On the oligomerization mechanism of Brønsted acid-catalyzed conversion of furans to diesel-range fuels

Abstract

a b s t r a c tThe conversion of biomass to fuels and chemicals is considered to be a promising alternative to petroleumbased conventional routes. The oligomerization of biomass-derived furans can yield an important precursor toward diesel fuel; yet, the underlying mechanism is not well understood. This study investigates the furan oligomerization mechanism and kinetics via density functional theory and microkinetic modeling. The oligomerization proceeds in the presence of water and a Brønsted acid and requires an aldehyde and two furan molecules, each with at least one unprotected ␣-C. If only furans are present in the acidic, aqueous environment, the initial hydrolysis to produce the aldehyde limits the oligomerization rate. Two strategies to accelerate the oligomerization are proposed: furnishing the furans with electron-donating substituents or supplying a non-self-condensing aldehyde in the reaction mixture.

Production of renewable toluene from biomass-derived furans via Diels-Alder and dehydration reactions: A comparative study of Lewis acid catalysts

“…Also, it has been reported that Brønsted acids catalyze the hydrolysis of MF to 4-oxopentanal and the subsequent trimerization of 4-oxopentanal with two MF molecules [19,20]. This suggests that Brønsted acids may not be a suitable choice for the conversion of MF.…”

Selective Synthesis of 4,4′-Dimethylbiphenyl from 2-Methylfuran

“…The hydrolysis of MF into 4-oxopentanal is observed as a major side reaction. This is ascribed to the furan ring-opening of MF with water (a byproduct of the homocoupling) under acidic conditions, as previously observed by Nikbin et al − Oligomerization of MF into trimers is also known to proceed in the presence of water and acid. − A high TFA concentration is favorable for both selectivity and yield to DMBF (Table ). This result suggests that the acid plays an important role in the reaction mechanism (see below).…”

Water-promoted selective heterogeneous catalytic trimerization of xylose-derived 2-methylfuran to diesel precursors

“…In the absence of water, ␣-carbocations are at a much lower concentration than ␤-carbocations, thus tetramerization of 2-MF was preferred [18]. In the aqueous acid catalysis of 2-MF, only the ␣-carbocation is active and can undergo ring opening [19]. The presence of water may stabilize the formation of ␣-carbocations, which further reacted with water and formed a trimer via hydrolytic ring-opening.…”