Catalytic Performance For Selective Hydrogenation Research Articles

Expedited Synthesis of Metal Phosphides Maximizes Dispersion, Air Stability, and Catalytic Performance in Selective Hydrogenation

AbstractMetal phosphides have been hailed as potential replacements for scarce noble metal catalysts in many aspects of the hydrogen economy from hydrogen evolution to selective hydrogenation reactions. But the need for dangerous and costly phosphorus precursors, limited support dispersion, and low stability of the metal phosphide surface toward oxidation substantially lower the appeal and performance of metal phosphides in catalysis. We show here that a 1‐step procedure that relies on safe and cheap precursors can furnish an air‐stable Ni2P/Al2O3 catalyst containing 3.2 nm nanoparticles. Ni2P/Al2O3 1‐step is kinetically competitive with the palladium‐based Lindlar catalyst in selective hydrogenation catalysis, and a loading corresponding to 4 ppm Ni was sufficient to convert 0.1 mol alkyne. The 1‐step synthetic procedure alters the surface ligand speciation of Ni2P/Al2O3, which protects the nanoparticle surface from oxidation, and ensures that 85 % of the initial catalytic activity was retained after the catalyst was stored under air for 1.5 years. Preparation of Ni2P on a variety of supports (silica, TiO2, SBA‐15, ZrO2, C and HAP) as well as Co2P/Al2O3, Co2P/TiO2 and bimetallic NiCoP/TiO2 demonstrates the generality with which supported metal phosphides can be accessed in a safe and straightforward fashion with small sizes and high dispersion.

Titelbild: Expedited Synthesis of Metal Phosphides Maximizes Dispersion, Air Stability, and Catalytic Performance in Selective Hydrogenation (Angew. Chem. 33/2024)

Titelbild: Expedited Synthesis of Metal Phosphides Maximizes Dispersion, Air Stability, and Catalytic Performance in Selective Hydrogenation (Angew. Chem. 33/2024)

Expedited Synthesis of Metal Phosphides Maximizes Dispersion, Air Stability, and Catalytic Performance in Selective Hydrogenation.

Metal phosphides have been hailed as potential replacements for scarce noble metal catalysts in many aspects of the hydrogen economy from hydrogen evolution to selective hydrogenation reactions. But the need for dangerous and costly phosphorus precursors, limited support dispersion, and low stability of the metal phosphide surface toward oxidation substantially lower the appeal and performance of metal phosphides in catalysis. We show here that a 1-step procedure that relies on safe and cheap precursors can furnish an air-stable Ni2P/Al2O3 catalyst containing 3.2 nm nanoparticles. Ni2P/Al2O3 1-step is kinetically competitive with the palladium-based Lindlar catalyst in selective hydrogenation catalysis, and a loading corresponding to 4 ppm Ni was sufficient to convert 0.1 mol alkyne. The 1-step synthetic procedure alters the surface ligand speciation of Ni2P/Al2O3, which protects the nanoparticle surface from oxidation, and ensures that 85 % of the initial catalytic activity was retained after the catalyst was stored under air for 1.5 years. Preparation of Ni2P on a variety of supports (silica, TiO2, SBA-15, ZrO2, C and HAP) as well as Co2P/Al2O3, Co2P/TiO2 and bimetallic NiCoP/TiO2 demonstrates the generality with which supported metal phosphides can be accessed in a safe and straightforward fashion with small sizes and high dispersion.

Cover Picture: Expedited Synthesis of Metal Phosphides Maximizes Dispersion, Air Stability, and Catalytic Performance in Selective Hydrogenation (Angew. Chem. Int. Ed. 33/2024)

Cover Picture: Expedited Synthesis of Metal Phosphides Maximizes Dispersion, Air Stability, and Catalytic Performance in Selective Hydrogenation (Angew. Chem. Int. Ed. 33/2024)

Novel Reaction-Adsorption Method for Preparation of Ru–Zn–La/ZrO2 Catalysts with High Catalytic Performance for Selective Hydrogenation of Benzene

