Continuous‐Flow O‐Alkylation of Biobased Derivatives with Dialkyl Carbonates in the Presence of Magnesium–Aluminium Hydrotalcites as Catalyst Precursors

Abstract

The base-catalysed reactions of OH-bearing biobased derivatives (BBDs) including glycerol formal, solketal, glycerol carbonate, furfuryl alcohol and tetrahydrofurfuryl alcohol with non-toxic dialkyl carbonates (dimethyl and diethyl carbonate) were explored under continuous-flow (CF) conditions in the presence of three Na-exchanged Y- and X-faujasites (FAUs) and four Mg-Al hydrotalcites (HTs). Compared to previous etherification protocols mediated by dialkyl carbonates, the reported procedure offers substantial improvements not only in terms of (chemo)selectivity but also for the recyclability of the catalysts, workup, ease of product purification and, importantly, process intensification. Characterisation studies proved that both HT30 and KW2000 hydrotalcites acted as catalyst precursors: during the thermal activation pre-treatments, the typical lamellar structure of the hydrotalcite was broken down gradually into a MgO-like phase (periclase) or rather a magnesia-alumina solid solution, which was the genuine catalytic phase.

Solid acid catalyzed carboxymethylation of bio-derived alcohols: an efficient process for the synthesis of alkyl methyl carbonates

“…Cattelan et al explored the catalytic activity of Mg–Al hydrotalcites for the valorization of OH-bearing bio-derived chemicals with non toxic DMC and DEC (Diethyl carbonate). The biomolecules such as glycerol formal, solketal, glycerol carbonate, furfuryl alcohol and tetrahydrofurfuryl alcohol have been successfully transformed with good yield of desired carbonate in continuous flow system 40 . In addition, the other base catalysts such as CsCO 3 41 , nanocrystalline-MgO, MgLa mixed oxides 15 , 29 , K 2 CO 3 42 , 43 , KW2000, basic Al 2 O 3 , acidic Al 2 O 3 28 , 38 , KF/α-Al 2 O 3, KF/TiO 2 , CsF 27 , 1,8-diazobicyclo[5.4.0]undec-7-ene (DBU) 44 etc have also been reported for DMC mediated carboxymethylation of various alcohols.…”

Renewable Aromatics from Kraft Lignin with Molybdenum‐Based Catalysts

“…The choice of Catalox SBa‐150 (Sasol) as the alumina support was based on its well‐defined properties and widespread industrial use. The magnesium–aluminium hydrotalcite, KW2000 (Kyowa Industries), was chosen on the basis of its previously reported performance for alkylation chemistry at high temperatures …”

Applications of Dimethyl Carbonate for the Chemical Upgrading of Biosourced Platform Chemicals

“…The 276 reaction outcome was greatly improved in the continuous-flow 277 mode by using a catalyst (c-HT30) composed of a mixture of 278 Mg/Al oxides obtained by the calcination of a hydrotalcite 279 precursor (Scheme 3, left, bottom). 46 Under such conditions, 280 quantitative conversion and O-methylation selectivities were 281 reached at atmospheric pressure, and even more importantly, 282 the productivity of the process (∼2 g prod g cat −1 h −1 ) was up to 283 200 times higher than that of the previous batchwise method. 284 Moreover, the flow-mode protocol proved effective also for the 285 etherification of glycerol carbonate and tetrahydrofurfuryl 286 alcohol, the latter deriving from sugars dehydration.…”