Selective Hydrogenation Research Articles

Optimization of bi-dispersed porous catalysts for methane super dry reforming via a particle-resolved simulation

Methane super dry reforming (MSDR) is a promising technology for sustainable hydrogen production and greenhouse gas utilization. However, its industrial application is hindered by high energy demand and catalyst deactivation due to carbon deposition. This study aims to optimize bi-dispersed porous catalysts for MSDR through particle-resolved simulation, focusing on the effects of micropore diameter, macropore fraction, and total porosity. A mathematical model incorporating continuity, momentum, species transport, and energy equations was established to simulate the performance of the catalysts. Hierarchical pore structures significantly enhance methane and carbon dioxide conversion rates, which reach 85% and 80% under optimized catalyst conditions, respectively. This improvement leads to increased hydrogen yield and selectivity, while simultaneously reducing carbon deposition. Our study identifies optimal macropore fractions (0.4) and micropore diameters (2 nm) that effectively balance diffusion and reaction kinetics, thereby maximizing catalyst performance. Tailored hierarchical designs of bi-dispersed catalysts are crucial for advancing MSDR technology and have great potential for industrial-scale hydrogen production.

Surface engineering of Pt nanocatalysts with transition metal oleates for selective catalysis: a case study on the hydrogenation of α,β-unsaturated aldehydes.

Selective and active catalysts enable effective use of feedstocks, reduced energy consumption and waste generation. Tuning the electronic structure of heterogeneous metal nanocatalysts via their surface modifications is a promising strategy to design highly selective and active catalysts for the synthesis of harder to make and more cost-efficient products. We introduce transition metal oleates as a new class of ligands to engineer the catalytically active and very selective surface in organic solvents. Using citral hydrogenation and 5 nm Pt NPs as a model reaction and model catalytic system, respectively, we show that surface engineering of Pt nanocatalysts with metal oleates allows synthesis of desired partially hydrogenated product (geraniol) with ∼90% conversion with selectivity over 93%. We demonstrate that the selective synthesis of the unsaturated alcohols catalyzed by Pt NPs modified by adsorption of the transition metal salts cannot be explained by the widely accepted mechanism of preferred coordination of CO groups by Lewis acids (e.g. partially oxidized transition surface metals). Our results indicate that CO groups prefer to bind to negatively charged surfaces. We propose the explanation on how the adsorption of transition metal oleates can result in the increased electron density at the surface of Pt nanoparticles. Our study not only provides reliable solutions to selective hydrogenation but opens a new possibility of using metal oleates for the electronic ligand effect.

Gallium‐Based Eutectic Alloys as Liquid Electron Donors to Ruthenium Single‐Atom Catalysts for Selective Hydrogenation of Vanillin

Gallium‐Based Eutectic Alloys as Liquid Electron Donors to Ruthenium Single‐Atom Catalysts for Selective Hydrogenation of Vanillin

Gallium-Based Eutectic Alloys as Liquid Electron Donors to Ruthenium Single-Atom Catalysts for Selective Hydrogenation of Vanillin.

Tuning the catalytic pathways of atomically dispersed single-atom catalysts (SAC) has emerged as an effective strategy to optimize their overall catalytic activity. Herein, we present Ru1@m-tube, a hollow carbon nitride-supported Ru SAC, coated with eutectic galinstan (GaInSn), as a model catalyst, we demonstrate a performance inversion in vanillin conversion. Vanillin, as a biomass-derived compound with industrial relevance, presents challenges in catalytic hydrogenation, making it an ideal model reaction to test and compare the catalyst's selectivity and efficiency. The as-obtained Ru1@m-tube(GaInSn) achieved nearly 100% vanillin conversion within 5 hours and exhibited an impressive 93.8% selectivity for vanillyl alcohol . Electron spillover from gallium-based eutectic alloys to highly diluted ruthenium sites enhances the desorption of vanillyl alcohol, resulting in an exceptional performance shift between hydrogenation and hydrodeoxygenation. Our findings not only offer a novel approach for modulating SAC performance via liquid-metal interfaces but also expand the understanding of promoter screening for various challenging reactions.

