Catalysts For Hydrogenation Reactions Research Articles

Supported Palladium Nanocatalysts: Recent Findings in Hydrogenation Reactions

Catalysis has witnessed a dramatic increase on the use of metallic nanoparticles in the last decade, opening endless opportunities in a wide range of research areas. As one of the most investigated catalysts in organic synthesis, palladium finds numerous applications being of significant relevance in industrial hydrogenation reactions. The immobilization of Pd nanoparticles in porous solid supports offers great advantages in heterogeneous catalysis, allowing control of the major factors that influence activity and selectivity. The present review deals with recent developments in the preparation and applications of immobilized Pd nanoparticles on solid supports as catalysts for hydrogenation reactions, aiming to give an insight on the key factors that contribute to enhanced activity and selectivity. The application of mesoporous silicas, carbonaceous materials, zeolites, and metal organic frameworks (MOFs) as supports for palladium nanoparticles is addressed.

Vicinal Na+ as structure guardians of atomically dispersed Ru catalysts in hydrogenation reactions

Vicinal Na+ as structure guardians of atomically dispersed Ru catalysts in hydrogenation reactions

Technology Trends of Catalysts in Hydrogenation Reactions: A Patent Landscape Analysis.

The purpose of this review is to present an overview of the patent landscape for catalysts used in hydrogenation reactions. Based on patent data extracted from PatBase®, we use predefined patent classifications as well as a keyword‐based search for our analyses. The results indicate that the number of patent families that protect heterogeneous catalysts grows twice as fast as that for their homogeneous counterparts. Furthermore, the data show a shift towards abundant and non‐toxic elements in heterogeneous catalysis, while the noble metals continue to dominate the patent landscape of homogeneous catalysis. A subsequent geographical analysis reveals that the high growth rates in heterogeneous catalysis, especially for nickel and iron, are driven by China. Conversely, patenting activities with regard to homogeneous catalysts mainly take place in the USA, the EU, and Japan. The subsequent keyword‐based search illustrates the continuous industrial relevance of enantioselective hydrogenation and transfer hydrogenation, as well as the rapidly increasing body of patents in hydrodeoxygenation. Setting these finding into context, we present and apply two concepts that are commonly used in patent analyses, namely the technology life cycle and the S‐curve. We conclude that hydrogenation catalysis has not reached its peak economic relevance yet and will continue to spark valuable patents and innovations in the future.

The Promotion Effect of Transition Metals on Water‐Tolerant Performance of Cu/SiO2 Catalysts in Hydrogenation Reaction

AbstractThe effect of transition metals (Fe, Co, Ni, Zn) on water‐tolerant performance of Cu/SiO2 catalysts in hydrogenation reaction at industrially relevant conditions (containing water) was investigated. Notably, an improvement in the water‐tolerant hydrogenation performance, indexed by the decrease in the reaction temperature (from 280 to 240 °C) was achieved. The HRTEM showed the existence of crystal defects which formed at the border of copper species and doping metal species. Furthermore, XRD of catalysts after reaction showed the peak shift was existed, indicating crystal defects were existed in the reaction. From the result of Cu LMM and TPR, the doping of metal element could also increase the value of Cu+/(Cu0+Cu+) by adjusting the interaction between copper ion and silica. The in‐situ DRIFT visually showed the promotion effect of doping meal on hydrogenation reaction. Combined with hydrogenation performance, it could be found crystal defects and high Cu+/(Cu0+Cu+) were main factors to improve hydrogenation performance of Cu/SiO2 catalyst, which provided more active sites at relative low temperature and then improve the water‐tolerant performance. Furthermore, it was found the size of Cu+/(Cu0+Cu+) took major responsibility for the improvement of hydrogenation performance, and crystal defects played an auxiliary role. The Cu−Zn/SiO2 catalyst showed the best water‐tolerant hydrogenation performance with a high conversion and stability at low temperature reaction conditions.

