from first principles PP-I-1

OP-III-5Effect of Carbonization on Dry Methane Reforming over Ni CatalystsBychkov V.Yu., Tyulenin Yu.P., Firsova A.A., Korchak V.N.Semenov Institute of Chemical Physics RAS, Moscow, Russiabychkov@chph.ras.ruDry methane reforming (DMR) is a promising process of the production of synthesis gasusing CH 4 and CO 2 as initial reagents, and Ni-containing systems are the effective catalysts ofthis reaction. It is known that during the DMR reaction CH 4 decomposes on metal surfacegiving surface carbon, which is an intermediate in CO production, but also can be a poison ofthe DMR process [1, 2]. Carbonization of Ni catalysts is one the main problems of industrialapplication of dry methane reforming, but details of carbon state, formation and removalduring DMR are still not clear. In this study, carbonization of supported Ni catalysts wasinvestigated using thermogravimetry and mass-spectrometry. Samples containing Ni particlesof different sizes were prepared and a redox thermogravimentric method for determination ofNi particle size was proposed and applied to the samples. Accumulation and removal ofcarbon during interactions of the catalysts with CH 4 , CO 2 , H 2 , O 2 as well as CH 4 -CO 2mixtures were measured at temperature programmed and isothermal regimes.It was found that accumulation of carbon proceeds in CH 4 or CH 4 -CO 2 flow and the rate of Caccumulation depends on Ni particle size, nature of alumina support, gas phase composition,temperature and also, in some cases, a direction of temperature variation. Minimal Caccumulation was found for catalysts containing the smallest and biggest Ni particles, 2 and30 nm, respectively. It was shown that the catalyst with the large Ni particles 30 nm, due tolower carbonization and despite of lower area of Ni surface, demonstrated the same catalyticactivity as the samples with 2-5 nm Ni particles.The rate of C accumulation in Ni/Al 2 O 3 was maximal at 600-650°C. So, it was shown that ahigher catalytic activity at 700°C can be observed for the catalyst, which was not preheated inthe reaction mixture from the room temperature.Experiments on removal of accumulated carbon by CO 2 , H 2 and O 2 allowed to comparedifferent states of the carbon in the catalysts. In particular, it was shown that all carbonaccumulated in Ni/α-Al 2 O 3 can react with CO 2 giving CO, but only part of carbonaccumulated in Ni/γ-Al 2 O 3 is reactive with CO 2 .This work was supported by the Russian Foundation for Basic Research(grant no 10-03-00715).References:[1] M.C.J. Bradford, M.A. Vannice, Cat.Rev.Sci.Eng., 41(1) (1999) 1-42.[2] V.Yu. Bychkov, O.V. Krylov, V.N. Korchak, Kinetics and Catalysis, 43 (1) (2002) 86-94.48