Catalysts For Hydrogenation Of Alkenes Research Articles

Scaling-Up Microwave-Assisted Synthesis of Highly Defective Pd@UiO-66-NH2 Catalysts for Selective Olefin Hydrogenation under Ambient Conditions.

The need to develop green and cost-effective industrial catalytic processes has led to growing interest in preparing more robust, efficient, and selective heterogeneous catalysts at a large scale. In this regard, microwave-assisted synthesis is a fast method for fabricating heterogeneous catalysts (including metal oxides, zeolites, metal-organic frameworks, and supported metal nanoparticles) with enhanced catalytic properties, enabling synthesis scale-up. Herein, the synthesis of nanosized UiO-66-NH2 was optimized via a microwave-assisted hydrothermal method to obtain defective matrices essential for the stabilization of metal nanoparticles, promoting catalytically active sites for hydrogenation reactions (760 kg·m-3·day-1 space time yield, STY). Then, this protocol was scaled up in a multimodal microwave reactor, reaching 86% yield (ca. 1 g, 1450 kg·m-3·day-1 STY) in only 30 min. Afterward, Pd nanoparticles were formed in situ decorating the nanoMOF by an effective and fast microwave-assisted hydrothermal method, resulting in the formation of Pd@UiO-66-NH2 composites. Both the localization and oxidation states of Pd nanoparticles (NPs) in the MOF were achieved using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray photoelectron spectroscopy (XPS), respectively. The optimal composite, loaded with 1.7 wt % Pd, exhibited an extraordinary catalytic activity (>95% yield, 100% selectivity) under mild conditions (1 bar H2, 25 °C, 1 h reaction time), not only in the selective hydrogenation of a variety of single alkenes (1-hexene, 1-octene, 1-tridecene, cyclohexene, and tetraphenyl ethylene) but also in the conversion of a complex mixture of alkenes (i.e., 1-hexene, 1-tridecene, and anethole). The results showed a powerful interaction and synergy between the active phase (Pd NPs) and the catalytic porous scaffold (UiO-66-NH2), which are essential for the selectivity and recyclability.

Rhodium Complexes with a Pyridine-2-yloxy-silyl-Based N,Si-Ligand: Bonding Situation and Activity as Alkene Hydrogenation Catalysts

Rhodium Complexes with a Pyridine-2-yloxy-silyl-Based N,Si-Ligand: Bonding Situation and Activity as Alkene Hydrogenation Catalysts

Ruthenium-Picolylamine-Incorporated Mixed-Linker MOFs: Highly Active Heterogeneous Catalysts for Olefin and Aldehyde Hydrogenation

Ruthenium-Picolylamine-Incorporated Mixed-Linker MOFs: Highly Active Heterogeneous Catalysts for Olefin and Aldehyde Hydrogenation

Achieving super dispersed metallic nickel nanoparticles over MCM-41 for highly active and stable hydrogenation of olefins and aromatics

Hydrogenation of olefins and aromatics is of significance for fuel processing and hydrogen storage, and developing nickel (Ni) catalyst highly active at low reaction temperature is the key to low the process cost. Herein we developed an ammonium citrate assisted impregnation method to fabricate loaded Ni catalyst (NiM-2) for hydrogenation. The Ni2+ species are anchored on the support MCM-41 strongly and evenly in form of Ni-citrate complex via the H-bonding between Si-OH group of MCM-41 and –COO- of citrate. During reduction, the carbon layerstemporarily formed by carbonization of citrate species inhibit the transfer and sintering of Ni species, and finally induces ultra-small metallic Ni nanoparticles after carbon layers slow decomposition by Ni species. Low coordination numbers and strong electron interaction between small metallic Ni nanoparticles and MCM-41 support upshift the d-band center of metallic Ni atoms. In hydrogenation, the small particle size and easier reduction for oxidized Ni species provide abundant active sites for reaction, and the upshifted d-band center induces strongly adsorption and activation of C = C bonds, which is confirmed for the first time in our work. As a result, the catalyst exhibits superior activity compared with reported and commercial Ni-based catalysts for hydrogenation of olefins and aromatics. Specifically, the catalyst with higher Ni loading (18%) exhibits good activity under room temperature and 0.1 MPa for hydrogenation of dicyclopentadiene and are comparable to Pd catalysts, making it as one of the best non-precious metal catalysts for hydrogenation reaction. And also, NiM-2 shows extremely high stability.

