90.
The effect of CO
2 was studied for cobalt and iron Fischer–Tropsch (FT) synthesis. CO
2 behaves differently in the presence of CO over cobalt and iron catalysts in terms of hydrogenation. A systematic increase of the CO
2 mole fraction of carbon in the feed gas mixture alters the product distribution dramatically for cobalt FT synthesis with CO
2 behaving like an inert gas at higher partial pressure of CO. With cobalt, CO appears to compete with CO
2 for adsorption. Using an iron FT catalyst, hydrogenation of CO
2 was effected due to the presence of the reverse water–gas shift activity of the catalyst which converts CO
2 to hydrocarbons through the formation of CO. Unlike the cobalt catalyst, the product distribution was only slightly altered with increasing CO
2 content in the feed gas mixture to the iron catalyst. This difference in behavior of CO
2 over cobalt and iron could be attributed to the absence of reverse water–gas shift activity on cobalt and hydrogenation of CO
2 to hydrocarbons—other than methane—will be derived through the formation of CO.
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