Catalytic upgrading of α-angelica lactone to levulinic acid esters under mild conditions over heterogeneous catalysts

Abstract

Butyl levulinate was prepared starting from α-angelica lactone and butanol over Amberlyst® 36. Different reaction conditions were optimized, which resulted in full conversion and 94% selectivity toward the ester at 75 °C. A reaction network analysis reveals pseudo-butyl levulinate and levulinic acid as intermediates in the preparation of butyl levulinate. The mild protocol was successfully applied for different alcohols and compared with the esterification of levulinic acid. Overall, this study identifies α-angelica lactone as a better candidate than levulinic acid for the heterogeneously catalysed preparation of levulinic acid esters. A catalyst screening shows that also zeolites and zirconia-based catalysts are able to catalyse the reaction. However, the transformation of the intermediate pseudo-butyl levulinate into butyl levulinate requires acid sites of sufficient strength to proceed

Synthesis of Butyl Levulinate Based on α‐Angelica Lactone in the Presence of Easily Separable Heteropoly Acid Catalysts

“…Only scarce data on the interaction of alpha-AL with alcohols is currentlya vailable. [22] The here reported yield of BL of approximately 80 %i ss omewhat lower,a lthough the reaction rate over Ch 2 H 4 P 2 W 18 O 62 conformst ot he previously published results. According to Manzer,D abco as ab ase catalysta fforded 58 %y ield of BL only.…”

“…Ab lank reaction withouta ny catalystw as also performed ( Figure 1). Analysis of the reaction mixture showed the presence of p-BL along [22] P-BL represents an intermediate of reaction pathway 1. Under the same conditions, the alpha-AL conversion was very lowo ver ChCl (13 %) as well as in the absence of any catalyst( 5%).…”

“…[2c, 18b] Consequently,L AEs are formed in lowc oncentration in alcohols used as substrate and solvent, thus causing additional costs for product separation. [22] They also uncovered pseudo-LAEs (p-LAEs) as intermediates, which can be further transformed to LAEs over acidic sites of sufficient strength.H owever,a ll reported protocols were implemented under anhydrous conditions (e.g.,u nder inert gas atmosphere)a saspecial precaution to prevent rehydration of alpha-AL to LA. Alpha-AL is readily available by dehydrationo f LA.…”

“…In this regard, synthesis of LAEs by an equimolar addition reactiono fa na lcohol with a-angelica lactone (alpha-AL) minimizes extensive separation procedures. [21,22] Herein, we report choline-exchangedD awson-type heteropoly acids [Ch x H (6Àx) P 2 W 18 O 62 ,i nw hich Ch refers to the choline cation HOCH 2 CH 2 N(Me) 3 + ]a sr ecyclable catalysts for the reaction of butanol with alpha-AL. [20] Manzer reported the production of LAEs based on alpha-AL at elevated temperatures of 100-150 8Co vers olid acids.…”

MFI Acid Catalysts with Different Crystal Sizes and Porosity for the Conversion of Furanic Compounds in Alcohol Media

“…In 2005, DuPont claimed the conversion of α‐angelica lactone (AnL) into LEs by using solid acid catalysts, with emphasis put on commercial acid ion‐exchange resin organocatalysts. These catalytic systems were recently revisited by Palkovits and co‐workers, who reported insightful mechanistic studies. Ion‐exchange resins can be highly active solid catalysts, but their limited chemical/thermal stabilities can be critical for applications in biomass conversion processes, because the solid catalysts are typically fouled by humins formed from feed components/reaction intermediates and the catalyst recovery generally involves thermal treatments …”