Trimethylolpropane, TMP, cas 77-99-6, is a widely used chemical material, which can be used to prepare alkyd resin coatings, polyurethane foam, plasticizers, stabilizers, surfactants and various polyether polyols.
There are two production methods that are more commonly used.
1. Cross-canizalolol condensation method
Cross-canizalol condensation method is also known as sodium formate method. The aqueous solution of n-butyraldehyde and formaldehyde under the action of an alkaline catalyst for alcohol-formaldehyde condensation reaction to generate 2,2-dimethylbutyraldehyde, 2,2-dimethylbutyraldehyde and excess formaldehyde in strong alkaline conditions cross-canizaro reaction to generate trimethylolpropane, formaldehyde is oxidized to formic acid, formic acid and sodium hydroxide neutralization to generate sodium formate, the reaction mixture and then desalted, refined to qualified products. The relevant reaction equation is:
The use of organic tertiary amine as a catalyst, separation is easier, but the catalyst is expensive, resulting in increased production costs of trimethylolpropane; calcium hydroxide (or calcium oxide) due to the small solubility in water, most of it can be precipitated out, the rest can be separated by centrifugation and film separation method, the separation of calcium formate can be used directly for feed additives, preservatives, etc., easy to use, the market is better, Currently, most of the trimethylolpropane is produced using this catalyst.
2. Aldehyde hydrogenation reduction method
N-butanol and formaldehyde in the catalytic effect of trialkylamine (such as triethylamine) to obtain hydroxyl aldehyde condensation products 2,2-dihydroxymethylbutyraldehyde, and then in the presence of a catalyst, 2,2-dihydroxymethylbutyraldehyde aqueous hydrogenation to produce trimethylolpropane. The reaction equation is:
In the hydroxyl aldol condensation, triethylamine is mainly used as a catalyst. The catalyst of hydroxyl aldol condensation reaction with triethylamine can control the selectivity of the reaction, inhibit the occurrence of side reactions and reduce the generation of formate. The aqueous hydrogenation catalyst is mainly distributed on the carrier of nickel or nickel oxide, but also available copper chromite, copper oxide or copper-chromium as a co-catalyst. The aldehyde hydrogenation reduction method has high utilization rate of formaldehyde, strong hydrogenation technology, can save a lot of formaldehyde and alkali, relatively few side reaction products, good product quality, purification and refinement is relatively simple, less equipment, low production costs, but the need for hydrogenation equipment, high-pressure equipment, hydrogenation equipment and catalyst requirements are high, the production technology requirements are also high, more suitable for large-scale continuous production. At present, some trimethylolpropane manufacturers in Europe and America mainly use this method for production.
