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Manganese-based mullite-type and perovskite-type mixed oxides were prepared by sol–gel method, and then palladium was loaded onto the mixed oxides by wet impregnation method. The catalytic performance for methane combustion, the influence of the supports, and the interaction between noble metal and the mixed oxides were investigated via experiments and theoretical calculations. The Pd/SmMn2O5 catalyst exhibited superior low-temperature catalytic activity for methane combustion (T50 = 328 °C), which was superior to the Pd/perovskites catalysts and even better than Pd/Al2O3 catalyst. It was ascribed to the abundant labile surface lattice oxygen species with high mobility and the uniformly dispersed Pd species on SmMn2O5, as revealed by TEM, CO-chemisorption, H2-TPR and XPS. DFT calculations verified the significant metal-support interaction via electron transfer between Pd and SmMn2O5, which further activated the lattice oxygen and improved the catalytic performance. It demonstrates the prospect of utilizing SmMn2O5 mullite to optimize the typical noble metal catalysts. [ABSTRACT FROM AUTHOR]

• Pr-modified MnO x catalysts were prepared via co-precipitation method. • Pr modification promoted low-temperature catalytic performance and SO 2 resistance. • A highly dispersion of metal oxides could be achieved by Pr modification on MnO x catalysts. • Lewis acid sites and chemisorbed oxygen were enriched on the surface of MnPrO x catalysts. Manganese oxides (MnO x) are a promising catalyst in selective catalytic reduction of NO with NH 3 due to their excellent low-temperature catalytic activities. However, MnO x still suffer from poor N 2 selectivity and SO 2 resistance. In this work, rare earth element Pr was used to modify MnO x catalysts via co-precipitation method, and the effects of Pr modification on SCR performance of MnO x catalysts had been investigated. The temperature window of MnPrO x -0.1 catalyst with nearly 100% NO conversion efficiency ranged from 120 to 220 °C, and Pr modification on MnO x catalyst had improved the resistance to SO 2 obviously. The characterization results indicated that Pr modification on MnO x catalyst could increase the specific surface area, dispersity, reducibility, relative percentages of surface Mn4+ and chemisorbed oxygen species (O α). NH 3 -TPD and in-situ DRIFTS results revealed that Pr modification increased the adsorption of NH 3 on catalyst surface, resulting in more amount of Lewis acid sites on the surface of MnPrO x -0.1 catalyst. All of these factors led to an excellent catalytic performance of Pr-modified MnO x catalysts. In-situ DRIFTS results implied that SCR reactions over Pr-modified MnO x catalyst followed both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. [Display omitted] [ABSTRACT FROM AUTHOR]

Cu-SAPO-34 catalysts with varied Cu loadings were synthesized through ion exchange to study the influence of water on the NH3-SCR reaction. The catalytic activities were evaluated by selective catalytic reduction of NO under a reactant feed in the presence/absence of water. Transient experiments were designed to study the response of NO conversion to the presence of water. H2-TPR and DFT calculations were performed to study the reducibility of Cu species. NH3-TPD and XPS were conducted to reveal the migration of Cu species. The results show that water could remarkably improve NO reduction activities and the promoting effect is more significant on the catalyst with low Cu loading. Both transient and permanent influences were found in this promoting phenomenon. For the transient influence, water has been proved to accelerate the re-oxidation half-cycle. Moreover, water can enhance the promoting effect of the SCR feed on the migration of Cu species. These unanchored Cu ions migrate to defect sites to form active sites, which lead to a permanent influence of water. [ABSTRACT FROM AUTHOR]

In this work, an active nano-catalyst with gold nanoparticles loaded in hollow mesoporous silica nanospheres (HMSNs/Au) was prepared by a one-pot sol-gel method, in which gold ions were loaded in hollow mesoporous silica spheres followed by sodium alginate reduction. The characterization of the HMSNs/Au were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N2adsorption–desorption isotherms (BET). The high catalytic activity of HMSNs/Au, denoted as apparent turn-over frequency (TOF), was detected by UV-Vis spectrophotometer for the catalytic reduction of 4-nitrophenol (74.5 h−1) and 2-nitrophenol (108.7 h−1) in the presence of sodium borohydride solution due to the small gold nanoparticles size and overall exposure of active sites. It is expected that this ecofriendly approach to prepare inorganic composited nanoparticles as high active catalysts based on hollow mesoporous materials was a promising platform for loading noble metal nanoparticles. [ABSTRACT FROM PUBLISHER]

