Catalytic Performance For Hydrogenation Research Articles

Mechanistic insight into the electron-donation effect of modified ZIF-8 on Ru for CO2 hydrogenation to formic acid

The electron-donating effect of supports on active metals has been reported to be beneficial to improve catalytic activity of heterogenized molecule catalysts for CO2 hydrogenation to formic acid. However, this effect has not been discussed in depth from the perspective of reaction mechanism, especially for CO2 activation with the combination of theoretical calculations. Herein, we report a catalyst prepared via anchoring RuCl3 on a post-synthetic modified (PSM) zeolitic imidazolate framework-8 (ZIF-8) in which linkers 3-methyl-1,2,4-triazole (Mtz) with a surplus of uncoordinated N sites have been incorporated. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations reveal that uncoordinated N sites in linkers donate additional electron-density to Ru, resulting in the decrease of energy barrier of CO2 activation. And the RuCl3@ZIF-8-Mtz(0.29) catalyst containing the most Mtz ligands displayed the highest catalytic performance for the CO2 hydrogenation to formic acid as compared to RuCl3@ZIF-8-Mtz(0.15) and RuCl3@ZIF-8.

A Study on the Binary and Ternary CuZnAl Catalysts without Additives for Efficient CO Hydrogenation to Ethanol

AbstractSynthesis of ethanol from syngas on CuZnAl catalyst without additives has attracted substantial interest. However, the active sites and the reaction mechanism are still not fully understood due to the complexity of the ternary system. Herein, a series of binary (CuZn, CuAl, ZnAl) and ternary CuZnAl catalysts were prepared using complete liquid method for CO hydrogenation to ethanol. The results show that CAT‐CZ and CAT‐ZA possess much higher ability for ethanol synthesis than CAT‐CA, which is attributed to the presence of the key species Zn and the strong interaction at the interface. In situ DRIFTS measurements reveal the intermediate species of each catalyst, indicating that there are different carbon chain growth paths in CAT‐CZ and CAT‐ZA. The desirable catalytic CO hydrogenation performance (10.87 % of CO conversion and 57.18 % proportion of ethanol in total alcohol) on CAT‐CZA can be attributed the existence of multiple mechanisms for the ethanol production process.

A highly efficient Cu-ZnO/SBA-15 catalyst for CO2 hydrogenation to CO under atmospheric pressure

The conversion of CO2 to useful chemicals has been considered as an essential strategy to mitigate greenhouse gas emission. In this work, Cu/SBA-15 and Cu-ZnO/SBA-15 catalysts were prepared and used for CO2 hydrogenation to CO. Although both catalysts give excellent CO selectivity (99.9%), Cu-ZnO/SBA-15 exhibits more superior catalytic activity with CO2 conversion of 29.1% at400 °C and atmospheric pressure. High specific surface area and confinement structure of SBA-15 and the addition of ZnO make Cu nanoparticles more dispersed. Because of this extraordinary dispersion, Cu-ZnO/SBA-15 has strong ability to interact with CO2 and H2 and behaves better catalytic CO2 hydrogenation performance than most catalysts in previous articles. Moreover, Cu-ZnO/SBA-15 has good catalytic stability and has, therefore, great potential for industrial application.

Rational design of biogenic PdxAuy nanoparticles with enhanced catalytic performance for electrocatalysis and azo dyes degradation.

The green biogenic PdAu nanoparticles (bio-PdAu NPs) exhibits remarkable catalytic performance in hydrogenation, which is highly desired. However, the catalytic principles and effectiveness of bio-PdxAuy NPs in response to various catalytic systems (electrocatalysis and suspension-catalysis) are unclear. Herein, a facile synthetic strategy for bio-PdxAuy NPs synthesis with controlled size and the catalytic principles for hydrogen evolution reaction (HER) and azo dye degradation is reported. In the biosynthetic process, the size and composition of the bio-PdxAuy NPs could be precisely controlled by predesigning the precursor mass ratio of Pd/Au, and the Au proportion showed a linear relationship with the size of NPs (R2=0.92). The obtained bio-PdxAuy NPs exhibit variable activity in electrocatalysis (HER) and suspension-catalysis (azo dye degradation). For electrocatalysis, the formation of conductive networks that facilitates the extracellular electron transfer is crucial. It was revealed that the bio-Pd2Au8 exhibited superior electrocatalytic performance in HER/toward hydrogen evolution, with a maximum current density of 1.65mAcm-2, which was 1.54 times higher than that commercial Pd/C (1.07mAcm-2). The high electrocatalytic activity was attributed to its appropriate size (81.38±6.14nm) and uniform distribution on the cell surface, which promoted the extracellular electron transfer by constructing a conductive network between catalyst and electrode. However, for suspension-catalysis, the size effect and synergistic effect of bimetallic NPs have a more prominent effect on the degradation of azo dyes. As the increase of Au proportion the particle size decreases, and the catalytic activity of bio-PdxAuy improved significantly. The response principles of bio-PdxAuy proposed in this study provide a reliable reference for the rational design of bio-based bimetallic catalysts with enhanced catalytic performance.

