Immobilized highly dispersed Ni nanoparticles over porous carbon as an efficient catalyst for selective hydrogenation of furfural and levulinic acid

Abstract Sustainable catalysis is the key for the future progress toward biorefinery and bioeconomy. In this work, we designed and developed an inexpensive and eco-friendly Ni@C catalyst for selective hydrogenation of biomass-based platform molecules. A facile synthesized Ni nanoparticles encapsulated in a stabilized carbon support derived from a sacrificial agent copolymer-gel was investigated in the hydrogenation of furfural (FA) to tetrahydrofurfuryl alcohol (THFOL) and levulinic acid (LA) to γ-valeralactone (GVL). The aim is to study the two different reactions over a highly stabilized Ni nanoparticles embedded in the carbon matrix. The Ni@C was found to be active and selective in multi-catalyzed hydrogenation reactions. The Ni nanoparticles with small and ultra-fine sizes are highly dispersed over the carbon matrix. This was concluded through high-resolution micrography images (SEM, TEM) and XRD patterns. In both reactions, a complete conversion of furfural and levulinic acid was achieved with maximum selectivity over the Ni@C catalyst. The effect of reaction temperature, solvent type, reaction time, and H₂ pressure were also studied. Overall, optimized reaction conditions were determined, and the Ni@C is easily reusable and exceptionally durable in the studied reaction cycles. The apparent activation energies for FA hydrogenation to THFOL and LA hydrogenation to GVL are 15.4 kJ/mol and 33.6 kJ/mol, respectively

Anisotropic phenanthroline-based ruthenium polymers grafted on a titanium metal-organic framework for efficient photocatalytic hydrogen evolution

Combining conjugated polymers with transition-metal-based metal-organic frameworks offers an opportunity to produce efficient photocatalytic materials. Here, exposed active sites and efficient charge transfer lead to hydrogen evolution rates of up to 2438 µmol g−1 h−1 for composites of anisotropic phenanthroline-based ruthenium polymers grafted on titanium-based MOFs

Morphologically tailored facet dependent silver nanoparticles supported α-Al₂O₃ catalysts for chemoselective reduction of aromatic nitro compounds

Abstract The nanoparticles surface area, intrinsic sites, exposed microcrystal shapes and lattice planes are some of the key factors in nanocatalysis. The influence of nanoparticles shape dependent had been profound effect on its catalytic activity. This study is focused on the synthesis of morphologically shape-controlled silver (Ag) nanoparticles supported on α-Al₂O₃ catalysts were performed. The correlation of Ag NPs with varied facets and lattice planes on the catalytic activities in chemoselective reduction of nitro compounds was investigated. Engineering the silver nanoparticles with different shapes and facets i.e., nanocubes (AgNCs), nanowires (AgNWs) and nano spheres (AgNSPs) were synthesized by using modified polyol method. It is demonstrated that there is a significant difference in their activities with respect to the shape and nanocrystal facets. The evolution of nanoshapes and the structural properties of Ag nanoparticles were analysed by SEM, TEM, HR-TEM and P-XRD techniques. From XRD, Ag nanocubes exhibited high percentage of low index (1 0 0) facets which are favourable active centers than (1 1 1) plane in nitro reduction. We observed that the silver nanocubes selectively exposed (1 0 0) facets, which are highly favorable for the enhanced catalytic activity in nitro reduction. The reaction rate of nitro phenol to amino phenol over different Ag nanoshapes are 35.01×10−3min−1(AgNCs/Al₂O₃), 8.28×10−3min−1(AgNWs/Al₂O₃), 0.65×10−3 min−1(AgNSPs/Al₂O₃), respectively. The calculated thermodynamic parameters of the Ea values 23.6, 28.6 and 29.4 for the AgNC, AgNWs and AgNSP respectively

Synergistic effects of graphene oxide grafted chitosan & decorated MnO2 nanorods composite materials application in efficient removal of toxic industrial dyes

