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Production of oxalic acid and matters needing attention

Issuing time:2020-10-17 08:23

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Industrial manufacturing method


The main industrial production methods of oxalic acid are: sodium formate method, oxidation method, carbonyl synthesis method, ethylene glycol oxidation method, propylene oxidation method, carbon monoxide coupling method.


1. Carbon monoxide purified by sodium formate method reacts with sodium hydroxide under pressure to form sodium formate, which is then dehydrogenated at high temperature to produce sodium oxalate, which is then subjected to lead (or calcification), acidification, crystallization, dehydration and drying processes to obtain finished oxalic acid. The synthetic pressure of carbon monoxide and sodium hydroxide is generally 1.8-2.0mpa. The dehydrogenation temperature was 400 ℃.


2. In the oxidation process, starch or glucose mother liquor is used as raw material, and nitric acid sulfuric acid is oxidized to produce oxalic acid in the presence of alum catalyst. The nitrogen oxide in the waste gas is sent to the absorption tower for recovery to form dilute nitric acid.


3. Carbonylation synthesis method carbon monoxide is purified to more than 90%, and then carbonylated with butanol in the presence of palladium catalyst to form dibutyl oxalate. Then oxalic acid is obtained by hydrolysis. This method can be divided into liquid phase method and gas phase method. The reaction conditions of gas phase method are lower, and the reaction pressure is 300-400kpa. The reaction pressure of liquid phase method is 13.0-15.0mpa.


4. Ethylene glycol oxidation is obtained by air oxidation of ethylene glycol in the presence of nitric acid and sulfuric acid.


The oxidation process of propylene was carried out in two steps. In the first step, propylene is converted to α - nitrolactic acid by nitric acid oxidation, and then oxalic acid is obtained by further catalytic oxidation. In the second step, mixed acid can be used as oxidant. Industrial grade oxalic acid dihydrate was produced by propylene oxidation, and the total yield was more than 90%.


Raw material consumption quota: coke (84%) 510kg / T, sulfuric acid (100%) 950kg / T, caustic soda (100%) 920kg / T.


Oxalic acid usually exists in the form of salt in many plant cell membranes in nature. In the past, wood chips and strong alkali were co melted at 240-250 ℃ to produce oxalate, and then acidified to obtain oxalic acid. Later, oxalic acid was produced by dehydrogenation of sodium formate. In industry, carbon monoxide (such as tail gas from yellow phosphorus production) is absorbed by caustic soda to produce sodium formate. The latter is dehydrogenated at 380 ℃ to produce sodium oxalate, which is then treated with lime and sulfuric acid to produce oxalic acid.


Hazards of oxalic acid and precautions in use:


Oxalic acid in the human body is not easy to be oxidized and decomposed. The product formed after metabolism is acidic, which can lead to acid-base imbalance in the human body. If you eat too much, you will be poisoned.


And oxalic acid in the human body if calcium and zinc will be generated calcium oxalate and zinc oxalate, not easy to absorb and discharged from the body, affecting the absorption of calcium and zinc.


Children need a lot of calcium and zinc for their growth and development. If the body is lack of calcium and zinc, it can not only lead to bone and tooth dysplasia, but also affect intellectual development.


Excessive intake of oxalic acid can also cause stones.


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