Highly dispersed nickel boosts catalysis by Cu/SiO2 in the hydrogenation of CO2-derived ethylene carbonate to methanol and ethylene glycol

The efficient hydrogenation of CO 2 -derived ethylene carbonate (EC) to yield methanol (MeOH) and ethylene glycol (EG) is a key process for indirect conversion of CO 2 to MeOH. However, a high H 2 /EC molar ratio during the hydrogenation process (usually as 180–300) is generally required to achieve good catalytic performance, resulting in high cost and energy consumption for H 2 circulation in the promising industrial application. Here, we prepared a series of Ni-modified Cu/SiO 2 catalysts and explored the effects of synthesis methods and Ni contents on catalytic performance under different H 2 /EC molar ratios. The Cu/SiO 2 catalyst with 0.2% (mass) Ni loading prepared by co-ammonia evaporation method exhibited above 99% conversion of EC, 91% and 98% selectivity to MeOH and EG respectively at H 2 /EC ratio of 60. And no significant deactivation was observed within 140 h at a lower H 2 /EC of 40. It is demonstrated that a few of Ni addition could not only promote Cu dispersion and increase surface Cu + species due to the strong interaction between Cu and Ni species, but also form uniformly-dispersed CuNi alloy species and thus enhance the adsorption and dissociation of H 2 . But the excess Ni species would aggregate and segregate to cover partial surface of Cu nanoparticles, leading to a significantly drop of catalytic performance in EC hydrogenation. These insights may provide guidance for further design of catalysts for the ester hydrogenation reactions.

Ultrasonic-assisted synthesis of highly stable RuPd bimetallic catalysts supported on MgAl-layered double hydroxide for N-ethylcarbazole hydrogenation.

N-Ethylcarbazole (NEC), as a promising liquid organic hydrogen carrier (LOHC), can store and release hydrogen through a reversible catalytic hydrogenation and dehydrogenation reaction. In this paper, RuPd bimetallic nanocatalyst supported on MgAl-layered double hydroxide (RuPd/LDH) was prepared by ultrasonic-assisted reduction method, and its catalytic performance in NEC hydrogenation was also studied. Under the action of ultrasound, hydroxyl groups (-OH) on the surface of LDH support dissociated into highly reductive hydrogen radicals for the reduction of Ru3+ and Pd2+ to Ru0 and Pd0. For the 4Ru1Pd/LDH-(300-1) catalyst prepared under ultrasonic conditions of 25 kHz, 300 W, and 1 h, the average size of the metal nanoparticles was only 1.23 nm, which indicated that Ru, Pd, and RuPd NPs were highly dispersed on the support. The strong electronic effects between Ru and Pd improved its catalytic performance in NEC hydrogenation. With m(Ru+Pd)/m(NEC) = 0.2wt%, pressure of 6 MPa, and temperature of 120 °C, the selectivity of dodecahydro-N-ethylcarbazole (12H-NEC) was 98.07%, and the capacity and percentage of hydrogen storage were 5.75wt% and 99.3%, respectively. After the catalyst was recycled 8 times, the percentage of hydrogen storage still reached 98.9%, showing higher stability. The preparation method is simple and environmentally friendly, providing an idea for the preparation of ultrafine bimetallic catalysts with high catalytic activity and stability.

