Search Results (31)

To comply with stringent emission regulations, the deployment of hybridized powertrains is continuously expanding. However, architectures such as plug-in and parallel hybrids intrinsically reduce the overall runtime of the internal combustion engine (ICE). Because the battery state-of-charge (SOC) dictates intermittent engine activation, this operational strategy inevitably induces frequent cold-start events. This study investigates the thermal dynamics of commercial catalyst geometries (300–1200 cpsi, 2–8 mil) via 1D numerical simulations under real-world driving conditions. Without active heating, high-thermal-mass substrates unexpectedly outperform ultra-thin-wall variants by buffering against convective quenching during prolonged idling. However, integrating start–stop functionality halts cold exhaust flow, elevating mean temperatures and marginalizing geometric disparities. Evaluating electrically heated catalysts (EHCs) reveals that discrete preheating is highly inefficient due to rapid heat dissipation. Conversely, continuous closed-loop heating coupled with start–stop functionality sustains operational temperatures for over 90% of the cycle. Under continuous heating, substrate geometry ceases to dictate thermal performance; instead, it governs electrical efficiency. Low-thermal-mass monoliths minimize cumulative energy demand to 213 kJ (versus 277 kJ for high-mass variants), incurring a negligible CO₂ penalty. Consequently, future hybrid architectures must integrate lightweight EHCs to ensure sustainable emission control. Full article

Conventional powdered catalysts for biomass valorization face critical operational limitations regarding recovery and reusability at an industrial scale. To address these challenges, this study developed innovative structured catalysts based on cordierite monoliths coated with carbon derived from oil palm waste, an abundant agricultural byproduct whose improper disposal poses environmental concerns. The carbonaceous layer was functionalized with sulfonic groups and tin (Sn) species to provide synergistic Brønsted and Lewis acid sites. In addition, colloidal silica was incorporated as a binder, significantly improving coating adhesion and homogeneity. Physicochemical characterization confirmed the successful incorporation of sulfonic groups and SnO_x species into the carbonaceous material, leading to dual Brønsted/Lewis acidity, with the B/L ratio increasing from 0.05 in AC to 0.07 in AC20p10Sn. Catalytic evaluation showed that the functionalized monoliths exhibited near 100% of glucose conversion with moderate selectivity towards 5-hydroxymethylfurfural (5-HMF). Notably, despite the surface deposition of solid byproducts, the monolithic architecture successfully eliminated complex downstream separation processes. Furthermore, the structured catalyst exhibited excellent stability, maintaining its catalytic performance over five consecutive cycles. This approach provides a sustainable pathway for structured carbon-coated monoliths derived from biomass waste while overcoming the handling bottlenecks of traditional powder systems by improving catalyst recovery, reusability, and scalability. Full article

Effective abatement of nitrogen oxides (NO_x) is achieved by ammonia selective catalytic reduction (NH₃-SCR). In this paper, the effects of single WO₃ doping and WO_x-VO_x co-doping into the MnO_x/TiO₂ catalyst on NH₃-SCR of NO_x removal, sulfur and water resistance, and reaction mechanisms were systematically investigated. The 5MnO_x/TiO₂, WO₃-5MnO_x/TiO₂, and WO₃-V₂O₅-5MnO_x/TiO₂ were prepared using the incipient-wetness impregnation method. Furthermore, the monolithic WO₃-V₂O₅-5MnO_x/TiO₂-CC (cordierite support) catalyst involved a coating process. The WO₃-V₂O₅-5MnO_x/TiO₂ catalyst demonstrated superior NO conversion and maintained over 80% activity following prolonged exposure to SO₂ and H₂O. Characterization results indicated that the introduction of WO₃ regulated Mn valence through the formation of W-O-Mn bonds. The synergistic effect of V₂O₅ and WO₃ further promoted electron transfer, increased surface chemisorbed oxygen and oxygen vacancies, and strengthened reactant adsorption and activation. In situ DRIFTS analysis suggested that WO₃ modulated the reaction pathway, and while 5MnO_x/TiO₂ followed the Langmuir–Hinshelwood (L-H) mechanism, both WO₃-5MnO_x/TiO₂ and WO₃-V₂O₅-5MnO_x/TiO₂ exhibited a combined L-H and Eley–Rideal (E-R) pathway. This study confirmed that WO₃ played a crucial regulatory role in both single-metal and multi-metal systems, and the synergistic interaction between V₂O₅ and WO₃ was the key to achieving superior denitration performance and poisoning resistance. Full article

