Study of a nickel catalyst under conditions of the SER process: Influence of RedOx cycling

Sorption-enhanced reforming of bioethanol in dual fixed bed reactor for continuous hydrogen production

“…A standard commercial Ni based catalyst NIAP-03(OAO NIAP, Novomoskovsk Russia) containing 11 wt % of NiO was used in this work which was early studied at SER conditions [14]. Prior to use, sorbent and catalyst were crushed and sieved into particles of 1e2 mm size.…”

“…The stability of the supported Ni reforming catalysts in SER process was not so extensively studied; however, Ortiz and Harrison [13] reported that after 25 cycles the decay of catalytic activity was negligible. It was also shown that in model conditions without sorbent, continuous change of reduction and oxidation atmosphere partially prevents sintering of the Ni catalyst active component and stabilizes the activity at a higher level as compared with the conventional steady state reforming [14].…”

Steam Reforming of CH4 Using Ni- Substituted Pyrochlore Catalysts

“…Repeating redox cycling of the Ni particles will then lead to the dispersion and stabilization of some of the Ni into smaller, and more active crystals. Further evidence demonstrating the improvement in the activity of Ni through redox cycling is shown in a study by Lysikov et al [140] during the sorption-enhanced reforming (SER) of CH4 at different temperatures (650-900°C). Over a commercial Ni-based steam reforming catalyst, alternating pulses between steam/CH4, and O2 were found to sinter the Ni metal from 5-10 nm sized particles to 100-200 nm over temperatures of 650°C and 800°C.…”

“…Over a commercial Ni-based steam reforming catalyst, alternating pulses between steam/CH4, and O2 were found to sinter the Ni metal from 5-10 nm sized particles to 100-200 nm over temperatures of 650°C and 800°C. However, interestingly, at S/C ratios greater than 2.0, cycling the catalyst at 650°C saw a 10-fold decline in activity, whereas the high temperature studies saw the catalyst remain stable and active [140]. The behavior was explained by the importance of the levels of reducing H2 gas in the reactor, as well as the volume contraction which occurs during the reduction of Ni from NiO.…”

“…The almost instant decline in activity at the start of the experiment for all materials, and the accompanied particle growth ( Table 4- however, the fast reduction of the larger particles under the SMR reaction conditions creates a porous, sponge-like Ni metal particle with irregular (non-epitaxial) orientations of the lattice grains due to rapid oxygen removal from the particle [132,140]. While the Ni particle may become more porous, the size of the pores is likely sufficiently small (10-100nm [140]) to allow diffusion of H2…”