Composition Effect on the Formation of Oxide Phases by Thermal Decomposition of CuNiM(III) Layered Double Hydroxides with M(III) = Al, Fe

The thermal decomposition processes of coprecipitated Cu-Ni-Al and Cu-Ni-Fe hydroxides and the formation of the mixed oxide phases were followed by thermogravimetry and derivative thermogravimetry analysis (TG - DTG) and in situ X-ray diffraction (XRD) in a temperature range from 25 to 800 °C. The as-prepared samples exhibited layered double hydroxide (LDH) with a rhombohedral structure for the Ni-richer Al- and Fe-bearing LDHs and a monoclinic structure for the CuAl LDH. Direct precipitation of CuO was also observed for the Cu-richest Fe-bearing samples. After the collapse of the LDHs, dehydration, dehydroxylation, and decarbonation occurred with an overlapping of these events to an extent, depending on the structure and composition, being more pronounced for the Fe-bearing rhombohedral LDHs and the monoclinic LDH. The Fe-bearing amorphous phases showed higher reactivity than the Al-bearing ones toward the crystallization of the mixed oxide phases. This reactivity was improved as the amount of embedded divalent cations increased. Moreover, the influence of copper was effective at a lower content than that of nickel.

Cu oxide deposited on shape-controlled ceria nanocrystals for CO oxidation: influence of interface-driven oxidation states on catalytic activity

The polar CeO2 (100) surface facets contribute considerably to the formation of surface hydroxyl groups, which are necessary for selective, stable Cu1+ state loading and enhancement of CO oxidation activity.

The Promotional Effects of ZrO2 and Au on the CuZnO Catalyst Regarding the Durability and Activity of the Partial Oxidation of Methanol

The promoter ZrO2 was applied to prevent Cu crystallites from sintering over CZ (ca. Cu 30 wt.% and Zn 70 wt.%) under partial oxidation of the methanol (POM) reaction. Gold was selected to promote the performance of CZrZ (ca. Cu 31 wt.%, Zr 16 wt.%, and Zn 53 wt.%) catalyst to overcome a high ignition temperature of 175 °C and CO selectivity (SCO) (>10% at T. > 200 °C). Experimentally, the deactivation rate constant of A5CZrZ (ca. Au 5 wt.%, Cu 31 wt.%, Zr 17 wt.%, and Zn 47 wt.%) and CZrZ was 1.7 times better than A5CZ (ca. Au 5 wt.%, Cu 31 wt.%, and Zn 64 wt.%) and CZ. The methanol conversion of CZrZ and A5CZrZ catalysts was kept higher than 70% for 12 h in an accelerated aging process. Meanwhile, the Au prompted more methoxy species oxidizing to formate on Cu+-rich A5CZrZ surface at lower temperature, and also improved CO transfer from formate reacting with moveable oxygen to form CO2. The SCO can lower to ca. 6% at 200 °C after adding 3–5% of gold promoter. These features all prove that the CZ catalyst with ZrO2 and Au promoters could enhance catalytic activity, lower the SCO and ignition temperature, and maintain good durability in the POM reaction.

Layered Double Hydroxides-Based Materials as Oxidation Catalysts

This chapter is focused on the transition-metal-containing LDHs-based materials having potential applications in both catalytic selective oxidation for obtaining chemicals and intermediates, and complete oxidation as a promising valuable technology for the destruction of Volatile Organic Compounds (VOCs).

Catalytic Reforming of Oxygenates: State of the Art and Future Prospects

This Review describes recent advances in the design, synthesis, reactivity, selectivity, structural, and electronic properties of the catalysts for reforming of a variety of oxygenates (e.g., from simple monoalcohols to higher polyols, then to sugars, phenols, and finally complicated mixtures like bio-oil). A comprehensive exploration of the structure-activity relationship in catalytic reforming of oxygenates is carried out, assisted by state-of-the-art characterization techniques and computational tools. Critical emphasis has been given on the mechanisms of these heterogeneous-catalyzed reactions and especially on the nature of the active catalytic sites and reaction pathways. Similarities and differences (reaction mechanisms, design and synthesis of catalysts, as well as catalytic systems) in the reforming process of these oxygenates will also be discussed. A critical overview is then provided regarding the challenges and opportunities for research in this area with a focus on the roles that systems of heterogeneous catalysis, reaction engineering, and materials science can play in the near future. This Review aims to present insights into the intrinsic mechanism involved in catalytic reforming and provides guidance to the development of novel catalysts and processes for the efficient utilization of oxygenates for energy and environmental purposes.

Catalytic partial oxidation of methanol and ethanol for hydrogen generation

Hydrogen-powered fuel cell vehicles feature high energy efficiency and minor environmental impact. Liquid fuels are ideal hydrogen carriers, which can catalytically be converted into syngas or hydrogen to power vehicles. Among the potential liquid fuels, alcohols have several advantages. The hydrogen/carbon ratio is higher than that of other liquid hydrocarbons or oxygenates, especially in the case of methanol. In addition, alcohols can be derived from renewable biomass resources. Catalytic partial oxidation of methanol or ethanol offers immense potential for onboard hydrogen generation due to its rapid reaction rate and exothermic nature. These benefits stimulate a burgeoning research community in catalyst design, reaction engineering, and mechanistic investigation. The purpose of this Minireview is to provide insight into syngas and hydrogen production from methanol and ethanol partial oxidation, particularly highlighting catalytic chemistry.