Hydrogenation Of Olefins Research Articles

Advances in Carbon Dioxide Catalytic Conversion and Applications

To achieve the global climate goals set out in the Paris Agreement, reducing carbon dioxide (CO2) emissions and utilizing resources have become key areas of focus within international energy technology research and development. CO2 can be converted into high-value chemicals, including hydrocarbons, alcohols and hydrocarbons, through the catalytic technology. This process can potentially address environmental issues while generating economic benefits. This paper presents a review of the principal products resulting from the catalytic conversion of CO2, together with an examination of their practical applications. These include hydrogenation of olefins, light aromatics, methanol, polyols, and synthetic bioconversion technologies. The development of catalysts with high conversion and selectivity represents a key area of current research. In the future, it will be necessary to combine physical, chemical, and biological technologies to establish an engineered heterogeneous carbon sequestration technology system to achieve the efficient conversion and utilization of CO2.

Synchronous photocatalytic benzimidazole formation and olefin reduction by magnetic separable visible-light-driven Pd-g-C3N4-Vanillin@γ-Fe2O3-TiO2 Nanocomposite

A visible light-responsive magnetically separable photocatalyst Pd-g-C3N4-Vanillin@γ-Fe2O3-TiO2 is fabricated using vanillin as a natural junction under ultrasonic agitation. Structural, morphological, optical, thermal, and magnetic assessments of the as-prepared catalyst are carried out. The photocatalyst successfully drives the simultaneous benzimidazole formation, and olefin hydrogenation with high atom economy under blue LED light and mild conditions. The photocatalytic activity of Pd-g-C3N4-Vanillin@γ-Fe2O3-TiO2 is significantly affected by the γ-Fe2O3:TiO2 weight ratio. PL spectra revealed the effective separation of carriers in the fabricated catalyst promoting its photocatalytic activity. The action spectra using the apparent quantum efficiency (AQE) exhibited the maximum AQEs at 520 and 750 nm in which the highest performance for styrene hydrogenation is observed. The title magnetically separable heterogeneous photocatalyst provides high yields of products under perfectly safe visible light, produces low/zero waste, and avoids using an external high-pressure hydrogen gas source, harmful solvents, undesirable additives, and reducing agents rendering green conditions for chemical reactions.

Nano-Pd/SiO2 aerogel catalyst prepared via ambient pressure drying process using perlite powder in hydrogenation and cross-coupling reactions

Perlite, a cheap silica source with abundant reserves in countries such as Türkiye, China, and Greece, was used to produce nano Pd-doped silica aerogel powder for the first time in this study. The microstructure and morphology of the prepared silica aerogel powder were examined using SEM, FE-SEM, and TEM. The phases of the silica aerogel powders were analyzed via XRD (X-ray Diffraction) technique. The chemical bonding of the surface modifier with aerogels was analyzed by Fourier transform infrared spectroscopy (FTIR, Spectrum RX-1, Perkin Elmer). Surface areas, pore volumes, distributions, and particle sizes of the alumina-silica-based aerogel powders with a porous structure were measured using a Micromeritics/ASAP 2020 brand BET (Brunauer, Emmet, and Teller) device in a liquid nitrogen gas environment at 77K.The efficiency of this nano Pd-doped silica aerogel powder was investigated as a heterogeneous catalyst for well-known transformations in organic synthesis, such as alkene hydrogenation and cross-linking reactions. The results indicated that the developed method is chemoselective, reducing only carbon-carbon multiple bonds without affecting C-N or C-O multiple bonds, such as carbonyl and nitrile. The effectiveness of the newly developed catalyst was also investigated in Heck and Suzuki-Miyaura reactions, yielding the targeted products with high efficiency.Thus, an inexpensive, economical, and environmentally friendly method has been developed that is potentially applicable in the hydrogenation and cross-coupling reactions of alkenes.

Palladium-Catalyzed Site-Selective Hydrogenation of Unactivated Alkenes Directed by 8-Aminoquinoline Amides.

We have developed a method for the site-selective hydrogenation of unactivated alkenes using 8-aminoquinoline amide as the directing group. For unactivated alkenes with two C-C double bonds, Daugulis's 8-aminoquinoline amide facilitated the site-selective hydrogenation of the desired C-C double bond, producing a product in which one C-C double bond was reduced. Site-selective reduction methodologies using intramolecular directing groups are expected to contribute significantly to the synthesis of molecules with multiple reducible functional groups in the future.

Photocatalytic Hydrogenation of Alkenes Using Water as Both the Reductant and the Proton Source.