Selective catalytic reduction (SCR) of NO using various reducing agents is a critical area of research for mitigating environmental pollution. In this study, the influence of active phase loading was investigated in four bimetallic Pt-Ag/Al₂O₃-WO_x catalysts, one monometallic Ag/Al₂O₃-WO_x catalyst, and one Pt-Ag/Al₂O₃-WO_x catalyst subjected to high-severity air-SO₂ pretreatment. All catalysts were supported on cordierite monoliths, and their performance in NO SCR was evaluated using H₂, C₃H₈, and CO as reducing agents. An increase in the active phase loading (Pt-Ag/Al₂O₃) from 10.7 wt% to 17.4 wt% resulted in higher conversions of NO, C₃H₈, and H₂, as well as improved N₂ selectivity. However, CO conversion decreased as the active phase loading increased, which was attributed to competitive reduction by H₂, since both reactions occur within the same temperature range (100–200 °C). The presence of N₂O below 6 ppm was observed in some catalysts. Furthermore, higher active phase loadings led to increased carbon deposition; the Ag/Al₂O₃-WO_x catalyst exhibited the highest carbon content (5 wt%). The deposited carbon was identified as ordered graphitic carbon. In the Pt-Ag catalysts, the presence of Ag⁺ and Agⁿδ⁺ species, as well as the Ag° plasmon, was identified by UV-Vis spectroscopy. STEM analysis showed Ag-Pt crystallites with an average size of 24 nm, which may have contributed to the higher NO conversion observed at 350 °C and the improved N₂ selectivity at 100 °C in the Pt-Ag bimetal catalysts, compared to the activity of the Ag/Al₂O₃-WOx catalyst. Full article

The development of highly efficient and stable non-noble metal catalysts for volatile organic compound (VOCs) abatement remains a pressing challenge. Mn-based perovskites exhibit superior thermal stability as redox catalysts but suffer from limited activity in light alkane combustion. This study systematically investigates the performance of SmMnO₃ (SMO) perovskite catalysts for propane oxidation through selective etching of Sm species. By precisely controlling the etching process, the removal of surface Sm exposes more active sites and significantly increases the specific surface area from 22.05 m²·g⁻¹ for pristine SMO to 66.15 m²·g⁻¹. SEM and N₂ adsorption–desorption analysis revealed that prolonged etching induces surface roughening and pore channel expansion. XPS and XANES measurements confirmed that an increased Mn⁴⁺/Mn³⁺ ratio enhances reactant adsorption and accessibility to active sites. The etched catalysts exhibited markedly improved activity for propane oxidation, achieving a ~50 °C reduction in light-off temperature compared to the raw SMO. This performance enhancement is attributed to the synergistic effects of enhanced oxygen mobility, elevated Mn⁴⁺ content, and abundant oxygen vacancies. Further characterization via Raman spectroscopy and H₂-TPR revealed weakened Jahn–Teller distortion and lower reduction temperatures, reflecting optimized Mn–O interactions and superior redox properties. Among the samples, SMO-20 demonstrated exceptional stability. Moreover, the SMO-20/cordierite monolithic catalyst maintained outstanding catalytic performance over 1000 h of operation. This work offers a facile and effective approach to engineer perovskite catalysts and provides new insights into structure–activity relationships in VOC oxidation. Full article

