Analysis and Discussion of the Results from Catalyst Evaluation Experiments

Thread Content

The catalyst used in the catalyst evaluation apparatus was 10 g. The problems that arose during the mass balance calculation for the conversion of methanol to propylene are as follows: the amount of methanol solution fed in can be measured; the water produced by the reaction, the water present in the raw materials, and the heavy hydrocarbons generated by the reaction can also be measured. Based on the mass balance, the amount of gaseous hydrocarbons can be determined by taking the difference between these two measured values. After separating the reaction products into oil and water, the amount of heavy hydrocarbons can be calculated. By dividing the measured amounts of heavy hydrocarbons and gaseous hydrocarbons by the amount of raw material used, the overall yield of hydrocarbons can be determined. The problem is that the yield calculated in this way is much higher than the theoretical value (the theoretical value is 14 g of hydrocarbons per molecule of methanol after the removal of water; dividing 14 by the molecular weight of methanol, which is 32, gives 43.75%). In reality, however, the yield calculated using this method is 63%, with a methanol conversion rate of 99.4% and a hydrocarbon selectivity of 99.5%). What could be the reason for such a large deviation of the actual value from the theoretical value?