Integrated Conversion of Hemicellulose and Furfural into γ-Valerolactone over Au/ZrO₂ Catalyst Combined with ZSM-5

Abstract

The high-yield synthesis of the biofuel γ-valerolactone (GVL) is a challenging task, which currently stems from the depolymerization of cellulose to levulinic acid, followed by its hydrogenation. We have developed a novel integrated process for the production of GVL from hemicellulose without using liquid acids and external hydrogen. The hemicellulose feed underwent hydrolysis and consecutive dehydration to produce furfural over ZSM-5 catalyst. Subsequently, the formed furfural with 2-propanol performed tandem conversion to GVL over Au/ZrO 2 catalyst combined with ZSM-5. This process gave a high yield of GVL under mild conditions: up to 61.5% based on hemicellulose. The outstanding performance was mainly ascribed to the strong interface interaction of Au with ZrO 2 species, large amounts of medium-strength acid sites over ZSM-5, and efficient synergy between active metal and acid sites.

The Promoting Effect of Ce on the Performance of Au/CexZr1−xO2 for γ-Valerolactone Production from Biomass-Based Levulinic Acid and Formic Acid

“…According to the proposed reaction pathway (Scheme 1), it can be known that higher acid amount can significantly promote the molecular dehydration reaction of LA hydrogenation products, thereby further improving the yield of GVL. This is well in line with the result in literature that medium-strength acid is important for LA conversion to GVL [12,28]. Weckhuysen et al points out that the presence of a strong acid could lead to the hydrogenation of LA, passing through the formation of 4-hydroxypentanoic acid (HPA) and pentanoic acid [34].…”

“…However, from both the economic and engineering point of view, this process will arguably be less sustainable, as the worldwide H 2 is produced mainly by the steam reforming of fossil carbon [7][8][9]. Alcohols, such as ethanol, isopropyl alcohol and butanol, are also employed as the hydrogen source in the process of catalytic transfer hydrogenation (CTH) [10][11][12]. Formic acid (FA) is another potential hydrogen source for GVL synthesis, as it shows higher energy density and is easier to be stored and transferred.…”

Production of γ‐Valerolactone from One‐Pot Transformation of Biomass‐Derived Carbohydrates Over Chitosan‐Supported Ruthenium Catalyst Combined with Zeolite ZSM‐5

“…For economic and cost‐saving purpose, it is more desirable to produce GVL from one‐pot conversion of the abundant biomass‐derived C5 carbohydrates such as furfural, xylose and hemicellulose. However, only a handful of catalyst systems have been developed to accomplish this goal so far . Such as Román‐Leshkov and co‐workers achieved a 78 % yield of GVL from the domino reaction catalyzed by zeolites with both Brønsted and Lewis acid catalyst sites in 2013 .…”

“…Later, bifunctional Zr‐Al‐Beta zeolite prepared through a post‐synthetic route obtained GVL in 22.6 % or 34 % yield from one‐pot conversion of FF or xylose in 2‐propanol, respectively . The combination of Au/ZrO 2 and ZSM‐5 could achieve an 80.4 % yield of GVL from one‐pot conversion of FF . In 2018, hafnium‐based metal‐organic frameworks was combined with Brønsted‐acidic Al‐beta zeolite to furnish a 75 % yield of GVL from one‐pot conversion of FF .…”

Alcoholysis: A Promising Technology for Conversion of Lignocellulose and Platform Chemicals

“…More importantly, this approach showed extensive substrate scope and led to the synthesis of a series of AL species with various functional groups. In addition, the hybrid catalysts Au/ZrO 2 and Al 3+ ‐exchanged HPW salt (AlPW) combined to afford AL in good yields (up to 78.7 %) by integrated conversion of furfural with 2‐propanol (Table , entry 19) . The alcoholic medium evidently plays a key role in this process, which cannot be smoothly realized in water.…”