Alkali metals are poisonous to the metal oxide catalyst for NO removal. The chemical configuration of alkali containing substance and interacting temperature can affect the poisoning profile. A computational method based on Frontier Molecular Orbital analysis was proposed to determine the reacting behavior of various alkali-containing substances with SCR catalyst. The results reveal that the poisoning reactivities of various substances can be ranked as: E (MOH) > E (M 2 SO 4 ) > E(MCl) > E(MNO 3 ) > E(MHSO 4 ). The experimental activity tests of the catalysts calcined at stepped temperatures show that NaOH can react with the catalyst below 200 °C. NaCl and NaNO 3 start to react with the catalyst at a temperature between 300 and 400 °C. Unlike MOH, MCl and MNO 3 , which can produce volatile or decomposable species for the anions after reacting with the catalyst, M 2 SO 4 and MHSO 4 will leave both cations and anions on the catalyst surface. The sulfate ions left on the catalyst can generate active acid sites for NH 3 adsorption. The experimental results also show that Na 2 SO 4 and NaHSO 4 will not lower the NO conversion. The after-reaction influences of various alkali metals were studied using theoretical and experimental methods. The theoretical results show that the acidity decreases with doping of alkali metal. Experiments show a consistent result that the NO conversion decreases as undoped >LiCl > NaCl > KCl. [ABSTRACT FROM AUTHOR]

A one-step ion-exchange method is developed to prepare high-performance Cu-SSZ-13 from Na-SSZ-13, by adjusting pH values of Cu salt solution during Cu-exchange. The H+ concentration has a significant influence on the Cu loading and distribution. In the absence of H+, the Cu2+ can only exchange the Na+ in 8 member rings (8-MR) as Cu(OH)+, due to the steric hindrance of Na+ ions located in 6 member rings (6-MR). When H+ is present, it is found to compete with Cu2+ to exchange the Na+ and to occupy the exchange sites in Na-SSZ-13. The Cu2+ ions take a priority over H+ to occupy the neighboring Al sites in 6-MR, while H+ takes precedence over Cu2+ to occupy ion-exchange sites in 8-MR, causing that Cu2+ coordinated to 6-MR is dominant in Cu-SSZ-13 via one-step method. The H+ concentration affects the overall catalytic activity and hydrothermal stability by controlling the Cu2+ loading and distribution. [Display omitted] • High-performance Cu-SSZ-13 is prepared via one-step ion-exchange from Na-SSZ-13. • The H+ competes with Cu2+ ions to exchange the Na+ ions in Na-SSZ-13 during Cu-exchange. • The chemistry of the competition between H+ and Cu2+ ions are revealed. • The H+ concentration affects the Cu2+ loading and distribution in Cu-SSZ-13. • The H+ concentration determines the activity and HTA stability of prepared catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two carbonates of Na 2 CO 3 and (NH 4) 2 CO 3 are used for SrO-based catalyst synthesis. • SrO-M/Na exhibits a better catalytic activity in comparison to SrO-M/NH 4. • SrO-M/NH 4 shows a better reusability by contrast to SrO-M/Na. • The existence of Na enhances the amount of lattice oxygen for SrO-M/Na. In present study, sodium carbonate (Na 2 CO 3) and ammonium carbonate ((NH 4) 2 CO 3) are separately selected as precipitant to synthesize the strontium oxide (SrO) based solid catalyst, namely, SrO–M/Na and SrO–M/NH 4 for biodiesel production through transesterification. The influence of precipitant on catalyst physicochemical property, catalytic activity as well as reusability are investigated and compared. To begin with, transesterification parameters of catalyst amount, molar ratio of methanol to oil, reaction time, and reaction temperature are concerned to comprehensively evaluate catalytic performance of the two catalysts. Moreover, catalyst reusability is evaluated under the optimal conditions. With catalyst amount of 4 wt.%, molar ratio of methanol to oil of 9 at 65 ℃ within 30 min, SrO–M/Na exhibits a better catalytic activity in comparison to SrO–M/NH 4 , whereas, the reusability is in reverse sequence. In order to reveal the reason behind, catalysts are characterized by thermogravimetric/differential thermogravimetric/scanning calorimetry (TG/DTG/DSC), X–ray diffraction (XRD), X–ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), N 2 –adsorption/desorption, basic strength, basicity and vibrating sample magnetometer (VSM). [ABSTRACT FROM AUTHOR]

