Explore the vast range of titles available.

Abstract 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 Co x /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.

Ce-based catalysts have been widely used in the removal of nitrogen oxides from industrial flue gas because of their good catalytic performance and environmental friendliness. However, the mechanism of alkali metal poisoning in Ce-based catalysts remains to be further studied. This work involves the preparation of the K/Na-poisoned CeWTi catalyst via the impregnation method for assessing its performance in NO removal. Experiments show that both K and Na exhibit detrimental effects on the CeWTi catalyst, and the loading of alkali metal reduces the specific surface area and pore volume of the catalyst. Furthermore, the presence of alkaline metals results in a notable decline in the CeWTi acid concentration, particularly in Lewis acid sites. Concurrently, the levels of Ce3+, oxygen vacancies, and reducing agents on the catalyst surface decrease, leading to diminished reduction capability and eventual catalyst deactivation. The application of a BP neural network for catalyst activity prediction yielded an average relative error of approximately 0.73%, indicating enhanced accuracy in prediction outcomes. This work explored the cause of alkali metal poisoning of the CeWTi catalyst and provided an effective prediction method for the lifetime of CeWTi catalyst, which provided theoretical guidance for the engineering application of Ce-based catalysts.

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 Co 6 ) on the surface of CeO 2 (110) using density functional theory, from which a stable loaded Co/CeO 2 (110) structure was selected to investigate the methane activation mechanism. Despite the relatively small size of the selected Co clusters, the obtained Co x /CeO 2 (110) exhibits interesting properties. The optimized Co 5 /CeO 2 (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 CH 3 *, CH 2 *, 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 CeO 2 (110) surface contributes to the understanding of the essence of Co/CeO 2 catalysts with promising catalytic behavior. It provides theoretical guidance for better designing the optimal Co/CeO 2 catalyst for tailored catalytic reactions.

With the increasing emphasis on environmental protection and sustainable development, improving air pollution control technology has become imperative. In this study, Ce-based catalysts are used as research objects to explore the effects of hydrothermal aging on their performance in oxidizing PM. Different Mn, Na, Pt and Zr-doped Ce-based catalysts were prepared based on the impregnation method and the PM oxidation performance of Ce-based catalysts before and after hydrothermal aging was investigated using thermogravimetric experiments, and the catalytic activity change pattern of fresh/hydrothermal aging Ce-based catalysts was analyzed by comparing the comprehensive combustion index S and combustion stability index Rw, revealing the PM oxidation process. The conclusion showed that the cerium-based catalyst significantly enhanced the oxidation efficiency of PM compared with PU. By comparing the performance of different metal-modified catalysts, it was found that the order of activity was: Pt > Na > Mn > Zr. With the metal doping increased, only the comprehensive combustion index S and combustion stability index Rw of Na/CeO2 catalysts decreased. After hydrothermal aging treatment, the Zr/CeO2 catalysts showed the best hydrothermal aging resistance, and the comprehensive combustion index S and combustion stability index Rw remained stable (<5%). Ce-based catalysts have the strongest to weakest hydrothermal aging resistance in the following order: Zr > Mn > Pt > Na. This study not only provides an important scientific reference for the application of Ce-based catalysts in the field of environmental purification but also contributes new ideas and methods to promote the green and sustainable development of air pollution control technology.

