questions on catalyst

[Sparx88]

Ok maybe a rookie question here. I see in various comps things like red iron oxide, black oxide as a catalyst. In Pyro, what does that mean, or what does it do? I know that the word means to increase a chemical reaction, but what exactly is the reaction in star comps that benefits from the catalyst?

 

I haven't used any before but am now getting ready to move into these kinds of star comps soon.

[OldMarine]

I think I was reading a thread on FW in which Mike Swisher explained the catalyst question. If I recall he stated that the catalyst actually acted in the flame envelope and it was impossible to tell if it was altered or not because it was consumed or just ejected by the reaction. Edited March 4, 2016 by OldMarine

[FlaMtnBkr]

I think the word is used a bit loosely in pyro, and normally is referred to something that speeds up the reaction and sometimes meant to make things hotter/bigger/more intense.

 

A true catalyst is added to speed along a reaction but is present at the end in the products as the same thing that was initially added. In pyro it's usually consumed and nothing like what was originally added as it's burnt up in the flame. Nothing to be concerned with but usually not a true catalyst.

 

I would be curious which star formulas you are referring to, where a catalyst is discussed and added.

[Seymour]

Catalysts lower the activation energy required for a reaction to occur. By definition the catalyst is not a reactant and as such is not 'used up'. This also means that they are used in small quantities, with 1% being a very typical quantity for pyrotechnics. Off on a tangent, as such Sulfur is not a catalyst because it is a fuel, and thus a reactant. It lowers the activation energy of gun powder just by having a lower activation energy than charcoal. It is incorrectly called a catalyst frequently in youtube videos.

 

It gets tricky when a catalytic ion is contained in a molecule that is a reactant. For example Copper benzoate... It is absolutely a reactant, but Copper is a well known catalyst for perchlorate. Where are our definitions now???

 

The specific action that they affect may vary a lot and in the context of fireworks it is often quite unknown. All sorts of stages of reactions can be catalysed, but the most common seems to be the decomposition of the oxidiser occurring at a lower temperature. However I am sure that it is sometimes more complex and things happen like the catalyst inducing the oxidiser to break down producing more of certain intermediate products (that are almost instantly destroyed) which just happen to be very effective at breaking certain bonds in a particular fuel...

 

With a few exceptions, notable whistle fuel and Potassium nitrate/Sugar, catalysts are not really that important, and I feel like they are added quite un necessarily without even having any evidence to suggest that they make enough difference to be worthwhile. At least this is how I'd describe my own use of them Sometimes I just want to make compositions "fancy" and "elite" and "exotic". Often it looks exciting on paper and that's it.

Edited March 5, 2016 by Seymour

[Fulmen]

Agreed, the term catalyst can be a bit imprecise in reactions like this. Technically a catalyst isn't consumed by the reaction. It might form intermediate species, but must revert back to it's original form to qualify. But unless you're running a continuous reaction where the catalyst would be available for the entire process there really isn't much difference between that and an accelerant or burn rate modifier.

[LiamPyro]

MnO2 is a "true" catalyst, right? I have a book and it lists a composition for impact firecrackers (torpedoes) that contains 1% MnO2, it says to mill it in with the KCIO3.

[Mumbles]

It's hard to say really without analyzing the residue and products after the combustion. I'd put MnO2 in the same category as iron oxides, copper oxides, copper chromite, etc. They're burn rate modifiers for sure and probably sensitizers, possibly catalysts.

 

A majority of times we're talking about catalysts in conjuction with a composition, it's relating to a chemical agent that assists in the breakdown of chlorates and perchlorates. This is a well known phenomenon. With the right equipment, it's easy to test even. If you search on this subject, the vast majority is for ammonium perchlorate, due to it's prevalence in the aerospace industry. There are some papers on potassium perchlorate though. There really isn't any definitive information given on mechanism or mode of action that I've seen however, and nothing really on the ultimate fate of the "catalyst".

[lloyd]

Mumbles,

In order to qualify as a catalyst, the compound must remain unmodified after the reaction, even if it enters into it during the reaction.

 

Manganese dioxide is a well-known catalyst for certain 'test tube' reactions we experimented with in high school chemistry classes.

 

Iron oxide may also contribute as a high-temperature oxidizer, so it's role as 'catalyst' is somewhat suspect.

 

But the "ultimate fate of a catalyst" MUST be that it remains the same composition in the same amount after the reaction as before.

 

Lloyd

[Fulmen]

Sure, but it's a moot point. If you're running a lab synthesis or a continuous process it makes a difference as the catalyst can be reused. In a pyrotechnical comp it's wasted, so there really isn't any practical differences between a catalyst and a burn rate modifier.

[lloyd]

That's not what I meant (and I think you knew that!)

 

If a 'pure' catalyst is used in a pyrotechnic composition, it has different effects and contributions than if a "somewhat catalytic" material is used that also enters into the combustion.

 

The goal, even in lab experiments, isn't to 'recover' the catalyst, except perhaps to prove the point that it was one.

 

Mmmm?

 

LLoyd

[Sparx88]

I see it in some rocket fuels like red iron in rocket candy, or used in glitter comps as well. Sparklers come to mind. Does the reaction benefit from iron/steel additives like this from the slower but hot burn rate to even out a fuels power band or help prevent maybe a blow out? It's interesting something going through a reaction like that and still remain intact after It's another "I shoulda took school more seriously" moments. I have lot's of those. But I do notice on videos concerning rocket fuels that adding the red iron oxide really wakes it up though.

[Fulmen]

If a 'pure' catalyst is used in a pyrotechnic composition, it has different effects and contributions than if a "somewhat catalytic" material is used that also enters into the combustion.

Are you sure? As most catalysts and burn rate modifiers are present in low, single digit percentages the differences would be slight. And a catalyst could affect affect flame chemistry even after it's original function was done. So differentiating between a proper catalyst and a BRM can be hard. A compound can have a purely catalytic action on the initial decomposition of the oxidizer and then be consumed in the combustion, or simply affect the reaction while it's consumed. The difference can be of great theoretical importance, but I'm not so sure about the practical implications.

[lloyd]

"The difference can be of great theoretical importance, but I'm not so sure about the practical implications."

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I will certainly concede that. As I do this commercially, I'm interested in both characteristics.

 

Lloyd

[Fulmen]

For commercial applications even subtle differences can be of great importance, you're right about that. And if you're developing new compositions a greater understanding of the actual effect can be beneficial. Still, we're in a gray area here.