Selective Hydrogenation Reactions Research Articles

Recent advance in selective hydrogenation reaction catalyzed by biomass-derived non-noble metal nanocomposites

The green and sustainable synthesis of fine chemicals and pharmaceuticals urgently demands a new generation of efficient and robust catalysts in diverse organic transformations. Owing to their unique features of ready availability, natural abundance and renewability, environmental friendliness, and low-cost, the development of catalytically active materials derived from biomass has attracted extensive attention in the field of organic synthesis over the past few years. In this review, we summarize major progress in design and preparation of efficient and robust non-noble metal catalysts derived from various biomass feedstocks for green and sustainable selective hydrogenation transformations, with a particular focus on catalytic hydrogenation of nitro compounds, unsaturated CC bonds, quinoline compounds, CO bonds and so on. Finally, the challenges remaining in this research area are discussed and feasible future research directions are proposed.

Modern Trends in the Applications of Perovskites for Selective Organic Transformations

AbstractPerovskites have captivated the interest of contemporary synthetic chemists in both the academic and industrial sector due to their multifarious physicochemical properties like excellent thermal stability, oxygen mobility substitution of A and B cations. These perovskite based mixed metal oxides effectively promote selective organic transformations like selective oxidation reactions, selective hydrogenation reactions, nitro to amine reduction, carbon‐carbon and carbon hetero‐bond forming reactions. Furthermore, these mixed metal oxide perovskites have been investigated for the multi‐component domino reactions for synthesis of valuable organic compounds. Recently, metal halide perovskites have emerged as futuristic materials for the catalytic and photocatalytic selective organic transformations to form valuable organic compounds. The present review mainly addresses the recent developments in the catalytic and photocatalytic applications of perovkites in organic synthesis in the past 10 years.

Surface molecular imprinting over supported metal catalysts for size-dependent selective hydrogenation reactions

Surface molecular imprinting over supported metal catalysts for size-dependent selective hydrogenation reactions

Ir nanoclusters confined within hollow MIL-101(Fe) for selective hydrogenation of α,β-unsaturated aldehyde

Although the selective hydrogenation of α,β-unsaturated aldehyde to unsaturated alcohol (UOL) is an extremely important transformation, it is still a great challenge to achieve high selectivity to UOL due to thermodynamic favoring of the CC hydrogenation over the CO hydrogenation. Herein, we report that iridium nanoclusters (Ir NCs) confined within hollow MIL-101(Fe) expresses satisfied reaction activity (93.9%) and high selectivity (96.2%) for the hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) under 1 bar H2 atmosphere and room temperature. The unique hollow structure of MIL-101(Fe) benefits for the fast transport of reactant, ensuring the comparable reaction activity and better recyclability of [email protected](Fe) than the counterparts which Ir NCs were on the surface of MIL-101(Fe). Furthermore, The X-ray photoelectron spectroscopy data indicates the electropositive Ir NCs, owing to the electron transfer from Ir to MIL-101(Fe), can interact with oxygen lone pairs, and Fourier transform infrared spectrum shows the Lewis acid sites in MIL-101(Fe) can strongly interact with CO bond, which contributes to a high selectivity for COL. This work suggests the considerable potential of synergetic effect between hollow MOFs and metal nanoclusters for selective hydrogenation reactions.

Waste Eggshell with naturally-functionalized sulfonic groups as excellent support for loading Pd and Ag nanoparticles towards enhanced 1,3-butadiene hydrogenation

• Eggshell was used as novel green support in selective 1,3-butadiene hydrogenation. • Pd-Ag/eggshell catalysts demonstrated superior stability. • The sulfonic groups on eggshell altered the Pd nanoparticles electronic properties. • The sulfonic groups result in the weaker adsorption of butenes and 1,3-butadiene. • The eggshell can be used as a natural modified support for hydrogenation. In recent years, high value utilization of waste biomass has been a hot topic in scientific research. Herein, waste eggshell (ES) rich in sulfonic groups was utilized as a natural modified support to load Pd and Ag nanoparticles (NPs), leading to efficient Pd-Ag/ES catalysts for the catalytic hydrogenation of 1,3-butadiene. Through series of characterizations such as SEM, TEM, BET, XPS, and FTIR, it was found that the porous ES not only has hierarchical structures to facilitate the metal dispersion, but also interacts strongly with Pd and Ag NPs via the inherent surface sulfonic groups, which are responsible for the enhanced catalytic performance. The optimized Pd-Ag/ES catalyst exhibited butenes selectivity of 95.8% and 1,3-butadiene conversion of 95% at 45 °C with excellent stability for at least 30 h on-stream. Furthermore, the first-principles density functional theory (DFT) calculation and in situ DRIFTS were performed to explore the plausible mechanism underlying the enhanced catalytic performance due to sulfonic groups. It is suggested that the sulfonic groups can effectively reduce the adsorption energy of butenes and 1,3-butadiene on the surface of Pd NPs which are beneficial to the selectivity of butenes. This work exemplifies that the waste ES with inherent sulfonic groups can be used as excellent support materials for loading active metal nanoparticles for selective hydrogenation reactions. Collectively, we verified that biological waste like eggshell has a great potential in serving as catalyst carrier due to its unique advantages.

