Glyoxylic acid consists of an aldehyde group (-CHO) and a carboxyl group (-COOH), and its aqueous solution is pale yellow. Soluble in water, slightly soluble in ethanol, ether, benzene and other organic solvents. It is the simplest keto acid (aldehyde acid), which has both acid and aldehyde properties, and is used as an intermediate for perfumes, medicines, dyes, plastics, etc.
Glyoxylic Acid Property
Melting point
-93°C
Boiling point
111°C
density
1.33 g/mL at 20 °C
refractive index
n20/D 1.414
Fp
111°C
storage temp.
Store below +30°C.
solubility
Miscible with ethanol. Slightly miscible with ether and benzene. Immiscible with esters.
pka
3.18(at 25℃)
Water Solubility
miscible
Glyoxylic Acid Uses
Glyoxylic acid is the easiest keto acid (aldehyde acid) with both acid and also aldehyde residential properties, and is used as a basic material for varnishes, as an intermediate for fragrances, drugs, dyes, plastics as well as home chemicals.
Glyoxylic acid is an essential fine chemical raw material, made use of in medication (primarily used in broad-spectrum antibiotic amoxicillin, antihypertensive medication atenolol, aesthetic additive allantoin, high value-added aromatic aldehyde, p-hydroxybenzoic acid, and so on ), water top quality stabilizers, flavors (ethyl vanillin), pesticide intermediates, and so on are commonly utilized.
Glyoxylic acid is utilized as a flavor agent as well as fixative in cosmetics as well as in pharmaceuticals.
Synthesis of Glyoxylic Acid in a Microchannel Reactor
The experimental device is shown in Figure 1. Nitric acid and glyoxal are pumped into the microreactor through pump 1 and pump 2 according to the molar ratio of 0.85:1, respectively. Nitric acid is mixed and reacted in the reactor, and the mixed solution continues to react in the microchannel at the temperature of t2; then the reaction is quenched in a coil outside the microchannel at 10-15 °C, and the reaction solution enters the collection bottle through the back pressure valve , the product to be analyzed is obtained.
When the molar ratio of nitric acid (35%) to glyoxal (40%) was 0.85:1, the flow rate of glyoxal (Q1) was 4.7 mL/min, and the flow rate of nitric acid (Q2) was 5.3 mL/min. The total residence time is 4min54s, of which the residence time of the t1 stage is 54s, and the residence time of the t2 stage is 4min. When the pressure of the back pressure valve is 0.5MPa, the effect of temperature on the conversion rate and selectivity is shown in the table. Figure 2 shows that the temperature of t2 is kept at 40 °C, and the influencing factors of the temperature of t1 are investigated. Figure 3 shows that the temperature of t1 is controlled to be 80 °C, and the influencing factors of the temperature of t2 are investigated.
Figure 2 Influencing factors of t1 temperature
Figure 3 Influencing factors of t2 temperature
From Figure 2 and Figure 3, it can be concluded that when t1 increases from 40°C to 90°C, the conversion rate increases from 15% to 95%, the selectivity increases from 20% to 58%, and then decreases to 45%. . The reason may be that when the temperature is lower, the reaction rate is slower and only a small amount of glyoxal is oxidized by nitric acid. As the temperature increases, the reaction is gradually initiated, so the conversion and selectivity increase; but when the temperature increases from 80 ℃ continues to increase, at this time the product will continue to be oxidized to oxalic acid, so the selectivity decreases; when t1 = 40℃, the temperature is low, it is difficult to initiate oxidation of glyoxal, and glyoxal is easy to polymerize and form More self-polymers and therefore lower selectivity. When t2 increased from 20℃ to 50℃, the conversion rate increased from 70% to 90%, the selectivity increased from 42% to 60%, and then decreased to 40%. Analysis of the reason may be that the reaction has been initiated at t1 temperature. At t2 temperature, glyoxal continues to participate in the reaction, so the conversion rate increases; when t2 increases from 20 °C to 40 °C, due to the polymerized glyoxal After preheating for a period of time at t1 temperature, some depolymerization has begun. At t2 temperature, although the temperature is low, the depolymerization reaction cannot be stopped immediately. At this time, the depolymerization rate is greater than the polymerization rate, so the selectivity gradually increases. When t2 continued to increase from 40 °C, the conversion of glyoxylic acid to oxalic acid was promoted, so the selectivity decreased. Therefore, t1 = 80°C and t2 = 40°C were chosen in the next experiment.
NO is produced during the oxidation of glyoxal by nitric acid. Studies have shown that the presence of NO in the system promotes the oxidation of glyoxal, that is, NO reacts with nitric acid to generate nitrous acid, and then nitrous acid reacts with glyoxal to generate Glyoxylic acid. In the presence of gas to promote the conditions, the pressure also played a great role in promoting the reaction. Figure 4 shows the effect of pressure on the conversion and selectivity of the reaction. This figure shows that when the pressure is increased, the conversion and selectivity of the reaction are increased, because when the pressure is low, the mixing effect in the system is poor and the system is unstable. However, when the pressure continues to increase, it is difficult to separate the generated NO from glyoxylic acid. When glyoxylic acid is contacted and mixed with nitric acid, the generated nitrous acid reacts directly with glyoxylic acid, so that the nitrous acid in the system that is in contact with glyoxal is decomposed. As the content decreases, the reaction rate decreases, so the conversion rate and selectivity decrease at the same time. Therefore, the pressure of 1.0MPa is the best choice in the reaction process.
