Temperature-programmed desorption/pulse surface reaction (tpd/tpsr) studies of CH ₄ , C ₂ H ₆ , C ₂ H ₄ , and CO over a cobalt/MWNTs catalyst

Summary

Temperature-programmed desorption (TPD) of CH₄, C₂H₆, C₂H₄, and CO and temperature-programmed pulse surface reactions (TPSR) of CH₄, C₂H₆, C₂H₄, CO, and CO/H₂ over a Co/MWNTs catalyst have been investigated. The TPD results indicated that CH₄ and C₂H₆ mainly exist as physisorbed species on the Co/MWNTs catalyst surface, whilst C₂H₄ and CO exist as both physisorbed and chemisorbed species. The TPSR results indicated that CH₄ and C₂H₆ do not undergo reaction between room temperature and 450^oC. Pulsed C₂H₄ can be transformed into CH₄ at 400 ^oC whilst pulsed CO can be transformed into CO₂ at 100 or 150^oC. In gaseous mixtures of CO and H₂ containing excess CO, the products of pulsed reaction were CH₃CHO and CH₃OH. When the ratio of CO and H₂ was 1:2, pulsed CO and H₂ were transformed into CH₃CHO, CH₃OH and CH₄. In H₂ gas flow, pulsed CO was transformed into a mixture of CH₃CHO and CH₄ between 200 and 250^oC and was transformed into CH₄ only above 250^oC.