Cooking up remedies
global stocks of natural gas are enormous. Industry analysts estimate that the world holds enough recoverable natural gas to produce 500 billion barrels of synthetic crude. If this gas is converted into liquid form, it can provide fuel for nearly a decade after conventional supplies of crude oil begin to dwindle. These fuels would be mostly free from toxic pollutants such as sulphur, nitrogen and heavy metals. Although the conversion facilities are large and complex, advanced techniques have made it possible to produce liquid fuel economically ( Scientific American , Vol 278, No 3).
There are different techniques to convert natural gas into liquid fuel. However, all these methods address the same fundamental problem in chemistry: making larger hydrocarbon molecules from smaller ones. Methane, a simple molecule, is the main component of natural gas. It has four hydrogen atoms arrayed around one carbon atom. This symmetry makes methane particularly stable. Natural gas can be converted by breaking its chemical bonds. High temperatures and pressures help to break these bonds.
The indirect approach for converting natural gas to liquid form relies on irrational force. First, the chemical bonds in methane are broken using steam, heat and a nickel-based catalyst to produce a mixture of carbon monoxide and hydrogen known as syngas or synthesis gas. This process is called steam reforming.
The second step in the production of liquid fuels from syngas uses a method invented by Franz Fischer and Hans Tropsch. During World War ii , Germany harnessed this technique to produce liquid fuels using syngas made from coal and atmospheric oxygen, thus establishing a reliable internal source for gasoline and diesel.
This Fischer-Tropsch technology has helped produce liquid fuels commercially for decades using syngas derived from coal. In this process, syngas is blown over a catalyst made of cobalt or nickel that is transformed into liquid hydrocarbons. The Fischer-Tropsch reaction gives off heat, and often this heat is used to drive the oxygen compressors needed to make syngas.
Temperature is the key factor that decides which liquid would emerge out of the reaction. For example, running a reaction vessel at 330 to 350