Neopentyl glycol production technology
Neopentyl glycol (neopentylglycol, NPG) 2, 2 - dimethyl - 1, 3 propanediol, molecular formula C5H12O2, relative molecular mass 104.15, structured HOCH2-C(CH3)2-CH2OH, as white crystalline solid, odourless, soluble in water, also soluble in aromatic hydrocarbons, esters, lower ketones, chlorinated meridians, insoluble in hexane and cyclohexane, melting point 124~130℃, boiling point 210℃, density (21℃) 1.06 g/cm3, flash point 129℃, spontaneous combustion point 399℃, sublimation temperature 210℃. Diols are synthesized by the reaction of isobutyraldehyde with formaldehyde, a by-product of butyl and octanol. Owing to the existence of hydroxyl groups in the symmetric position of the molecule and the absence of alpha-hydrogen atoms in the central carbon atom, it has some special properties that other binary alcohols do not have. The unsaturated resins, high-grade coatings and their derivatives made from it have good thermal stability, light resistance, corrosion resistance and chemical stability.

Neoprene is widely used as a plasticizer for the production of unsaturated polyester resins, oil-free alkyd resins, polyurethane foams and elastomers, additives for advanced lubricants and other fine chemicals. Neopentadiol is an excellent solvent for the selective separation of aromatic and cycloalkyl hydrocarbons. Neopentadiol is resistant to water, chemicals and weatherability. The amino baking varnish has good light retention and does not yellowing. It can also be used as the raw material for producing polymerization inhibitor, stabilizer and insecticide.

Neopentylglycol Manufacturing Technique
Technical Principle
Isobutyraldehyde and formaldehyde react with hydroxyl aldehyde to form the intermediate hydroxyl neopentaldehyde under the aldol condensation reaction of alkali catalyst. Neopentaldehyde reacts with excessive formaldehyde to form neopentyl glycol under strong alkali condition, while formaldehyde is oxidized and reacts with alkali to form calcium formate.

————————→ (CH3)2C(CH2OH)2+HCOOCa

Technological Process
Using iso-butyraldehyde and formaldehyde as raw materials, using calcium hydroxide as catalyst and reactant, neopentaldehyde is prepared by condensation evaporation distillation process. In the condensation process, the feed kilogram volume ratio of iso-butyraldehyde and formaldehyde is 1:1.5-2.0. The molar ratio of feeding is isobutyraldehyde: formaldehyde: calcium hydroxide =1:2.5 - 3.5:0.58-0.65; The raw material concentration is 20-25% iso-butyraldehyde, 12-15% formaldehyde and 8-10% calcium hydroxide. Its character is: the condensation process using the following method of feeding: formaldehyde one-time feeding, uniform to feed iso-butyraldehyde, calcium hydroxide used for 92-95% of industrial grade purity, containing 5-8% of silicon magnesium aluminium and small amounts of impurities of heavy metals. Input 3-10 minutes in advance, i.e. 1/4 of the total amount added in the first half, 3/4 of the total amount added in the second half, and completely finished with isobutyraldehyde at the same time. The reaction temperature was controlled at 35-55℃ and the reaction time is 3-5 hours. After the reaction, adjust the pH value with formic acid, add bridge-building agent and sulfide precipitant. Silicon, magnesium, aluminium and a small amount of heavy metal impurities are precipitated under weak alkaline conditions, and then removed by filtration equipment. Then adjust the pH value, remove the excessive formaldehyde in the condensation solution through the pressure tower. Dealdehyde solution enters the evaporator, and the dilute formaldehyde returns to the condensation ingredients. During evaporation, neopentyl glycol and water rise to the evaporation tower in the form of vapor. After spraying condensate from the top of the tower, due to the different boiling points of the two, neopentyl glycol re-enters the evaporator, and water is removed from the evaporator through the condenser, thus achieving the effect of concentration. Calcium formate crystals are washed out and put into the crystallization assistant to obtain high quality by-product calcium formate. The evaporation liquid is further concentrated by distillation column and finally sliced into neopentyl glycol product by cooling.

Technological Characteristics
1,  This process adopts the innovative catalyst program feeding, enlarges the molecular ratio of formaldehyde feeding, can significantly improve the conversion rate of neopentyl glycol, make the conversion rate of neopentyl glycol reach more than 94%, the main product of neopentyl glycol grade 98 products reach 70%;

2,  By adding bridge-building agent and sulfide precipitant, this process can reduce the occurrence of side reactions and improve the by-product calcium formate purity to more than 99%, increase the added value of by-products;

3,  This process has the advantages of low investment, quick effect, simple process, good quality of main products and high added value of by-products;

4,  This process can reduce the cost of catalyst, obviously reduce the occurrence of side reactions, improve the hydroxyl value of the main product with good quality.
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