Barium Sulfate Crystallization in the Presence of Variable Chain Length Aminomethylenetetraphosphonates and Cations (Na+ or Zn2+)

• Published in: Crystal growth & design Vol. 7; no. 2; pp. 321 - 327
• Main Authors: Barouda, Eleni, Demadis, Konstantinos D, Freeman, Sandra R, Jones, Franca, Ogden, Mark I
• Format: Journal Article
• Language: English
• Published: Washington,DC American Chemical Society 01-02-2007
• Subjects: Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Exact sciences and technology; Physics; Structure of solids and liquids; crystallography; Organic molecule; Chain length; Transition elements; Crystallization; Phosphonates; Chemical inhibition; Zinc; Barium sulfates
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/cg0604172

Barium sulfate is a common scale in oil production installations that is treated and controlled with phosphonate inhibitors. A fundamental understanding of how these inhibitors operate, however, is only slowly emerging. In this paper, we investigate the effect on barium sulfate crystallization of two very similar phosphonate molecules that only differ in their backbone spacing, ethylenediamine-N,N,N‘,N‘-tetra(methylenephosphonic acid) (EDTMP) and hexamethylenediamine-N,N,N‘,N‘-tetra(methylenephosphonic acid) (HDTMP). It was found that the inhibitory efficacy of the organic molecules depends on their structural differences but also on the presence of other cations such as Zn2+. It appears that both stereochemical considerations and complexation strength differences between the two phosphonate additives result in different inhibitory powers. In the presence of zinc cations and EDTMP, it is found that inhibition is related to the concentration of uncomplexed (“free”) organic.