A novel wet-chemistry reaction-adsorption strategy via the facile acid–base interaction under mild conditions is demonstrated to fabricate the state-of-the-art Ru–Zn–La/ZrO2 catalysts for selective hydrogenation of benzene to cyclohexene. The catalyst preparation process is systematically investigated and verified with the combination of various characterization techniques. Preloading of lanthanide salts and alkali treatment after calcination not only favor the introduction of ruthenium and zinc species in the later stages but also help enhance the dispersion of the catalysts. The reaction rate constants (k1 and k2) decrease with the increment of the Zn/Ru molar ratio, and the selectivity at 40% conversion (S40) is positively correlated with the k1/k2 ratio, demonstrating the role of Zn species in retarding the hydrogenation activity of Ru and improvement of the selectivity to cyclohexene. In general, the catalytic behavior is dependent on the particle size of Ru, the La-to-Ru electron transfer effect, the content of Zn species, and the surface hydrophilicity of catalyst. These factors are generated by using different precursors and various predesigned La/Ru molar ratios in the preparation recipe. Moreover, a passivation treatment before the hydrogenation reaction can promote the cyclohexene selectivity of the catalyst Ru–Zn–La/ZrO2 (1.6 La/Ru) to 80.6% at a benzene conversion of 43.7%, which meets the industrial requirement. Notably, the specific activity of the catalyst is as high as 1224 gBZ·gRu–1·h–1, over 10 times higher than the industrial criterion. This work provides new insights into the design of Ru-based catalysts for benzene hydrogenation and other hydrogenation reactions as well.

N,S-Co-doping Significantly Improves the Co–Nx Content of the Co-NSPC Catalyst and Enhances the Catalytic Performance for Selective Hydrogenation of Halogenated Nitrobenzenes

Non-noble metals have attracted worldwide attention for the catalytic hydrogenation of halonitrobenzene due to their high activity, low price, and abundance on Earth. However, the construction of effective and stable non-noble-metal catalysts for the selective hydrogenation of halonitrobenzene to haloaniline by a simple method remains challenging. Herein, we report a facile one-pot method for the synthesis of N,S-co-doped mesoporous carbon-supported non-noble-metal catalysts through carbonization of a mixture of metallic precursors and 2-aminothiazole in molten ZnCl2. The prepared Co-NSPC catalyst showed excellent activity and selectivity with a turnover frequency of 84.4 h–1 in the hydrogenation of p-chloronitrobenzene to p-chloroaniline. Furthermore, Co–Nx was found to be the main active site for this reaction on the basis of characterization and experimental data, and the introduction of S promoted the formation of Co–Nx sites. Moreover, the Co-NSPC-800 catalyst can be reused at least four times and applied to the hydrogenation of 10 kinds of halogenated nitrobenzenes with excellent selectivity.

A zirconium(IV)-based metal–organic framework modified with ruthenium and palladium nanoparticles: synthesis and catalytic performance for selective hydrogenation of furfural to furfuryl alcohol

A zirconium(IV)-based metal–organic framework modified with ruthenium and palladium nanoparticles: synthesis and catalytic performance for selective hydrogenation of furfural to furfuryl alcohol

Synergistic effects of PtFe/CeO2 catalysts afford high catalytic performance in selective hydrogenation of cinnamaldehyde

Selective hydrogenation of unsaturated aldehydes remains a grand challenge in controlling chemoselectivity up to now. We synthesized a series of PtFex/CeO2 catalysts, which were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) as well as temperature-programmed-reduction by hydrogen (H2-TPR). The catalytic performance of PtFex/CeO2, including cinnamaldehyde (CAL) conversion and selectivity toward cinnamyl alcohol (COL), is improved remarkably by introduction of Fe species in the Pt particles in the selective CAL hydrogenation under mild conditions. XPS results indicate that the electron transfer from Fe to Pt promotes CAL adsorption, resulting in the enhanced CAL conversion. And the COL selectivity is improved by CAL adsorption via an interaction of CO group with surface oxygen defect sites because of interaction between PtFe and CeO2 support. In all, this study may provide some hints to design efficient nano Pt particles for the selective hydrogenation.

