The reactivity and initial carbonization of an Unsupported Nickel catalyst in dry reforming of methane

High speed product gas analysis during the dry reforming of CH4 allows the observation of transient elevated H2 and CO production rates, combined with high initial conversions of CH4 and CO2. The transients are observed in the first 120 s of the reaction, followed by a lower steady-state production rate after 3–5 min. The catalytic reactivity in the initial 120 s is important in understanding the catalyst performance and determining the reactions responsible for carbon deposition. Monitoring the changes in the H2 and CH4 partial pressures from the start, through the transient production regime, and on through the steady-state regime, shows that the transient reactivity is directly related to the decomposition of CH4. This finding is further supported by the linear trend found between the H2/CO ratio and the carbon deposition in the peak region of the product gas profile. Although significant amounts of carbon are deposited on the Ni surface, it is not completely deactivated at any of the reaction temperatures in the 500–800 °C range explored herein. Characterizing the initial reactivity in terms of carbon deposition and catalyst performance in dry reforming of CH4 may lead to changes in the sampling technique for researchers working with reforming reactions, and optimized catalysts that exhibit reduced initial carbon deposition. •We have quantified the initial carbonization of Ni catalysts during dry reforming.•Initial deactivation is due to methane decomposition.•Steady state reforming kinetics are found within 5 min of operation.•Deactivation is dominant for temperatures below ~700 °C.