2017 Volume 60 Issue 2 Pages 95-100
The Fischer-Tropsch synthesis (FTS) was conducted for active-carbon-supported iron catalysts in a slurry-phase reactor. Heat treatment of the active carbon support in N2 resulted in some improvement in catalytic durability. However, ozone (O3) treatment of the support greatly improved catalytic durability. The optimum treatment temperature was found to be 400 °C. X-ray diffraction measurements and N2 adsorption analysis revealed that the structure of the active carbon support did not change drastically by the O3 treatment but the average pore size and mesopore volume increased to 1.3 times of those of the untreated support. This suggests that O3 removes a part of the amorphous carbon phase, thereby enlarging the pores to some extent. The major reason for catalyst deactivation was assumed to be the blocking of active sites by waxy products that formed. The enlarged pores facilitated solvent extraction from heavier products and thus promoted the maintenance of high catalyst activity. The product distribution obtained from the O3-treated catalyst exhibited a higher proportion of low-carbon-number products, thereby indicating suppression of secondary chain growth.
