Ethyl hexanoate rich stream from grape pomace: A viable route to obtain fine chemicals from agro by-products

Abstract

A novel viable route for obtaining ethyl hexanoate-rich streams from grape pomace, an agro by-product generated from the winery industry, was investigated. Highly concentrated hexanoic acid (87 wt%) was efficiently produced through the chain elongation fermentation of red and white grape pomace, easily separated, recovered and reacted with ethanol by using AlCl3·6H2O as a catalyst. Under the optimised mild reactive conditions (molar ratio acid:ethanol:catalyst of 1:2:0.1, 5 h, 348 K), a high conversion equal to 93.5 % was achieved in a single step. AlCl3·6H2O was very effective in catalysis, playing an additional key role in the separation of products, shifting the equilibrium of the reaction and making products' recovery easier. After the reaction cycle, the catalyst was easily recoverable and reusable without losing effectiveness. According to this simple layout of processes, including the anaerobic digestion of the residual part of grape pomace, a specific production cost of 0.935 €·kg−1 was calculated related to the final products. This proposed approach could represent a promising green and sustainable route to produce ethyl esters of volatile fatty acids from agro by-products.