Catalytic Hydrogenation Of 4-nitrophenol Research Articles

Waste-Derived Caffeine for Green Synthesis of Rhenium Nanoparticles with Enhanced Catalytic Activity in the Hydrogenation of 4-Nitrophenol

Yearly, thousands of tons of wasted coffee grounds are produced according to high coffee consumption. Still, after the coffee brewing, wasted coffee grounds contain some amounts of caffeine (CAF). CAF, in turn, contains multiple O and N chelating atoms in its structure. These have a potential to be reductors for complexes of metals. In this context, within the present study, a set of CAF extracts derived from coffee beans and coffee grounds were obtained and then used for the one-step reduction of ReO4− ions with no additional toxic chemicals. Within this approach, CAF was applied as a secondary, green resource for the synthesis of unique rhenium nanoparticles (ReNPs) containing Re species at 0 and +6 oxidation states. The obtained ReNPs were identified and characterized with the use of X-ray powder diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Further, the capping and stabilization of ReNPs by CAF were verified with the aid of Fourier transformation infrared spectroscopy (FT-IR). The so-obtained “green” ReNPs were then used as a homogenous catalyst in the catalytic hydrogenation of 4-nitrophenol (4-NP). This new nanomaterial revealed a superior catalytic activity, leading to the complete reduction of 4-NP to 4-aminophenol within 40–60 min with a first-order rate constant of 0.255 min−1.

Recyclable and Biodegradable Ag@Chitosan Nanocomposite Beads Synthesized in One-step for Catalytic Hydrogenation of 4-Nitrophenol

The study presents the in-situ synthesis of recyclable bio-nanocomposite beads based on chitosan (Cs) and silver (Ag) nanoparticles for utilization in catalytic processes. For the first time, alkaline ethanol solution was used as a physical crosslinking and reducing agent to synthesize cross-linked Ag@Cs biocomposite hydro-gel beads in one-step. The catalytic activity of the prepared beads was evaluated before and after the integration of various Ag contents through hydrogenation of toxic nitrophenol to amino-phenol, as a safer configuration. XRD, SEM, EDX, BET, UV-Vis, HRTEM, FT-IR, and TGA analyses were used to characterize the resulted samples. XRD, EDX, and optical measurements confirmed the successful immobilization of Ag into Cs beads. The grown Ag atoms are well dispersed in the Cs, with an average diameter of around 6.7 nm, according to HRTEM. Because of the synergistic effect of Ag sensitization and large surface area, the optumium Ag@Cs composite beads have high catalytic activity with a kinetic rate constant of 0.143 min− 1, compared to 0.0001 min− 1 for pure Cs beads. Furthermore, regeneration studies were performed to ensure its catalytic stability in the removal of nitrophenol. Finally, the mechanism of Ag@Cs biocomposite hydrogel beads fabrication in a single pot was thoroughly discussed.

PtCo nanoparticles supported on hierarchical SAPO-34 for hydrolysis of ammonia borane and tandem reduction of 4-nitrophenol

In this work, hierarchical SAPO-34 supported PtCo bimetallic catalysts with different Pt/Co ratios were prepared by impregnation method. The obtained PtCo/SAPO-34 catalysts displayed high catalytic activities and durability for the dehydrogenation of ammonia borane (AB). Among them, Pt1Co5/SAPO-34 catalyst delivered the highest hydrogen generation activity with a turnover frequency (TOF) of 262 molH2(molPt∙min)−1 at 303 K as well as excellent catalytic activity in catalytic hydrogenation of 4-nitrophenol (4-NP) by coupling with hydrolytic dehydrogenation of AB, due to the electron interaction of Pt and Co in PtCo alloy and the high metal dispersion and exposure of Brønsted acidic sites on SAPO-34 support. Moreover, it is noteworthy that the prepared Pt1Co5/SAPO-34 catalyst also exhibited superior recycle stability, with 81% of the initial TOF value after five runs of hydrolysis reaction.

