What is methanation？

What is methanation？

Methanation reaction is actually the reverse reaction of methane steam conversion. In principle, the nickel catalyst used for steam conversion is also active to methanation reaction.However, the chemical sequence of methane is between decarbonization and compression, so it is better to choose the catalyst with low reaction temperature, so as not to waste energy by repeatedly rising and cooling. So methanation catalyst should have good low temperature activity;At the same time, due to the very strict requirements of gas purification (up to several ppm), the catalyst is required to have high activity, high thermal stability, high mechanical strength, good toxicity resistance, good selectivity.High activity is because the residual content of carbon oxide required by the process is very low. High thermal stability ensures that the catalyst can withstand large temperature fluctuations. Good toxicity resistance enables the catalyst to be corroded by impurities such as sulfur, arsenic and chlorine, which can better maintain its activity and prevent the toxicity from penetrating the bed and affecting the next process.Good selectivity can promote the smooth methanation reaction and reduce the occurrence of side reactions.High mechanical strength can ensure that the catalyst in abnormal conditions (such as pressure changes caused by jump, instantaneous temperature fluctuations, liquid, etc.) keep the particle integrity, avoid breakage or powder.

Over a certain concentration of CO and CO2 will cause subsequent ammonia synthesis catalyst (iron, due to the excessive content of oxygen compounds) poisoning.So CO2 and CO should be removed by certain methods.The following two reaction equations are the mechanism by which CO and CO2 are removed.The resulting methanation is harmless to ammonia synthesis catalysts.

CO+3H2=+H2O

CO2+4H2=CH4+2H2O