The problem of passivation in stainless steel reaction vessels
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Reactions are carried out in stainless steel reactors; for the first step, concentrated sulfuric acid is used as the solvent, while for the second step, formamide is used as the solvent. The temperature is raised to 140°C during the reaction, and ammonia gas is generated during this process. Iron ions are present in the product obtained later – what’s the reason for this?
Concentrated sulfuric acid: It is usually stored and transported in iron containers, so the concentrated sulfuric acid you use already contains iron ions. And your reaction still takes place in a stainless steel reactor. What you need to do now is: first, control it at the source – sulfuric acid, of analytical purity. For water and cleaning, deionized water must be used. Second, the product needs to be deionized somehow.