These applications involve environmental protection, materials science and other fields.
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Method 1: dichloroacetic acid method
1. Preparation of dichloroacetic acid: methanol and chlorine are introduced into the reactor and chlorinated under the action of catalyst to produce dichloroacetic acid. The chemical equation of this step is: CH3OH+Cl2 → h2c2o2+HCl.
2. Condensation of dichloroacetic acid and sodium methoxide: dichloroacetic acid and sodium methoxide are mixed and condensed under appropriate temperature and pressure to produce sodium dimethoxyacetate. The chemical equation for this step is: h2c2o2+CH3ONa → h2c2o2 · ch3o2na.
3. Hydrolysis of sodium dimethoxyacetate: sodium dimethoxyacetate is mixed with hydrochloric acid and hydrolyzed at a certain temperature and pressure to produce glyoxylic acid and methanol. The chemical equation of this step is: h2c2o2 · ch3o2na+HCl → h2c2o2 · HCl+CH3OH.
4. Separation and purification: the glyoxylic acid and methanol are separated and further purified to obtain high-purity glyoxylic acid. This step usually adopts distillation, crystallization and other methods.
Through the above steps, glyoxylic acid can be synthesized by dichloroacetic acid method. It should be noted that the whole process needs to be carried out under specific temperature and pressure conditions, and the conditions of chemical reaction need to be accurately controlled to ensure the quality and yield of products. In addition, it is also necessary to pay attention to safety issues, especially when chlorination, condensation, hydrolysis and other reactions are carried out, corresponding safety measures should be taken to prevent explosion, corrosion and other safety accidents.
Glyoxylic acid synthesis by dichloroacetic acid is an important organic chemical production method, which has a wide application prospect and value. In order to ensure its sustainable development and efficiency, it is necessary to strengthen technology research and innovation, and take corresponding environmental protection measures and energy-saving technologies to reduce production costs and environmental pollution.
In practice, the synthetic process can be optimized and adjusted as needed. For example, in the condensation reaction of dichloroacetic acid with sodium methoxide, an appropriate amount of catalyst can be added to improve the reaction rate and selectivity; In the hydrolysis reaction, the purity and yield of the hydrolysate can be improved by controlling the reaction temperature and concentration. In addition, the recovery and reuse of by-products can also be researched and developed to realize the effective utilization of resources and reduce production costs.
Method 2: maleic anhydride ozonation reduction method
The detailed steps are as follows:
1. Preparation of maleic anhydride: firstly, maleic acid and anhydride should be reacted to produce maleic anhydride. The chemical equation of this step is: c4h2o4+C2H2O2 → 2ch2o2. In practice, maleic acid is usually dissolved in an appropriate amount of solvent, then anhydride is slowly added, and the temperature is controlled to prevent the occurrence of side reactions.
2. Ozonation reaction: then, the generated maleic anhydride is reacted with hydrogen peroxide solution to generate the intermediate product ozonation. The chemical equation of this step is: ch2o2+H2O2 → ch2o2 · H2O. Ozonation reaction requires certain temperature and pressure conditions, and is usually carried out in a specific reactor. In the reaction process, the concentration and adding speed of hydrogen peroxide need to be strictly controlled to ensure the safety of the reaction.
3. Reduction reaction: then, the odorous oxide reacts with the reducing agent to generate glyoxylic acid. The chemical equation of this step is: ch2o2 · H2O+NAH → CH3COOH+NaOH. Hydride is usually used as reducing agent in reduction reaction, such as sodium, potassium, etc. During the reaction process, it is necessary to control the temperature and pressure to ensure the complete reduction reaction. At the same time, it is also necessary to pay attention to safety issues, such as preventing hydrogen leakage.
4. Product separation and purification: finally, the glyoxylic acid generated is separated from the reaction solution and purified. This step usually adopts distillation, crystallization and other methods. Glyoxylic acid and other volatile impurities can be separated by distillation, while glyoxylic acid can be separated from the solution by crystallization for further purification. In the process of product separation and purification, attention should be paid to the control of temperature and the stability of operation to avoid product loss and deterioration.
Maleic anhydride ozonation reduction method is a commonly used method to synthesize glyoxylic acid with high yield and purity. However, this method needs to consume a large number of raw materials such as maleic anhydride and hydrogen peroxide, and will produce a certain amount of wastewater and waste gas. Therefore, corresponding environmental protection measures and energy-saving technologies need to be taken to reduce production costs and environmental pollution.
Method 3: chemical oxidation
The basic steps are as follows:
1. Raw material preparation: first, prepare the required raw materials, such as formic acid, acetate or ethylene glycol. These raw materials are the basis for the synthesis of glyoxylic acid.
2. Oxidation reaction: the raw material is reacted with oxidant to generate glyoxylic acid. Common oxidants include nitric acid, potassium permanganate, hydrogen peroxide, etc. The chemical equation for this step depends on the raw materials and oxidants used. For example, using formic acid as raw material and nitric acid as oxidant, the reaction equation is: HCOOH+2hno3 → hcoono2+2H2O. If acetate is used as raw material and potassium permanganate as oxidant, the reaction equation is: CH3COO (-)+MnO4 (-)+H (+) → CH3COOH+Mn (IV). If ethylene glycol is used as raw material and hydrogen peroxide as oxidant, the reaction equation is hoch2ch2oh+H2O2 → ohccho+2H2O.
3. Product separation and purification: after the reaction is completed, the glyoxylic acid generated needs to be separated from the reaction solution and purified. This step usually adopts extraction, distillation, crystallization and other methods. Through these methods, glyoxylic acid can be separated from other impurities to obtain high purity products.
4. Post treatment: finally, the glyoxylic acid after separation and purification is post treated, such as drying, packaging, etc. This step is to ensure the quality and safety of the product.
Chemical oxidation is a common method for the synthesis of glyoxylic acid with high yield and purity. However, this method needs to consume a large number of oxidants and raw materials, and will produce a certain amount of wastewater and waste gas. Therefore, corresponding environmental protection measures and energy-saving technologies need to be taken to reduce production costs and environmental pollution.
In practical applications, the selection of appropriate synthesis methods needs to be comprehensively considered according to the actual needs and conditions. Different synthesis methods have different advantages and disadvantages, such as cost, efficiency, environmental protection and so on. Therefore, when selecting synthesis methods, it is necessary to comprehensively consider a variety of factors to determine the most appropriate method. In addition, it is also necessary to strengthen technological research and innovation to promote the sustainable development of the organic chemical industry and socio-economic progress.