Mimicking Real Catalysts: Model Stepped Nickel Surfaces in Furfural Catalysis─Insights into Adsorption, Reactivity, and Defect-Driven Conversion Pathways.

The catalytic conversion of furanic compounds into renewable chemicals is essential for sustainable manufacturing. Here, we report a unique self-hydrogenation pathway of furfural to 2-methylfuran on Ni(119) surface, showing how steps and nickel carbides govern reaction selectivity. Thermal desorption and spectroscopic measurements reveal that furfural undergoes decarbonylation to furan on terraces, while step sites act as "hydrogen transfer pumps", abstracting hydrogen from furfural and facilitating its diffusion to terrace-bound molecules, thereby promoting selective hydrogenation to 2-methylfuran. Moreover, the surface-bound hydrogen enhances hydrogenolysis, with product selectivity closely connected to hydrogen concentration. DFT calculations show a preference for the top step edges, where strong bonding and electron redistribution stabilize intermediates and promote catalytic transformations. We further demonstrate how these insights provide a framework for designing advanced catalysts through surface structure optimization. By linking model catalysts with real-world applications, this approach enables the development of efficient and selective catalysts tailored for biomass conversion.

Selective Asymmetric Hydrogenation of Waste Polyethylene Terephthalate via Controlled Sorption through Precisely Tuned Moderate Acid Sites.

The partial hydrogenation of waste polyethylene terephthalate (PET) offers a great opportunity to produce valuable chemicals, yet achieving precise catalytic control remains challenging. Herein, for the first time, we realized one-pot selective hydrogenation of waste PET to p-toluic acid (p-TA) with a record-high yield of 53.4%, alongside a 36.4% yield of p-xylene (PX), using a specially designed PtW/MCM-48 catalyst. Mechanistic investigations revealed that the exceptional catalytic performance arises from synergistic interaction between Pt nanoparticles and WOx species. Low-valent WOx enhances Pt dispersion, while Pt stabilizes WOx as low-polymerized polytungstates. The moderate acidity of PtW1.5/MCM-48 ensures controlled desorption of p-TA, preventing overhydrogenation to PX. The catalyst demonstrated robust performance with real-world PET waste. Life cycle assessment and technical and economic evaluation further highlight its practical feasibility. This study establishes a sustainable pathway for PET chemical upcycling and provides a framework for designing advanced catalysts for selective hydrogenation reactions, addressing critical challenges in circular chemistry and plastic waste management.

A d-electron Deficient Pd Trimer for Exceptional Pyridine Hydrogenation Activity and Selectivity.

The selective hydrogenation of pyridines containing reducible groups such as 2-phenylpyridine typically has low yields due to strong nitrogen coordination with the metal as well as non-selective and over-hydrogenation. We report the synthesis of a novel Pd trimer catalyst through confined growth on an ordered mesoporous carrier, characterized by a 0.42 d-electron deficiency to address this challenge. This catalyst achieved a nearly complete conversion of 2-phenylpyridine and selectivity to 2-phenylpiperidine, maintaining its performance across 8 batch cycles and continuous flow in the liquid phase for 800 h with negligible loss of activity or selectivity. We discuss the roles of active sites, including Pd d charge and ensemble structure, in relation to activation entropy, a Hammett study, and the adsorption configuration of the reactant. The exceptional 2-phenylpyridine hydrogenation activity and selectivity are attributed to the adsorption constraint of the pyridyl ring and the stabilization of the negatively charged transition state in the rate-determining step produced by d-electron deficient Pd trimer.

High-Performance Piezoelectric Micro Diaphragm Hydrogen Sensor.

