Catalytic Reaction Research Articles

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.

Reduced graphene oxide encapsulated octahedral NiSe2 nanocrystals with dominant {111} crystal facets for efficient hydrogen evolution reaction

Regulating the exposed crystal facets of electrocatalysts is an effective means to enhance their electrocatalytic activity. However, related studies have focused mainly on traditional noble metals or metal oxides based electrocatalysts, while the research on crystal facets dependent electrocatalytic activity of metal selenides is still very rare. Here, crystal facets effect of cubic NiSe2 in electrocatalytic HER was studied. It was shown that octahedral NiSe2 nanocrystals dominated by active {111} crystal facets exhibited significantly enhanced HER activity. Moreover, by encapsulating the octahedral NiSe2 nanocrystals into reduced graphene oxide (rGO) nanosheet networks, further improvement in their HER activity could be achieved. First principles calculations and experimental characterization indicated that {111} crystal facts of NiSe2 had abundant surface active sites and ideal catalytic reaction energy barriers. This study not only expands the research on crystal facets-dependent HER activity, but also gains a deep understanding of the electrocatalytic mechanism.

CO2 capture and H2 production performance of calcium-based sorbent doped with iron and cerium during calcium looping cycle

As the interest in environmentally-friendly energy processes increases, many studies have been focused on producing hydrogen as an alternative energy carrier via catalytic reaction processes. Sorption enhanced water gas shift (SEWGS) that combines WGS and in situ CO2 removal is a promising technology for high-purity H2 production and CO2 capture. In this study, Fe/Ce-modified CaO-Ca12Al14O33 bi-functional porous nanotubes were synthesized in one step by template method and applied for H2 production from SEWGS process. The unique porous nanotube structure fully exposes the catalytic active sites and facilitates the gas-solid transport, resulting in the excellent H2 production and CO2 capture performance in SEWGS/regeneration cycles. The introduction of Ce enhances the basicity of the nanotube material, thereby increasing the affinity for CO2. The interaction of Fe-Ce improves the redox capability of Fe2+ and Fe3+, which is beneficial to the conversion of CO. In addition, the formed Ca2Fe2O5 and Ca2CeO4 both increase the concentration of oxygen vacancies, further enhancing the SEWGS reactivity of the material. The optimal molar ratio of Fe/Ce/Al/Ca is 10/3/10/100, and the CO conversion, H2 concentration, CO2 capture capacity of the Fe/Ce-modified bi-functional material were 76.9 %, 70.1 % and 83.2 % after 20 cycles. The effect of Fe/Ce doping on CaO-based materials was investigated at the molecular level using density functional theory (DFT). The results demonstrate that the addition of Ce can effectively maintain the stable structure of Fe-CaO-based materials. The modification of Fe/Ce is expected to promote efficient H2 generation from CaO-based materials through the SEWGS process.

A Simple and Cost-Effective FeCl3-Catalyzed Functionalization of Cellulose Nanofibrils: Toward Adhesive Nanocomposite Materials for Medical Implants.

In the present work, we explored Lewis acid catalysis, via FeCl3, for the heterogeneous surface functionalization of cellulose nanofibrils (CNFs). This approach, characterized by its simplicity and efficiency, facilitates the amidation of nonactivated carboxylic acids in carboxymethylated cellulose nanofibrils (c-CNF). Following the optimization of reaction conditions, we successfully introduced amine-containing polymers, such as polyethylenimine and Jeffamine, onto nanofibers. This introduction significantly enhanced the physicochemical properties of the CNF-based materials, resulting in improved characteristics such as adhesiveness and thermal stability. Reaction mechanistic investigations suggested that endocyclic oxygen of cellulose finely stabilizes the transition state required for further functionalization. Notably, a nanocomposite, containing CNF and a branched low molecular weight polyethylenimine (CNF-PEI 800), was synthesized using the catalytic reaction. The composite CNF-PEI 800 was thoroughly characterized having in mind its potential application as coating biomaterial for medical implants. The resulting CNF-PEI 800 hydrogel exhibits adhesive properties, which complement the established antibacterial qualities of polyethylenimine. Furthermore, CNF-PEI 800 demonstrates its ability to support the proliferation and differentiation of primary human osteoblasts over a period of 7 days.