The demand for environmentally friendly types of energy is growing all over the world, which naturally increases the intensity of studies on fuel mixtures that have high contents of hydrogen. In this case, methanol steam reforming is a leading effective research area, as it is a process with low energy consumption. The results of the steam reforming of methanol on synthesized catalysts by the solution combustion synthesis (SCS), self-propagating high-temperature synthesis (SHS), and moisture impregnation capacity methods are presented. A study was conducted to evaluate the activity of Cu-Ce-Al catalysts with varying ratios of components for hydrogen production, comparing the SCS method with the other mentioned methods. The methanol conversion reached 99% and the selectivity of H2 was 88% at 500 °C. The study showed that the replacement of Al3+ ions with Cu2+ and Ce3+ cations leads to the formation of spinels, such as CuAl2O4 and CeAlO3. As a consequence, the CuAl2O4 and CeAlO3 lattice parameters increase because of the difference in the ionic radii of Al3+ (0.53 Å), Cu2+ (0.73 Å), and Ce3+ (1.07 Å). Advantages of SCS catalysts in the process of the steam reforming of methanol have been demonstrated. The goal of this research is to create a new catalyst for methanol’s conversion into hydrogen-containing fuel mixtures, the production of which, in the future, will be a huge step in the transition to more energy-efficient and environmentally friendly methods of their synthesis.

The simultaneous removal of NO x and dioxins is the frontier of environmental catalysis, which is still in the initial stage and poses several challenges. In this study, a series of CeNb 3 Fe x /TiO 2 ( x  = 0, 0.3, 0.6, and 1.0) catalysts were prepared by the sol–gel method and examined for the synergistic removal of NO x and CB. The CeNb 3 Fe 0.3 /TiO 2 catalyst exhibits an optimum catalytic performance, with an NO x conversion greater than 95% at 260–380 °C. It also exhibits an optimal CB oxidation activity, in which CB promoted both the NO x conversion and N 2 selectivity below 250 °C. Moreover, the more favorable ratios of Ce 4+ to Ce 3+ and plentiful surface-adsorbed oxygen species are the reasons why CeNb 3 Fe 0.3 /TiO 2 catalyst has better catalytic activity than other catalysts at the lower temperature. Simultaneously, owing to the modulation of Fe to the redox properties of Ce and Nb, the large number of oxygen vacancies and acid sites was generated, and the CeNb 3 Fe 0.3 /TiO 2 catalyst is beneficial to NO x reduction and CB oxidation. Furthermore, the results of in situ DRIFTS study reveal the NH 3 -SCR reactions over CeNb 3 Fe 0.3 /TiO 2 catalysts are mainly conformed to by the L–H mechanism (< 350 °C) and E-R mechanism (> 350 °C), respectively, and the multi-pollutant conversion mechanism in the synergistic reaction was systematically studied.

In this study, Mn-Ce/Al2O3/TiO2 catalyst prepared by impregnation method was used for synergistic O3 oxidation NO. The catalyst prepared by impregnating Al2O3/TiO2 at a Mn:Ce molar ratio of 4:1 showed the best catalytic activity. The catalyst performance showed that when the molar ratio of Mn:Ce was 4:1 and the volume ratio of O3:NO was 1:4, the removal rate of NO could reach 63%, which could increase the removal rate by 40% compared with that of NO oxidized by O3 alone. BET, XRD, and TEM characterization results showed that when the molar ratio of Mn:Ce was 4:1, the catalyst specific surface area, and pore capacity were the largest. A large amount of MnOx and CeOx were distributed on the catalyst surface. The XPS analysis showed that the oxidation-reduction and oxygen vacancy of Mn (IV)/Mn (III)/Mn (II) and Ce (IV)/Ce (III), had a synergistic effect on the decomposition of O3 into reactive oxygen species(O*), thus improving the catalytic capacity of Mn-Ce/Al2O3/TiO2 catalyst for O3. The O2-TPD analysis showed that the oxygen vacancies and oxygen species in the catalyst could be used as the active point of decomposition of O3 into O*. The experimental results show that the prepared catalyst can significantly improve the efficiency of ozone oxidation of NO and reduce the amount of ozone. The catalyst can be applied to ozone oxidation denitrification technology.

