Hydrogenation Of Acetylene Research Articles

Broadly Applicable Copper(I)-Catalyzed Alkyne Semihydrogenation and Hydrogenation of α,β-Unsaturated Amides Enabled by Bifunctional Iminopyridine Ligands.

A highly active bifunctional catalyst consisting of a copper(I)/N-heterocyclic carbene complex and a basic 2-iminopyridine subunit allows for copper hydride chemistry under low H2 pressure, achieving efficient catalysis reaching 1 bar (balloon pressure). The bifunctional catalyst tolerates a remarkable variety of functional groups in catalytic alkyne semihydrogenations. Furthermore, this catalyst design gives rise to a high reactivity that allows for the catalytic hydrogenation of α,β-unsaturated amides (a substrate class hitherto unreactive in copper hydride catalysis) at a low H2 pressure for the first time. In this manner, late-stage modification and isotope labeling of α,β-unsaturated amides, common subunits in biologically active compounds, can be realized through catalytic hydrogenation using a first-row transition metal catalyst based on abundant copper. Preliminary mechanistic experiments indicate that the bifunctional catalyst operates via an iminopyridine-mediated proximity effect. We hypothesize that the coordination of an alcohol as a proton source on the copper(I) complex facilitates the overall reactions through a rapid proto-decupration step.

Influence of CeO2 crystal facet on acetylene selective hydrogenation over Pd/CeO2 catalysts

Influence of CeO2 crystal facet on acetylene selective hydrogenation over Pd/CeO2 catalysts

Liquid-phase selective hydrogenation of acetylene with the feed composition of front-end process

Liquid-phase selective hydrogenation of acetylene with the feed composition of front-end process

Cost-Optimized Design of Front-End Acetylene Hydrogenation Using Artificial Neural Networks

Cost-Optimized Design of Front-End Acetylene Hydrogenation Using Artificial Neural Networks

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.

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.

Tailoring ultrastable CuNiCs amorphous cluster via entropy engineering for acetylene selective hydrogenation

Tailoring ultrastable CuNiCs amorphous cluster via entropy engineering for acetylene selective hydrogenation

Ruthenium-Catalyzed Transfer Hydrogenation of Alkynes: Access to Alkanes and (E)- or (Z)-Alkenes in Tandem with Pd/Cu Sonogashira Cross-Coupling.

A complete reduction of alkynes using a combination of [RuCl2(p-cymene)]2, DTBM-SEGPHOS, and a paraformaldehyde/water system as the hydrogen source was developed, affording alkanes in 52-99% yields. In addition, the preparation of alkenes from terminal alkynes and aryl iodides by a tandem process of Pd/Cu-catalyzed Sonogashira reaction followed by Ru-catalyzed transfer hydrogenation is reported, affording alkenes in 38-99% yields. This multicatalysis proceeds via three consecutive reactions and can be extended further, as shown by adding an iodine-catalyzed cis-trans alkene isomerization step.

Atomically exposed Pd catalysts covered by boron nitride for highly selective hydrogenation of acetylene

AbstractThe selective hydrogenation of acetylene to remove trace acetylene in ethylene plays a significant role in the ethylene polymerization industry. Herein, boron nitride (BN) was selected for encapsulating Pd nanoparticles to prepare a catalyst with atomic Pd sites exposed by a simple inorganic precursor‐based strategy. This atomically exposed Pd catalyst favors the desorption of ethylene kinetically instead of further hydrogenation, which is the key for improving the selective hydrogenation of acetylene. With only atomic Pd exposure, the Pd@BN‐0.5 catalyst reached 94% ethylene selectivity when acetylene conversion was 100% in a pure acetylene environment. More importantly, this atomically exposed Pd catalyst also showed an ethylene selectivity of 84.7% in ethylene‐rich feed, which is the simulated environment for industrial production. Finally, this atomic exposure strategy was extended to PdAg@BN, where 96.9% ethylene selectivity in a pure acetylene environment and 88.7% ethylene selectivity in an ethylene‐rich environment were obtained.