Stability and catalytic activity of hyperbranched polyglycerol stabilized gold nanofluids

A gold nanofluid with good suspension stability was prepared using hyperbranched polyglycerol (HPG) as a stabilizer because of the functional hydroxyl groups at the end of every branch in its structure. The effects of reaction-medium pH and temperature on the preparation of the HPG-gold nanofluids were discussed. The influences of pH on the stability of HPG-gold nanofluids after preparation were investigated. The HPG-gold nanofluid was employed as catalyst for the reduction of 4-nitrophenol. The results showed that HPG-Au nanofluid stabilized at high pH range (pH = 10). The nanofluid exhibited high activity in the catalytic hydrogenation of 4-nitrophenol. The HPG-gold nanofluid was promising for applications of quasi-homogeneous catalysis.

Synergistic effects of carbon-encapsulated cobalt/tricobalt tetroxide nanocapsules on hydrogenation of 4-nitrophenol

In this paper, we fabricated carbon-encapsulated cobalt/tricobalt tetroxide complex nanomaterials (Co/Co3O4@C) by a simple arc-discharged method and controlled annealing in air. Controlled annealing can solve the problem of poor hydrophilicity of materials prepared by arc-discharged method, and what’s more, a large number of Co/Co3O4 heterointerfaces can be constructed. Carbon-encapsulated Co/Co3O4 exhibited excellent catalytic performance in the catalytic hydrogenation of 4-nitrophenol (4-NP), even better than that of the reported precious metal catalysts in the literature. Excellent catalytic performance not only contributed to improved hydrophilicity, but also contributed to the synergistic effects of Co and Co3O4 on the catalytic 4-NP hydrogenation. The preparation process is appropriate for synthesizing various defective-rich metals or alloy@carbon electrocatalysts.

Bioinspired silver nanoparticles/reduced graphene oxide nanocomposites for catalytic reduction of 4-nitrophenol, organic dyes and act as energy storage electrode material

Facile and a novel technique for bioinspired synthesis of silver nanoparticles (AgNPs) using an aqueous extract of mango (Mangifera indica) flower as stabilizing and reducing agent was demonstrated. The formation of AgNPs and AgNPs/rGO nanocomposites were confirmed through extensive experimental characterization and numerical analysis. Both, AgNPs and AgNPs/rGO nanocomposites showed excellent catalytic performance in catalytic hydrogenation of 4-nitrophenol and azo bond in dye molecules. The rGO supported Ag nanocomposites exhibited improved catalytic activity compared to AgNPs due to the enhancement of surface area. Electrochemical analysis of AgNPs/rGO nanocomposites showed specific capacitance (SC) of ∼532 F g−1 at a current density of 1.0 A g−1. About 92% retention in SC after 2000 charge-discharge cycles suggested long-term electrochemical cyclic stability as supercapacitor electrode materials. The biogenic nano-particles and composites implied that the rGO reinforced Ag excellent applicants as hydrogenation refining materials. All these observations demonstrated a novel, eco-cost effective and estimable candidates as hydrogenation refining materials and electrode materials.

Toward High Activity and Durability: An Oxygen-Rich Boron Nitride-Supported Au Nanoparticles for 4-Nitrophenol Hydrogenation

Catalytic hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) is widely recognized as one of the most effective solutions to deal with the water-related environmental issues, where catalysts with high activity and long cycle life are always pursued. In this paper, oxygen-rich boron nitride (BNO)-supported Au nanoparticles (Au/BNO) were proposed to serve as catalysts for 4-NP hydrogenation. Our results show that the Au nanoparticles are well dispersed on the highly porous BNO substrate with a small particle size of 2.2 nm. Under the optimal reaction conditions, the 4-NP molecules could be completely reduced to 4-AP in 2.5 min over Au/BNO with a relatively high conversion rate constant of 2.25 min–1. Moreover, the as-synthesized Au/BNO is also highly stable with no visible efficiency decay after been reused for several times. The excellent durability of the catalyst could be ascribed to the strong anchoring strength between the Au nanoparticles and BNO substrate, leading to a negligible metal loss...

