Selective Catalytic Hydrogenation Research Articles

Lignin-tailored fabrication of Ni single atom catalyst with Ni-N3 active site for efficient and selective catalytic transfer hydrogenation of lignin-derived aldehydes

Developing sustainable catalytic processes for catalytic transfer hydrogenation (CTHDO) of lignin-derived aldehydes to renewable fuels and chemicals is essential for scale valorization of vast underused lignin. Herein, the work contributes to the efficient and selective vanillin (VAN) CTHDO process using formic acid (FA) as the H-donor over a novel lignin-coordinated N-anchoring Ni single-atom catalyst (Ni SAs-N@LC). Ni SAs-N@LC was fabricated through facile pyrolysis of lignin-Ni/Zn complex mixed with melamine, in which lignin localized the Ni atoms through its negatively charged groups (e.g. phenolic OH) and the dispersed Ni atoms were further anchored by the N-doped carbon support to form Ni-N3 active structure. DFT calculations revealed that the Ni-N3 structure preferentially adsorbed the –CHO end of VAN and endowed the catalyst with superior hydrogen evolution capacity. Therefore, Ni SAs-N@LC exhibited outstanding catalytic performance (98.93% of VAN conversion and 97.3% of 2-methoxy-4-methylphenol selectivity) which was significantly higher than two reference catalysts Ni NPs@LC (without N-anchoring) and Ni@C (without lignin coordination and N-anchoring) as well as the previously reported Ni-based catalysts. Moreover, Ni SAs-N@LC presented excellent feasibility to the CTHDO of a wide range of lignin-derived aldehydes and exhibited superior cycling durability in FA system owing to its acid resistance property. Consequently, this work provides a facile preparation method for atomically dispersed biomass-based catalysts and further demonstrates its favorable applicability in the CTHDO of lignin-derived aldehydes.

Synthesis of Disecondary Aromatic Diols

The synthesis of disecondary aromatic diols (the main precursors for divinyl aromatic monomers) was carried out. The optimal conditions for the preparation of these diols by selective catalytic hydrogenation of aromatic diketones in the presence of Raney nickel and by reduction of these diketones by sodium borohydride were established. It was demonstrated that sodium borohydride reduction afforded the pure diols under mild and relatively safe conditions (in the systems of CHCl3–PEG400–H2O, at room temperature and atmospheric pressure).

MIL-101(Cr) supported Pt and Au-Pt composites as active catalysts for the selective hydrogenation of nitrobenzene under mild reaction conditions

In this study, we report the successful synthesis of monometallic Pt(2 wt.%)/MIL-101(Cr) and bimetallic Au(1 wt.%)-Pt(1 wt.%)/MIL-101(Cr) catalysts with low dimension MeNPs by the double-solvent (DS) method. The catalysts were characterized by powder X-ray diffraction (PXRD), N2 sorption analysis (BET), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), and transmission electron microscopy (TEM). The characterization results demonstrated the presence of well-dispersed Pt and Au-Pt nanoparticles (2.9 and 2.7 nm, respectively), located mainly inside the pores of MIL-101(Cr). The stronger interaction of Au-Pt NPs with the support compared to Pt NPs was demonstrated by H2-TPR and XPS, which proved the existence of charge exchange between Pt NPs and Cr from MIL-101 in the case of Au(1 wt%)-Pt(1 wt%)/MIL-101(Cr), but not in the case of Pt(2 wt%)/MIL-101(Cr). The composite materials were tested in the catalytic selective hydrogenation of nitrobenzene to aniline in liquid phase under mild conditions (low temperature, low hydrogen pressure), and in the presence of a biomass-derived non-toxic solvent (ethanol). The bimetallic Au(1 wt%)-Pt(1 wt%)/MIL-101(Cr) catalyst showed superior catalytic activity as compared to the monometallic Pt(2 wt%)/MIL-101(Cr) catalyst. This is due to the synergetic effect between the two metals as demonstrated by the projected density of states studies.

