Steering of methanol reforming selectivity by zirconia–copper interaction

Steering the Catalytic Properties of Intermetallic Compounds and Alloys in Reforming Reactions by Controlled in Situ Decomposition and Self-Activation

Based on the increasing importance of intermetallic compounds and alloys in heterogeneous catalysis, we explore the possibilities of using selected intermetallic compounds and alloy structures and phases as catalyst precursors to prepare highly active and CO2-selective methanol steam reforming (MSR) as well as dry reforming of methane (DRM) catalyst entities by controlled in situ decomposition and self-activation. The exemplary discussed examples (Cu51Zr14, CuZn, Pd2Zr, GaPd2, Cu2In, ZnPd, and InPd) show both the advantages and pitfalls of this approach and how the concept can be generalized to encompass a wider set of intermetallic compounds and alloy structures. Despite the common feature of all systems being the more or less pronounced decomposition of the intermetallic compound surface and bulk structure and the in situ formation of much more complex catalyst entities, differences arise due to the oxidation propensity and general thermodynamic stability of the chosen intermetallic compound/alloy and their constituents. The metastability and intrinsic reactivity of the evolving oxide polymorph introduced upon decomposition and the surface and bulk reactivity of carbon, governed by the nature of the metal/intermetallic compound-oxide interfacial sites, are of equal importance. Structural and chemical rearrangements, dictating the catalytic performance of the resulting entity, are present in the form of a complete destruction of the intermetallic compound bulk structure (Cu51Zr14) and the formation of an metal/oxide (Cu51Zr14, InPd) or intermetallic compound/oxide (ZnPd, Cu2In, CuZn) interface or the intertranformation of intermetallic compounds with varying composition (Pd2Zr) before the formation of Pd/ZrO2. In this Perspective, the prerequisites to obtain a leading theme for pronounced CO2 selectivity and high activity will be reviewed. Special focus will be put on raising awareness of the intrinsic properties of the discussed catalyst systems that need to be controlled to obtain catalytically prospective materials. The use of model systems to bridge the material's gap in catalysis will also be highlighted for selected examples.

Intermetallic compounds in catalysis - a versatile class of materials meets interesting challenges

The large and vivid field of intermetallic compounds in catalysis is reviewed to identify necessities, strategies and new developments making use of the advantageous catalytic properties of intermetallic compounds. Since recent reviews summarizing contributions in heterogeneous catalysis as well as electrocatalysis are available, this contribution is not aiming at a comprehensive literature review. To introduce the field, first the interesting nature of intermetallic compounds is elaborated - including possibilities as well as requirements to address catalytic questions. Subsequently, this review focuses on exciting developments and example success stories of intermetallic compounds in catalysis. Since many of these are based on recent advances in synthesis, a short overview of synthesis and characterisation is included. Thus, this contribution aims to be an introduction to the newcomer as well as being helpful to the experienced researcher by summarising the different approaches. Selected examples from literature are chosen to illustrate the versatility of intermetallic compounds in heterogeneous catalysis where the emphasis is on developments since the last comprehensive review in the field.

Copper–Zirconia Catalysts: Powerful Multifunctional Catalytic Tools to Approach Sustainable Processes

Copper–zirconia catalysts find many applications in different reactions owing to their unique surface properties and relatively easy manufacture. The so-called methanol economy, which includes the CO2 and CO valorization and the hydrogen production, and the emerging (bio)alcohol upgrading via dehydrogenative coupling reaction, are two critical fields for a truly sustainable development in which copper–zirconia has a relevant role. In this review, we provide a systematic view on the factors most impacting the catalytic activity and try to clarify some of the discrepancies that can be found in the literature. We will show that contrarily to the large number of studies focusing on the zirconia crystallographic phase, in the last years, it has turned out that the degree of surface hydroxylation and the copper–zirconia interphase are in fact the two mostly determining factors to be controlled to achieve high catalytic performances.

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.

Chemical vapor deposition-prepared sub-nanometer Zr clusters on Pd surfaces: promotion of methane dry reforming

An inverse Pd–Zr model catalyst was prepared by chemical vapor deposition (CVD) using zirconium-t-butoxide (ZTB) as an organometallic precursor.