Kinetics of Methanation in a Packed Bed Reactor

Purpose

This experimental apparatus is designed for the study of the methanation reaction in a packed bed reactor. The reaction is catalyzed by a supported Nickel catalyst in, essentially, a plug flow reactor.

The reaction may be considered as irreversible (why?) and the rate of reaction could be described by an equation of the Hougen-Watson form :

where k is related to temperature an Arrhenius equation.

With the Methanation apparatus and its data acquisition facilities, you should obtain data sufficient to determine the constants in the rate equation and the Arrhenius constants. Note that because of stoichiometry, and under conditions of excess H2, that not all terms in the denominator can be identified.

Equipment Preparation

A schematic diagram showing all thermocouple and valve locations is on the control board of the apparatus.

• The infrared analyzer as well as the reactor have slow dynamics, e.g. may take nearly two hours to warm up. Plan accordingly.
• Reactor temperature control has been improved by the implementation of a triac which can be set for any temperature and is continuously monitored by the computer (see Program use). The triac allows you to maintain an essentially between 270 and 350 degrees Celsius.

Running the Reaction and Collecting Data

• Read downstream data.
  • Open valves A - D.
  • Close bypass valve.
  • Run reaction gas through reactor.
  • Wait for steady state conditions.
  • Read downstream data.
• Read upstream data.
  • Close valve D.
  • Open bypass valve.
  • Read upstream data.
• Alternatively - calculate feed concentration from flow rates.

Helpful Hints

• Allow two hours for the infrared analyzer to heat up. You can either come in before lab and turn it on, or ask one of the shop technicians to do it for you in the morning. The analyzer needs to be periodically zeroed (consult instruction manual in the laboratory).
• Be careful of coking problems in the reactor. If the temperature seems to be acting in a strange way, turn off the CO feed and pass pure H2 through the reactor. This procedure should reactivate the catalyst.

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