Fabrication of Superamphiphilic Carbon Using Lignosulfonate for Enhancing Selective Hydrogenation Reactions in Pickering Emulsions.

Superamphiphilic materials have great potential to enhance the mass transfer between phases in liquid-liquid catalysis due to their special affinities. Constructing superamphiphilic surfaces that possess superhydrophilic and superhydrophobic properties simultaneously has been a tough assignment. So, exploration of simple methods to prepare such materials using renewable and abundant feedstocks is highly desired. Here, we reported an effective strategy to construct superamphiphilic carbon directly from sodium lignosulfonate, which is a renewable resource from paper industry wastes. From the characterization of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) for superamphiphilic carbon, we found that element C was responsible for the hydrophobic nature and the existence of O and S endowed the carbon with hydrophilic characteristics. Further, micro/nanohierarchical pores were found beneficial for the superamphiphilicity of carbon. Meantime, in the selective hydrogenation of styrene, phenylacetylene, and cis-stilbene in liquid-liquid systems, conversion became double using superamphiphilic carbon compared with blank results, and the yields were three times more than those in blank experiments. The reasons were that superamphiphilic carbon induced the formation of Pickering emulsions and enriched the reactants around catalysts, as concluded by the characterization of confocal laser scanning microscopy and relating contrastive experiments. This work revealed a different route to obtain superamphiphilic carbon and provided a diverse perspective to promote Pickering emulsion catalysis by the superamphiphilicity of carbon.

Studying the Selective Methylacetylene Hydrogenation Reaction in Methylacetylene–Propylene Mixtures on Palladium Oxide Nanocatalysts

Studying the Selective Methylacetylene Hydrogenation Reaction in Methylacetylene–Propylene Mixtures on Palladium Oxide Nanocatalysts

A Comparison of Experimental Procedures for the Application of Infrared Spectroscopy to Probe the Surface Morphology of an Alumina-Supported Palladium Catalyst

Structure/function relationships in heterogeneous catalysis play an important role in catalyst design strategies. The combination of chemisorption of suitable probe molecules alongside application of infrared spectroscopy is an established technique for providing information on the metal crystallite morphology of supported metal catalysts. Following a review of key literature on this topic, a variety of experimental arrangements that may be adopted for this task are examined. Specifically, the adsorption of CO over a 5wt% Pd/Al2O3 catalyst is investigated using transmission and diffuse reflectance sampling options and two research grade spectrometers. Although comparable spectra are obtained on all the platforms examined, differences are noted. In particular, temperature-programmed IR spectroscopy on one platform enables resolution of two features assigned to linear CO bound to the Pd particles. The relevance of this sub-division of terminal sites with respect to selective hydrogenation reactions is briefly considered.

Versatile Hollow ZSM-5 Nanoreactors Loaded with Tailorable Metal Catalysts for Selective Hydrogenation Reactions.

Zeolites are one of the most commonly used materials in the chemical industry, acting as catalysts or catalyst supports in different applications. Recently, the synthesis and functionalization of hollow zeolites have attracted many research interests, owing to the unique advantages of their hollow morphology. In the development of more sustainable processes, the hollow zeolites are often endowed with additional stability, selectivity, and activity. Herein, we present a stepwise synthetic protocol to prepare a range of complex hollow ZSM-5 catalysts with catalytic nanoparticles. Solid ZSM-5 crystals were first synthesized from Stöber silica spheres. This solid ZSM-5 sample was then loaded with transition metals via the impregnation method. A subsequent hollowing process was carried out in hydrothermal conditions in which hollow ZSM-5 crystals with confined transition metals inside were synthesized. More specifically, after the encapsulation of transition metals inside hollow ZSM-5, two different approaches have been further devised to allow the deposition of noble metals into the interior cavities or onto the exterior surfaces of the hollow ZSM-5. The deposition of Pt on the exterior surface was carried out by mixing the hollow ZSM-5 sample with presynthesized Pt nanoparticles. Loading of Pd in the interior was achieved by the galvanic replacement reaction between the Pd ions and embedded transition metals inside the hollow ZSM-5 sample. The catalytic performance of these reactor-like nanocatalysts has been evaluated with hydrogenation reactions in both liquid and gas phases, and their compositional and structural merits have been illustrated. For the hollow ZSM-5 sample with Pd loaded inside, liquid-phase selective hydrogenation of styrene over 4-vinylbiphenyl has been achieved with the ZSM-5 shell acting as a molecular sieve. The deposition of Pt on the exterior has improved the C2-C4 product yield when tested for the gas-phase CO2 hydrogenation reaction.

