In Situ Biocatalytic Synthesis of Butyl Butyrate in Diesel and Engine Evaluations

Abstract

Blending petroleum fuels with biofuels is likely to become increasingly important over the years to come. Butyl butyrate has promising characteristics as a blend component in diesel and can be synthesized by lipase‐catalyzed esterification of 1‐butanol and butyric acid, which both can be derived from fermentation technologies. In the current study, the enzyme load and reaction temperature were optimized for the production of butyl butyrate with Novozyme 435 (immobilized Candida antarctica lipase B) directly in diesel at a substrate concentration of 1 m using a molar ratio of 1:1 between n‐butanol and butyric acid. Optimum conditions were found by using a central composite design at an enzyme load of 12 % of substrate weight and a temperature of 57 °C, giving 90 % yield conversion in 30 min, corresponding to a butyl butyrate productivity of 1.8 mol L−1 h−1. Diesel blended with 5, 10, and 30 % butyl butyrate was tested in a heavy‐duty diesel engine under two load cases. The ignition properties of the blended fuels were very similar to pure diesel, making butyl butyrate an interesting diesel substitute. The emission analysis demonstrated lower soot and CO emissions, similar hydrocarbons levels and slightly increased NOx levels compared with using pure diesel. The high activity of lipase in diesel and the compatibility between diesel and butyl butyrate opens up the possibility to develop fuel blending systems where the synthesis of the blend‐in component occurs directly in the fuel.

Novozym 435: the “perfect” lipase immobilized biocatalyst?

“…In a very interesting paper, N435 was used to esterify 1-butanol and butyric acid using diesel as the reaction medium, with a 90% yield. 263 The diesel thus modified has some improved properties. Another paper shows that butyric acid and ethanol were esterified in n-hexane using N435.…”

Metabolic engineering of Escherichia coli for the production of butyric acid at high titer and productivity

“…Butyric acid esters are common in the food and cosmetic industries as flavor and fragrant additives. Ethyl and butyl esters of butyric acid can directly serve as renewable fuel to mitigate petroleum use [ 2 ]. Further, butyric acid can be reduced chemically or biologically to butanol, a drop-in biofuel [ 3 ].…”

Advanced biofuels: Perspectives and possibilities

“…Under appropriate conditions, butyrate can be combined with butanol as produced or separately to generate butyl butyrate, an eight-carbon ester as a drop-in biofuel for diesel (Noh et al, 2018;Sjoblom et al, 2017;Xin et al, 2016). Although butyl-butyrate production by microbial biocatalysts has been demonstrated, toxicity of this ester to the microorganism precludes the production of this ester at high concentration by fermentation (Wilbanks and Trinh, 2017).…”