Surfactant-free synthesis of nanostructured palladium materials under mild conditions and their highly catalytic selective hydrogenation

Nanostructured palladium (Pd) materials are highly efficient noble metal catalysts in various fields, but developing a simple and mild strategy to prepare Pd nanomaterials with high activity and selectivity still remains a big challenge. In this study, uniform-sized Pd popcorn-like nanospheres (PNSs) were successfully synthesized by the slow reduction of Pd(OAc)2 in anhydrous methanol under ambient conditions in the dark without any surfactant, additional reductant and support. The obtained Pd PNSs have rough surface with the average diameter of approximately 140 nm, and are composed of many smaller PNSs with the average size of about 12 nm. Pd PNSs have excellent catalytic performance in the hydrogenation of 4-nitrobenzaldehyde to 4-aminobenzaldehyde under mild conditions. Specifically, using the as-prepared Pd PNSs as catalyst, the 98 % conversion of 4-nitrobenzaldehyde and 98 % selectivity to 4-aminobenzaldehyde can be achieved within 1.5 h at 35°C under atmospheric pressure. After three recycling, the Pd PNSs can still maintain highly catalytic activity and selectivity. The very simple strategy developed here will be a valuable supplement to the methodology for the surfactant-free fabrication of other surface-active metallic nanomaterials for advanced applications.

Copper‐based nanocatalysts toward chemoselective hydrogenation reaction

AbstractCu‐based catalysts are widely used in various heterogeneous catalytic reaction systems, the precise control of their electronic structure is an intrinsic requirement for the rational design of metal catalysts, and it is also an important basis for clarifying their structure‐activity relationships. Changing the electronic structure of Cu‐based catalysts is an important way to improve the catalytic hydrogenation performance of Cu‐based catalysts by controlling the adsorption intensity between the reaction adsorbate and the active center. In this paper, the application of selective hydrogenation of Cu‐based catalysts is reviewed, with a special emphasis on the selective catalytic hydrogenation reduction of p‐nitrostyrene and CO2. This review particularly emphasizes the application of Cu‐based catalysts in the field of selective hydrogenation and discusses the influence of their different properties on selective hydrogenation performance.

Ru and Ruδ+ synergistic catalysis efficiently promotes 2,2,6,6-Tetramethyl-4-Piperidone hydrogenation for 2,2,6,6-Tetramethyl-4-Piperidinol preparation

The catalytic hydrogenation of nitrogen-containing heterocyclic compounds is a crucial process; however, nitrogen removal severely restricts product selectivity. Consequently, this study utilized a simple heat treatment method to synthesize ruthenium (Ru)-based catalysts supported on N-doped activated carbon for application in the selective catalytic hydrogenation of 2,2,6,6-Tetramethyl-4-piperidone (TAA). The results show that the selectivity of 2,2,6,6-Tetramethyl-4-piperidinol (TMP) is as high as 99.87 % under the premise of almost complete TAA reaction. The catalyst was characterized using N2-physisorption-desorption, XRD, TEM, Raman, XPS, ICP-OES, and H2-TPR techniques. N-doped activated carbon introduced numerous defect sites to the catalyst, improved the surface wettability of the activated carbon support, provided abundant active metal anchoring sites, which results in highly uniform dispersion of Ru nanoparticles (NPs) on the carrier surface, forms relatively smaller nanoparticles, and enhances the catalyst's activity. Additionally, a strong interaction exists between the active metal Ru and N-doped activated carbon support. Thus, the transfer of free electrons from Ru to N species was facilitated, and the relative content of Ruδ+ in the catalyst was increased, and the synergistic effect between Ru and Ruδ+ contributes to improving the catalyst's performance. This work holds significant potential for controlling the selectivity of nitrogen-containing heterocyclic compounds in the catalytic hydrogenation process.

Continuous Hydrogenation of Nitriles to Primary Amines with High Selectivity in Flow by Using Raney Cobalt

AbstractPrimary amines produced by selective catalytic hydrogenation of cyano compounds are widely used as basic chemicals, but due to the complexity of the hydrogenation mechanism and the inefficient mass transfer of the intermittent reaction, the process tends to produce secondary and tertiary amines as undesirable by‐products. In this research, a continuous hydrogenation system employing a micropacked‐bed reactor (μPBR) was established for the catalytic hydrogenation of 3‐ethylaminopropionitrile (3‐EAPN) to synthesize N‐ethyl‐1,3‐propanediamine (3‐EAPA). Under optimal experimental conditions using Raney cobalt as a catalyst, complete conversion of 3‐EAPN was achieved, and a high selectivity of 99.6 % for the primary amine (3‐EAPA) was obtained. On this basis, the system was extended with other cyano compounds of different structures as hydrogenation substrates, demonstrating the general applicability of this continuous hydrogenation system by using Raney cobalt as a catalyst in a μPBR for the hydrogenation of various nitriles.

