Mond process
Encyclopedia
The Mond process, sometimes known as the carbonyl process is a technique created by Ludwig Mond
in 1890 to extract and purify nickel
. The process was used commercially before the end of the 19th century. It is done by converting nickel oxides (nickel combined with oxygen
) into pure nickel.
This process makes use of the fact that carbon monoxide
complexes with nickel
readily and reversibly to give nickel carbonyl
. No other element forms a carbonyl compound under the mild conditions used in the process.
This process has three steps:
1. Nickel oxide is reacted
with Syngas
at 200 °C to remove oxygen, leaving impure nickel. Impurities include iron
and cobalt
.
2. The impure nickel is reacted with excess carbon monoxide
at 50–60 °C to form nickel carbonyl
.
3. The mixture of excess carbon monoxide and nickel carbonyl is heated to 220–250 °C. On heating, nickel tetracarbonyl decomposes to give nickel:
The decomposition may be engineered to produce powder, but more commonly an existing substrate is coated with nickel. For example, nickel pellets are made by dropping small, hot pellets through the carbonyl gas; this deposits a layer of nickel onto the pellets.
This process has also been used for plating nickel onto other metals, where a complex shape or sharp corners made good results difficult by electroplating. Although the results are good, the toxicity makes it impractical as an industrial process. Such parts are now plated by electroless nickel plating
instead.
Ludwig Mond
Dr Ludwig Mond , was a German-born chemist and industrialist who took British nationality.-Education and career:...
in 1890 to extract and purify nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
. The process was used commercially before the end of the 19th century. It is done by converting nickel oxides (nickel combined with oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
) into pure nickel.
This process makes use of the fact that carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
complexes with nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
readily and reversibly to give nickel carbonyl
Nickel carbonyl
Nickel carbonyl is the organonickel compound with the formula Ni4. This pale-yellow liquid is the principal carbonyl of nickel. It is an intermediate in the Mond process for the purification of nickel and a reagent in organometallic chemistry...
. No other element forms a carbonyl compound under the mild conditions used in the process.
This process has three steps:
1. Nickel oxide is reacted
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
with Syngas
Syngas
Syngas is the name given to a gas mixture that contains varying amounts of carbon monoxide and hydrogen. Examples of production methods include steam reforming of natural gas or liquid hydrocarbons to produce hydrogen, the gasification of coal, biomass, and in some types of waste-to-energy...
at 200 °C to remove oxygen, leaving impure nickel. Impurities include iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
and cobalt
Cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
.
- NiO (s) + H2 (g) → Ni (s) + H2O (g)
2. The impure nickel is reacted with excess carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
at 50–60 °C to form nickel carbonyl
Nickel carbonyl
Nickel carbonyl is the organonickel compound with the formula Ni4. This pale-yellow liquid is the principal carbonyl of nickel. It is an intermediate in the Mond process for the purification of nickel and a reagent in organometallic chemistry...
.
- Ni (s) + 4 CO (g) → Ni(CO)4 (g)
3. The mixture of excess carbon monoxide and nickel carbonyl is heated to 220–250 °C. On heating, nickel tetracarbonyl decomposes to give nickel:
- Ni(CO)4 (g) → Ni (s) + 4 CO (g)
The decomposition may be engineered to produce powder, but more commonly an existing substrate is coated with nickel. For example, nickel pellets are made by dropping small, hot pellets through the carbonyl gas; this deposits a layer of nickel onto the pellets.
This process has also been used for plating nickel onto other metals, where a complex shape or sharp corners made good results difficult by electroplating. Although the results are good, the toxicity makes it impractical as an industrial process. Such parts are now plated by electroless nickel plating
Electroless nickel plating
Electroless nickel plating is an auto-catalytic chemical technique used to deposit a layer of nickel-phosphorus or nickel-boron alloy on a solid workpiece, such as metal or plastic. The process relies on the presence of a reducing agent, for example hydrated sodium hypophosphite which reacts with...
instead.