Background and overview[1][2]
Oxalic acid is also known as “ramic acid” and its scientific name is “oxalic acid”. The molecular formula is (COOH)2·2H2O. It is a colorless and transparent monoclinic crystal, often found in rhubarb and other plants in the form of calcium salts. Strongly acidic, non-flammable, toxic, soluble in hot water, ethanol and glycerin, slightly soluble in ether, harmful to eyes, corrosive to skin, stronger when exposed to water, people can be poisoned and die if 2 grams are taken orally. . During storage, it should be protected from moisture, rain, and isolated from oxidants and alkali substances. To prevent contact with food, it should be kept away from living areas and should not be installed on the deck when loading the ship. Although this substance is not easy to burn, if it causes fire, water and sand can be used as fire-fighting methods. If it enters your eyes or touches your skin, rinse with plenty of water. If swallowed by mistake, you should be sent to the hospital for treatment.
In industry, it is generally synthesized from carbon monoxide and sodium hydroxide. It can be used as a solvent for refining rare metals, a dye reducing agent, a printing and dyeing bleach, a metal rust remover, a marble polishing agent, a descaling agent, and an anti-wrinkle surface treatment agent for paper. It is also a raw material for manufacturing oxalates and organic synthesis. Oxalic acid production methods include sodium formate method, starch or glucose oxidation method, ethylene glycol oxidation method, propylene oxidation method, etc. However, these methods have the disadvantages of high energy consumption and large pollution, and have been gradually eliminated. At present, more methods are used to produce oxalate esters through oxo synthesis, and then the oxalate esters are hydrolyzed to produce oxalic acid.
Oxalate poisoning symptoms and mechanism[2]
Many animal experiments have shown that soluble oxalates can rapidly bind to calcium or magnesium in the serum, thereby abruptly lowering the concentrations of these ions. Acute oxalate poisoning can sharply reduce the calcium concentration in the serum, affect the animal’s normal cell function, cause the animal’s muscle tremors, circulatory collapse, and eventually death. Chronic oxalate poisoning, insoluble calcium oxalate can seriously damage the renal tubules.
Finally, even if the animals do not die from hypocalcemia and cellular energy metabolism disorders, they will die from renal failure. When cattle are poisoned by oxalate, they may suffer from loss of appetite, depression, unresponsiveness, constipation, dry mouth, prolonged blood coagulation time, reduced rumen motility, frequent standing and lying down, muscle weakness, abnormal gait, accelerated heart rate, muscle tremors and twitching; Frequent urge to urinate, and occasional discharge of brown-red urine; shortness of breath and difficulty, bloody foamy liquid flowing from the nose; eventually paralysis, lying on the ground, or even coma. When oxalate poisoning occurs, the body will show weakness, ataxia, twitching, and coma. Oxalates can affect energy metabolism and blood glucose levels.
Apply[1][3]
Oxalic acid can be used as a reducing agent, bleaching agent, decontamination reagent, and analytical reagent, and its anhydrate can be used as a dehydrating agent in organic synthesis. In addition, oxalic acid can be prepared into oxalate to play its role
1. Application in magnetic induction materials
Magnetic induction materials are widely used in industrial production such as communications, sensing, audio and video equipment, switching power supplies, and magnetic heads. The electromagnetic properties of magnetic induction materials are largely determined by its chemical composition, microstructure, morphology and uniformity of particles. At present, most of our industry uses high-temperature solid-phase synthesis, which sometimes makes the cost too high. At the same time, when solid phase materials are used as precursor raw materials, the oxide reactivity of each component is not very high and cannot be microscopically uniform.
2. Application in ceramic materials
Conductive ceramics have the characteristics of good conductivity, stable chemical properties, corrosion resistance, and high temperature resistance. In some aspects, they cannot be replaced by metal conductive materials. Therefore, the research on conductive ceramics has received increasing attention and its applications have become more and more widespread. The room temperature resistivity of the BaPbO3 conductive ceramic material prepared by the liquid phase co-precipitation method is 3.4× 10-4Ψ·cm, and it has an obvious PTC effect.
3. Application in catalyst preparation
Catalysts made into ultrafine particles are currently a hot research topic. Because ultrafine particles have a large specific surface and many surface active centers, they show higher activity and selectivity in catalytic reactions. BaTiO3 was prepared by using high-temperature solid-state reaction method, oxalate co-precipitation method and sol-gel method. BaTiO3 was used as a carrier and the impregnation method was used to load the metal to prepare the catalyst. The nickel-based catalyst was prepared by the sol-gel direct method. The sol-gel method was used to prepare BaTiO3. The catalyst prepared by the gel direct method has higher activity than the nano-BaTiO3 supported nickel-based catalyst prepared by the impregnation method.
4. Application in fluorescent materials
The quality of phosphor is not only related to purity, but also closely related to particle morphology, particle size, and particle size distribution. Since high-definition color TV picture tubes adopt a point-shaped phosphor screen structure, the diameter of the phosphor dots is required to be very small. For this reason, phosphors with small particles with an average particle size of less than 2 μm and long afterglow and no flicker can meet the requirements.