The aim of this work was the preparation of ceramic monolithic catalysts for the catalytic oxidation of gaseous mixture of benzene, toluene, ethylbenzene and o-xylene BTEX. The possibility of using zirconium dioxide (ZrO₂) as a filament for the fabrication of 3D-printed ceramic monolithic carriers was investigated using fused filament fabrication. A mixed manganese and iron oxide, MnFeO_x, was used as the catalytically active layer, which was applied to the monolithic substrate by wet impregnation. The approximate geometric surface area of the obtained carrier was determined to be 53.4 cm², while the mass of the applied catalytically active layer was 50.3 mg. The activity of the prepared monolithic catalysts for the oxidation of BTEX was tested at different temperatures and space times. The results obtained were compared with those obtained with commercial monolithic catalysts made of ceramic cordierite with different channel dimensions, and with monolithic catalysts prepared by stereolithography. In the last part of the work, a kinetic analysis and the modeling of the monolithic reactor were carried out, comparing the experimental results with the theoretical results obtained with the 1D pseudo-homogeneous and 1D heterogeneous models. Although both models could describe the investigated experimental system very well, the 1D heterogeneous model is preferable, as it takes into account the heterogeneity of the reaction system and therefore provides a more realistic description. Full article

The construction of multicomponent transition metal oxide catalysts can effectively increase the surface defects of catalysts, and bring a synergistic effect from different components, thus enhancing the generation of reactive oxygen species and improving the catalytic activity of catalysts for volatile organic compounds (VOCs) oxidation. In this article, CuO/Co₃O₄ catalysts with abundant oxygen vacancies for the degradation of ethyl acetate was prepared by a simple impregnation method. The effect of the ratio of Co/Cu on the redox capacity, oxygen vacancy, active oxygen species and catalytic oxidation activity of ethyl acetate were studied. The 90% conversion and mineralization temperatures of ethyl acetate for the optimal catalyst Co₃O₄-20Cu are 211 and 214 °C (WHSV = 60,000 mL/(g·h), 1000 ppm ethyl acetate), which also shows good stability and excellent water vapor resistance. Compared with pure Co₃O₄, the CuO/Co₃O₄ catalysts have more oxygen vacancies, provide more reactive oxygen species, allowing the catalyst better low-temperature reduction. Through in situ DRIFTS study, the intermediates of ethyl acetate decomposition were analyzed, then a possible catalytic oxidation mechanism of ethyl acetate on the Co₃O₄-20Cu catalyst was proposed. In addition, we prepared a Co₃O₄-20Cu/cordierite monolithic catalyst on the basis of Co₃O₄-20Cu, exhibiting a good catalytic activity in degradation of ethyl acetate. Full article

A high-activity, low-cost, and easy-to-prepare monolithic catalyst is crucial for the industrial catalytic combustion of volatile organic compounds (VOCs) in a cost-effective manner. In this study, a highly efficient monolithic catalyst, designated as 4GM/COR, was developed by loading 4% graphene-doped α-MnO₂ (4GM) catalyst onto pre-etched cordierite (COR) blocks using a straightforward “ball-milling-assisted impregnation” method. The anchoring force of the cordierite pores, generated through oxalic acid etching, enables the uniform and robust loading of powdered 4GM onto COR, preventing detachment under high temperatures or high gas flow rates. The loading rate, specific surface area, and concentrations of Mn³⁺ and surface-lattice and absorbed oxygen species in the monolithic catalyst increase with impregnation times from 2 to 4, indicating that catalytic activity is optimized through repeated impregnation. Catalytic performance tests demonstrated that the 4-4GM/COR exhibited the highest activity, achieving 90% degradation of toluene at 200 °C under both dry and humid (relative humidity is 85%) conditions. Furthermore, the 4-4GM/COR maintains high catalytic stability and activity even at a large GHSV of 6000 h⁻¹. To conclude, the 4-4GM/COR monolithic catalyst developed in this study not only represents a promising option for industrial applications but also serves as an important reference for the synthesis of monolithic catalysts. Full article