The difficulty of this process is to prevent the overoxidation of glyoxal, so in addition to the influencing factors that must be considered in traditional reactors such as temperature and pressure, the method of staged feeding can also be considered. If the initial feed amount is too small, the reaction rate will be low and the reaction time will be prolonged; if the initial feed amount is too large, the glyoxylic acid will be easily oxidized, which will easily lead to a decrease in selectivity. In the continuous process of using the microchannel reactor, the molar ratio of nitric acid and glyoxal was first fed from 0.3:1 to the first reaction piece, and then 0.12 mol of nitric acid was added to the third reaction piece, In this way, the conversion rate and selectivity of the reaction are both above 70%, and compared with the traditional kettle type process, the amount of nitric acid in the entire reaction process is reduced, and the post-treatment pressure is reduced.
Such nitric acid oxidation reaction produces a large amount of heat, and it is easy to produce peroxidized products during the reaction. Because the microchannel reactor has good heat transfer and heat transfer effects, it is possible to accurately control the reaction conditions. Therefore, the temperature is difficult to control in the traditional reactor or the reaction type with low selectivity of the reaction due to back mixing can achieve better experimental results by means of staged temperature control and staged feeding in the microchannel reactor. Compared with the traditional kettle reaction, the advantages of the microchannel reactor are mainly reflected in:
①Experimental precise control of reaction conditions (temperature, pressure, flow).
②Double-sided heat exchange has great advantages for chemical reaction types with large heat release.
③ Continuous flow reactor, no back mixing, increase the selectivity of the reaction.
④The area is small, and it can be used as a laboratory for an experimental chemical plant.
Preparation Method of Glyoxylic Acid
At present, glyoxylic acid industry mainly adopts glyoxal nitric acid oxidation method to produce, and glyoxylic acid industrial product is usually 40% or 50% glyoxylic acid aqueous solution, which contains 0.7%-1.5% oxalic acid, 0.5% -1.5% glyoxal and 0.1%-3% hydrochloric acid impurities. The glyoxal impurity in glyoxylic acid has a great influence on its quality, and a large amount of research has been carried out to reduce the glyoxal impurity content in the product. In industrial production, in order to reduce glyoxal residue in glyoxylic acid product, have to take the method that adds excessive nitric acid to improve glyoxal raw material conversion rate, causes a large amount of glyoxylic acid oxidative decomposition, reduces product yield.
A method for preparing crystalline glyoxylic acid, characterized in that high-purity crystalline glyoxylic acid is prepared by crystallization from a 45%-50% glyoxylic acid aqueous solution, comprising the following steps:
(1) 35%-40% glyoxylic acid crude product is vacuum concentrated at 45-55 ℃ to obtain 45%-50% glyoxylic acid;
(2) cooling 45%-50% glyoxylic acid to -2-2°C, and centrifuging the separated oxalic acid;
(3) The mother liquor is further cooled to -6-10°C, and glyoxylic acid monohydrate is induced to crystallize with glyoxylic acid seeds;
(4) the monohydrate glyoxylic acid crystal separated out by centrifugation after 4-6 hours of low temperature crystallization;
(5) the secondary mother liquor repeats the above concentrated and monohydrate glyoxylic acid crystallization separation operations;
(6) three times the mother liquor is returned to the oxidation to reduce the glyoxal content and circulate;
(7) The glyoxylic acid monohydrate crystals are put into a desiccator containing anhydrous calcium chloride and calcium oxide to be dried.
Company Profile and Corporate Culture
Company Profile：
ZhiShang Chemical is owned by ZhiShang Group is a professional new-type chemicals enterprise combined into research and development, production and sales .
The company’s competitive product is pharmaceutical raw materials and intermediates (especially carbohydrate derivatives Series), In recent years, the company has made a major breakthrough in food and feed additives, plant extraction, industrial chemicals industry .
The company insists on the spirit of “sincere management, strict quality control, customer as god” , get consistent high praise from customers at home and abroad.
Corporate Culture：
OUR MISSION Help China Chemicals to benefit the happiness of human life OUR VISSION Become the most trusted chemical supplier in the world OUR BUSINESS PHILOSOPHY Striver – oriented, enrich employees, customer first, deep service, seek development OUR VALUES Be prepared for danger in times of peace, forge ahead actively, unity and cooperation, and be brave to fight
About Us
The production base is located in Zhangqiu chemical industry park and Tai’an high-tech chemical industry park. laboratory and workshop in strict accordance with the GMP standard and the product fit national ISO9001 and ISO2000 standards.
“Zhishang” products are exported to Europe, North and South America, the Middle East, Asia Pacific and Africa area, so as to establish a long-term and stable cooperation relationship with customer in the world.
Factory Location : Diao Town Industry Park, Zhangqiu City, Jinan City, Shandong Province, China.
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FAQ
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We will make samples before mass production, and after sample approved, we’ll begin mass production. Doing 100% inspection during production, then do random inspection before packing.
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Our MOQ is 1kg. But usually we accept less quantity such as 100g on the condition that sample charge is 100% paid.
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Different quantity has different discount.
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1. ≤50kg, Express delivery recommended, usually called as DDU service;
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