We performed a design calculation to determine the amount of catalyst that we should use. To achieve a space time of one hour, the mass of catalyst is calculated to be 90g. The corresponding methanol feed flow rate should be 130 ml/h. As for temperature, the second parameter that has a strong effect in the product composition, we found that our reactor design did not foresee the large temperature gradient that exists. In previous experiments, the temperature throughout the reactor was presumed to have remained constant at 600 ^oC, as was set by the controller. In order to measure the temperature variations inside the reactor, a thermocouple was inserted at the bottom. However, the temperature measured was of the empty space and did not give an accurate description of the temperature variations inside the reactor. To verify whether the reactor has reached a steady state temperature, a thermocouple was inserted inside the reactor and its location was varied as the experiment proceeded.
The results were as follows: Temperatures at different locations in the reactor are given below. Note that the location L is defined as the thermocouple's height in the catalyst bed. The catalyst bed is 30 cm overall.

      Top of the reactor, L= 30cm T=300^oC       L= 22cm T=400 ^oC       L=11 cm T=420^oC       Bottom, L= 0-3cm T=350^oC

As observed, the temperature inside the reactor varies, and these variations are expected to have an important effect in the product composition. However, according to the experimental results obtained by Chang in the temperature range of 300-450 ^o C, the formation of aliphatics, aromatics and C2-C4 hydrocarbons are favored. Even though the temperature inside the reactor varies, these temperature values are favorable in obtaining the desired product. We made a modification to help achieve a uniform steady state temperature at least at the beginning of a reactor run. This was accomplished by heating the reactor and allowing its temperature to reach a constant value before methanol was injected. The catalyst was also activated for approximately an hour by flowing nitrogen inside the reactor. The reactor temperature was set by the controller to be 340 ^oC.
      Important assumptions were made in order to simplify the physical interpretation. The flow rate of methanol was assumed to remain constant, which more accurately means negligible disruption during refills. We estimated 30sec disruption out of ten minute run cycle, which is apparently very small. The reactor temperature is assumed to be at a steady state and even though the temperature values change in different portions of the reactor, these values are within the favorable limits in obtaining the desired product.

    The following represents the experimental results of the last trial:

In the last experimental trial the volume of the catalyst was calculated by the ratio of the mass and density which was 137ml. The nitrogen flow was set to 70cc/min and the flow rate of methanol was set to 15ml/hr. The condenser set point was 1^oC and the reactor jacket temperature was set to 340^oC. This space time calculated gave a nine hour space velocity (with ignorance of the nitrogen flowrate). This is a very large space time, which according to the experimental results by Chang the amount of byproducts should be large. Using gas chromatography and mass spectroscopy, we determined the product composition to consist mainly of propane, butane, pentane, methyl butene cyclopentane, methyl pentane, hexane, methyl cyclopentane, benzene, methyl hexane, toluene. In this experimental trial, paraffins were detected and one possible explanation is perhaps related to the temperature effect. According to Chang, the higher the temperature of the reactor, especially above 600^oC, the smaller is the amount of paraffins in the final product. However, more analysis has to be done in this area.



Chang, Clarence., "Hydrocarbons From Methanol," New York, 1984.