Highly sensitive, selective, and compact hydrogen (H2) sensors for safety and process monitoring are needed due to the growing adoption of H2 as a clean energy carrier. Current resonant frequency-based H2 sensors face a critical challenge in simultaneously achieving high sensitivity, low operating frequency, and miniaturization while maintaining a high figure of merit (FOM). This study addresses these challenges by introducing a novel piezoelectric micro diagram (PMD) H2 sensor that achieves an unprecedented FOM exceeding 104. The sensor uniquely integrates a PMD resonator with a palladium (Pd) sensing layer, operating on a stress-based mechanism distinct from traditional mass-loading principles. Despite a low operating frequency of 150 kHz, the sensor demonstrates a remarkable sensitivity of 18.5 kHz/% H2. Comprehensive characterization also reveals a minimal cross-sensitivity to humidity and common gases and a compact form factor (600 μm lateral length) suitable for IC integration. The sensor's performance was systematically evaluated across various Pd thicknesses (40-125 nm) and piezoelectric stack covering ratios (50% and 70%), revealing a trade-off between sensitivity and response time. This PMD H2 sensor represents a significant advancement in resonant frequency-based H2 sensing, offering superior sensitivity, compact size, and robust performance for diverse applications in H2 detection and monitoring.

Radical Chemistry of Tetrazenes: Access to Polymers with Pristine Tetrazenyl Chain Ends and Depolymerization Applications.

We report the first radical reaction of tetrazenes -i. e. functions with four consecutive nitrogen atoms with a linear N-N=N-N chain- that retains the characteristic 4N pattern. Selective hydrogen atom transfer (HAT) in the α-position of the 4N chain enables the free radical polymerization of various polar and non-polar monomers. The tetrazene units play a dual role. Its decomposition generates aminyl radicals that can undergo HAT and lead to initiating C-centered radicals. Contrary to what was previously thought the aminyl radicals never add to the monomers. The polymers obtained feature tetrazene chain ends, which can be harnessed as macro-initiators to further grow the polymer chains. Heating of the former above the ceiling temperature leads to cleavage of the tetrazene function, which enables depolymerization by unzipping of polymethyl methacrylate (PMMA) and polystyrene (PS).

Tailoring Atomically Precise Gold Nanoclusters for Boosting Selective Hydrogenation of Nitrostyrene with H2.

Hydrogenation reactions represent some of the most extensively studied topics within the field of catalysis. A novel alkynyl and phosphine coprotected [Au34(PhC≡C)14(Ph3P)6](SO3CF3)2(1) nanocluster has been synthesized, and its structure was determined by single crystal X-ray diffraction (SCXRD). Density functional theory calculation shows that 1 features an 18-electron superatomic molecule character with a configuration of (1σ)2(1n)2(1π)2(2σ)2(1σ*)2(3σ)2(2n)2(3n)2(1π*),2 which is significantly different from previously reported 18-electron metal nanoclusters. In comparison with some gold nanoclusters with similar composition or size but different ligands or surface coordination structures, except for the ligand effect (different kinds of ligands), the surface coordination structure involving the Au(I) sites derived from the PhC≡C-Au-C≡CPh monomeric staple motif and the steric hindrance of PhC≡C and Ph3P on the surface of 1, and the special electronic structure play a critical role in ensuring the enhanced catalytic performance of 1/TiO2 toward the chemoselective hydrogenation of 4-nitrostyrene with H2. The turnover frequency (TOF) of 1322.5 h-1 and the turnover number (TON) of 23500 represent the highest values observed among the gold nanocluster-based catalysts toward the same reaction. It presents an example of tailoring the surface coordination structure to modulate the catalytic performance, and offers valuable insights for the rational design and synthesis of catalysts to trade off the catalytic activity and selectivity at the atomic level.

The Synthesis of Hydroquinolines from Nitroaldehydes and Ketones by Hydrogenation Sequences and Condensations.

