Catalytic Performance For Hydrogenation Research Articles

Construction of intimate Lewis acid and basic sites on an Al2O3–NC composite catalyst with enhanced performance in transfer hydrogenation of cinnamaldehyde

The concerted function of acidic and basic sites leads to enhanced catalytic performance in transfer hydrogenation of cinnamaldehyde.

Bifunctional catalyst MoSx@H-Beta for highly selective conversion of CO2 to C2–6 hydrocarbons

MoSx clusters encapsulated in channels of H-Beta zeolite constitute a bifunctional catalyst and show excellent catalytic performance for CO2 hydrogenation: CO2 conversion >13%, C2–6 hydrocarbons selectivity >74% and stability >200 h on stream.

An unprecedented oxalate-functionalized Ta/W polyoxometalate enabling the self-assembly of a 2D composite for catalytic hydrogenation

The first-ever oxalate-functionalized Ta-polyoxometalate was synthesized and integrated into a graphene composite, Pd/(C2O4-POM)@rGO, displaying outstanding catalytic performance in olefin hydrogenation.

Electronic state, abundance and microenvironment modulation of Ru nanoclusters within hierarchically porous UiO-66(Ce) for efficient hydrogenation of dicyclopentadiene

Developing catalysts for dicyclopentadiene (DCPD) hydrogenation to tetrahydrodicyclopentadiene (THDCPD) at low temperature is crucial and challenging for the green and energy-saving production of high energy density aviation fuel. Herein, hierarchically porous UiO-66(Ce) encapsulate Ru nanoclusters (NCs) was successfully customized by soft template method and in-situ reduction. The mesoporous UiO-66(Ce) promoted the high dispersion of Ru NCs, and the transfer of substrate molecules. By controlling the synthesis conditions, the electronic state, abundance, and microenvironment of Ru NCs were precisely regulated. Theory calculation and experimental results revealed that metallic Ru as the main active sites greatly promoted the adsorption and activation of substrate molecules. Therefore, mesoporous UiO-66(Ce) encapsulated Ru NCs showed remarkable catalytic DCPD hydrogenation performance with DCPD conversion of 100% and THDCPD selectivity of ~100% (60 °C, only 35 min). This study has brought new inspiration and guidance to the rational design of function materials for various catalytic applications.

Sustainable hydrogenation of limonene to value-added products using Cu–Ni catalysts supported on KIT-5

We synthesized a series of new catalysts of non-noble metals (Cu and Ni) supported on mesoporous silica KIT-5. The materials showed changes in their reduction profile due to the combination of the metals and differences in the particle sizes. The catalysts showed remarkable catalytic performance in hydrogenation of limonene at mild reaction conditions. The catalyst with pure Cu produced only the molecule p-Menth-1-ene, while the addition of Ni promotes the hydrogenation of this product leading to p-menthane, which is an attractive compound as a sustainable aviation fuel (SAF). Cost analysis highlighted the economic advantages of Cu-based catalysts, especially NiCu1:2/K5, offering cost savings in raw materials and increased selectivity toward economically valuable products. Moreover, Cu production was found to have a significantly lower carbon footprint than Ni production, emphasizing the environmental benefits of Cu-based catalysts. Therefore, these new materials underscore the economic and environmental benefits of bimetallic catalysts with an equimolar Cu:Ni ratio.

Sodium Promoted FeZn@SiO2-C Catalysts for Sustainable Production of Low Olefins by CO2 Hydrogenation

A prepared FeZnNa@SiO2-C catalyst with graphitized carbon (C)-modified mesoporous SiO2 supports metal nanoparticles with the sol–gel method. The effect of adding metal Na and Zn promoters as a dispersion on the CO2 hydrogenation to low olefins was systematically studied. The results showed that Zn–Na, as a combination, could promote the absorption of CO2 and improved the conversion rate of CO2. Na as an alkaline substance can improve the absorption of more acidic CO2, which could increase the conversion rate of CO2 to 59.03%. Meanwhile, the addition of secondary metal Zn to Fe-based catalysts to form a surface alloy could alter the adsorption of CO2 and the activation of C-O bonds, inhibit the subsequent hydrogenation of olefins to paraffins, and facilitate the reduction of Fe2O3 and the formation of active Fe5C2 species. The formation of active Fe5C2 species was found in TEM and XRD, and the selectivity of the target product was 41.07%. The deep hydrogenation of olefins was inhibited, and the space–time yield (STY) of low olefins was raised again by inhibiting their deep hydrogenations, up to 0.0436. However, the corresponding STY did not increase infinitely with the increase of Na doping, and higher catalytic performance for CO2 hydrogenation could be exhibited when the Na doping reached 6.4%. Compared with Fe@SiO2-C catalyst, Na- and Zn-promoted Fe-based catalysts, prepared by the modified sol-gel method, can be used directly for highly efficient CO2 hydrogenation to low olefins and thus has a more promising application prospect in the future.

