Abstract
Pre-treating the multi-walled carbon nanotubes (CNTs) support by refluxing in 35 vol% nitric acid followed by heating at the temperature of 600 to 900 °C resulted in the formation of defects on the CNTs. Increasing the temperature of the pre-treatment of the CNTs from 600 °C to 900 °C, enhanced the fraction of cobalt-oxide nanoparticles encapsulated in the channels of CNTs from 31% to 70%. The performance of Co/CNTs in Fischer-Tropsch synthesis (FTS) was evaluated in a fixed-bed micro-reactor at a temperature of 240 °C and a pressure of 2.0 MPa. The highest CO conversion obtained over Co/CNTs.A.900 was 59% and it dropped by ~3% after 130 h of time-on-stream. However, maximum CO conversion using Co/CNTs.A.600 catalysts was 28% and it decreased rapidly by about 54% after 130 h of time-on-stream. These findings show that the combined acid and thermal pre-treatment of CNTs support at 900 °C has improved the stability and activity of the Co/CNTs catalyst in FTS.
Highlights
Recent developments on the applications of Co-based catalyst on carbon materials support in Fischer-Tropsch synthesis (FTS) have been reviewed by Mark E Dry [1] where a new option and challenges in catalysis for the Fischer-Tropsch Synthesis (FTS) have been highlighted
After metal loading on the pre-treated carbon nanotubes (CNTs) at 600 ◦ C, via strong electrostatic adsorption (SEA) method, the BET surface area and total pore volume decreased to 207.8 m2 ·g−1 and 0.50 cm3 ·g−1, respectively
Co catalyst was prepared on treated CNTs support using SEA method
Summary
Recent developments on the applications of Co-based catalyst on carbon materials support in Fischer-Tropsch synthesis (FTS) have been reviewed by Mark E Dry [1] where a new option and challenges in catalysis for the Fischer-Tropsch Synthesis (FTS) have been highlighted. We used the same approach of combined acid and thermal pre-treatments of CNTs as that of Tavasoli et al [10] but we applied the strong electrostatic adsorption (SEA) method to prepare the Co/CNTs catalyst where the pH of the precursor solution was controlled during the metal deposition. Schwarz suggested that the electrostatic forces between a metallic ion and a charged support could be utilized for direct adsorption of the metallic ion over surfaces including two oxide fractions [11,12] The idea behind this method has been efficiently applied to make highly dispersed, monometallic catalysts on a multitude of oxide and carbon supports [13,14,15]. We have established that the combined acid and thermal pre-treatments of CNTs at 900 ◦ C improved the activity and stability of the Co/CNTs catalyst in FTS
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