Exploring Geometric Properties and Cycle Design in Packed Bed and Monolith Contactors Using Temperature-Vacuum Swing Adsorption Modeling for Direct Air Capture.

This study presents a comprehensive comparison between the packed bed and monolith contactor configurations for direct air capture (DAC) via process modeling of a temperature-vacuum swing adsorption (TVSA) process. We investigate various design parameters to optimize performance across different contactor geometries, including pellet size, monolith wall thickness, active sorbent content in monoliths, and packed bed structure configurations, considering both a traditional long column (PB) and multiple shorter columns configured in parallel (PB). Our parametric analysis assesses specific exergy consumption, sorbent, and volume requirements across different operating conditions of a five-step TVSA cycle.

On Comparing Packed Beds and Monoliths for CO Capture from Air Through Experiments, Theory, and Modeling.

This study compares the performance of amine-functionalized γ-alumina sorbents in the form of 3 mm γ-alumina pellets and of a γ-alumina wash-coated monolith for CO capture for direct air capture (DAC). Breakthrough experiments were conducted on the two contactors to analyze the adsorption kinetics and performance for different gas feeds. A constant pattern analysis revealed dominant mass transfer resistances in the gas film and in the pores, with axial dispersion also observed, particularly at higher concentrations.

Assessment of Potential and Techno-Economic Performance of Solid Sorbent Direct Air Capture with CO Storage in Europe.

Direct air capture with CO storage (DACCS) is among the carbon dioxide removal (CDR) options, with the largest gap between current deployment and needed upscaling. Here, we present a geospatial analysis of the techno-economic performance of large-scale DACCS deployment in Europe using two performance indicators: CDR costs and potential. Different low-temperature heat DACCS configurations are considered, i.

On Solute Recovery and Productivity in Chiral Resolution through Solid-State Deracemization by Temperature Cycling.

Temperature cycling represents an effective means for the deracemization of chiral compounds that crystallize as conglomerates and racemize in solution. In such a process, a suspension enriched in the desired enantiomer is converted into an enantiopure one through periodic cycles of crystal dissolution and crystal growth. We show that performing temperature cycling at higher temperatures leads to faster deracemization and, consequently, higher productivity.

Kinetics and Thermodynamics of Lactose Mutarotation through Chromatography.

The mutarotation kinetics and thermodynamics of the reaction α-lactose ⇌ β-lactose have been measured in dilute solutions using liquid chromatography without any derivatization step, using a C18 column and pure water as the mobile phase. The effect of temperature (0.5-45 °C) of the starting powder composition (α-lactose-rich or β-lactose-rich powder) and of the solvent composition (water with up to 35% weight fraction of seven organic solvents) has been experimentally investigated.

Monitoring Aqueous Sucrose Solutions Using Droplet Microfluidics: Ice Nucleation, Growth, Glass Transition, and Melting.

Freezing and freeze-drying processes are commonly used to extend the shelf life of drug products and to ensure their safety and efficacy upon use. When designing a freezing process, it is beneficial to characterize multiple physicochemical properties of the formulation, such as nucleation rate, crystal growth rate, temperature and concentration of the maximally freeze-concentrated solution, and melting point. Differential scanning calorimetry has predominantly been used in this context but does have practical limitations and is unable to quantify the kinetics of crystal growth and nucleation.

Exact and Ubiquitous Condition for Solid-State Deracemization in Vitro and in Nature.

Solid-state deracemization is the amplification of an enantiomeric excess in suspensions of conglomerate-forming chiral compounds. Although numerous chemical and biochemical compounds deracemize, its governing mechanism has remained elusive. We introduce a novel formulation of the classical population-based model of deracemization through temperature cycles to prove that suspensions deracemize whenever a simple and ubiquitous condition is met: crystal dissolution must be faster than crystal growth.

HPLC method development for the quantification of a mixture of reacting species: The case of lactose.

Preparative and analytical chromatography are impaired by analytes that undergo a chemical reaction during the chromatographic separation, leading to peak distortion and systematic errors during the subsequent quantification phase. The pitfalls are highlighted through a combination of analytical results and numerical simulations. Two different quantification strategies for partially overlapping and reacting peaks are compared.

In-situ experiment reveals CO enriched fluid migration in faulted caprock.