MnO₂ catalysts are recognized as highly efficient materials for ozone decomposition at room temperature. However, the conventional preparation methods, such as the hydrothermal method, typically require critical conditions (100–200 °C for 6–48 h). Moreover, the prepared catalysts are almost powders, which makes them difficult to apply as monolithic catalysts. In this work, a simple pH-adjusted method was developed to in situ prepare MnO₂ with different crystal phases (α, amorphous, and δ) under ambient conditions. XRD analysis revealed that decreasing the pH from 13 to 3 induced a gradual phase transformation from δ-MnO₂ to amorphous MnO₂, while the α-phase appeared at pH = 1.5. The combination of XPS and O₂-TPD results shows that amorphous MnO₂ exhibited the lowest average oxidation state (AOS) and highest oxygen vacancy concentration. The optimized amorphous MnO₂ catalyst (Cat. 2) achieved the highest ozone removal efficiency of 98% with a high relative humidity of 90%. Furthermore, in situ DRIFTS experiments further demonstrated that the prepared Cat. 2 maintained minimal OH accumulation under humid conditions, confirming its excellent water resistance. Finally, the preparation method of amorphous MnO₂ was effectively applied to cordierite honeycomb carrier (CHC). The a(amorphous)-MnO₂/CHC catalyst module (100 mm × 100 mm × 20 mm) showed stable ozone removal efficiency of 60% during a 60 h evaluation in an air duct (O₃: 400 ± 30 ppb, T: 25 ± 5 °C, gas velocity: 1 m s⁻¹). This study innovatively developed a simple pH-adjusted method to prepare MnO₂ with different crystal phases under ambient conditions and successfully applied it to the cordierite honeycomb carrier for monolithic catalyst development. Full article

The climate crisis, driven by increasing CO₂ levels in the atmosphere, has heightened the need for new, environmentally friendly energy sources. Hydrogen gas, which can meet our energy needs, has become a particularly intriguing topic. This study investigated the partial oxidation reaction of methane with cordierite monolith catalysts. The Ni-coated catalysts were supported with γ-Al₂O₃, CeO₂, ZrO₂, and CeO₂-ZrO₂. The catalysts were tested at temperatures of 750, 800, and 850 °C with different flow rates and methane feed concentrations (2%, 5%, and 10%). It was demonstrated that catalyst activity varies depending on these parameters. It has been found that high gas hourly space velocity (GHSV) and CH₄ feed rates decrease catalyst activity. The obtained reaction results indicated that the optimal reaction parameters were 800 °C, a GHSV of 1 × 10⁴ h⁻¹, and a CH₄ feed concentration of 2%. By optimizing these parameters, catalysts with high CH₄ conversion and selectivity for H₂ and CO were achieved. The prepared catalysts were characterized using scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and temperature-programmed reduction (TPR). Full article

The synthesis of Co and Ce oxide nanoparticles using precipitation of precursor salt solutions in the form of microdroplets generated with a nebulizer proved to be an efficient, fast and inexpensive method. Different morphologies of single oxides particles were obtained. Ceria nanoparticles were almost cube-shaped of 8 nm average size, forming 1.3–1.5 μm aggregates, whereas cobalt oxide appeared as rounded-edged particles of 37 nm average size, mainly forming nanorods 50–500 nm. Co₃O₄ and CeO₂ nanoparticles were used to generate structured catalysts from both metallic (stainless steel wire mesh monoliths) and ceramic (cordierite honeycombs) substrates. Ceria Nyacol was used as a binder to favor the anchoring of catalytic particles thus enhancing the adhesion of the coating. The resulting structured catalysts were tested for the combustion of diesel soot with the aim of being used in the regeneration of particulate filters (DPFs). The performance of these structured catalysts was similar to or even better than that exhibited by the catalysts prepared using commercial nanoparticles. Among the catalysts tested, the structured systems using ceramic substrates were more efficient, showing lower values of the maximum combustion rate temperatures (T_M = 410 °C). Full article

In this work, ceramic monoliths were coated with powders based on exchanged Cs and/or Co cations in Na-mordenite (MOR) zeolite. SEM images showed that zeolite particles fill the macropores of cordierite walls and form a continuous layer of approximately 40 µm with good adherence. XPS analysis revealed that Co and Cs are present on the film surface solely as Co²⁺ and Cs⁺ at exchange positions in zeolite. The monolithic structures were evaluated for the butane-toluene co-adsorption and SCR of NOx with hydrocarbon mixture as the reducing agent. The presence of alkali metal cations in the zeolitic lattice favored the adsorption capacity of both hydrocarbons, while cobalt cations provoked a decrease in the adsorbed amounts due to its weak interaction with the HCs. Breakthrough curves of butane adsorption showed a roll-up phenomenon, associated with a competitive adsorption effect generated from toluene presence. In the desorption process, it was observed that adsorbed toluene hindered the butane diffusion through mordenite channels, which released at higher temperatures (above 250 °C). Cs₂CoM and Cs₇CoM monoliths were more active than the CoM monolith for NO-SCR. The presence of Cs cations close to Co cations increased the hydrocarbons concentration around active sites at high temperatures, according to TPD results, promoting the reduction activity of NO. Full article

