Catalytic and mechanistic insights into the production of ethyl levulinate from biorenewable feedstocks

Abstract

The importance of ethyl levulinate (EL) as a fuel additive and a potential biomassderived platform molecule is noteworthy. EL is obtained from the esterification of levulinic acid (LA) in presence of ethanol. Besides LA, the acid-catalyzed ethanolysis reaction to produce EL is carried out on a variety of biomass-derived substrates which include; furfuryl alcohol (FAL), chloromethyl furfural, monosaccharides, polysaccharides and lignocellulosic biomass. The acid catalysts employed for such conversions covers a wide range of structure and properties. The nature of acid catalysts and the key intermediates formed during the reaction dictates the overall yield of the desired product. For example, in the ethanolysis reaction of FAL to produce EL, diethyl ether (DEE) and ethoxymethylfuran (EMF) produced as side products are suggested to influence the selectivity of EL. Similarly, in the ethanolysis of glucose, formation of ethyl-Dglucopyranoside (EDGP) resulted into a slow conversion to produce EL. The review, therefore; is focused on highlighting the importance of catalyst structure, acidity, reaction mechanism and the role of key intermediates in the production of EL from biorenewable resources.EL could either be synthesized directly from biomass or via the transformation of LA, or FAL 20 or chloromethyl furfural (CMF) 23 . All of the suggested reaction routes essentially contain an ethanolysis step in the presence of an acid catalyst. In general, an understanding of the mechanistic routes of product formation, dictates the development of a suitable process for achieving higher yield 24,25 . This could be further strengthened by the design of a suitable homogeneous acid, solid acid or ionic liquid based acid catalysts. On catalytic processing, EL could be converted into an array of higher value chemicals. This review comprehensively covers all the suggested ways of EL production and applications detailing key mechanistic insights, catalytic properties and reaction conditions. Importance of EL as a Fuel AdditiveAlkyl levulinates have shown considerable promises for blending in gasoline and diesel engines, owing to their reduced sulfur content, high lubricity, improved flow properties and flash point stability 20 . The candidate LA esters for this application are methyl, ethyl 26 and butyl levulinates, 23 measuring anti-knocking index of value 106.5, 107.5 and 102.5 respectively 27 . Out of three levulinates, methyl levulinate (ML) is miscible with water and is difficult to separate. With gasoline, ML is lesser miscible and under cold flow conditions is not suitable to blend.Compared to butyl levulinate (BL), EL shows better solubility with diesel range fuels containing higher aromatics 14 . Moreover, NOx emissions were lowered by about 4% on EL blend in diesel as compared to the BL blend. Higher NOx emissions could be attributed to the dilution of lube oil and deposits in combustion chamber, which was observed to be a major problem with BL blended fuels. Furthermore, when propanol or higher alcohols are used for the...

Insights into the Metal Salt Catalyzed 5-Ethoxymethylfurfural Synthesis from Carbohydrates

“…A variety of substances were detected after the reaction, namely glucose, fructose, ethyl glucoside (EGO), ethyl fructoside (EFO), HMF, EMF, and ethyl levulinate (EL). Factually, ethyl formate can also be generated along with EL in a serial mode from the reaction of the furan derivatives and ethanol [26][27][28]. However, ethyl formate was not observed in our tests, probably due to no separation of ethyl formate and solvent ethanol for the equipped GC instrument.…”

Catalytic Upgrading of Biomass-Derived Furfuryl Alcohol to Butyl Levulinate Biofuel over Common Metal Salts

“…In recent years, research on the transformation of furfuryl alcohol to levulinate esters has been reported at an increasing rate [13][14][15]. Acid catalyst is identified as the key point for the synthesis of levulinate esters, and is thus the focus of the study.…”

Advanced Biofuels and Beyond: Chemistry Solutions for Propulsion and Production

“…[57] Thep athways to such tailor-made biofuels or related valueadded chemicals [248][249][250][251][252] must satisfy the principles of "Green Chemistry" [253] to address the criteria of sustainability on the basis of the feedstock as well as in the production process. [254][255][256] In this context, the selective conversion of the raw materials into the desired products,while largely maintaining the synthetic effort of nature,a ppears to be an attractive approach.…”