Rui P.P.L. Ribeiro

Electric Swing Adsorption for Gas Separation and Purification: A Review

Electric Swing Adsorption is one of the emerging separation processes for gas cleaning and purification. It has already been industrially tested for Volatile Organic Compounds (VOCs) abatement and other markets are envisaged in the near-term future, especially the capture of carbon dioxide from anthropogenic sources. In this work, the fundamentals of the ESA process are discussed and the possible different regeneration steps are explained. A state-of-the-art review of the process applications is disclosed and the future trends for process implementation are discussed.

Challenges of Electric Swing Adsorption for CO2 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.

Diffusion of the small, very polar, drug piracetam through a lipid bilayer: an MD simulation study

One of the major goals to improve drug discovery is to understand the molecular properties that influence oral bioavailability. Molecular dynamics-based methods have been used to understand passive diffusion with atomic detail and to predict diffusivities and permeabilities. In this paper, we explore the structural and dynamic behavior of piracetam, a nootropic drug, using umbrella sampling, as it crosses a 1,2-dioleoyl-sn-glycero-3-phosphocholine bilayer model. This is accompanied with a potential of mean force profile, showing the partition equilibrium within the bilayer. We discuss important molecular properties and their influence to the permeation of this important drug. Piracetam changes its solution-dominant conformation, modifying its polar surface area and forming an internal hydrogen bond, to facilitate penetration into the hydrophobic core. Rotation and orientation patterns, as piracetam diffuses across the membrane, were also analyzed, and we found out that in bulk water and at the membrane center piracetam shows no specific orientation as it rotates quickly and freely, whereas near the phospholipids’ polar head groups its polar atoms are much more oriented and the rotation is slowed down by more than one order of magnitude. Altogether, the study provides a very detailed view of the events mediating the permeation of this small and very polar drug.

A Sensitive Method Approach for Chromatographic Analysis of Gas Streams in Separation Processes Based on Columns Packed with an Adsorbent Material

A sensitive method was developed and experimentally validated for the in-line analysis and quantification of gaseous feed and product streams of separation processes under research and development based on column chromatography. The analysis uses a specific mass spectrometry method coupled to engineering processes, such as Pressure Swing Adsorption (PSA) and Simulated Moving Bed (SMB), which are examples of popular continuous separation technologies that can be used in applications such as natural gas and biogas purifications or carbon dioxide sequestration. These processes employ column adsorption equilibria on adsorbent materials, thus requiring real-time gas stream composition quantification. For this assay, an internal standard is assumed and a single-point calibration is used in a simple mixture-specific algorithm. The accuracy of the method was found to be between 0.01% and 0.25% (-mol) for mixtures of CO2, CH4, and N2, tested as case-studies. This makes the method feasible for streams with quality control levels that can be used as a standard monitoring and analyzing procedure.