Aldol Condensation of Furfural with Acetone Over Mg/Al Mixed Oxides. Influence of Water and Synthesis Method

Abstract

Aldol condensation of furfural and acetone (an important initial step to obtain diesel from biomass) was studied over MgAl mixed oxides. The influence of the utilization of microwaves and/or a surfactant (Pluronic 123) during the synthesis as well as the use of water (either pre-hydrating the solids before catalytic studies or in water/toluene mixtures as the reaction medium) is discussed. The combined use of Pluronic 123 and microwaves led to solids with bigger pore sizes, exhibiting lower basicity and higher acidity than the conventional synthetic method, thus resulting in an increase in the yield of the desired product of condensation, comprising two molecules of furfural and one of acetone (F2Ac). As for the influence of water, re-hydration of the mixed oxides was detrimental to activity, probably as a result of the partial blocking (solvation) of active sites. On the contrary, the increase in water percentage in the reaction medium resulted in higher conversions, though selectivity to F2Ac decreased. The weakening of the C=O bond of furfural in the presence of water as well as the higher solubility of the first condensation product (FAc) in toluene, as compared to water, could account for that. A 44.5% yield of F2Ac (66% conversion) after 16 h was obtained with the most active solid, which maintained the activity for three consecutive reactions.

Catalytic applications of layered double hydroxides in biomass valorisation

“…A related study of MgAl-LDH explored the impact of water:toluene solvent ratio; added water ( ≤50 vol%) increased the C8 product yield from 14 to 70 %, attributed to partitioning of this intermediate in the organic phase and hindering subsequent reaction. 55 Calcined LiAl-LDHs (Li:Al of 0.5) synthesised by mechanochemical methods have been explored for aldol condensation of acetone and furfural, and exhibit higher base site loadings and reaction rates than Mg3Al-LDH. 56 Calcined MgFe-LDH (Mg:Fe of 1 to 10) are also active for acetone and furfural condensation, with a balance of acid and base sites necessary to achieve both condensation and dehydration steps to form the stable enone; while increasing Mg content enhanced furfural conversion, dehydration was favoured over acidic materials with Mg:Fe≤ 5.…”

Rate-Enhancing Role of Water in H-BEA and Sn-BEA for Keto–Enol Tautomerization of Acetone: A DFT Study

“…Mixed-aldol condensation of acetone with furfural has been studied using a variety of catalysts. − Among different catalysts, several properties of zeolites make them the preferred choice for several reactions. A defect-free all-silica zeolite is generally inactive.…”

Effect of Ni Metal Content on Emulsifying Properties of Ni/CNTox Catalysts for Catalytic Conversion of Furfural in Pickering Emulsions

“…[21,22] The relevance of FAL catalytic conversion comes from the large number of chemicals and biofuels that can be obtained from its transformation. [23][24][25][26][27] FAL can be converted to long-chain products by CÀ C coupling condensation reaction, [28,29] valuable fuel additives such as 2-methyltetrahydrofuran (2-MTHF) [30] and furfuryl ether (FFE), [31,32] and to value-added compounds such as furan by decarbonylation, [33] furfuryl alcohol by hydrogenation [34,35] and by hydrogenation/ ring rearrangement to cyclopentanone (CPO). [36][37][38][39][40] Particular focus has been put on the transformation of furfural to aliphatic cyclic molecules such as cyclopentanone and cyclopentanol because they are important intermediate in fine chemical industry with a broad range of application in the perfume, medicine, and agriculture field.…”

“…The relevance of FAL catalytic conversion comes from the large number of chemicals and biofuels that can be obtained from its transformation [23–27] . FAL can be converted to long‐chain products by C−C coupling condensation reaction, [28,29] valuable fuel additives such as 2‐methyltetrahydrofuran (2‐MTHF) [30] and furfuryl ether (FFE), [31,32] and to value‐added compounds such as furan by decarbonylation, [33] furfuryl alcohol by hydrogenation [34,35] and by hydrogenation/ring rearrangement to cyclopentanone (CPO) [36–40] …”