Inverse Oxide/Metal Catalysts for CO₂ Hydrogenation to Methanol

Abstract

The hydrogenation of CO 2 to methanol using heterogeneous catalysts is an appealing route for mitigating greenhouse gas emissions and generating useful products. The synthesis of methanol is attractive due to its utilization as a fuel, a fuel additive, or an intermediate for a wide array of industrial chemicals. Traditional catalytic systems, like those based on Cu or Ni, have been extensively explored but have thus far shown limited conversion and selectivity to desired products like methanol primarily due to the chemical stability of CO 2 . These catalysts are also difficult to use industrially due to the high pressures and temperatures needed for these catalytic reactions. In the search for improvements in the reaction rates, conversion, and selectivity to liquid products, inverse oxide/metal catalysts have been recently explored and have yielded promising results. This review summarizes the latest advances in the use of inverse catalysts for the hydrogenation of CO 2 to methanol. First, this review focuses on some strategies for synthesizing inverse oxide/metal catalysts. Next, the relationship between the interfacial properties and the catalytic activity is reviewed, emphasizing the nature of the oxide layer and its dispersion on the metal surface. Lastly, the activities of inverse catalysts and materials prepared by traditional synthesis approaches are compared.

ZrO2-Promoted Cu-Co, Cu-Fe and Co-Fe Catalysts for Higher Alcohol Synthesis

“…In contrast to the more commonly reported supported metal catalysts, the presence of low quantities of metal oxide on active metals is a shared characteristic among all of the families investigated. Rodriguez et al initially introduced the term “inverse catalyst” for model systems exhibiting layers of metal oxides on flat metal surfaces. − Subsequently, this term has been extended to describe more realistic catalysts in the related water–gas shift and methanol synthesis reactions, among other applications. − However, the precise boundaries in terms of composition and physical or catalytic properties of this concept remain elusive, precluding a clear distinction from the established concept of promotion of bulk metal catalysts by metal oxides. In our view, the term “inverse catalyst” may appropriately describe the general architecture involving relatively low amounts of oxides dispersed on bulk metals, whereas the term “promoted” would imply enhanced performance relative to the oxide-free bulk metals.…”

“…Rodriguez et al initially introduced the term “inverse catalyst” for model systems exhibiting layers of metal oxides on flat metal surfaces. 25 − 27 Subsequently, this term has been extended to describe more realistic catalysts in the related water–gas shift and methanol synthesis reactions, among other applications. 28 − 30 However, the precise boundaries in terms of composition and physical or catalytic properties of this concept remain elusive, precluding a clear distinction from the established concept of promotion of bulk metal catalysts by metal oxides.…”

“…Interactions between oxide supports and active metal nanoparticles do not only stabilize the latter, but could also induce surface reconstruction or confer promotional qualities for intermediate formation in HAS, among other general effects of structural and electronic nature. ,, Increased dispersion or confinement of M 1 M 2 particles by large amounts of bulk MO x tends to reduce the degree of sintering at the expense of a modest density of interfacial active sites. More recently, reversing the traditional catalyst architecture by dispersing the metal oxide (typically <20% of the total composition) on the surface of active metals has created alternative configurations with increased interfacial site densities − with promise mostly in model surfaces for relatively simple reactions such as CO and CO 2 methanation, CO oxidation, water–gas shift and methanol synthesis. − Inspired by these developments, we explore the potential of using relatively low quantities of highly dispersed metal oxides on the surface of bimetallic m-FTS catalysts (denoted by M 1α M 2β @MO x -γ, where γ represents the molar MO x content, Figure ) as promoters in HAS. This research was first developed for the most widely studied Co-Cu family and later generalized to Cu-Fe and Co-Fe systems.…”

CO2heterogeneous hydrogenation to carbon-based fuels: recent key developments and perspectives

“…240 Meanwhile, the use of inverse oxide/metal catalysts are also considered to be an effective strategy for improving CO 2 hydrogenation to methanol. [241][242][243] Wu et al ascribed the high activity to the formation of a highly reactive HCOO-Cu intermediate adsorbed on the metallic Cu of the inverse ZrO 2 /Cu catalyst (Fig. 16e).…”

Mechanism of Methanol Synthesis from CO2 Hydrogenation over Cu/γ-Al2O3 Interface: Influences of Surface Hydroxylation

“…The hydrogenation of carbon dioxide to methanol has attracted considerable attention because it offers an efficient way to reduce CO 2 concentrations [1][2][3][4][5], the resulting methanol is high-value-added and it can be used as a renewable fuel and a convenient feedstock for chemical processes [6][7][8]. Due to the chemical inertness of CO 2 , many catalysts have been proposed to achieve the conversion of CO 2 to CH 3 OH, in which the most representative is the metal catalyst supported on the oxide surface [3,9].…”