Microstructured gas-liquid-(solid) interfaces: A platform for sustainable synthesis of commodity chemicals.

Gas-liquid-solid catalytic reactions are widespread in nature and man-made technologies. Recently, the exceptional reactivity observed on (electro)sprayed microdroplets, in comparison to bulk gas-liquid systems, has attracted the attention of researchers. In this perspective, we compile possible strategies to engineer catalytically active gas-liquid-(solid) interfaces based on membrane contactors, microdroplets, micromarbles, microbubbles, and microfoams to produce commodity chemicals such as hydrogen peroxide, ammonia, and formic acid. In particular, particle-stabilized microfoams, with superior upscaling capacity, emerge as a promising and versatile platform to conceive high-performing (catalytic) gas-liquid-(solid) nanoreactors. Gas-liquid-(solid) nanoreactors could circumvent current limitations of state-of-the-art multiphase reactors (e.g., stirred tanks, trickle beds, and bubble columns) suffering from poor gas solubility and mass transfer resistances and access gas-liquid-(solid) reactors with lower cost and carbon footprint.

Triazine-wingtips accelerated NHC-Pd catalysed carbonylative Suzuki cross-coupling reaction

Triazine conjugated N-heterocyclic carbene palladium complexes were synthesized for reducing the Pd amount in the catalysts to the ppm levels. This work reports the carbonylative Suzuki-Miyaura coupling of aryl iodides catalyzed by N-heterocyclic carbenes palladium with triazine wingtips (T-NHC-Pd). More importantly, the palladacycles have been used to generate high turnover numbers (TON's) and turnover frequencies (TOF's).

Screening the optimal Cox/CeO2(110) (x = 1–6) catalyst for methane activation in coalbed gas

The challenges posed by energy and environmental issues have forced mankind to explore and utilize unconventional energy sources. It is imperative to convert the abundant coalbed gas (CBG) into high value-added products, i.e., selective and efficient conversion of methane from CBG. Methane activation, known as the “holy grail”, poses a challenge to the design and development of catalysts. The structural complexity of the active metal on the carrier is of particular concern. In this work, we have studied the nucleation growth of small Co clusters (up to Co6) on the surface of CeO2(110) using density functional theory, from which a stable loaded Co/CeO2(110) structure was selected to investigate the methane activation mechanism. Despite the relatively small size of the selected Co clusters, the obtained Cox/CeO2(110) exhibits interesting properties. The optimized Co5/CeO2(110) structure was selected as the optimal structure to study the activation mechanism of methane due to its competitive electronic structure, adsorption energy and binding energy. The energy barriers for the stepwise dissociation of methane to form CH3*, CH2*, CH*, and C* radical fragments are 0.44, 0.55, 0.31, and 1.20 eV, respectively, indicating that CH* dissociative dehydrogenation is the rate-determining step for the system under investigation here. This fundamental study of metal-support interactions based on Co growth on the CeO2(110) surface contributes to the understanding of the essence of Co/CeO2 catalysts with promising catalytic behavior. It provides theoretical guidance for better designing the optimal Co/CeO2 catalyst for tailored catalytic reactions.

