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Heat of Rx for Aerosolization Reaction?

Heat of Rx for Aerosolization Reaction?

Heat of Rx for Aerosolization Reaction?

(OP)
Oxidation of titanium tetrachloride with O2 occurs at high temps, but produces a solid product, with the overall reaction given below:

TiCl4 + O2 -> TiO2 + 2Cl2

There are quite a few mechanistic steps in between, but the overall reaction has the reactants as completely gas-phase and the product a mixture of solid and gas phase. The reaction happens in what is essentially a tubular reactor. I have a question that I've never received a satisfactory answer to - does the heat of reaction go towards heating the products, reactants, or both? If this process were slow (mixing speed >>> reaction speed), I would expect that the temperature rise could be predicted by the reactant/product mass average Cp.

However, this reaction is very fast - reaction rate is largely controlled by diffusion/mixing rate of one gas into another, and typically is 99%+ complete in, say, less than 0.25 seconds.

In this scenario, is the temperature rise governed by average reactant mass Cp (including products and reactants) or by the product mass average Cp? There is a large difference in average Cp between the reactant and products. Would it be more complex, with Cp depending on reaction %complete and average reactant/product Cp at a given distance down the reactor?

As I think about the mechanisms at work, the heat is released when new bonds are formed, meaning the products will receives the initial heat of reaction first. Then, it would be up to heat transfer to transfer any of that heat to reactants, correct?

RE: Heat of Rx for Aerosolization Reaction?

Seems to me to be a fairly complex question. There may be some software models that can work at this level. Note that the heat of formation may be manifested as a combination of kinetic energy rise and radiative emission. The latter could be re-absorbed by the stuff swirling around, or may be absorbed by the chamber walls.

In a well-controlled experiment, you might be able tease out the various components.

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RE: Heat of Rx for Aerosolization Reaction?

"As I think about the mechanisms at work, the heat is released when new bonds are formed, meaning the products will receives the initial heat of reaction first. Then, it would be up to heat transfer to transfer any of that heat to reactants, correct?"

Yes. The heat release also drives convection and mixing of hot products with reactants. You might want to read some texts/papers on combustion.

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