I recently came across a paper focusing on the hydrodeoxygenation of oxygen-containing compounds. The paper linearized the rate equation in order to determine the experimental reaction order with respect to reactant "A". The paper found that the experimental reaction order was ~1.08 (I'm assuming the theoretical order should be 1). The interpretation was that this higher experimental reaction order with respect to "A" signified that the "A" mass transfer limitation dominated the reaction. How does this interpretation come about? Can someone help explain how a lower or higher experimental reaction order in comparison to the theoretical reaction order can be interpreted? Thanks in advance for the assistance!
Note that a reaction order of unity is only found for elementary reactions. Many reactions are not elementary, since they involve intermediate species (in particular when catalysts are involved). So the first question is whether you expect hydro-deoxygenation to be an elementary reaction or not.
Dear Jamison Watson,
Any chemical reaction mechanism can be developed in terms of a number of elementary reactions steps or lumped reactions steps.
In the case of elementary reaction mechanisms, the rate of each reaction step in the reaction mechanism is written in term of elementary steps (through KTG theory for gaseous mixtures). The type of these reactions (uni-molecular, bi-molecular or tri-molecular) determines the order of the reactions. For example
A + B C + D is bi-molecular reaction with elementary reaction rate as=AT^(a)exp(-Ea/RT)[A][B]
But, when we start writing lump reactions (a reduce set for compact models), we start averaging out the number of elementary steps (a combination of uni, bi and trimolecular reactions) to get the required production/consumption of any given specie of interest. Hence, this type of averaging leads to non-integral order for the lumped reactions.
- Badges
- Science topic
- Similar topics
- Philosophy
- Esthetics
- Interpretation