Active Hydrogenation Catalysts Research Articles

Supported Ni nanoparticles derived from MOFs as a highly active catalyst for benzene hydrogenation

Metal-organic frameworks (MOFs) is easy to agglomerate at high temperature, resulting in the rapid collapse of the MOFs structure and the aggregation of metal sites. In this paper, Al2O3 is used as the support material to support the in-situ synthesis of Ni-MOF on the surface, and the metal Ni nanoparticles are successfully fixed on the Al2O3. The results showed that both Ni/Ni-MOF-300 and Ni/NA-MOF-300 catalysts reduced at 300 ℃ have good hydrogenation activity of benzene, and Ni/Ni-MOF-450 catalysts reduced at 450 ℃ formed huge Ni aggregates, which significantly reduced the hydrogenation activity of benzene. However, Ni/NA-MOF-450 catalyst reduced at 450 ℃ can effectively resist the metal Ni agglomeration caused by the collapse of MOFs structure at high temperature, and has better hydrogenation activity of benzene.

Nitrogen species from Spirulina platensis derived bio-oil enhance catalytic activity of cobalt catalysts for hydrogenation

High nitrogen content in Spirulina platensis-derived bio-oil is a highly undesirable feature in upgrading of bio-oil to biofuel via hydrodeoxygenation. However, the nitrogen species could be potentially used as dopant for tailoring the catalytic behaviors of metallic sites in heterogeneous catalysts. In this study, the nitrogen species in the bio-oil from hydrothermal carbonization (HTC) of Spirulina platensis was used to modify Co-based catalyst for enhancing their catalytic activity for hydrogenation of o-chloronitrobenzene (o-CNB). The results showed that the introduction of N species not only promoted dispersion of Co particles via formation of Co–N sites, but also generated extra pores and significantly increased H2 uptake. The abundant Co–N sites, high dispersion of Co and higher surface area of N-doped catalyst (CoFeAl–N) jointly contributed to the enhanced catalytic activity for hydrogenation of o-CNB, achieving the yield of 90.3% for o-chloroaniline (o-CA) and lowering the activation energy from 63.0 kJ mol−1 (with N-free CoFeAl catalyst) to 55.1 kJ mol−1. The effectiveness of introducing nitrogen for enhancing catalytic activity for hydrogenation of o-CNB was also confirmed in the experiments for doping Co/Al2O3 (prepared via impregnation) and CoAl (prepared via co-precipitation) catalysts with the Spirulina platensis derived bio-oil.

Thermally stable Ni foam-supported inverse CeAlOx/Ni ensemble as an active structured catalyst for CO2 hydrogenation to methane

Nickel is the most widely used inexpensive active metal center of the heterogeneous catalysts for CO2 hydrogenation to methane. However, Ni-based catalysts suffer from severe deactivation in CO2 methanation reaction due to the irreversible sintering and coke deposition caused by the inevitable localized hotspots generated during the vigorously exothermic reaction. Herein, we demonstrate the inverse CeAlOx/Ni composite constructed on the Ni-foam structure support realizes remarkable CO2 methanation catalytic activity and stability in a wide operation temperature range from 240 to 600 °C. Significantly, CeAlOx/Ni/Ni-foam catalyst maintains its initial activity after seven drastic heating-cooling cycles from RT to 240 to 600 °C. Meanwhile, the structure catalyst also shows water resistance and long-term stability under reaction condition. The promising thermal stability and water-resistance of CeAlOx/Ni/Ni-foam originate from the excellent heat and mass transport efficiency which eliminates local hotspots and the formation of Ni-foam stabilized CeAlOx/Ni inverse composites which effectively anchored the active species and prevents carbon deposition from CH4 decomposition.

Sustainable Production of Chemicals via Hydrotreating of CO2 and Biomass Derived Molecules Using Heterogeneous Noble Metal Oxide Catalysts

AbstractThe noble metals are widely used in heterogeneous catalysis and automobile industry. The limited natural sources and high cost of noble metals dictates improving the efficiency of modern industry. This review considers the applications of noble metal oxide as potential solutions to the sustainability issues, including biomass conversion, CO2 capture and conversion, green fuel production, etc. Noble metal oxides with their different compositions (monometallic and bimetallic) and structures exhibit a wide range of properties in heterogeneous catalysis. Although platinum metals in an oxidized form may not be the most common choice in hydroprocesses; recently, there have been studies indicating that they were highly active and selective catalysts in hydrogenation and hydrogenolysis. This review outlines the most established noble metal oxide catalysts used in hydrogenation catalysis and shed the light on the relation of noble metal oxide species to catalyst selectivity based on state‐of‐the‐art techniques. Finally, the perspectives on the application of noble metal oxide catalysts to produce value‐added chemicals are discussed.

