Conversion of carbohydrates to organic acids using Lewis acid catalysts in aqueous medium.

Abstract

The increasing use of renewable feedstocks to produce fine chemicals, pharmaceuticals, and biofuels for industrial applications is due to the need to replace a range of petroleum-based products with sustainable alternatives. This way, carbohydrate conversion to organic acids have an important role in their possible conversion to several high-value-added chemicals, fuel and/or food additives, and polymeric materials. In this study, sugarcane molasses containing sucrose, glucose, and fructose were converted to organic acids such as levulinic and lactic acids using different Lewis acid catalysts in aqueous media. Aluminum and zinc nitrate and chloride were used in two reaction systems based on conventional and microwave heating. Stainless steel and glass reaction vessels were used for this purpose, respectively. The conversion was evaluated for different reaction times and temperatures. Lactic acid predominated as a product from the retro-aldol reaction of fructose, reaching 70% molar yield using aluminum nitrate in a stainless-steel reactor with conventional heating. Besides lactic acid, a small amount of formic and levulinic acids and 5-(hydroxymethyl)-furfural (5-HMF) were obtained as co-products. The temperature regime was a critical parameter to achieve high yields and good selectivity for lactic acid in these reaction systems.