Glycerol acetals as diesel additives: Kinetic study of the reaction between glycerol and acetaldehyde

Certain acetals can be produced from renewable resources (bioalcohols) and seem to be good candidates for different applications, such as oxygenated diesel additives. This paper addresses the production of acetals (5-hydroxy-2-methyl-1,3 dioxane and 4-hydroxymethyl-2-methyl-1,3 dioxolane) from glycerol and acetaldehyde using Amberlyst 47 acidic ion exchange resin. This ion exchange resin performed well, recording 100% selectivity toward acetal formation at a suitably high initial glycerol concentration. When the initial acetaldehyde concentration was significantly higher than the glycerol concentration, 2,4,6 trimethyl-1,3,5 trioxane was the main reaction product. Unlike other acetalization reactions, the one studied here does not have thermodynamic limitations, and 100% conversion is achieved under different reaction conditions. A kinetic study was performed in a batch stirred tank reactor to study the influence of different process parameters, such as temperature, feed composition and stirring speed. A pseudo-homogeneous kinetic model was developed to describe this reaction kinetics, proving that its rate is just first order on the acetaldehyde concentration under the conditions studied.