Metal Nanoparticles Immobilized on Molecularly Modified Surfaces: Versatile Catalytic Systems for Controlled Hydrogenation and Hydrogenolysis.

ConspectusThe synthesis and use of supported metal nanoparticle catalysts have a long-standing tradition in catalysis, typically associated with the field of heterogeneous catalysis. More recently, the development and understanding of catalytic systems composed of metal nanoparticles (NPs) that are synthesized from organometallic precursors on molecularly modified surfaces (MMSs) have opened a conceptually new approach to the design of multifunctional catalysts (NPs@MMS). These complex yet fascinating materials bridge molecular (“homogeneous”) and material (“heterogeneous”) approaches to catalysis and provide access to catalytic systems with tailor-made reactivity through judicious combinations of supports, molecular modifiers, and nanoparticle precursors. A particularly promising field of application is the controlled activation and transfer of dihydrogen, enabling highly selective hydrogenation and hydrogenolysis reactions as relevant for the conversion of biogenic feedstocks and platform chemicals as well as for novel synthetic pathways to fine chemicals and even pharmaceuticals. Consequently, the topic offers an emerging field for interdisciplinary research activities involving organometallic chemists, material scientists, synthetic organic chemists, and catalysis experts.This Account will provide a brief overview of the historical background and cover examples from the most recent developments in the field. A coherent account on the methodological and experimental basis will be given from the long-standing experience in our laboratories. MMSs are widely accessible via chemisorption and physisorption methods for the generation of stable molecular environments on solid surfaces, whereby a special emphasis is given here to ionic liquid-type molecules as modifiers (supported ionic liquid phases, SILPs) and silica as support material. Metal nanoparticles are synthesized following an organometallic approach, allowing the controlled formation of small and uniformly dispersed monometallic or multimetallic NPs in defined composition. A combination of techniques from molecular and material characterization provides a detailed insight into the structure of the resulting materials across various scales (electron microscopy, solid-state NMR, XPS, XAS, etc.).The molecular functionalities grafted on the silica surface have a pronounced influence on the formation, stabilization, and reactivity of the NPs. The complementary and synergistic fine-tuning of the metal and its molecular environment in NPs@MMSs allow in particular the control of the activation of hydrogen and its transfer to substrates. Monometallic (Ru, Rh, Pd) monofunctional NPs@MMSs possess excellent activities for the hydrogenation of alkenes, alkynes, and arenes for which a nonpolarized (homolytic) activation of H2 is predominant. The incorporation of 3d metals in noble metal NPs to give bimetallic (FeRu, CoRh, etc.) monofunctional NPs@MMSs favors a more polarized H2 activation and thus its transfer to the C=O bond, while at the same time preventing the arrangement of noble metal atoms necessary for ring hydrogenation. The incorporation of reactive functionalities, such as, for example, a −SO3H moiety on NPs@MMSs, results in bifunctional catalysts enabling the heterolytic cleavage corresponding to a formal H–/H+ transfer. Consequently, such catalysts possess excellent deoxygenation activity with strong synergistic effects arising from an intimate contact between the nanoparticles and the molecular functionality.While many more efforts are still required to explore, control, and understand the chemistry of NPs@MMS catalysts fully, the currently available examples already highlight the large potential of this approach for the rational design of multifunctional catalytic systems.

From amorphous to ordered: Structural transformation of Pd nanoclusters in 1-pentyne hydrogenation reactions

Nanostructured palladium catalysts are used industrially for selective alkyne hydrogenation reactions. However, structural changes can lead to a loss of performance. In this study, we show the evolution of the atomic structure of monodispersed Pd nanoclusters undergoing a vapour-phase 1-pentyne hydrogenation reaction. A specific structural transformation, from amorphous to highly symmetrical structures, is observed at the atomic level with aberration-corrected scanning transmission electron microscopy (AC-STEM). This surprising behaviour which occurs concurrently with the alkyne hydrogenation reaction, is clearly size-dependent. The results provide new understanding of the long-term stability of commercial heterogeneous catalysts.