Synergistic effects of ZnO–ZrO2@SAPO-34 core-shell catalyst in catalyzing CO2 hydrogenation for the synthesis of light olefins

As a method for valorizing CO2 emissions, hydrogenation of CO2 into olefins remains viable. Herein, ZnO–ZrO2 and SAPO-34 were prepared and used as bifunctional catalysts in light olefins synthesis through CO2 hydrogenation. The combination of the two components includes layered filling, physically mixing, physically grinding, and core-shell composite. Based on the evaluation, different combinations resulted in diverse product distributions. ZnO–ZrO2@SAPO-34 core-shell catalysts are better suited for promoting synergistic effects, which facilitate light olefin production. Due to the unique core-shell structure, appropriate weak acidity, and moderate basicity, the light olefins selectivity was enhanced. Further, the calcination time and core-shell mass ratio were optimized over the ZnO–ZrO2@SAPO-34 core-shell catalyst to investigate the synergistic effects between catalytic structure and catalytic performance. With a 3:1 core-shell mass ratio and 3 h of calcination at 550 °C, the optimal ZnO–ZrO2@SAPO-34 (3:1) catalyst was obtained, which exhibited 73% selectivity to light olefins with CO2 conversion of 16.1%, whereas the selectivity of CO and CH4 was lower than 44% and 1.5%, respectively. This study provides new insights into the design and optimization of ZnO–ZrO2@SAPO-34 core-shell catalysts for CO2 hydrogenation and synthesis of light olefins.

Discovery of a Thioxanthone–TfOH Complex as a Photoredox Catalyst for Hydrogenation of Alkenes Using p ‐Xylene as both Electron and Hydrogen Sources

Hydrogenation of alkenes is one of the most fundamental transformations in organic synthesis, and widely used in the petrochemical, pharmaceutical, and food industries. Although numerous hydrogenation methods have been developed, novel types of catalysis with new mechanisms and new hydrogen sources are still desirable. Thioxanthone (TX) is widely used in energy-transfer photoreactions, but rarely in photoredox processes. Herein we show that a catalytic amount of TfOH as a co-catalyst can tune the properties of TX to make it a photoredox catalyst with highly enhanced oxidative capability in the hydrogenation of carbonylated alkenes with the cheap petroleum industrial product p-xylene serving as the hydrogen source. Deuterium can also be introduced by this method by using D2O as the D source. To the best of our knowledge, this is the first example of using p-xylene as a hydrogen source.

Discovery of a Thioxanthone-TfOH Complex as a Photoredox Catalyst for Hydrogenation of Alkenes Using p-Xylene as both Electron and Hydrogen Sources.

Hydrogenation of alkenes is one of the most fundamental transformations in organic synthesis, and widely used in the petrochemical, pharmaceutical, and food industries. Although numerous hydrogenation methods have been developed, novel types of catalysis with new mechanisms and new hydrogen sources are still desirable. Thioxanthone (TX) is widely used in energy-transfer photoreactions, but rarely in photoredox processes. Herein we show that a catalytic amount of TfOH as a co-catalyst can tune the properties of TX to make it a photoredox catalyst with highly enhanced oxidative capability in the hydrogenation of carbonylated alkenes with the cheap petroleum industrial product p-xylene serving as the hydrogen source. Deuterium can also be introduced by this method by using D2 O as the D source. To the best of our knowledge, this is the first example of using p-xylene as a hydrogen source.

