Cobalt FT catalyst

The oxidation of cobalt metal to inactive cobalt oxide by product water has long been postulated to be a major cause of deactivation of supported cobalt FTS catalysts.6 10 Recent work has shown that the oxidation of cobalt metal to the inactive cobalt oxide phase can be prevented by the correct tailoring of the ratio Ph2cJPh2 and the cobalt crystallite size.11 Using a combination of model systems, industrial catalyst, and thermodynamic calculations, it was concluded that Co crystallites > 6 nm will not undergo any oxidation during realistic FTS, i.e., Pi[,()/I)i,2 = 1-1.5.11-14 Deactivation may also result from the formation of inactive cobalt support compounds (e.g., aluminate). Cobalt aluminate formation, which likely proceeds via the reaction of CoO with the support, is thermodynamically favorable but kinetically restricted under typical FTS conditions.6... 

Examples of Various Carbon Species on Cobalt FTS Catalysts along with Their Hydrogenation Temperatures... 

MINIMIZATION OF CARBON DEPOSITS ON COBALT FTS CATALYSTS BY PROMOTION... 

Additives such as rare earth or noble metals are generally introduced into industrial cobalt FTS catalysts as structural or reduction promoters.92 The addition of various promoters to cobalt catalysts has also been shown to decrease the amount of carbon produced during the FTS.84 87 93 94 Also, the addition of promoter elements may decrease the temperature of regeneration, preventing the possible sintering of supported cobalt particles during such treatments.92... 

The Presence of Various Carbon Species in Supported Cobalt FTS Catalysts as Operated under Realistic FTS Conditions (200-240°C, 10-40 bar, H2/CO = 1-2)... 

Olefin-hydroformylation on Cobalt-FT-catalysts in 1938 Head of Research at the Ruhrchemie company until 1962 Early co-worker of Franz Fischer... 

Cobalt- rather than iron-based FT catalysts have been examined, in order to minimize the competing water-gas shift reaction, which would result in a lowered carbon efficiency. Most cobalt FT catalysts have been prepared by coprecipitation of Co salts with various promoters onto a slurried oxide support to afford mixed phase systems (J ). Reduction to the active catalyst was controlled by addition of various promoters (e.g. MgO, Th02, AI2O3) (2). In part, these promoters are necessary to maintain good metal dispersion in the catalyst and resistance to sintering. Dispersion... 

We have recently studied the effect of water on the cobalt FT catalysts [2]. Water is the major oxygen containing product in Fischer-Tropsch synthesis (FTS), and in certain reactor types (e.g. backmixed slxnrry reactors) the concentration of water will be high and this can influence the catalyst surface. Water can deactivate the catalyst, and we have shown that this is mainly due to a surface reoxidation of cobalt. 

Shell has been involved in syngas chemistry for many years, giving special attention to the options for the conversion of natural gas into more easily transportable liquid hydrocarbons. The first result of this effort has been the Shell Middle Distillate Synthesis (SMDS) plant commissioned in Malaysia in 1993. This plant makes use of cobalt FT catalyst and tubular reactors in the Heavy Paraffin Synthesis unit (HPS). A simplified flow scheme of this plant is presented in Figure 7. 

The cobalt FT catalyst, key for performance in the early years, is being revived as the catalyst of choice for the LIFT GTL projects under consideration. 

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