Hydrogenated polycyclic aromatic hydrocarbons (HnPAHs) as catalysts for hydrogenation reactions in the interstellar medium: a quantum chemical model.

The sticking of H atoms onto dust grains and large hydrocarbon molecules has received considerable attention because it is thought to govern the formation of H2 and other H-containing molecules in the interstellar medium. Using the density functional theory (DFT) approximation, we have investigated the capacity of neutral hydrogenated polycyclic aromatic hydrocarbons (HnPAH) to catalyze simple hydrogenation reactions by acting as a source of atomic hydrogen. In particular, the interaction of OH and CO with H1-anthracene (singly hydrogenated) and H14-anthracene (fully hydrogenated) to form H2O and HCO was modeled following the Eley-Rideal mechanism. In this process, a hydrogen atom is abstracted from the HnPAH molecule forming the corresponding hydrogenated compound. The results were compared to the most known case of the HnPAH-catalyzed formation of H2. It was observed that whereas H2 is formed by overcoming activation barriers of approximately 0.02 and 0.10 eV with H1-anthracene and H14-anthracene, respectively, H2O is produced in a barrierless fashion with both hydrocarbon molecules. The production of HCO was found to be a highly unfavorable process (with activation barriers of 0.73 eV and 3.13 eV for H1- and H14-anthracene, respectively). Complementary calculations performed using the rest of the Hn-anthracene molecules (from 2 to 13 extra H atoms) showed that in all the cases the reaction with OH is barrierless as well. This efficient mechanism could therefore be a possible route for water formation in the cold interstellar medium.

HETEROGEN CATALYSIS IN SUSTAINABLE GREEN SOLVENT: ALKENES HYDROGENATION WITH NEW SILICA IMMOBILIZED PALLADIUM COMPLEX CONTAINING S,O-CHELATING LIGAND

Pd(II) complex containing S,O-chelating ligand was immobilized on surface of the amine functionalized silica support in scCO 2 media. Silica-based catalyst ( SiO 2 -ThiophPd(II)) were characterized by IR, SEM, XRF, and BET analyses. The catalytic activity of the immobilized catalyst in hydrogenation reactions of alkenes has been compared with the homogeneous counterpart. SiO 2 -ThiophPd(II) catalyst showed good activity and reusability than homogeneous system. The best conversion in styrene hydrogenation was obtained with TOF value as 5871 h -1 at 370 K, 10 bar H 2 and 1500 psi total pressure. Especially, while homogeneous counterpart has not activity in cyclohexene hydrogenation, it has been provided 100% cyclohexane conversion with the immobilized catalyst. It has also been found that the catalyst can be reused at least ten times without significant loss of activity in the styrene hydrogenation

A Durable Nickel Single-Atom Catalyst for Hydrogenation Reactions and Cellulose Valorization under Harsh Conditions.

Hydrothermally stable, acid-resistant nickel catalysts are highly desired in hydrogenation reactions, but such a catalyst remains absent owing to the inherent vulnerability of nickel under acidic conditions. An ultra-durable Ni-N-C single-atom catalyst (SAC) has now been developed that possesses a remarkable Ni content (7.5 wt %) required for practical usage. This SAC shows not only high activities for hydrogenation of various unsaturated substrates but also unprecedented durability for the one-pot conversion of cellulose under very harsh conditions (245 °C, 60 bar H2 , presence of tungstic acid in hot water). Using integrated spectroscopy characterization and computational modeling, the active site structure is identified as (Ni-N4)⋅⋅⋅N, where significantly distorted octahedral coordination and pyridinic N constitute a frustrated Lewis pair for the heterolytic dissociation of dihydrogen, and the robust covalent chemical bonding between Ni and N atoms accounts for its ultrastability.

Synthesis of N-Doped Mesoporous Carbon Nanorods through Nano-Confined Reaction: High-Performance Catalyst Support for Hydrogenation of Phenol Derivatives.

