Chapter 7
The Reactions with Monoxides
for Pollution Removal
7.1 Introduction
In general, the main cluster types include naked clusters without stabilizing ligands.
Besides, there are abundant investigations on ligand-protected clusters which serve
as building blocks in numerous materials [1]. The stability of such clusters is often
reconciled by ligands granting the cluster a closed electronic shell through covalent
or ionic bonding [2]. For example, clusters especially gold usually employ a class of
ligands including thiols [3–9] and phosphines [10–13] to improve the stabilization.
In gas phase, typical clusters for main group elements can be stabilized by hydride
ligands; while for transition metal clusters, typical stabilizing ligands have been
found to be carbon monoxide (also halides, isocyanides, alkenes and hydrides, etc.)
[1, 14–19]. These ligands undergo electronegative bonding with the metallic core
of the cluster, perturbing the electronic structure of the cluster. In this chapter, we
will present the curious influence of CO encountering metal clusters. In addition
to exploring the stability of cluster species in protection of such ligands, equitable
research interest in studying the cluster reactivity of metals and metal oxides with
carbon monoxide has also been recognized of importance in catalysis. Transition
metal oxides (molecules or clusters) provide good catalytic activity in oxidation
reactions due to the potential advantage that the oxygen atoms are bound atomically
to the transition metal atoms and there are no O–O bonds unless the oxygen to metal
ratio is large [20].
It is well-known that CO is used to manufacture steel from iron ore in blast
furnaces where the general reactions are “Fe 2 O 3 + 3CO = 2Fe + 3CO 2 , Fe 3 O 4 +
4CO = 3Fe + 4CO 2 ” [21, 22]. However, as the reaction to provide CO by “C + CO 2
= 2CO” is reversible, there is always some CO included in the exhaust gas polluting
air if no effective treatments. In addition to the exhaust gas in metal smelting, the
environmentally harmful gas, CO, is also involved in automobile exhaust. In general,
the oxidation of CO to CO 2 is an important environmental reaction to the abatement
of harmful carbon monoxide gas. This reaction involves breaking the O–O bond of
© The Editor(s) (if applicable) and The Author(s), under exclusive license
to Springer Nature Singapore Pte Ltd. 2020
Z. Luo and S. N. Khanna, Metal Clusters and Their Reactivity,
https://doi.org/10.1007/978-981-15-9704-6_7
97
The Reactions with Monoxides
for Pollution Removal
7.1 Introduction
In general, the main cluster types include naked clusters without stabilizing ligands.
Besides, there are abundant investigations on ligand-protected clusters which serve
as building blocks in numerous materials [1]. The stability of such clusters is often
reconciled by ligands granting the cluster a closed electronic shell through covalent
or ionic bonding [2]. For example, clusters especially gold usually employ a class of
ligands including thiols [3–9] and phosphines [10–13] to improve the stabilization.
In gas phase, typical clusters for main group elements can be stabilized by hydride
ligands; while for transition metal clusters, typical stabilizing ligands have been
found to be carbon monoxide (also halides, isocyanides, alkenes and hydrides, etc.)
[1, 14–19]. These ligands undergo electronegative bonding with the metallic core
of the cluster, perturbing the electronic structure of the cluster. In this chapter, we
will present the curious influence of CO encountering metal clusters. In addition
to exploring the stability of cluster species in protection of such ligands, equitable
research interest in studying the cluster reactivity of metals and metal oxides with
carbon monoxide has also been recognized of importance in catalysis. Transition
metal oxides (molecules or clusters) provide good catalytic activity in oxidation
reactions due to the potential advantage that the oxygen atoms are bound atomically
to the transition metal atoms and there are no O–O bonds unless the oxygen to metal
ratio is large [20].
It is well-known that CO is used to manufacture steel from iron ore in blast
furnaces where the general reactions are “Fe 2 O 3 + 3CO = 2Fe + 3CO 2 , Fe 3 O 4 +
4CO = 3Fe + 4CO 2 ” [21, 22]. However, as the reaction to provide CO by “C + CO 2
= 2CO” is reversible, there is always some CO included in the exhaust gas polluting
air if no effective treatments. In addition to the exhaust gas in metal smelting, the
environmentally harmful gas, CO, is also involved in automobile exhaust. In general,
the oxidation of CO to CO 2 is an important environmental reaction to the abatement
of harmful carbon monoxide gas. This reaction involves breaking the O–O bond of
© The Editor(s) (if applicable) and The Author(s), under exclusive license
to Springer Nature Singapore Pte Ltd. 2020
Z. Luo and S. N. Khanna, Metal Clusters and Their Reactivity,
https://doi.org/10.1007/978-981-15-9704-6_7
97