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The reaction of methane decomposition is an endothermic process that produces hydrogen without any impurities as a gas product and carbon nanotubes/carbon nanofibers as a solid product. In this study, NiO–MgO catalysts with different nickel loadings (20, 30, 40, and 50 wt. %) were synthesized using the mechanochemical method. The Physicochemical features of the synthesized catalysts were characterized by various methods such as BET, XRD, SEM, TPO, and H2-TPR. The prepared samples were tested in the methane decomposition process at various temperatures under the GHSV value of 48,000 ml/(gcat h). Among the prepared samples, the 50wt.%NiO–MgO exhibited the best activity (40% methane conversion at 575 °C) in this process due to its higher concentration of active metal and better catalyst reducibility. Also, the effect of different parameters such as feed ratio, GHSV, and calcination temperature was studied on the activity of this catalyst. The results showed that with the increase of GHSV and feed ratio, the methane conversion decreased due to the lesser contact time and diminishing the proportion of accessible active sites per methane entrance molecules. Moreover, the results showed that with the rise of calcination temperature from 500 to 700 °C, the methane conversion decreased due to the sintering of nickel particles. The results also showed that the addition of 15 wt.% Cr2O3 to the catalyst formulation improved the catalytic performance and lifetime in the thermocatalytic decomposition of methane due to the higher reducibility and dispersion of the active species on the catalyst surface. [ABSTRACT FROM AUTHOR]

VOHPO·0.5HO synthesized via the alcohol reduction of VOPO·2HO was mechanochemical treated for 30 min in three different media, i.e. cyclohexane, ethanol and air. XRD results revealed that their structure became less crystalline compared to the unmilled material. SEM showed that the particles for the milled materials become smaller and unique features were observed in the different type of media used. The reactivity of the oxygen species linked to V and V were also affected by the milling process. The selectivity to maleic anhydride from n-butane oxidation were observed to increase in line with the increase in the oxygen species associated with V and the presence of isolated V phase. A correlation was observed between the crystallite size of the pyrophosphate phase at (020) plane with the maleic anhydride selectivity. Graphical Abstract: [Figure not available: see fulltext.]. [ABSTRACT FROM AUTHOR]