Monometallic Ru Catalysts Research Articles

Ruthenium-Cobalt Solid-Solution Alloy Nanoparticles for Enhanced Photopromoted Thermocatalytic CO2 Hydrogenation to Methane.

Bimetallic alloy nanoparticles have garnered substantial attention for diverse catalytic applications owing to their abundant active sites and tunable electronic structures, whereas the synthesis of ultrafine alloy nanoparticles with atomic-level homogeneity for bulk-state immiscible couples remains a formidable challenge. Herein, we present the synthesis of RuxCo1-x solid-solution alloy nanoparticles (ca. 2 nm) across the entire composition range, for highly efficient, durable, and selective CO2 hydrogenation to CH4 under mild conditions. Notably, Ru0.88Co0.12/TiO2 and Ru0.74Co0.26/TiO2 catalysts, with 12 and 26 atom % of Ru being substituted by Co, exhibit enhanced catalytic activity compared with the monometallic Ru/TiO2 counterparts both in dark and under light irradiation. The comprehensive experimental investigations and density functional theory calculations unveil that the electronic state of Ru is subtly modulated owing to the intimate interaction between Ru and Co in the alloy nanoparticles, and this effect results in the decline in the CO2 conversion energy barrier, thus ultimately culminating in an elevated catalytic performance relative to monometallic Ru and Co catalysts. In the photopromoted thermocatalytic process, the photoinduced charge carriers and localized photothermal effect play a pivotal role in facilitating the chemical reaction process, which accounts for the further boosted CO2 methanation performance.

Enhanced ruthenium selectivity for the conversion of FAMEs to diesel-range alkanes by surface decoration of FeOx species

Ruthenium-based catalysts have been widely used in the lignin depolymerization and polystyrene hydrogenolysis reactions due to its superior hydrogenolysis activity for C-O and C-C bonds. However, serious cleavage of C-C bonds at high temperatures greatly limits its application in the production of green biodiesel from the conversion of natural oils and bio-derived fatty esters. In this work, we found that introducing a suitable second less-reactive metal (e.g., Fe, Zn) can effectively suppress the hydrogenolysis activity of ruthenium (Ru) metal for C-C bonds and exhibit a high selectivity (>90 %) to diesel-range alkanes (C15-C18 alkanes) in the conversion of fatty acid methyl esters (FAMEs) even at high reaction temperature (250 °C) over the Ru1Fe0.5 catalyst, while an obvious cracking reaction was observed from 210 °C over the monometallic Ru catalyst. Detailed characterization and theoretical calculation results reveal that the introduction of Fe species in the RuFe catalysts weakens the interaction between catalyst and the resulting alkanes, which inhibits the cracking of alkanes. Specifically, adding Fe species breaks the ensemble of Ru atoms and decreases the binding affinity of metallic Ru for H2, which suppresses the activity of Ru metal for the hydrogenolysis of C-C bonds and exhibits a high selectivity to diesel-range alkanes. This research provides valuable information for improving the hydrodeoxygenation (HDO) selectivity of Ru-based catalysts while inhibiting its high hydrogenolysis activity for C-C bonds.

Aqueous phase selective C[dbnd]O hydrogenation of cinnamaldehyde over bimetallic RuCo catalysts with electronic and geometric modification

Aqueous phase selective hydrogenation of cinnamaldehyde (CALD), as a representative α,β-unsaturated aldehyde, into cinnamyl alcohol (CALA) has been investigated over monometallic Ru and bimetallic RuCo catalysts on pristine h-BN support. Using water as the solvent, the optimal 0.5%Ru-1.1%Co/h-BN catalyst exhibits 510 h−1 specific reaction rate and 78.9 % CALA selectivity as well as good recycling stability at 100 °C. Based on the structure characterizations of catalysts, metal nanoparticles consisting of metallic Ru0 and partially oxidized Ruδ+ sites are uniformly dispersed on h-BN thin sheets. In comparison to monometallic catalysts, additive Co metals in bimetallic RuCo/h-BN catalysts play significant geometric and electronic modification roles on Ru active sites depending on the Ru/Co ratio, and therefore remarkably enhances the preferential activation of CALD CO bond and selectivity of CALA product as well as accelerates the catalytic reaction. Furthermore, the hydrogen dissociative activation ability of various Ru and RuCo catalysts was evaluated, while the superior catalytic performance in water than other commonly used solvents was also clarified and discussed.