Selective Hydrogenation of Furfural over the Co-Based Catalyst: A Subtle Synergy with Ni and Zn Dopants.

A multimetal doping strategy has aroused extensive attention in promoting a non-noble catalyst for selective hydrogenation reaction. Herein, a multimetallic catalyst (NiCoZn@CN) with excellent catalytic performance for hydrogenation of furfural (FAL) to furfuryl alcohol (FOL) is prepared through a facile, inexpensive, and efficient pyrolysis method. Using H2 as a H donor, extremely high selectivity (>99%) with 100% conversion is attained over the optimal NiCoZn@CN-600 catalyst. The subtle synergy between Co and Ni, Zn dopants, which remarkably promotes the performance of the Co-based catalyst, is revealed. In the NiCoZn@CN system, Co0 is proven to be the main active site, whose content is greatly improved by Ni and Co dopants. Additionally, the Ni dopant could also benefit activation of H2 and the Zn dopant could enhance metal nanoparticle dispersion and the porous structure of the catalyst. In situ FTIR indicates that the vertical adsorption mode of FAL with the Oaldehyde terminal on NiCoZn@CN-600 ensures a selective hydrogenation process. With a N-doped carbon matrix, NiCoZn@CN-600 shows good cycling stability in five times run. NiCoZn@CN-600 is also competent in the catalytic transfer hydrogenation (CTH) of FOL, affording >99% yield with 2-propanol as a H donor. This study opens an avenue toward rational design of multimetallic doping catalysts with high selectivity for challenging reactions in the conversion of biomass-derived compounds.

Pd single-atom monolithic catalyst: Functional 3D structure and unique chemical selectivity in hydrogenation reaction

Regulating the selectivity of catalysts in selective hydrogenation reactions at the atomic level is highly desirable but remains a grand challenge. Here we report a simple and practical strategy to synthesize a monolithic single-atom catalyst (SAC) with isolated Pd atoms supported on bulk nitrogen-doped carbon foams (Pd-SAs/CNF). Moreover, we demonstrate that the single-atom Pd sites with unique electronic structure endow Pd-SAs/CNF with an isolated site effect, leading to excellent activity and selectivity in 4-nitrophenylacetylene semi-hydrogenation reaction. In addition, benefiting from the great integrity and excellent mechanical strength, monolithic Pd-SAs/CNF catalyst is easy to separate from the reaction system for conducting the subsequent recycling. The cyclic test demonstrates the excellent reusability and stability of monolithic Pd-SAs/CNF catalyst. The discovery of isolated site effect provides a new approach to design highly selective catalysts. And the development of monolithic SACs provides new opportunities to advance the practical applications of single-atom catalysts.

Recyclable Transition Metal Catalysis using Bipyridine-Functionalized SBA-15 by Co-condensation of Methallylsilane with TEOS.

Well-defined recyclable Pd- and Rh-bipyridyl group-impregnated SBA-15 catalysts were prepared for C-C bond coupling reaction and selective hydrogenation reactions, respectively. These SBA-15 derived ligands for the catalysts were prepared by direct and indirect co-condensation method using bipyridyl-linked methallylsilane. This indirect method, involving methoxysilane generated from methallylsilane shows higher loading efficiency of transition metal catalysts on SBA-15 than the direct use of methallylsilane.

Ceria-Based Catalysts for Selective Hydrogenation Reactions: A Critical Review

The catalytic behaviour of ceria (cerium (IV) Oxide; CeO2) incorporated with trace metals, metallic particles or mixed support systems has been studied extensively for various heterogeneous reactions. Moreover, unique redox properties and structural defects have made ceria a desirable choice for selective hydrogenation reactions. This paper provides the first review of studies focusing on the performance of ceria in selective catalytic hydrogenation. The review covers the fundamentals, economic benefits, and application of ceria in the aforementioned reaction, highlighting the theoretical basis and importance of non-stoichiometric forms of ceria (CeO2-x). We have contrasted the effect of operational parameters and molecular alterations as documented in the literature, and constructed the mechanistic and kinetic insights on the heterogeneous hydrogenation over ceria. The remarks in this review provide necessary future outlooks, recommendations, and plausaible improvements on the catalytic performance of ceria.

Convenient semihydrogenation of azoarenes to hydrazoarenes using H2.

The high atom-economical and eco-benign nature of hydrogenation reactions make them much more superior to conventional reduction and transfer hydrogenation. Herein, a convenient and highly selective hydrogenation reaction of azoarenes using molecular hydrogen to access diverse hydrazoarenes is reported. The present catalytic method is general and operationally simple, and it operates under exceedingly mild conditions (room temperature and 1 atm of hydrogen pressure). The reusability of catalysts used in this method is also successfully demonstrated.