DFT Study of the Mechanism of Selective Hydrogenation of Acetylene by Rhodium Single-Atom Catalyst Supported on HY Zeolite.

The selectivity of acetylene hydrogenation by the Rh single-atom catalyst (SAC) supported on HY zeolite was investigated using density functional theory (DFT) and a 5/83T quantum mechanics/molecular mechanics (QM/MM) embedded cluster model. The calculated activation barrier (ΔG≠) for the oxidative addition of dihydrogen to the Rh metal center (15.9 kcal/mol) is lower in energy than that for the σ-bond metathesis of dihydrogen to the Rh-C bond (22.7 kcal/mol) and the Rh-O bond (28.4 kcal/mol). The activation barriers of the oxidative addition of subsequent dihydrogen molecules are significantly higher than that of the oxidative addition of the first dihydrogen molecule. These findings align with the experimentally observed activity and selectivity of the atomically dispersed Rh catalyst supported on HY zeolite. Natural bond orbital (NBO), molecular orbital (MO) and fuzzy bond order analyses were used to examine the interaction between the Rh metal center and acetylene versus ethylene ligands. The occupancies of the Rh lone pairs, π-bonding and π*-antibonding orbitals of acetylene and ethylene are consistent with the expected stronger interaction between the Rh metal center and acetylene compared to ethylene on the HY zeolite support.

An Aziridine and a 2-Pyrrolidone with Pyridyl Sidearms as Ligands for Cationic Rh(I)-Catalyzed Hydrosilylation and Hydrogenation of C=C and C≡C Bonds.

Phosphine- or carbene-based soft ligands are customarily used in Rh and other late transition metal catalyzed alkene and alkyne hydrosilylation and hydrogenation. We report here an aziridine and a 2-pyrrolidone with pyridyl sidearms, whose cationic Rh(I) complexes prove as excellent catalysts for hydrosilylating terminal olefins by Et3SiH giving anti-Markovnikov products selectively. To the best of our knowledge, the [(2-pyrrolidone)-Rh]+ seems to be the most active Rh catalyst recording a highest TOF of 24000 h-1. It works remarkably (TOF: 714 h-1) even at 10 ppm concentration! Terminal alkynes are hydrosilylated too to give β-(Z)-vinylsilanes selectively. Both catalysts also hydrogenate alkenes and doubly-hydrogenate alkynes, both terminal and internal, under ambient and benchtop conditions. But in hydrogenation, the [(aziridine)-Rh]+ catalyst works better. Both ligands and the Rh catalysts are air-stable.

Ligand-Shell Cooperativity in a Bilayer Silica-Sandwiched Mixed-Metals Nanocatalyst Design for Absolute Selectivity Switch.

Unlike homogeneous metal complexes, achieving absolute control over reaction selectivity in heterogeneous catalysts remains a formidable challenge due to the unguided molecular adsorption/desorption on metal-surface sites. Conventional organic surface modifiers or ligands and rigid inorganic and metal-organic porous shells are not fully effective. Here, we introduce the concept of "ligand-porous shell cooperativity" to desirably switch reaction selectivity in heterogeneous catalysis. We present a nanocatalyst design strategy consisting of bilayer silica-sandwiched 2D mixed metal islands. The intimate 2D/2D nanoscale interfacing between porous silica layers and flat island-like mixed-metal sites, combined with organic ligands, creates a nanoconfined microenvironment that enables reliable control of molecular orientation-dependent reactivity, affording the desired product in 100% selectivity. This design simultaneously leverages the hydrophobicity and flexibility of organic ligands and the nanoscale geometric rigidity of the pores inside the inorganic silica shell. Our strategy is effective with simple amorphous silica, random Cu-alloy, and commonly used metal-coordinating ligands. We demonstrate the applicability in industrially significant reactions: selective hydrogenation of alkynes, α,β-unsaturated esters/aldehydes, and nitroarenes. Our findings offer the valuable scope of a multicomponent compact nanoscale design strategy in next-generation switchable, sustainable, and recyclable catalysis.

