Dry Reforming of Methane over Ni-Based Pyrochlore Catalysts Using Transient Pulsing

Dry reforming of methane requires temperatures of 750 – 950 °C to achieve near equilibrium conversions. A thermally robust and active catalyst, such as Ni-substituted La₂Zr₂O₇ pyrochlore is desirable to achieve long term synthesis gas production. 

Here, we report pulsing experiments in which 10% CH₄/He flows over a pre-reduced catalyst continuously while pulses of 10% CO₂/He was switched with pure helium gas. The products were quantified using an in-line quadrupole mass spectrometer.

The results at 750 °C show the deactivation of the catalyst during the first pulse, but in the subsequent pulses the catalyst is found to be stable. At 800 °C and 850 °C, the CO concentration decreases during each CO₂ pulse. However, the catalyst activity was found to be increasing from its initial value before start of each pulse, which corresponds to an increase in the reaction rate of the CO₂-consuming reaction(s). Carbon, formed during the times only CH₄ flows, reacts with CO₂ to produce CO. At the higher temperatures, the reaction is faster, producing more CO and consuming the carbon faster.