Catalytic reaction discovery or methodology development is preferably performed with homogeneous catalysts, but heterogeneous catalysts allow the design of complex multistep syntheses based on their reusability. We introduce here the catalytic synthesis of hydroquinolines starting from nitroaldehydes, ketones and hydrogen. The reaction is complex and proceeds via multiple selective hydrogenation and condensation steps. The nitroaldehyde is selectively hydrogenated forming an aminoaldehyde, followed by a base-catalyzed Friedländer synthesis and selective quinoline hydrogenation. The starting materials are inexpensive, simple regarding their structure and diversely available, and the hydroquinoline motif is part of numerous biologically active compounds. A nanostructured earth-abundant metal catalyst mediates our reaction most efficiently.

One-pot synthesis of E-chalcones using a multifunctional catalyst comprised of ruthenium nanoparticles and palladium N-heterocyclic carbene complexes immobilized on silica.

The integrated one-pot synthesis of valuable E-chalcones from aryl iodides, phenylacetylenes, CO and H2 is achieved using a single catalyst material. The multifunctional catalytic system is composed of a silica support on which ruthenium nanoparticles and covalently functionalized palladium N-heterocyclic carbene (NHC) complexes are jointly assembled. The resulting Ru@SiO2-[Pd-NHC] catalyst was characterized by a variety of techniques including N2 physisorption, solid-state nuclear magnetic resonance, electron microscopy, and X-ray photoelectron spectroscopy to collect information on its textural, structural, morphological, and electronic properties. Ru@SiO2-[Pd-NHC] was found to be active and selective for the one-pot synthesis of a wide variety of E-chalcones, valuable products with widespread applications in the fine chemical, agrochemical, and pharmaceutical industries. The heterogenized Pd-NHC complex catalyzed the carbonylative Sonogashira coupling step, while CO-covered Ru NPs were found to be responsible for the highly selective hydrogenation of the ynones intermediates to E-chalcones. This study outlines the potential of hybrid multifunctional catalytic systems combining molecular and nanoparticle sites to open up new and more sustainable complex reaction sequences toward valuable compounds.

Pd Ensemble Sites Tuned Local Environment of Cu Catalysts for Matching Propyne Semi‐Hydrogenation

AbstractTailoring local environments of active sites to match targeted configuration of key species is significant for controlling reaction pathways in selective hydrogenations. Herein, differently typed Pd sites are introduced onto Cu catalysts to tune the local environment of Cu sites for controlling the configuration of semi‐hydrogenation pathway of propyne hydrogenation used in production of polymer‐grade propylene. Detailed structure characterizations demonstrate the controllable construction of Pd single‐atom and Pd ensemble sites modified Cu surfaces and PdCu alloy via fine tuning the Pd/Cu ratios. Catalytic tests, kinetics analysis, and temperature‐programmed experiments demonstrate that the presence of Pd ensemble sites on Cu surface directly catalyzes the hydrogenation of propyne that occurs on the Cu sites in other cases, and enables a facile activation for hydrogen and simultaneously promotes the desorption of propylene against its hydrogenation. Accordingly, the selectivity to target propylene is up to 95.3% at the full conversion of propyne on the corresponding Pd0.1Cu catalyst. In contrast, the C─C coupling pathway is quite facile on the Cu surface tuned by single‐atom Pd sites, which is similar to that on the pristine Cu sites on the Cu catalyst, and the well‐defined Pd─Cu coordination on PdCu alloy catalyst leads to facile over‐hydrogenation process.

Zr‐Based MOFs Catalyzed Selective Transfer Hydrogenation of Nitrobenzaldehydes: the Harmony of Pore Size and Acidity

Noble metal free catalysts are urgently needed for catalytic transfer hydrogenation (CTH). Zr‐based metal‐organic frameworks (MOFs) show excellent catalytic activity towards the transformation of aldehydes to alcohols via the CTH route. Among the tested Zr‐MOFs with different pore size and acidic sites, MOF‐808 shows the best catalytic activity, selectivity, and stability for synthesizing nitrobenzyl alcohols due to the harmony of pore size and acidity, which completes the reaction in a short period under mild conditions.