Hydrogenolysis of glycerol over ZSM-5 supported ruthenium and copper catalysts: Structural study and effects in reaction

HZSM-5 supported bimetallic Ru-Cu catalysts were investigated with the objective of converting glycerol from biodiesel production into propanediols through the hydrogenolysis reaction. Two zeolites were used as supports, one with a SiO2/Al2O3 molar ratio of 80 and another with a ratio of 23. Physisorption analysis showed high specific area for the solids with values in the range of 400 m2 g−1, that enabled the metals to be incorporated as nanoparticles undetectable by XRD. Monometallic Ru catalysts displayed Ru0 species after reduction and RuO2 species duo to passivation, as evidenced by XPS analysis. Monometallic copper catalysts contained Cu0 and Cu+ species verified by XPS and DRIFTS after reduction and passivation, Cu2+ species were not found. As for the Ru-Cu bimetallic catalysts, Ru was added by impregnation of Cu/HZSM-5 and covered the copper nanoparticles as XPS analysis showed an increase in Ru/Cu molar ratio at the surface for both bimetallic catalysts. The XPS analysis showed increased Ru/Cu ratio at the surface for both bimetallic catalysts (1.95 and 2.94 for Ru-Cu/HZSM-5–80 and Ru-Cu/HZSM-5–23, respectively), furthermore no electronic effects between the two metals were observed indicating that the interaction between Ru and Cu consists in Ru diluting Cu. Chemisorption analysis show increase in CO adsorption for the bimetallic catalysts duo to the joint adsorptive capacity of Ru and Cu+, increasing from 141.4 µmol g−1 to 147.8 µmol g−1 for Ru-Cu/HZSM-5–80, and from 155.2 µmol g−1 to 198.5 µmol g−1 for Ru-Cu/HZSM-5–23, although the species adsorbed are thermally unstable compared to the monometallic adsorption, as shown by DRIFTS analysis. The activity of Ru catalysts was the highest (33 % and 32 % for catalysts supported on ZSM-5–80 and ZSM-5–23, respectively), but there was the formation of degradation products such as ethylene glycol. Copper catalysts showed moderate activity (11 % and 8 % for catalysts supported on ZSM-5–80 and ZSM-5–23, respectively) with good selectivity towards propanediols (22 % and 23 % for 1,2-PDO at isoconversion) duo to Cu0 and Cu+ interaction. Bimetallic catalysts Ru-Cu catalyst showed an improvement in selectivity to propanediols (36 % and 54 %) due to the interaction between Ru and Cu with low activity and reaction’s TOF (0.71 and 0.80 ×10−3 s−1).

Mechanochemical Synthesis of RuCo/MgTiO3 Catalysts for Nonthermal Plasma-Assisted Ammonia Synthesis

