OREANDA-NEWS. A recent TUT doctoral thesis examined, how to produce synthetic petroleum from oil shale in the most effective way.


Current industrial processes are oriented at the production of oil shale accompanied by high content of organic carbon in emissions and volatile matter.

In the second last week of May, Julia Krasulina defended her doctoral thesis "Upgrading of Liquid Products from Estonian Kukersite Oil Shale by Catalytical Hydrogenation" at TUT. The goal of the thesis was to elucidate the possibilities for more effective thermochemical upgrading of Estonian kukersite oil shale in order to obtain as the main product oil with possibly high yield and high content of hydrocarbons, which would be a synthetic analogue to natural petroleum.

Petroleum is primarily a mixture of hydrocarbons, but shale oil is also rich in heteroatoms, i.e oxygen, sulphur or nitrogen containing compounds. "Various oxygen compounds form up to two-thirds of the composition of Estonian oil shale," Hans Luik, Head of the Laboratory of Oil Shale and Renewables Research, who supervised the doctoral thesis, explains. If most of the oxygen, sulphur and nitrogen could be removed from oil shale in after-treatment, a hydrocarbon-rich product, i.e. synthetic petroleum could be obtained.

Essentially, this process means separation of the mineral matter from the organic matter. It is not just a question of separating organic matter, i.e. kerogen, as effectively as possible. In case of pyrolysis, i.e. retorting, applied currently in industry, organic matter is the only valuable product. As a result of the abovementioned process the mineral matter formed is environmentally hazardous semicoke, whereas as a result of the new process a neutral co-product suitable for future use is formed .

In order to achieve this, two processes need to be completed: at first the kerogen in the oil shale must be converted, as effectively as possible, into liquid substance, thermobitumen, and thereafter heteroatoms must be removed from it.

"As a result of the research, a new especially effective thermal dissolution method was worked out and optimized," Krasulina says. The yield of processes used for industrial applications falls within 40-45%, whereas by applying the new method, 86-91% of kerogen is transformed into an intermediate product with new composition – a mixture of incompletely decomposed oil, a mixture of thermobitumen and oil.

This is followed by purification of the intermediate product, for which catalytic hydrogenation, i.e. replacement of heteroatoms with hydrogen by using a catalyst, is the most suitable method. In case of optimum time, temperature, hydrogen pressure and catalyst type, up to 79 % of raffinate can be produced from kerogen. The result is outstanding - this yield is even higher than the amount of shale oil obtained by pyrolysis in Fischer Assay (66%).

However, this does not mean that domestic or foreign oil shale industries can apply the above-described process in the near future. "This is a fundamental research serving as a basis for applied research, which shall identify industrial applications," Luik stresses. The ultimate goal is certainly to develop a process for producing synthetic petroleum from oil shale, which is relatively unknown on the world market.