Exactly how the automotive industry will develop in the future, nobody can tell for sure. However, two things are certain: Alternative propulsion systems and fuels will play a greater role, although combustion engines will continue to dominate in the short to medium term. The question of alternative fuels and propulsion sometimes has a political dimension. 

There is no doubt that the discussion about alternative energy sources to replace ever more expensive crude oil continues. An important milestone in this direction was achieved by the invention of a method to exploit the by-products of oil production. CAC and Bergakademie Freiberg Technical University worked together to create a pilot plant to obtain high-quality gasoline from unused petroleum gases that are otherwise burned off when oil is stored.

Directly derived synthesis gas
With the new technology, the gas is directly turned into transportable and useable petrol right at the wellhead. It also reduces CO2 emissions, of which 100 to 150 million tonnes per year are currently generated worldwide by the combustion of this gas. In fact, the exploitation of crude oil associated gas in this manner could supply Germany's energy needs for a full year. A positive side-effect is environmental protection.

Unused Resources
In 2010, world annual production of natural gas including associated gas was around 4 trillion cubic metres. In addition to 483 billion cubic metres per year re-injected to maintain oil well pressure for production, a further 120 billion cubic metres per year are wasted, as the petroleum oil is either burned off, with resulting CO2 emissions, or directly blown off.

Removal of the associated gas by pipeline from remote deposit fields is not economically feasible. This offers on-site conversion into a liquid product, like synthetic fuels or chemical feedstock. This is equally interesting for countries with large amounts of natural gas but little or no oil. These large amounts of unused associated gas could in future be converted into high-quality petrol.

STF process in detail
"The conversion of petroleum gases into gasoline is called 'syngas-to-fuel' - STF for short. The STF process is a world technological first and is patented", says Dr. Mario Kuschel, Senior Process Engineer at CAC. The process is based on a novel combination of various process parameters.

What makes this process so unique is the heat transfer application design, in addition to the use of a specially developed catalyst. The synthetic gas, which contains CO and hydrogen, is first passed through a methanol synthesis process for which the newly developed isothermal reactor is used. The methanol is then removed in a separation step and treated in a subsequent gasoline synthesis process in which the methanol is converted to high octane, so very high quality, gasoline. This gasoline contains exactly the same level of octane as premium gasoline found at service stations. 

High-octane gasoline produced in this way is of Euro V classification standards and, in contrast to other methods, can be used without further post-processing - except for stabilisation of the gasoline fraction in a distillation column, no further post-processing steps are required. Non-reacted methanol and light hydrocarbons are separated in a subsequent separation step and recycled to the process.

Water vapour as energy carrier
In the newly developed reactors, heat produced by the exothermic reactions is utilised to produce steam, which is then used as energy carrier for the process. These isothermal reactors together with the newly developed catalysts guarantee a high level of efficiency and effectiveness.

In addition to associated gas, gasoline can also be produced from biomass or sometimes from coal. This exploitation of associated gases prevents its senseless burning and allows for a sustained reduction in CO2 emissions. In addition, methanol contained in the water produced as a by-product of the synthesis can be reused in the process after treatment. This new method thus makes a positive contribution to environmental protection. The prospects are promising: associated gases which inevitably occur during oil production can be used similar to the oil to produce petrol and contribute to mitigating the impending problem of dwindling oil reserves in the future. In theory, the technology will thus contribute to a sustainable energy supply in the long term.

Pilot plant in Freiberg
To prove its practicality, CAC commissioned a pilot plant in partnership with Bergakademie Freiberg Technical University.
In addition to the production of gasoline from synthesis gas, it should demonstrate that the process works and is very effective. The fact that unreacted materials, such as excess methanol or light hydrocarbons, are recycled and can be reused in the process contributes among other things to the high degree of efficiency. 

In June 2010, the plant produced the first batch of petrol from synthesis gas in a two-stage process with an established volume of 700 standard cubic metres of gas per hour. From this, partners CAC and Bergakademie TU were able to obtain 120 litres of fuel per hour. Currently, gasoline continues to be produced at the pilot plant in Freiberg - with increasingly purer final product. Dr. Mario Kuschel emphasises: "This process does surely not resolve the concerns about car use and fuels of the future. But it can make a valuable contribution, making driving affordable and environmentally sound in the future ".

For further information please visit #ACHEMA 2015 in Halle 9.1, Stand: B26