Methanation Catalyst

A small amount of carbon oxide in the syngas reacts with hydrogen in the presence of the methanation catalyst to form easily removed water and inert methane to protect the synammonia catalyst.The reaction equation is as follows:

CO+3H2=CH4+H2O     △H298=-206.2kJ/mol

CO2+4H2=CH4+2H2O    △H298=-165.0kJ/mol 

Methanation is a convenient and economical method of gas purification, which is widely used in modern ammonia plants and hydrogen plants.If the fault occurs in this process, it will make the catalyst in the post section "poisoning", and can not normal production or affect the economic operation of the device.

n industry, nickel-aluminum series methanation catalyst is generally used, the active component is nickel oxide, Al2O3 as the carrier, adding a certain amount of additives. Methanation catalyst was developed in the 1960s. With the introduction of 300kt/a ammonia synthesis plant in China in the 1970s,  with the continuous development of production, users have higher and higher requirements for methanation catalysts, hoping that some properties of methanation catalysts can be developed.

1.Significant burn loss.This will waste valuable driving time in the process of temperature reduction because of the need to remove some of the ineffective substances;The voids that may be created during the removal of inactive substances may provide opportunities for strength reduction and deflection, causing use problems.

2. The contraction is obvious.The catalyst will shrink during use, which will cause two problems:

① Reduce the actual volume of catalyst, objectively increase the catalyst operating airspeed :② the difference in particle shrinkage time and shrinkage speed may produce "small bridge", resulting in uneven distribution of air flow.

3. The restoration time is long.This is very uneconomical for the user, raises the cost of driving and wastes valuable production time.

4. Poor resistance to toxicity.The influence of poison on catalyst is significant. Once the catalyst is poisoned, it may lose its activity and become unusable and forced to be replaced.

5. Pore volume and specific surface area are small.Methanation reaction is basically carried out on the surface of the catalyst. If the surface area is small, the contact surface with the raw gas will be small, and the activity will be affected, so it is difficult to reach the standard of export trace.

6. There are problems with strength properties.In the case of operation accidents such as the decarbonized strip liquid, the catalysts of the original bond type and the ordinary sintered type have a great possibility of pulverization.Generally more than moderate with liquid accident can only be forced to replace the catalyst.

7.Anti-decarbonizing fluid problem.The catalyst is after the decarbonization process, and the problem of using the catalyst caused by the invasion of decarbonization solution is a common accident in this process. It is hoped that the catalyst can have the ability to recover quickly after the decarbonization solution accident.

8. Bond resistance problem.Methanation reaction is a strong exothermic reaction. In the accident, the total carbon content at the inlet may rise sharply, causing the temperature of catalyst bed to rise to a certain height. At this time, the catalyst may bond and affect its use.It is hoped that the catalyst can have certain temperature resistance to avoid bonding.