Monolithic Catalysts Research Articles

Development and Evaluation of Ni–Cu–Pt Monolithic Catalysts for Improved Ethanol Autothermal Reforming and Hydrogen Production

Development and Evaluation of Ni–Cu–Pt Monolithic Catalysts for Improved Ethanol Autothermal Reforming and Hydrogen Production

Upcycling iron oxide scale slag into a high‐performance, sustainable ozone catalyst

Upcycling iron slag into a monolithic catalyst has led to low‐cost heterogeneous catalytic ozonation (HCO) strategies for water treatment. The primary industrial challenges are the low chemical oxygen demand (COD) reduction rate in treating authentic wastewater and difficulties sustaining close‐loop reaction cycles. In this study, we present a monolithic catalyst transformed from low‐cost iron oxide scale slag (IOSM) for highly efficient, sustainable ozone catalysis. The IOSM, constituted of 59.70% Fe2O3 and 40.30% Fe3O4, effectively decomposes ozone into superoxide radicals (·O2⁻) through a close‐loop cyclic reaction facilitated by interfacial charge transfer. This mechanism enables super‐fast degradation of 100 mg·L⁻¹ tetracycline at ozone concentrations below 1.00 mg·L⁻¹ in just four minutes, with the iron leaching merely at 59 μg·L‐1 after 10 cycles. In tests with authentic antibiotic wastewater, the IOSM‐based HCO system achieves a record‐breaking 81.70% COD reduction within two hours. This research underscores the potential of upcycling industrial waste into highly effective ozone catalysts for sustainable practices in wastewater treatment.

Upcycling iron oxide scale slag into a high-performance, sustainable ozone catalyst.

Upcycling iron slag into a monolithic catalyst has led to low-cost heterogeneous catalytic ozonation (HCO) strategies for water treatment. The primary industrial challenges are the low chemical oxygen demand (COD) reduction rate in treating authentic wastewater and difficulties sustaining close-loop reaction cycles. In this study, we present a monolithic catalyst transformed from low-cost iron oxide scale slag (IOSM) for highly efficient, sustainable ozone catalysis. The IOSM, constituted of 59.70% Fe2O3 and 40.30% Fe3O4, effectively decomposes ozone into superoxide radicals (·O2⁻) through a close-loop cyclic reaction facilitated by interfacial charge transfer. This mechanism enables super-fast degradation of 100 mg·L⁻¹ tetracycline at ozone concentrations below 1.00 mg·L⁻¹ in just four minutes, with the iron leaching merely at 59 μg·L-1 after 10 cycles. In tests with authentic antibiotic wastewater, the IOSM-based HCO system achieves a record-breaking 81.70% COD reduction within two hours. This research underscores the potential of upcycling industrial waste into highly effective ozone catalysts for sustainable practices in wastewater treatment.

Roles of Divinylbenzene Co‐Cross‐Linker in a Threefold Cross‐Linked Polystyrene–Phosphine Hybrid Monolith: Impact of Cross‐linking Degree on Catalytic Performance

AbstractContinuous‐flow organic transformations using immobilized catalysts are crucial for green and sustainable chemistry. Cross‐linked polymer ligands offer high stability, ease of recovery through filtration, and thus enhance performance in continuous‐flow reactions via transition‐metal catalysis. Additionally, the cross‐linking structure of the polymer support creates a unique reaction platform that controls the coordination behavior of the supported ligands and stabilizes the metal catalysts. However, insights into the material‐based design for preparing highly active and durable immobilized metal catalysts are still limited. In this report, we propose a straightforward approach to boost both selective mono‐coordination and effective stabilization of metal complexes. We developed threefold cross‐linked polystyrene‐triphenylphosphine hybrid monoliths with cross‐linking structures adjusted by varying the content of divinylbenzene as co‐cross‐linker. The coordination behaviors and metal‐support interactions of these monoliths were evaluated, highlighting the importance of co‐cross‐linker content in site‐isolating phosphine units and stabilizing metal centers via arene‐metal interactions on the polystyrene network. By optimizing the cross‐linking structure, the monolith catalysts demonstrated exceptionally high catalytic activity and durability in Pd‐catalyzed C−Cl transformations, such as Suzuki–Miyaura cross‐couplings and Buchwald‐Hartwig aminations in continuous flow. This underscores the utility of our monolith system in challenging transition‐metal catalysis.

