A.2.3 Basic operating procedure
The sample system should be mounted as close as possible
to the reactor inlet in order to minimize lag time. Air
(20.93% O
2
) is used as the source of O
2
, and the air/CH
3
OH
vapor mixture is sampled at the reactor inlet. The XMO2
continuously verifies that the optimal amount of O
2
(typically
9.8%) is present for the reaction to proceed safely to a
maximized yield. Too low an O
2
level will decrease the yield,
while too high an O
2
level will create a safety hazard.
For this application the required calibration gases are:
• Zero Gas: N
2
(at least 99.95% pure - 0.0% O
2
)
• Span Gas: air (20.93% O
2
)
Note: Any compatible display device may be specified.
A.2.4 Previous systems
Dumbbell-type paramagnetic O
2
sensors were once
commonly used for this application. However, such systems
required extensive maintenance and frequent manual
calibration. In addition, the sensors were easily damaged by
condensable liquids, requiring frequent sensor replacement.
As the XMO2 provides continuous, accurate monitoring of
the reactor feed gas O
2
content with maintenance-free
operation and excellent calibration stability, it is now the
system of choice.
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