Coke formation from carbon monoxide

Klouz investigated ethanol steam reforming and autothermal reforming over a nickel/copper catalyst on a silica carrier in the temperature range between 300 and 600 °C [197]. While the catalyst suffered from coke formation under steam reforming conditions, the addition of oxygen to the feed reduced both coke formation and carbon monoxide selectivity. By-products such as ethylene and acetaldehyde were not reported by these workers. 

In addition to coke formation and formation of carbon monoxide, the most familiar by-product is methane, which may be formed from carbon monoxide via the mefhanation reaction ... 

Coke formation may also originate from carbon monoxide reacting with hydrogen to produce carbon and steam [see Eq. (3.20) in Section 3.2]. 

A feed of 100 Ncm3 min-1 methane and 50 Ncm3 min-1 oxygen was introduced into the reactor at a pressure loss of < 2.5 mbar. The residence time of the reaction was 50 ms. 60% conversion was achieved along with a high carbon monoxide selectivity of 70% at 700 °C reaction temperature. Owing to the short residence times applied, no coke formation was observed and carbon monoxide selectivity was higher than expected from the thermodynamic equilibrium [46],... 

Anthony and Singh concluded from a kinetic analysis of the methanol conversion to low molecular weight olefins on chabazite that propylene, methane, and propane are produced by primary reactions and do not participate in any secondary reactions, whereas dimethylether, carbon monoxide, and ethane do. Ethylene and carbon dioxide appear to be produced by secondary reactions. It was also shown that the product selectivities could be correlated to the methanol conversion even though the selectivity and the conversion changed with increasing time on stream due to deactivation by coke formation. 

Several gaseous components present during most commercial pyrolysis runs react with or at the surface. For example, hydrogen reduces the surface oxides (6), desulfurizes coke (7), and reacts with the coke Itself to produce methane (8). Cleaning coke from the surface may act to promote more coke fonnatlon, but reduction of surface oxides presumably often decreases the rate of coke formation. Carbon monoxide also Is a reducing agent for metal oxides and Is sometimes employed during the manufacture of steel. 

An obvious advantage of partial oxidation is that only an air feed is required, apart from the fuel. This makes the system simpler because evaporation processes, as required for steam reforming, are avoided. On the other hand, the amount of carbon monoxide formed is considerably higher compared with steam reforming. This puts an additional load onto the subsequent clean-up equipment, but only where CO-sensitive fuel cells are cormected to the fuel processor. When fuels are converted by partial oxidation, some total oxidation usually takes place as an undesired side reaction [46]. In practical applications, an excess of air is fed to the system and consequently even more fuel is subject to total oxidation. The water formed by the combustion process in turn gives rise to some water-gas shift. Another typical byproduct of partial oxidation is methane, which is formed according to reaction (3.5). Coke formation is a critical issue (see Sections 4.1.1 and 4.2.11). Coke may be formed by reaction of carbon monoxide with hydrogen ... 

Fuel Cell and Fuel Processor Catalyst Tolerance There are major fuel requirements for the gas reformates that must be addressed. These requirements result from the effects of sulfur, carbon monoxide, and carbon deposition on the fuel cell catalyst. The activity of catalysts for steam reforming and autothermal reforming can be affected by sulfur poisoning and coke formation this commonly occurs with most fuels used in fuel cells of present interest. Other fuel constituents can also prove detrimental to various fuel cells. Examples of these are halides, hydrogen chloride, and ammonia. 

The eponymous blast of a blast furnace is a blast of air. It may seem odd to use oxygen-rich air in a process designed to remove oxygen from an ore, but it is used to oxidize the carbon to carbon monoxide and also to help ensure that the contents of the furnace do not settle to the bottom. Care must be taken, of course, to ensure that the blast is not so strong that the contents are blown out through the top A gas such as carbon monoxide is much more fleet of molecular foot than lumps of coke and can penetrate into and attack the molten ore wherever it lies. The partial combustion of the coke—for that is what the formation of CO represents— also serves to raise the temperature within the furnace and render the ore molten. 

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