Nickel Carbide Nanoparticle Catalyst for Selective Hydrogenation of Nitriles to Primary Amines.

Despite its unique physicochemical properties, the catalytic application of nickel carbide (Ni3 C) in organic synthesis is rare. In this study, we report well-defined nanocrystalline Ni3 C (nano-Ni3 C) as a highly active catalyst for the selective hydrogenation of nitriles to primary amines. The activity of the aluminum-oxide-supported nano-Ni3 C (nano-Ni3 C/Al2 O3 ) catalyst surpasses that of Ni nanoparticles. Various aromatic and aliphatic nitriles and dinitriles were successfully converted to the corresponding primary amines under mild conditions (1 bar H2 pressure). Furthermore, the nano-Ni3 C/Al2 O3 catalyst was reusable and applicable to gram-scale experiments. Density functional theory calculations suggest the formation of polar hydrogen species on the nano-Ni3 C surface, which were attributed to the high activity of nano-Ni3 C towards nitrile hydrogenation. This study demonstrates the utility of metal carbides as a new class of catalysts for liquid-phase organic reactions.

Ni-Cu and Ni-Co-Modified Fly Ash Zeolite Catalysts for Hydrodeoxygenation of Levulinic Acid to γ-Valerolactone.

Monometallic (Ni, Co, Cu) and bimetallic (Ni-Co, Ni-Cu) 10-20 wt.% metal containing catalysts supported on fly ash zeolite were prepared by post-synthesis impregnation method. The catalysts were characterized by X-ray powder diffraction, N2 physisorption, XPS and H2-TPR methods. Finely dispersed metal oxides and mixed oxides were detected after the decomposition of the impregnating salt on the relevant zeolite support. Via reduction intermetallic, NiCo and NiCu phases were identified in the bimetallic catalysts. The catalysts were studied in hydrodeoxygenation of lignocellulosic biomass-derived levulinic acid to γ-valerolactone (GVL) in a batch system by water as a solvent. Bimetallic, 10 wt.% Ni, and 10 wt.% Cu or Co containing fly ash zeolite catalysts showed higher catalytic activity than monometallic ones. Their selectivity to GVL reached 70-85% at about 100% conversion. The hydrogenation activity of catalysts was found to be stronger compared to their hydration ability; therefore, the reaction proceeds through formation of 4-hydroxy pentanoic acid as the only intermediate compound.

Chiral Bifunctional NHC–Guanidine Ligands for Asymmetric Hydrogenation

AbstractWe report the synthesis of chiral N-heterocyclic carbene/guanidine bifunctional ligands from readily available amino alcohols. The resulting chiral bifunctional copper(I) complexes are active catalysts in an asymmetric hydrogenation of ketones. We show that the chiral linker unit can be employed for the transfer of stereoinformation.

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

КАТАЛИЗ ГИДРИРОВАНИЯ АРОМАТИЧЕСКИХ СОЕДИНЕНИЙ: ИСТОРИЯ И СОВРЕМЕННОЕ СОСТОЯНИЕ. ЧАСТЬ 2. ГИДРИРОВАНИЕ ПОЛИЯДЕРНЫХ АРОМАТИЧЕСКИХ УГЛЕВОДОРОДОВ, АЗОТ- И КИСЛОРОДЗАМЕЩЕННЫХ АРЕНОВ

The review is devoted to hydrogenation processes of aromatic substrates differing in reactivity using catalysts of different activity. The global trend in this area is the search for more active and selective heterogeneous catalysts for hydrogenation of the aromatic ring, both for industrial processes and in laboratory practice. An analysis of literature data on the hydrogenation of polynuclear aromatic hydrocarbons, phenol, aniline and their derivatives, as well as arenes substituted with a functional group, is presented. Various types of catalysts for the hydrogenation of an aromatic ring, the patterns of the process depending on the structure of the substrate and reaction conditions, the nature of the active phase and the catalyst support are considered.

