Role of water in metal catalyst performance for ketone hydrogenation: a joint experimental and theoretical study on levulinic acid conversion into gamma-valerolactone

Microkinetic analysis of acetone hydrogenation over Pt/SiO2

Catalytic hydrogenation of a biomass-derived molecule, levulinic acid (LA), to γ-valerolactone (GVL) has been getting much attention from researchers across the globe recently. This is because GVL has been identified as one of the potential molecules for replacing fossil fuels. For instance, GVL can be catalytically converted into liquid alkenes in the molecular weight range close to that found in transportation fuels via a process that does not require an external hydrogen source. Noble and non-noble metals have been used as catalysts for the selective hydrogenation of LA to GVL. Of these, Ru has been reported to be the most active metal for this reaction. The type of metal supports and solvents has been proved to affect the activity, selectivity, and yields of GVL. Water has been identified as a potential, effective “green” solvent for the hydrogenation of LA to GVL. The use of different sources of H2 other than molecular hydrogen (such as formic acid) has also been explored. In a few instances, the product, GVL, is hydrogenated further to other useful products such as 1,4-pentanediol (PD) and methyl tetrahydrofuran (MTHF). This review selectively focuses on the potential of immobilized Ru catalysts as a potential superior catalyst for selective hydrogenation of LA to GVL.

Heterogeneous Ru Catalysts as the Emerging Potential Superior Catalysts in the Selective Hydrogenation of Bio-Derived Levulinic Acid to γ-Valerolactone: Effect of Particle Size, Solvent, and Support on Activity, Stability, and Selectivity

The gas phase hydrogenation of levulinic acid to γ-valerolactone over copper and ruthenium based catalysts in a continuous fixed-bed reactor system was investigated. Among the catalysts a copper oxide based one [50–75 % CuO, 20–25 % SiO2, 1–5 % graphite, 0.1–1 % CuCO3/Cu(OH)2] gave γ-valerolactone in 93 % yield for more than 90 h constant operation.

Gas Phase Hydrogenation of Levulinic Acid to gamma-Valerolactone

The hydrodeoxygenation (HDO) of levulinic acid (LA) aldol condensation product dimers was studied between 250 and 300 °C and 50 bar H2 in a batch reactor with Ru catalyst supported on mesoporous zirconia. During the reaction, the unsaturated dimers, which contained ketone groups and double bonds, were hydrogenated to saturated dimers. A greater degree of deoxygenation was achieved at higher temperatures, and oxygen was removed as water and CO2. Oxygen removal was evidenced by elemental analysis and infrared spectroscopy, in which the C=O peak decreased with increasing temperature. A drawback of high reaction temperature (300 °C) was a minor degree of oligomerization. The formation of aromatics was also observed at the higher temperatures. Aside from the saturated dimers, volatile products were obtained at all temperatures, including ketones, acids, and esters. This study demonstrates for the first time the potential of LA dimers as a sustainable route from lignocellulosic biomass to biofuels and biocomponents.

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Hydrodeoxygenation of Levulinic Acid Dimers on a Zirconia-Supported Ruthenium Catalyst

The catalytic properties of supported mono- and bimetallic catalysts of the Tc/support, M/support, and M-Tc/support types (M=Pt, Pd, Rh, Ru, Ni, Re, Co; supports are γ-Al2O3, MgO, SiO2) were investigated in the acetone hydrogenation. The main products of this reaction are isopropyl alcohol and propane. The catalytic activity in the acetone hydrogenation of the metals studied decreases in the consequence Pt>Tc≈Rh>Pd>Ru >Ni≈Re>Co (with γ-Al2O3 as the support). The influence of support nature on the catalytic activity was investigated for the Rh−Tc system as an example. A nonadditive increase in the catalytic activity of Rh−Tc/γ-Al2O3 in comparison with monometallic catalysts was found. The state of the surface of the catalysts was characterized by the UV-VIS diffuse reflectance spectra.

Hydrogenation of acetone on technetium catalysts

The catalytic properties of a Rh-Tc/support (γ-Al2O3, SiO2, or MgO) system in the dehydrogenation of cyclohexane have been investigated. A nonadditive increase in the catalytic activity of bimetallic catalysts in comparison with monometallic systems has been established. This effect depends on the ratio of the amounts of the supported metals and on the nature of the support. Diffuse reflectance spectra showed the presence of ionic forms of the metals in the bimetallic catalysts. Analysis of the catalytic and optical properties allowed one to draw the conclusion that the synergistic effect is explained by the formation of RhxTcy clusters.

Rhodium-technetium catalysts in the dehydrogenation of cyclohexane

Catalytic properties of the Ru-Tc/support (γ-Al2O3, Y2O3, and SiO2) systems in the dehydrogenation of cyclohexane have been studied. The catalytic activity of the bimetallic catalysts depends on the nature of the support. A nonadditive increase in the catalytic activity of the bimetallic catalysts in comparison with monometallic samples was established. The value of the synergistic effect depends on the ratio between the amounts of the supported metals and the nature of the support. By using the diffuse reflectance spectra in UV- and visible regions and hydrogen chemisorption techniques, the modifying influence of the ionic metal species on the catalytic properties was shown.

N. N. Rimar

Papers

Hydrogenation of acetone on technetium catalysts

Rhodium-technetium catalysts in the dehydrogenation of cyclohexane

Synergistic effect for bimetallic ru-tc catalysts of cyclohexane dehydrogenation