Filtration process for purifying liquid azole heteroaromatic compound-containing mixtures

A process for removing impurities from a liquid azole heteroaromatic compound-containing mixture, which comprises the following steps:

• (a) providing a liquid feed flow comprising an azole heteroaromatic compound-containing mixture and having impurities;
• (b) providing a filtration system comprising:
• (1) an initial filtration section comprising at least two parallel filtration units;
• (2) an intermediate filtration section positioned after the initial filtration section having one or more intermediate filtration subsections, each intermediate filtration subsection comprising at least two parallel filtration units;
• and (3) a final filtration section comprising at least two parallel filtration units positioned after the intermediate filtration section, wherein each filtration unit of the initial filtration section, each intermediate filtration subsection and the final filtration section each comprise one or more filtration membranes selected from the group consisting of nanofiltration membranes and ultrafiltration membranes, each filtration membrane having a molecular pore size in the range of from about 200 daltons to about 1 kilodalton;
• (c) passing a first portion of the feed flow of step (a) through each filtration unit of the initial filtration section of step (b) to provide an initial permeate comprising an at least partially purified azole heteroaromatic compound-containing mixture and an initial retentate comprising at least some impurities;
• (d) passing a second portion of the feed flow of step (a) in a cross-flow manner through each filtration unit of each intermediate filtration subsection of the intermediate filtration section of step (b) to provide an intermediate permeate comprising an at least partially purified azole heteroaromatic compound-containing mixture and an intermediate retentate comprising at least some impurities;
• (e) passing a third portion of the feed flow of step (a) in a cross-flow manner through each filtration unit of the final filtration section of step (b) to provide a final permeate comprising an at least partially purified azole heteroaromatic compound-containing mixture and a final retentate comprising at least some impurities;
• and
• (f) adding at least some of the initial, intermediate, and final retentates from steps (c) through (e) to the feed flow of step (a).