Water decomposition conventional catalysts

For the higher molecular weight feedstocks such as liquefied petroleum gas (usually propane CjH8) and naphtha (q.v.), nickel catalysts with alkaline carriers or alkaline-free catalysts with magnesium oxide as additive can be used. Both types of catalyst are less active than the conventional nickel catalyst. Therefore, a less rapid decomposition of the hydrocarbons is achieved. At the same time, the reaction of water with any carbon formed is catalyzed. 

One of the most important variables in the TPD of CO from a supported Pt catalyst is the sample pretreatment. Calcination at 500°C for one hour followed by reduction is the conventional method to obtain the maximum exposed Pt and this follows closely to refinery practice for start-up and regeneration of commercial catalysts. The final step in our case was a 600°C He sweep for 30 minutes to ensure a fully dehydrated catalyst up to this temperature so that no water evolved during the subsequent TPD. We had previously observed that a high temperature He sweep could reduce the Pt catalyst without a prior H reduction presumably by the decomposition of the Pt oxide. 

Methane reforming Eq. (2.36) is the simplest example of steam reforming (SR). This reaction is endothermic at MCFC temperatures and over an active solid catalyst the product of the reaction in a conventional reforming reactor is dictated by the equilibrium of Eq. (2.36) and the water-gas shift (WGS) reaction Eq. (2.37). This means that the product gas from a reformer depends only by the inlet steam/ methane ratio (or more generally steam/carbon ratio) and the reaction temperature and pressure. Similar reaction can be written for other hydrocarbons such as natural gas, naphtha, purified gasoline, and diesel. In the case of reforming oxygenates such as ethanol [125, 126], the situation is in some way more complex, as other side reactions can occur. With simple hydrocarbons, like as methane, the formation of carbon by pyrolysis of the hydrocarbon or decomposition of carbon monoxide via the Boudouard reaction Eq. (2.38) is the only unwanted product. 

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