In this study, CeZr0.5TiaOx (with a = 0, 1, 2, 5, 10) catalysts were prepared by a stepwise precipitation approach for the selective catalytic reduction of NOx with NH3. When Ti was added, all of the Ce-Zr-Ti oxide catalysts showed much better catalytic performances than the CeZr0.5Ox. Particularly, the CeZr0.5Ti2Ox catalyst showed excellent activity for broad temperature range under high space velocity condition. Through the control of pH value and precipitation time during preparation, the function of the CeZr0.5Ti2Ox catalyst could be controlled and the structure with highly dispersed CeO2 (with redox functions) on the surface of ZrO2-TiO2 (with acidic functions) could be obtained. Characterizations revealed that the superior catalytic performance of the catalyst is associated with its outstanding redox properties and adsorption/activation functions for the reactants.

The efficient removal of refractory organosulfur compounds, such as dibenzothiophene, remains a critical bottleneck in achieving ultra-low sulfur diesel standards. While oxidative-adsorptive desulfurization is promising, there is a significant research gap in rationally designing adsorbents that utilize synergistic multi-metal active sites to enhance the capture of sterically hindered species. To address this, we synthesized a novel multi-metal ion-exchanged zeolite (AgNiCeY) via a sequential ion-exchange process, aiming to strategically incorporate Lewis acid sites (Ag + , Ni 2+ , Ce 3+ ) within the NaY framework. BET surface area for NaY and AgNiCeY was 623 and 540 respectively .The desulfurization performance and underlying adsorption mechanisms were rigorously evaluated. Using response surface methodology (RSM) on a model fuel system (DBT in n -octane)), the optimal capacity was determined at a contact time of 55 min and an oil/adsorbent ratio of 18.2 ml/g. The resulting AgNiCeY adsorbent demonstrated a remarkable increase in equilibrium adsorption capacity from 12.61 mg/g (NaY) to 33.26 mg/g, marking a 164% enhancement. Mechanistic analysis, supported by FT-IR and electronic structure visualization, confirms that the synergy between the exchanged cations acts as Lewis acids, facilitating superior σ\\sigmaσ-bond formation with the sulfur atom. Crucially, when tested under realistic conditions using real diesel fuel containing 2544 ppm sulfur, the modified AgNiCeY maintained high efficiency, achieving a 61.3% sulfur removal, significantly outperforming the parent NaY (57.8%). This study validates a novel design principle for heterogeneous catalysts, demonstrating that precise, sequential multi-metal exchange in zeolites offers a robust and scalable strategy for improving the selective adsorption of refractory sulfur compounds. Regeneration experiments were also conducted to assess the recyclability of the catalysts over multiple cycles.

Progressive research on reducing engine emissions is highly valued due to the emissions’ significant environmental and health impacts. This comprehensive comparative study examines the catalytic efficiency of manganese (Mn) and cerium silica (Ce-Si) synthesis catalyst-based molds in a diesel engine using a selective catalytic reduction (SCR) technique with diesel and diesel–plastic oil blend (DPB) (B50). In addition to Fourier transform infrared spectroscopy (FTIR) studies, X-ray diffraction (XRD), scanning electron microscopy (SEM), and the Brunauer–Emmett–Teller (BET) method are utilized to characterize the produced molds before and after exhaust gas passes. The Ce-Si-based mold demonstrates superior redox capacity, better adsorption capacity, and better thermal stability, attributed to enhanced oxygen storage and structural integrity compared to the Mn-based mold. Under minimum load conditions, nitrogen oxide (NO) reduction efficiency peaks at 80.70% for the Ce-Si-based mold in the SCR treatment with DPB fuel. Additionally, significant reductions of 86.84%, 65.75%, and 88.88% in hydrocarbon (HC), carbon monoxide (CO), and smoke emissions, respectively, are achieved in the SCR treatment under optimized conditions. Despite a wide temperature range, Ce-Si-based mold promotes high surface area and superior gas diffusion properties. Overall, the Ce-Si-based mold provides efficient emission control in diesel engines, which paves a path for developing better environmental sustainability. The outcomes contribute to advancing environmental sustainability by supporting the achievement of SDGs 7, 11, and 13.