Influence of Dopants on Pt/Al2O3-Based Monolithic Catalysts for Autothermal Oxidative Coupling of Methane

Autothermal oxidative coupling of methane (OCM) is a highly attractive approach for methane utilization. If platinum-based catalysts are operated in short-contact-time reactors with high space velocities, high methane conversion can be achieved. Using a 1 wt.% Pt/Al2O3 catalyst as a benchmark, the present study elucidates how different dopants, namely Ni, Sn, and V2O5, affect the OCM reaction. Kinetic catalyst tests reveal that acetylene (C2H2) is the predominant C2 product, irrespective of the catalyst formulation or operation conditions. Furthermore, the use of bimetallic catalysts allows either for the maintenance or even the improvement of the C2 selectivity during OCM, which is attributed to synergistic effects that occur when expensive Pt is partially replaced by cheaper dopants. In particular, the 1 wt.% Pt/Al2O3 reference catalyst yielded a maximum C2 selectivity of 8.2%, whereas the best-performing doped sample 0.25 wt.% Pt 0.75 wt.% V2O5/Al2O3 yielded a total C2 selectivity of 11.3%.

Electrochemical synthesized copper mesh catalysts for catalytic combustion: A comprehensive study of Mn doping and atmospheric conditions during calcination

Metal-based monolithic catalysts offer significant advantages in heterogeneous catalysis attributed to their exceptional thermal conductivity and mechanical strength. However, controlling the loading of active components on metallic substrates remains a major challenge. Here, we synthesized a Mn-doped Cu mesh catalyst using a facile electrochemical method, allowing the active components to grow directly on Cu mesh without extra pretreatments or binding agents. The synthesized catalyst exhibits approximately a 30 % increase in carbon monoxide oxidation activity at 100°C and a 60 % increase in toluene oxidation activity at 240°C compared to the Mn-free Cu mesh catalyst. We found that calcination in inert gases enhances interactions between Cu and Mn species, leading to more oxygen vacancies and adsorption sites for reactants. This investigation paves the way for fabricating multi-metal monolithic catalysts on metallic substrates.

Post plasma-catalysis for room-temperature removal of gaseous styrene over monolithic nickel foam catalysts: Synergistic effect and stability test

Post plasma-catalysis for room-temperature removal of gaseous styrene over monolithic nickel foam catalysts: Synergistic effect and stability test

Fe-based monolithic catalysts for Fenton-like degradation of organic dyes: The important role of Fe2(OH)3Cl species

Fe-based monolithic catalysts for Fenton-like degradation of organic dyes: The important role of Fe2(OH)3Cl species

Low-Temperature NH3-SCR Technology for Industrial Application of Waste Incineration: An Overview of Research Progress

Selective catalytic reduction of nitrogen oxides with NH3 (NH3-SCR) was investigated deeper and deeper with poisoning factors such as H2O, SO2, heavy metals, etc. In order to remove the reheating process before the SCR reactor, the application trend of NH3-SCR technology in the non-power industry is concentrated on the condition of low temperature even ultra-low temperature. The present study summarizes the research process of SO2 and H2O resistance of NH3-SCR catalysts under low temperatures related to the working conditions of municipal solid waste incineration plants. In detail, the effects of a high content of H2O and low concentration of SO2 are reviewed. Other factors such as heavy metals, alkali, or alkaline earth metals in the reaction system, synergistic removal of NOx, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are addressed. Finally, the catalytic performance of assembled monolithic catalysts and pilot-scale experiments are also analyzed for the possibility of industrial application. Hopefully, in view of the questions outlined in this study, valuable insights could be taken into consideration for the development of NH3-SCR in waste incineration.

