Combustion of n-butyl acetate synthesized by a new and sustainable biological process and comparisons with an ultrapure commercial n-butyl acetate produced by conventional Fischer esterification

Abstract This paper reports a study of the combustion dynamics of n-butyl acetate (BA) using the configuration of a burning droplet. Two grades of BA were examined: one (SBA) synthesized by a new process described in the paper that uses a metabolically engineered solventogenic Clostridium strain through an extractive fermentation process using n-hexadecane as the extractant; and one commercially available as a high-purity (99.9%) ‘neat’ BA grade produced by conventional Fischer esterification (NBA). The initial droplet diameter was primarily 0.6 mm with some limited experiments carried out for 0.4 mm droplets to show the influence of convection. Experiments were performed in the standard atmosphere and ignition was by spark discharge. The results showed the presence of impurities in the SBA at mass concentrations totaling about 6% which included n-butanol, n-hexadecane, iso-propyl alcohol and ethyl acetate. Droplet burning rates and flame structures were not influenced by these impurities at this concentration level. In the presence of convection created by buoyancy, droplets burned faster with stretched flames and a luminosity revealing the presence of soot by incandescence at the flame tips. Reducing the initial droplet diameter to 0.4 mm eliminated the convective effect and resulted in near spherical flames. The results presented show that the new synthesis process is a sustainable alternative for BA production with burning characteristics identical to NBA in both convective and stagnant gas transport fields.