Utilization of clean and low-cost water as the reductant to enable hydrogenation of alkenes is highly attractive in green chemistry. However, this research subject is considerably challenging due to the sluggish kinetics of the water oxidation half-reaction. It is also very difficult to avoid the undesired oxidation of alkenes because that this oxidation is far easier to occur than the desired oxidation of water from thermodynamic standpoint. Herein, this challenge is overcome by applying a cooperative catalysis where HCl is used as the cocatalyst to accelerate Pt/g-C3N4-catalyzed water oxidation and suppress the undesired oxidation of the alkene. This provides an example for using water as the reductant and the proton source to enable the photocatalytic hydrogenation of alkenes. The present method exhibits broad substrate applicability, and allows various arylethenes and aliphatic alkenes to undergo the hydrogenation smoothly.

Anchoring Frustrated Lewis Pair Active Sites on Copper Nanoclusters for Regioselective Hydrogenation.

In recent years, the concept of Frustrated Lewis Pairs (FLPs), which consist of a combination of Lewis acid (LA) and Lewis base (LB) active sites arranged in a suitable geometric configuration, has been widely utilized in homogeneous catalytic reactions. This concept has also been extended to solid supports such as zeolites, metal oxide surfaces, and metal/covalent organic frameworks, resulting in a diverse range of heterogeneous FLP catalysts that have demonstrated notable efficiency and recyclability in activating small molecules. This study presents the successful immobilization of FLP active sites onto the surface of ligand-stabilized copper nanoclusters with atomic precision, leading to the development of copper nanocluster FLP catalysts characterized by high reactivity, stability, and selectivity. Specifically, thiol ligands containing 2-methoxyl groups were strategically designed to stabilize the surface of [Cu34S7(RS)18(PPh3)4]2+ (where RSH = 2-methoxybenzenethiol), facilitating the formation of FLPs between the surface copper atoms (LA) and ligand oxygen atoms (LB). Experimental and theoretical investigations have demonstrated that these FLPs on the cluster surface can efficiently activate H2 through a heterolytic pathway, resulting in superior catalytic performance in the hydrogenation of alkenes under mild conditions. Notably, the intricate yet precise surface coordination structures of the cluster, reminiscent of enzyme catalysts, enable the hydrogenation process to proceed with nearly 100% selectivity. This research offers valuable insights into the design of FLP catalysts with enhanced activity and selectivity by leveraging surface/interface coordination chemistry of ligand-stabilized atomically precise metal nanoclusters.

Stable and Versatile Pd Precursors for the Preparation of Robust Pd Catalysts Under Continuous-Flow.

To achieve global sustainability, the chemical and engineering communities require the development of versatile precursors that can be used to synthesize robust catalysts. To meet this demand, we developed a new Pd precursor for highly efficiently incorporating fine Pd-metal into supports. An atmospherically stable Pd precursor (Pd-80) was prepared by thermally promoting the aerobic oxidation of tetrakis(triphenylphosphine)palladium. The physical properties of Pd-80 were investigated by NMR spectroscopy, SEM, XPS, solvent-relaxation NMR spectroscopy, and dynamic light scattering (DLS) experiments. We also prepared a cordierite-supported Pd catalyst (Pd/cordierite) by stirring Pd-80 and cordierite powder in chloroform at room temperature. Pd/cordierite selectively catalyzed the hydrogenation of various reducible functional groups, including alkynes, azides, nitro groups, olefins, CO2Bn, N-Cbz, O-Bn, aromatic ketones, and styrene oxide, in continuous-flow hydrogenation reactions. The Pd/cordierite-catalyzed continuous-flow hydrogenation of nitrobenzene derivatives afforded the corresponding anilines, with catalytic activities maintained for over 250 h of continuous operation with a turnover number (TON) of 61,090.

Stereocontrolled Hydrogenation of Conjugated Enones to Alcohols via Dual Iridium-Catalysis.

The concept of dual catalysis is an emerging area holding high potential in terms of preparative efficiency, yet faces severe challenges in compatibility of reaction conditions and interference of catalysts. The transition-metal catalyzed stereoselective hydrogenation of olefins and ketones typically proceeds under different reaction conditions and/or uses a different reductant. As a result, these two types of hydrogenations can normally not be performed in the same pot. Herein, the stereocontrolled hydrogenation of enones to saturated alcohols is described, enabled by orthogonal dual iridium catalysis, using molecular hydrogen for both reductions. In this one-pot procedure, N,P-iridium catalysts (hydrogenation active towards olefins) and NHC,P-iridium catalysts (hydrogenation active towards ketones) operated independently of one another allowing the construction of two contiguous stereogenic centers up to 99% ee, 99/1 d.r. Ultimately, by simple selection of the chirality of either ligands, the enone could be efficiently reducedto allfour stereoisomers of the saturated alcohol in equally high stereopurity. This degree of stereocontrol for the synthesis of different stereoisomers by dual transition-metal catalyzed hydrogenation was previously not attained. The generality in substituted enones (alkyl, aryl, heteroaryl) demonstrate the wide applicability of this concept.