Multi-metal catalysts for selective furfural hydrogenation: Toward biomass valorisation

The research presented here focuses on the design of non-noble transition metal-based bimetallic catalysts, prepared via a green sol-gel process (the urea-glass route), which leads to well-defined (in composition and size) and crystalline nanoparticles, with high surface area. The potential of these tailor-made catalysts for biomass-related model reactions is also presented. In particular, carbon supported Ni, Ni3Fe, Ni0.5Fe0.5, Ni0.5Fe0.5/Fe3C and Ni0.35Fe0.65/NiFe2O4 nanoparticles were synthesized and tested as-prepared, with no need for post-synthesis purification, activation, or co-catalysts addition. Results showed that these catalysts are active in the liquid-phase hydrogenation of furfural (FUR), with almost full conversion with Ni° catalyst, at 170 °C after 22 h, under 4 MPa hydrogen pressure, obtaining the highest yield towards tetrahydrofurfuryl alcohol (THFA) of 85%. More interesting, the incorporation of Fe, to form NiFe alloys, modifies the hydrogenating capacity of the catalyst, provoking a change in the selectivity pattern, from tetrahydrofurfuryl alcohol (THFA), obtained as the only product with Ni° nanoparticles, to furfuryl alcohol (FFA). Thus, high FFA and THFA yields can be obtained by modifying the nature of the metallic phase of samples synthesized with the urea-glass route, demonstrating the potential of this methodology for the preparation of active and selective catalysts for liquid-phase FUR hydrogenation.

Novel Metallomacrocyclic Carboxamide Mn(II) Complexes as Efficient Catalysts for the Transfer Hydrogenation of Ketones

AbstractHerein, we present the first metallomacrocyclic Mn(II) complexes as efficient catalysts for the transfer hydrogenation of ketones. The dinuclear Mn(II) complexes [Mn2(L1–L4)2Cl2] (Mn1–Mn4), were synthesised in good yields by reacting MnCl2 ⋅ 4H2O with the ligands N,N′‐(1,4‐phenylene)dipicolinamide (L1), N,N′‐(1,2‐phenylene)dipicolinamide (L2), N,N′‐(4‐methoxy‐1,2‐phenylene)dipicolinamide (L3) and N,N′‐(4,5‐dimethyl‐1,2‐phenylene)dipicolinamide (L4). Structural characterization of the resulting Mn(II) complexes was achieved using FT‐IR spectroscopy, mass spectrometry, magnetic moment measurements, elemental analysis, and single‐crystal X‐ray diffraction for Mn2. The solid‐state structure of complex Mn2 reveals a dinuclear Mn(II) core, in which the metal coordination sphere consists of two bidentate, K2(N−O) bridging L2 units and two chlorido ligands to give a distorted octahedral geometry. The Mn(II) complexes (Mn1–Mn4) were quite active catalysts for the transfer hydrogenation of ketones displaying turnover numbers (TON) of up to 2633, which is comparable to those of well‐established Mn(I) catalysts. The new Mn(II) complexes also efficiently hydrogenated a number of aromatic, heterocyclic, functionalized and aliphatic ketones. More significantly, cheaper, and readily available hydrogen sources like ethanol also gave decent catalytic activities in the transfer hydrogenation reactions.

CO2 hydrogenation using MOFs encapsulated PdAg nano-catalysts for formate production

Catalytic hydrogenation of CO2 for the production of formic acid/formate, a valuable commodity and renewable hydrogen carrier, is a promising strategy to achieve an economic andsustainable CO2-mediated hydrogen energy cycle. The rational design of highly active and stable heterogeneous catalysts for CO2 hydrogenation in gas–liquid-solid phase still remains challenging. In this work, we report a series of dual-function catalysts namely PdAg@MIL-101-PEI, where PdAg alloy nanoparticles (NPs) for hydrogen activation and dissociation are encapsulated into MIL-101 supports tethered with CO2 adsorption agent polyethyleneimine (PEI). The optimal PdAg@MIL-101-PEI catalyst displays exceptional performance for CO2 hydrogenation, affording a high turnover number (TON) of 4968 at 120 °C under 8 MPa in 2 h. Thermodynamic and kinetic studies illustrate that Ag incorporation and PEI functionalization dramatically reduce the activation energy barrier of PdAg@MIL-101-PEI catalyst for CO2 hydrogenation. Furthermore, the optimal PdAg@MIL-101-PEI catalyst demonstrates outstanding structural stability and reusability over multiple catalytic cycles. We also propose a reaction mechanism for CO2 hydrogenation through in situ DRIFTS study.

