Levulinic Acid Upgrading

Levuhnic acid is one of the products of selective dehydration of cellulosic biomass feedstocks. Levuhnic acid is produced when six-member ring carbohydrates derived from ceUulose are subjected to acid-catalyzed dehydration conditions (Fig. 9.6) [4, 43]. The other main product of this reaction is formic acid. Although levulinic acid has some potential use as a solvent or in the production of industrial and pharmaceutical chemicals, its current market is minimal [4]. Therefore, the conversion of levulinic acid to a directly usable biofuel has become an important area of interest. In particular, esterification, oxidation, hydrogenation, reductive amination, condensation, and enzymatic conversion have been tested as potential methods to produce useful compounds from levulinic acid [4,44,45]. 

Of these levulinic acid conversion reactions, catalytic hydrogenation to form y-valerolactone (GVL) has been reported as a promising route. GVL is interesting due to its potential direct application as a biofuel [43,46]. The physical and chemical properties of GVL are very attractive for storage, transportation, and direct use in conventional 

The conversion of levuUnic acid to GVL using various catalysts supported on carbon (iridium, rhodium, palladium, ruthenium, platinum, rhenium, and nickel at 5 wt % on carbon) has been reported [48]. Although high conversions of levulinic acid are seen with these catalysts, the only catalyst with a high selectivity to GVL is Ru/C. The selectivities decrease in the following order at 150°C and 800 psig for 2h  

A GVL selectivity of greater than 97% is observed when the reaction conditions are changed to 500 psig for 4h of reaction time. Also, this catalyst can be recycled multiple times without noticeable deactivation. 

In a subsequent report, the Ru precatalyst was immobilized on three different inorganic/organic hybrid sihca supports (1) amine-functionalized (Ru-N/SiO ), (2) phosphine functionalized (Ru-P/SiOj), and (3) thiol functionalized (Ru-S/SiO ) [50]. For levulinic acid hydrogenation to GVL, the performance of the catalysts decreases in the order of Ru-P/SiO Ru-S/SiO Ru-N/SiO. When compared to a Ru/C catalyst, the Ru/C exhibits a much higher turnover frequency (10 times greater than Ru-P/SiOj) but has an extremely low yield ( 7% after 12h). This is attributed to the poor selectivity of Ru/C to decompose formic acid to and CO. Furthermore, the Ru-P/SiOj catalyst was used in eight consecutive experiments without noticeable loss of selectivity or yield of GVL [50], 

---

Serrano-Ruiz JC, Wang D, Dumesic JA (2010) Catalytic upgrading of levulinic acid to 5-nonanone. Green Chem 12 574-577... 

Dumesic and collaborators developed a process for the catalytic upgrading of levulinic acid to 5-nonanone, with the intermediate formation of y-valerolactone (Fig. 13.3). Levulinic acid can be obtained inexpensively and in high yields via acid hydrolysis of waste cellulosic materials. The process starts with the deconstruction of solid cellulose in an aqueous solution of sulfuric acid yielding an equimolar mixture of levulinic acid and formic acid. The formic... 

Ding, D., Wang, J., Xi, J., Liu, X., Lu, G., Wang, Y., 2014. High-yield production of levulinic acid from cellulose and its upgrading to yvalerolactone. Green Chemistry 16, 3846-3853. 

Nandiwale, K.Y., Sonar, S.K., Niphadkar, P.S., Joshi, P.N., Deshpande, S.S., Patil, V.S., Bokade, V.V., 2013. Catalytic upgrading of renewable levulinic acid to ethyl levuhnate biodiesel using dodecatungstophosphoric acid supported on desilicated H-ZSM-5 as catalyst. Applied Catalysis A General 460—461, 90—98. 

Pasquale, G., Vazquez, P., Romanelli, G., Baronetti, G., 2012. Catalytic upgrading of levulinic acid to ethyl levuhnate using reusable silica-included WeUs-Dawson heteropolyacid as catalyst. Catalysis Communications 18, 115—120. 

Intrinsic energy of FA can also be upgraded by means of etherification with short-chain alcohols, transformation of alkyl-furfuryl ethers into alkyl levulinates and esterification with short alkyl carboxylic acids. In the following, we wiU discuss the most... 

---