Synthesis of bio-plasticizers derived from renewable organic acids and n-butanol by heterogeneous catalysis

ACUÑA, YANINA M.; AGUZÍN, FEDERICO L.; BEDOGNI, GABRIEL A.; PADRÓ, CRISTINA L.; OKULIK, NORA B.

Ciudad Autónoma de Buenos Aires

Congreso; WCCE11 - 11th World Congress of Chemical Engineering; 2023

Asociación Argentina de Ingenieros Químicos

The current paradigms of chemical engineering contemplate the integral use of the renewable sources for the sustainable development of societies [1]. In this sense, the aim is to replace plasticizers based on petrochemical phthalates, which have low biodegradability and considerable toxicity, by others obtainable from renewable sources. Succinic acid (SA), citric acid (CA) and malonic acid (MA) and n-butanol (BtOH), can be obtained by biomass fermentation. By esterification of the AS, AC or AM with BtOH, the esters: dibutyl succinate (DBS), tributyl citrate (TBC) and dibutyl malonate (DBM), can be produced becoming sustainable alternatives for bio-plasticizers. This esterification reactions involve the use of catalysts to obtain good yields.The goal of this work is to study the effect of reaction conditions and catalyst nature in the synthesis of DBS, TBC and DBM bioplasticizers. The commercial resin Amberlyst 36 (A36), the commercial mesoporous carbon Starbon and tungstophosphoric acid (HPA) supported on activated carbon (HPA-AC), were used as catalysts.The reactions were carried out in a batch reactor with periodic sampling, analyzing reactants and products by chromatography (liquid and/or gas). The reaction conditions, catalyst load (0.5 to 1.5 wt%), reaction temperature (60 to 120 °C), stirring rate (600 to 1000 rpm) and molar ratio of reactants (1:30 to 1 :10 - acid:alcohol), were studied using A36 as catalyst. From these experiments the best values of these parameters were selected for further evaluation of the catalysts. The temperature showed the greatest influence on the yield of the esters of interest, while the others parameters evaluated showed a minor effect on the esterifications. The catalytic activity results of the catalysts showed that both conversion and selectivity and, consequently, the yield towards the multisubstituted products increase with acidity. In the case of DBS, the yields are of the order of 11% with HPA-AC and 34% with Starbon, lower than those obtained with A36 (61%), catalyst with higher concentration of acid sites. In the case of malonic and citric acids, high yields are observed towards monosubstituted derivatives (and disubstituted for CA), while the yields towards TBC and DBM are 8% and 24%, respectively.From these results it is concluded that bio-plasticizers can be obtained from renewable raw material, however the yield achieved depends on the acidity and the reaction conditions.