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Surface property modification of catalyst support is a straightforward approach to optimize the performance of supported noble metal catalysts. In particular, oxygen vacancies and hydroxyl groups play significant roles in promoting noble metal dispersion on catalysts as well as catalytic stability. In this study, we developed a nanoflower-like TiO2-supported Pd catalyst that has a higher concentration of oxygen vacancies and surface hydroxyl groups compared to that of commercial anatase and P25 support. Notably, due to the distinctive structure of the nanoflower-like TiO2, our catalyst exhibited improved dispersion and stabilization of Pd species and the formation of abundant reactive oxygen species, thereby facilitating the activation of CO and O2 molecules. As a result, the catalyst showed remarkable efficiency in catalyzing the low-temperature CO oxidation reaction with a complete CO conversion at 80 °C and stability for over 100 h. [ABSTRACT FROM AUTHOR]

Abstract: Al- and Zn-containing mesoporous molecular sieves (SBA-15) were prepared by an impregnation method and were used as catalysts for the catalytic dehydrogenation and cracking of industrial dipentene, an important natural feedstock. The catalysts were characterized by X-Ray fluorescence spectroscopy (XRF), X-Ray diffraction (XRD), N2 adsorption/desorption, transmission electron microscopy (TEM), magic angle spinning nuclear magnetic resonance (27Al MAS NMR) and Fourier transform infrared spectroscopy (FT-IR) techniques. The characterization results suggest that the active components were introduced without changing the mesostructure of SBA-15. FT-IR revealed that Al/SBA-15 shows weak Brönsted acidity and strong Lewis acidity, while Zn/SBA-15 only possesses moderate Lewis acidity. Dehydrogenation and cracking products, such as toluene, were found in the dipentene conversion over Al/SBA-15, while for Zn/SBA-15, p-cymene was the major dehydrogenation product. Along with the strong Brönsted acidity and high cracking activity of HZSM-5, our results suggest that the reaction pathway is determined by the acidic sites. Stability tests showed the deactivation is also related to the acidity. The highest yield of p-cymene reaches to 86.7% on Zn/SBA-15 at 723K. [Copyright &y& Elsevier]

Mn–Al and Mg–Mn–Al hydrotalcite-like compounds (HTlcs) were synthesized by a coprecipitation method. The activity of the calcined HTlcs for hydrogenation of methyl benzoate to benzaldehyde was tested. The effects of Mn/Al and Mg/Mn ratio, preparation and reaction conditions, and potassium promoter on the catalytic performance of the catalysts were investigated. The prepared catalysts give better performance than conventional 10% Mn/γ-Al2O3 catalyst. The conversion of methyl benzoate and selectivity to benzaldehyde on 3% K/Mg0.2Mn1.8Al1 catalyst at 390 °C are 90.0 and 88.0%, respectively. XRD, TPR and CO2-TPD studies show that the redox and basic properties of the catalysts play important roles in the reaction. A suitable degree of reduction and a small number of basic sites on the catalyst lead to a high activity and selectivity to benzaldehyde. [Copyright &y& Elsevier]

Coalbed methane is a significant source of methane in the atmosphere, which is a potent greenhouse gas with a considerable contribution to global warming, thus it is of great importance to remove methane in coalbed gas before the emission. Exploring the economical non-noble metal catalysts for catalytic methane combustion (CMC) has been a wide concern to mitigate the greenhouse effect caused by the emitted low-concentration methane. Herein, a series of Mn-doped Co3O4 catalysts have been synthesized by the environmentally friendly solid-state method. As a result, the Mn0.05Co1 catalyst performed the best CMC activity (T90 = 370 °C) and good moisture tolerance (3 vol% steam). The introduction of an appropriate amount of manganese conduced Co3O4 lattice distortion and transformed Co3+ to Co2+, thus producing more active oxygen vacancies. Mn0.05Co1 exhibited better reducibility and oxygen mobility. In situ studies revealed that methane was adsorbed and oxidized much easier on Mn0.05Co1, which is the crucial reason for its superior catalytic performance. [ABSTRACT FROM AUTHOR]

Direct conversion of syngas to aromatics over metal oxide‐zeolite (OX‐ZEO) composite catalysts is a novel route for efficient utilization of carbon resources. To realize a high activity with considerable selectivity to aromatics and stability, the design of synergetic OX‐ZEO catalyst to meet complex kinetics still remains a great challenge. In this work, a synergetic dual‐oxide/zeolite catalyst was developed to tune the coupling between CO and H2 activation through active H species migration, by adopting ZnZrOx oxide with stable single‐layer Zn−O structure for H2 activation and CeZrOx oxide with abundant oxygen vacancies as the CO activation component. The ratio and the proximity of CeZrOx and ZnZrOx is essential for the catalyst activity and stability. The optimal catalyst 1CeZrOx‐2ZnZrOx/Z5@Si shows a superior catalytic performance with 75.6 % aromatics selectivity at a CO conversion as high as 57.5 %. After induction period, the catalyst exhibits excellent stability for 1100 h, keeping the high selectivity above 75 % with an average conversion of 43 %. This work will provide a new perspective to design a high performance and long‐life OX‐ZEO composite catalyst for direct conversion of syngas to high value chemicals. [ABSTRACT FROM AUTHOR]

