Effect of introduced zeolite on the Fischer–Tropsch synthesis over a cobalt catalyst

Cobalt hybrid catalysts in Fischer-Tropsch synthesis

Currently, cobalt and zeolites are used in Fischer-Tropsch synthesis (FTS) to produce gasoline-range hydrocarbons (GRHs) that constitute clean and environmentally friendly fuels. This technology has earned a great deal of attention from researchers across the world, as it provides a substitute for fuel derived from fossil crudes, which have hitherto been the sole source of the petrol and diesel required by the industry. However, owing to the depletion of the earth’s oil and coal reserves and the unfavourable environmental impact of conventional fuel production, an alternative source of fuel is needed. This article provides a critical review of the technological challenges involved in producing middle isoparaffins and olefins (gasoline hydrocarbons) by FTS. These involve combining cobalt-based catalysts and zeolites to form hybrid catalysts. In this review, we address most of these by setting out each method of creating cobalt and zeolite hybrid catalysts in turn, so that researchers can identify which applications are most effective for producing GRHs.

Cooperative effect of cobalt and zeolite in controlling activity and stability of a catalytic Fischer–Tropsch process

The use of zeolites in Co-catalysts of Fischer–Tropsch synthesis (FTS) results in cooperative effect in the form of sudden increase of the zeolite activity in catalysing secondary transformations of FTS-generated hydrocarbons at unusually low temperatures in the range of 170–260 °C. In addition, hydrophobic zeolites in H-form allow changing the hydrophobicity of the pore walls and influence capillary condensation phenomena for intermediate species. The most unexpected effect of Co and hydrophobic zeolites is the improvement of degradation behaviour of the catalysts due to involvement of FTS-generated water into formation of additional Bronsted centres thus preventing undesirable oxidation of heat-conductive metal additives and other water-induced degradation processes. In addition, the stability of catalyst behaviour and its lifetime increase.