An efficient NiCu@C/Al2O3 catalyst for selective hydrogenation of acetylene.

The development of non-noble metal catalysts for selective hydrogenation still remains a challenge. Herein, NiCu@carbon core-shell nanoparticles supported on Al2O3 (NiCu@C/Al2O3) were prepared, which showed enhanced catalytic performance of acetylene-selective hydrogenation in comparison with NiCu/Al2O3 without carbon encapsulation. In detail, NiCu@C/Al2O3 displayed high ethylene selectivity (>86%) even at an acetylene conversion of 100% and excellent stability (>90 h). Thus, NiCu@C/Al2O3 exhibited great potential as an alternative to Pd-based catalysts for acetylene-selective hydrogenation.

In‐Situ Incorporation of Pt Nanoparticles on Layered Double Hydroxides for Selective Conversion of Cinnamaldehyde to Cinnamyl Alcohol

AbstractDesigning efficient and low‐cost catalysts for generation of cinnamyl alcohol (CMO) from cinnamaldehyde (CMA) hydrogenation is of practical value. Herein, layered double hydroxide supported Pt nanoparticles (Pt‐s/LDH) were prepared by in‐situ reduction of PtCl62− in PtCl62−‐LDH with ethylene glycol, and the PtCl62− was intercalated in LDH by ion‐exchange method. The characterization results verify that small Pt nanoparticles are uniformly distributed on LDH with average diameter of 1.9 nm and narrow size distribution. The prepared Pt‐s/LDH catalyst exhibits excellent catalytic performance for selective hydrogenation of CMA under relatively mild reaction conditions (80 °C, 2 MPa H2) with high turnover frequency (TOF) (0.574 s−1) and CMA conversion (92.6 %). Furthermore, the CMA conversion rate and CMO selectivity remain almost unchanged after the fourth run compared with the results of the first run. This study provides an effective route for synthesis of efficient and stable LDH‐supported metal catalysts.

Ultrasound-driven fabrication of high-entropy alloy nanocatalysts promoted by alcoholic ionic liquids

High-entropy alloy nanoparticles (HEA-NPs) are highly underutilized in heterogeneous catalysis due to the absence of a reliable, sustainable, and facile synthetic method. Herein, we report a facile synthesis of HEA nanocatalysts realized via an ultrasound-driven wet chemistry method promoted by alcoholic ionic liquids (AILs). Owing to the intrinsic reducing ability of the hydroxyl group, AILs were synthesized and utilized as environmentally friendly alternatives to conventional reducing agents and volatile organic solvents in the synthetic process. Under high-intensity ultrasound irradiation, Au3+, Pd2+, Pt2+, Rh3+, and Ru3+ ions were co-reduced and transformed into single-phase HEA (AuPdPtRhRu) nanocrystals without calcination. Characterization results reveal that the as-synthesized nanocrystals are composed of elements of Au, Pd, Pt, Rh, and Ru as expected. Compared to the monometallic counterparts such as Pd-NPs, the carbon-supported HEA nanocatalysts show superior catalytic performance for selective hydrogenation of phenol to cyclohexanone in terms of yield and selectivity. Our synthetic strategy provides an improved and facile methodology for the sustainable synthesis of multicomponent alloys for catalysis and other applications.

A Cationic Ru(II) Complex Intercalated into Zirconium Phosphate Layers Catalyzes Selective Hydrogenation via Heterolytic Hydrogen Activation

