Partial oxidation of methane over Ni0/La2O3 bifunctional catalyst II: Global kinetics of methane total oxidation, dry reforming and partial oxidation

• The global Arrhenius equation was established for DR, TO and POM.
• Ea of DR, TO and POM were 87.8, 116.4 and 112.8 kJ mol−1, respectively.
• At 1073 K, kDR=69.3 {(mol m−3)1−α s−1}≫kTO=12.4 {(mol m−3)1−(γ+δ) s−1}kDR=69.3 {(mol m−3)1−α s−1}≫kTO=12.4 {(mol m−3)1−(γ+δ) s−1}; (kSR ≈ kDR).
• Methane TO reaction is the rate determining cycle (rdc) of POM reaction (rPOM0=2rTO0 with kPOM ≈ 2kTO).

The global kinetics (power rate law) of methane total oxidation (TO) over La2O3 catalyst was performed at 773, 823 and 873 K. The global kinetics of methane dry reforming (DR) at 648, 673, 698 and 723 K and partial oxidation (POM) at 993, 1013, 1023 and 1053 K were conducted over Ni0/La2O3 catalyst. The initial rate method and isolation method were used to determine initial rates, rate constants, and partial orders to reactants and establish the Arrhenius equations for TO, DR, POM. The experimental apparent activation energies were 87.8, 116.4 and 112.8 kJ mol−1 for DR, TO and POM, respectively. For TO, the reaction order to CH4 was varying with conversion whereas that to O2 was zero. For DR, the reaction order to CH4 was constant, whereas that to CO2 was dependent on the concentration of CO2. The values of rate constants revealed the following order: kDR ≫ kPOM, kTO. It was found that the rate constant of POM reaction is linked to that of methane TO: kPOM ≈ 2kTO. The catalytic cycle of methane TO is the “rate determining cycle” (rdc) of the POM process.

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