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This study aims to investigate the catalytic activity of spinel-type oxides (NixCoyO4) for the oxidation of toluene and carbon monoxide at low temperatures. A series of Ni/Co catalysts with different mole ratios were synthesized via citric acid assisted sol-gel method and the influence of the nickel to cobalt ratios on the properties and catalytic performance of NixCoyO4 were investigated by characterization such as XRD, SEM-EDX, BET, H2–TPR. The results indicate that the catalyst with the Ni/Co atomic ratio of 1.5/1.5 exhibits the highest complete toluene oxidation activity, with 85% toluene conversion rate at 100 – 250 °C and complete toluene oxidation at 300 °C. However, for the complete oxidation of CO, the Ni/Co atomic ratio of 1/2 exhibits higher activity, converting 100% CO at 150 °C. The results show that NiO and CoOx are proved to be more active than the other for the oxidation of toluene and CO, respectively. The characteristic results show that high surface area, small particle size, good temperature reducibility, and oxygen species with high mobility in low-temperature regions are responsible for the catalytic performance of nickel cobalt spinel-type catalyst for toluene and carbon monoxide oxidation. The good stability of the Ni-Co oxide catalysts for the oxidation reactions originates from the strong Ni-Co interaction. [ABSTRACT FROM AUTHOR]

Highly dispersed Ni nanoparticles supported on high-surface-area mesoporous nanocrystalline MgAl2O4 powder was generated by a facile and simple propylene oxide assisted gelation agent route. The mesoporous spinel materials exhibited enhanced catalytic performance for hydrogen production in biogas dry reforming. The obtained spinel catalysts with different Ni loadings after calcination at 700 °C possessed high BET surface areas (236-224 m2 g−1). A narrow pore size distribution in the mesopore range was observed in the samples, and all the samples except 2.5 wt % Ni showed a mesoporous-macroporous structure. The 5 wt % Ni/MgAl2O4 sample showed the highest activity for the biogas dry reforming reaction because of the high dispersion of Ni on the mesoporous surface of the spinel support. X-ray photoelectron spectroscopy revealed that the catalysts with a low Ni loading undergo the exchange of Mg2+ by Ni2+, whereas catalysts with a higher Ni loading undergo the substitution of Al3+ by Ni3+. Thus, appropriate partial Ni substitution in the MgAl2O4 support may play a role in the elevated catalytic performance. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate a method used to tune the selectivity of LaNiO3 (LNO) perovskite catalysts through the substitution of La with K cations. LNO perovskites were synthesised using a simple sol-gel method, which exhibited 100% selectivity towards the methanation of CO2 at all temperatures investigated. La cations were partially replaced by K cations to varying degrees via control of precursor metal concentration during synthesis. It was demonstrated that the reaction selectivity between CO2 methanation and the reverse water gas shift (rWGS) could be tuned depending on the initial amount of K substituted. Tuning the selectivity (i.e., ratio of CH4 and CO products) between these reactions has been shown to be beneficial for downstream hydrocarbon reforming, while valorizing waste CO2. Spectroscopic and temperature-controlled desorption characterizations show that K incorporation on the catalyst surface decrease the stability of C-based intermediates, promoting the desorption of CO formed via the rWGS prior to methanation. [ABSTRACT FROM AUTHOR]

Mesoporous nanocrystalline Mg 1-x Ni x Al 2 O 4 (x = 0.10, 0.13, 0.17 and 0.20) with large surface area were synthesized via a simple one-step sol-gel method using nonprecious metals. The prepared Mg 1-x Ni x Al 2 O 4 catalysts exhibit good catalytic performance towards methane and carbon dioxide dry reforming reaction. The catalysts were evaluated by various techniques, including XRD, BET, TPR, TPO, EPR, Chemisorption, SEM and TEM. All the Ni incorporated MgAl 2 O 4 samples possessed high BET area (296–305 m 2 g −1 ) and pore volume (0.47–0.56 cm 3 g −1 ) with small pore size (6.4–7.4 nm) in meso region after calcination at 700 °C. The TPR results suggested strong interaction effect in Ni Mg and the reducibility property of the catalysts improved with the increase of nickel doping. Mg 0.8 Ni 0.2 Al 2 O 4 exhibited the highest activity for biogas dry reforming with 72.6% CH 4 and 80.7% CO 2 conversion at 700 °C. Electron paramagnetic resonance (EPR) results indicated that the incorporation of Ni in MgAl 2 O 4 spinel lattice led to the lattice distortion and formed oxygen vacancies which are a benefit for the dry reforming reaction. [ABSTRACT FROM AUTHOR]

A simple, template-free and scalable modified sol-gel route was developed for the synthesis of mesoporous flake-like magnesium aluminate spinel (MgAl 2 O 4 ) at low temperature (700 °C) with high surface area (281 m 2 g −1 ). The obtained spinel materials were characterized by means of physicochemical techniques including X-ray diffraction, thermogravimetric analysis, scanning electron microscopy with energy-dispersive X-ray spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and N 2 adsorption-desorption analysis. The propylene oxide was used as gelation and pore forming agent in the sol-gel process. Different morphologies and sizes of flake were generated by the varied synthesis conditions. The result materials reveal that the textural properties of the MgAl 2 O 4 product are strongly associated with the nature and amount of addictive solvent and calcination temperatures. It shows that the BET surface area decrease as the increase of calcination temperature and the optimal temperature of 700 °C result in the pure phase of MgAl 2 O 4 spinel. This synthesis strategy offers a feasible approach for scalable fabrication of mixed metal oxides for various catalytic reactions or catalyst supports due to the large surface area. [ABSTRACT FROM AUTHOR]

Abstract: In this work, cerium–tungsten oxide catalysts were prepared by three methods: single step sol–gel (SG), impregnation (IM), and solid processing (SP). The catalysts were used for selective catalytic reduction (SCR) of NO x with ammonia over a wide temperature range. The results indicated that the catalysts prepared by the SP and IM methods exhibited better SCR activity than that prepared via the SG method in 175–500°C. The excellent activity can be attributed to larger surface area, higher surface concentrations of Ce and Ce3+, enhanced NO oxidization ability, and greater number of surface acid sites. [Copyright &y& Elsevier]