AbstractCatalytic hydrogenations constitute economic and clean transformations to produce pharmaceutical and a multitude of fine chemicals in chemical industry. Herein, we report a cationic Ru(II) complex intercalated into zirconium phosphate (ZrP) layers that enables the efficient catalytic conversion of furfural and other biomass‐derived carbonyl compounds into the corresponding alcohols through selective hydrogenation of C=O group. The ZrP layers acted not only as a support for the Ru‐complex, but also as the new ligands to tune the Ru(II) center via forming Ru−O bond. The resulting catalysts exhibit excellent catalytic performance and can be easily recycled for six times without significant loss of activity and selectivity. The Ru(II) complex‐intercalated catalysts have been characterized by XRD, SEM, HRTEM, HAADF‐STEM, XPS, FT‐IR, DR‐UV/Vis, EXAFS and XANES. Especially, it is observed that the appropriate interlayer spacing between ZrP layers is favorable to stabilize the Ru(II) complex. Notably, on the basis of the further characterization and density functional theory (DFT) calculation, it is identified that the interaction of cationic Ru(II) complex and P−OH group within ZrP layers leads to the high catalytic performance in selective hydrogenation, and the newly formed Ru−O−P species plays a crucial role in the heterolytic hydrogen activation and selective hydrogenation of biomass‐derived compounds containing a carbonyl group.

Metal single-atom catalysts for selective hydrogenation of unsaturated bonds

Single atom catalysts (SACs) show excellent catalytic performance in selective hydrogenation. Herein, the applications of SACs in the selective hydrogenation of unsaturated bonds are reviewed.

Understanding the geometric and electronic factors of PtNi bimetallic surfaces for efficient and selective catalytic hydrogenation of biomass-derived oxygenates

Selective and efficient upgrading of furfural over controllable PtNi bimetallic catalyst under mild conditions. Ni-base catalysts are promising candidate for the hydrogenation of furfural (FAL) to high-value chemicals. However, slow intermediate desorption and low selectivity limit its implementation. Identifying the catalytic performance of each active sites is vital to design hydrogenation catalyst, and tuning the geometrical sites at molecule level in PtNi could lead to the modification of electronic structure, and thus the selectity for the hydrogenation of FAL was modulated. Herein, PtNi hollow nanoframes (PtNi HNFs) with three dimensional (3D) molecular accessibility were synthesized, EDX results suggested that Ni was evenly distributed inside of the hollow nanoframes, whereas Pt was relatively concentrated at the edges. DFT calculation demonstrated that PtNi significant decrease the desorption energy of the intermediates. This strategy could not only enhance the desorption of intermediates to improve the catalytic performance, but also transfer the adsorption mode of FAL on catalyst surface to selective hydrogenation of FAL to FOL or THFA. The PtNi HNFs catalyst afforded excellent catalytic performance for selective hydrogenation of a broad range of biomass-derived platform chemicals under mild conditions, especially of FAL to furfuryl alcohol (FOL), in quantitative FOL yields (99%) with a high TOF of 2.56 h −1 . It is found that the superior performance of PtNi HNFs is attributed to its 3D hierarchical structure and synergistic electronic effects between Pt and Ni. Besides, the kinetic study demonstrated that the activation energy for hydrogenation of FAL was as low as 54.95 kJ mol −1 .

Morphology effect of CeO2 on Ni/CeO2 catalysts for selective hydrogenation of cinnamaldehyde

A series of CeO 2 with different morphologies (nanoparticles, nanorods and nanocubes) supported metal nickel catalysts were synthesized successfully using the hydrothermal route. Ni/CeO 2 -R catalyst with nanorods as the support exhibited the best catalytic performance for selective hydrogenation of CAL, which was attributed to the highest concentration of surface oxygen vacancies in Ni/CeO 2 -R. • Ni/CeO 2 with different morphologies were synthesized successfully. • Ni/CeO 2 -R catalyst exhibited the best catalytic performance. • Ni/CeO 2 -R catalyst had the highest concentration of surface oxygen vacancies. • Ni/CeO 2 -R showed excellent catalytic recycling stability. A series of CeO 2 with different morphologies (nanoparticles, nanorods and nanocubes) supported nickel catalysts were synthesized successfully using the hydrothermal route to investigate the morphology effects of CeO 2 on these Ni/CeO 2 catalysts for selective hydrogenation of cinnamaldehyde (CAL). Catalytic activities of three Ni/CeO 2 catalysts were ranked in the order of Ni/CeO 2 -R > Ni/CeO 2 -P > Ni/CeO 2 -C, which was attributed to the the highest concentration of surface oxygen vacancies in Ni/CeO 2 -R. These may lead more active surface oxygen and better redox properties on Ni/CeO 2 -R catalyst. More importantly, Ni/CeO 2 -R also showed excellent catalytic recycling stability, reflecting the morphological effect of nanocatalysis.