The acidity and Ga-species status in the zeolite play a crucial role in the CO 2 -assisted propane dehydroaromatization (CO 2 -PDA). In this work, a copper modified Ga-MFI zeolite (Cu/Ga-MFI) with well dispersed framework Ga species was fabricated. A remarkable aromatics selectivity of 73% at propane conversion of 93.6% was achieved on Cu/Ga-MFI catalyst. The Ga atoms in MFI framework can create a moderate acid strength, while the introduced Cu provide an appropriate Brønsted/Lewis acid distribution, enhancing the synergy between metal-related species and the zeolite. Besides, DFT results indicate that the acid sites in Ga-MFI are more preferable for the dehydrogenation of propane instead of the C-C cleavage. Moreover, CO 2 can inhibit coke formation through reverse Boudouard and reverse water gas shift reaction, which endows Cu/Ga-MFI catalyst with superior anti-coking ability and regeneration stability. This work provides a novel approach for designing catalysts with high activity, aromatics selectivity, and stability for CO 2 -PDA reactions. [Display omitted] • H-type Al-free Ga-MFI with Ga located in frameworks is successfully fabricated. • Cu/Ga-MFI shows a superior aromatics selectivity and stability in CO 2 -PDA reaction. • The moderate acid strength from Ga in MFI is favored by propane dehydrogenation. • The synergy between Brønsted/Lewis acid is crucial for catalytic performance. • The introduction of Cu promotes CO 2 activation and inhibits the carbon deposition. [ABSTRACT FROM AUTHOR]

Abstract: Dehydrogenation of ethane to ethylene in the presence of carbon dioxide was investigated over various gallium-based catalysts. Ga2O3/HZSM-5 catalysts show better stability than β-Ga2O3, and the higher Si/Al ratio HZSM-5 supported gallium oxide catalysts are more resistant to deactivation. The Ga2O3/HZSM-5(97) catalyst exhibits both high activity and stability for dehydrogenation of ethane, with an ethane conversion of 15% and ethylene selectivity of 94% without any observable trend of deactivation in 70h. The results of NH3-TPD and FT-IR spectra of adsorbed pyridine revealed that the enhancement of the catalyst stability with increasing Si/Al ratio of the support is caused by the decrease of the acidity of the catalysts, resulting in the suppression of the side reactions, such as cracking and oligomerization. The promoting effect of CO2 on the dehydrogenation reaction is attributed to the reverse water gas shift reaction. The catalyst stability is also enhanced by the introduction of CO2. [Copyright &y& Elsevier]

Abstract: Series of Rh/SBA-15 catalysts were prepared by impregnation and grafting method applying different Rh precursors. The catalytic behaviors of N2O decomposition over these catalysts were tested in an automated eight flow reactor system. The catalysts were characterized by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), N2 adsorption/desorption, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. The results showed that the dispersion of Rh species on the catalysts is closely related to the molecular size and the hydrophobic property of the precursors comparing to the hydrophilic support, better dispersion results were found in catalysts by impregnation of smaller precursors, while by grafting better dispersion resulted from big precursor. On the other hand, the activities of the catalysts match well with the Rh dispersion status. Rh/SBA-15-CDCR starting from [(CO)2RhCl]2 showed good dispersion and gave the best N2O decomposition activity. [Copyright &y& Elsevier]

Thermo-catalytic CO 2 hydrogenation with renewable energy has become one of the promising alternatives to fossil carbon-based routes for the production of bulk chemicals and has been extensively researched in recent years. And the heterogeneous oxide–zeolite (OX–ZEO) bifunctional catalysts have received much attention due to their high product selectivity. However, the need for multifunctional active sites, the complexity of tandem cascade reactions and the difficulty in understanding reaction mechanisms pose significant challenges for the design of effective catalysts. In this review, we present an overview of recent advances in the catalytic hydrogenation of CO 2 to value-added products over OX–ZEO bifunctional catalysts, with particular emphasis on the role of the oxide. The nature of the metal oxide, the modification of oxides to improve catalytic performance in CO 2 hydrogenation and the reaction mechanisms are discussed. Finally, the current challenges and future perspectives of the catalytic conversion of CO 2 to hydrocarbons are briefly presented. [Display omitted] • Metal oxides in OX-ZEO bifunctional catalysts for direct hydrogenation of CO 2 are briefly summarized. • Enhancement of OX/ZEO catalytic performance in CO 2 hydrogenation as well as the mechanisms are discussed. • Challenges for OX-ZEO catalysts in hydrogenation of CO 2 into value-added chemicals are addressed. [ABSTRACT FROM AUTHOR]