Selective catalytic reduction of NO by CO over spinel CuFe2O4 catalyst: The vital role of oxygen vacancies

Oxygen vacancies are widely employed to augment the catalytic reactivity in the selective catalytic reduction of NO by CO (CO-SCR) process. Herein, the specific promotion mechanism of oxygen vacancies was intensively explored through a series of CuFe2O4 catalysts via experiments and density functional theory (DFT) simulations. After the modification of oxygen vacancies, NO conversion was enhanced by 20 %-32 % and N2 selectivity was improved. Characterizations revealed that the redox performance, NO adsorption and activation capacity, active centers, and acidic sites of CuFe2O4 can be improved by enriched oxygen vacancies, contributing to the superior CO-SCR performance. DFT results identified that the adsorption energies of reactants were elevated and the intermediate reaction energy barriers were decreased with more oxygen vacancies. Furthermore, the CO-SCR reaction pathways with CuFe2O4 catalyst were proposed according to in-situ test results: it follows the Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms in the low-temperature range (50–250 ℃) and the Marse-van-Krevelen (Mvk) mechanism in the high-temperature range (≥250 ℃). Overall, this work highlights the bright prospects of oxygen vacancies on the modification of CO-SCR catalysts.

Controllable Synthesis of Titanium Silicon Molecular Zeolite Nanosheet with Short b-Axis Thickness and Application in Oxidative Desulfurization.

Titanium silicon molecular zeolite (TS-1) plays an important role in catalytic reactions due to its unique nanostructure. The straight channel on TS-1 was parallel to the orientation of the short b-axis and directly exposed to the aperture of the 10-member ring with a diameter of 0.54 nm × 0.56 nm. This structure could effectively reduce the diffuse restriction of bulk organic compounds during the oxidative desulfurization process. As a kind of cationic polymer electrolyte, polydimethyldiallyl ammonium chloride (PDDA) contains continuous [C8H16N+Cl-] chain segments, in which the Cl- could function as an effective structure-directing agent in the synthesis of nanomaterials. The chain of PDDA could adequately interact with the [0 1 0] plane in the preparation process of zeolite, and then the TS-1 nanosheet with short b-axis thickness (6 nm) could be obtained. The pore structure of the TS-1 nanosheet is controlled by regulating the content of PDDA. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 physical adsorption analysis, infrared absorption spectrum and ultraviolet-visible spectrum were used to determine the TS-1. The thinner nanosheets exhibit excellent catalytic performance in oxidative desulfurization of dibenzothiophene (DBT), in which the removal rate could remain at 100% after three recycles. Here, the TS-1 nanosheet with short b-axis thickness has a promising future in catalytic reactions.

Operando Spectroscopy to Understand Dynamic Structural Changes of Solid Catalysts.

Solid materials like heterogeneous catalysts are highly dynamic and continuously tend to change when exposed to the reaction environment. To understand the catalyst system under true reaction conditions,operando spectroscopy is the key to unravel small changes, which can ultimately lead to a significant difference in catalytic activity and selectivity. This was also the topic of the 7th International Congress on Operando Spectroscopy in Switzerland in 2023. In this article, we discuss various examples to introduce and demonstrate the importance of this area, including examples from emission control for clean air (e.g. CO oxidation), oxidation catalysis in the chemical industry (e.g. oxidation of isobutene), future power-to-X processes (electrocatalysis, CO2 hydrogenation to methanol), and non-oxidative conversion of methane. All of these processes are equally relevant to the chemical industry. Complementary operando techniques such as X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and Raman spectroscopy were utilized to derive the ultimate structure of the catalyst. The variety of conditions requires distinctly different operando cells that can reach a temperature range of 400-1000 °C and pressures up to 40 bar. The best compromise for both the spectroscopy and the catalytic reaction is needed. As an outlook, we highlight emerging methods such as modulation-excitation spectroscopy (MES) or quick-extended X-ray absorption fine structure (QEXAFS) and X-ray photon in/out techniques, which can provide better sensitivity or extend X-ray based operando studies.

Current Developments in Operando Electron Paramagnetic Resonance Spectroscopy.

Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for in situ/operando tracking of catalytic reactions that involve paramagnetic species either as a catalyst (e.g. transition metal ions or defects), reaction intermediates (radicals) or poisoning agents such as coke. This article provides a summary of recent experimental examples and developments in resonator design as well as detection schemes that were carried out in our group. Opportunities for applying this technique are illustrated by examples, including studies of transition metal exchanged zeolites and metal-free zeolites as well as metal oxide catalysts. The inherent limitations of EPR applied at high temperatures are discussed, as well as strategies in reducing or lifting these restrictions are evaluated and ideas for future improvements and methodologies are discussed.