Retraction Note: PdAu Alloy Nanoparticles Encapsulated by PPI-g-MWCNTs as a Novel Catalyst for Chemoselective Hydrogenation of Alkenes Under Mild Conditions

Retraction Note: PdAu Alloy Nanoparticles Encapsulated by PPI-g-MWCNTs as a Novel Catalyst for Chemoselective Hydrogenation of Alkenes Under Mild Conditions

The Implications of the Brønsted Acidic Properties of Crabtree-Type Catalysts in the Asymmetric Hydrogenation of Olefins.

Chiral iridium complexes derived from Crabtree’s catalyst are highly useful in modern hydrogenations of olefins attributed to high reactivity, stereoselectivity, and stability. Despite that these precatalysts are pH neutral, the reaction mixtures turn acidic under hydrogenation conditions. This Perspective is devoted to the implications of the intrinsic Brønsted acidity of catalytic intermediates in asymmetric hydrogenation of olefins. Despite that the acidity has often been used only as a rationale for side-product formation, more recent methodologies have started to use this property advantageously. We hope that this Perspective serves as a stimulant for the development of such compelling and new asymmetric hydrogenations. The inherent scientific opportunities in utilizing or annihilating the generated Brønsted acid are enormous, and potential new innovations are outlined toward the end.

Nickel−palladium alloy nanoparticles supported on reduced graphene oxide decorated with metallic aluminum nanoparticles (Al-rGO/NiPd): a multifunctional catalyst for the transfer hydrogenation of nitroarenes and olefins using water as a hydrogen source

A multifunctional nanocatalyst, Al-rGO/Ni40Pd60, is designed for the transfer hydrogenation of nitroarenes and olefins using water as a hydrogen source and solvent.

Synthesis of Ni(ii)-phosphotungstic acid/nanocrystalline HZSM-5 catalyst for ultra clean gasoline in a single-stage reactor

An excellent catalyst for hydrodesulfurization, aromatization and olefin hydrogenation of FCC gasoline, is designed in this paper.

Cover Feature: Silylene‐Bridged Tetranuclear Palladium Cluster as a Catalyst for Hydrogenation of Alkenes and Alkynes (ChemCatChem 1/2021)

Cover Feature: Silylene‐Bridged Tetranuclear Palladium Cluster as a Catalyst for Hydrogenation of Alkenes and Alkynes (ChemCatChem 1/2021)

Silylene‐Bridged Tetranuclear Palladium Cluster as a Catalyst for Hydrogenation of Alkenes and Alkynes

AbstractA planar tetranuclear palladium cluster was obtained from the reaction of a cyclotetrasilane with [Pd(CNtBu)2]3. Single‐crystal X‐ray diffraction analysis and DFT calculations revealed that the tetranuclear framework of the cluster was supported effectively by the bridging organosilylene ligand. Although [Pd(CNtBu)2]3 as well as mononuclear palladium bis(silyl) complex, cis‐Pd(SiMePh2)2(CNtBu)2, do not act as the effective catalyst, the planar tetranuclear palladium cluster acts as an efficient catalyst for the hydrogenation of alkenes and alkynes including sterically hindered tri‐ and tetra‐substituted alkenes.

Rate-Limiting Steps in the Intramolecular C-H Activation of Ruthenium N-Heterocyclic Carbene Complexes.

Ruthenium (II) complexes with N-heterocyclic carbenes (NHC) are commonly used as efficient catalysts in hydrogenation of olefins with simultaneous intramolecular C–H activation. Using the DFT approach, we have investigated the entire hydrogenation reaction pathway for four new potential catalysts and ethylene, a model substrate. Our calculations imply that the dissociation of phosphine is the rate-limiting step of hydrogenation, contrary to recent computational results. We also found that catalysts bearing NHCs with aliphatic and aromatic side groups are energetically favorable over other aliphatic cyclohexyl-substituted NHC. To examine how electronic properties of various catalysts influence the energetic barrier in the crucial steps of the reaction, we applied the Noncovalent Interaction analysis, which allowed us to reveal crucial interactions which stabilize/destabilize important intermediates and transition states in the hydrogenation reaction.

