The dry point of the reformation feed increases; why does the xylene yield decrease?
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The control target for the dry point of the feed material during reformation is set at <180°C; however, due to abnormalities in atmospheric pressure, the dry point rose to 205°C. As a result, the yield of xylene decreased from 17 tons/h to 7 tons/h, while the yield of C9+ aromatics increased. What is the reason behind this?
Is it suspected that the dryness level is too high, resulting in reduced catalyst activity and an overall decrease in the aromatics conversion rate? Could you pay attention to the conversion rates of other aromatics as well?
Yes, the increase in temperature leads to a decrease in catalyst activity, which results in a significant reduction in the overall aromatic conversion rate. Additionally, some alkanes with more than 10 carbon atoms fail to cyclize into aromatics and remain mixed in the xylene. In my opinion, the decrease in xylene yield is caused by an increase in heavier components starting from C9. For example, if the feed to the xylene column is 35 tons, the output of xylene is 15 tons, the output of C9 compounds is 18 tons, and the output of heavier components is 2 tons. As the dry point rises, the amount of C9 and heavier components increases, which in turn leads to an increase in the amount of reformed aromatic hydrocarbons. With the feed to the xylene column remaining unchanged, the yield of C9 and heavier components increases, resulting in a decrease in the xylene yield.