Construction of Highly Active and Selective Molecular Imprinting Catalyst for Hydrogenation.

Surface molecular imprinting (MI) is one of the most efficient techniques to improve selectivity in a catalytic reaction. Heretofore, a prerequisite to fabricating selective catalysts by MI strategies is to sacrifice the number of surface-active sites, leading to a remarkable decrease of activity. Thus, it is highly desirable to design molecular imprinting catalysts (MICs) in which both the catalytic activity and selectivity are significantly enhanced. Herein, a series of MICs are prepared by sequentially adsorbing imprinting molecules (nitro compounds, N) and imprinting ligand (1,10-phenanthroline, L) over the copper surface of Cu/Al2O3. The resulting Cu/Al2O3-N-L MICs not only offer promoted catalytic selectivity but also enhance catalytic activity for nitro compounds hydrogenation by an creating imprinting cavity derived from the presorption of N and forming new active Cu-N sites at the interface of the copper sites and L. Characterizations by means of various experimental investigations and DFT calculations disclose that the molecular imprinting effect (promoted activity and selectivity) originates from the formation of new active Cu-N sites and precise imprinting cavities, endowing promoted catalytic selectivity and activity on the hydrogenation of nitro compounds.

Acetone hydrogenation over face-centered cubic and hexagonal close-packed cobalt

Acetone hydrogenation is employed for investigating the structure sensitivity of H2 activation over cobalt catalysts while the produced isopropanol garners increasing interest in the sustainable energy context e.g. as H2 storage material and fuel for direct fuel cells. Both hexagonal close-packed (hcp) and face-centered cubic (fcc) Co can produce isopropanol with 100% selectivity below 150 °C with the reaction proceeding almost ten times faster over hcp Co. Hydrogenation rates are even higher over an hcp Co/Co3O4 composite which remains highly selective to isopropanol despite that Co3O4 yields mostly mesityl oxide and related products. The superior performance of hcp Co and its composite are attributed to efficient generation of atomic H on the metal and the presence of stronger sites for acetone activation on XRD-amorphous phases that are formed during reduction of the Co3O4 precursor at 250 °C and 400 °C. These findings provide insight into the optimum structural design of highly active and selective low-temperature cobalt hydrogenation catalysts.

Highly Selective Conversion of Carbon Dioxide to Methanol through a Cu−ZnO−Al2O3−ZrO2/Cu−MOR Tandem Catalyst

AbstractMethanol formation from CO2 hydrogenation attracts great attention in view of utilization of carbon resources. However, CO2 transformation to methanol is challenging because of the thermodynamic equilibrium restriction and water‐caused catalyst deactivation. It is desired, therefore, to develop highly active, selective and stable catalysts for CO2 hydrogenation to methanol. Herein, we propose a novel tandem catalyst composed of Cu−ZnO−Al2O3−ZrO2 (CZAZ) and Cu−MOR for highly selective conversion of CO2 to methanol. During CO2 hydrogenation by the CZAZ catalyst, the by‐product methane is continuously transformed to methanol through reaction with water via the Cu−MOR catalyst, thus enhancing CO2 conversion and methanol selectivity. Under mild reaction conditions (200 °C and 3.0 MPa), high CO2 conversion (40.7 %) and methanol selectivity (97.6 %) are achieved, outperforming state‐of‐the‐art CO2 hydrogenation catalysts. Further, water‐caused deactivation of the catalyst through aggregation and densification is suppressed owing to water consumption via methane oxidation to methanol, validating a high CZAZ/Cu−MOR tandem catalyst stability.

A Highly Active and Reusable Multicomponent high Entropy Metal Oxide Catalyst for Nitroarenes Hydrogenation

It is well known that multicomponent catalysts can improve catalytic performance, however their rational design and precise control of catalytic activities by varying the composition of the elements is challenging. Herein, we present a facile and scalable synthetic strategy for production of senary and septenary metal oxide nanoparticles with a chemical composition of MSbOx and MSb2Ox (M: Fe, Ni, Co, Cu, and Zn). All samples were formed in a tetragonal crystal structure with space group 136 and crystallographic symmetry P42/mnm while the details of their constituent unit cells are different, belonging to rutile or trirutile structures. These nanocomposites have an oxygen vacancy-rich construction with uniform elemental distributions that produce various surface functionalities. They showed instantaneous hydrogenation catalytic performance for reduction of 4-nitrophenol to 4-aminophenol at room temperature. Among our samples, the senary catalyst with MSbOx chemical composition showed better durability and reusability owning to its morphological and microstructural properties. It showed 100% conversion of 4-nitrophenol to 4-aminophenol within 4 min at the 18th run without any by-products.