Effects of Slurry Composition and Interfacial Adhesion of Monolithic Coatings on FeCrAl Honeycombs

Excellent coating adhesion is a crucial requirement for monolithic catalysts. Within this investigation, a Design of Experiments (DOEs) Taguchi approach was leveraged to construct a 9-factor-3-level matrix encompassing 27 parallel experiments. This framework was employed to scrutinize the pivotal elements influencing the adhesion of FeCrAl metal-based integral coatings, which were prepared using the slurry method. Moreover, an unprecedented endeavor was made to scrutinize the mechanism of coating delamination from the vantage points of macroscopic slurry, microscopic coatings, and nanoscale interfaces. The findings reveal the following: (1) The inclusion of a high-acidity additive (>5%) emerges as one of the pivotal factors in achieving superior adhesion, particularly when the boehmite content exceeds 1%. (2) The existence of binder-filled interstices within the coating, smaller by 1–2 orders of magnitude than the carrier particles, significantly contributes to heightened adhesion. (3) A bonding region of approximately 5 nm is present at the interfaces between carrier particles, resulting in augmented adhesion.

Producing a monolithic catalyst for the catalytic oxidization of dioxins by comparing extrusion and coating methods

Producing a monolithic catalyst for the catalytic oxidization of dioxins by comparing extrusion and coating methods

Development and performance evaluation of a novel solar mid-and-low temperature receiver/reactor with packed metal foam

Solar-driven hydrogen production from methanol decomposition (MD) is an important method of storing solar energy as clean fuels and improving the solar energy utilization efficiency. Catalyst preparation is one of the key steps, but conventional Cu-ZnO-Al2O3 particle catalysts lead to uneven reactor temperature, reducing the efficient conversion of solar energy into fuels. To alleviate this challenge, a monolithic catalyst utilizing packed foamy copper as a carrier is developed with exceptional thermal and mass transfer properties. The experimental results validate its excellent performance in hydrogen production using MD. The absolute conversion increases by an average of 12.11 % at 250 °C and further by 14.43 % at 270 °C compared to the particle catalyst. Based on these findings, a novel solar reactor is proposed, and a multi-field coupling model is built. The comparative results verify the performance advantage of the developed solar thermochemical receiver/reactor with packed metal foam-based catalyst. It maintains high conversion rates and solar-to-fuel energy efficiency, while alleviating overheating problems caused by traditional particle catalysts. Under the design conditions, the new reactor significantly improves the absolute conversion of methanol and the energy efficiency of solar-to-fuel conversion by 4.57 % and 3.00 %, respectively, resulting in 92.64 % and 67.56 %. This study provides a theoretical basis and technical solution for more stable and efficient use of mid-and-low temperature solar energy.

Ozone-Catalytic Treatment of Automotive Exhaust

In the paper, an original design of an ozone-catalytic device, in which the process of ozone formation occurs directly inside the catalyst monolith of the honeycomb structure, is proposed for solving the problem of exhaust gases purification at the "cold start" of an automobile engine. For the considered device, various regimes of operation were examined, and the equations allowing us to calculate the concentrations of ozone depending on time were obtained. The developed mathematical model shows a significant decrease in ozone concentration after the "cold start" is over and the temperature of the exhaust gases increases, because of changes in the balance of various chemical reactions. Thus, the ozone concentration is maximum during a cold start, precisely when the lower temperatures do not allow other reactions than those of oxidation of toxic gases with ozone, and decreases by the time the catalytic unit warms up, when effective neutralization of toxic impurities becomes possible without the participation of ozone. The results of the mathematical modeling were confirmed by testing this device for purifying exhaust gases of a YaMZ-238M2 engine. The test results show that the use of ozone-catalytic reactions significantly increases the efficiency of neutralizing toxic impurities under cold start conditions, compared to the case when only catalytic reactions with oxygen without the participation of ozone are used.

