tion. As a result, formulators of detergents incorporate costly
co-formulated chelating agents (phosphates, ethylenedi-aminetetraacetic acid, among others) that preferentially bind
to the ions to mitigate the effects of hard water and improve
performance. Petroleum dependence, limited selectivity, and
tunability of commercial surfactants, coupled with the use of
expensive and toxic chelating agents, drive the need to find
bio-renewable surfactants with improved properties. Superior
bio-products will incentivize further development efforts to
make sustainable products economically viable and competitive against existing fossil-based commercial counterparts. A
recent paper by Park, D.S., et al., “Tunable oleo-furan surfactants by acylation of renewable furans,” reveals a new renewable surfactant that boasts 100x greater hard water stability,
eliminating the need for chelating agents [ 3]. The result could
make bio-renewable detergent formulations even cheaper
than their petrochemical counterparts.
OLEO-FURAN SURFACTANTS: NATURAL
STRUCTURE FOR NATURAL FUNCTION
The natural oil- and sugar-derived structures of oleo-furan surfactants harness their inherent function for improved
detergency, solubility, and exceptional stability in hard water
conditions. OFS precursors are synthesized through the acylation of sugar-derived furan with natural oil-derived fatty acids.
Furan is synthesized renewably from xylose, a sugar found in
lignocellulosic biomass, while fatty acids are obtained from
hydrolysis of triglycerides found in various natural oils, such as
coconut and soybean oil (Fig. 1).
The synthesis of OFS molecules is highly tunable.
Surfactant properties can be selected by using different
sources of triglycerides and by coupling various chemistries
to obtain a wide range of surfactants incorporating linear or
branched structure—or different chemical functionalities.
Fatty acids with varying chain lengths, from 7 to 18 carbon
atoms, were used to synthesize a wide range of surfactants
with different hydrophobic tail lengths. The coupling of chemistries such as acylation, hydrogenation, aldol condensation,
and sulfonation aid in the synthesis of linear, branched, and
functionalized surfactants exhibiting high control over the tunability of reactions and surfactant structure. High yield and
selectivity (>90%) toward the desired OFS precursor can be
achieved in the presence of a zeolite catalyst. Using the aforementioned chemistry, 10 different OFS surfactant prototypes
were synthesized in high purity with variation in the chain
length and functionality of the hydrophobic group.
EVALUATION OF OFS PERFORMANCE:
ENHANCED HARD WATER STABILITY
Surfactant performance was evaluated by testing standard
properties, such as critical micelle concentration (CMC), Krafft
point, foaming, wetting, and stability in hard water. Ideally, surfactants should possess low CMC and Krafft points to ensure
a wide range of operating conditions, especially in detergency
applications. In comparison with LAS, OFS surfactants were
found to have similar values of CMC and lower Krafft points,
enabling application in dilute conditions and cold water. More
importantly, OFS were found to possess superior detergency in
FIG. 1. Natural structure. Oleo-Furan Surfactants are renewably synthesized via tunable reaction chemistries from biomass-derived
furans and fatty acids obtained from triglycerides.
Fatty Acids Furan
Side-Chain Aromatic Linker
Biomass-derived furan ring
Natural Oils Fatty Acids
Anionic, cationic, nonionic
e.g. sulfonate or sulfate
Source: Fatty acids derived