Yesterday, before leaving the lab, I ran a trial testing a catalyst another student had made, only using a higher concentration of methane in the reactants. We expected to see a proportionate change in the resulting methane concentration after running through the reactor, but saw almost no change. Thus begins our problem shooting.
There were a couple essential areas of fault here: method (experimentor systematic error), the measuring device (systematic error- is the GC insensitive to methane?) and the flow meters (random error- if the flow of one gas changes randomly as the regulators are wont to do, it will change the concentration of the reactant mixture randomly)
The rest of the day was spent trying to isolate these areas of error. The major method fault is that we cannot separate the independent variables of time (always changing) and temperature (what we want to change to evaluate the effectiveness of our catalyst). If the catalyst deteriorates with time (due to oxidization of the materials) then the consecutive trials will lower in reaction yield even with an increase in temperature, a change that generally spurs reactions to become more active. We were, however, able to rule out the sensistivity of our machine by running 100% methane through the GC and seeing a doubling of the output relative to the 50% mixture we left yesterday with. This means that the failure to change between yesterday’s two mixtures (going from 3% to 50%) was due to some other issue. We then took two more trials at the same heat and saw a regressive curve with consecutive trials. It appeared that our catalyst had a lifespan. In order to fix this, Dr. Hotz showed Maya how to pretreat the catalyst while I worked on collecting calibration points.