The generation of synthesis gas (hydrogen and carbon monoxide mixture) from two global warming gases of carbon dioxide and methane via dry reforming is environmentally crucial and for the chemical industry as well. Herein, magnesium-promoted NiO supported on mesoporous zirconia, 5Ni/xMg–ZrO₂ (x = 0, 3, 5, 7 wt%) were prepared by wet impregnation method and then were tested for syngas production via dry reforming of methane. The reaction temperature at 800 °C was found more catalytically active than that at 700 °C due to the endothermic feature of reaction which promotes efficient CH₄ catalytic decomposition over Ni and Ni–Zr interface as confirmed by CH₄–TSPR experiment. NiO–MgO solid solution interacted with ZrO₂ support was found crucial and the reason for high CH₄ and CO₂ conversions. The highest catalyst stability of the 5Ni/3Mg–ZrO₂ catalyst was explained by the ability of CO₂ to partially oxidize the carbon deposit over the surface of the catalyst. A mole ratio of hydrogen to carbon monoxide near unity (H₂/CO ~ 1) was obtained over 5Ni/ZrO₂ and 5Ni/5Mg–ZrO₂, implying the important role of basic sites. Our approach opens doors for designing cheap and stable dry reforming catalysts from two potent greenhouse gases which could be of great interest for many industrial applications, including syngas production and other value-added chemicals.

Caprolactam is the precursor of many industrial chemical productions as in nylon industry, plastic industry, paint industry, lysine synthesis and cross-linking for polyurethanes. The production of caprolactam has been focus much from last three decades among the scientific community to fulfill the industrial need under environment precautions. Herein a sequential and explanatory review broadly covering the transformation of a different substrate as cyclohexanone oxime, cyclohexanone, cyclohexanol, cyclohexane, and biorenewable sources into caprolactam is presented. For every substrate, a wide range of catalyst including homogeneous as well as the heterogeneous system has been deeply considered. This study will be helpful for developing alternative industrial route for production of caprolactam. Graphical abstract

Highly stable gold nanoparticles immobilized on the surface of amine-functionalized nanocomposite microspheres possessing a magnetite (Fe₃O₄) nanoparticle core and a silica (SiO₂) shell (Au/SiO₂-shell/Fe₃O₄-core) were prepared. These gold nanocomposite catalysts were tested for 4-nitrophenol (4-NP) and 2-nitroaniline (2-NA) reduction in aqueous solution in the temperature range 293–323 K and in the presence of aqueous NaBH₄ reducing agent. The magnetically recyclable gold catalyst showed high stability (∼3 months), efficient recyclability (up to 10 cycles), and high activity (∼100% conversion within 225 s, ∼700 ppm 4-NP or 2-NA). The pseudo-first-order apparent reaction rate constants (k) of 4-NP and 2-NA reduction were 7.5 × 10^–3 and 4.1 × 10^–3 s^–1, respectively, and with an apparent catalytic activity of 4.48 × 10^–8 kmol/(m³ s).

Developing cost-effective nonprecious active metal-based catalysts for syngas (H₂/CO) production via the dry reforming of methane (DRM) for industrial applications has remained a challenge. Herein, we utilized a facile and scalable mechanochemical method to develop Ba-promoted (1-5 wt %) zirconia and yttria-zirconia-supported Ni-based DRM catalysts. BET surface area and porosity measurements, infrared, ultraviolet-visible, and Raman spectroscopy, transmission electron microscopy, and temperature-programmed cyclic (reduction-oxidation-reduction) experiments were performed to characterize and elucidate the catalytic performance of the synthesized materials. Among different catalysts tested, the inferior catalytic performance of 5Ni/Zr was attributed to the unstable monoclinic ZrO₂ support and weakly interacting NiO species whereas the 5Ni/YZr system performed better because of the stable cubic ZrO₂ phase and stronger metal-support interaction. It is established that the addition of Ba to the catalysts improves the oxygen-endowing capacity and stabilization of the cubic ZrO₂ and BaZrO₃ phases. Among the Ba-promoted catalysts, owing to the optimal active metal particle size and excess ionic CO₃ ^2- species, the 5Ni4Ba/YZr catalyst demonstrated a high, stable H₂ yield (i.e., 79% with a 0.94 H₂/CO ratio) for up to 7 h of time on stream. The 5Ni4Ba/YZr catalyst had the highest H₂ formation rate, 1.14 mol g^-1 h^-1 and lowest apparent activation energy, 20.07 kJ/mol, among all zirconia-supported Ni catalyst systems.