In situ formation of inhibitor species through catalytic surface reactions during area-selective atomic layer deposition of TaN.

Small molecule inhibitors (SMIs) have been gaining attention in the field of area-selective atomic layer deposition (ALD) because they can be applied in the vapor-phase. A major challenge for SMIs is that vapor-phase application leads to a disordered inhibitor layer with lower coverage as compared to self-assembled monolayers, SAMs. A lower coverage of SMIs makes achieving high selectivity for area-selective ALD more challenging. To overcome this challenge, mechanistic understanding is required for the formation of SMI layers and the resulting precursor blocking. In this study, reflection adsorption infrared spectroscopy measurements are used to investigate the performance of aniline as an SMI. Our results show that aniline undergoes catalytic surface reactions, such as hydrogenolysis, on a Ru non-growth area at substrate temperatures above 250 °C. At these temperatures, a greatly improved selectivity is observed for area-selective TaN ALD using aniline as an inhibitor. The results suggest that catalytic surface reactions of the SMI play an important role in improving precursor blocking, likely through the formation of a more carbon-rich inhibitor layer. More prominently, catalytic surface reactions can provide a new strategy for forming inhibitor layers that are otherwise very challenging or impossible to form directly through vapor-phase application.

Backstepping synchronization control for four-dimensional chaotic system based on DNA strand displacement

Backstepping control is an important nonlinear control design method, which realizes the control of complex systems by constructing control law step by step, and has significant advantages for dealing with complex nonlinear systems. This article proposes a synchronization technique for four-dimensional chaotic systems using a combination of backstepping control method and DNA strand displacement technology. By relying on theoretical knowledge of DNA molecules, five basic chemical reaction modules such as trigger reaction, reference reaction, catalytic reaction, annihilation reaction and degradation reaction are given to construct a four-dimensional DNA chaotic system. On the basis of the relevant theory of chaotic dynamics, the constructed system is analyzed by Lyapunov exponent diagram and spectral entropy complexity algorithm, and the results come to the conclusion that the system reveals extremely complex and varied dynamic behaviors. Combining DNA strand displacement technology with backstepping control method, four controllers are developed to ensure that the trajectories of two homogeneous chaotic systems are synchronized. The numerical simulation results validate the feasibility and applicability of the proposed method. The method proposed in this paper may provide some references in the field of DNA molecular chaos synchronization control.

Furfural Hydrogenation Over Reduced Pure (LaBO3) and Substituted (LaB0.5B'0.5O3) (B, B': Fe, Co, Ni) Perovskites

AbstractA series of pure and 50 % substituted Fe‐containing (LaFeO3, LaFe0.5Ni0.5O3 and LaFe0.5Co0.5O3) and Co/Ni‐containing (LaCoO3, LaNiO3, and LaCo0.5Ni0.5O3) perovskites were used as precursors to synthesize metallic reduced catalysts to be tested for the liquid hydrogenation of furfural. The catalytic reaction was carried out in a batch reactor at 200 °C and 3.0 MPa of H2 pressure. The calcined perovskites and reduced catalysts were characterized by X‐ray diffraction (XRD), N2 physisorption at 77 K, temperature programmed reduction (H2‐TPR), temperature programmed CO2 and NH3 desorption (CO2‐TPD and NH3‐TPD), Atomic Absorption Spectroscopy (AAS) and X‐ray photoelectron spectroscopy (XPS) techniques. The LaCo0.5Ni0.5O3 reduced catalyst display the highest activity in furfural conversion, which was attributed to a cooperative effect between highly dispersed nickel and cobalt metal nanoparticles after reduction process. The effect of the nature of B‐cation have a high impact on the products selectivity in the hydrogenation of furfural, suggesting that enriched‐Ni metal surface was selectivity to tetrahydrofurfuryl alcohol, meanwhile enriched‐Co metal surface was selective to furfuryl alcohol formation, which was also supported with adsorption mode of furfural over the active sites obtained by quantum calculation.