The development of robust yet effective catalysts is vital for promoting nonthermal plasma (NTP)-assisted ammonia (NH3) synthesis toward practical applications. Herein, we report a simple mechanochemical synthesis method (via ball milling) for preparing bimetallic RuCo supported on MgTiO3 catalyst (i.e., RuCo/MgTiO3-6-500) to be used in NTP-assisted catalytic NH3 synthesis. The physicochemical properties of the developed catalysts were investigated systematically with respect to the relevant process parameters of ball milling. Catalytic tests showed that, at a low specific energy input of 15 kJ L–1, the developed RuCo/MgTiO3-6-500 catalyst exhibited a high NH3 synthesis rate and an energy efficiency of ∼50 μmol min–1 gcat–1 and 1.54 gNH3kWh–1, respectively, which outperformed the monometallic Ru or Co control catalysts. Additionally, the energy barriers were calculated as a function of N2/H2 ratio for the NTP-catalytic NH3 synthesis over RuCo/MgTiO3-6-500, and the results were interpreted together with the activity data measured during the catalysis. It was found that the energy barrier approach may not be appropriate for discussing the energy required for the dynamics of interest in the NTP-catalytic system. Compared to MgTiO3-packed and plasma-alone systems, results by in situ optical emission spectroscopic (OES) diagnosis of the plasma-catalytic systems showed that the presence of active metal sites (i.e., Ru and/or Co) could intensify the activation and dissociation rates of N2 and H2 molecules, showing the relatively higher peak intensity of NH, N2*, N2+, and Hα species. However, based on the obtained information, the possible roles of Ru and/or Co in NTP-assisted ammonia synthesis system are difficult to be identified.

Promoting Effect of Ni on the Catalytic Production of Alanine from Lactic Acid over RuNi/AC Catalyst

A series of RuNi bimetallic catalysts supported on activated carbon were prepared to study the reductive amination of lactic acid. Among the tested catalysts, the catalyst containing 40% Ni and 60% Ru was selected as the optimal catalyst. The yield of alanine significantly increased to 64% using the Ru6Ni4 catalyst supported on an activated carbon, which was 1.5 times that using the monometallic Ru catalyst supported on an activated carbon. A number of characterization methods such as transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction (TPR) were used to characterize monometallic and bimetallic catalysts. The strong electron transfer between Ni and Ru and the highly dispersed structure of metal on the surface of the support contributed to the excellent catalytic performance of Ru6Ni4. The Ru6Ni4 catalyst supported on activated carbon also exhibited good activity in the reductive amination of other α-hydroxyl acids to corresponding amino acids.

Effect of ZnSO4, MnSO4 and FeSO4 on the Partial Hydrogenation of Benzene over Nano Ru-Based Catalysts.

Nano Ru-based catalysts, including monometallic Ru and Ru-Zn nanoparticles, were synthesized via a precipitation method. The prepared catalysts were evaluated on partial hydrogenation of benzene towards cyclohexene generation, during which the effect of reaction modifiers, i.e., ZnSO4, MnSO4, and FeSO4, was investigated. The fresh and the spent catalysts were thoroughly characterized by XRD, TEM, SEM, XPS, XRF, and DFT studies. It was found that Zn2+ or Fe2+ could be adsorbed on the surface of a monometallic Ru catalyst, where a stabilized complex could be formed between the cations and the cyclohexene. This led to an enhancement of catalytic selectivity towards cyclohexene. Furthermore, electron transfer was observed from Zn2+ or Fe2+ to Ru, hindering the catalytic activity towards benzene hydrogenation. In comparison, very few Mn2+ cations were adsorbed on the Ru surface, for which no cyclohexene could be detected. On the other hand, for Ru-Zn catalyst, Zn existed as rodlike ZnO. The added ZnSO4 and FeSO4 could react with ZnO to generate (Zn(OH)2)5(ZnSO4)(H2O) and basic Fe sulfate, respectively. This further benefited the adsorption of Zn2+ or Fe2+, leading to the decrease of catalytic activity towards benzene conversion and the increase of selectivity towards cyclohexene synthesis. When 0.57 mol·L−1 of ZnSO4 was applied, the highest cyclohexene yield of 62.6% was achieved. When MnSO4 was used as a reaction modifier, H2SO4 could be generated in the slurry via its hydrolysis, which reacted with ZnO to form ZnSO4. The selectivity towards cyclohexene formation was then improved by the adsorbed Zn2+.

Catalytic Reforming of the Aqueous Phase Derived from Diluted Hydrogen Peroxide Oxidation of Waste Polyethylene for Hydrogen Production.

