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Abstract: Manganese–zirconium catalysts loaded on ZSM-5 (Si/Al=25) were prepared using an ion-exchange method and investigated for the selective catalytic reduction of NO, with the aim of studying the effects of zirconium doping on the performance of Mn-based ZSM-5 catalysts. A series of characterization techniques, namely N2-sorption, X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), temperature-programmed reduction by hydrogen, and X-ray photoelectron spectroscopy (XPS), were used to characterize these samples. TEM and XRD results showed that the addition of zirconium increased the manganese dispersion and prevented manganese crystallization. XPS results demonstrated that the introduction of zirconium enhanced the manganese species enrichment on the ZSM-5 grain surfaces. After zirconium addition, some of the manganese ions were incorporated into the zirconia lattice. The strong interaction between Mn and Zr contributed to the formation of Zr3+ ions or oxygen vacancies around the Zr4+ ions, which enhanced the redox abilities of the Mn–Zr/ZSM-5 catalysts. The temperature range for efficient NO conversion was lowered after zirconium doping. The MnZr3/ZSM-5 (Mn 3.2wt.% and Zr 8.6wt.%) sample exhibited NO x conversions (>90%) over a wide temperature range (230–415°C) and markedly superior to that of Mn/ZSM-5 (296–425°C). Moreover, the formation of N2O was suppressed at low temperatures due to the presence of zirconium in the catalysts. [Copyright &y& Elsevier]

[Display omitted] • Utilizing Bacterial Cellulose as a Pore-Forming Agent to Synthesize Multi-Layered, Multi-Porous Composite Metal Oxide Catalysts. • Bacterial Cellulose Mitigates Environmental Risks and Cost in Catalyst Preparation. • In-Depth Analysis Reveals How the Pore Structure Created by Cellulose Pore-Forming Agent Enhances Catalytic Activity. Utilizing environmentally-friendly bacterial cellulose as a scaffold, a highly porous, layered OA-BC catalyst was synthesized through an enhanced sol-gel process. This catalyst demonstrated exceptional performance in the oxidation of toluene, outperforming conventional alternatives that utilize chemical porogens. The OA-BC catalyst efficiently degrades toluene at 220℃ with high stability and hydrophobicity, indicating resistance to deactivation. Its superior activity is due to increased oxygen vacancies, enhanced metal oxide cooperation, and a layered porous structure, which together enhance active oxygen species and oxygen diffusion. Calcination of the OA-BC catalyst results in molecular cleavage and formation of small aggregates, increasing hydroxyl groups that stabilize Cu and Ce centers, enhancing toluene-oxygen reactions. In-situ infrared and X-ray photoelectron spectroscopy confirm stable monodentate Cu+ ligands, contributing to its high catalytic activity. This study introduces a novel approach by employing bacterial cellulose as a template for synthesizing a porous stratified OA-BC catalyst, demonstrating superior performance in toluene oxidation. The efficacy of catalyst results from a tripartite synergy involving the stratified porous architecture, the stabilizing effect of Cu+-coordinating ligands and hydroxyl groups, and the interplay of hydroxyl electron donors and acceptors, shedding light on environmentally benign catalyst development. [ABSTRACT FROM AUTHOR]

[Display omitted] • The controllable morphology synthesis of hexagonal WO 3 (HWO) was achieved by commercial bacterial cellulose (C). • The obtained V 2 O 5 /HWO-C catalyst exhibits effective resistance to K poisoning and SO 2 , and follows the Langmuir-Hinshelwood mechanism. • The detailed alkali metal-resistant pathways for the distribution of alkali metal ions (K+) on the K-V 2 O 5 /HWO-C catalyst were proposed. A series of V 2 O 5 /HWO catalysts are prepared by hydrothermal and impregnation methods using different precursors, among which the V 2 O 5 /HWO-C catalyst exhibited the optimal NH 3 -SCR performance. Compared to oxalic acid (O) and water (W), commercial bacterial cellulose (C) as a precursor can firstly achieve a more controllable synthesis to form hexagonal WO 3 (HWO) of V 2 O 5 /HWO-C catalyst. Various characterization (XRD, N 2 -BET, TEM, SEM, XPS, EDX mapping, and NH 3 /NO-TPD-MS) indicate that a higher specific surface area, abundant active oxygen and surface acidity result from the V 2 O 5 /HWO-C catalyst. The reason is that HWO-C has an excellent and smooth rod-shaped morphology, which promotes high dispersion of V 2 O 5 on its surface. In situ IR results show that the SCR follows the Langmuir-Hinshelwood (L-H) mechanism, where absorbed NO x intermediate species are formed on the V 2 O 5 and react with the NH 4 + and NH 3abs groups of V 2 O 5 and HWO. After loading 1.75 wt% K+, the obtained K-V 2 O 5 /HWO-C catalyst exhibits effective resistance to K poisoning and SO 2 , and retains 78 % NO x conversion efficiency at 360 °C after 10 h, attributed to the effective capture of K+ (1.04 wt%) in HWO-C channels via a new pathway, although approximately 0.71 wt% K+ are located on HWO-C external surface with weak bonding to V 2 O 5. [ABSTRACT FROM AUTHOR]