Preparation of Porous NiCe Composite Catalyst and Its Performance for CO2 Hydrogenation

AbstractNi component can be effectively introduced into CeO2 by a soft template method to prepare porous NiCe composite catalysts. The reducibility of the catalyst precursors was studied by H2‐TPR. The physicochemical properties of the prepared NiCe composite catalysts were characterized by XRD, quasi in‐situ XPS, BET and TEM. And the catalytic performances of the corresponding NiCe composite catalysts was evaluated by CO2 catalytic hydrogenation. The synergistic effect of Ni and Ce species can significantly improve the reducibility of the precursors to form CO2 hydrogenation active sites in the corresponding NiCe composite catalysts. The morphology, pore structure, specific surface area, crystallinity and content of metal Ni species of the prepared NiCe composite catalysts were significantly affected by nNi/nCe ratio, which can affect the CO2 catalytic hydrogenation performances of NiCe composite catalysts. The synergistic effect of Ni and Ce species can also promote the formation of NiCe composite catalyst nanoparticles with small particle size about 5–10 nm. The developed mesoporous structure and high specific surface area can be formed in the prepared NiCe composite catalysts. The NC3 catalyst with a nNi/nCe ratio of 3.0 showed the best CO2 hydroreduction performances and use stability. When the reaction temperature was 300 °C, the CO2 conversion and CH4 selectivity can reach 85.6% and 100%, respectively. Even if the reaction temperature rises to 340 °C, the CO2 conversion and CH4 selectivity can be maintained at 83.7% and 100% in the continuous reaction of 600 min, respectively.

Effect of Cu Content on Structure of NiCu Alloy Catalyst and Catalytic Performance for Nitroarenes Hydrogenation

AbstractCarbon doped silica‐supported NiCu alloy nanoparticles (Ni1Cux/C@SiO2) with different Cu/Ni molar ratio (x=0.12, 0.24, 0.36) were fabricated via one‐step impregnation, following in situ carbonization reduction. Effects of Cu content on catalyst structure, surface properties and particle sizes were investigated by Brunauer‐Emmett‐Teller (BET), inductively coupled plasma (ICP), Raman, X‐ray diffraction (XRD), transmission electron microscopy (TEM) and X‐ray photoelectron spectroscopy (XPS). The surface Ni0 content increased with increasing Cu content, but showed a maximum at 0.24 of Cu/Ni molar ratio, because the smaller NiCu alloy nanoparticle formed and the segregation of antioxidative Cu atoms on the surface protected the metallic Ni from oxidation. The Ni1Cux/C@SiO2 were investigated for nitrobenzene hydrogenation with H2. The optimal Ni1Cu0.24/C@SiO2 catalyst with the highest Ni0 content showed markedly improved catalytic activity compared to monometallic Ni/C@SiO2. The Ni0 species were the active sites for the hydrogenation of nitrobenzene. The Ni1Cu0.24/C@SiO2 could transform various substituted nitroarenes to corresponding aromatic amines. Moreover, the Ni1Cu0.24/C@SiO2 could be recycled for 8 times without decrease in catalytic performance, exhibiting superior anti‐oxidation and anti‐leaching abilities.

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.

A facile synthesis of in-situ formed amorphous zirconia catalysts for efficient transfer hydrogenation of unsaturated aldehydes

Several metal salts were used for the cinnamaldehyde transfer hydrogenation, and it was found that heterogeneous reactions coexisted in this superficial homogeneous catalytic system. Among these metal salts, Zr(NO3)4·5H2O exhibits the best catalytic performance. Notably, the in-situ formed amorphous zirconia during the reaction is identified as the active site of Zr(NO3)4·5H2O. The in-situ formed zirconia in the presence of cinnamaldehyde (self-selective ZrO2) possesses smaller particle size, better dispersion and more surface hydroxyl groups, which exhibits remarkably enhanced catalytic performance in cinnamaldehyde transfer hydrogenation as compared to the commercial nano-zirconia and laboratory-prepared zirconia. The characterization and theoretical analysis reveal that the synergistic catalytic effect between zirconium active site and surface hydroxyl groups can effectively activate CO bonds in cinnamaldehyde and reduce the activation energy barrier, thus significantly improving the transfer hydrogenation performance. Moreover, the self-selective ZrO2 exhibits excellent catalytic performance for a series of unsaturated aldehydes.

