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Garbis, Panagiota Katherina ; Jess, Andreas:
Selective methanation of CO over Ru-yAl2O3 catalyst.
2018
Veranstaltung: Jahrestreffen Reaktionstechnik 2018
, 07.-09.05.2018
, Würzburg.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung
,
Poster
)
Abstract
The worlds shift to alternative forms of energy production leads to home designs which are independent from electricity prices and reduce CO2 emission. In the recent years, the interest in the development of proton exchange membrane fuel cells (PEMFC) in stationary application increased. The potential of PEMFC is the combined heat and power supply of households with natural gas or, as a perspective, biogas as energy source for a clean and renewable solution to help achieve the world’s increasing energy demand and also reduce CO2 emissions. The compound CO is undesirable in the PEMFC operating gas because of the PEM fuel cell degradation by poisoning of the hydrogen oxidation reaction occurring at the anode of the fuel cell [1, 2]. Avoiding the degradation of the fuel cell, the CO content must be reduced to a value lower than 10 ppm [2–4]. A way to achieve this reduction of CO, as required in the fuel cell applications, is the selective methanation of CO. For this purpose, in-house manufactured catalysts supported on Al2O3 were used in experiments for the examination of their activity and selectivity in the CO methanation.
Experimental part and discussion
A number of catalysts were synthesized and examined in the CO selective methanation with semi realistic reformate gas concentrations of CO, CO2 and H2. Catalysts were prepared by wet impregnation of Rutheniumnitrosylnitrate Ru(NO)(NO3)3 (1.5% Ru), cobalt (II) nitrate hexahydrate and manganese (II) nitrate on γ-Al2O3 spheres with a diameter of 2.5 mm. A Ru on Al2O3 catalyst was also impregnated with NH4Cl for a better reaction selectivity. After a reduction in 10 vol% H2 in N2 atmosphere at 350 °C, the catalysts were first examined in the methanation of CO and CO2.
Therefore a plant was set up, consisting of a steel tube heated by an oil heating system as fixed bed reactor. Two thermocouples in a guide tube were positioned in the catalyst bed to monitor the reaction temperature. The inlet gases are CO, CO2, H2 and H2O balanced with N2. The gas composition (CO, CO2, H2 and CH4) leaving the reactor is measured by a gas analyzer (X-STREAM Enhanced Process Gas Analyzer, Emerson). Measurements were conducted at 180 – 300 °C and 1 bar.
Although the 2 wt% Ru with 1.3 wt% Cl on Al2O3 catalyst showed the highest selectivity, the catalyst is unsuitable for the claimed goal. It has been proven that the chlorine component is discharged from the catalyst surface by the gas stream and thus would poison the catalyst in the PEMFC. The best suited catalyst was a 2 wt% Ru supported on Al2O3 catalyst which will be used for further investigation. The reaction kinetics of this system were investigated. It is proven that in a CO/H2 reaction system, the CO inhibits the reaction. A kinetic model of the system of CO/H2 and CO2/H2 as well as for the selective methanation of CO will be presented on the conference poster.