Traditional hard-template methods for the preparation of mesoporous carbon structures have been well developed, but there are difficulties associated with complete filling of the organic precursors in ordered mesochannels and exact replication of the templates. Herein, mesoporous carbon nanorods (meso-CNRs) were synthesized through thermal condensation of furfuryl alcohol followed by the nano-confined decomposition of polyfurfuryl alcohol in silica nanotubes (SiO2 NTs) with porous shells. Limited and slow release of gaseous water through the porous shells and finite polyfurfuryl precursor inside silica nanotubes are responsible for the formation of the mesoporous structures. Nitrogen can be doped into the meso-CNRs by adding guanidine hydrochloride to the precursors. The nitrogen dopant not only stabilizes the ultrasmall and active Pd nanocatalyst in the meso-CNRs but also increases the electron density of Pd and accelerates the dissociation of H2 , both of which increase the catalytic activity of the Pd catalyst in hydrogenation reactions.

Olefin-Stabilized Cobalt Nanoparticles for C=C, C=O, and C=N Hydrogenations.

The development of cobalt catalysts that combine easy accessibility and high selectivity constitutes a promising approach to the replacement of noble-metal catalysts in hydrogenation reactions. This report introduces a user-friendly protocol that avoids complex ligands, hazardous reductants, special reaction conditions, and the formation of highly unstable pre-catalysts. Reduction of CoBr2 with LiEt3 BH in the presence of alkenes led to the formation of hydrogenation catalysts that effected clean conversions of alkenes, carbonyls, imines, and heteroarenes at mild conditions (3 mol % cat., 2-10 bar H2 , 20-80 °C). Poisoning studies and nanoparticle characterization by TEM, EDX, and DLS supported the notion of a heterotopic catalysis mechanism.

Engineering active sites on reduced graphene oxide by hydrogen plasma irradiation: mimicking bifunctional metal/supported catalysts in hydrogenation reactions

H2 plasma generates carbon vacancies on reduced graphene oxide increasing its activity as a hydrogenation catalyst.

Facile one-pot synthesis of MOF supported gold pseudo-single-atom catalysts for hydrogenation reactions

Pseudo single atom Au/MOF catalysts are synthesized using a facile wet-chemistry approach on a large scale and show excellent performance in p-nitrophenol hydrogenation.

Hydrogenation of Unsaturated Hydrocarbons on Platinum and Palladium Catalysts Encapsulated in Mesoporous Bakelites

Syntheses are reported for catalysts derived from platinum and palladium nanoparticles supported on a mesoporous phenol formaldehyde polymer modified by an ionic liquid. These catalysts are used for the hydrogenation of unsaturated compounds, specifically, acyclic and cyclic isoprenoids: isoprene, 2,5 – dimethyl–2,4–hexadiene, limonene, α –terpinene, γ –terpinene, as well as phenylacetylene, transstilbene, and 1,4–diphenyl–1,3–butadiene. High activity was found for these catalysts in hydrogenation reactions. The palladium catalysts were more active than their platinum analogs. The products of complete hydrogenation predominate in the hydrogenation of isoprenoids on the palladium catalysts, while monoene products predominate in the reactions on platinum catalysts.

CuNi Nanoparticles Assembled on Graphene for Catalytic Methanolysis of Ammonia Borane and Hydrogenation of Nitro/Nitrile Compounds

We report a solution-phase synthesis of 16 nm CuNi nanoparticles (NPs) with the Cu/Ni composition control. These NPs are assembled on graphene (G) and show Cu/Ni composition-dependent catalysis for methanolysis of ammonia borane (AB) and hydrogenation of aromatic nitro (nitrile) compounds to primary amines in methanol at room temperature. Among five different CuNi NPs studied, the G-Cu36Ni64 NPs are the best catalyst for both AB methanolysis (turnover frequency (TOF) of 49.1 molH2 molCuNi–1 min–1 and an activation energy (Ea) of 24.4 kJ/mol) and hydrogenation reactions (conversion yield of >97%). The G-CuNi compound represents a unique noble-metal-free catalyst for hydrogenation reactions in a green environment without using pure hydrogen.

