Synergistic Production of Methyl Lactate from Carbohydrates Using an Ionic Liquid Functionalized Sn‐Containing Catalyst

Abstract

Considerable progress has been made recently in the catalytic conversion of renewable biomass resources to methyl lactate (MLA). However, conceiving eco-friendly and effective catalytic systems for the production of MLA from biomass carbohydrates remains a key challenge. Herein, we report a multifunctional catalyst Sn(salen)/IL, consisting of a Sn(salen) complex and an imidazolium-based ionic liquid (IL), which acts via an intramolecular synergistic effect to convert carbohydrates to MLA in methanol. The versatile properties of the resultant catalyst were revealed to be responsible for the conversion of fructose to MLA and the efficient suppression of undesired side reactions. This catalyst displayed outstanding catalytic activity, high selectivity, and excellent recyclability, giving an MLA yield of up to 68.9 % at 160 8C after 2 h. The results of this study will contribute to new approaches for designing synergistic catalysts for producing liquid fuels and chemicals from biomass resources.

Heterogeneous Catalytic Synthesis of Methyl Lactate and Lactic Acid from Sugars and Their Derivatives

“…Complete conversion of fructose was obtained after 2 h at 160 °C under 20 bar in its transformations over Sn(salen)/IL catalyst, when varying the initial fructose concentration from 0.04 to 0.18 mol L −1 . The yield of ML was the highest using 0.11 mol L −1 initial fructose concentration, that is, increasing from 55 % yield to 68 % in the concentration range 0.04 mol L −1 to 0.11 mol L −1 decreasing thereafter to 60 % …”

“…On the other hand, in fructose transformations complete conversion was obtained in 2 h. At the same time, the yield of ML increased with increasing NiOOH catalyst amounts in fructose transformations to ML at 200 °C, while an optimum catalyst loading was observed in this reaction over Sn(salen)/IL at 160 °C. For higher catalyst amounts the yield of ML even decreased . In their case the sum of the product yields decreased.…”

“…In their case the sum of the product yields decreased. It should be stated here that kinetics for fructose transformation was not studied with different catalyst masses and thus a comprehensive kinetic analysis based on the available data is not possible.…”

“…The conversion decreased over 1MgSn‐Beta catalyst in five consecutive experiments from 78 % to 76 % at 120 °C, while only less than 3 % of Sn and Mg were leached . Sn(salen)/IL catalyst was successfully recycled giving the same ML yield in glucose transformations, when the catalyst was washed with ethyl acetate between experiments . Noteworthy is that only washing the spent Fe 2 O 3 /SnO 2 catalyst with methanol and drying at 100 °C facilitated its successful reuse in glucose transformations …”

“…Biomass transformation to value‐added products has been under intensive research efforts in the recent years [1–36] . The target in biorefinery has been to transfer highly abundant biomass to chemicals and fuels [37,38] .…”