• Ea of intermediate species is calculated during toluene oxidation. • Relationship between the activation energy of the overall and primitive reaction. • Transient response experiments of isotopically labeled oxygen. • M−K mechanism dominates in the oxidation of toluene. Catalytic properties of multiple metals deposited on TiO 2 nanoparticles were investigated in the oxidation of toluene. Isovolume impregnation method prepared the catalysts containing Cu, Mn, Ni, Co, and Fe deposited on TiO 2 , including CeO 2 and ZrO 2. The effects of loaded metal oxides on the structure and activity of initial catalysts were investigated using various characterization techniques. Toluene's removal efficiency and CO 2 selectivity in the catalyst system were classified as follows: CuCeZr/T > MnCeZr/T > NiCeZr/T > CoCeZr/T > FeCeZr/T. Presence of water vapor exhibits an inhibitory effect on the conversion of toluene, which diminishes at higher temperatures. One contribution of this paper is to obtain the oxidation pathway of toluene and the relationship between the activation energy of all-inclusive and elementary reactions based on the variation of infrared spectrum using Freeman-Carroll method. Another contribution is to clarify the share of Langmuir-Hinshelwood and Mars-van Krevelen mechanisms during the oxidation of toluene over CuCeZr/T catalyst by transient response experiments of isotopically labeled oxygen. These findings provide a feasible method for the design and synthesis of transition metal oxide catalysts for industrial applications. [ABSTRACT FROM AUTHOR]

• Semi-quantitative analysis of 23Na CP/MAS NMR were conducted. • Molecular occurrence model of sodium was constructed via computational chemistry. • Adsorption position of sodium was investigated by computational chemistry. • The real way of organic sodium bonding to the coal was discussed and observed. Detailed intrinsic sodium occurrence for future research on migration, release, and catalyst effect behavior of sodium is necessary. Complementary characterizations, such as 13C CP/MAS NMR, FT-IR, 23Na CP/MAS NMR, XPS, elemental composition analysis, and sequential extraction experiments, were employed to elucidate the actual compound form of sodium as well as Zhundong coal's structural features. Thus, a molecular occurrence model of sodium in Zhundong coal was constructed based on its structural characteristics via computational chemistry. The occurrence model of alkali metals in Zhundong coal, including their compound form, relative content, and distribution properties, was investigated at the microstructural level. Preliminary results show that the amorphous cell formula of Zhundong coal is (C 2080 H 980 O 380 N 30 S 10 Na) n. Organic oxygen in Zhundong coal was 67.7% hydroxyl (ethoxy), 15.5% carbonyl, and the remaining 16.8% was attributed to carboxyl. Combined with the 23Na CP/MAS NMR and sequential extraction experiment, organic sodium accounts for 18.01% of the total. Most inorganic sodium (81.99%) is present as hydrated sodium ion (75.08%), while a small part is present as NaCl crystal phase (3.34%) insoluble-sodium account for 3.57%. Calculated 13C NMR, FT-IR, and 23Na NMR spectra of the proposed model agree well with the experimental spectra suggesting that the molecular occurrence model of sodium in Zhundong coal is a particularly convincing model at the approximate condition of statistical average. The highest negative electrostatic potential area is near the carboxyl group and may be attributed to organic sodium absorption sites; the hydroxy or phenoxy group nearby may form additional coordination bonds to sodium, indicating the reflection of the complexity of the Na chemical environment as concluded from 23Na CP/MAS NMR. [ABSTRACT FROM AUTHOR]

• The LMO-W, LMO-SW, LCMO-W, LCMO-SW, LSMO-W and LSMO-SW catalysts were well designed by precursors. • The Binary search was used to determine the lean-combustion limits for the self-sustained combustion of CO. • The stability of the LCMO-SW catalyst was evaluated under CO oxidation at the furnace temperature of 535 °C. • The influence mechanism of self-sustaining combustion stability of CO catalyst was investigated and put forward. • The L-H mechanisms were performed for SCR reaction over the catalysts via in situ IR experiments. The LaMnO 3 , La 0.9 Ce 0.1 MnO 3 and La 0.9 Sr 0.1 MnO 3 catalysts are synthesized using sugar agent, and the CO self-sustained combustion is investigated, where the catalytic performance is decided by temperature with CO conversions of 10% (T 10), 50% (T 50), and 90% (T 90). The results show that self-sustaining combustion is successfully realized on the catalyst, and the order of activity decrease is as follows: La 0.9 Ce 0.1 MnO 3 (with sugar) > La 0.9 Sr 0.1 MnO 3 (with sugar) > LaMnO 3 (with sugar) > LaMnO 3 (without sugar) > La 0.9 Sr 0.1 MnO 3 (without sugar) > La 0.9 Ce 0.1 MnO 3 (without sugar). Combined with the results of XPS, H 2 -TPR, O 2 -TPD and CO-TPD techniques, the excellent activity of La 0.9 Ce 0.1 MnO 3 (with sugar) can be attributed to the high content of Mn4+ ions and reactive oxygen vacancies enriched on the catalyst surface, sound low-temperature reduction, and uniform dispersion. Besides, in situ IR spectroscopy results indicate that the catalytic combustion of CO over manganese-based perovskite catalysts follows the L-H mechanism: the chemisorption of CO and O 2 takes place to produce monodentate carbonates and bicarbonate species, which then decompose to yield CO 2 release. The high-temperature stability test provides evidence that the La 0.9 Ce 0.1 MnO 3 (with sugar) gives 100% CO conversion and that the activities remain almost unchanged after reaction for 12 h, where the temperature of catalyst bed reaches about 717 °C. The results obtained are helpful to accept this technology on efficient and clean energy utilization in iron and steel industry. [ABSTRACT FROM AUTHOR]

