双核磺化酞菁钴与硫化钠反应的伏安法研究

Voltammetry study on the reaction between binuclear sulfonated phthalocyanine cobalt and sodium sulfide

关键词:  湿法脱硫  双核磺化酞菁钴  硫化钠  伏安法  多硫离子

Key words:  wet desulfurization  binuclear sulfonated phthalocyanine cobalt  sodium sulfide  voltammetry  polysulfide ions

摘要:

PDS脱硫法有效解决了氰化氢中毒问题,得到许多企业的青睐,但副盐问题仍然是目前整个脱硫行业十分关注 的话题。采用循环伏安法对PDS脱硫体系中双核磺化酞菁钴(bi-CoPc)与硫化钠的反应过程进行了研究。结 果表明:Na₂S和Na₂S_x在玻碳电极上的氧化反应是受浓度扩散控制的不 可逆反应,且S^2-向S₈的转化并不是一步完成,而是先转化成S^2- S_x,进而再生成S₈。此外,参与反应的S^2-仅有20%转化为S₈。S^2-_x以S^2-₂~S²₉中的某两种形式为主要存在形式,且S_x^2-的存在形式可能对于S₈的生成速率和生成量有一定影响。bi-CoPc在水溶液中易与OH-形成配合物,加入碳酸盐缓冲溶液,可降低配合物的形成能力,同时,Co⁺/Co²⁺的氧化还原反应更易发生。bi-CoPc与Na₂S反应先生成S^2-₂,然后S^2-₂可转化为更长链的S^2-_x,最终形成S₈。该研究结果有助于加深对脱硫机理的了解,同时,对降低副产物生成有一定的指导意义。

Abstract:

PDS desulfurization method has been applied widely because of effectively solving the problem of hydrogen cyanide poisoning. However, the by-products problem is still a hotspot concerned in whole desulfurization field at present. The reaction between binuclear sulfonated phthalocyanine cobalt (bi-CoPc) and sodium sulfide was studied by the cyclic voltammetry in this paper. The results showed that the oxidation reaction of Na₂S and Na₂S_x on glassy carbon electrode was an irreversible process controlled by concentration diffusion. And the transformation from S^2- to S₈ was not a one-step process, but firstly transformed into the intermediate, S^2-_x, then further generated S₈. Moreover, it was deduced that only 20% of S^2- involved in the reaction was converted into S₈. S^2- xhad two main existing forms within the range from S^2-₂ to S^2-₉, and their forms might have influences on the formation rate and production amount of S₈. Bi-CoPc could be more readily form the coordination complex with OH- in aqueous solution than in carbonate buffer system, but the redox reaction of Co⁺/Co²⁺ is easier in carbonate buffer system than in aqueous system. Meanwhile, S^2-₂ was formed firstly in the reaction between bi-CoPc and Na₂S, S^2- _2then could transformed into S^2- xwith a longer chain, finally formed S₈. It was helpful for us to understand the mechanism of PDS desulfurization, and it also had guiding significance for reducing the formation of by-products.