Oxalic acid powder is an organic compound with the chemical formula of HCO₄. It is a metabolic product of organisms. It is a binary weak acid, widely distributed in plants, animals and fungi, and plays different functions in different living organisms. The study found that more than 100 kinds of plants are rich in oxalic acid, especially spinach, amaranth, beet, purslane, taro, sweet potato and rhubarb. Because oxalic acid can reduce the bioavailability of mineral elements, it is easy to form calcium oxalate with calcium ions in the human body and lead to kidney stones, so oxalic acid is often considered as an antagonist to the absorption and utilization of mineral elements. Its anhydride is carbon trioxide.
The industrial production methods of oxalic acid mainly include: sodium formate method, oxidation method, carbonyl synthesis method, ethylene glycol oxidation method, propylene oxidation method, and carbon monoxide coupling method.
1. Carbon monoxide purified by sodium formate method reacts with sodium hydroxide under pressure to generate sodium formate, which is then dehydrogenated at high temperature to generate sodium oxalate, which is then subject to lead (or calcification), acidification, crystallization, dehydration and drying to obtain finished oxalic acid. The synthetic pressure of carbon monoxide and sodium hydroxide is generally 1.8-2.0MPa. The dehydrogenation temperature is 400 ℃.
2. The oxidation method takes starch or glucose mother liquor as raw material and oxidizes with nitric acid-sulfuric acid in the presence of alum catalyst to obtain oxalic acid. The nitrogen oxide in the waste gas is sent to the absorption tower for recovery to generate dilute nitric acid.
3. Carbon monoxide in the carbonyl synthesis method is purified to more than 90%, and then undergoes carbonylation reaction with butanol in the presence of palladium catalyst to produce dibutyl oxalate, which is then hydrolyzed to obtain oxalic acid. This method is divided into liquid phase method and gas phase method. The reaction conditions of gas phase method are relatively low, and the reaction pressure is 300-400kPa. The reaction pressure of liquid phase method is 13.0-15.0MPa.
Use of oxalic acid powder:
Complexing agent, masking agent, precipitating agent, reducing agent. The analysis is used to verify and determine beryllium, calcium, chromium, gold, manganese, strontium, thorium and other metal ions. Sodium and other elements are examined by micro-crystal analysis. Precipitate calcium, magnesium, thorium and rare earth elements. Calibrate the standard solution of potassium permanganate and cerium sulfate solution. bleaching agents. Dye aids. It can also be used to remove rust on clothes. Before painting exterior wall paint, the construction industry should first paint oxalic acid to remove alkali because of the strong alkalinity of the wall.
The pharmaceutical industry is used to manufacture drugs such as aureomycin, oxytetracycline, tetracycline, streptomycin, borneol, vitamin B12, phenobarbital, etc. The printing and dyeing industry is used as color developing and dyeing aids, bleaching agents, and pharmaceutical intermediates. The plastic industry is used to produce PVC, amino plastics and urea-formaldehyde plastics.
As a catalyst for the synthesis of phenolic resin, the catalytic reaction is mild, the process is relatively stable, and the duration is the longest. Acetone oxalate solution can catalyze the curing reaction of epoxy resin and shorten the curing time. It is also used as pH regulator for synthesis of urea-formaldehyde resin and melamine formaldehyde resin. It can also be added to PVF water-soluble adhesive to improve drying speed and bonding strength. It is also used as curing agent of urea-formaldehyde resin and metal ion chelating agent. It can be used as a promoter for the preparation of starch adhesive with KMnO4 oxidant to accelerate the oxidation rate and shorten the reaction time.
1.As bleach：
Oxalic acid is mainly used as reducing agent and bleaching agent, in the production of antibiotics, borneol and other drugs, as well as solvent for refining rare metals, dye reducing agent, tanning agent, etc.
2.Oxalic acid can also be used in the production of cobalt-molybdenum-aluminum catalysts, the cleaning of metals and marble, and the bleaching of textiles.
3.Used for metal surface cleaning and treatment, rare earth element extraction, textile printing and dyeing, leather processing, catalyst preparation, etc.
Detection method of oxalic acid:
Test according to the analytical method specified in GB1626-88.
Oxalic acid content (calculated by H2C2O4*2H2O) is titrated with sodium hydroxide standard solution using phenolphthalein as indicator.
Sodium carbonate is added to the sulfate (calculated as SO42-) sample to make the sulfate in oxalic acid generate sulfate. In order to decompose oxalic acid and oxalate by heat, the residual solution is added with barium chloride solution to generate barium sulfate for turbidimetry.
The ash content shall be determined according to GB7531.
Heavy metals (calculated in Pb) shall be determined according to GB7531.
Iron (calculated as FE) shall be determined according to GB3049.
Chloride (calculated as Cl) In the acid solution of nitric acid, chloride and silver nitrate form silver chloride, and then turbidimetric.