Pickering Interfacial Catalysts for solvent-free biomass transformation: Physicochemical behavior of non-aqueous emulsions

• Glycerol/dodecanol emulsions were prepared using amphiphilic silica particles.
• The particles contained a combination of alkyl and sulfonic acid surface groups.
• The droplet size was reduced until a concentration of 1 wt.% of silica particles.
• Ostwald ripening and flocculation were the main destabilization mechanisms.
• The particles catalyzed the etherification of glycerol with dodecanol at 150 °C.

A key challenge in biomass conversion is how to achieve valuable molecules with optimal reactivity in the presence of immiscible reactants. This issue is usually tackled using either organic solvents or surfactants to promote emulsification, making industrial processes expensive and not environmentally friendly. As an alternative, Pickering emulsions using solid particles with tailored designed surface properties can promote phase contact within intrinsically biphasic systems. Here we show that amphiphilic silica nanoparticles bearing a proper combination of alkyl and strong acidic surface groups can generate stable Pickering emulsions of the glycerol/dodecanol system in the temperature range of 35–130 °C. We also show that such particles can perform as Pickering Interfacial Catalysts for the acid-catalyzed etherification of glycerol with dodecanol at 150 °C. Our findings shed light on some key parameters governing emulsion stability and catalytic activity of Pickering interfacial catalytic systems. This understanding is critical to pave the way toward technological solutions for biomass upgrading able to promote eco-efficient reactions between immiscible organic reagents with neither use of solvents nor surfactants.

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