Acetonitrile synthesis over potassium-promoted, supported iron catalysts

Abstract

Listen

Translate article

Potassium promotion of iron on high surface area carbon catalysts increases the selectivity for direct acetonitrile synthesis from CO, H 2, and NH 3 at temperatures of 673–723 K and atmospheric pressure. Catalyst wafers prereduced in hydrogen at 673 K were quenched from reaction in situ to room temperature or 77 K for Mössbauer analysis. The spectra show reversible formation of small ε'-iron carbide panicles at short reaction times followed by sintering of the ε' phase and partial conversion to χ-carbide as the activity and selectivity decrease to a steady value. Catalysts prereduced only to the Fe 2+ state by hydrogen treatment at 473 K grow to a steady rate higher than that of catalysts prereduced at 673 K, but do not reach the value of the high rate maximum of those catalysts. These results are consistent with assignment of εe' carbide as the primary active phase, but imply that the development of effective surface area of this phase during reaction depends on its relative rates of production and sintering.