Catalytic decomposition of methane over cerium-doped Ni catalysts
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0885-A09-49.1
Catalytic decomposition of methane over cerium-doped Ni catalysts Oscar A. González, Miguel A.Valenzuela*, Jin-An Wang Lab.Catálisis y Materiales. ESIQIE-IPN. Zacatenco, 07738, México D.F. MEXICO.
ABSTRACT Si-Ce-O mixed solids (50, 30, 10 and 5, Si/Ce molar ratio) were prepared by using Ce(NO3)3·6H2O as cerium source, tetraethyl orthosilicate (TEOS) as Si precursor and cetyltrimethylammonium bromide (CTABr) as synthesis template. The Ni catalysts were prepared by impregnation of the supports using Ni-acetilacetonate (30 wt.% Ni) as Ni source. The samples were characterized by: X-ray diffraction, temperatureprogrammed reduction (TPR), and TEM. The nickel reduction degree decreased with the addition of cerium, even in low concentration. When methane was decomposed over all the catalysts only hydrogen was obtained as a gaseous product. The addition of cerium brought about a significant increase in stability compared with Ni/SiO2 catalyst. These preliminary results indicated that CeO2 addition improves the dispersion of Ni particles leading to a better distribution of deposited carbon and increasing the lifetime of Ni particles.
INTRODUCTION The demand for hydrogen is ever increasing due to its use in chemical processing, electronics, food processing, metal manufacturing and fuel cells [1]. Hydrogen production, from water-splitting by using solar light or other renewable energy sources, is not competitive from an economical point of view [2]. Therefore, in the near future hydrogen production will continue to depend on fossil fuels, mainly natural gas [3]. Commonly, most of the industrial hydrogen production is based on the steam reforming process which is a source of significant CO2 emissions into the atmosphere [4].Catalytic partial oxidation and autothermal reforming combined with CO2-sequestration are alternatives to the conventional steam reforming process [5]. The catalytic decomposition of methane (CDM) can be used to obtain COx-free hydrogen and has become an interesting research topic recently [6-12]. It produces pure hydrogen and carbon and there is no necessity for the separation of hydrogen from other gases, such as COx in the conventional processes.The most studied catalysts for the CDM are nickel supported on: SiO2, TiO2, graphite, ZrO2, SiO2-Al2O3, Al2O3, MgOSiO2, MgO and ZnAl2O4 among others [6-12]. The activity and life of the supported Ni catalysts for CDM strongly depend on the particle size of Ni metal and the textural properties of the support [8]. Unfortunately, rapid deactivation of Ni-based catalyst results at temperatures in excess of 600°C, leading to a low yield of hydrogen [12]. On the other hand, it is well known that the surfactant-assisted (SA) route provides finely tuned pore sizes, high surface areas and enhanced accessibility of the active surface sites [13-14]. It is, therefore, a major challenge to develop a catalytic system that sustains its activity at high temperatures. In the present work, we focus our attention to the synthesis method and characterization (XRD, TP
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