When designing a dispersant for sludge/varnish control and high temperature deposit inhibition, the process usually begins with the selection of the polymer tail, which is responsible for maintaining oil solubility. The most commonly used polymer is polyisobutylene (PIB), which is produced from the refinery C4 line and has an olefin group at the end of the molecule. The olefin end group allows the polyamine or polyol head to be attached to create the dispersant. To simplify this process, the PIB is first attached to the linking group and then reacted with the desired polar head group. There are two types of linking group chemistries used in the industry: maleated and phenol methanol alkylated, which produce succinimide dispersants and Mannich base dispersants, respectively.
However, these traditional succinimide dispersants and Mannich base dispersants, both used for sludge/varnish control and high temperature deposit inhibition, are not effective in maintaining oil rheology control in media containing a large amount of soot. This is because the surface of the soot particles is highly aromatic, and aromatic dispersants are sometimes required to effectively bond and disperse them. Exchanging the polyamine head groups with aromatic amines or aromatic esters while retaining the basic polymer structure and architecture has resulted in only marginal improvements. As a result, new dispersant structures have been developed that interact strongly with the soot surface.
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