Abstract In this study, we designed a heterogeneous graphene oxide (GO) grafted on chitosan decorated with MnO2 nanorods (α-MnO2NRs/GO-Chit) composite materials and its ability to remove the cationic and anionic toxic dyes from wastewaters were analysed. The synthesised materials presented an effective stabilization of active MnO2 nanorods (NRs) on the GO-Chit surface. The synthesised materials were detailed characterised by several spectroscopic and microscopic techniques such as, FT-IR, P-XRD, SEM, TEM, Raman, TGA, XPS, BET, CO2-TPD and UV–Visible analysis. In addition, α-MnO2NRs/GO-Chit material is successfully applied in removal of industrial ionic dyes such as amido black 10B (AB) and methylene blue (MB), respectively. The dye adsorption experiments confirmed that the GO-Chit/α-MnO2 NRs material exhibited remarkably high adsorption capacity in efficient removal of cationic dye methylene blue (MB) and anionic dye amido black 10B (AB). The maximum MB dye removal (97%) process completed in 24 min at C0 = 30 mg·L-1, but in the case of AB the maximum dye removal (80%) process was reached in 700 min. Over GO-Chit/α-MnO2 NRs hybrid material, a maximum theoretical monolayer adsorption (qmax values is 328.9 mg g-1) of MB was calculated from the Langmuir isotherm equation. In case MB, a faster adsorption and 2.18 times maximum adsorption capacity was achieved than that of AB10 dye. The enhanced adsorption over α-MnO2NRs/GO-Chit is due to the increased surface functionalities (i.e., oxygen-containing groups), high basicity and strong electrostatic forces between MnO2 nanorods and GO-Chit. Furthermore, α-MnO2NRs/GO-Chit hybrid material displayed good stability after 10 successive adsorption tests

Selective hydrogenation of levulinic acid over a highly dispersed and stable copper particles embedded into the ordered mesoporous carbon supported catalyst

Abstract Transformation of levulinic acid (LA) to γ -valerolactone (GVL) via hydrogenation is a greener approach in synthesising the eco-friendly GVL fuel additive. In this work, highly active and stable pre-synthesized copper nanoparticles (CuNPs) are embedded and distributed into the ordered mesoporous carbon (OMC) support material by the chelate-assisted multicomponent assembly pathway method. The Cu/OMC nanocatalyst is characterized by different analytical instruments to determine the key properties. The ordered mesoporous carbon (OMC) structure was formed successfully by controlled synthesis steps via resol carbonization. The morphology and structure of OMC was confirmed by the XRD, TEM and HRTEM analysis. The OMC surface was functionalized with different oxygen-containing functional groups, which enhances the interactions with the Cu nanoparticles. The TEM micrographs reveal that Cu NPs with average size of ~5.5 nm was evenly distributed over the surface of the OMC matrix. The synthesized Cu/OMC catalyst showed remarkable activity and stability due to confinement effects of Cu in mesoporous carbon and the highly dispersed nanosized Cu particles, which are exposed sites over the support. More importantly, the stability of the Cu/OMC was excellent, and the activity did not decline even after 60 h time on stream test under optimized conditions (WHSV-2.28 h⁻¹, 20 wt% aqueous LA, H₂ flow- 30 mL/min, 260 °C at 0.1 MPa hydrogen pressure)

The role of AgNPs in selective oxidation of benzyl alcohol in vapor phase using morphologically tailored MnO₂ nanorods in the presence of air

Abstract Vapor phase benzyl alcohol (BnOH) oxidation reaction is investigated over a pre–synthesised morphologically designed shape controlled spherical silver nanoparticles (AgNPs) decorated on manganese oxide nanorods (α–MnO₂NRs) in the presence of air. The combination of silver nanoparticles and the α–MnO₂NRs interface enabled the increased oxygen vacancies (Ov) and exhibited the strong metal–support interactions (SMSI) in surface oxygen activation. The effect of Ag loadings is significant and the optimal 1 wt% Ag loaded catalyst (1Ag/MnO₂NRs) showed excellent performance in benzyl alcohol oxidation due to high adsorption capacity, enhanced oxygen vacancies and red–ox properties. The DFT calculations confirmed that the high BnOH surface adsorption was exhibited over Ag modified MnO₂NRs than the bare α–MnO₂NRs. The optimized 1Ag/α–MnO₂NRs catalytic system achieved 2.6 fold higher activity compared to bare α–MnO₂NRs. These results provided novel insights on the rational design of shape dependent metal/metal oxide based heterogeneous catalysts