Stereocontrolled Hydrogenation of Conjugated Enones to Alcohols via Dual Iridium‐Catalysis

The concept of dual catalysis is an emerging area holding high potential in terms of preparative efficiency, yet faces severe challenges in compatibility of reaction conditions and interference of catalysts. The transition‐metal catalyzed stereoselective hydrogenation of olefins and ketones typically proceeds under different reaction conditions and/or uses a different reductant. As a result, these two types of hydrogenations can normally not be performed in the same pot. Herein, the stereocontrolled hydrogenation of enones to saturated alcohols is described, enabled by orthogonal dual iridium catalysis, using molecular hydrogen for both reductions. In this one‐pot procedure, N,P‐iridium catalysts (hydrogenation active towards olefins) and NHC,P‐iridium catalysts (hydrogenation active towards ketones) operated independently of one another allowing the construction of two contiguous stereogenic centers up to 99% ee, 99/1 d.r. Ultimately, by simple selection of the chirality of either ligands, the enone could be efficiently reduced to all four stereoisomers of the saturated alcohol in equally high stereopurity. This degree of stereocontrol for the synthesis of different stereoisomers by dual transition‐metal catalyzed hydrogenation was previously not attained. The generality in substituted enones (alkyl, aryl, heteroaryl) demonstrate the wide applicability of this concept.

Cobalt‐Potassium Synergistic Modification Effects on Fe‐Based Catalysts for CO2 Hydrogenation to Low‐Carbon Olefins

ABSTRACTTo enhance the CO2 hydrogenation activity and low‐carbon olefin selectivity of Fe‐based catalysts, a strategy involving the use of metal promoters to modulate the structure of active metal centers in catalyst preparation was proposed. The incipient wetness impregnation method was used to introduce modifying agents K and/or Co into the Fe/Al2O3 catalyst. Characterization techniques such as XRD, BET, SEM, HRTEM, H2‐TPR, XPS, CO2‐TPD, NH3‐TPD, and TG were employed to investigate the effects of the modifying agents on the dispersion, reducibility, electronic properties, and acid–base properties of active metal species. Furthermore, the influence of K and Co modification on the CO2 hydrogenation activity and low‐carbon olefin selectivity of Fe/Al2O3 catalysts was explored. The results revealed that the introduction of K generated more basic sites and electron‐rich active metal centers in the catalyst, facilitating the adsorption and activation of CO2, while suppressing the hydrogenation of olefins and the formation of methane, thus improving the selectivity towards low‐carbon olefins. Co promoter facilitated the dispersion of Fe species, exposing more active sites and enhancing the FTS reaction activity, leading to more CO being converted into C2+ hydrocarbon products. Under the synergistic effect of K and Co, the CO2 conversion activity of the Fe‐based catalyst significantly increased, achieving a CO2 conversion rate of 37%, while the selectivity towards C2‐C4= increased to 31.9%.

Identity of the Silyl Ligand in an Iron Silyl Complex Influences Olefin Hydrogenation: An Experimental and Computational Study.

In this study, we explore the selective synthesis of iron silyl complexes using the reaction of an iron mesityl complex (MesCCC)FeMes(Py) with various hydrosilanes. These resulting iron silyl complexes, (MesCCC)Fe(SiH2Ph)(Py)(N2), (MesCCC)Fe(SiMe2Ph)(Py)(N2), and (MesCCC)Fe[SiMe(OSiMe3)2](Py)(N2), serve as effective precatalysts for olefin hydrogenation. The key to their efficiency in catalysis lies in the specific nature of the silyl ligand attached to the iron center. Experimental observations, supported by density functional theory (DFT) simulations, reveal that the catalytic performance correlates with the relative stability of dihydrogen and hydride species associated with each iron silyl complex. The stability of these intermediates is crucial for efficient hydrogen transfer during the catalytic cycle. The DFT simulations help to quantify these stability factors, showing a direct relationship between the silyl ligand's electronic and steric properties and the overall catalytic activity. Complexes with certain silyl ligands exhibit better performance due to the optimal balance between the stability and reactivity of the key active catalyst. This work highlights the importance of ligand design in the development of iron-based hydrogenation catalysts.

Data-Driven Insights into the Transition-Metal-Catalyzed Asymmetric Hydrogenation of Olefins.