Pd-Co Supported on Anodized Aluminium for VOCs Abatement: Reaction Mechanism, Kinetics and Applicability as Monolithic Catalyst

It has been found out that Pd-Co-based catalyst, supported on anodized aluminum, possesses very high activity in combustion reactions of C1–C6 alkanes and toluene. The catalyst characterization has been made by N2-pysisorption, XRD, SEM, XPS, FTIR, TEM, and EPR methods. In view of the great interest, methane combustion was investigated in detail. It is ascertained that the complete oxidation of methane proceeds by dissociative adsorption on PdO and formation of hydroxyl and methyl groups, the former being highly reactive, and it undergoes further reaction to oxygen-containing intermediates, whereupon HCHO is one of them. The presence of Co2+ cations promotes greatly oxygen adsorption. The dissociative adsorption is favored on neighboring Co2+ cations, leading to the formation of bridging peroxides. Further, the oxygen dissociates on the nearest Pd2+ cations. According to the results from the experimental data, instrumental methods, and the observed kinetics and DFT model calculations, it can be concluded that the reaction pathway over Pd+Co/anodic alumina support (AAS) catalyst proceeds most probably through Mars–van Krevelen. The obtained data on the kinetics were used for simulation of the methane combustion in a full-scale adiabatic reactor.

Foam Ti Supported Pd Catalysts for the Selective Hydrogenation of Nitroaromatics.

The selective hydrogenation of nitroaromatics plays an essential role in the chemical industry for the synthesis of anilines and their derivatives, which are known as crucial fine chemicals and pharmaceuticals. In this study, we demonstrate the preparation of Pd/Ti monolith catalyst containing well-isolated metallic Pd sites on Ti substrate through a simple impregnation method, showing remarkable catalytic properties in the selective hydrogenation of nitroaromatics containing various functional groups. Kinetic analyses reveal an apparent activation energy of 61 kJ/mol and the kinetic isotope effect (KH2/KD2) of ~1.7 in the hydrogenation of 3-chloronitrobenzene over Pd/Ti-200 ppm catalyst, indicating the facile dissociation of dihydrogen and the subsequent efficient hydrogenation. The Pd/Ti-200 ppm catalyst also demonstrates good stability and recyclability, maintaining its performance over multiple cycles. This simple but innovative approach not only enhances the efficiency of Pd catalysts in the selective hydrogenation of nitroaromatics but also offers significant potential for industrial applications in aniline production.

Topology optimization and numerical validation for heat transfer improvement in a packed-bed reactor with monolithic catalyst

This study focuses on optimizing heat transfer in packed-bed reactors by simplifying the problem to a two-dimensional steady-state heat conduction scenario. The objective is to efficiently arrange a limited volume of high-conductivity material to transport heat from the source to the low-conductivity heat-absorbing materials, representing the reacting fluid phase. The topology optimization problem is tackled using a density-based method that relies on a gradient-based algorithm. The optimized design is extruded and compared to a honeycomb internal structure using high-fidelity simulations for steam methane reforming. Results show a 6.04 % improvement in CH4 conversion for the optimized structure, highlighting the potential of this method to enhance monolithic catalysts, particularly in cases where heat transfer critically influences the reaction.

A monolithic self-supporting ZnFe2O4/ZnO/ZnNi foam photocatalyst and application in the decomposition of gaseous benzene

Volatile organic compounds (VOCs) are major air pollutants which seriously affect ecological environment and pose threats to human health. In this investigation, a monolithic self-supporting ZnFe2O4/ZnO/ZNF(ZFO/ZnO/ZNF) photocatalyst was developed by in-situ growing ZnFe2O4 and ZnO on ZnNi foam (ZNF). Using benzene as a representative of the target gaseous contaminants, the optimal 5ZFO/ZnO/ZNF achieved a 99.8 % removal efficiency and 99.7 % mineralization efficiency within 20 min at an initial benzene concentration of 600 ppm under simulated sunlight irradiation. Moreover, this catalyst presents the lower ullage during gas–solid reaction, and thus enables durable recycling reuse of the photocatalyst, which still retains a 95.8 % benzene decomposition after 30th consecutive run. The mechanism studies reveal that the metal-mediated Z-type heterostructure of ZFO/ZnO/ZNF enhances rapid transportation of the photo-generated electrons and promotes redox potential, leading to the excellent photocatalytic oxidation activity and mineralization efficiency. This study highlights the potential of self-supporting monolithic metal-mediated catalysts and provides a key strategy for effective VOCs degradation.

