Yes Definitely,

As the inter-molecular distance between the reactants is less, lower activation energy is required.

Simply, consider that every chemical process needs energy to break the bonds and to intermix properly, as the micro-channel reactors have higher and efficient mixing of reactants the part of the energy required to overcome the mass transfer barrier gets reduced but chemical transformation part remains unchanged. In this way the net activation energy in intensified reactor is reduced.

It's not just the size up and down, but concentration/viscosity, speed/movement parameters, space for mixing and remixing, flow, currents (not electrical) dynamics, etc. also contribute!

Rick Lee Of course, It will affect.

Activation energy affects the intensified reactors and the various reactor theory associated along with the characteristics of reactors. The reactor, the key component of a majority of chemical processes, has received more attention than other unit operations in the context of intensification.

Ritesh Malani thk for your kind explanation, do you mean that part of the activation energy coming from mass transfer ?

activation energy = mass transfer barrier + chemical transformation ?

microreactor reduce the mass transfer limitation thus reduce in resultant activation energy?

Rick Lee

yes , i think so . in micro - reactors , but that mass transfer is a component of activation energy , i don 't think we have active energy as we don 't react to only mass transfer .

two things are separate .

@Rick Lee

Yes part of activation energy was utilized to overcome mass transfer barrier.

Thus, smaller reactor such as intensified reactors reduces mass transfer barrier.

The same approach I used to intensify tranesterification process using ultrasound.

You can refer my recent papers

Rick Lee

When designing a reactor, you need to increase the proportion of active molecules. Only active molecules react in a collision. The proportion of active molecules increases the temperature increase, the catalyst, electromagnetic radiation ... Therefore, when designing the reactor you need to provide for the participation of these regulators to increase the reaction rate.

The activation energy value is only affected by the type of reaction and the type of catalyst used. The use of a microreactor or other type of reactor does not affect the value of the activation energy of the chemical reaction taking place in it. I have the impression that the author of the question and some of the respondents do not distinguish between activation energy and apparent activation energy.

Rick Lee, There is no relationship between the size of the microchannel and the average distance between the molecules, which you suggest in the question. A change in the average distance between molecules can only take place as a result of a change in concentration. However, reducing the size of the microchannel will reduce the average distance of the molecules from its internal surface. So, if we immobilize the catalyst/biocatalyst on this surface, the average distance of the molecules from its active centers will decrease. Due to this, the conversion in the output stream may increase. However, the catalyst/biocatalyst must keep up with the processing of the molecules diffusing into its active centers. So what about activation energy? Of course, it will be smaller, but only due to the presence of a catalyst/biocatalyst, not a change in the size of the microchannel. This is the whole secret of the so-called intensified reactor. Regards,

Ritesh Malani, A smaller inter-molecular distance between the reactants may be due to higher pressure or concentration. As a result, the initial rate of a chemical reaction with an order greater than zero will increase. But it certainly will not affect the activation energy. The smaller the microchannel size, the greater the likelihood of laminar flow. But then one should forget about mixing in the fluid stream.

Miroslaw Grzesik, Thank you for giving a more reasonable answer for getting lower mass transfer coefficient in micro-channel reactors. Ultimately, the activation energy is nothing but the energy which has to be spend to bring the molecules together and further transfer of electrons/protons so that chemical reactions occurs. Thus, in view of that, I agree with you regarding that there is no direct relation between reactor size and activation energy, but in depth bringing the molecules closer by reducing the inter-molecular distance between them, is a part of mass transfer barrier in the reaction which also needs some energy and that part is minimized in micro-channel or intensified reactors.

I don't know why you bring up the intermolecular distance problem again. At a given concentration, the diameter of the microchannel does not affect the intermolecular distance, but the distance of the substrate molecules from the active surface of the microchannel. As a result, the rate may increase. Mass transport resistances in such microchannels are negligible, so no additional energy is needed.

Dear Miroslaw Grzesik, it would be great if you could share your articles or any other articles with regards to your answers and comments above.

Dear Syamsul Rizal Abd Shukor, The above is a commonly available basic knowledge on mass transfer and chemical reactions. I don't think one should cite any articles or books here. If you have a different opinion on the question asked, please write. This is a discussion forum. Regards,

Just a general comment. Consider the traditional first-order kinetic of reaction occurs in the micro-channels, so we can write the rate of reaction:

-dC/dt = kC where k = k0*exp(-Ea/(RT)); Ea is the activation energy, k0 is the pre-exponential factor.

Recall the basic chemistry knowledge that the activation energy is determined by the chemistry, e.g., nature of chemicals and catalysts used. It's independent of the mixing condition. The pre-exponential factor is of course depends on the mixing intensity - i.e., better mixing leads to a higher collision rate that leads to a faster reaction rate. In this way, a microreactor might outperform the conventional macro reactor due to a more intense mixing in the former, thus increasing the k0 value.