Selective hydrogenolysis of biodiesel waste bioglycerol over titanium phosphate (TiP) catalysts:the effect of Pt & WO₃ loadings

Abstract Glycerol is an important by-product (biowaste) from biodiesel production. Transformation of glycerol into value-added compounds is critical in improving the overall efficiency of the biodiesel production. In this work, a sustainable and cleaner production of 1,3-propanediol (1,3-PDO) by vapor phase hydrogenolysis of glycerol was performed over titanium phosphate (TiP) supported catalysts by varying the Pt and WO₃ loadings (5–20 wt.%). The WO₃ promoted Pt modified TiP catalysts were prepared by a simple wet impregnation method and characterized by various analytical techniques in determining the key properties. Furthermore, the catalyst activity and stability were studied under different reaction conditions. The synergistic effects of Pt and WO₃ loadings on the final performance of the catalyst has been significant in improving the hydrogen transfer rate. Both Pt and WO₃ promotional effects is envisaged the enhanced catalytic properties in conjunction with TiP support acidity. WO₃ incorporation increased Brønsted acidity and formed strong interactions with Pt over TiP support. Both Lewis and Brønsted acid sites presented but BAS played a key role in enhancing the 1,3-PDO selectivity in a bifunctional dehydration-hydrogenation reaction mechanism of glycerol. The effect of reaction temperature, contact times and the weight hour space velocity were evaluated. Overall, under optimized reaction conditions, 2 wt.% Pt-10 wt.% WO₃/TiP catalyst displayed superior activity with a maximum glycerol conversion of ~ 85% and ~ 51% of 1,3-PDO selectivity achieved at time on stream of 4 h

Designing versatile nanocatalysts based on PdNPs decorated on metal oxides for selective hydrogenolysis of biomass derived γ-valerolactone and reduction of nitro aromatics

Abstract In this work, we designed versatile heterogeneous nanocatalysts based on palladium nanoparticles (PdNPs) decorated on metal oxides supports (i.e., PdNPs/γ-Al₂O₃, PdNPs/WO₃ and PdNPs/Nb₂O₅) by step-wise controlled synthesis of novel monodispersed ∼2 nm PdNPs at room temperature and then impregnated over metal oxides. PdNPs supported catalysts were characterised by powder XRD, TEM, HRTEM, NH₃-TPD, N₂-BET, H₂-TPR, and XPS techniques. PdNPs based catalysts studied in two different model reactions were presented i.e., biomass platform chemical intermediate γ-valerolactone (GVL) conversion into pentanoic acid (PA) studied in vapor phase hydrogenolysis and 4-Nitrophenol (4-NP) reduction to 4-Aminophenol (4-AP) in liquid phase using NaBH₄ as reducing agent over 0.5 wt% Pd nanoparticles -based nanocatalysts. The relationship between the active sites and the catalytic performance was evaluated. The Under optimized reaction conditions, over 0.5 wt% PdNPs/γ-Al₂O₃ catalyst exhibited the highest PA yield of 100%, and over 0.5 wt% PdNPs/WO₃, 0.5 wt% PdNPs/Nb₂O₅ exhibited PA yields of 98% and 96% respectively. Over PdNPs/γ-Al₂O₃, PdNPs/WO₃, and PdNPs/Nb₂O₅, the reduction reaction rates in the 4-NP to 4-AP are 5.40 × 10⁻³ s⁻¹, 2.55 × 10⁻³ s⁻¹ and 2.30 × 10⁻³ s⁻¹ respectively. The calculated thermodynamic parameters of the Ea values for 4-NP to 4-AP reaction were 25.30, 26.75, and 27.81 KJ/mol for the PdNPs/γ-Al₂O₃, PdNPs/WO₃ and PdNPs/Nb₂O₅, respectively