The transition-metal-catalyzed asymmetric hydrogenation of olefins is one of the key transformations with great utility in various industrial applications. The field has been dominated by the use of noble metal catalysts, such as iridium and rhodium. The reactions with the earth-abundant cobalt metal have increased only in recent years. In this work, we analyze the large amount of literature data available on iridium- and rhodium-catalyzed asymmetric hydrogenation. The limited data on reactions using Co catalysts are then examined in the context of Ir and Rh to obtain a better understanding of the reactivity pattern. A detailed data-driven study of the types of olefins, ligands, and reaction conditions such as solvent, temperature, and pressure is carried out. Our analysis provides an understanding of the literature trends and demonstrates that only a few olefin-ligand combinations or reaction conditions are frequently used. The knowledge of this bias in the literature data toward a certain group of substrates or reaction conditions can be useful for practitioners to design new reaction data sets that are suitable to obtain meaningful predictions from machine-learning models.

Selective Hydrogenation Reaction: Utilizing a Microreactor for Continuous Flow Synthesis of Nickel Nanoparticles

Introduction: In this investigation, we employed a continuous flow reactor to synthesize nickel (Ni) nanoparticles exhibiting uniform size distribution and excellent stability. Our focus centered on exploring the impact of reactant dilution and flow rate on the synthesis process. Result: It was observed that the optimization of these parameters played a pivotal role in obtaining small-sized Ni nanoparticles. Specifically, we achieved successful synthesis using a solution of 0.00025 M NiCl2·6H2O and 0.002 M NaBH4, with a flow rate of 25 mL/h. The resulting Ni nanoparticles were effectively coated with the CTAB surfactant, as confirmed through thorough analysis using TEM and PSD techniques. Additionally, the interaction between the surfactant and nanoparticles was verified via FTIR analysis. We subjected them to high-pressure alkene hydrogenation to assess the catalytic activity of the synthesized Ni nanoparticles. Method: Encouragingly, the Ni nanoparticles exhibited excellent performance, producing hydrogenated products with high yields. Moreover, we capitalized on Ni nanoparticles' catalytic effect for synthesizing two natural compounds, brittonin A and dehydrobrittonin A. Remarkably, both compounds were successfully isolated in quantifiable yields. This synthesis protocol boasted several advantages, including low catalyst loading, omission of additives, broad substrate scope, straightforward product separation, and the ability to recover the catalyst up to eight times. In summary, this study effectively showcased the potential of continuous flow reactor technology in synthesizing stable and uniformly distributed nanoparticles. Conclusion: Additionally, it highlighted the effectiveness of Ni nanoparticles as catalysts in various chemical reactions. The findings from this study hold significant implications for developing more efficient and sustainable chemical synthesis protocols.

Hydrogenation of Alkenes Catalyzed by Mn(I) Alkyl Complexes Bearing NHC Phosphine Ligands

An efficient additive free hydrogenation of alkenes with molecular hydrogen is described. The pre‐catalyst is a well‐defined bench stable Mn(I) alkyl complex bearing a NHC phosphine ligand. These reactions are environmentally benign and atom economic, implementing an inexpensive, earth abundant non‐precious metal catalyst. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn‐alkyl bond to yield an acyl intermediate which undergoes rapid hydrogenolysis to form the active 16e Mn(I) hydride catalyst [Mn(PC‐iPr)(CO)2(H)]. A range of mono‐ and disubstituted alkenes were efficiently converted into alkanes in good to excellent yields. The hydrogenation requires a reaction temperature of 60 oC. In all cases, a catalyst loading of 1 mol % and a hydrogen pressure of 50 bar was applied. A mechanism based on DFT calculations is presented which is supported by experimental studies.

Contrasting Metallic (Rh0) and Carbidic (2D-Mo2C MXene) Surfaces in Olefin Hydrogenation Provides Insights on the Origin of the Pairwise Hydrogen Addition.