Boosting the Catalytic Performance of CuOx in CO2 Hydrogenation by Incorporating CeO2 Promoters

AbstractCopper is one of the most promising components in CO2 hydrogenation reactions, however, it still seriously suffers from the lower capability in CO2 activity, as well as poor durability. Herein, a novel copper‐cerium mixed metal oxide is fabricated via a controllable surface deposition route, showing excellent catalytic performance in CO2 hydrogenation. Of particular note, among the various samples with tunable Cu/Ce molar ratios, the obtained CuOx‐5CeO2 containing 0.42% Ce exhibits the highest catalytic activity with ≈31% CO2 conversion and 98% CO selectivity at 380 °C, as well as an excellent stability for 50 h. The as‐prepared catalysts are then characterized by H2‐temperature‐programmed reduction, CO2‐termperature programmed desorption, and in situ diffuse reflectance infrared Fourier transform spectroscopy to explore the possible reaction pathways. The results indicate the significance of the interactions between CuOx and CeO2, which can facilitate the activation of H2 and CO2 simultaneously, to promote the formation of formate intermediates.

Preparation of Bimetallic CuxAgy Nanoparticles and their Catalytic Performance in Hydrogenation of 4-Nitrophenol with H2 to 4-Aminophenol

Preparation of Bimetallic CuxAgy Nanoparticles and their Catalytic Performance in Hydrogenation of 4-Nitrophenol with H2 to 4-Aminophenol

Bimetallic catalyst derived from copper cobalt carbonate hydroxides mediated ZIF-67 composite for efficient hydrogenation of 4-nitrophenol

4-nitrophenol (4-NP), a toxic pollutant, is ubiquitous in the environment and difficult to degrade in natural conditions. To deal with this contaminant, catalytic reduction of 4-NP is a promising way. Herein, we report a copper and cobalt nanoparticle decorated carbon framework (Cu/Co@CF) through a self-sacrificial template method derived from the copper cobalt carbonate hydroxides/zeolitic imidazolate framework-67 (CuCoCH/ZIF-67) composite. Served as a cobalt and copper source as well as a self-sacrificial template, CuCoCH extended the pore sizes of carbonized derivatives of ZIF-67 and synchronously transformed to bimetallic active sites. The catalyst exhibited a highly efficient catalytic performance and remarkable reusability for hydrogenation of 4-NP. The 4-NP conversion reached 99.7% in 1 min and the pseudo-first-order reaction kinetic constant was 5.122 min-1, which is the highest among similarly reported catalysts.

Preparation of highly dispersed CuO-ZnO-ZrO2 catalysts and their improved catalytic performance for hydrogenation of CO2

Highly dispersed CuO-ZnO-ZrO2 (CZZ) catalysts were prepared by the citrate gel method. The structures of catalysts and precursors were characterized by XPS, BET, XRD, H2-TPR, H2-TPD, CO2-TPD, and TG-DTA. The effects of wet gel drying time and citric acid dosage on the catalyst structure were studied and compared with the catalysts prepared by the combustion method to investigate the performance of different catalysts for CO2 hydrogenation to methanol. Studies have shown that prolonging the drying time of wet gel can effectively prevent the splashing of the catalyst during calcination. The BET surface area of the catalyst dried at 120 °C for 48 h is 44.8 m2/g, which is higher than that of the combustion method. When the amount of citric acid is equal to the stoichiometric ratio, the catalyst has the best performance. Under the conditions of 240 °C, 2.6 MPa, space velocity of 3600 h–1, and H2/CO2 volume ratio of 3, the space–time yield of methanol reaches 110.3 g/(kg h). Excessive citric acid will affect the dispersion of catalyst components and result in decomposition residue covering catalyst surface active sites, which is not conducive to CO2 hydrogenation reaction.

Synthesis of Hollow Silica Nanotubes from Linear Metallosupramolecular Polyelectrolytes and Their Application as Catalyst Supports for Hydrogenation.

In this study, we report a facile templating method to construct hollow silica nanotubes. In particular, bis-terpyridine is used to coordinate metal ions to form polymeric bis-terpyridine-metal complexes that further self-assemble into tubular organogels in the presence of cetyltrimethylammonium bromide. The following silica deposition on organogels and subsequent calcination give metal oxide-doped hollow silica nanotubes (MxOy-HSNs). Facilitated by the high coordination stability constants of bis-terpyridine with metal ions, a series of metal ions, such as Fe, Ni, Cu, and Zn, could be used to form polymeric bis-terpyridine-metal complexes. The supported Pt/FexOy-HSNs exhibit good catalytic performance for hydrogenation of a series of substituted nitrobenzenes, showing that the obtained MxOy-HSNs could be used as catalyst supports due to their good textural properties.

