Synthesis method of maleic anhydride and precautions for storage and transportation | (herbicide safety agent)

Tell you the synthesis method of maleic anhydride and pay attention to storage and transportation. Maleic anhydride, also known as maleic anhydride (MAH), referred to as maleic anhydride, is the acid anhydride of maleic acid. At room temperature, it is a colorless or white solid with an acidic taste, and the molecular formula is C4H2O3. Maleic anhydride was previously prepared by catalytic oxidation of benzene, but due to the price, it is now mostly produced by n-butane oxidation.

Synthesis method of maleic anhydride

1. Benzene oxidation method

Benzene vapor and air (or oxygen) undergo gas-phase oxidation reaction to form maleic anhydride on catalysts with V2O5-MnO3 as active components and α-Al2O3 as support. The benzene oxidation method is a traditional production method for the production of maleic anhydride, and the process technology is mature and reliable. The main technologies include the American SD method, the Alusuisle/UCB method and the Japanese catalyst chemical method, among which the SD method is the most widely used.

2. C4 olefin method

This method uses n-butene, butadiene, etc. in the mixed C4 fraction as raw materials, and air (or oxygen), under the action of V2O5-P2O5 catalyst, through gas-phase oxidation reaction to generate maleic anhydride, in which n-butene is first dehydrogenated to form butadiene during the reaction process, and then oxidized to form maleic anhydride. During the reaction process, in addition to the formation of the main products, carbon monoxide, carbon dioxide and water are also byproduced, as well as a small amount of acetaldehyde, acetic acid, acrylic aldehyde and furan, etc. The raw material unit consumption is high and the yield is low. This method has been gradually eliminated.

3. Phthalic anhydride by-product method

When phthalic anhydride is produced from o-xylene, a certain amount of maleic anhydride products can be obtained by-product, and the output is about 5% of the output of phthalic anhydride. In the production of phthalic anhydride, the reaction tail gas is removed from the organic matter by the washing tower and then discharged into the atmosphere. The washing liquid is maleic anhydride and a small amount of impurities such as benzoic acid and phthalic acid, which are concentrated and refined and heated and dehydrated to obtain maleic anhydride products.

4. N-butane oxidation method

The n-butane oxidation process is based on n-butane as raw material, and the gas phase oxidation reaction is generated to maleic anhydride under the action of V2O5-P2O5 catalyst. Since the industrialization of this process by Monsanto Company in the United States in 1974, due to the low price of raw materials, little environmental pollution, and the abundance of n-butane resources in Europe and the United States, it has developed rapidly, representing the development trend of maleic anhydride production processes. Capacity: In 2010, the domestic capacity was about 1 million tons, of which the butane production capacity was about 100,000 tons.

Matters needing attention in storage and transportation of maleic anhydride

1. Precautions for transportation: The packaging should be complete and the loading should be safe when shipping. During transportation, ensure that the container does not leak, collapse, fall or damage. It is strictly forbidden to mix and transport with oxidants, reducing agents, acids, edible chemicals, etc. During transportation, it should be protected from exposure to sunlight, rain, and high temperature;

2. Storage precautions: Store in a cool, dry, well-ventilated warehouse for recovery. Keep away from fire and heat sources. Keep the container sealed. It should be stored away from oxidants, reducing agents, acids, and edible chemicals, and should not be mixed. Equipped with fire-fighting equipment of the corresponding variety and quantity. The storage area should be equipped with suitable materials to contain leaks;

3. Packing precautions: chemical intermediates (fluorocarbon methyl ester) pesticide intermediates bag or two-layer kraft paper bag with full opening or middle opening steel barrel; chemical intermediates (fluorocarbon methyl ester) pesticide intermediates bag or two-layer kraft paper bag outer fiberboard barrel, plywood barrel, cardboard barrel; chemical intermediates (fluorocarbon methyl ester) pesticide intermediates bag outer chemical intermediates (fluorocarbon methyl ester) pesticide intermediates barrel (solid); chemical intermediates (fluorocarbon methyl ester) pesticide intermediates barrel (liquid).