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Introduction
Objective
Theory
Experiment
Results
Zeolite ZSM-5
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Several experimental runs have been done at the following conditions: 70 cc/min Nitrogen flowrate, 20 cc Methanol feed at 1 cc/min flowrate, Reactor temperature setpoint at 600 C, Condenser set point at 1 C. Preliminary results appear promising.
Reaction products have been obtained which appear to be "gasoline". The product smells like gasoline. Additionally, using the Gas Chromatograph with Mass Spectroscopy (GC/MS) has shown the presence of benzene and toluene in the product, which indicates that at least some of the reactant has gone to the desired endpoint.
The temperature of the reactor had appeared to be oscillating randomly during reactions. However, on closer inspection it appears that the variation in reactor temperature is a result of the high exothermicity of the reactions taking place inside it. See Figure 1, next page, for a plot of reactor temperature vs. time in Trial B. The temperature appears to dip at first, probably because as methanol is injected at time zero, the heat of vaporization is absorbed from the reactor, lowering its temperature. However, the temperature soon rises rapidly, probably because the exothermic reactions have begun, releasing heat and raising the temperature of the reactor. After about twenty minutes, the methanol has all run out, the reaction slows or stops, and the reactor temperature slowly goes back to its initial temperature. These variations of reactor temperature will be very difficult to counteract in our system due to the transient nature of the phenomena. The only way to reduce them would be to try to induce a steady state of reaction and heat transfer, perhaps by injecting methanol feed at a very slow rate over a very long time. However, it may not be possible to conduct the experiment this way. More work will be done in this area soon.
Mass balances of catalyst before and after reaction had shown about a 3% drop in mass after reaction, even though there was obviously coke deposits on the catalyst which should have increased the catalyst mass instead. This phenomenon had puzzled us; was it due to loss of catalyst during handling (spills), or something else? Dr. Herz had suggested that the catalyst may have adsorbed moisture from the atmosphere which was subsequently desorbed in the high temperatures of reaction, reducing the apparent mass of the catalyst. To investigate this, a small amount of catalyst was carefully massed, dried, and massed again. The catalyst sample weighed 13.547 g before drying, and 13.088 g after drying-a drop of 3.4%. This seems to support Dr. Herz's theory of water adsorption on the catalyst, which would explain the change in apparent mass of the catalyst.
We will soon explore the effects of varying residence time (weight of catalyst divided by flowrates of nitrogen and methanol) on the reaction.