Quenching method to prepare ultra-low loading high-entropy catalyst for furfural selectively hydrogenation at ambient temperature

Herein, the quenching method was employed to prepare ultra-low loading high-entropy catalyst for highly active, chemoselective, and robust furfural hydrogenation. The metals (Pd, Pt, Ru, Mo, Zn) in the form of a complex were vacancy anchored and strongly interacted with the support (TiO2) during the quenching and reduction process, ultimately forming the high entropy catalyst PdPtRuMoZn-TiO2 with strong metal and support interaction (SMSI) driven encapsulated layer. Moreover, this catalyst exhibits excellent catalytic performance for furfural selective hydrogenation with 90.82% conversion and 91.3% selectivity toward furfuryl alcohol at ambient temperature. The catalytic mechanism showed that high-entropy alloy (HEA) enhanced the hydrogen dissociation and migration capacity, and adjusted the electron environment of the interface between TiO2 and HEA, causing rich oxygen vacancies in the TiO2 SMSI driven encapsulated layer and the reduction of the horizontal furfural adsorption configuration, resulting in high FF conversion and furfuryl alcohol selectivity. The work reported ultra-low loading high-entropy catalyst and their superior performance in bio-cellulose-derived product conversion.

Fully exposed Pd species on nanodiamond/graphene hybrid support for the efficient toluene hydrogenation reaction

AbstractLiquid organic hydrogen carriers have emerged as promising hydrogen storage systems, offering notable advantages over conventional storage and utilization efficiency methods. However, designing a catalyst that operates at low temperatures and remains cost‐effective poses a significant challenge. We successfully synthesized Pd species (single atoms, fully exposed clusters, and nanoparticles) on a nanodiamond/graphene (ND@G) hybrid support for toluene hydrogenation. The structure of as‐developed Pd catalyst was investigated by HAADF‐STEM, X‐ray absorption fine structure, Raman, XRD, XPS, and other characterizations. Remarkably, the Pdn/ND@G catalyst achieved a toluene conversion rate of 99.3% (100°C, 2.0 MPa H2) without loss of catalytic ability after 5 runs, which exhibited excellent catalytic performance and stable activity. Furthermore, the Pdn/ND@G catalyst exhibited an apparent activation energy as low as 62.36 ± 3.33 kJ mol−1 and an initial turnover frequency of 33.1 h−1 at 100°C. By adjusting the size and metal‐dependent effects, we have achieved enhanced catalytic performance for toluene hydrogenation, thus paving the way for the design of efficient liquid organic hydrogen storage catalysts.

Catalytic Transfer Hydrogenation Performance of Magnesium-Doped ZrO2 Solid Solutions

This is the first study to investigate the activity of a solid solution containing magnesium ions in a zirconia matrix in the catalytic transfer hydrogenation (CTH) of acetophenone with 2-pentanol. The results have shown that magnesium oxide is very highly active in CTH when physically mixed with zirconia. However, the same concentration of Mg2+ ions (Mg:Zr = 3:97) inserted into a zirconia lattice did not yield high activity in CTH. A higher concentration of Mg2+ ions (5%) was also tested in the two types of systems, i.e., a physical mixture of oxides and a solid solution. The increase in the concentration of Mg2+ ions in the physical mixture led to a pronounced increase in the activity of the system, whereas in the case of the solid solution it led to a slight decrease in activity. The impact of the zirconyl salt used in the synthesis was also examined, but showed little effect on the properties and activity of the systems. The study has also shown that the increase of the concentration of magnesium ions caused a decrease in the m-ZrO2 to t-ZrO2 ratio. Nevertheless, the rate of heating had an even bigger effect on this ratio.

Preparation of SBA-15 supported Ru nanocatalysts by electrostatic adsorption-ultrasonic in situ reduction method and its catalytic performance for hydrogen storage of N-ethylcarbazole.

