Base‐Catalyzed Condensation of Levulinic Acid: A New Biorefinery Upgrading Approach

Abstract

The base-catalyzedc ondensation of levulinic acid (LA) under mild conditions (0.1 MPa, 323 K, 0.45 mol L À1 aq solution of levulinic acid, catalyst/reactant = 1:24 wt.)w as proposed as an ew approachf or the upgrading of this molecule by using mixed oxides as catalysts. Three products were identified: a-angelica lactone (AL) and two aldol condensation adducts,L A-LA and AL-LA. These last ones (obtainedw ith selectivities higher than 90 %a t3 0% conversion upon using MgZr)p resenth igh value as fuel and chemical precursors. The distribution of basic and acidic sites on the catalyst governs the performance and selectivity of the catalyst, whereas the stability of the catalyst in the reactionm edia determines the deactivation behavior.B ulk MgZr oxidespresent agood balance of these properties.Transformation of biomass into highly valuable products and liquid fuels has received much attention in the last years. Levulinic acid (4-oxopentanoic acid, LA) is nowadays considered one of the most promisingb ioplatformm olecules. This keto acid is obtained in significant yields (> 80 %) by the aqueousphase hydrolysis of cellulosic feedstock if the hydrolytic conditions are acidic enough to yield levulinic acid and formic acid by fragmentation of dehydrated sugars.[1] These conditions are industrially implemented by the BIOFINE process.[2] LA has been proposed asareactant in different processesf or the productiono fa dvanced biofuels, monomers, as well as other molecules with industriali nterest.[3] Most of these processes involve the transformation of levulinic acid into g-valerolactone. [4,5] However,t his reactionr equires the presence of molecular hydrogen and severe conditions (473 Ka nd 3MPa), which hinder both energy trade-off and process sustainability.C onsequently,d ifferent improvements, such as using formic acida s the hydrogen source,h ave been explored.[6] Other acid-catalyzed reactions are proposed, including esterification with different alcohols catalyzedb yh omogeneous acids such as HCl, H 2 SO 4 ,a nd H 3 PO 4 [7] or basic salts such as K 2 CO 3 at temperatures over 450 K, [8] not fulfilling the "green chemistry" principles.Most of these previously studied reactions are focused on the reactivity of the carboxyl group of the levulinic acid;r eferences dealing with the reactivity of the carbonyl group are very scarce. In this framework, aldol condensation is one of the most common reactions involving this functional group.T his reactioni ncreases the length of the carbon chain by ab asecatalyzed mechanism that beginsw ith abstraction of ap roton a to the carbonyl functional group. This reaction has already been proposed to upgrade bioplatform molecules,s uch as acetone, 5-hydroxymethylfurfural, and furfural.[9-12] Although acetones elf-condensation is often studied in the gas phase, [9,13] most aldol condensations are performed in the aqueous phase, at low pressure, and mild temperatures, [10][11][12] and it leads to sustainable and environmentally benignb iorefinery processes. Despitet he fact that the fir...

Angelica Lactones: From Biomass‐Derived Platform Chemicals to Value‐Added Products

“…The Ordóñez group has also disclosed findings on this subject, and in their work they study the self‐condensation of LA and its condensation with AL with the aim to produce compounds with 10 carbon atoms that might be used as fuel precursors (Scheme ) . The authors identify three distinct products under the studied conditions, which include conducting the reaction at 50 °C in water by using MgZr or MgAl mixed oxides as catalysts and levulinic acid as the starting material: one, α‐AL; two, the product resulting from the condensation of α‐AL with LA (AL‐LA); three, the self‐condensation product of LA (2LA), as shown in Scheme .…”

“…ChemSusChem 2018, 11,25-47 www.chemsuschem.org cursors (Scheme 15). [37] The authorsi dentify three distinct products under the studied conditions, which include conducting the reactiona t5 0 8Ci nw ater by using MgZr or MgAl mixed oxidesa sc atalystsa nd levulinic acid as the startingm aterial:o ne, a-AL;t wo, the product resulting from the condensation of a-AL with LA (AL-LA);t hree, the self-condensation product of LA( 2LA), as shown in Scheme 15. The presence of the AL-LA product can be explained by considering enolization of the a-AL adduct followed by its reaction with the carbonyl group of the levulinate anion.H owever,t he formation of AL-LA involves ap rimary reaction product (a-AL), and therefore, its yield is significantly lower than that for the 2LA adduct (the highest selectivity to the former compound is 12.7 %).…”

Transformation of Levulinic Acid to Valeric Biofuels: A Review on Heterogeneous Bifunctional Catalytic Systems

“…In addition, alkaline‐catalyzed aldol condensation of LA is considered to be another way to achieve biomass upgrading; carbon loss and byproducts can be effectively suppressed by condensation processes . Two condensation adducts, LA dimer and LA‐α‐angelica lactone adduct, could be obtained through aqueous LA aldol condensation reactions under the catalysis of MgZr oxides . 5‐Hydroxymethylfurfural (5‐HMF) and furfural (Fur) are also able to undergo condensation reactions with LA under alkaline catalytic conditions and generate the corresponding aldol adducts, which could be used as potential precursors for value‐added polymers and renewable fuels …”

Hydrodeoxygenation of Levulinic Acid Dimers on a Zirconia-Supported Ruthenium Catalyst

“…The structure and production of LA dimers through aldol condensation was first described by Blessing and Petrus [18]. Recently, the production of LA dimers has been described by several authors using hydrogenating conditions with a Pd containing ion-exchange resin as a catalyst, basic MgZr oxide catalysts in water, or ZnCl2 catalyst in trichloroacetic acid [7,[19][20][21]. The formation of LA dimers in hydrogenating conditions and the mixture of identified LA dimers in the feed used in this work are presented in Scheme 1.…”

“…The formation of LA dimers in hydrogenating conditions and the mixture of identified LA dimers in the feed used in this work are presented in Scheme 1. The LA dimers have potential applications, upon further processing, as fuel additives, surfactants, plasticizers, hydraulic fluids, and lubricants [19,20,22]. Scheme 1.…”