Selective hydrogenation of acetylene on Cu-Pd intermetallic compounds and Pd atoms substituted Cu(111) surfaces.

The selective hydrogenation of acetylene was studied on the ordered Cu-Pd intermetallic compounds (L10-type CuPd, L12-type Cu3Pd, and L12-type CuPd3) and Pd-modified Cu(111) surfaces through first-principles calculations. The catalytic selectivity and activity of Cu-Pd alloy catalysts are closely related to the crystal structure and composition of Cu-Pd intermetallic compounds and the size of Pd ensembles of Cu-based dilute alloy surface for the selective hydrogenation of acetylene to ethylene. Significantly, we found that the ordered Cu-Pd alloy surface containing isolated Pd atoms (i.e., L12-type Cu3Pd(111) surface) is highly efficient for the selective hydrogenation reaction of C2H2 + H2→ C2H4. The contiguous Pd atom ensembles (Pd dimer and trimer) are catalytically active towards C2H2 + H → C2H3 and C2H3 + H → C2H4 reactions than the single Pd atom on a Pd-decorated Cu(111) surface. However, the small Pd ensembles on Cu(111) present a low chemical activity for H2 dissociation compared with the ordered Cu-Pd intermetallic compounds. Our theoretical results provide a strategy of crystal phase and composition control for enhancing the selectivity and activity of Cu-Pd catalysts towards acetylene selective hydrogenation.

Direct Synthesis of Atomically Dispersed Palladium Atoms Supported on Graphitic Carbon Nitride for Efficient Selective Hydrogenation Reactions.

Heterogeneous catalysts with atomically precise metal sites have enabled unique insight into structure-property relationships in materials science. Herein, we report the construction and selective hydrogenation performance of a single-atom palladium catalyst by confining the palladium atoms into the six-fold N-coordinating cavities of graphitic carbon nitride (g-C3N4) through a facile spatial confinement-reduction approach under mild reducing conditions. Spherical aberration correction electron microscopy and extended X-ray absorption fine structure measurements confirm the presence of atomically dispersed palladium atoms stabilized by the g-C3N4 support. Its exceptional catalytic activity was demonstrated by the hydrogenation of styrene (98% conversion, 1.5 h) and furfural (conversion of 64% and selectivity of 99%, 4 h) and hydrodechlorination of 4-chlorophenol (99% conversion and 99% selectivity, 10 min). This palladium catalyst can be reused at least five times with negligible deterioration of its activity. Importantly, the palladium atoms retained their atomic dispersion following the thermal treatment. Moreover, this synthetic method can be scaled up while retaining similar catalytic activity. Fundamental insights are provided to elucidate how the material's structure significantly impacts the catalytic performance at the atomic scale.

A theoretical investigation of iron-catalyzed selective hydrogenation of nitriles to secondary imines

The mechanism of the transition metal iron complex [(iPr-PNP)Fe(H)Br(CO)] catalyzed reaction of selective hydrogenation of nitriles to secondary imines has been investigated with the M06-2X function. The results indicate that the reaction involves two basic processes: (i) A catalyzed p-bromobenzonitrile to benzaldimine and primary amine transformation; (ii) condensation of benzaldimine with a primary amine to afford secondary imine. The calculated barrier of transition metal-catalyzed condensation reaction of benzaldimine with a primary amine, 30.6 kcal/mol, indicates that the condensation reaction is feasible under experiment conditions. The theoretical results provide a deeper understanding of the mechanism and fully explain the experimental facts.

MODIFIED COBALT CATALYSTS FOR HYDROGENATION OF HYDROCARBONS

This work is devoted to the study of the influence of aluminum oxide content on the activity of cobalt catalysts in the reaction of selective hydrogenation of acetylene to ethylene. Cobalt catalysts modified with aluminum oxide having size between 50 to 500 nm were synthesized. Chemical contents and structure of carrier were investigated. The catalytic activity of 5% Со/clay and 5% Co/SiAl catalysts at acetylene hydrogenation was studied in the temperature range 100-180 ℃, with a ratio of 1:2 of acetylene and hydrogen. The ethylene yield is 87.8% in modifying the cobalt catalyst with aluminum oxide, whereas with the same process parameters, the ethylene yield is 72%. 5% Cobalt catalysts modified with 1.5% aluminum oxides are more active in hydrogenation acetylene process than 5% Со/clay 450 ℃ catalyst.