Alumina Supported Iron Catalysts for Selective Acetylene Hydrogenation Under Industrial Front‐End Conditions

AbstractThe removal of acetylene traces from ethylene streams coming from the steamcracker is carried out in the industry on an annual scale of several million tons using Pd‐Ag/Al2O3 catalysts. The substitution of palladium containing catalysts with more abundant, cheap, and nontoxic materials is a first crucial step toward a more sustainable chemical industry. As iron is one of the most abundant metals and can be mined in almost all regions worldwide, it is an ideal catalyst material. In this work, we present the development of α‐alumina supported iron catalysts with 1, 5, and 10 wt% iron loading and their application in the selective acetylene hydrogenation under industrially applied front‐end conditions. The catalysts were prepared via simple incipient wetness‐impregnation and were analyzed via XRD, XRF, TPR, TEM, and N2‐physisorption. The catalysts were subsequently calcined, reduced, and tested in the selective acetylene hydrogenation. After an activation phase, the catalysts show excellent activity and selectivity in the acetylene hydrogenation at 90 °C without significant ethylene hydrogenation. The excellent catalytic activity underline the great potential of iron based catalysts as an alternative to conventional Pd‐containing materials.

Polystyrene-Br End-Group Modification via Electrolysis: Adjusting Hydrogenation vs Coupling Selectivity.

Atom transfer radical polymerization (ATRP) enables the precise synthesis of polymers with well-defined architectures, controlled molecular weights, and low dispersity. However, the halogen end-groups inherent to ATRP polymers can pose challenges due to their chemical reactivity and thermal instability. To address these issues, various strategies, including chemical and photochemical methods, have been developed for chain-end modification. This study introduces an electrochemical approach to selectively reduce halogen end-groups in ATRP polymers. Using glassy carbon (GC) and silver electrodes, the reductive cleavage of C-Br in bromine-capped polystyrene was investigated. Cyclic voltammetry revealed that polystyrene-bromide undergoes electron transfer accompanied by the concerted removal of the C-Br functionality. The Ag electrode facilitated electrocatalysis with enhanced activity. Controlled-potential electrolysis demonstrated that reaction conditions, particularly the choice of proton donors, significantly influence product distribution, enabling selective hydrogenation or dimerization of polystyrene-bromide chain ends. This work advances the understanding of electrochemical strategies for tailoring polymer end-group functionality.

Hydrogen Storage in Zeolites: A Mini Review of Structural and Chemical Influences on Adsorption Performance

Review Hydrogen Storage in Zeolites: A Mini Review of Structural and Chemical Influences on Adsorption Performance Baran Taşğın 1,*, Jiří Ryšavý 1, Thangavel Sangeetha 2,3, and Wei-Mon Yan 2,3 1 Energy Research Centre, Centre for Energy and Environmental Technologies, VSB—Technical University of Ostrava, 17. listopadu 2172/15, 708 00 Ostrava, Czech Republic 2 Department of Energy and Refrigerating, Air-Conditioning Engineering, National Taipei University of Technology, Taipei 10608, Taiwan 3 Research Center of Energy Conservation for New Generation of Residential, Commercial, and Industrial Sectors, National Taipei University of Technology, Taipei 10608, Taiwan * Correspondence: baran.tasgin.st@vsb.cz Received: 9 January 2025; Revised: 20 February 2025; Accepted: 22 February 2025; Published: 5 March 2025 Abstract: Hydrogen is increasingly being recognized as a clean energy carrier that is vital for decarbonizing industries and integrating renewable energy sources. Efficient hydrogen storage is critical for its widespread adoption and economic viability. Among promising solutions, zeolites have gained attention because of their unique microporous structures, high surface areas, and modifiable chemical properties. These characteristics enable zeolites to effectively adsorb hydrogen molecules, making them suitable for sustainable energy storage and transportation. The exceptional physicochemical properties of zeolites, such as ion exchange and adsorption capacities, allow tailored modifications to enhance their hydrogen storage performance. Techniques such as surface functionalization with amines and ion exchange with specific cations significantly improve adsorption capacity and efficiency. For instance, amine modifications introduce electrostatic interactions, whereas ion exchange optimizes the pore structure and increases the surface charge. Recent studies have highlighted the potential of silver ion-exchanged zeolites for selective hydrogen isotope separation, demonstrating the versatility of these materials. With advancements in zeolite research, the development of scalable, cost-effective, and high-capacity hydrogen storage systems has become increasingly feasible. These innovations position zeolites as key contributors to clean energy transition, supporting the role of hydrogen as a cornerstone of sustainable energy infrastructure.

