Blended fuel property analysis of butyl-exchanged polyoxymethylene ethers as renewable diesel blendstocks

Abstract

Methyl-terminated polyoxymethylene ethers (MM-POMEs), having the formula CH3O-(CH2O)n-CH3 (n = 3–6), are a class of oxygenates with desirable diesel-like fuel properties including high cetane number and low soot formation. However, their low energy density and high water-solubility present barriers to their adoption. Both concerns were recently addressed by our research group by synthesizing a mixture of POME structures having butyl end-groups and n = 1–6, termed B*POME1–6. B*POME1–6 maintained the advantageous properties of the parent MM-POMEs, and exhibited improved energy density and most notably, dramatically decreased water solubility. For evaluation against a set of criteria for a blended diesel blendstock, a 20 vol% blend of B*POME1–6 with a base diesel fuel was investigated here. Oxidation stability, cetane number, sooting tendency, lubricity and conductivity were improved in the B*POME1–6 blend compared with the base diesel, while also maintaining the flash point, cloud point, energy density, viscosity, and boiling point requirements. The B*POME1–6 product demonstrated a synergistic blending behavior at 10 vol% and a linear blending behavior at 20–30 vol% blends, in agreement with similar POME blends at comparable blend levels. Finally, common environmental and toxicity models performed on B*POME1–6 component molecules suggested they have a greater propensity to partition into the water compartment compared to a common diesel surrogate, but with a lower tendency to bioaccumulate.