Comparative Study of Homogeneous and Silica Immobilized N^N and N^O Palladium(II) Complexes as Catalysts for Hydrogenation of Alkenes, Alkynes and Functionalized Benzenes

This work reports the use of homogeneous and silica immobilized palladium(II) complexes of ligands (2-phenyl-2-((3(triethoxysilyl)propyl)imino)ethanol) (L1), (4-methyl-2-((3(triethoxysilyl)propyl)imino)methyl)phenol) (L2), [L1-MCM-41] (L1im), and [L2-MCM-41] (L2im) as catalysts in molecular hydrogenation of alkenes, alkynes and functionalized benzenes. The homogeneous complexes [Pd(L1)2] (Pd1), [Pd(L2)2] (Pd2), [Pd(L1)(Cl2)] (Pd3), and [Pd(L2)(Cl2)] (Pd4), and their respective silica immobilized complexes [Pd(L1)2]-MCM-41] (Pd1im), [Pd(L2)2)-MCM-4] (Pd2im), [Pd (L1)(Cl2)-MCM-41] (Pd3im) and [Pd(L2)(Cl2)]-MCM-41] (Pd4im) formed active catalysts in the molecular hydrogenation of these substrates. The catalytic activities and product distribution in these reactions were largely dictated by the nature of the substrate. The kinetic studies revealed a pseudo-first order dependence on styrene substrate for both the homogeneous and immobilized catalysts. Significantly, the selectivity of both homogeneous and immobilized catalysts were comparable in the hydrogenation of both alkynes and multi-functionalized benzenes. The supported catalysts could be recycled up to four times with minimum loss of catalytic activity and showed absence of any leaching from hot filtration experiments. Kinetics and poisoning studies established that complexes Pd1–Pd4 were largely homogeneous in nature, while the immobilized complexes Pd1im–Pd4im formed Pd(0) nanoparticles as the main active species.

Combined KH/alkaline-earth metal amide catalysts for hydrogenation of alkenes

Breaking saline KH: The combined KH/alkaline-earth metal amide catalysts display much better catalytic activity than their components in the hydrogenation of alkenes, suggesting the degradation and activation of saline KH with the metal amides.

Development of nitrogen-doped bamboo-like carbon nanotubes coated zeolite beads as \u201csupport on support\u201d catalyst for the catalytic hydrogenation of olefins

“Support on support” type catalysts were developed by applying catalytic chemical vapour deposition (CCVD). Nitrogen-doped bamboo-like carbon nanotubes (N-BCNT) were synthetized on the surface of zeolite beads by using four different metals (Ni, Fe, Co and V). Based on the thermogravimetric analysis (TGA), the Ni, Co and Fe were catalytically active for nanotube production on the zeolite surface. It was confirmed by SEM measurements, that the surface of the beads was extensively covered by N-BCNTs. Based on the TGA and SEM results, two SoS systems were selected for further catalysts development, which differed the most in their nanotube content (difference 11.63 wt%) and surface coverage. These were two nickel containing samples with 6.72 and 18.35 wt% N-BCNT. Palladium nanoparticles were deposited (1 wt%) on the surface of the N-BCNT/zeolite systems, and the final Pd/SoS catalysts were tested in hydrogenation of 1-butene. The conversion maximum (X = 100%) was reached after 6 min in both cases independently of the nanotube content and coverage (WHSV: 5.49). To measure the lifetime of the selected catalysts, the WHSV was increased from 5.49 to 11 (by increasing the gas flow) and the systems were still active after 6 h. Thus, the lifetime of the catalysts is longer than 6 h. Furthermore, by increasing the gas flow (WHSV = 11), higher conversion was achieved (98%) with the sample which has a higher nanotube content Therefore, smaller carbon nanotube content is still as catalyst support. The final Pd/SoS catalysts were active, easy to treat and removable from the reactors and could work with smaller carbon nanotube content as well. Thus, a more economical catalysts was developed, than a solely carbon nanotube-based counterparts which lack the zeolite core.