CaH2-Assisted Molten Salt Synthesis of Zinc-Rich Intermetallic Compounds of RhZn13 and Pt3Zn10 for Catalytic Selective Hydrogenation Application

Zinc-included intermetallic compound catalysts of RhZn, PtZn, and PdZn with a molar ration of Zn/metal = 1/1, which are generally prepared using a hydrogen reduction approach, are known to show excellent catalytic performance in some selective hydrogenations of organic compounds. In this study, in order to reduce the incorporated mounts of the expensive noble metals, we attempted to prepare zinc-rich intermetallic compounds via a CaH2-assisted molten salt synthesis method with a stronger reduction capacity than the common hydrogen reduction method. X-ray diffraction results indicated the formation of RhZn13 and Pt3Zn10 in the samples prepared by the reduction of ZnO-supported metal precursors. In a hydrogenation reaction of p-nitrophenol to p-aminophenol, the ZnO-supported RhZn13 and Pt3Zn10 catalysts showed a higher selectivity than the RhZn/ZnO and PtZn/ZnO catalysts with the almost similar conversions. Thus, it was demonstrated that the zinc-rich intermetallic compounds of RhZn13 and Pt3Zn10 could be superior selective hydrogenation catalysts compared to the conventional intermetallic compound catalysts of RhZn and PtZn.

Graphene Chainmail Shelled Dilute Ni─Cu Alloy for Selective and Robust Aqueous Phase Catalytic Hydrogenation.

Cost-effective non-noble metal-based catalysts for selective hydrogenation with excellent activity, selectivity, and durability are still the holy grail. Herein, an oxygen-doped carbon (OC) chainmail encapsulated dilute Cu-Ni alloy is developed by simple pyrolysis of Cu/Ni-metal-organic framework. The CuNi0.05@OC catalyst displays superior performance for atmospheric pressure transfer hydrogenation of p-chloronitrobenzene and p-nitrophenol, and for hydrogenation of furfural, all in water and with exceptional durability. Comprehensive characterizations confirm the close interactions between the diluted Ni sites, the base Cu, and optimized three-layered graphene chainmail. Theoretical calculations demonstrate that the properly tuned lattice strain and Schottky junction can adjust electron density to facilitate specific adsorption on the active centers, thus enhancing the catalytic activity and selectivity, while the OC shell also offers robust protection. This work provides a simple and environmentally friendly strategy for developing practical heterogeneous catalysts that bring the synergistic effect into play between dilute alloy and functional carbon wrapping.

Nanocatalysts Based on Ni Nanoparticles in Functionalized Ionic Liquids for Chemoselective Hydrogenation and Transfer Hydrogenation of α,β‐unsaturated Carbonyl Compounds

AbstractFor the development of catalytically active and selective Ni nanoparticle (NP) catalysts both the choice of the synthesis method and the selection of stabilizer are key parameters. A series of Ni NPs were synthesized in various ionic liquids (Ni/ILs) and applied as catalysts for the chemoselective reduction of 2‐cyclohexen‐1‐one (1), as a representative of the group of α,β‐unsaturated carbonyl compounds with industrial relevance. The Ni/ILs systems were found to be efficient catalysts for the selective hydrogenation of 1 to cyclohexanone (2) under quite mild reaction conditions (130‐170 °C, 10 bar H2, 1/Ni molar ratio of 100/1), achieving high conversions in a short reaction time (1 h). The oxidized counterparts (Ni‐NiO/ILs) showed to be active for the selective catalytic transfer hydrogenation (CTH) of 1 to 2‐cyclohexen‐1‐ol (3) with 2‐propanol, also under mild reaction conditions (150 °C, 48 h, 1/Ni ratio of 50/1).

Catalytic synthesis of renewable 2-methylfuran from furfural

The efficient catalytic selective hydrogenation of furfural to produce 2-methylfuran was accomplished through the introduction of a small quantity of hydroquinone over a monometallic catalyst comprising solely of Co and its oxides.

Selective catalytic hydrogenation of 5-hydroxymethylfurfural over silica supported FeCoNiCuRu high-entropy alloy nanoparticles

A simple organic ligand chelate-assisted thermal-reduction method provides a universal strategy for generating high-entropy alloy (HEA) nanoparticles catalysts with uniformly dispersed particles for efficient catalytic hydrogenation.