5. Preparation of superconducting materials
YBaCuO high-temperature superconducting powder was prepared in a nitric acid solution containing excess oxalic acid with a mass ratio of Y, Ba, and Cu of 1:1:3 at pH=1.0~1.4. Use nitrates of Y, Ba, and Cu as raw materials, add oxalic acid, and perform co-precipitation at pH=2~4. The prepared precursor is thermally decomposed at 850~930°C to prepare high-temperature superconducting powder with Tc=92 K. . Nitrate is added to the mixture of oxalic acid and ethanol according to the material mass ratio of Bi:Pb:Sr:Ca:Cu: 0.8:0.2:1:1:2, and the pH value is adjusted with ammonia water. The obtained precursor is heated at 800°C. After roasting for 6 hours, Bi-Pb-Sr was obtained-Ca-Cu-O high temperature superconducting powder. Bi-Pb-Sr-Ca-Cu-O superconductor powder is prepared by microemulsion method, with particle size in the range of 2 to 6 nm.
6. Preparation of metal or alloy powder materials
Use Ce (NO3)3· 6H2O (>98%), Y (NO3 sub>)3· 6H2O (99.9%) and C2H2O4· 2H 2O (>99.5% ), using oxalate as precipitation medium. It has been shown that oxalates are not as sensitive to cleaning and drying conditions as hydroxide precipitates, allowing yields close to 100%. After washing the precipitate with alcohol and calcining at 700°C, fine powder with an average agglomeration size of 0.7 μm was obtained. The powder has good compressibility and sinterability. Research shows that the performance of cemented carbide bits made with this composite powder is no less than that of WC-Co cemented carbide.
7. Others
Neodymium metal can be extracted from NdFeB magnetic material manufacturing industrial waste using oxalic acid as a precipitant. Rare earth composite oxide catalysts have good exhaust gas purification performance. Compared with traditional precious metal catalysts, rare earth composite oxide catalysts have low cost and good resistance to lead poisoning. Using the oxalate co-precipitation method and according to different drying conditions, nanocrystalline LaCoO3 perovskite with more oxygen vacancies was obtained.
Preparation [4] [5]
Method 1: Use carbon monoxide and methyl nitrite to synthesize dimethyl oxalate, and hydrolyze dimethyl oxalate to obtain oxalic acid. The reaction principle of this method is as follows: Reaction to synthesize dimethyl oxalate from methyl nitrite:
Reaction to synthesize oxalic acid from dimethyl oxalate:
Method 2: The specific process of synthesizing oxalic acid from oxalate ester can be as follows: before using the hydrolysis reaction tower, preheat the tower, and when the temperature of the entire tower body is higher than 60°C, pump the oxalate ester and water into the tower. The lower part, then control the temperature of the tower kettle at 90~150℃, the temperature at the top of the tower at 60~90℃, and the pressure at the top of the tower 0~0.2Mpa (G). During the reaction reflux process, monitor the temperature of the tower top and the produced liquid from the tower kettle. According to the demand, alcohol is extracted from the top of the tower, and oxalic acid aqueous solution is extracted from the tower kettle.
Method 3: A method for preparing oxalic acid through catalytic hydrolysis of oxalate resin, including the following steps,
1) Wash the ion exchange resin with deionized water and dry it, and measure the water content in the ion exchange resin at the same time;
2) Weigh 200-300 parts by mass of deionized water; 10 parts by mass of oxalate ester and 6.5-13 parts by mass of ion exchange resin. Among them, the mass ratio of water to ester of the constituent components is 19:1- 30:1, the water in the water-to-ester mass ratio includes the moisture in the ion exchange resin and deionized water;
3) Add deionized water and ion exchange resin into the open reactor, heat to 55-75°C and stir the ion exchange resin at a constant speed; at the same time, seal and heat the oxalate ester to 55-75°C ;
4) Quickly transfer the oxalate ester to the reaction kettle and continue stirring at a constant speed,
5) Take regular samples to measure the content of oxalic acid and oxalate esters. When the oxalate ester content in the reactor is less than 0.005%, stop stirring and heating;
6) Take out the bottom liquid from the reactor and separate the generated oxalic acid from water through distillation reaction.
References
[1] Technical Dictionary of Container Transport Business·Volume 2
[2] Long Miao, He Runxia, Liu Minyue, et al. Harm of oxalate in feed to ruminants and its prevention [J]. Feed Industry, 2014, 35(12): 48-50.
[3] Zhang Weinan, Chen Donghua. Application of oxalate in inorganic functional materials[J]. Journal of South Central University for Nationalities: Natural Science Edition, 2004, 23(2): 29-32.
4] Qian Shengtao; Chen Zhu; Liu Huawei; Xiao Erfei; Liu Yingjie; Lu Ming; Chengchun Pigment Carbon Black Xi; Lei Jun; Lu Zhiyan; Wang Xianhou; Kong Yuhua. A process for synthesizing oxalic acid from oxalate esters. CN201510583382 .X, application date 20150915
[5] Yao Xiaoyan; Liu Yi. Method for preparing oxalic acid by catalytic hydrolysis of oxalate resin CN201610133291.0, application date 20160309