The thermal degradation and conversion of waste polyethylene (PE) using a two-step process including hydrothermal oxidation (HO) and aqueous phase reforming (APR) were investigated. The objective of this study was to achieve efficient disposal of waste PE and generate H2 in a mild and green way. The effects of various HO conditions on both HO and APR processes were studied. A high H2 O2 concentration caused overoxidation of PE resulting in more CO2 . Decreasing the H2 O2 concentration weakened the overoxidation. The process using diluted H2 O2 exhibited the highest selectivity for acetic acid among the produced carboxylic acids. When the HO temperature exceeded 200 °C, there was an increase in the CO2 yield during the HO process and a decrease in the H2 yield during the APR process. In addition, the effects of various monometallic and bimetallic catalysts on the reforming of the aqueous phase from the HO of PE were discussed. The highest H2 mole fraction (51.52 %) in gaseous products from the APR process was obtained with Ru/mesoporous carbon. Nevertheless, Ru-Ni exhibited a higher stability than the monometallic Ru catalyst.

Engineering Ru atomic structures toward enhanced kinetics of hydrogen generation

Herein, we demonstrate a strategy of engineering Ru atomic structures by fine-tuning Cl and Co coordination to synergize the quantity and quality of Ru active sites for boosting hydrogen generation from ammonia borane hydrolysis, via engineering the Cl-free/Cl-containing monometallic Ru catalysts and Co-leaching/Co-containing bimetallic Ru-Co catalysts. Under similar Ru particle sizes, the correlation between Ru binding energy and hydrogen generation activity affords a quantitative discrimination of Ru electronic and geometric contributions, where the site blockage and steric hindrance of Ru by Cl are more detrimental to hydrogen generation compared with the electronic modification by charge donation from Co to Ru. Reversely, the acid-leaching of Co from bimetallic catalysts creates abundant edge-like Ru active sites with much lower H2O activation barrier, as indicated by the kinetics switch from a Cl coverage-limited regime to a reactant activation regime, thus yielding a significant 4.1-fold increase in hydrogen generation activity.

Experimental Study on CO2 Methanation over Ni/Al2O3, Ru/Al2O3, and Ru-Ni/Al2O3 Catalysts

CO2 methanation is recognized as one of the best technologies for storing intermittent renewable energy in the form of CH4. In this study, CO2 methanation performance is investigated using Ni/Al2O3, Ru/Al2O3, and Ru-Ni/Al2O3 as the catalysts under conditions of atmospheric pressure, a molar ratio of H2/CO2 = 5, and a space velocity of 5835 h−1. For reaction temperatures ranging from 250 to 550 °C, it was found that the optimum reaction temperature is 400 °C for all catalysts studied. At this temperature, the maximum values of CO2 conversion, H2 efficiency, and CH4 yield and lowest CO yield can be obtained. With temperatures higher than 400 °C, reverse CO2 methanation results in CO2 conversion and CH4 yield decreases with increased temperature, while CO is formed due to reverse water-gas shift reaction. The experimental results showed that CO2 methanation performance at low temperatures can be enhanced greatly using the bimetallic Ru-Ni catalyst compared with the monometallic Ru or Ni catalyst. Under ascending-descending temperature changes between 250 °C and 550 °C, good thermal stability is obtained from Ru-Ni/Al2O3 catalyst. About a 3% decrease in CO2 conversion is found after three continuous cycles (74 h) test.

Selective Hydrogenation of Dimethyl Terephthalate to 1,4-Cyclohexane Dicarboxylate by Highly Dispersed Bimetallic Ru-Re/AC Catalysts.