N-ethylcarbazole (NEC) is an ideal liquid organic hydrogen storage carrier. The development of efficient hydrogen storage catalysts can promote the large-scale application of this process. In this paper, SBA-15 supported Ru nanocatalysts (Ru/S15-SU) were synthesized by strong electrostatic adsorption (SEA)-ultrasonic in situ reduction method (UR). Ru/S15-SU was characterized by N2 adsorption-desorption, TEM, H2 temperature program reduction, FT-IR, XRD, and XPS analysis measures. The results showed that ultrafine Ru NPs were evenly distributed on the surface of SBA-15, and ultrasonic in situ reduction not only reduced Ru3+ to Ru0, but also produced a coordination effect between Ru and O, enhancing the interaction between Ru NPs and the carrier. Ru/S15-SU exhibited excellent catalytic performance in the hydrogenation reaction of NEC, and the hydrogen storage efficiency reached 99.31% at 130°C and 6 MPa H2 pressure, which is superior to that of commercial 5wt%Ru/Al2O3. The excellent catalytic hydrogenation performance can be attributed to the selective anchoring of ruthenium ions on the surface of SBA-15 via electrostatic adsorption, preventing the aggregation of Ru NPs and enhancing the interaction between SBA-15 and Ru NPs by ultrasonic in situ reduction. Ru/S15-SU had a lower NEC hydrogenation apparent activated energy (Ea) of 68.45 kJ/mol than 5wt%Ru/Al2O3 catalyst. This method provides a new approach for the green preparation of nanocatalysts without using any chemical reducing agents.

Elemental Fe conditioning for the synthesis of highly selective and stable high entropy catalysts for CO2 methanation

High entropy oxides (HEOs) with high stability and designability have demonstrated excellent catalytic performance in CO2 hydrogenation. However, it is challenging to combine high methane selectivity and high stability of HEOs using an equimolar design strategy. In this study, a non-equimolar design strategy was used to fix the Cr, Co, Mn and Ni elements and adjust different Fe molar amounts to prepare a highly crystalline HEO at 900 °C. After H2 reduction, the catalyst (HEO-4-900/H2) achieved 72.9% CO2 conversion and 98.8% methane selectivity at atmospheric pressure and 400 °C, and maintained a high methane selectivity of over 97% after 100 h stability test. The catalytic activity was influenced by the amount of Fe. Increasing the amount of Fe could precisely regulate the crystallinity and oxygen defects of the crystal, improve the catalyst stability, reduce the interaction between the Co-Ni alloys and HEOs, and allow the catalyst to contain more Co-Ni active sites and more abundant oxygen vacancies. This study demonstrates the considerable potential of HEOs for CO2 methanation, and provides a new design idea for further stimulating highly active CO2 methanation HEOs catalysts.

Co3InC0.75-In2O3 composite construction and its synergetic hydrogenation catalysis of CO2 to methanol

The efficient catalytic hydrogenation of CO2 to methanol is a promising route for CO2 emission mitigation and utilization. Recently, the Co-In based materials as one of the excellent alternative catalysts for CO2 hydrogenation to methanol have received intense attention. Herein, we developed new and efficient Co-In based catalysts (the composite of Co3InC0.75 and In2O3) by Prussian Blue analogues (PBA) pyrolysis. And a series of Co3InC0.75-In2O3 composites with tunable proportion of Co3InC0.75 and In2O3 has been prepared. The experimental results demonstrate the Co3InC0.75-In2O3 catalysts have high catalytic CO2 hydrogenation performance into methanol, reaching a methanol yield up to 0.62 gMeOHgcat−1h−1 at 300 °C, 5 MPa, 24000 cm3STPgcat−1h−1, and H2/CO2 = 3:1, the high reaction stability and air resistance. The synergetic effects between Co3InC0.75 and In2O3 for the enhanced methanol production were confirmed by a series of characterizations, and a positive correlation between methanol production activity and the fraction of Co3InC0.75/In2O3 was well established.

Reactant enrichment in hollow void of Pt NPs@MnOx nanoreactors for boosting hydrogenation performance.

