Diesel fuel properties of renewable polyoxymethylene ethers with structural diversity

Polyoxymethylene ethers (POMEs) are a class of low-soot and high-cetane oxygenate oligomers of structure RO(CH2O-)n-R, with different chain lengths (n) and end-groups (R) that determine their diesel-like fuel properties. Commercial POMEs with methyl end-groups (MM-POME3-6) exhibit undesirably low energy density and high water solubility. A previous computational assessment indicated that the lower heating value (LHV) and water solubility for MM-POME3-6 both improve upon end-group exchange with larger butyl, iso-butyl and iso-pentyl end-groups. Here, we expanded upon our initial trans-acetalization reaction that employed 1-butanol to install butyl end-groups to also include branched, higher carbon-number end-groups using iso-butanol and fusel oil as reagents. These new products are termed iB*POME1-6, and FOil*POME1-5, respectively, and collectively referred to as R*POMEs. They possess the advantaged properties of the parent MM-POME3-6 while exhibiting higher LHV (31 MJ kg-1 and 28 MJ kg-1 for iB*POME1-6, and FOil*POME1-5, respectively) and much reduced water solubility (2.7 g L-1 and 1 g L-1 for iB*POME1-6, and FOil*POME1-5, respectively). Additional fuel property analyses were performed using 20 vol% blends of the R*POMEs with a base diesel fuel. Overall, the greater energy density and decreased water solubility of the R*POMEs, as well as their synergistic blending with diesel at moderate blend levels, provide the greatest benefits to consumers and position this group of products as an environmentally friendlier blendstock alternative to the commercially-available MM-POME3-6.