The fabrication of bimetallic catalysts has been taken great focus in the concept of heterogeneous catalysis due to their high efficiency and economic concerns. In this work, a series of bimetallic Ru-Re catalysts were designed and synthesized for the selective hydrogenation of dimethyl terephthalate (DMT) to 1,4-cyclohexane dicarboxylate (DMCD) under mild condition. Characterization techniques including the XRD, TEM, STEM-HAADF EDX elemental mapping, H2-TPR, and XPS were used to study the surface chemical property, the morphology, as well as the catalytic behavior of different samples. It was revealed that the monometallic Ru catalyst already has the capacity to activate and transform DMT into DMCD. Whilst the promotion effect can be optimized to a maximum with only small amount of Re, with the mass ratio of Ru/Re as 10:1. It was also revealed that the addition of Re could largely enhance the distribution of surface active metal species, facilitate the charge transfer between Ru and Re, as well as strengthen the Ru-Re synergistic interaction, which further led to the modification of the redox ability and the catalytic performances of samples. However, excessive addition of Re caused strong interaction between Ru and Re, and further limited the H₂ activation and the seasonable release of the active reducible metal species, which was responsible for the depressed catalytic performances in the presence of higher Re loading. The Ru1.25Re0.13/AC catalyst displayed the DMT conversion of 82% with DMCD selectivity of 96% under mild condition of 70 °C at 3 MPa. The specific rate of Ru1.25Re0.13/AC based on per gram of Ru was 0.44 mol·g-1 Ru·h-1.

Ru‐Pt catalysts supported on Al2O3 and SiO2─Al2O3 for the selective ring opening of naphthenes

AbstractAlumina and silica‐alumina supported Ru‐Pt catalysts were evaluated for the ring opening of naphthenes. Pt, Ru, and Ru‐Pt catalysts were prepared by the impregnation of inorganic precursors over γ‐alumina and silica‐alumina supports. The catalysts were evaluated by temperature programmed reduction (TPR), pyridine temperature programmed desorption (TPD), CO‐FTIR, and by test reactions of 33DM1B isomerization, cyclohexane dehydrogenation, cyclopentane hydrogenolysis, and the ring opening of decalin. The strong interaction between the metals (Pt‐Ru) was attributed to their reductions occurring simultaneously. The acidity and strength of the acid sites of the monometallic Ru catalyst were higher than those of the monometallic Pt catalyst. The total acidity (Lewis and Brønsted) and the strength of the acid sites were higher for the silica‐alumina supported catalysts. The silica‐alumina catalysts had 10 times more Brønsted acidity than the γ‐alumina ones and an increased activity and selectivity to decalin ring opening products. Supported monometallic Ru had the best performance for the ring opening reaction.

Stable bimetallic Ru-Mo/Al2O3 catalysts for the light alkane combustion: Effect of the Mo addition

A series of Ru-Mo/γ-Al2O3 catalysts containing fixed Ru loading (5 wt.%) and variable Mo contents (1.6, 4.8 and 9.5 wt.%), were synthesized by co-impregnation method using Ru(NO)(NO3)3 and (NH3)6Mo7O24×4H2O as metal precursors and their catalytic characteristics were evaluated for the first time in combustion of propane used as a model compound. The effect of the Ru/Mo atomic ratio (3:1, 1:1 and 1:2) on the structure of the reduced samples was investigated by ICP-AES, BET, XRD, HRTEM, SEM-EDX, H2-TPR and chemisorption of hydrogen and oxygen. The surface properties of the catalysts were detailed studied by XPS spectroscopy. Structural characterization data lead to conclusion that a synergy effect of ruthenium and molybdenum is observed in the Ru-Mo/γ-Al2O3 catalysts. An increase of Mo loading caused the formation of smaller nanoparticles (dav = 1.3, 1.0 and 0.8 nm, respectively) as compared to the monometallic Ru system (dav = 1.4 nm). For low Mo loading (Ru:Mo atomic ratio of 3:1) the H2 uptake was higher (H/Ru = 0.55) than in the Ru/γ-Al2O3 sample (H/Ru = 0.52). This leads to the high activity of the 5%Ru-1.6%Mo catalyst in the propane combustion (TOF = 0.034 (s−1)). Moreover, the catalytic stability was much higher for the bimetallic Ru-Mo systems than for the monometallic Ru catalyst. Despite their high thermal stability under oxygen-rich atmosphere, bimetallic catalyst containing 4.8%Mo (Ru:Mo atomic ratio of 1:1) was less active in propane oxidation (TOF = 0.016 (s−1)) than the Ru system (TOF = 0.029 (s−1)). The lower activity results from partial blocking the active centers on the ruthenium by covering them with an inactive MoOx layer. At the highest Mo content (Ru:Mo atomic ratio of 1:2) the blocking of the active Ru centres increases, much lower H2 chemisorption capacity and a significant increase of the metallic Ru (74%) and metallic Mo (25%) species, resistant to oxidation at low temperature, were observed. This leads to very low activity of the 5%Ru-9.5%Mo catalyst in the propane combustion. Importantly, our studies also revealed that the molybdenum modifies interaction of hydrogen and oxygen with ruthenium in the Ru-Mo catalysts. For hydrogen, the adsorption process becomes activated and Mo species weaken the adsorption strength.