Silica-Protection-Assisted Encapsulation of Cu2 O Nanocubes into a Metal-Organic Framework (ZIF-8) To Provide a Composite Catalyst.

The integration of metal/metal oxide nanoparticles (NPs) into metal-organic frameworks (MOFs) to form composite materials has attracted great interest due to the broad range of applications. However, to date, it has not been possible to encapsulate metastable NPs with high catalytic activity into MOFs, due to their instability during the preparation process. For the first time, we have successfully developed a template protection-sacrifice (TPS) method to encapsulate metastable NPs such as Cu2 O into MOFs. SiO2 was used as both a protective shell for Cu2 O nanocubes and a sacrificial template for forming a yolk-shell structure. The obtained Cu2 O@ZIF-8 composite exhibits excellent cycle stability in the catalytic hydrogenation of 4-nitrophenol with high activity. This is the first report of a Cu2 O@MOF-type composite material. The TPS method provides an efficient strategy for encapsulating unstable active metal/metal oxide NPs into MOFs or maybe other porous materials.

Multi-metal nanomaterials obtained from oil/water interface as effective catalysts in reduction of 4-nitrophenol

In this study Pt and Pd-based nanostructured thin films have been successfully fabricated by room temperature self-assembly of metal nanoparticles (NPs) at the interface between toluene and water without/with using stabilizers such as graphene oxide (GO) or aminoclay (AC). Successful formation of these thin films is investigated by transmission electron microscopy (TEM), energy dispersive analysis of X-ray (EDAX) and X-ray diffraction (XRD). Catalytic hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) was investigated using thin film nanocatalysts. The as synthesized nanostructured thin films exhibit high catalytic activity toward hydrogenation reaction of 4-NP. This study highlights the value of nano alloy thin films and their ability as catalyst in catalytic hydrogenation reaction.

Multifaceted Gold-Palladium Bimetallic Nanorods and Their Geometric, Compositional, and Catalytic Tunabilities.

Kinetically controlled, seed-mediated co-reduction provides a robust and versatile synthetic approach to multimetallic nanoparticles with precisely controlled geometries and compositions. Here, we demonstrate that single-crystalline cylindrical Au nanorods selectively transform into a series of structurally distinct Au@Au-Pd alloy core-shell bimetallic nanorods with exotic multifaceted geometries enclosed by specific types of facets upon seed-mediated Au-Pd co-reduction under diffusion-controlled conditions. By adjusting several key synthetic parameters, such as the Pd/Au precursor ratio, the reducing agent concentration, the capping surfactant concentration, and foreign metal ion additives, we have been able to simultaneously fine-tailor the atomic-level surface structures and fine-tune the compositional stoichiometries of the multifaceted Au-Pd bimetallic nanorods. Using the catalytic hydrogenation of 4-nitrophenol by ammonia borane as a model reaction obeying the Langmuir-Hinshelwood kinetics, we further show that the relative surface binding affinities of the reactants and the rates of interfacial charge transfers, both of which play key roles in determining the overall reaction kinetics, strongly depend upon the surface atomic coordinations and the compositional stoichiometries of the colloidal Au-Pd alloy nanocatalysts. The insights gained from this work not only shed light on the underlying mechanisms dictating the intriguing geometric evolution of multimetallic nanocrystals during seed-mediated co-reduction but also provide an important knowledge framework that guides the rational design of architecturally sophisticated multimetallic nanostructures toward optimization of catalytic molecular transformations.

Novel synthesis of silver/reduced graphene oxide nanocomposite and its high catalytic activity towards hydrogenation of 4-nitrophenol

Ag/RGO nanocomposites were prepared via reducing AgNO3 in a macroscopic RGO aerogel directly through a convenient impregnation process, which exhibited high activity in the catalytic hydrogenation of 4-nitrophenol.