Production of Biomass‐Based Automotive Lubricants by Reductive Etherification

Abstract

Growing concern with the effects of CO emissions due to the combustion of petroleum-based transportation fuels has motivated the search for means to increase engine efficiency. The discovery of ethers with low viscosity presents an important opportunity to improve engine efficiency and fuel economy. We show here a strategy for the catalytic synthesis of such ethers by reductive etherification/O-alkylation of alcohols using building blocks that can be sourced from biomass. We find that long-chain branched ethers have several properties that make them superior lubricants to the mineral oil and synthetic base oils used today. These ethers provide a class of potentially renewable alternatives to conventional lubricants produced from petroleum and may contribute to the reduction of greenhouse gases associated with vehicle emissions.

Synthesis of Biomass‐Derived Ethers for Use as Fuels and Lubricants

“…Ethers derived from biomass also have the potential to replace petroleum‐derived automotive lubricants . Transportation vehicles consume almost 30 % of energy produced today, and of that approximately one third is lost due to friction and wear .…”

“…The currently used synthetic automotive lubricant consists of poly‐alpha‐olefins (PAO), which are derived from petroleum through the oligomerization of α‐olefins . However, as shown in Table , recent reports showed that branched ethers such as 11‐{[(2‐ethylhexyl)oxy]methyl}tricosane have comparable lubricant properties and can be synthesized from renewable sources . Branches in the alkyl portions of ethers reduce the PP and increase the viscosity of the ether, enhancing the lubricant properties .…”

“…This method is also relatively ineffective for the synthesis of asymmetrical linear ethers because the alcohols will self‐couple to generate symmetrical ethers. Reductive etherification of alcohols with aldehydes and ketones provides an alternative approach for producing high yields of symmetrical and asymmetrical ethers with a variety of structures and degrees of carbon chain branches …”

“…Various catalytic pathways involving condensation, reduction, acetalization, and dehydration have been identified for producing liquid fuels from biomass‐derived platform chemicals . Ethers have emerged as a class of molecules with excellent properties that can be used to meet the growing demands for gasoline additives, cetane enhancers for diesel fuel, automotive lubricants, and other valuable products …”

Effect of Alcohol Structure on the Kinetics of Etherification and Dehydration over Tungstated Zirconia

“…[1] Ethers have attractedr ecent interest as renewable fuels and lubricants. [6] Longer chain branched ethers in the C 28 -C 32 range have low pour points ande xcellent lubricant properties, [7][8][9] and could replace poly-alpha-olefin lubricants,which are produced fromf ossil reserves. [2][3][4][5] Branched ethers such as methyl tert-butyle ther can also be added to gasoline because of their high octanen umbers.…”