Facile Synthesis of Size-Controlled Nitrogen-Doped Mesoporous Carbon Nanosphere Supported Ultrafine Ru Nanoparticles for Selective Hydrogenation of Quinolines.

Nitrogen-doped mesoporous carbon nanosphere (NMCS) with tunable sizes and uniform mesoporosity was synthesized by a facile soft-templating method. During the synthesis, F127 (PEO-PPO-PEO triblock copolymer) could be used not only as a soft template to generate the mesostructure but also as a size-control agent to tailor the size of NMCS in a relatively wide range of 100 to 700 nm. In addition, the synthesis process was simple and suitable for large-scale production. Moreover, the NMCS was used as support of ultrafine Ru nanoparticles (Ru/NMCS), which exhibited good catalytic performances for selective hydrogenation of quinolones. It is expected that the simple synthetic strategy for the NMCS can generate extensive interest in many catalysis and sorption applications.

Gold Nanoparticles Supported on Ce–Zr Oxides for Selective Hydrogenation of Acetylene

Gold nanocatalysts have been reported to be active in the selective hydrogenation of acetylene. In this paper, a series of Au/Ce1−xZrxO2 (x = 0.03 to 0.5) supported catalysts with different ratios of Ce to Zr were prepared and their catalytic performance for selective hydrogenation of acetylene was investigated. The structure and surface defects of the catalyst can be changed by altering the amount of Zr incorporation. Compared to both Au/CeO2 and Au/ZrO2, the synthesized Au/Ce1−xZrxO2 showed the higher catalytic activity with keeping almost 100% ethylene selectivity at 300 °C. The TEM observation indicated that the incorporation of Zr led to the formation of hollow spherical solid solutions. The specific surface area also has a certain influence on the catalytic activity. Considering the catalytic activity of Au/Ce1−xZrxO2 and their characterizations by XPS and Raman, the concentration of Ce4+ and the oxygen vacancy of the Ce1−xZrxO2 support play an important role in the selective hydrogenation of acetylene.

C, N Co-Decorated Alumina-Supported Au Nanoparticles: Enhanced Catalytic Performance for Selective Hydrogenation of Acetylene

The modifications of support for the dispersion and immobilization of gold nanoparticles were examined for the selective hydrogenation of acetylene to ethylene. The catalyst, denoted as Au/CNA, was prepared by the carbonization of C and N atom-containing organic precursors on Al2O3, which were subsequently used as supports for gold nanoparticles. The TOF value of Au/CNA was five times higher than that of Au/Al2O3 at 250 °C. The carbonization modification of Al2O3 support without N species showed almost no change in catalytic activity. Therefore, the improved catalytic performance of Au/CNA is related to the interactions of the N species on the CNA support with nano-gold particles. From the XPS analysis, electron transfer between gold and C, N co-doped species may play an important role in the high levels of Au active site utilization. This study may provide new avenues for the construction of organic/inorganic composite materials for efficient catalytic hydrogenation applications.

Golden touch of the nanoparticles.

A combination of two different types of sites shows high catalytic performance for selective hydrogenation due to hydrogen spillover.

Regulation of sulfur doping on carbon-supported Pd particles and abnormal relationship between Pd particle size and catalytic performance in selective hydrogenation of o-chloronitrobenzene

S was successfully doped into carbon via calcination and Pd size was modulated by adjusting the S content. Sulfur species were considered to be anchor sites, contributing to the highly dispersion of Pd nanoparticles. In addition, Pd/CS4 achieved 99.9% sel. With complete conversion in hydrogenation of o-chloronitrobenzene compared to Pd/AC (99.9% con., 61.6% sel.). Interestingly, catalysts with smaller metal size exhibited higher selectivity and lower activity, which was contrary to previous studies. It was suggested that electronic effects between S and Pd played an important role in this reaction, contributing to the excellent performance of the catalysts.