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Preparation of Diethyl Maleate

Diethyl maleate, also known as Maleic acid diethyl, is mainly used in the synthesis of polymer monomers, pesticides(e.g. organophosphorus insecticide: malathion), pharmaceuticals, fragrances, etc. The commonly used synthesis method is catalyzed by sulfuric acid or cation exchange resin, which is made by esterification of shortening of maleic acid or maleic acid with ethanol. Sulfuric acid is a strong inorganic acid, which is highly corrosive and can cause side reactions (e.g. oxidation, carbonization, addition), easily causing environmental pollution and not meeting today’s environmental requirements. Cation exchange resin can overcome the disadvantages of sulfuric acid catalysis, but the cost is higher. The above two catalysts are applied in the process of producing diethyl maleate, and the conversion rate is generally not more than 95%.

Diethyl maleate Chemical Structure-141-05-9 - Feiyang

In order to overcome the shortcomings of the above technical problems, a method for the preparation of diethyl maleate is provided, which can completely solve the above problems.
Add crispy maleate, anhydrous ethanol, solid acid catalyst and water-carrying agent in the reaction vessel, install water divider, reflux condenser and thermometer on the reaction vessel, heat for reflux water division, react until no water beads appear and then react for 25~30min, stop heating, wait for cooling at room temperature for 30min and then release the water layer, wash the reaction solution with water, dry and then steam the pavilion, first steam out the former pavilion division and then collect 216~220℃ of the pavilion into products.
The above solid acid catalyst is acid zeolite. The mass ratio of the above-mentioned crispy maleate, anhydrous ethanol and solid acid catalyst is 5:12:0.3. The above-mentioned water-carrying agent is any one of cyclohexane, benzene or toluene.

Zeolites are salts of sodium, bell, calcium, barium and strontium of aluminosilicate. Different metal ions make zeolites with different pore sizes. Synthetic zeolites are highly porous crystals made of small microtubules interwoven from 3 to 8Å in diameter. The small pores of zeolites inhibit the formation of macromolecules. More than fifty percent of the volume of zeolite is the pore volume, and most of the atoms in zeolite are surface atoms. The surface area of zeolites is very large. A spoon full of acid zeolite catalyst expanded to the thickness of one molecule has an area more than the size of a batting cage. In addition, the microenvironment surrounding the acidic zeolite cavity is a regular pattern of separable protons. These protons are uniformly distributed throughout the internal structure of the zeolite as reaction centers.

In order to overcome the shortcomings of the above technical problems, a method for the preparation of diethyl maleate is provided, which can completely solve the above problems. Add crispy maleate, anhydrous ethanol, solid acid catalyst and water-carrying agent in the reaction vessel, install water divider, reflux condenser and thermometer on the reaction vessel, heat for reflux water division, react until no water beads appear and then react for 25~30min, stop heating, wait for cooling at room temperature for 30min and then release the water layer, wash the reaction solution with water, dry and then steam the pavilion, first steam out the former pavilion division and then collect 216~220℃ of the pavilion into products. The above solid acid catalyst is acid zeolite. The mass ratio of the above-mentioned crispy maleate, anhydrous ethanol and solid acid catalyst is 5:12:0.3. The above-mentioned water-carrying agent is any one of cyclohexane, benzene or toluene. Zeolites are salts of sodium, bell, calcium, barium and strontium of aluminosilicate. Different metal ions make zeolites with different pore sizes. Synthetic zeolites are highly porous crystals made of small microtubules interwoven from 3 to 8Å in diameter. The small pores of zeolites inhibit the formation of macromolecules. More than fifty percent of the volume of zeolite is the pore volume, and most of the atoms in zeolite are surface atoms. The surface area of zeolites is very large. A spoon full of acid zeolite catalyst expanded to the thickness of one molecule has an area more than the size of a batting cage. In addition, the microenvironment surrounding the acidic zeolite cavity is a regular pattern of separable protons. These protons are uniformly distributed throughout the internal structure of the zeolite as reaction centers. The solid acid catalyst used in the present invention can increase the conversion of the feed material from the usual below 95% to more than 99.5%. Moreover, the present invention can avoid the problem of waste liquid discharge caused by the addition of sodium carbonate to neutralize excess acid in the liquid catalyst process. The present invention is described in further detail below in conjunction with specific embodiments. Preparation method of diethyl maleate in the following steps. Example: Add 5g of crispy maleate, 12g of anhydrous ethanol, 0.3g of acidic zeolite, 15m1 cyclohexane burned in the reaction vessel, install on the reaction vessel a water separator, reflux condenser and thermometer, heat for reflux water separation, react until no water droplets appear and then react for 25min, stop heating, leave to cool at room temperature for 30min and then release the water layer, the reaction solution washed with water, dried and then steamed pavilion, first steamed out before the pavilion, and then collect 216 ~ 220 ℃ pavilion into products. - Feiyang

The solid acid catalyst used in the present invention can increase the conversion of the feed material from the usual below 95% to more than 99.5%. Moreover, the present invention can avoid the problem of waste liquid discharge caused by the addition of sodium carbonate to neutralize excess acid in the liquid catalyst process.

The present invention is described in further detail below in conjunction with specific embodiments.
Preparation method of diethyl maleate in the following steps.
Example:
Add 5g of crispy maleate, 12g of anhydrous ethanol, 0.3g of acidic zeolite, 15m1 cyclohexane burned in the reaction vessel, install on the reaction vessel a water separator, reflux condenser and thermometer, heat for reflux water separation, react until no water droplets appear and then react for 25min, stop heating, leave to cool at room temperature for 30min and then release the water layer, the reaction solution washed with water, dried and then steamed pavilion, first steamed out before the pavilion, and then collect 216 ~ 220 ℃ pavilion into products.

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