From FCC to BCC: Engineering Pd Nuclearity in the PdCu Catalyst to Enhance Ethylene Selectivity in Acetylene Hydrogenation.

The ability to finely tune the nuclearity of active metal sites is critical for designing highly selective catalysts, especially for hydrogenation processes. In this work, we developed a novel PdCu catalyst with an ordered body-centered cubic (BCC) structure, enabling precise control over Pd nuclearity to optimize selectivity. Using a facile polyol synthesis method, we modulated the Pd coordination environment, reducing the Pd-Pd coordination number from 3 (disordered face-centered cubic, FCC) to 0 (ordered BCC), thereby achieving full isolation of Pd by the surrounding Cu atoms. This structural transformation enhances hydrogen spillover and weakens ethylene adsorption, resulting in superior activity for the selective hydrogenation of acetylene to ethylene. The ordered PdCu supported on Al2O3 (o-PdCu/Al2O3) achieved a 99% acetylene conversion with an 84.5% ethylene selectivity at near-room temperature. This work highlights the importance of controlling atomic-scale nuclearity in metal catalysts and provides a promising strategy for improving the catalytic efficiency and selectivity in industrially significant processes.

Hydrogen‐localization Transfer Regulation in 3D COFs Enhances Photocatalytic Acetylene Semi‐hydrogenation to Ethylene

In this work, a series of new crystalline three‐dimensional covalent organic frameworks (3D COFs) based on [8+4] construction was designed and successfully realized efficient photocatalytic acetylene (C2H2) hydrogenation to ethylene (C2H4). By regulating the hydrogen‐localization transfer effect in these 3D COFs，the Cz‐Co‐COF‐H containing cobalt glyoximate active centers exhibited excellent C2H2‐to‐C2H4 performance, with an average C2H4 yield of 1755.33 μmol g‐1 h‐1 in pure C2H2, also showed near 100% conversion of C2H2 in 1% C2H2 contained crude C2H4 mixtures (industry‐relevant conditions), and finally obtain polymer grade C2H4. In contrast, the Cz‐Co‐COF‐BF2 only showed one fifth activity due to lack of hydrogen‐localization transfer. The density functional theory (DFT), projected density of states (PDOS) and molecular dynamics "slow‐growth" kinetic calculations based on precise 3D COF structures confirmed that the rapid hydrogen species transfer, enhanced water dissociation and suitable C2H2 adsorption in COFs jointly contributed efficient photocatalytic acetylene hydrogenation (PAH). This work provides new opportunity towards rational design and development of crystalline photocatalysts for C2H2 hydrogenation.

Hydrogen-Localization Transfer Regulation in 3D COFs Enhances Photocatalytic Acetylene Semi-Hydrogenation to Ethylene.

In this work, a series of new crystalline three-dimensional covalent organic frameworks (3D COFs) based on [8+4] construction was designed and successfully realized efficient photocatalytic acetylene (C2H2) hydrogenation to ethylene (C2H4). By regulating the hydrogen-localization transfer effect in these 3D COFs, the Cz-Co-COF-H containing cobalt glyoximate active centers exhibited excellent C2H2-to-C2H4 performance, with an average C2H4 yield of 1755.33 μmol g-1 h-1 in pure C2H2, also showed near 100 % conversion of C2H2 in 1 % C2H2 contained crude C2H4 mixtures (industry-relevant conditions), and finally obtain polymer grade C2H4. In contrast, the Cz-Co-COF-BF2 only showed one fifth activity due to lack of hydrogen-localization transfer. The density functional theory (DFT), projected density of states (PDOS) and molecular dynamics "slow-growth" kinetic calculations based on precise 3D COF structures confirmed that the rapid hydrogen species transfer, enhanced water dissociation and suitable C2H2 adsorption in COFs jointly contributed efficient photocatalytic acetylene hydrogenation (PAH). This work provides new opportunity towards rational design and development of crystalline photocatalysts for C2H2 hydrogenation.

