Application of Alkoxyalkanoates (AOAs) as Renewable Diesel Blendstocks from Chemical Coupling of High-Yield Fermentation Products

Abstract

Combustion of liquid fossil fuels for transportation is a major source of carbon emissions only partially offset by the incumbent renewable alternativesbiodiesel, renewable diesel, and ethanol. New renewable ground transportation fuels derived from abundant sources of biomass, and utilizing carbon-efficient bioprocessing, are needed to further offset fossil fuel use. Low carbon intensity liquid fuels are especially required for medium- to heavy-duty engine architectures supporting the long-range transportation fleet. Realization of substantial carbon efficiency gains in renewable fuel production can be achieved by extending feedstocks beyond lipids, which are the primary bioderived source material for biodiesel and renewable diesel. Toward these ends, chemical upgrading of the high carbon yield, central metabolism-derived intermediates, glycolic acid, lactic acid, and 4-hydroxybutyrate with various fermentation-derived alcohols was accomplished using standard chemical transformations to provide a class of compounds that show promise as an alternative to petroleum diesel. Fuel property testing of these C7–C22 hydroxyalkanoate-derived compounds demonstrated improved cold temperature performance compared to biodiesel (cloud point temperatures < −50 °C) and improved derived cetane number (DCN) and sooting metrics compared to renewable diesel, providing the technical basis for a new high-performance renewable blendstock for decarbonization of heavy-duty transport.

High performance alkyl dialkoxyalkanoate bioderived transportation fuels accessed using a mild and scalable synthetic protocol

“…DAOA lifecycle assessment was performed by analogy to the rigorous analysis performed for AOA s, which utilize similar biological feedstocks and chemical processes. 10 For AOA s, lignocellulosic biomass is fermented to produce lactic acid and fusel alcohols, which are in turn combined in sequential esterification and etherification units to generate AOA s. A key result of the analysis is that a reduction from 92 to 31 g CO 2 e per MJ (65%) is anticipated for the AOA lifecycle relative to conventional petroleum diesel, which is one of the largest reductions among recent sustainable diesel concepts and exceeds biofuel emission targets of 60% lifecycle CO 2 reduction. 4,5 Interestingly, the primary source of GHG production during the AOA lifecycle comes indirectly from NaOH usage in the deacetylation and mechanical refining (DMR) of biomass to aid in enzymatic hydrolysis, which presents opportunities for future optimization.…”

“…[6][7][8][9] Our group initially investigated lactate ester-ethers (alkyl alkoxyalkanotes or AOAs) that were synthesized in two steps from lactic acid. 10 (Scheme 1) while derived cetane number 43.6, YSI per kg 324, cloud point < −50 °C and LHV 32.1 of isopentyl 2-(isopentyloxy)propanoate was promising, the etherication requires hazardous and toxic reagents, dry solvent and inert atmosphere. A milder route featuring reductive etherication of the corresponding pyruvate ester-ketal was proposed.…”