The sealing characteristics of the geological formation located above a CO storage reservoir, the so-called caprock, are essential to ensure efficient geological carbon storage. If CO were to leak through the caprock, temporal changes in fluid geochemistry can reveal fundamental information on migration mechanisms and induced fluid-rock interactions. Here, we present the results from a unique in-situ injection experiment, where CO-enriched fluid was continuously injected in a faulted caprock analogue.

The Role of Operating Conditions in the Precipitation of Magnesium Hydroxide Hexagonal Platelets Using NaOH Solutions.

Magnesium hydroxide, Mg(OH), is an inorganic compound extensively employed in several industrial sectors. Nowadays, it is mostly produced from magnesium-rich minerals. Nevertheless, magnesium-rich solutions, such as natural and industrial brines, could prove to be a great treasure.

Developing Versatile Contactors for Direct Air Capture of CO through Amine Grafting onto Alumina Pellets and Alumina Wash-Coated Monoliths.

The optimization of the air-solid contactor is critical to improve the efficiency of the direct air capture (DAC) process. To enable comparison of contactors and therefore a step toward optimization, two contactors are prepared in the form of pellets and wash-coated honeycomb monoliths. The desired amine functionalities are successfully incorporated onto these industrially relevant pellets by means of a procedure developed for powders, providing materials with a CO uptake not influenced by the morphology and the structure of the materials according to the sorption measurements.

How to make climate-neutral aviation fly.

The European aviation sector must substantially reduce climate impacts to reach net-zero goals. This reduction, however, must not be limited to flight CO emissions since such a narrow focus leaves up to 80% of climate impacts unaccounted for. Based on rigorous life-cycle assessment and a time-dependent quantification of non-CO climate impacts, here we show that, from a technological standpoint, using electricity-based synthetic jet fuels and compensating climate impacts via direct air carbon capture and storage (DACCS) can enable climate-neutral aviation.

Thermodynamics Explains How Solution Composition Affects the Kinetics of Stochastic Ice Nucleation.

The freezing of aqueous solutions is of great relevance to multiple fields, yet the kinetics of ice nucleation, its first step, remains poorly understood. The literature focuses on the freezing of microdroplets, and it is unclear if those findings can be generalized and extended to larger volumes such as those used in the freezing of biopharmaceuticals. To this end, we study ice nucleation from aqueous solutions of ten different compositions in vials at the milliliter scale.

Process Performance and Operational Challenges in Continuous Crystallization: A Study of the Polymorphs of L-Glutamic Acid.

The crystallization of the two polymorphs of l-glutamic acid (LGA) is carried out in a continuous crystallization process, and its performance according to different criteria is evaluated. The study aims at identifying suitable operating conditions for producing either αLGA or βLGA with a high polymorphic purity. To this end, we investigate the process both from a theoretical perspective and through experiments using either a single stirred-tank crystallizer or a cascade of two stirred-tank crystallizers in series.

Conceptual Validation of Stochastic and Deterministic Methods To Estimate Crystal Nucleation Rates.

This work presents a generalized framework to assess the accuracy of methods to estimate primary and secondary nucleation rates from experimental data. The crystallization process of a well-studied model compound was simulated by means of a novel stochastic modeling methodology. Nucleation rates were estimated from the simulated data through multiple methods and were compared with the true values.

Online 3D Characterization of Micrometer-Sized Cuboidal Particles in Suspension.

Characterization of particle size and shape is central to the study of particulate matter in its broadest sense. Whilst 1D characterization defines the state of the art, the development of 2D and 3D characterization methods has attracted increasing attention, due to a common need to measure particle shape alongside size. Herein, ensembles of micrometer-sized cuboidal particles are studied, for which reliable sizing techniques are currently missing.

Online Monitoring of the Concentrations of Amorphous and Crystalline Mesoscopic Species Present in Solution.

Despite the growing evidence for the existence of amorphous mesoscopic species in a solution and their crucial roles in crystallization, there has been the lack of a suitable method to measure the time-resolved concentrations of amorphous and crystalline mesospecies in a lab-scale stirred reactor. This has limited experimental investigations to understand the kinetics of amorphous and crystalline mesospecies formation in stirred solutions and made it challenging to measure the crystal nucleation rate directly. Here, we used depolarized light sheet microscopy to achieve time-resolved measurements of amorphous and crystalline mesospecies concentrations in solutions at varying temperatures.