Recent progress of waste plastic upcycling based on multifunctional zeolite catalysts

The chemical upcycling method is a promising strategy to alleviate the pollution problem of waste plastics by tapping into their intrinsic value and converting them into high value-added products. Zeolite-based catalysts are one of the surprising and efficient classes of thermocatalytic materials that have recently attracted considerable attention for waste plastic upcycling. They are designed for targeted applications with a wide range of adjustable acidic sites, multiple pore structures, and synergistic interactions with surface metals. In this review, we categorize plastics being converted into different high-value products and introduce the role of zeolite-based catalysts in the thermal upcycling of plastics. The structure-performance relationships of zeolite-based catalysts in catalytic reactions are discussed in depth. Finally, the future development of these multifunctional catalysts applied to the upcycling of plastics is outlined.

Predicting and probing the local temperature rise around plasmonic core-shell nanoparticles to study thermally activated processes.

Ultrafast spectroscopy can be used to study dynamic processes on femtosecond to nanosecond timescales, but is typically used for photoinduced processes. Several materials can induce ultrafast temperature rises upon absorption of femtosecond laser pulses, in principle allowing to study thermally activated processes, such as (catalytic) reactions, phase transitions, and conformational changes. Gold-silica core-shell nanoparticles are particularly interesting for this, as they can be used in a wide range of media and are chemically inert. Here we computationally model the temporal and spatial temperature profiles of gold nanoparticles with and without silica shell in liquid and gas media. Fast rises in temperature within tens of picoseconds are always observed. This is fast enough to study many of the aforementioned processes. We also validate our results experimentally using a poly(urethane-urea) exhibiting a temperature-dependent hydrogen bonding network, which shows local temperatures above 90 ◦C are reached on this timescale. Moreover, this experimentally shows the hydrogen bond breaking in such polymers occurs within tens of picoseconds.

TEMPO immobilized polymeric Janus dumbbell: Assembly and catalysis at liquid-liquid interface

Pickering interfacial catalysts (PICs) have emerged as a promising solution for simultaneously enhancing and catalyzing liquid-liquid biphasic reactions. In this study, we successfully synthesized dumbbell-shaped Janus structured polymeric nanoparticles with one side anchored imidazolium-TEMPO (im-C4-TEMPO@JPP) as Pickering interfacial catalyst for the oxidation of alcohols using the Anelli-Montanari reaction system. In the Pickering emulsion system, the im-C4-TEMPO@JPPs particles are assembled at the W/O interface due to the hydrophilicity of imidazolium-TEMPO anchored lobe which enables excellent amphiphilic character of the polymeric Janus dumbbell. Moreover, the im-C4-TEMPO@JPPs particles reduce the interfacial tension from 27.82 to 18.43 mN/m. This excellent interfacial adsorption capacity of im-C4-TEMPO@JPPs strongly stabilizes the water/dichloromethane Pickering emulsion over two months (emulsion volume fraction >90 %), thus providing an efficient reaction platform for liquid-liquid biphasic reactions. As a result, the constructed Pickering emulsion system efficiently catalyzes the oxidation of cinnamyl alcohol to cinnamaldehyde under static conditions. After 1 hour of reaction, the conversion of cinnamyl alcohol achieved 97.1 % with a selectivity of 99 %, nearly the same level relative to stirring intensified biphasic reaction. Hence, this novel PIC effectively improves the efficiency and sustainability of liquid-liquid biphasic catalytic reactions.

Synergistic role of MoS2 in gelation-induced fabrication of graphene oxide films.

