Effect of support composition on the origin and reactivity of carbon formed during dry reforming of methane over 5 wt% Ni/Ce1−xMxO2−δ (M = Zr4+, Pr3+) catalysts

摘要: Abstract Carbon dioxide reforming of methane to synthesis gas in the 550–750 °C range over 5 wt% Ni/Ce1−xMxO2−δ (M = Zr4+, Pr3+) solids has been investigated with respect effects support chemical composition and reaction temperature on amount, reactivity (towards H2 O2) relative contribution CH4 CO2 activation routes towards “carbon” formation. For these characterisation studies, various transient isothermal temperature-programmed oxidation (TPO) hydrogenation (TPH) experiments coupled use 13CO 13CO2 isotope gases were conducted. TPO following dry (5%13CO2/5%12CH4/45%Ar/45%He) demonstrated that amount kinds formed via was strongly dependent composition. At 550 °C, ratio 12CO2 12C-containing 13C-containing inactive 0.4, 0.27 0.19, whereas at 750 °C 1.07, 1.06 0.29, respectively, for Ni supported Ce0.8Zr0.2O2, Ce0.8Pr0.2O2 Ce0.5Zr0.5O2 carriers. The origin formation route illustrated be Boudouard (2CO-s → CO2(g) + C-s + s) through a isotopic experiment feed containing 12CH4. It also found CO-s derived from direct dissociation can lead number different which depends present Ni/Ce0.8Pr0.2O2 catalytic system exhibited conversion 84%, H2-yield 48%, H2/CO 1.04 after 50 h (20% CH4, 20% CO2, He; GHSV = 30,000 h−1) relatively low (17.5 mg C/gcat or 1.75 wt%) accumulated “carbon”. influence nickel particle size, turn influenced origin, kinetics deposition under conditions.