A comparative study of the performance of Pt/MgF2, Ir/MgF2 and Ru/MgF2 catalysts in hydrogenation reactions

This paper reports results of a comparative study of the structure and activity of MgF2-supported metal (Me) catalysts containing 1wt.% of platinum, iridium or ruthenium. Their activities for hydrogenation of toluene and selective hydrogenation of ortho-chloronitrobenzene to ortho-chloroaniline were compared with the hydrogenation performance of metal catalysts prepared by impregnation of a alumina which is one of the most widely used supports. The catalysts were characterized by using low-temperature nitrogen adsorption, TPR-H2 and H2-chemisorption techniques. The nature of metal and support appeared to have a clear influence on metallic phase dispersion and it was reflected by the activity of Me/MgF2 catalysts. The application of magnesium fluoride as a support has enabled to obtain catalysts showing high activities for hydrogenation of toluene at 323–498K and selective hydrogenation of ortho-chloronitrobenzene (o-CNB) to ortho-chloroaniline (o-CAN) in the liquid-phase at 353K under hydrogen pressure of 4MPa. From among the catalysts studied, the highest activity for the both aforementioned reactions has been found in the case of MgF2-supported platinum catalyst and the highest selectivity (100%) in that of ruthenium-containing catalyst. The activity of magnesium fluoride-supported catalysts was several times higher than that of alumina-supported ones.

Mesoporous Microcapsules through d-Glucose Promoted Hydrothermal Self-Assembly of Colloidal Silica: Reusable Catalytic Containers for Palladium Catalyzed Hydrogenation Reactions

A facile methodology is reported to fabricate hierarchically ordered silica nanoassembled microcapsules (SiO2 NACs) with tailored mesopores by combining polymerization of d-glucose with self-assembly of colloidal silica nanoparticles (SiO2 NPs). This controlled self-assembly of SiO2 NPs during a hydrothermal process enables the formation of core–shell (organic/inorganic) hybrid microspheres of carbon and SiO2 NPs. After removal of carbon, spherical hollow SiO2 NACs are formed having mesopores and their surface area was observed as 248 m2/g. The synthesized mesoporous SiO2 NACs can be effectively used to encapsulate palladium nanoparticles (Pd NPs) to act as a heterogeneous catalyst in hydrogenation reactions. The position of Pd NPs in SiO2 NACs (either inside the nanopores or throughout the wall of the capsules) can be dictated by the method of encapsulation which can impart selectivity in hydrogenation of various nitroaromatic compounds, alkyne, and alkenes. The advantages of our catalytic system are greener synthesis of catalyst, that lower Pd content (0.3 mol %) was utilized for the catalytic hydrogenation reaction, heterogeneous nature and reusability.

Palladium Nanoparticle Loaded Bifunctional Silica Hybrid Material: Preparation and Applications as Catalyst in Hydrogenation Reactions.

Bifunctional mesoporous silica was prepared by co-condensation of tetraethyl orthosilicate (TEOS) with functionalized organosilanes containing azides or alkoxyamines. Orthogonal functional groups at the particles were selectively addressed in subsequent chemical modifications through "click"-chemistry ("click to ligand" strategy) and radical nitroxide exchange. Palladation with PdCl2 delivered Pd nanoparticle-loaded silica material bearing sulfoxides and additional aminoamides as stabilizing ligands by means of in situ reduction of the PdII -salt. These functional particles were successfully applied to the hydrogenation of alkynes and alkenes. Aldehyde hydrodeoxygenation and benzyl ether cleavage were achieved with these hybrid catalysts under mild conditions. Particles were analyzed by IR, TEM/STEM, EDX, and solid-state NMR spectroscopy.