Robust palladium oxide nano-cluster catalysts using atomic ions and strong interactions for high-performance methane oxidation

Optimizing metal catalyst structures to achieve desired states is vital for efficient surface reactions, yet remains challenging due to the lack of well-defined precursor materials and weak metal-support interaction. Palladium-based catalysts, when not properly tailored for complete methane oxidation exhibit insufficient performance. Herein, we fabricate Pd oxide nano-clusters supported on SSZ-13 using atomic ions with strong metal-support interaction (SMSI). Steam treatment of Pd/SSZ-13 transforms Pd particles into ions and induces SMSI. Subsequently, CO reduction and O2 oxidation yield mildly sintered Pd oxide nano-clusters firmly anchored on extra-framework Alpenta sites of SSZ-13, facilitating superior activity. The robustness from SMSI prevents irreversible deactivation, and water-resistance by complete dehydration suppresses reversible degradation in wet conditions. This catalyst exhibits high performance in bench-scale reactions using monolith catalysts, ensuring applicability for industrial methane abatement. The results demonstrate that sequential treatment to Pd/SSZ-13 offers a promising approach for tailoring metal structures to enable high-performance methane oxidation.

Diverse Effects of SO2-Induced Pt-O-SO3 on the Catalytic Oxidation of C3H6 and C3H8.

The effects of sulfur dioxide (SO2) in the catalytic purification of short-chain hydrocarbons are still controversial, and the exact role of SO2 on adsorption and reaction pathways during the catalytic oxidation of different volatile organic compounds (VOCs) remains unclear. Herein, a three-dimensional ordered macroporous Ce0.8Zr0.2O2 supported Pt nanoparticle monolithic catalyst (Pt/OM CZO) was synthesized to investigate these effects. Our findings uncover the diverse effects of SO2: Upon SO2 treatment, the coupling between the S 3p and Pt 5d orbitals promotes the Pt-O-SO3 structure in situ formed on the catalyst surface. The propene (C3H6) molecule readily binds with the oxygen atom in Pt-O-SO3, resulting in the accumulation of acetone and carbon deposition, thereby hindering C3H6 oxidation. Conversely, a cleaved oxygen atom within the Pt-O-SO3 structure enhances propane (C3H8) adsorption and activates the C-H bond, facilitating C3H8 oxidation. These insights are pivotal for advancing the frontier of sulfur-tolerant catalysts, addressing both economic and environmental challenges.

Facile fabrication of NF-loaded Co3O4 monolithic catalyst and its application in the reduction of P-nitrophenol

In this work, a foam nickel-loaded Co3O4 nanosheet featuring an integral structure (NF@Co3O4) was successfully fabricated by a facile hydrothermal-calcination strategy. The catalytic performance of the NF@Co3O4 was evaluated using the reduction of P-nitrophenol (PNP) to P-aminophenol (PAP) under NaBH4 as a model reaction. A reduction rate of 94.44% for PNP was achieved under the following reaction parameters over 25 min at 25∘C: two slices of NF@Co3O4 monolithic catalysts (3 × 4 cm2), a PNP concentration of 15 mg L[Formula: see text] (500 mL), and a NaBH4 dosage of 15 mmol L[Formula: see text]. Moreover, NF@Co3O4 presented a stable performance in PNP reduction, maintaining a reductive conversion above 91% over sixteen consecutive runs. This study suggested that NF-loaded Co3O4 is a promising monolithic catalyst for the treatment of phenol-containing wastewater, owe to its superb catalytic performance and ease of recovery.