abstracts - Институт катализа им. Г.К. Борескова

OP-I-19SR and DR was carried out at atmospheric pressure, contact times 1-6 ms and temperatures inthe range of 550-900 o C in a plug-flow quartz reactor. The catalysts were pretreated in situ at700-900 o C for 1 h in the oxygen or hydrogen flow. After pretreatment, the reaction mixture of adesired composition was supplied with the flow rate of 5.5-36 l/h i.e. at 0.7-6 ms contact time.The data of POM TPR show that the dynamics of CH 4 and O 2 consumption and productevolution strongly depends upon the catalyst composition (Fig. 1) and catalyst pretreatment.Concentration, %1.61.20.80.40.0LaNi (O 2)400 800 880 880Temperature, O CH 2CH 4O 2COH 2O CO 2870 Isothermconcentration, %1.5 LaNiPt (O 2)1.00.50.0CH 4COO 2H 2OCO 2740H 2635 680Isotherm 70 min800 880 880Temperature, O CFig. 1. Data of temperature-programmed reaction POM over channel of oxidized catalystsLaNiO x /CeO 2 -ZrO 2 /α-Al 2 O 3 and LaNiPtO x /CeO 2 -ZrO 2 /α-Al 2 O 3 .The addition of Pt facilitates the formation of syngas at lower temperature and favors ahigh catalyst stability preventing catalyst coking. For Pt-containing catalyst, after allpretreatment types, syngas evolution starts at temperature about 140-150 ºC below that forpure oxides containing samples. Pre-reduction of the catalysts with hydrogen or methanedecreases the temperature of syngas evolution. Over oxidized catalyst, H 2 O evolutionfollowed by CO 2 appearance in the presence of oxygen in the gas phase is observed. Thismeans that pyrolysis of CH 4 can proceed over both metal nickel (Pt) particles and partiallyoxidized Ni or Ni-Pt clusters.According to the steady-state data, the conversion of reactants and products selectivityincrease with the temperature and the channel length. For both catalysts with and without Pt,at 1-12 % CH 4 , at all temperatures, the conversion of methane is significantly lower than theequilibrium value. The oxygen conversion is incomplete only for experiments with the dilutedfeeds containing 1-3.5 % CH 4 at contact time ∼ 2 ms and temperature below 650 o C.Comparison of activity of the catalysts with Pt and without it reveals that the methaneconversion and product selectivity (Fig. 2) are better for the catalyst without Pt. Decline of116