As we have said before, manufacturing triazine-based scavengers is simple—in theory. The devil’s in the details. This devil is also true for MMA-triazine manufacturing, if not more so.
One of our customers started lab-scale production of 40% MMA-triazine, using the OPAL-103 Triazine Analysis System to analyze the quality. Just like with MEA-triazine, MMA-triazine has a nice Raman spectrum with clearly-defined, characteristic peaks that enable quantification with an appropriate internal standard (see figure above). The two minute test is easy to perform.
MMA-triazine is produced from equimolar amounts of methylamine and formaldehyde. Unlike monoethanolamine, however, methylamine is not available in “pure” form as a liquid. This amine is generally available in two forms for triazine production: as a salt or as a 40% aqueous solution.
Every couple weeks, our customer would send us a test report showing roughly 27% MMA-triazine. The data looked perfect. They asked us: what’s wrong? Why is our triazine measuring so much lower than expected.
So, we started some calculations on MMA-triazine reactions. The fastest way to start making MMA-triazine is to purchase 40% MMA in water and 37% formaldehyde in water (formalin). The molecular weights of MMA and formaldehyde are nearly the same (31 vs 30 g/mol), so as a first test, mix equal mass quantities of each. At first blush, two ~40% solutions mixed together that react in equimolar amounts should yield ~40% MMA-triazine. Or so our customer incorrectly thought…
Because that is not what happens. When MEA or MMA reacts with formaldehyde, three molecules of each are consumed—producing a triazine molecule and three molecules of water. This reaction is why MEA-triazine is available at a maximum of 80%. For MMA-triazine, starting with 40% MMA and 37% formaldehyde yields a maximum product of—drum roll—27% by weight.
To get to higher concentrations, it is necessary to start with a form of MMA that does not contain water—methylamine hydrochloride, for example. Unlike with liquid monoethanolamine, the solid MMA hydrochloride is not 100% MMA: it is 46% MMA and 54% hydrochloride by mass. But with the MMA salt and formalin, it is possible to produce up to 38% MMA-triazine. A true 40% formulation requires using 50% formaldehyde, something that requires more complex equipment (heated trucks). Less scrupulous manufacturers might be inclined to label their formalin-based blends as 40%—caveat emptor.
Note that even with paraformaldehyde, the maximum concentration is 70% by weight without going to more exotic forms of methylamine. And that does not include the water that would need to be added to dissolve these two solids to accelerate the reaction.
If you are thinking about making MMA-triazine, note that the chemical engineering is a little different. The starting materials, the calculations, and then process need to be carefully considered. A tool like the OPAL-103 is a necessary piece of equipment for process development and control.