Construction of Cu–Ru bimetallic catalyst for the selective catalytic transfer hydrogenation of carbonyl (C[dbnd]O) in biomass-derived compounds

The catalytic transfer hydrogenation (CTH) of levulinate ester to γ-valerolactone is one of the important reactions for production of renewable fuels from biomass. An efficient and robust bimetallic Cu–Ru catalyst were developed for the hydrogenation of biomass-derived ethyl levulinate to γ-valerolactone. A series of bimetallic catalysts were prepared and characterized in detail. Subsequently, the as-prepared catalysts were evaluated in the hydrogenation system of ethyl levulinate. The results showed that Cu–Ru/ZrO2–SO3–SiO2-450 catalyst provided 100 % GVL yield in 12 h at 180 °C. Meanwhile, it also exhibited high catalytic hydrogenation activity for the various biomass-derived carbonyl compounds. The structure-reactivity relationship of catalysts was investigated in detail, and the results show the interaction between support and metal sites played an important role in the hydrogenation activity. The sulfur species could tune the electronic states of metallic sites to gain optimal activity. Besides, the Cu–Ru/ZrO2–SO3–SiO2-450 catalyst performed excellent recyclability in five reaction runs without an obvious loss of activity.

Shape dependency of CO2 hydrogenation on ceria supported singly dispersed Ru catalysts

Harnessing the selectivity in catalytic hydrogenation of CO2 is important for producing valuable chemicals. Herein, the shape dependency of the CO2 hydrogenation on singly dispersed Ru/CeO2 catalysts is investigated. CeO2 of three shapes, including nanocube, nanooctahedron and nanorod, are prepared as the catalyst supports and assigned to the surface of (100), (111) and (110) crystal plane, respectively. The Ru/CeO2 (nanorod) exhibits the highest selectivity to CO (97.6 %) at 350 °C, while the Ru/CeO2 (nanocube) exhibits a mediocre selectivity to CO (41.4 %) but the highest CO2 conversion. The shape of the CeO2 support determines the electronic state of supported Ru atoms through the electronic metal-support interaction. The low CO affinity on cationic Ruβ sites leads to the higher selectivity to CO on the Ru/CeO2 (nanorod) and Ru/CeO2 (nanooctahedron) catalysts, while the strong dissociation ability of H2 on low valence Ruα sites results in the high activity on the Ru/CeO2 (nanocube) catalyst.

Highly selective catalytic transfer hydrogenation of biomass derived furfural to furfural alcohol over Zr/SBA-15 catalysts

The effective utilization of furfural (FU) from biomass for the production of furfuryl alcohol (FOL) is becoming increasingly important due to the versatility of FOL production of valuable chemicals. This study reports a highly efficient approach for in-situ hydrothermal methods to prepare SBA-15 (SB) and x% Zr/SBA-15 (ZSB) composite catalysts with different weight percentages (x = 1, 3, and 5 wt.%). The prepared bare and most active catalysts were analyzed by XRD, FT-IR, FE-SEM, EDS, and TEM. Characterization studies showed that Zr species were present and uniformly distributed in the SB framework. All the prepared materials were used for liquid phase catalytic transfer hydrogenation (CTH) of FU with isopropanol (2-PrOH) at atmospheric N2 pressure (1 atm) under mild reaction conditions. The 3ZSB catalyst showed excellent conversion of FU (100 %) and remarkably high selectivity for FOL (97 %). To achieve the highest possible conversion of FU with high selectivity to the desired products, the experimental parameters such as reaction temperature, hydrogen donor, time, molar ratio, and catalyst weight were optimized. The reusability of the most active 3ZSB composite catalysts was also tested for up to six sequences. Moreover, no significant change in catalytic performance was observed. In this study, a green, efficient, and sustainable process for the catalytic synthesis of FOL using biomass-derived FU is presented. This process is of great importance in promoting the sustainable use of biomass resources.

Selective Catalytic Hydrogenation of Vegetable Oils over Copper-Based Catalysts Supported on Amorphous Silica

This work aims to study the selective catalytic hydrogenation of vegetable oils to maximize oleic acid content and expand the range of non-edible uses. Oleic acid (C18:1) is suitable for use as a biodegradable lubricant and is a building block in producing polymers and plastics from renewable resources. The challenge is the synthesis of heterogeneous catalysts, allowing for a maximum yield of C18:1 and low formation of the corresponding saturated acid (stearic acid). New copper-based catalysts on silica were synthesized via two synthesis methods: hydrolysis precipitation and ammonia-evaporation. Experimental tests were carried out at a lab scale operating in a semi-batch mode. The best conversion reached 90% for C18:3 and 80% for C18:2 HP Cu-silica catalyst results, the best candidate for an industrial case study. Good results were obtained in the selectivities of oleic acid production and cis/trans isomers ratio. The modified return on the investment of the designed hydrogenation plant provides the revenues of the capital costs in less than one year.