A series of ZSM-5 zeolites with tunable mesoporosity were synthesized by a facile ultrasound-assisted method. XRD, FT-IR and NH 3 -TPD results exhibited that as-synthesized ZSM-5 kept the MFI structure as well as the original acidity. Traced by TEM techniques, the crystallization process, especially the state of initial amorphous gel, was found notably affected by the ultrasound treatment by breaking the weak bonds, which led to formation of mesopores in crystals. The ZSM-5 catalysts with abundant mesoprores inhibited coking significantly and showed high catalytic stability for methanol to propylene reaction. The Z5-us-60 catalyst exhibited the highest catalytic stability for >600 h at a high WHSV of 4.0 h −1 . [ABSTRACT FROM AUTHOR]

Constructing non-noble robust catalysts for deep catalytic oxidation of obstinate light alkanes at low temperature is of great value and significance. Herein, we designed a facile solvent-thermal-reduction strategy to fabricate an O-vacancy-rich porous MnO 2 nanosheet (MnO 2 −PS) catalyst for propane catalytic oxidation. The abundant vacancies in MnO 2 −PS catalysts can significantly promote its redox ability and oxygen activation capacity, and then provide more active oxygen species with enhanced oxygen mobility and reactivity, thus accelerate the cleavage of C-H bond and the decomposition of intermediates. Meanwhile, benefiting from the porous nanosheet structure, MnO 2 −PS catalyst possesses highly accessible surface and high density of exposed active sites, thus facilitating the adsorption and the activation of reactant molecule. At the same time, the catalyst also exhibits good thermal stability and water resistant ability. This robust and efficient catalytic system may provide some enlightenments for designing feasible catalyst with high-performance for deep catalytic destruction of VOCs. [Display omitted] • O-vacancy-rich porous MnO 2 nanosheets (MnO 2 –PS) catalyst were fabricated through a facile method. • High catalytic performance of propane catalytic oxidation on MnO 2 –PS catalyst was achieved. • The MnO 2 –PS with abundant vacancies exhibits higher density of exposed active sites, higher redox ability and oxygen mobility. [ABSTRACT FROM AUTHOR]

Abstract: Modified high silica HZSM-5 catalysts have been used to selectively transform methanol to propylene (MTP). The HZSM-5 catalyst with a Si/Al ratio of 220 exhibited satisfying catalytic performance (space time yield of propylene is up to 18mmol/gh). The selectivity of propylene can be obviously affected by additives. P leads to a pronounced improvement of propylene selectivity up to 55.6% with complete conversion of methanol. The enhancement of propylene selectivity and catalytic life can be attributed to partial elimination of the strong acid sites on the HZSM-5 catalyst. [Copyright &y& Elsevier]

Abstract: Pt was introduced into pure and polyacrylic acid (PAA) grafting multi-walled carbon nanotubes (MWNTs) by electroless metal deposition method and used as catalysts for hydrogenation of citral. The catalysts exhibited higher activity in the hydrogenation of citral when compared with Pt impregnated active carbon (AC) catalyst, while the selectivity of the catalysts on different MWNTs supports were quite different. The catalyst characterization results reveal that the selectivity of products is related with the morphology of the MWNTs and Pt(111) facet, functionalized carbon nanotubes will orient Pt facet and facilitate its dispersion on support. [Copyright &y& Elsevier]

To improve propane combustion activity and illustrate the promotional effects of molybdenum doping, Pt-Mo/ZSM-5 catalysts with different Mo amounts were prepared by the co-impregnation method. XRD, Raman, H2-TPR, NH3-TPD, in situ DRIFTs, XPS and other characterizations were performed. The results indicated that the concentration of Pt0 in Pt/ZSM-5 catalyst increased after the doping of Mo and the content of Pt0 had a positive correlation with the reaction turnover frequency value. The propane combustion activity of Pt/ZSM-5 catalyst was significantly improved after the doping of molybdenum species. Among all the catalysts, Pt-6Mo/ZSM-5 catalyst (Pt/ZSM-5 with 6 wt.% Mo modification) showed the lowest T50 and T90 for propane catalytic combustion. Moreover, the Pt-Mo/ZSM-5 catalyst exhibited outstanding catalytic stability. [ABSTRACT FROM AUTHOR]

An effective and safe route is proposed to prepare supported Mo2C-based catalysts from organic–inorganic hybrids, which exhibit high activity and stability for producing H2from methanol catalytic decomposition. [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) have recently been used as precursors of the catalysts for the combustion of volatile organic compounds (VOCs). In the present work, three kinds of CeO2 catalysts were successfully synthesized from Ce-MOF-808, Ce-BTC, and Ce-UiO-66, with specific topological structures and coordinate environments. Catalysts with small particle size, stacking mode, and structural defects could be created by pyrolysis of Ce-MOFs, which affects the activity in the toluene combustion significantly. Raman spectra, XPS, and OSC studies were performed to reveal the formation of defect sites. The thermal redox properties were determined by H2-TPR. Catalytic activity tests were conducted on the toluene combustion, and CeO2-MOF-808 showed the best catalytic performance (T90 = 278 °C) due to its having the largest specific surface area, abundant active surface oxygen species, and low-temperature reducibility. [ABSTRACT FROM AUTHOR]