The Role of the Hydrogen Source on the Selective Production of γ‐Valerolactone and 2‐Methyltetrahydrofuran from Levulinic Acid

Abstract

A mechanistic study of the hydrogenation reaction of levulinic acid (LA) to 2-methyltetrahydrofuyran (MTHF) was performed using three different solvents under reactive H2 and inert N2 atmospheres. Under the applied reaction conditions, catalytic transfer hydrogenation and hydrogenation with molecular H2 were effective at producing high yields of γ-valerolactone. However, the conversion of this stable intermediate to MTHF required the combination of both hydrogen sources (the solvent and the H2 atmosphere) to achieve good yields. The reaction system with 2-propanol as solvent and Ni-Cu/Al2 O3 as catalyst allowed full conversion of LA and a MTHF yield of 80 % after 20 h reaction time at 250 °C and 40 bar of H2 (at room temperature). The system showed the same catalytic activity at LA feed concentrations of 5 and up to 30 wt%, and also when high acetone concentration at the beginning of the reaction were added, which confirmed the potential industrial applications of this solvent/catalyst system.

Cascade Strategy for the Tunable Catalytic Valorization of Levulinic Acid and γ-Valerolactone to 2-Methyltetrahydrofuran and Alcohols

“…Regarding the related reaction mechanism, under solvent-free conditions, 2-BuOH is predominantly formed via subsequent hydrogenation/decarbonylation reactions of the GVL [42], as shown in Scheme 3. Obregón et al [45] reported the GVL hydrogenation, achieving a maximum 2-BuOH yield of 37.3 mol %, working in 2-PrOH, at 250 °C and 4 MPa H2. Lastly, Lv et al [54] have recently used nanoporous Ru for LA hydrogenation in water, reporting the combined production of both 2-BuOH and 2-Pentanol (2-PeOH), the latter derived mainly from 1,4-PDO hydrogenation, with a total [2-BuOH + 2-PeOH] yield of 78.8 mol %, working at 140 °C for 20 h, with 6 MPa H2.…”

“…Concerning the other possible route, the presence of 2-MeTHF was reported for the first time as a by-product of the LA hydrogenation with CuCr 2 O 3 [35]. Afterward, many works have been published on this topic, which have partially clarified the reaction mechanism, and significantly improved the catalytic performances for the synthesis of 2-MeTHF [36][37][38][39][40][41][42][43][44][45]. Two reaction mechanisms have been proposed for 2-MeTHF synthesis from LA, the first one occurring by LA dehydration via angelicalactone (AGL) (path A, Scheme 1), whereas the second one by LA hydrogenation to 4-hydroxypentanoic acid (HPA) (path B, Scheme 1), both reported in Scheme 1.…”

“…The reaction proceeds by LA reduction to HPA, which readily dehydrates to GVL. The hydrogenation of GVL into 1,4-pentanediol (1,4-PDO) is reported to be strongly inhibited by water [42], thus highlighting evident difficulties to perform this reaction in water already at this backward step and, even with greater difficulty, for the final 1,4-PDO dehydration to 2-MeTHF [45]. Main by-products of this reaction include pentanoic acid and 1-pentanol.…”

xNi–yCu–ZrO2 catalysts for the hydrogenation of levulinic acid to gamma valorlactone

“…The authors concluded that there was a synergistic effect between Ni and Cu in the mixed NiCu particles leading to an improved yield of 2-MTHF. A recent study by Palkovits and co-workers [27] discussed the mechanism of the hydrogenation of LA to GVL and 2-MTHF using Cu-Ni/Al 2 O 3 catalyst under hydrogenation and transfer hydrogenation conditions. They have reported that Cu-Ni/Al 2 O 3 catalysts are more active than Ru/C using a solvent that is a poor hydrogen donor, and that a 93% yield of GVL can be obtained.…”

Sustainable Carbon Sources and Renewable Energy: Challenges and Opportunities at the Interface of Catalysis and Reaction Engineering

“…Further studies confirmed a significant effect of the solvent system. Under the applied reaction conditions, catalytic transfer hydrogenation and hydrogenation with molecular H 2 occurred and their combination was necessary to achieve 80 % 2‐methyltetrahydrofuran yield with 2‐propanol as solvent and 40 bar of H 2 (at room temperature) . Also, the transformation of platform chemicals such as sorbitol and xylitol via selective C – C and C – O cleavage into ethylene and propylene glycol could be established (Fig.…”