• A brand new, efficient, and practically accessible method to regulate reducibility. • After tuning, we highly accelerated redox circles in catalytic oxidation reaction. • Occupying cations created "pushing" effect towards A-sites Co2+ and B-sites Co3+. • Adsorbed oxygen and surface defects were enriched due to the lattice distortion. Promoting the catalyst reducibility is the key to the breakthrough of the catalytic oxidation technology. We prepared the layered double oxides (LDOs) spinel catalysts utilizing the layered double hydroxides (LDHs) as precursors. Innovatively, cobalt was applied as A/B-sites double-occupying cations. By introducing Cu(II) into the A-sites, we created a pushing effect towards the A-sites Co(II). The binding energy of Co 2p and the projected density of states energy of Co 3d shifted higher. The Co(II) gained greater momentum to convert to Co(III). The same pushing effect towards B-sites Co(III) were generated using B-sites occupying Ga(III), promoting Co(III) transfer towards lower valence state. Thus, the converting between Co(II) and Co(III) were speeded up. Moreover, the ionic radius differences between Cu(II) and Co(II) caused lattice distortion, enhancing the adsorbed oxygen species and surface oxygen defects. These contributed to the great improvement of reducibility and enhanced catalytic activity towards toluene oxidation. [ABSTRACT FROM AUTHOR]

Formation of NH 4 HSO 4 and its deposition on catalyst surface are the main obstacle for the application of NH 3 -SCR technology at low temperature. In this work, the deposited NH 4 HSO 4 was found to be highly active towards NO x in the NO/NO 2 contained atmosphere on the V 2 O 5 -WO 3 /TiO 2 catalyst. The reaction profiles indicate that the NO/NO 2 /O 2 mixture can rapidly react with NH 4 + of NH 4 HSO 4 above 100 °C, while NO/O 2 mixture can only strongly react with NH 4 HSO 4 above 300 °C. Regenerations of NH 4 HSO 4 -deactivated catalyst were performed in both NO/O 2 and NO/NO 2 /O 2 atmospheres and the performances were compared. Results from FTIR, XPS and EDS characterizations indicate the S-containing groups of deposited NH 4 HSO 4 will be stabilized as metal sulfate after NH 4 + is consumed by NO x . The BET and BJH analysis shows that the NO/NO 2 /O 2 mixture can recover the pore structure of NH 4 HSO 4 -deposited catalyst more effectively than NO/O 2 mixture does. The SCR activity tests reveal that the regeneration by NO/NO 2 /O 2 mixture can remarkably restore the activity of NH 4 HSO 4 -deactivated catalyst. [ABSTRACT FROM AUTHOR]

One kind of composites involved in silver nanoparticles (AgNPs) loading in-situ on natural populus fiber (PF) matrix was prepared by polyamidoxime (PAO) functionalized the cellulose fiber. In which PAO worked as trapping and stabilizing agents chelating silver ions and made it reduced in-situ to obtain AgNPs by borohydride at room temperature. The synthesized composites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Moreover, the composites showed significant catalytic activity 1.87 s −1 g −1 and repeated usability more than 7 cycles in reducing 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) detected by UV–vis spectrophotometer in aqueous solution due to the surface-enhanced immobility and large amount of AgNPs. The natural cellulose fiber provides a green platform to react and support other noble metals for wide catalytic reactions. [ABSTRACT FROM AUTHOR]