Production of 5-hydroxymethylfurfural from glucose using aluminium doped MCM-41 silica as acid catalyst

Abstract

Mesoporous aluminium doped MCM-41 silica catalysts were prepared by a sol–gel method in two reaction steps (acid and alkaline hydrolysis) from joint hydrolysis of tetraethylortosilicate (TEOS) and aluminium triisoproxide, using n-dodecylammonium chloride as surfactant, at room temperature, and subsequent calcination at 550°C. Two solids with different Si/Al molar ratios (5 and 10) were synthesized, which possess high specific surface area and acidity, with both Brönsted and Lewis acid sites. By using a biphasic water/MIBK as reaction medium and a 30wt.% of the 10Al-MCM catalyst with respect to the substrate weight (glucose), 87% of glucose conversion and 36% of HMF yield were achieved at 195°C after 150min of reaction time. The reaction is quite selective toward HMF, since only fructose was detected as by-product, but neither levulinic acid nor furfural were found. Moreover, the use of a sodium chloride aqueous solution (20wt.%) and MIBK ameliorates the partition coefficient between the organic and the aqueous phases up to 1.9, leading to an enhancement of the glucose conversion and HMF yield, attaining values of 98% and 63%, respectively, in a time as short as 30min. The catalytic performance of this acid solid, associated to the presence of strong acid sites, is well maintained after three catalytic cycles.