Exploring the Potential of Metal-Organic Frameworks for the Separation of Blends of Fluorinated Gases with High Global Warming Potential.

The research on porous materials for the selective capture of fluorinated gases (F-gases) is key to reduce their emissions. Here, the adsorption of difluoromethane (R-32), pentafluoroethane (R-125), and 1,1,1,2-tetrafluoroethane (R-134a) is studied in four metal-organic frameworks (MOFs: Cu-benzene-1,3,5-tricarboxylate, zeolitic imidazolate framework-8, MOF-177, and MIL-53(Al)) and in one zeolite (ZSM-5) with the aim to develop technologies for the efficient capture and separation of high global warming potential blends containing these gases. Single-component sorption equilibria of the pure gases are measured at three temperatures (283.15, 303.15, and 323.15 K) by gravimetry and correlated using the Tóth and Virial adsorption models, and selectivities toward R-410A and R-407F are determined by ideal adsorption solution theory. While at lower pressures, R-125 and R-134a are preferentially adsorbed in all materials, at higher pressures there is no selectivity, or it is shifted toward the adsorption R-32. Furthermore, at high pressures, MOF-177 shows the highest adsorption capacity for the three F-gases. The results presented here show that the utilization of MOFs, as tailored made materials, is promising for the development of new approaches for the selective capture of F-gases and for the separation of blends of these gases, which are used in commercial refrigeration.

Batch chromatography with recycle lag. I-Concept and design.

This is the first of a two-part study in which we explore the concept of batch chromatography with recycle lag, concluding with the design, construction, and experimental validation of a prototype that embodies the physical realization of this concept. Moreover, the apparatus is simple to set up in particular in view of large-scale applications. Here the theory behind batch chromatography with recycle lag is revisited and extended, with emphasis on the mathematical formulation and procedure for deriving the single-column batch analogue of any variant of multicolumn simulated countercurrent chromatography. By resorting to selected examples, namely GE Healthcare Bio-science's three-column periodic countercurrent chromatography, Novasep's sequential multicolumn chromatography, and a few hypothetical multicolumn processes, we discuss how the theory can be operationalized. Finally, we conclude by describing the design of a device or apparatus-an eluate recycling device (ERD)-to physically realize the proposed concept. The ERD implements an approximate "first in, first out" method for organizing and manipulating the to-be-recycled fractions of eluate collected from the chromatography column, where the oldest (first) amount fluid, or 'head' of the fraction, is the first to exit and be recycled to the column.

Batch chromatography with recycle lag. II-Physical realization and experimental validation.

This is the second of a two-part study in which we explore the concept of batch chromatography with recycle lag, concluding with the design, construction, and experimental validation of a prototype-an eluate recycling device (ERD)-that embodies the physical realization of this concept. The ERD implements an approximate "first in, first out" method of organizing and manipulating the to-be-recycled fractions of eluate collected from the chromatography column, where the oldest (first) amount fluid, or 'head' of the fraction, is the first to exit and be recycled back to the column. Moreover, the apparatus is simple to set up in particular in view of large-scale applications. Here we detail the construction of the ERD and assembly of a setup to interconnect the ERD and a chromatography column. Through the coordinated operation of two-way valves and two-position six-port switching valves it is possible to implement a diverse set of configurations or operating modes interconnecting the chromatography column and the ERD. The setup is validated experimentally with success using the separation of a nucleoside mixture by reversed phase chromatography as a model problem. It is also shown that by redesigning the fluid distributor using 3D printing technology the ERD performance can be improved.

Challenges of electric swing adsorption for CO(2) capture.

This work focuses on the application of electric swing adsorption (ESA) as a selective postcombustion technique to capture and concentrate CO(2) from flue gases of power plants. The initial application should be the capture of CO(2) from flue gases of combined cycle natural gas (NGCC) power plants: the CO(2) content ranges from 3-5 %, with up to 12 % of oxygen. Several challenges to deploy this process for a large-scale application are pointed out. Materials such as amine-modified resins or zeolites should be good candidates for this process (indirect ESA) because they exhibit good loadings at low partial pressures of CO(2). The process design should take into account the temperature increase due to adiabatic operation, pushing the effective loadings to values around 20 % of maximum loading. Several process operations are suggested in order to improve the CO(2) purity and recovery and also to integrate the ESA process with other sources of heat, which may have an important impact in energy consumption.