Effect of magnetic field on CO2 conversion over Cu-ZnO/ZrO2 catalyst in hydrogenation reaction

Based on green and sustainable innovation with efficient utilization concepts for enhancement of catalyst performance and energy conservation, an external magnetic field has been applied in CO2 hydrogenation reaction in order to improve catalytic activity and reduce the energy consumption. In this research, the performances of Cu-ZnO/ZrO2 catalyst under magnetic field with different magnetic field intensities (0, 20.8, and 27.7mT) and orientations (north-to-south (N-S) and south-to-north (S-N) directions) in CO2 hydrogenation were investigated. Cu-ZnO/ZrO2 catalysts operated under magnetic field gave higher CO2 conversions, compared to that of without magnetic field at all reaction temperatures. The highest CO2 conversions were obtained under the magnetic field condition at 20.8mT in S-N direction which was 1.8–3.0 times higher than that of without magnetic field. Accordingly, the operating temperatures were significantly lower than those of without magnetic field at the same reaction rate. This outstanding performance could be attributed to the fact that the external magnetic field facilitated adsorption of CO2 reactant gas molecules over the surface of magnetized catalysts. Accordingly, the challenge in application of magnetic field in CO2 hydrogenation process help reduce CO2 emission into the atmosphere compared to the convention reactor, and therefore led to the carbon-neutral CO2 conversion process.

Negatively Charged N-Heterocyclic Carbene-Stabilized Pd and Au Nanoparticles and Efficient Catalysis in Water

Herein we describe the synthesis of negatively charged N-heterocyclic carbene (NHC)-functionalized palladium and gold nanoparticles (NPs), which are stable in water for over 3 months. The formation of these NHC–NPs proceeds via an efficient ligand exchange procedure. This method was successfully applied to different negatively charged NHCs bearing sulfonate and carboxylate groups. The obtained PdNPs were investigated as catalysts in hydrogenation reactions and showed high catalytic activity (TON up to 2500 and TOF up to 2000 h–1).

Synthesis, Solid‐State NMR Characterization, and Application for Hydrogenation Reactions of a Novel Wilkinson’s‐Type Immobilized Catalyst

Silica nanoparticles (SiNPs) were chosen as a solid support material for the immobilization of a new Wilkinson's-type catalyst. In a first step, polymer molecules (poly(triphenylphosphine)ethylene (PTPPE); 4-diphenylphosphine styrene as monomer) were grafted onto the silica nanoparticles by surface-initiated photoinferter-mediated polymerization (SI-PIMP). The catalyst was then created by binding rhodium (Rh) to the polymer side chains, with RhCl3⋅x H2O as a precursor. The triphenylphosphine units and rhodium as Rh(I) provide an environment to form Wilkinson's catalyst-like structures. Employing multinuclear ((31)P, (29)Si, and (13)C) solid-state NMR spectroscopy (SSNMR), the structure of the catalyst bound to the polymer and the intermediates of the grafting reaction have been characterized. Finally, first applications of this catalyst in hydrogenation reactions employing para-enriched hydrogen gas (PHIP experiments) and an assessment of its leaching properties are presented.

PVP-Stabilized Palladium Nanoparticles in Silica as Effective Catalysts for Hydrogenation Reactions

Palladium nanoparticles stabilized by poly (N-vinyl-2-pyrrolidone) (PVP) can be synthesized by corresponding Pd(acac)2(acac = acetylacetonate) as precursor in methanol at 80°C for 2 h followed by reduction with NaBH4and immobilized onto SiO2prepared by sol-gel process under acidic conditions (HF or HCl). The PVP/Pd molar ratio is set to 6. The effect of the sol-gel catalyst on the silica morphology and texture and on Pd(0) content was investigated. The catalysts prepared (ca.2% Pd(0)/SiO2/HF andca.0,3% Pd(0)/SiO2/HCl) were characterized by TEM, FAAS, and SEM-EDS. Palladium nanoparticles supported in silica with a size 6.6 ± 1.4 nm were obtained. The catalytic activity was tested in hydrogenation of alkenes.