(73f) Cobalt Catalyst Development For Fisher Tropsch Synthesis

Nafees, A., The Petroleum Institute
Al Hashimi, S. H., The Petroleum Institute

Commercially Fischer Tropsch (F-T) synthesis uses cobalt and iron catalyst to produce, hydrocarbons, oxygenates and chemicals including unrefined gasoline, diesel and wax ranges. Cobalt based catalyst have the advantage of higher conversion rate and a longer life. Theses catalysts are in general more reactive for hydrogenation and produce therefore less unsaturated hydrocarbons and alcohols compared to iron catalyst. The cobalt catalyst was firstly discovered in early 1920s. As soon as it was demonstrated that cobalt catalyst is the best suitable catalyst for F-T synthesis, commercial cobalt based processes were developed. From 1950s until late 1980s, iron based F-T processes dominated both industrial and R&D level area. Resulting in only marginal advancement in cobalt based process and technologies. Starting early 1990s, development of cobalt based technologies again gathered momentum.

Over the years, as a result of improvement in catalyst design technology, the performance and selectivity of the cobalt catalyst has been improved many folds. It has been demonstrated that that the activity and selectivity of cobalt based F-T synthesis catalyst can be influenced by the nature of the support (composition, pore size etc) and the type of the promoter. The idea of using composite catalyst (mixture of a classical F-T catalyst and a co-catalyst) is relatively newer. It has been shown that these catalysts have superior performance. However, the effect of physical mixing of catalyst and an adsorbent on catalytic activity and selectivity of the mixed catalysts is not well understood. One of the recent studies find that physical mixture of cobalt catalyst and an adsorbent separated by a wire mesh can significantly improve the performance. The authors are currently investigating the effect of different adsorbent parameters (catalyst/adsorbent ratio, pore size etc) on the selectivity/activity of the F-T synthesis. This manuscript reviews the historical development and present status of the cobalt catalyst for F-T synthesis.