In confined mesoscopic spaces, the unraveling of a catalytic mechanism with complex mass transfer and adsorption processes such as reactant enrichment is a great challenge. In this study, a hollow nanoarchitecture of MnOx-encapsulated Pt nanoparticles was designed as a nanoreactor to investigate the reactant enrichment in a mesoscopic hollow void. By employing advanced characterization techniques, we found that the reactant-enrichment behavior is derived from directional diffusion of the reactant driven through the local concentration gradient and this increased the amount of reactant. Combining experimental results with density functional theory calculations, the superior cinnamyl alcohol (COL) selectivity originates from the selective adsorption of cinnamaldehyde (CAL) and the rapid formation and desorption of COL in the MnOx shell. The superb performance of 95% CAL conversion and 95% COL selectivity is obtained at only 0.5MPa H2 and 40min. Our findings showcase that a rationally designed nanoreactor could boost catalytic performance in chemoselective hydrogenation, which can be of great aid and potential in various application scenarios.

An unconventional direct path for the chemoselective hydrogenation of nitroarenes over a metal-free catalyst

In recent years, significant efforts have been devoted to the fabrication of heteroatom-doped carbon materials as ecofriendly catalysts to replace metal-based catalysts employed in the hydrogenation of nitroarenes. However, the reaction pathway of metal-free catalysts has not been thoroughly studied. In this study, nitrogen-doped hollow hierarchical porous carbon materials have been successfully prepared. The porous nitrogen-doped carbon was prepared by carbonizing at 900°C (PNC-900) and exhibited an exceptional catalytic performance in the chemoselective hydrogenation of nitroarenes with high tolerance to various substrates under mild reaction conditions. The analysis of the experimental results and characterizations, revealed that graphitic N species were the primary catalytic active sites and played a crucial role in efficient hydrogenation. The reaction followed a special direct path in the hydrogenation of nitrobenzene (NB) owing to the absence of nitrosobenzene (NSB) as an intermediate, which was markedly different from the other metal-free catalysts. Moreover, the PNC-900 catalyst exhibited excellent reactivity and selectivity even after six cycling tests, thus demonstrating unconventional high performance in terms of both recyclability and stability.

MXene-supported single-atom and nano catalysts for effective gas-phase hydrogenation reactions

Transition metal carbides are known as efficient catalysts or catalyst supports and two-dimensional carbides (MXenes) offer renewed possibilities to anchor metal atoms and promote catalytic performances. This paper first presents an in-depth study of the elaboration of Pt or Pd-loaded Ti3C2Tx MXenes and their unstacking for gas-phase catalysis investigations, along with step-by-step characterization by XRD, XPS, SEM and STEM. In particular, the influence of the MXene preparation method (HF vs. LiF-HCl etchants) on surface structure/composition and metal dispersion/oxidation state is disclosed. Second, the catalytic hydrogenation performances of these materials are reported, and reveal the interest of low-loaded Pt/MXene single-atom catalysts in terms of activity, selectivity and resistance to sintering. They present an unusually high selectivity to 2-butene – without butane formation – in butadiene hydrogenation, a model reaction of applied interest for the petrochemical industry. Moreover, in CO2 reduction to CO (reverse water-gas shift reaction, relevant to greenhouse-gas valorization), these catalysts exhibit up to 99 % selectivity and a superior Pt-molar activity with respect to oxide-supported references. This work may stimulate the elaboration and investigation of other MXene-based systems for thermal heterogeneous catalysis, which remains rarely addressed on these materials.

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.

Engineering the Quaternary Hydrotalcite-Derived Ce-Promoted Ni-Based Catalysts for Enhanced Low-Temperature CO2 Hydrogenation into Methane.

Ce-promoted NiMgAl mixed-oxide (NiCex-C, x = 0, 1, 5, 10) catalysts were prepared from the quaternary hydrotalcite precursors for CO2 hydrogenation to methane. By engineering the Ce contents, NiCe5-C showed its prior catalytic performance in low-temperature CO2 hydrogenation, being about three times higher than that of the Ce-free NiCe0-C catalyst (turnover frequency of NiCe5-C and NiCe0-C: 11.9 h-1 vs. 3.9 h-1 @ 225 °C). With extensive characterization, it was found that Ce dopants promoted the reduction of NiO by adjusting the interaction between Ni and Mg(Ce)AlOx support. The highest ratio of surface Ni0/(Ni2+ + Ni0) was obtained over NiCe5-C. Meanwhile, the surface basicity was tailored with Ce dopants. The strongest medium-strength basicity and highest capacity of CO2 adsorption was achieved on NiCe5-C with 5 wt.% Ce content. The TOF tests indicated a good correlation with medium-strength basicity over the NiCex-C samples. The results showed that the high medium-strength and Ce-promoted surface Ni0 species endows the enhanced low-temperature catalytic performance in CO2 hydrogenation to methane.