Kinetic studies are vital for gathering mechanistic insights into heterogeneously catalyzed hydrogenation of unsaturated organic compounds (olefins), where the Horiuti-Polanyi mechanism is ubiquitous on metal catalysts. While this mechanism envisions nonpairwise H2 addition due to the rapid scrambling of surface hydride (H*) species, a pairwise H2 addition is experimentally encountered, rationalized here based on density functional theory (DFT) simulations for the ethene (C2H4) hydrogenation catalyzed by two-dimensional (2D) MXene Mo2C(0001) surface and compared to Rh(111) surface. Results show that ethyl (C2H5*) hydrogenation is the rate-determining step (RDS) on Mo2C(0001), yet C2H5* formation is the RDS on Rh(111), which features a higher reaction rate and contribution from pairwise H2 addition compared to 2D-Mo2C(0001). This qualitatively agrees with the experimental results for propene hydrogenation with parahydrogen over 2D-Mo2C1-x MXene and Rh/TiO2. However, DFT results imply that pairwise selectivity should be negligible owing to the facile H* diffusion on both surfaces, not affected by H* nor C2H4* coverages. DFT results also rule out the Eley-Rideal mechanism appreciably contributing to pairwise addition. The measurable contribution of the pairwise hydrogenation pathway operating concurrently with the dominant nonpairwise one is proposed to be due to the dynamic site blocking at higher adsorbate coverages or another mechanism that would drastically limit the diffusion of H* adatoms.

Pd-Catalyzed Transfer Hydrogenation of Alkenes Using Tetrahydroxydiboron as the Sole Hydrogen Donor

AbstractTetrahydroxydiboron-mediated catalytic transfer hydrogenations have typically involved co-additives that, like tetrahydroxydiboron itself, are H atom donors. Herein we report an alkene transfer hydrogenation method with tetrahydroxydiboron as the sole source of H atoms. The reaction uses Pd(OAc)2 as a convenient putative colloid pre-catalyst, and cyclic monoethers are competent solvents. Highly efficient alkene deuteration is demonstrated using tetradeuteroxydiboron.

Hydrogen-Free Electrochemical Hydrogenation of Unactivated Alkenes under Nickel Catalysis

Hydrogen-Free Electrochemical Hydrogenation of Unactivated Alkenes under Nickel Catalysis

Zr(OH)4‐Catalyzed Semi‐Hydrogenation of Phenylacetylene with Terminal Zr‐O‐H as Active Site: Inactive for Free Styrene

In the field of industrial semi‐hydrogenation of trace alkynes amidst alkene feedstocks, the pivotal challenge lies in circumventing the hydrogenation of alkenes. Herein, we present Zr(OH)4 as an innovative catalyst for the semi‐hydrogenation of phenylacetylene, demonstrating remarkable selectivity towards styrene (>96%), while exhibiting inactivity towards free styrene. Notably, Zr(OH)4 achieves a 95% conversion of quasi‐industry 1 mol% phenylacetylene within styrene, with a mere 0.44% styrene loss. Experimental and theoretical results confirm both terminal Zr‐O‐H and bridge Zr‐O‐H can dissociate H2, while the terminal Zr‐O‐H plays a crucial role on activating phenylacetylene through the sequential hydrogenation process of C6H5C≡CH→C6H5C=CH2→C6H5CH=CH2. The high rate of phenylacetylene removal is attributed to its strong adsorption capacity, while Zr(OH)4 has a significantly weaker adsorption capacity for styrene.

Zr(OH)4-Catalyzed Semi-Hydrogenation of Phenylacetylene with Terminal Zr-O-H as Active Site: Inactive for Free Styrene.

In the field of industrial semi-hydrogenation of trace alkynes amidst alkene feedstocks, the pivotal challenge lies in circumventing the hydrogenation of alkenes. Herein, we present Zr(OH)4 as an innovative catalyst for the semi-hydrogenation of phenylacetylene, demonstrating remarkable selectivity towards styrene (>96 %), while exhibiting inactivity towards free styrene. Notably, Zr(OH)4 achieves a 95 % conversion of quasi-industry 1 mol % phenylacetylene within styrene, with a mere 0.44 % styrene loss. Experimental and theoretical results confirm both terminal Zr-O-H and bridge Zr-O-H can dissociate H2, while the terminal Zr-O-H plays a crucial role on activating phenylacetylene through the sequential hydrogenation process of C6H5C≡CH→C6H5C=CH2→C6H5CH=CH2. The high rate of phenylacetylene removal is attributed to its strong adsorption capacity, while Zr(OH)4 has a significantly weaker adsorption capacity for styrene.

Enantioselective Total Synthesis of (+)‐Propolisbenzofuran B†

Comprehensive SummaryThe first catalytic asymmetric total synthesis of (+)‐propolisbenzofuran B, enabled by a highly enantioselective rhodium‐catalyzed hydrogenation of a tetrasubstituted olefin, was described. Other noteworthy aspects include the construction of the central hydrodibenzo[b,d]furan core through a sequence of Zn(II)‐mediated regioselective benzofuran formation and Dieckmann condensation, as well as C‐H oxidations, involving a visible light‐induced Fe(III)‐catalyzed benzylic C(sp3)‐H oxidation. Additionally, the absolute configuration was confirmed by X‐ray analysis of a carbonate intermediate.