1,3-Butanediol CAS 107-88-0

Propylene and formaldehyde react as follows in the presence of an acidic catalyst:

Reactions (5) and (6) belong to typical Prins addition reactions. The Prince reaction of propylene with formaldehyde needs to be carried out in polar solvents and acidic catalysts. Commonly used solvents are water, ethanol and acetic acid, etc. Studies have shown that acetic acid is the most ideal solvent. The catalyst can be H2SO4, BF3, HClO4, etc., among which HClO4 has the best catalytic effect. However, due to the strong corrosiveness of H2SO4 and HClO4, H+ type cation exchange resin is used as the catalyst in actual production.

The composition of the Prince reaction product of propylene and formaldehyde is more complicated. The main product is 1,3-butanediol, and the by-products are 4-methyl-1,3-dioxane, formal, etc. When acetic acid is used as a solvent, 1,3-butanediol acetates are by-products. The 4-methyl-1,3-dioxane hydrolysis method can improve the yield of 1,3-butanediol, that is, the reverse reaction of reaction (6) is carried out.

The condensation hydrolysis of propylene and formaldehyde was industrialized in the 1970s. The specific process adopts a two-step method, replacing the H2SO4 catalyst with a KU-2(H+) cation exchange resin. The first step: 4-methyl-1,3-dioxane prepared by condensation of propylene and formaldehyde solution; the second step: 4-methyl-1,3-dioxane in the presence of methanol Hydrolysis, the function of methanol is to condense with the hydrolyzed formaldehyde into easily separated methylal.

The process flow is briefly described as follows: After preheating the industrial grade formaldehyde aqueous solution and the industrial propylene-propane mixture respectively, they are fed through the bottom of the vertical tubular reactor to carry out the condensation reaction. The reactor is equipped with KU-2 (H+) type Cation exchange resin reaction conditions: 100~110℃, 30×105~40×105Pa. The condensation reaction product is decompressed to 1.0×105Pa and then sent to the 1# tower to separate propane and unreacted propylene, and the recovered propylene can be recycled after purification. The reaction product of removing propylene propane is composed of: 4-methyl-1,3-dioxane, water, methylal and a small amount of high boilers; the reaction product of removing propylene propane is in the 2# tower. head, remove methanol and methylal; separate propane and unreacted propylene, the recovered propylene can be recycled after purification; in the 3# tower, remove methanol and methylal; separate propane and unreacted propylene, The recovered propylene can be recycled after purification treatment; 4-methyl-1,3-dioxane and water are distilled out in the form of azeotrope, and the azeotrope is 88°C. The organic phase separated from the azeotrope is mixed with methanol in a ratio of 1:3 through a mixer, and then passed into a vertical hydrolyzer for hydrolysis. The hydrolyzer is also equipped with KU-2 (H+) type cations exchange resin. Hydrolysis conditions: 80~90℃, feed rate 25h-1. The conversion rate of 4-methyl-13-dioxane is higher than 85%. The hydrolyzed product is rectified in the 4# rectification tower to obtain high-purity 1,3-butanediol. 4# rectification tower operating conditions: 104℃, 1.33kPa