Ru catalysts for levulinic acid hydrogenation with formic acid as a hydrogen source

Abstract

International audienceThe catalytic hydrogenation of levulinic acid (LA) with formic acid (FA) as a hydrogen source into [gamma]-valerolactone (GVL) is considered as one of the crucial sustainable processes in today's biorefinery schemes. In the current work, we investigated the modification of Ru/C as efficient catalysts for both formic acid decomposition and levulinic acid hydrogenation in comparison with Pd and Pt catalysts. In order to better understand what features are responsible for high catalytic performance, we combined experimental tests, DFT calculations together with extensive material characterization. In LA hydrogenation with FA as a hydrogen source, the intermediate surface formate inhibits at least partially the LA hydrogenation. In addition, the FA decomposition is highly sensitive to the kind of the preparation method of the Ru/C catalyst: (i) the process looks structure sensitive favored on larger particles and (ii) residual chlorine decreases significantly the FA decomposition rate

Interfacial acidity in ligand-modified ruthenium nanoparticles boosts the hydrogenation of levulinic acid to gamma-valerolactone

“…Notwithstanding the determination of the atomic state of Ru-based materials is not straightforward for carbon supported material, due to the overlapping of the Ru 3d core level signal with C 1s one, a feature centred at 281.3 eV indicative of the presence of RuO x species for the Ru/C sample was observed. 58 In the case of the Ru-HHDMA/TiSi 2 O 6 , a single Ru 3d 5/2 core level at 280.2 eV was displayed (Figure 6), confirming that the ruthenium surface is fully metallic. 58,59 An additional tool to further prove the oxidation state of the Ru catalysts is H 2 -TPR ( Figure S2).…”

“…58 In the case of the Ru-HHDMA/TiSi 2 O 6 , a single Ru 3d 5/2 core level at 280.2 eV was displayed (Figure 6), confirming that the ruthenium surface is fully metallic. 58,59 An additional tool to further prove the oxidation state of the Ru catalysts is H 2 -TPR ( Figure S2). Apart from the decreased signal intensity observed at room temperature due to the stabilisation of the MS filament, Ru-HHDMA/TiSi 2 O 6 did not show any hydrogen consumption peak around 400 K, the expected temperature of reduction of RuO x species to Ru 0 .…”

A Multiphase Protocol for Selective Hydrogenation and Reductive Amination of Levulinic Acid with Integrated Catalyst Recovery

“…[27] Because FA can be catalytically decomposed to CO 2 and H 2 over Ru/C, [28] it may act as an in situ transfer-hydrogenation agent. [30] This behavior was confirmed by the resultso btained in the IL-free MP system. [29] However,l imitations exist owing to the high temperature (!…”

“…[32] Unfortunately,i nitial tests showedt hat the catalyst remained partitioned between the two immiscible phases of the system, and most importantly,the major reaction was the competitive hydrogenation of LA to GVL and not the desired formation of 1-cyclohexyl-5-methylpyrrolidin-2-one (CyMP). [29,30] Further screening studies were therefore performed with an equimolar mixture of LA and FA (3.6 mmole ach), by adjusting the quantity of CyNH 2 (3.6-7.2 mmol) and water (0.5-5 mL), and by varying T and p (130 and 150 8C, and 15 and 35 bar H 2 ). [31,33,35,38] To disfavort he formation of GVL during the MP process, we envisaged adding FA,w hich is known to selectively inhibit the adsorption of LA on Ru/C (see the previous section).…”

Ru/ZrO2 Catalysts for Transfer Hydrogenation of Levulinic Acid with Formic Acid/Formate Mixtures: Importance of Support Stability

“…Further increasing the ratio from 1 to 2, however, led to a significant drop in the conversion from 73% to 32%, confirming that the hydrogen source competes with levulinic acid for active sites on the catalyst. This is supported by DFT calculations showing that the relative adsorption energy of formic acid on Ru is higher than levulinic acid . Hence, the optimum hydrogen source: levulinic acid ratio is 1 : 1, which is the ratio at which levulinic acid and formic acid are formed in the hydrolysis of carbohydrates.…”