PtAu bimetallic nanocatalyst for selective hydrogenation of alkenes over aryl halides

Herein, we present a new strategy that for the first time achieved chemo- and enantio-selective hydrogenation of alkenes over arylhalides. Key to the success is that instead of using external poisons, we use the composition of the bimetallic nanocrystal catalysts to control chemoselectivity (hydrogenation of C=C bonds without cleavage of Ar-X bonds). We further show that this system combined with surface modifying chiral ligands can control the enantioselectivity. Thus, after synthesizing and screening a series of easily accessible MxAuy (M = Pd, Pt; x, y = 1, 3, 5) bimetallic nanocrystals (9-10 nm) supported on activated carbon, we identified that Pt1Au1/C is a recyclable and generally applicable catalyst for the chemoselective hydrogenation of alkenes without cleaving aryl halogen bonds. Furthermore, cinchonidine modified Pt1Au1/C is shown to be capable of enantioselective hydrogenation, as illustrated by the rapid and enantio-enriched synthesis of RIP1 inhibitor analogue 7-Br-O-Nec1.

Alkene Transfer Hydrogenation with Alkaline-Earth Metal Catalysts.

The alkene transfer hydrogenation (TH) of a variety of alkenes has been achieved with simple AeN''2 catalysts [Ae=Ca, Sr, Ba; N''=N(SiMe3 )2 ] using 1,4-cyclohexadiene (1,4-CHD) as a H source. Reaction of 1,4-CHD with AeN''2 gave benzene, N''H, and the metal hydride species N''AeH (or aggregates thereof), which is a catalyst for alkene hydrogenation. BaN''2 is by far the most active catalyst. Hydrogenation of activated C=C bonds (e.g. styrene) proceeded at room temperature without polymer formation. Unactivated (isolated) C=C bonds (e.g. 1-hexene) needed a higher temperature (120 °C) but proceeded without double-bond isomerization. The ligands fully control the course of the catalytic reaction, which can be: 1) alkene TH, 2) 1,4-CHD dehydrogenation, or 3) alkene polymerization. DFT calculations support formation of a metal hydride species by deprotonation of 1,4-CHD followed by H transfer. Convenient access to larger quantities of BaN''2 , its high activity and selectivity, and the many advantages of TH make this a simple but attractive procedure for alkene hydrogenation.

Alkene Transfer Hydrogenation with Alkaline‐Earth Metal Catalysts

AbstractThe alkene transfer hydrogenation (TH) of a variety of alkenes has been achieved with simple AeN′′2 catalysts [Ae=Ca, Sr, Ba; N′′=N(SiMe3)2] using 1,4‐cyclohexadiene (1,4‐CHD) as a H source. Reaction of 1,4‐CHD with AeN′′2 gave benzene, N′′H, and the metal hydride species N′′AeH (or aggregates thereof), which is a catalyst for alkene hydrogenation. BaN′′2 is by far the most active catalyst. Hydrogenation of activated C=C bonds (e.g. styrene) proceeded at room temperature without polymer formation. Unactivated (isolated) C=C bonds (e.g. 1‐hexene) needed a higher temperature (120 °C) but proceeded without double‐bond isomerization. The ligands fully control the course of the catalytic reaction, which can be: 1) alkene TH, 2) 1,4‐CHD dehydrogenation, or 3) alkene polymerization. DFT calculations support formation of a metal hydride species by deprotonation of 1,4‐CHD followed by H transfer. Convenient access to larger quantities of BaN′′2, its high activity and selectivity, and the many advantages of TH make this a simple but attractive procedure for alkene hydrogenation.