Continuous gas phase catalytic transformation of levulinic acid to γ‐valerolactone over supported Au catalysts

Abstract

BACKGROUND: -Valerolactone (GVL) is a high value chemical obtained from hydrogenation of bio-derived levulinic acid (LA). Work to date has focused on batch pressurised catalytic systems where high GVL yield is challenging. In this work, the role of support redox and acidity properties is examined in the continuous gas phase hydrogenation of aqueous LA at ambient pressure over gold on Al 2 O 3 , CeO 2 and TiO 2 ; Pd/Al 2 O 3 served as a benchmark in catalyst tests. RESULTS: 100% GVL yield was achieved under stoichiometric conditions (inlet H2 /LA = 1) over supported Au (mean size = 3.0-4.3 nm). Greater catalytic activity was recorded for Au on reducible TiO 2 and CeO 2 . Under the same reaction conditions, Pd/Al 2 O 3 delivered higher LA consumption rates but promoted formation of pentanoic acid. CONCLUSIONS: GVL formation proceeds via 4-hydroxypentanoic as reactive intermediate. Surface oxygen vacancies (confirmed by O 2 titration) formed during temperature programmed reduction of reducible oxides activate LA for reaction. Greater GVL productivity (with full hydrogen utilisation) is demonstrated in this work relative to state-of-the art supported Pd and Ru catalysts. EXPERIMENTAL Catalyst preparation and activationThe oxide carriers ( -Al 2 O 3 (Puralox, Condea Vista Co.), CeO 2 (Grace Davison) and TiO 2 (P25, Degussa)) were used as received. Supported (1.0-3.0% wt.) Au catalysts were prepared by deposition-precipitation. Urea (100-fold excess, Riedel-de Haën, 99%), used as basification agent, was added to an aqueous solution of HAuCl 4 (4 × 10 −5 -5 × 10 −3 M; 20-50 cm 3 , Sigma-Aldrich,99%) containing the support (5-30 g). The wileyonlinelibrary.com/jctb

Sulfated TiO2 nanosheets catalyzing conversion of biomass derivatives: influences of the sulfation on distribution of Brønsted and Lewis acidic sites

“…The production of levulinic acid (LA) from biomass or derivatives of biomass has also attracted increasing attention, as LA is a raw material for the production of pharmaceutical intermediates or additives in the cosmetic and fuel sectors . Besides, LA is also a platform chemical for the production of other value‐added chemicals, including levulinic esters, γ ‐valerolactone, 1,4‐pentanediol, etc.…”

The hydrogenation of levulinic acid to γ-valerolactone over Cu–ZrO2 catalysts prepared by a pH-gradient methodology

“…As such, Ru-based catalysts are generally accepted as benchmark catalysts for this reaction, and typically comprise of Ru metal loadings between 0.5 and 2 wt% [16][17][18] . Other noble metals have also been studied, such as palladium [19,20] , gold [21] and platinum [22] . However, due to the relatively high costs associated with noble metals, the application of such elements on an industrial scale is somewhat limiting.…”

Hydrogenation of methyl levulinate to γ‐valerolactone over Cu─Mg oxide using MeOH as in situ hydrogen source

“…Molecular H 2 is the most common hydrogen source for the hydrogenation of biomass-derived LA and its esters. [24][25][26][27][28][29][30] Recently, the application of alcohols as the solvent and H-donor for the transfer hydrogenation of levulinate esters through Meerwein-Ponndorf-Verley (MPV) reduction has gained increasing attention. [31][32][33][34][35] It is highly desirable to employ MeOH as the H-donor from the perspective of economy, because…”