Interfacial compatibility critically controls Ru/TiO2 metal-support interaction modes in CO2 hydrogenation

Supports can widely affect or even dominate the catalytic activity, selectivity, and stability of metal nanoparticles through various metal-support interactions (MSIs). However, underlying principles have not been fully understood yet, because MSIs are influenced by the composition, size, and facet of both metals and supports. Using Ru/TiO2 supported on rutile and anatase as model catalysts, we demonstrate that metal-support interfacial compatibility can critically control MSI modes and catalytic performances in CO2 hydrogenation. Annealing Ru/rutile-TiO2 in air can enhance CO2 conversion to methane resulting from enhanced interfacial coupling driven by matched lattices of RuOx with rutile-TiO2; annealing Ru/anatase-TiO2 in air decreases CO2 conversion and converts the product into CO owing to strong metal-support interaction (SMSI). Although rutile and anatase share the same chemical composition, we show that interfacial compatibility can basically modify metal-support coupling strength, catalyst morphology, surface atomic configuration, MSI mode, and catalytic performances of Ru/TiO2 in heterogeneous catalysis.

Organic acid-assisted design of zirconium-lignocellulose hybrid for highly efficient upgrading levulinic acid to γ-valerolactone

Acid treatment is the key to improve the physicochemical properties of metal-lignocellulosic hybrid, thus contributing to the catalytic performance for catalytic transfer hydrogenation (CTH) of carbonyl compounds to their corresponding alcohols. Herein, a series of organic acids were introduced to assist the design of Zr-Pennisetum sinese hybrid. Comprehensive studies demonstrated the dramatic changes of specific surface and acid/base sites of the prepared hybrid. Remarkably, formic acid-assisted Zr@PS-FA possessed the largest surface area and enhanced interaction effects between acids (Lewis acid and Brønsted acid) and Lewis base sites, which exhibited excellent catalytic activity for CTH of levulinic acid to γ-valerolactone with a high yield of 95.6% in isopropanol under moderate reaction conditions (180 °C and 1.5 h). Zr@PS-FA also showed remarkable cycle stability, and it could be consecutively used at least six runs without a significant loss in catalytic activity. More gratifyingly, Zr@PS-FA displayed a superior universality for CTH of various carbonyl compounds to their corresponding alcohols, demonstrating great potential for upgrading biomass-derived aldehydes/ketones.

Network-Like Platinum Nanosheets Enabled by a Calorific-Effect-Induced-Fusion Strategy for Enhanced Catalytic Hydrogenation Performance.

In this paper, we report the construction of network-like platinum (Pt) nanosheets based on Pt/reduced graphite oxide (Pt/rGO) hybrids by delicately utilizing a calorific-effect-induced-fusion strategy. The tiny Pt species first catalyzed the H2-O2 combination reaction. The released heat triggered the combustion of the rGO substrate under the assistance of the Pt species catalysis, which induced the fusion of the tiny Pt species into a network-like nanosheet structure. The loading amount and dispersity of Pt on rGO are found to be crucial for the successful construction of network-like Pt nanosheets. The as-prepared products present excellent catalytic hydrogenation activity and superior stability towards unsaturated bonds such as olefins and nitrobenzene. The styrene can be completely converted into phenylethane within 60 min. The turnover frequency (TOF) value of network-like Pt nanosheets is as high as 158.14 h−1, which is three times higher than that of the home-made Pt nanoparticles and among the highest value of the support-free bimetallic catalysts ever reported under similar conditions. Furthermore, the well dispersibility and excellent aggregation resistance of the network-like structure endows the catalyst with excellent recyclability. The decline of conversion could be hardly identified after five times recycling experiments.

Synthesis of Cu Single Atom with Adjustable Coordination Environment and Its Catalytic Hydrogenation Performance※

Synthesis of Cu Single Atom with Adjustable Coordination Environment and Its Catalytic Hydrogenation Performance^※

Two-dimensional N-doped Pd/carbon for highly efficient heterogeneous catalysis.

A novel two-dimensional ZIF-derived Pd@CN material prepared via one-step calcination exhibits outstanding catalytic activity in heterogeneous hydrogenation. Its well-developed porous structure, low dimensions and low density make active sites more accessible. This facile and effective strategy can guide the synthesis of highly active and durable Pd@CN catalysts with specific morphologies.