Studies on Cobalt Nano Particles Supported on Nitrogen-Doped Carbon Catalysts for Selective Hydrogenation of Biomass Derived Furfural

Studies on Cobalt Nano Particles Supported on Nitrogen-Doped Carbon Catalysts for Selective Hydrogenation of Biomass Derived Furfural

Pd Ensemble Sites Tuned Local Environment of Cu Catalysts for Matching Propyne Semi-Hydrogenation.

Tailoring local environments of active sites to match targeted configuration of key species is significant for controlling reaction pathways in selective hydrogenations. Herein, differently typed Pd sites are introduced onto Cu catalysts to tune the local environment of Cu sites for controlling the configuration of semi-hydrogenation pathway of propyne hydrogenation used in production of polymer-grade propylene. Detailed structure characterizations demonstrate the controllable construction of Pd single-atom and Pd ensemble sites modified Cu surfaces and PdCu alloy via fine tuning the Pd/Cu ratios. Catalytic tests, kinetics analysis, and temperature-programmed experiments demonstrate that the presence of Pd ensemble sites on Cu surface directly catalyzes the hydrogenation of propyne that occurs on the Cu sites in other cases, and enables a facile activation for hydrogen and simultaneously promotes the desorption of propylene against its hydrogenation. Accordingly, the selectivity to target propylene is up to 95.3% at the full conversion of propyne on the corresponding Pd0.1Cu catalyst. In contrast, the C-C coupling pathway is quite facile on the Cu surface tuned by single-atom Pd sites, which is similar to that on the pristine Cu sites on the Cu catalyst, and the well-defined Pd-Cu coordination on PdCu alloy catalyst leads to facile over-hydrogenation process.

The influence of reaction conditions on selective acetylene hydrogenation over sol immobilisation prepared AgPd/Al2O3 catalysts

Electric plasma activation of methane opens up the possibility to produce ethene, an important platform chemical in industry, by using sustainable resources like biogas or hydrogenated carbon dioxide and electricity from renewable energies. The ethene stream of such pyrolysis plants contains, however, much higher concentrations of acetylene (≥ 15 vol.%) compared to ethene from conventional steam cracking of naphtha (< 2 vol.%). In this study, silver‐palladium catalysts in various compositions supported on alumina were synthesized via a sol‐immobilisation technique and investigated in the selective gas‐phase hydrogenation of equally concentrated acetylene‐ethene mixtures under industrially relevant pressures. A molar Pd concentration of around 10 % in the PdAg alloyed nanoparticles was identified as the optimum composition for simultaneous high activity and ethene selectivity under catalysis conditions. Higher temperatures seem to be crucial for the stability of the catalysts on‐stream most likely via increased desorption of active site blocking and high‐boiling oligomers from acetylene. The best performing Pd10Ag90 displayed an ethene, ethane and C4+ selectivity of 65, 4 and 14% respectively, at 175 °C while being active for more than 200 minutes. The performance of the catalyst was compared with catalysts synthesized via a mechanochemical and a conventional wet‐impregnation procedure.