Ni-based nanocatalyst protected by ultrathin mesoporous nitrogen-doped carbon layer with hollow structure for the efficient transfer hydrogenation of halogenated nitrobenzenes

It is of great scientific and industrial value to develop cheap and efficient supported non-noble metal-based catalysts for the selective hydrogenation of halogenated nitrobenzenes. In this work, hollow-structured Ni-based nano-catalysts coated with ultrathin nitrogen-doped carbon layers (H-Ni@NC) have been prepared. The etching of SiO2 template before calcination and decomposition of residual Ni3Si2O5(OH)4 shell into SiO2 leads to the resulting catalysts could maintain good mechanical property and stability. The H-Ni@NC catalyst prepared at 600 °C exhibits the optimal catalytic performance for the catalytic selective hydrogenation of halogenated nitrobenzenes under mild conditions (60 °C) when using hydrazine hydrate (N2H4·H2O) as the reducing agent, and could maintain its catalytic properties even after 5 consecutive runs. The contrast experiments confirm that the combination of hollow structure with N-doped carbon protective layer make the catalyst show the best catalytic effect, and the synergistic effects are further discussed in detail combined with characterization analysis. In addition, this work further reveals the mechanism of Ni-based catalysts for the transfer hydrogenation of halogenated nitrobenzenes, which may provide a reference idea for the preparation of other Ni-based catalysts.

Selective Catalytic Hydrogenation of Fatty Acids with Cobalt–Halloysite Nanocomposites for Waste Valorization

Selective Catalytic Hydrogenation of Fatty Acids with Cobalt–Halloysite Nanocomposites for Waste Valorization

Acetylene Semi-Hydrogenation on Intermetallic Ni–In Catalysts: Ni Ensemble and Acetylene Coverage Effects from a Theoretical Analysis

DFT-based reaction profiles and microkinetic simulations were used to describe the catalytic selective hydrogenation of acetylene on Ni, Ni3In, NiIn, and Ni2In3 model intermetallic surfaces. Among the NixIny intermetallic catalysts, NiIn showed the highest ethylene yield. Decreased formation of ethane was observed on NiIn and Ni2In3 accompanied by increased formation of oligomers compared to Ni and Ni3In. This emphasizes the significance of accounting for the oligomerization reactions when evaluating the selectivity of the catalysts. Inconsistent acetylene coverage was obtained when performing microkinetic simulations using free energy values calculated at low acetylene coverage, while a fully consistent coverage was obtained using high-coverage free energy values. Results from the high-coverage microkinetic model showed that the presence of In on the catalytic surface decreased the rate of acetylene consumption with a trade-off relation between activity and selectivity. Simulations in the absence of ethylene in the feed confirmed that ethylene hydrogenation and acetylene C–C coupling were the primary sources for ethane and oligomer formation, respectively. This study highlights the importance of considering oligomerization reactions, coverage effect, and feed composition when describing the activity and the selectivity of catalysts during the competitive hydrogenation of alkynes.

Catalytically efficient Co-CoOx-Al2O3 interface for mild temperature fatty alcohol production via fatty acid transfer hydrogenation

The cost-effective and environmentally friendly conversion of biomass to value-added chemicals under mild conditions is highly desirable but challenging. Herein, two-dimensional Co-Al hydrotalcite catalysts (CoAl-LDOx) were fabricated for selective catalytic transfer hydrogenation (CTH) of fatty acids to fatty alcohols with isopropanol (2-PrOH) as hydrogen donor. The structure and morphology of surface Co species can be regulated via reduction temperature. The optimal CoAl-LDO600 with high Co dispersion, modest reducibility, and rich Co-CoOx-Al2O3 interface achieved the highest octadecanol yield (94.2%) at full oleic acid conversion under 200 °C for 3 h. This catalyst was magnetically separable, highly stable and versatile for various fatty acids to achieve 89.1–96.7% alcohol yields. Controlled experiments suggest that 2-PrOH dehydrogenation was not highly dependent on Co structure, while the interfacial synergy of metallic Co and oxidized Co boosted the active hydrogen transfer, thus accelerating the overall reaction. The present work provided a boosted and stable catalytic system for biomass-related hydrogenation reactions without any external hydrogen supply.