Supporting materials for electrocatalysts must exhibit relative chemical inertness to facilitate unimpeded movement of gas, and demonstrate electrical conductivity to promote efficient electron transfer to the catalyst. Conventional catalyst electrodes, such as glassy carbon, carbon cloths, or Ni foam, are commonly employed. However, the challenge lies in the limited stability observed during testing due to the relatively weak adhesion between the catalyst and the electrode. Addressing this limitation is crucial for advancing the stability and performance of catalyst-electrode systems in various applications. Here, we suggest a novel fabrication method for a freestanding conducting film, accomplished through gelation, incorporating 1T-MoS2 and graphene oxide. 1T-MoS2 nanosheets play a crucial role in promoting the reduction of graphene oxide (GO) on the Zn foil. This contribution leads to accelerated film formation and enhanced electrical conductivity in the film. The synergistic effect also enhances the film's stability as catalyst supports. This study provides insights into the effective utilization of MoS2 and graphene oxide in the creating of advanced catalyst support systems with potential applications in diverse catalytic reaction.

Simulation analysis of micro-explosion during emulsification feeding of residue fluidized catalytic cracking

Residue Fluidized Catalytic Cracking (RFCC) is one of the key processes to convert heavy oil into light products in refineries. The fast and sufficient vaporization of the feedstock in the FCC riser reactor can promote the catalytic cracking reaction and is beneficial for increasing the yield of light products and decreasing the yield of coke. However, fast vaporization of residue oil is extremely challenging due to its high density and viscosity. Recently, emulsified feeding technology is seen as a potential method that can effectively enhance the vaporization of RFCC feedstock. Computational Fluid Dynamics (CFD) simulations were performed in order to reveal the micro-explosion mechanism of emulsion droplet in the riser reactor. The CFD model was validated against experimental results from literature. The model was used to study micro-explosion of emulsified droplets in the gas phase and at the catalyst particle surface separately. It was found that due to the micro-explosion of emulsion oil droplets in producing large number of tiny droplets, the secondary atomization of droplets can be realized. In the gas phase, the interfacial area of emulsion droplet can be improved by 5 to 15 times. At the catalyst surface, the percentage of liquid film coverage was reduced by 32.6 %, and the droplet diameter was reduced by 92 % for the emulsified feeding technology. These results indicate that the vaporization efficiency of the residual oil can be greatly improved by this technology.

Photocatalytic water oxidation by iron and copper phthalocyanine complexes immobilized on Fe3O4@SiO2@TiO2 under visible light irradiation

In this research, the heterogeneous catalysts of Fe3O4@SiO@TiO‐FePc and Fe3O4@SiO@TiO‐ CuPcN (FePc = iron (II) phthalocyanine and CuPcN = copper (II) tetraazaphthalocyanine), termed respectively as nanocomposites 1 and 2, were prepared by immobilizing the FePc and CuPcN complexes on the Fe3O4@SiO@TiO surface and used for the photocatalytic water oxidation reaction. Since phthalocyanine complexes have received very little attention as photocatalysts for water oxidation, the advantage of the synthesized photocatalyst owes to the ability of the phthalocyanine complex grafted on the titanium substrate to oxidize water in the photocatalytic reaction. The prepared nanocomposites were then studied by diffraction (XRD), scanning electron microscopy (SEM), energy‐dispersive X‐ray (EDX), Fourier transform infrared (FT‐IR) spectroscopies, thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), inductively coupled plasma‐optical emission spectroscopy (ICP‐OES), Brunauer–Emmett–Teller (BET) analysis, ultraviolet diffuse reflectance (DRS), and photoluminescence (PL) spectroscopies. The photocatalytic response of water oxidation by nanocomposites 1 and 2 was investigated in the presence of silver nitrate as an electron recipient at ambient temperature. The progress of the water oxidation reaction was monitored with an oxygen meter. The amount of oxygen generated in the presence of nanocomposites 1 and 2 under visible light irradiation was found to be 2.6 and 2.1 mg L−1, respectively. Owing to the existence of magnetic material, these nanocomposites can be effortlessly removed from the response medium with an external magnet. The involved nanocomposites can be used up to three times in catalytic water oxidation reactions with no significant change in their photocatalytic activity.