What is the difference between carbon monoxide and carbon dioxide poisoning of ammonia synthesis catalysts?
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In the ammonia synthesis reaction, carbon monoxide and carbon dioxide may exceed the standard. Please tell me, what are the phenomena of these two substances after they enter the synthesis tower? How is the approach different?
3 carbon dioxide: It reacts chemically with the K2O present in the catalyst, changing the chemical properties of the catalyst. And react with ammonia to form salts such as ammonium carbamate or ammonium bicarbonate, which will cause blockage of equipment and pipelines. It also undergoes a methanation reaction (CO2+4H2 CH4+2H2O), consuming hydrogen and converting it into methane and water vapor, and water vapor is a poison. 4 carbon monoxide: It is the most common poison in ammonia synthesis gas and is also more harmful. It consumes hydrogen through the methanation reaction (CO+3H2 CH4+H2O) and is converted into methane and water vapor, and water vapor is a poison. Part of the CO will be stably adsorbed in the active center, reducing the activity of the catalyst. Poisoning reactions are all strong exothermic reactions, so when the catalyst is poisoned, it will cause a temporary temperature rise of the upper catalyst. After the catalyst activity is reduced or deactivated, the temperature of the upper layer drops sharply. Because the upper catalyst is deactivated, a large amount of hydrogen and nitrogen that has not reached the reaction equilibrium enters the lower layer, causing the reaction heat of the lower layer to increase, the temperature to rise, the hot spot to move downward, and the temperature line on the paper recorder to "cross". This is very different from the drop in bed temperature caused by high or low hydrogen-to-nitrogen ratio, excessive methane content, liquid ammonia, high ammonia cooling temperature, large reduction, excessive air speed, excessive opening of the tower auxiliary line, etc. This is also an important basis for judging catalyst poisoning. Although temporary poisoning can be recovered, it will always cause a certain amount of permanent poisoning. If it accumulates for a long time and is poisoned repeatedly, temporary poisoning can become permanent poisoning.
Here are some links from forums about ammonia synthesis catalyst poisoning for your reference. http://bbs.hcbbs.com/viewthread.php?tid=529107&highlight=%D6%D0%B6%BE http://bbs.hcbbs.com/viewthread.php?tid=309499&highlight=%D6%D0%B6%BE http://bbs.hcbbs.com/viewthread.php?tid=386396&highlight=%D6%D0%B6%BE http://bbs.hcbbs.com/viewthread.php?tid=389243&highlight=%D6%D0%B6%BE http://bbs.hcbbs.com/viewthread.php?tid=297958&highlight=%D6%D0%B6%BE
The second floor’s point of view is very correct. I agree with the second floor’s point of view.
What 2 said is very reasonable. In addition, carbon monoxide can also react with the alumina in the catalyst, thus causing the performance of the catalyst to decrease.
This post was last edited by Chemical Gas Purification on 2010-12-8 14:45 CO+3H2 =CH4+H2O (water vapor) CO2+4H2= CH4+2H2O (water vapor) Water vapor reacts with Fe ions in the catalyst: H2O+Fe= Fe O+H2 3H2O+Fe= Fe2 O3+3H2 It can be seen that the presence of CO and CO2 will reduce the catalyst activity, the catalyst bed temperature will decrease, and the system pressure will increase. Catalyst poisoning occurs. CO2 can also form crystals with ammonia and other substances in the system, causing blockage of pipelines and equipment. This is the difference between poisoning.