Ru-Catalyzed methanol homologation with CO2 and H2 in an ionic liquid

A monometallic Ru catalyst can efficiently accelerate ethanol synthesis via methanol homologation with CO2 and H2 in an ionic liquid.

Monometallic Ru, Au, and Pt Catalysts Deposited on Carbon Nanotubes for Oxidative Steam Reforming of Methanol

Monometallic Ru, Au, and Pt Catalysts Deposited on Carbon Nanotubes for Oxidative Steam Reforming of Methanol

Selective Hydrogenation of Benzene to Cyclohexene over Monometallic Ru Catalysts: Investigation of ZnO and ZnSO4 as Reaction Additives as Well as Particle Size Effect

Monometallic Ru catalysts with different particle size were prepared via a precipitation method and reduced at different temperatures. In addition, their catalytic activity towards cyclohexene formation from selective hydrogenation of benzene was investigated. With the utilization of ZnO and ZnSO4 as reaction additives, (Zn(OH)2)3(ZnSO4)(H2O)3 could be generated and chemisorbed on the Ru surface, which played a crucial role on increasing the selectivity to cyclohexene and retarding the catalytic activity towards benzene conversion. Interestingly, without addition of ZnO and ZnSO4, no cyclohexene was observed over all tested Ru catalysts with different particle sizes. This suggested that particle size plays no role in cyclohexene synthesis from selective hydrogenation of benzene over the pure monometallic Ru catalysts in the absence of ZnO and ZnSO4. On the other hand, when both ZnO and ZnSO4 were applied, surface n(Zn2+)/n(Ru) molar ratio increased with increasing particle size of the monometallic Ru catalysts after catalytic experiments, demonstrating that the content of chemisorbed (Zn(OH)2)3(ZnSO4)(H2O)3 on Ru catalysts surface is enhanced under such a circumstance. More importantly, the maximum cyclohexene yield obtained over monometallic Ru catalysts showed a volcanic-type variation with increasing particle size of Ru from 3.6 nm to 5.6 nm. When the particle size of the monometallic Ru catalyst was 4.7 nm, the highest cyclohexene yield of 60.4% was achieved with an optimum n(ZnO)/n(Ru) ratio of 0.19:1 in the presence of 0.62 mol·dm−3 ZnSO4 within 25 min of catalytic experiments at 423 K under 5.0 MPa of H2. In addition, no decrease of catalytic activity towards cyclohexene generation was observed over this catalyst after 10 catalytic experiments without any regeneration.

Cooperative action of heteropolyacids and carbon supported Ru catalysts for the conversion of cellulose