COMPARATIVE HYDROGENATION OF BENZENE DEPOSITED BY RHODIUM AND PLATINUM CATALYSTS

Rhodium and platinum, as the most active catalysts for hydrogenation of the aromatic ring, were applied to γ-Al2O3 under comparative conditions and their activities during hydrogenation of benzene in hexane were compared. It is shown that under the studied conditions, rhodium exhibits greater activity than platinum during the hydrogenation of benzene in hexane at 80 oC and 40 atm. It is more active than platinum when hydrogenating benzene in hexane at 80o C and 40 atm.

Pd Nanoparticles Supported on N-Incorporated Hybrid Organosilica as an Active and Selective Low-Temperature Phenol Hydrogenation Catalyst

A heterogeneous Pd-NPMO hybrid-silica catalyst is synthesized and its application for aqueous phase selective hydrogenation of phenol to cyclohexanone at near ambient temperature (40 °C) and under atmospheric hydrogen pressure is demonstrated. The homogeneously distributed Pd nanoparticles on N-bridged hybrid mesoporous organosilica showed remarkable activity and selectivity for cyclohexanone compared to the unmodified Pd-SBA-15 catalyst. Control experiments strongly claim the role of nitrogen domains in the organic framework of hybrid silica support in stabilizing small Pd nanoparticles and possibly modifying the Pd sites responsible for catalysis to activate the substrate molecules in water. The hybrid silica catalyst was stable and reused several times without any significant drop-in activity, proving the heterogeneity of the bifunctional Pd catalyst. Based on the density functional theory study and experimental interventions, a possible reaction mechanism for the low-temperature phenol hydrogenation explaining the role of organic domains in the hybrid-silica framework is proposed.

A Highly Active Nickel Catalyst for the Selective Hydrogenation of Functionalized Nitroarenes

AbstractThe catalytic hydrogenation of nitroarenes using hydrogen gas as reducing agent to form substituted aniline derivates is an important reaction in industry and academic research. Here, we report on the nitroarene hydrogenation capability of a nanostructured nickel catalyst synthesized from a nickel salen complex and a commercially available porous silica support. Our catalyst allows the selective hydrogenation of nitroarenes under mild conditions while tolerating various functional groups and hydrogenation‐sensitive examples such as iodine, nitrile or olefinic groups. The use of the nickel salen complex as metal precursor is crucial for the high activity and selectivity observed.

AuFe3@Pd/γ-Fe2O3 Nanosheets as an In Situ Regenerable and Highly Efficient Hydrogenation Catalyst

Heterogenous Pd catalysts play a pivotal role in the chemical industry; however, it is plagued by S2- or other strong adsorbates inducing surface poisoning long term. Herein, we report the development of AuFe3@Pd/γ-Fe2O3 nanosheets (NSs) as an in situ regenerable and highly active hydrogenation catalyst. Upon poisoning, the Pd monolayer sites could be fully and oxidatively regenerated under ambient conditions, which is initiated by •OH radicals from surface defect/FeTetra vacancy-rich γ-Fe2O3 NSs via the Fenton-like pathway. Both experimental and theoretical analyses demonstrate that for the electronic and geometric effect, the 2-3 nm AuFe3 intermetallic nanocluster core promotes the adsorption of reactant onto Pd sites; in addition, it lowers Pd's affinity for •OH radicals to enhance their stability during oxidative regeneration. When packed into a quartz sand fixed-bed catalyst column, the AuFe3@Pd/γ-Fe2O3 NSs are highly active in hydrogenating the carbon-halogen bond, which comprises a crucial step for the removal of micropollutants in drinking water and recovery of resources from heavily polluted wastewater, and withstand ten rounds of regeneration. By maximizing the use of ultrathin metal oxide NSs and intermetallic nanocluster and monolayer Pd, the current study demonstrates a comprehensive strategy for developing sustainable Pd catalysts for liquid catalysis.