This study presents the development of a method for the washcoating of Ni/boehmite gels, prepared by the sol–gel process, onto the surface of a commercial ceramic monolith. Indeed, a cordierite monolith in a honeycomb shape was used as the substrate for the Ni/Al₂O₃ deposition. An experimental assembly was made in order to apply the coating on the cordierite surface. Different suspensions were used with various viscosities, and multiple coating parameters were tested as the withdrawal speed, or the number of impregnations. It was observed that the simple deposition of the Ni/boehmite gel led to the formation of coating. Different morphologies were observed, and defects were highlighted as cracks, coating-free areas or aggregates. Among the various parameters studied, the pH of the sol appeared to play a role even more important than the viscosity. Indeed, the sol acidified with nitric acid showed a coating which was almost free of cracks or of large aggregates. Moreover, the use of a slurry mix of calcined alumina particles and colloidal boehmite appeared also as an interesting path. The beneficial influence of the slurry was attributed to a better resistance of the coating against the stresses induced during drying, and a deviation of the cracks in the gels by slurry grains. Full article

Diesel engines are important for heavy-duty vehicles. However, particulate matter (PM) released from diesel exhaust should be eliminated. Nowadays, catalytic diesel particulate filters (CDPF) are recognized as a promising technology. In this work, a series of monolith Mn_1−nK_nCo₂O₄ catalysts were prepared by the simple citric acid method. The as-prepared catalysts displayed good catalytic performance for soot combustion and the Mn_0.7K_0.3Co₂O₄ catalyst gave the best catalytic performance among all the prepared samples. The T₁₀ and T_m of Mn_0.7K_0.3Co₂O₄-HC catalyst for soot combustion are 310 and 439 °C, respectively. The physical and chemical properties of catalysts were characterized by means of SEM, XPS, H₂-TPR, Raman and other techniques. The characterization results indicate that K substitution is favorable for the formation of oxygen vacancies, enhancing the mobility of active oxygen species, and improving the redox properties and so on. In-situ Raman results prove that the strength of Co-O bonds in the catalysts became weak during the reaction at high temperatures. In addition, SEM and ultrasonic test results show that the peeling rate of the coat-layer is less than 5%. The as-prepared catalysts can be taken as one kind of candidate catalyst for promising application in soot combustion because of its facile synthesis, low cost and high catalytic activity. Full article

Monolithic catalysts are widely used in industrial catalysis. However, in the preparation of a monolithic catalyst, the traditional methods have some drawbacks such as low washcoat uploading ratio and poor uniformity. In the present work, the effects of Pd/Ce loading and catalyst components on the catalytic abatement of toluene were investigated. The acid treatment of the substrate, the particle size of the slurry and the dispersant on the uniformity of the washcoat and the catalytic performance were also explored. Characterisation was achieved via BET, SEM, zeta potential and laser grain-size analyses. The results showed that the catalytic activity of the catalyst increased with the increasing of the Ce content. It was found that the 0.2Pd-0.3Ce/γ-Al₂O₃ catalysts had the best toluene catalytic activity. The pretreatment of the cordierite with 20% HCl could improve the properties of the cordierite. It was also found that reducing the particle size of the washcoat and adding dispersant PAA could effectively improve the stability of the suspension and the uniformity of the washcoat. When 20% HCl pretreatment was used, the toluene catalytic activity of the monolith catalyst prepared by cordierite increased, in which T₁₀ and T₉₀ decreased by about 5 °C. Decreasing the particle size and dispersant also promoted the efficiency of catalytic degradation. Full article