The reaction pathways of CO oxidation over the (1 0 0), (1 1 0) and (1 1 1) crystal planes of Cu 2 O. • Morphologies of Cu 2 O micro/nanocrystals were controlled by simply changing precursor concentration. • Increase of precursor concentration results in more exposure of active crystal plane of Cu 2 O. • Activity of CO self-sustained catalytic combustion on Cu 2 O increases with precursor concentration. • Coordination unsaturated Cu and O on the (1 1 1) and (1 1 0) planes promote CO oxidation. The self-sustained catalytic combustion is one of the most effective ways to remove high concentration CO at low temperature. In this paper, Cu 2 O micro/nanocrystals with different morphologies were successfully synthesized by changing the precursor concentration using liquid phase reduction method. The obtained Cu 2 O were characterized using SEM, XRD, XPS, H 2 -TPR and O 2 -TPD, and the relationship between the catalytic performance and morphology was analyzed based on CO-TPD-MS and activity evaluation results. It was found that high precursor concentration leads to more exposure of active crystal planes of Cu 2 O. Compared with Cu 2 O-1 exposing only (1 0 0) crystal planes, Cu 2 O-5, the precursor concentration of which is 5 times of Cu 2 O-1, exposes (1 0 0) and (1 1 0) crystal planes. Cu 2 O-9, with 9 times of precursor concentration of Cu 2 O-1, exposes (1 0 0), (1 1 0) and (1 1 1) crystal planes simultaneously. All the obtained Cu 2 O with different precursor concentrations can achieve self-sustained CO catalytic combustion, and the catalytic activity increases with increasing precursor concentration (Cu 2 O-1 < Cu 2 O-5 < Cu 2 O-9). The results prove that unsaturated coordination of Cu and O on the (1 1 1) and (1 1 0) planes can enhance the corresponding reducibility, adsorption and activation of gaseous oxygen, consequently promoting the CO oxidation to CO 2 over Cu 2 O-9. [ABSTRACT FROM AUTHOR]

• The powder sample is well designed and coated on the HC tube to form CuCe 0.75 Zr 0.25 O δ /HC catalyst. • The transient changes and two-dimensional temperature region are obtained for CO self-combustion via CO-TPO + FLIR. • The various intermediate species and competitive adsorption of reactants on different active sites are evidenced. • The different pathways and roles of M-K and L-H mechanisms are proposed using in situ IR. A CuCe 0.75 Zr 0.25 O δ catalyst was prepared by the sol-gel method and successfully coated on honeycomb ceramic (HC) carrier. The activity of CuCe 0.75 Zr 0.25 O δ /HC was determined by the CO-TPO + FLIR, with the results performing that the critical condition for CO self-sustained combustion is 3 vol% CO + 3 vol% O 2 /N 2 at 0.5 L/min. As the CO concentration increases from 1 vol% CO to 3 vol% CO, the induction process (T 15) shifts to rapid ignition with a transient change for the CO oxidation reaction. The furnace temperature for CO self-sustained combustion decreases with increasing the CO and O 2 concentrations. Upon increasing the CO 2 concentration, however, furnace temperature is needed to increase and realize CO complete conversion. The thermal stability test combined with SEM + EDX results indicate that the CuCe 0.75 Zr 0.25 O δ /HC retains an excellent thermal stability after a 200 h, and the high-temperature region remains at 225 ± 1 °C during the CO self-combustion reaction. The activity of catalyst is reduced slightly after the 200 h test because of the carbon deposition on the catalyst surface, but such a slight deactivation can be eliminated by the air oxidation method. In situ IR results show a competitive adsorption of CO/O 2 and CO 2 on the Cu-Ce active sites, indicating that the addition of gaseous CO 2 performs an inhibition of CO oxidation. CO preferentially adsorbs linearly at Cu+ sites to form carbonyls that react with lattice oxygen to produce CO 2 to release, which can be ascribed to M-K mechanism. The L-H mechanism is less important, which involves the relatively weak reaction of adsorbed CO and adsorbed oxygen on the Cu-Ce active sites to form carbonate species. [ABSTRACT FROM AUTHOR]