The impact of the MTBE catalytic distillation column on acid consumption in the alkylation unit
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Generally, catalytic distillation columns are used in the fractionation towers of MTBE plants, which can improve the MTBE conversion rate to a certain extent. However, such columns affect the separation efficiency, causing residual tetrahydrocarbons to be carried along with MTBE; this in turn impacts the acid consumption in the alkylation unit. According to the Rumus process theory, the acid consumption should be below 50, but in practice it varies greatly. My analysis of the reason for this is as follows; I’m not sure if it makes sense
Is it feasible to convert a catalytic distillation column into a conventional distillation column?
:(Why do some people have them and others don’t?)
Hehe. This edition is for non-technical professionals to discuss. Generally, after etherification, C4 is used as a raw material for alkylation, and inevitably chemicals such as methanol and MTBE that consume acid are present. Today, catalytic distillation is used for MTBE to improve the conversion rate of isobutane.
After etherification, C4 is washed with water (to remove methanol) and adjusted (to achieve the required alkene-to-alkane ratio in the feedstock), before entering the alkylation reaction. Large fluctuations in acid consumption are not necessarily due to MTBE.
It is not advisable to deliberately adjust the operation of the MTBE unit solely in order to reduce acid consumption. As long as the catalytic distillation column is operating properly, the MTBE content in the overhead vapor should be very low, and it can even be brought down to ppm levels. Acid consumption is influenced by various factors, including impurities, water, oxides, butadiene, C5 compounds, and so on. If your facility indeed has MTBE or C5 compounds in its alkylation feedstock, it is recommended to install an dewaxing column.
What is contained in the composition of C4? What are the levels of C5 and butadiene?
The MTBE content is high at the beginning of catalyst replacement in the catalytic distillation tower due to the remaining C4 compounds, and it decreases after one year of operation. Doesn’t this indicate a problem with the separation efficiency of the catalytic distillation tower? Moreover, even if some isobutylene fails to react and ends up in the alkylation process, it isn’t a waste after all
Building another tower – the workload is way too large, right?:
Check if there are other reasons; MTBE does not cause significant fluctuations in acid consumption.