Electrocatalytic hydrogenation of alkynes and alkenes using a proton conductive graphene oxide membrane.

Graphene-based membranes are emerging as promising materials for energy and chemical conversion due to their exceptional proton conductivity and stability. In this study, we report a graphene oxide (GO) nanosheet membrane for electrochemical hydrogenation reactions. The GO membrane demonstrates excellent proton conductivity, confirmed through concentration cell measurement and complex impedance spectroscopy, and efficiently facilitates proton transport when integrated with active platinum catalysts as the cathode and anode. This system enables selective hydrogenation of alkynes and alkenes into their corresponding alkanes, achieving selectivities of 82% to 93%. This work highlights the potential of graphene-based membrane reactors as cost-effective, scalable, and energy-efficient alternative to traditional hydrogenation methods.

Acetylene semi-hydrogenation catalyzed by Pd single atoms sandwiched in zeolitic imidazolate frameworks via hydrogen activation and spillover.

The semi-hydrogenation of alkynes into alkenes rather than alkanes is of great importance in the chemical industry, and palladium-based metallic catalysts are currently employed. Unfortunately, a fairly high cost and uncontrollable over-hydrogenation impeded the application of Pd-based catalysts on a large scale. Herein, a sandwich structure single atom Pd catalyst, Z@Pd@Z, was prepared via impregnation exchange and epitaxial growth methods (Z stands for ZIF-8), in which Pd single atoms were stabilized by pyrrolic N in a zeolitic imidazolate framework (ZIF-8). Semi-hydrogenation of acetylene was performed and Z@Pd@Z achieved 100% acetylene conversion at 120 °C with an ethylene selectivity of more than 98.3% at an extra low Pd concentration. Z@Pd@Z exhibited a specific activity of 1872.69 mLC2H4 mgPd-1 h-1, surpassing most of the reported Pd-based catalysts. The existence of Pd single atoms coordinated by nitrogen (Pd-N4) was verified by XAS (synchrotron X-ray absorption spectroscopy), which provided active sites for H2 dissociation and the dissociated hydrogen quickly spilled over the surface of the outer ZIF layer to hydrogenate alkyne to ethene; besides, the catalytic activity could be controlled by adjusting the thickness of the outer ZIF layer. The confinement of the ZIF on Pd single-atom sites and the high energy barrier of ethylene hydrogenation were found to be responsible for the superior C2H2 semi-hydrogenation activity. This work opens up valuable insights into the design of ZIF-derived single-atom catalysts for efficient acetylene selective hydrogenation.

Alkyne dichotomy and hydrogen migration in binuclear cyclopentadienylmetal alkyne complexes.

