An Interesting and Novel Approach to Chemical Separations of Which I was Unaware.
In 2011, the late great Nobel Laureate George Olah proposed a closed carbon cycle to address the on going and accelerating tragedy of climate change: Anthropogenic Chemical Carbon Cycle for a Sustainable Future George A. Olah, G. K. Surya Prakash, and Alain Goeppert Journal of the American Chemical Society 2011 133 (33), 12881-12898
Intrinsic to this concept is access to sustainable energy, of which there is one, and only one form, nuclear energy, since the reduction of carbon dioxide requires the addition of all the energy released when it was created (The First Law of Thermodynamics) plus the energy required to overcome the entropy of mixing connected with dumping it into the environment (The Second Law of Thermodyanmics).
To paraphrase something I read somewhere, although I cannot remember the attribution, "The best time to have discussed this was at least 20 years ago, the second best time is now."
Also intrinsic to this conception, which would include sequestering carbon in products as opposed to dumps, is the chemical separation of chemical products, already an important element of our modern life, for good and for bad, a refinery for dangerous petroleum is essentially a chemical separations plant, relying heavily on the use of distillation, with increasing sophistication.
A paper I came across this morning puts a new wrinkle on distillation, of which I was unaware, although apparently it's been around for sometime adding a dimension to adsorption based technologies (governed by Langmuir and BET theory) by adding centrifugation.
The paper is this one: Radial Temperature Profile Measurements to Understand Mass Transfer in Rotating Packed Bed Distillation
Hina Qammar, Tobias Pyka, Jörg Koop, Andrzej Górak, and Gerhard Schembecker Industrial & Engineering Chemistry Research 2023 62 (38), 15588-15599
From the introductory text:
Maldistribution in the gas and liquid phases has been a challenge in both types of equipment, i.e., columns and RPBs. Both equipment types tend to show maldistribution, especially for the liquid phase. (1,11) Since in an RPB, the cross-sectional area of the packing increases from the inner to the outer packing diameter, the liquid load decreases throughout the packing, which may result in dewetting of packing surface areas at some parts. Therefore, liquid maldistribution along the radius of the rotor is expected to account for the reduced mass transfer performance of RPBs. Groß et al. (11) showed the results of Gamma-ray tomography and concluded that rotational speed affects liquid holdup in the packing, and at higher rotational speeds, the liquid holdup reduces rapidly along the radial packing length. Not only does the liquid load become smaller, but the strength of the centrifugal field also increases linearly with the radial position in the rotor.
Furthermore, at the inner diameter of the packing, a liquid ring exists that diminishes almost linearly toward the outer diameter of the packing. (11) Guo et al. (12) conducted a theoretical study using a three-dimensional simulation in an RPB to understand the liquid flow behavior, droplet size, specific surface area, and residence time. The results show that the particular area of liquid droplets increases, whereas the residence time of the liquid in an RPB decreases rapidly with increasing rotational speed. They proposed that increasing the rotational speed or the liquid inlet velocity could help to minimize the liquid maldistribution... (12)
...In this work, the experimental setup developed by Hampel et al. (16) and Qammar et al. (17) is further used with temperature measurements along the rotor’s radius to characterize the mass transfer profile in the packing of an RPB as well as in the casing separately. This work aimed to understand the mass transfer contribution of different sections/zones in an RPB for different rotor configurations and not to achieve the maximum separation efficiency in an RPB. Figure 1 shows an overview of the sensor positions and the process flow of distillation in RPB...
The Hampel paper, which is open sourced is here: Recent Advances in Experimental Techniques for Flow and Mass Transfer Analyses in Thermal Separation Systems Chem. Ing. Tech. 2020, 92, No. 7, 926–948.
I am not a process chemist, although I am professionally required to be aware of process chemistry, but was unaware of this particular approach. The nature of this separation comes under the general rubric of "orthogonality" which is also a component of analytical chemistry, one that is increasingly important and on which I often focus my professional research.
Cool, I think, obscure but important.
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