Hydrogenation of CO2 to higher alcohols on an efficient Cr-modified CuFe catalyst

CO2 hydrogenation to higher alcohols (C2+OH) is a promising approach to achieve carbon recycling, but it is a challenge due to complex reaction network. Herein, various Cr-modified CuFe (Cr(x)-CuFe) catalysts were prepared, and their catalytic performance and reaction mechanism in CO2 hydrogenation to C2+OH were investigated. Introduction of small amounts of Cr enhances the interaction between Cu and Fe species, which alleviates CO over-dissociation and inhibits generation of iron carbides. In contrast, more acetate and acetaldehyde intermediates are produced via promoting the reaction of CHx with non-dissociated CO. Cr(1%)-CuFe showed CO2 conversion, C2+OH selectivity and space-time yield (STY) as high as 38.4%, and 29.2% and 104.1 mg gcat−1 h−1, at 320 °C, 4.0 MPa and GHSV of 6000 mL gcat−1 h−1. Interestingly, C2+OH STY was further elevated to 268.5 mg gcat−1 h−1, with a catalytic lifetime of at least 120 h, when GHSV was increased to 48000 mL gcat−1 h−1.

Role of the structure and morphology of zirconia in ZnO/ZrO2 catalyst for CO2 hydrogenation to methanol

The global carbon dioxide (CO2) emission problem is getting increasingly severe nowadays. Hence a suitable CO2 hydrogenation technology to obtain methanol is an efficient way to achieve carbon neutrality. Zinc oxide (ZnO) nanoparticles were loaded on zirconium dioxide (ZrO2) with different morphologies via the impregnation method. This was followed by the investigation of the effect of zirconia structure and morphology on the interfacial synergy manifested in the catalysts and the catalytic performance in CO2 hydrogenation. The results showed that the CO2 conversion of the ZnO/ZrO2 catalyst possessing a hollow nanoframe-like morphology was significantly enhanced. This catalyst also exhibited the highest methanol space-time yield, which was 1.78 times higher than that of the ZnO/ZrO2 catalyst having an aggregate shape of irregular particles. The unique morphology effectively inhibited the transition of the metastable tetragonal ZrO2 (t-ZrO2) to the monoclinic ZrO2 (m-ZrO2) while forming a special interfacial structure with the loaded ZnO to strengthen the interfacial interaction. This enhanced the hydrogen activation capacity and generated more oxygen vacancies favorable to the activation of CO2.

Depositing Pd on the outmost surface of Pd1Ni/SiO2 single-atom alloy via atomic layer deposition for selective hydrogenation of acetylene

Supported Pd single-atom alloy (SAA) catalysts are selective in acetylene semi-hydrogenation. However, it is a challenge to prepare Pd SAA where Pd single atoms dispersed on the outmost surface of the catalysts because the Pd atoms on Pd SAA prepared by conventional impregnation distribute inside the alloyed particle or on the support surface after activation. In this work, we firstly synthesized Ni/SiO2 nanocatalysts by impregnation, followed by H2 reduction to generate metal Ni particles on SiO2. Subsequently, Pd single atoms are selectively deposited on the Ni particle surface by atomic layer deposition (ALD). The Pd species on the Pd1Ni/SiO2 prepared by ALD dispersed on the outmost surface of catalyst, presenting the improved catalytic performances in acetylene hydrogenation, as compared to a reference Pd1Ni/SiO2 catalyst prepared by impregnation. The Pd1Ni/SiO2 catalyst prepared by ALD with 5 cycles (0.04 wt. %Pd, 5c-Pd1Ni/SiO2) shows both superior hydrogenation activity (92 %) and selectivity (88 %) under mild temperature (80 °C) in the selective semi-hydrogenation of acetylene. Moreover, the specific activity of the 5c-Pd1Ni/SiO2 catalyst is the highest, as compared to the catalysts reported in literature. Therefore, we conclude that the metal single atoms on metal SAA catalyst prepared by ALD locate on the outmost surface of the catalyst, presenting the unusual catalytic performances in catalysis.