The structures and energetics of the binuclear cyclopentadienylmetal alkyne systems Cp2M2C2R2 (M = Ni, Co, Fe; R = Me and NMe2) have been investigated using density functional theory. For the Cp2M2C2(NMe2)2 (M = Ni, Co, Fe) systems the relative energies of isomeric tetrahedrane Cp2M2(alkyne) structures having intact alkyne ligands and alkyne dichotomy structures Cp2M2(CNMe2)2 in which the C[triple bond, length as m-dash]C triple bond of the alkyne has broken completely to give separate Me2NC units depending on the central metal atoms. For the nickel system Cp2Ni2C2(NMe2)2 as well as the related nickel systems Cp2Ni2(MeC2NMe2) and Cp2Ni2C2Me2 the tetrahedrane structures are clearly preferred energetically consistent with the experimental syntheses of several stable Cp2Ni2(alkyne) complexes. The tetrahedrane and alkyne dichotomy structures have similar energies for the Cp2Co2C2(NMe2)2 system whereas the alkyne dichotomy structures are significantly energetically preferred for the Cp2Fe2C2(NMe2)2 system. The potential energy surfaces for the Cp2M2(MeC2NMe2) and Cp2M2C2Me2 systems (M = Co, Fe) are complicated by low-energy structures in which hydrogen migration occurs from the alkyne methyl groups to one or both alkyne carbon atoms to give Cp2M2(C3H3NMe2) and Cp2M2(C3H3Me) derivatives with bridging metalallylic ligands, Cp2M2(CH2[double bond, length as m-dash]C[double bond, length as m-dash]CHNMe2) and Cp2M2(CH2[double bond, length as m-dash]C[double bond, length as m-dash]CHMe) with bridging allene ligands, as well as Cp2M2(CH2[double bond, length as m-dash]CH-CNMe2) and Cp2M2(CH2[double bond, length as m-dash]CH-CHMe) with bridging vinylcarbene ligands. For the Cp2M2C2Me2 (M = Co, Fe) systems migration of a hydrogen atom from each methyl group to an alkyne carbon atom can give relatively low-energy Cp2M2(CH2[double bond, length as m-dash]CH-CH[double bond, length as m-dash]CH2) structures with a bridging butadiene ligand. Five transition states have been identified in a proposed mechanism for the conversion of the Cp2Co2/MeC[double bond, length as m-dash]CNMe2 system to the cobaltallylic complex Cp2Co2(C3H3NMe2) with intermediates having agostic C-H-Co interactions and an activation energy barrier sequence of 13.1, 17.0, 15.2, and 12.0 kcal mol-1.

Pd catalysts doped with B/C atoms in the subsurface: the positive effect of interstitial atoms in regulating the selectivity of acetylene catalytic hydrogenation.

At present, the modification of palladium (Pd) catalysts is an important topic due to its potential to enhance catalytic performance and reduce catalyst costs. In this work, boron (B) and carbon (C) are interstitially doped into the subsurface of Pd to construct Pd4LB2L and Pd4LC2L catalysts. The adsorption properties of acetylene and ethylene, the mechanism of acetylene hydrogenation, and ethylene selectivity are studied based on density functional theory (DFT) calculations. The results show that the ethylene selectivity of the Pd4LB2L catalyst is significantly enhanced compared with that of Pd(111). The adsorption of CH2CH2 is weakened substantially after B element doping, and the ethylene selectivity descriptor (Esel) value of the Pd4LB2L catalyst reaches 19.7 kJ mol-1. It is revealed that non-metallic atoms doped into the subsurface layer of metal catalysts change the adsorption of reactant/intermediate molecules and the selectivity of ethylene by affecting the electronic structure and properties of Pd atoms in the surface layer. This work provides insights into the selectivity of modified Pd-based catalysts for selective hydrogenation of acetylene and realization of cost-effective catalysts.

Synergistic effect of ligand-cluster structure and support in gold nanocluster catalysts for selective hydrogenation of alkynes.

In the field of nanocluster catalysis, it is crucial to understand the interplay of different parameters, such as ligands, support and pretreatment and their effect on the catalytic process. In this study, we chose the selective hydrogenation of phenylacetylene as a model reaction and employed two gold nanoclusters as catalysts, the phosphine protected Au11 and the thiolate protected Au25, each with different binding motifs. They were supported on MgO, Al2O3 and a hydrotalcite (HT), chosen for their different acidity. We found that while in the case of the Au11 MgO was the preferred support and the pretreatment had a positive impact on the catalysis. For the Au25 the HT performed best and pretreating had negative effects, indicating that the bonding motif of the ligands and their interaction with the support is crucial for the catalytic process. Using X-ray absorption spectroscopy we could trace these phenomena to changes in the cluster-ligand interface, which seem to impact the stability of the catalysts.