Acid hydrolysis and hydrogenation/hydrogenolysis reactions can be combined for catalytic conversion of cellulose into renewable biorefinery feedstocks by using heterogeneous bifunctional catalysts. In the present study a cooperative effect of heteropolyacids (HPA) and Ru nanoparticles supported on two carbon materials is demonstrated. The process can be suitable for the one-pot tandem reaction, yielding the conversion of cellulose into alkanediols (mainly propylene glycol and ethylene glycol).From a mechanistic point of view the differences in the distribution of polyol products, obtained from the cellulose reaction over monometallic Ru catalysts or over bifunctional Ru-HPAs materials, seem to be strongly determined by the competitive reactions of the sucrose (glucose+fructose) intermediate. HPA not only promote, as solid acids, the efficient hydrolysis of cellulose to glucose, but also catalyze the selective cleavage of the CC bonds in glucose and fructose, leading to the formation of ethylene glycol and propylene glycol. These reactions are in competition with the sugar hydrogenation to the corresponding C6 polyols (e.g. sorbitol), which takes place on the single Ru surface sites. The strong dependence of the product distribution on both catalytic functions is clarified by the kinetic analysis of the three competitive reactions of glucose, including its hydrogenation, isomerization and CC bond cleavage.Finally, considering the applicability of this reaction, it should be raised that the ball-milling pretreatment of cellulose is compulsory. In fact, during this ball-milling the crystallinity and particle size of cellulose are reduced, which results in a much higher conversion of cellulose. Herein, mixed ball-milling of cellulose and solid catalysts together was presented, which remarkably accelerates the cellulose conversion into valuable products.

Aqueous phase hydrogenation of furfural using carbon-supported Ru and RuSn catalysts

The aqueous phase hydrogenation (APH) of furfural was studied over carbon-supported monometallic Ru and bimetallic RuSn catalysts at 90°C and 1.25MPa. Tin was added via Surface Organometallic Chemistry on Metals techniques and its effect was a function of the Sn/Ru atomic ratio. Thus, the addition of Sn in a Sn/Ru ratio of 0.4 promoted the CO hydrogenation reaching a selectivity towards furfuryl alcohol over 85% throughout the course of the reaction. A higher concentration of tin does not improve the situation. It seems to be a compromise between the dilution of Ru sites, active for the hydrogenation reaction, and the promoting effect of Sn. TEM, TPR and XPS characterization indicate the strong interaction between Ru and Sn in all the bimetallic catalysts. Finally, the reuse of the catalyst was analyzed.

Support Screening Studies on the Hydrogenation of Levulinic Acid to γ-Valerolactone in Water Using Ru Catalysts

γ-Valerolactone (GVL) has been identified as a sustainable platform chemical for the production of carbon-based chemicals. Here we report a screening study on the hydrogenation of levulinic acid (LA) to GVL in water using a wide range of ruthenium supported catalysts in a batch set-up (1 wt. % Ru, 90 °C, 45 bar of H2, 2 wt. % catalyst on LA). Eight monometallic catalysts were tested on carbon based(C, carbon nanotubes (CNT)) and inorganic supports (Al2O3, SiO2, TiO2, ZrO2, Nb2O5 and Beta-12.5). The best result was found for Ru/Beta-12.5 with almost quantitative LA conversion (94%) and 66% of GVL yield after 2 h reaction. The remaining product was 4-hydroxypentanoic acid (4-HPA). Catalytic activity for a bimetallic RuPd/TiO2 catalyst was by far lower than for the monometallic Ru catalyst (9% conversion after 2 h). The effects of relevant catalyst properties (average Ru nanoparticle size, Brunauer-Emmett-Teller (BET) surface area, micropore area and total acidity) on catalyst activity were assessed.

Highly efficient Ru/carbon catalysts prepared by pyrolysis of supported Ru complex towards the hydrogen production from ammonia borane

Highly efficient carbon-supported Ru catalysts towards the H2 production from the ammonia borane (AB: NH3BH3) hydrolysis reaction have been developed by using tri(2,2′-bipyridyl) ruthenium (II) chloride hexahydrate as metal precursor. Different temperatures were used to decompose the metal precursor, which afford the preparation of various nanoparticles sizes, ranging from 3.8 to 13.5nm. The catalytic results revealed that both geometric and electronic features of the metal nanoparticles are crucial to attain optimum catalytic activity towards the H2 production from the hydrolysis of AB. The optimum catalyst under the experimental condition used was that prepared at 800°C, which efficiently boosts the hydrolysis of AB, achieving an average TOF number of 670mol H2/mol metal min, which is among the highest values ever reported for a monometallic Ru catalyst in this reaction up to date.