AS THE VERSATILE element which forms the basis for all organic chemistry, carbon has two important inorganic oxides.

Carbon dioxide is perhaps the more renowned of the two, while the other, carbon monoxide, only ever seems to be in the news when it has killed someone – which is surprisingly often for a small molecule.

For the common man, carbon monoxide (CO) is synonymous with harmful effects, but for our industry it is a vital gas which finds application in a score of areas.

CO is a colourless, odourless and tasteless, yet highly toxic gas, produced from the partial oxidation of carbon containing compounds, notably in internal-combustion engines.

CO forms in preference to the more usual carbon dioxide, when there is a reduced availability of oxygen present during the combustion process.

CO has significant fuel value, burning in air with a characteristic blue flame, producing carbon dioxide and despite its serious toxicity, plays a highly useful role in modern industry as a precursor to myriad products.

Chemical industries use large quantities of carbon monoxide, in particular to produce polyurethanes (foams, insulation) and polycarbonates (CDs, computer cases).

Industrial production
Industry has developed several different methods of making the gas.

Heating carbon in the form of coke, with a limited supply of oxygen, forms carbon monoxide. In this process the product is called ‘producer gas’.

Producer gas is formed by the combustion of carbon in oxygen at high temperatures, when there is an excess of carbon. In an oven, air is passed through a bed of coke and the initially produced CO2 equilibrates with the remaining hot carbon to give CO.

The downside of this method is however, if
it is done with air it leaves a mixture that is mostly nitrogen.

It can also be made by reacting water, in the form of steam, with carbon and the product of this reaction is called ‘water gas’ or ‘synthesis gas’.

Applications
CO is a major industrial gas that has an array of different applications in the diverse field of bulk chemicals manufacturing.

This chemically-complementing gas is a reducing agent in blast furnaces and is used in the purification of metals, as well as in the production of acetic acid, formic acid, methyl formate, Dimethylformamide, acrylic acid, propanoic acid and phosgene.

A large variety of chemicals, ranging from saturated hydrocarbons to oxygenated compounds such as methanol, are produced using CO.

Syngas, a mixture of CO and hydrogen produced by partial combustion of carbon or hydrocarbons, is used as a starting material for a variety of processes – not to mention for industrial power.

CO is a very important industrial compound. In the form of producer gas or water gas, it is widely used as a fuel in industrial operations, while it is also an effective reducing agent.

In another application, a mixture of metallic ores is heated to 50–80°C in the presence of producer gas. All oxides except those of nickel are reduced to their metallic state, as a way of separating nickel from other metals with which it can commonly occur.

New plants
A whole host of new CO plant capacity is set to come on-stream in the near future, catering for what is clearly a healthy demand.

Saudi International Petrochemicals Co.’s new carbon monoxide plant is due to be operational in April 2009. The plant will be run with technology from Lurgi and Air Liquide and at the time of our going to press, almost 99% of the work has been completed.

Yangzi Petrochem-Air Products has completed the manufacturing of a world-scale CO coldbox at its cryogenic equipment manufacturing facility in Caojing in January 2009.

It is the largest CO coldbox and the largest workshop-built CO coldbox that Air Products has ever constructed for its customers globally, producing over 300,000 tonnes per year of CO.

Meanwhile, Air Liquide is undergoing the renewal and expansion of its agreements with The Dow Chemical Company (Dow) and CUF in Estarreja, 50km south of Porto, in Portugal.

The project involves production of around 4,000 Nm3/hour of CO.