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Background
Background
Catalytic methanation is the reaction of carbon dioxide with hydrogen to produce methane. Wanting to explore this reaction and it's potential importance in a hydrogen economy, I set out with a small team of engineers to explore this process.
Our reactor (pictured Left) made use of a nickle-based catalyst; however, my team was unsure of the kinetics governing the reaction. The concern stemmed from the catalyst- at high temperatures, the perceived kinetic rate of the reaction would shift to a pore diffusion limited reaction. To better understand this, my team set out to determine the kinetic rate law and the Arrhenius parameters for converting CO2 and H2 to CH4.
The full report is found below. The principle takeaways from this project were:
Diffusive deviations from a kentic rate law became significant around 290 °C and dominant beyond 300 °C.
According to our results, we conclude that 7.91 molminof CH4 will be produced from a 10,000 SLM feed of 4.0% CO2 and 20% H2 at 270 ⁰C and 1 atm. The reaction performs reasonably well at these operating conditions (about 50% conversion)
The reaction rate is more dependent upon the inlet partial pressure of H2 than it is upon CO2. As mentioned in a paper by Bartholomew, the catalyst is poisoned at low levels of H2.
With natural gas selling at a market price of around $9.52 per thousand cubic feet, we would only generate approximately $62,000 of revenue per year for an isothermal CSTR with one ton of catalyst operated at 270 °C and 1 atm with a feed of 1.0 x 104 SLM containing 4.0% CO2 and 20% H2. The operating costs will vastly exceed the revenue generated.
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