Oxygenated biofuels: Synthesis of fatty acid solketal esters with a mixture of sulfonated silica and (Bu4N)(BF4) catalyst

An Expedient Catalytic Process to Obtain Solketal from Biobased Glycerol

“…In the attempt to compare alternative Brønsted species, orthophosphoric acid was first considered but, when supported on silica (H 3 PO 4 •SiO 2 , 3.0 mmol/g) it gave a disappointing result on acetalization of glycerol (27% isolated yield), suggesting the importance of the acid strength [4]. At this point, finding other candidates seemed not straightforward as monoprotic donors were expected to be devoid of catalytic activity, accordingly to the popular SSA representation based on sulfuric acid esters with surface silanols [22][23][24][25][27][28][29][30][31][32].…”

“…To the best of our knowledge, SSA structure has not been fully characterized, possibly due to its amorphous nature. Most of the literature reports depicts it as a sulfuric acid ester of surface silanols [22][23][24][25][27][28][29][30][31][32], despite this model is unable to explain the known activity of supported monoprotic acids, nor of bisulfates. Sulfuric esters may correspond to possible transient states during the formation of SSA (or SSANa), but then hardly represents the final form, because of the known hydrolytic instability of silyl sulfones [46][47][48].…”

“…Therefore, dealing with simple/elegant solutions, suitable to industrial consideration, we were surprised to note that simple acids supported on silica received little attention in this field. Only a few reports considered the use of sulfuric acid on silica for glycerol acetalization [22][23][24][25], but the current technique require high temperature (130 • C), microwaves, or a large excess of acetone (20 eq) to gain acceptable conversions, so further study was needed to reveal its potential.…”

Sustainable Enzymatic Synthesis of a Solketal Ester—Process Optimization and Evaluation of Its Antimicrobial Activity

“…In the last years, the world production of biodiesel has generated a large volume of glycerol as a byproduct, which has become a promising feedstock for the sustainable synthesis of several added-value chemicals, including solketal-(2,2-dimethyl-1,3dioxolan-4-yl)methanol or 1,2-O-isopropylidene glycerol [1]. It is currently synthesized via ketalization reaction with acetone using homogeneous or heterogeneous acid catalysts [1,2]. Solketal has been successfully used to synthesize a variety of esters (fatty acid solketal esters-FASEs) used as potential fuel additives, lubricants, solvents, flavoring agents and plasticizers [3].…”

“…Usually, solketal-based esters have been synthesized by esterification or transesterification reactions using classical homogeneous or heterogeneous catalysts [2,3,5,9]. However, these reactions require high temperature (100-150 • C) and long reaction-times to reach high conversions [3,9].…”