Stochastic ice nucleation governs the freezing process of biopharmaceuticals in vials.

Biopharmaceuticals commonly require freezing to ensure the stability of the active pharmaceutical ingredients (APIs). At commercial scale, freezing is typically carried out over the course of days in pallets comprising tens of thousands of vials. The selected process conditions have to ensure both complete freezing in all vials and a satisfactory manufacturing throughput.

Solubility of Organic Salts in Solvent-Antisolvent Mixtures: A Combined Experimental and Molecular Dynamics Simulations Approach.

We combine molecular dynamics simulations with experiments to estimate solubilities of an organic salt in complex growth environments. We predict the solubility by simulations of the growth and dissolution of ions at the crystal surface kink sites at different solution concentrations. Thereby, the solubility is identified as the solution's salt concentration, where the energy of the ion pair dissolved in solution equals the energy of the ion pair crystallized at the kink sites.

Secondary Nucleation by Interparticle Energies. III. Nucleation Rate Model.

A nucleation rate model for describing the kinetics of secondary nucleation caused by interparticle energies (SNIPEs) is derived theoretically, verified numerically, and validated experimentally. The theoretical derivation reveals that the SNIPE mechanism can be viewed as enhanced primary nucleation, i.e.

Solid-State Deracemization via Temperature Cycles in Continuous Operation: Model-Based Process Design.

Solid-state deracemization via temperature cycles converts a racemic crystal mixture into an enantiopure product by periodic cycling of the temperature in the presence of a racemization catalyst. A continuous counterpart of this conventional batch-operated process is proposed that can be performed in mixed suspension mixed product removal crystallizers (MSMPRCs). More specifically, three different configurations are described to perform periodic forcing via temperature cycles, which differ from each other in the type of the feed and in the withdrawal system.

Crystallization-Induced Deracemization: Experiments and Modeling.

Inspired by deracemization via temperature cycles, which enables the collection of crystals of the desired enantiomer from an initially racemic mixture, we focus in this work on an alternative batch process, namely crystallization-induced deracemization. This process starts with a suspension of enantiomerically pure crystals, which undergoes a simple cooling crystallization, coupled with liquid-phase racemization. The experimental and model-based analysis of such a process, carried out here, revealed that: (i) deracemization via temperature cycles is a safe choice to operate with high enantiomeric purity, although its throughput is limited by the suspension density; (ii) if the distomer is less prone to nucleation, crystallization-induced deracemization is a simple process; however, its performance is strongly limited by the solubility; (iii) the purity achieved with crystallization-induced deracemization can be increased by utilizing large seed mass and by optimizing the cooling profile or catalyst concentration.

Accounting for the Presence of Molecular Clusters in Modeling and Interpreting Nucleation and Growth.

The effect of molecular cluster formation on the estimation of kinetic parameters for primary nucleation and growth in different systems has been studied using computationally generated data and three sets of experimental data in the literature. It is shown that the formation of molecular clusters decreases the concentration of monomers and hence the thermodynamic driving force for crystallization, which consequently affects the crystallization kinetics. For a system exhibiting a strong tendency to form molecular clusters, accounting for cluster formation in a kinetic model is critical to interpret kinetic data accurately, for instance, to estimate the specific surface energy γ from a set of primary nucleation rates.

Secondary Nucleation by Interparticle Energies. II. Kinetics.

This work presents a mathematical model that describes growth, homogeneous nucleation, and secondary nucleation that is caused by interparticle interactions between seed crystals and molecular clusters in suspension. The model is developed by incorporating the role of interparticle energies into a kinetic rate equation model, which yields the time evolution of nucleus and seed crystal populations, as in a population balance equation model, and additionally that of subcritical molecular clusters, thus revealing an important role of each population in crystallization. Seeded batch crystallization at a constant temperature has been simulated to demonstrate that the interparticle interactions increase the concentration of the critical clusters by several orders of magnitude, thus causing secondary nucleation.

Deracemization via Periodic and Non-periodic Temperature Cycles: Rationalization and Experimental Validation of a Simplified Process Design Approach.

Solid-state deracemization via temperature cycles is a promising technique that combines crystallization and racemization in the same batch process to attain enantiomer purification. This method is particularly attractive because the target enantiomer can be isolated with a 100% yield, and a large number of operating parameters can be adjusted to do this effectively. However, this implies that several choices need to be made to design the process for a new compound.