Studies of Transient Species Formed During Catalytic Reactions of CO2 + D2 and of 1-Butene

Transient species in a catalyzed reaction have been observed in the gas phase by placing the catalyst in a specially designed mass spectrometer ion source. The reaction, $${\mathrm{D}}_2+{\mathrm{CO}}_2\to {\displaystyle {lim}_{\mathrm{Pt}}}{\mathrm{D}}_2\mathrm{O}+\mathrm{CO},$$ was studied over a pressure range 0.1–1 mm Hg and a temperature range 50–1100°C to demonstrate the applicability of the techniques. A free radical, of molecular formula CDO, was shown to be formed by and desorbed from the Pt catalyst during the reaction. In addition, DCOO^— ions were observed suggesting the presence of an intermediate DCOOD on the catalyst. The production of the products CO and D₂O was not a monotonic function of catalyst temperature, but instead showed a maximum in the temperature range 400–500°C. The rate increased approximately as the first power of PCO₂ and was nearly independent of the partial pressure of D₂. The catalytic decomposition of butene‐1 was studied in the same way. Free radicals produced by the catalytic decomposition of this compound are compared to those known to occur from thermal decomposition at the same temperature. In the catalytic decomposition, the radicals C₄H₇ and C₃H₅ were found to be most abundant; in contrast, CH₃ and C₃H₅ are most abundant in the thermal decomposition.