There are questions regarding nickel carbonyl in the methane synthesis process
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NI(CO)4: What are the conditions under which it is formed during the process? What is the mechanism that deactivates the catalyst?
When the reaction temperature exceeds the limit, nickel carbonyl is formed, and nickel loses its activity
Excessive reaction temperature does not cause the formation of nickel carbonyl； On the contrary, it is low temperatures that cause the formation of nickel carbonyl, especially in the temperature range of 210–230°C ；
3# In what form does NI(CO)4 exist after it is formed in this temperature range?
Carbon deposition occurs at high temperatures, while nickel carbonyl is formed at low temperatures.
The production of nickel carbonyl leads to the loss of the active components of the catalyst. Excessive temperature causes carbon buildup to cover the catalyst pores.
Thank you for the reply from the 6th floor. What form does nickel carbonyl exist in?
At low temperatures below 200 degrees and high CO pressures, nickel carbonyl is likely to form
Studies on carbon deposition in nickel-based catalysts during methanation reactions show that, especially when the CO concentration in the feed gas is high, the catalyst’s activity gradually declines due to carbon deposition. Studies have found that both CO and CH4 undergo carbon deposition reactions; at 570°C, the disproportionation reaction of CO is dominant (2CO → CO2 + C, Δ_r H_m = 173 KJ/mol), while at 750°C, the decomposition reaction of CH4 is dominant (CH4 → 2H2 + C, Δ_r H_m = 75 KJ/mol). Carbon deposits exist in two forms: carbides and graphite carbon, with graphite carbon being the primary form. In practical production, for safety and precautionary reasons, it is generally advisable to keep the reaction temperature below 550°C (for David Company in the UK, 574°C is the upper limit for the shutdown valve protection in methanation reactors).
NI(CO)4 is formed at a reaction temperature of around 200°C, and the mechanism for deactivating the catalyst is the loss of NI.
At over 200 degrees, gaseous nickel carbonyl is formed and carried away by the airflow