Dialkyl Succinates and Adipates as Alternative Plasticizers-Even More Efficient Synthesis

As a result of strict regulations of phthalate plasticizers, alternative non-phthalate forms are desired and increasingly used. This work presents a synthetic method for alternative plasticizers (dialkyl succinates and adipates) via esterification of succinic and adipic acid with alcohols: butan-1-ol and 2-ethylhexan-1-ol. Ionic liquids were synthesized by the reaction of triethylamine with over-equimolar (1:2.7) amounts of sulfuric(VI) acid, which were used as an acidic catalyst and solvent. The two-phase liquid-liquid system was formed during the reaction due to immiscibility of the esters with the ionic liquid. This phenomenon is a driving force of this process, shifting the equilibrium toward the product formation. As a result, dialkyl succinates and adipates were obtained in high yields (99%) and selectivities (> 99%), under mild reaction conditions at 70-80 degrees C and using a 4:1 molar ratio of alcohol to acid and 15 mol% of catalyst. The catalyst was recycled 10 times without any loss of activity. This alternative method is highly competitive: it involves a simple procedure for product isolation as well as a high yield and purity of the resulting esters. These advantages make this method sustainable and promising for industrial applications.

Automated summary

A synthetic method for alternative plasticizers (dialkyl succinates and adipates) was presented via esterification reaction using ionic liquids as acidic catalyst and solvent, forming a two-phase liquid-liquid system. High yields and selectivities of the products were achieved under mild reaction conditions, with the catalyst being reusable. The method is competitive due to its simplicity in product isolation, high yield, and purity of the resulting esters, making it sustainable and promising for industrial applications.