We explored the potential of plasma-based In-Situ Resource Utilization (ISRU) for Mars through the conversion of Martian atmosphere (∼96% CO2, 2% N2, and 2% Ar) into life-sustaining chemicals. As the Martian surface pressure is about 1% of the Earth’s surface pressure, it is an ideal environment for plasma-based gas conversion using microwave reactors. At 1000 W and 10 Ln/min (normal liters per minute), we produced ∼76 g/h of O2 and ∼3 g/h of NOx using a 2.45 GHz waveguided reactor at 25 mbar, which is ∼3.5 times Mars ambient pressure. The energy cost required to produce O2 was ∼0.013 kWh/g, which is very promising compared to recently concluded MOXIE experiments on the Mars surface. This marks a crucial step towards realizing the extension of human exploration.

Nitrous oxide (N2O) is considered the primary source of NOx in the atmosphere, and among several abatement processes, catalytic decomposition is the most promising. The thermal energy necessary for this reaction is generally provided from the external side of the reactor by burning fossil fuels. In the present work, in order to overcome the limits related to greenhouse gas emissions, high heat transfer resistance, and energy losses, a microwave-assisted N2O decomposition was studied, taking advantages of the microwave’s (MW) properties of assuring direct and selective heating. To this end, two microwave-susceptible silicon carbide (SiC) monoliths were layered with different nickel–cobalt–aluminum mixed oxides. Based on the results of several characterization analyses (SEM/EDX, BET, ultrasound washcoat adherence tests, Hg penetration technique, and TPR), the sample showing the most suitable characteristics for this process was reproduced in the appropriate size to perform specific MW-assisted catalytic activity tests. The results demonstrated that, by coupling this catalytic system with an opportunely designed microwave heated reactor, it is possible to reach total N2O conversion and selectivity of a highly concentrated N2O stream (50 vol%) at T = 550 °C, the same required in the conventionally heated process to remove N2O from a less concentrated gas stream (20 vol%).

Nitrous oxide (N2O), produced from several human activities, is considered a greenhouse gas with significant environmental impacts. The most promising abatement technology consists of the catalytic decomposition of N2O into nitrogen and oxygen. Many recently published papers dealing with N2O catalytic decomposition over Ni-substituted Co3O4 are related to the treatment of N2O concentrations less than 2 vol% in the feed stream. The present work is focused on developing catalysts active in the presence of a gaseous stream richer in N2O, up to 20 vol%, both as powder and in structured configurations suitable for industrial application. With this aim, different nickel-cobalt mixed oxides (NixCo1−xCo2O4) were prepared, characterized, and tested. Subsequently, since alumina-based slurries assure successful deposition of the catalytic species on the structured carrier, a screening was performed on three nickel-cobalt-alumina mixed oxides. As the latter samples turned out to be excellent catalysts for the N2O decomposition reaction, the final catalytic formulation was transferred to a silicon carbide monolith. The structured catalyst led to the following very promising results: total N2O conversion and selectivity towards N2 and O2 were reached at 510 °C by feeding 20 vol% of N2O. It represents an important achievement in the view of developing a more concretely applicable catalytic system for industrial processes.

N2O has a global warming potential about 300 times higher than CO2, and even if its contribution to the greenhouse effect is underrated, its abatement in industrial production’s tail gas has become imperative. In this work, we investigate the feasibility of the microwave (MW)-assisted regeneration of a 13X zeolite bed for N2O capture from tail gases. Several consecutive adsorption–desorption cycles were performed to verify the microwave heating effect on the zeolite’s adsorption properties. The results of the experimental tests, performed at N2O concentrations of 10, 20 and 40% vol, highlighted that (i) the steps are perfectly repeatable in terms of both adsorbed and desorbed amount of N2O, meaning that the MWs did not damage the zeolite’s structure, (ii) the presence of both H2O and O2 in the feed stream irreversibly reduces the adsorbent capacity due to nitrites and nitrates formation, and (iii) the presence of H2O alone with N2O still reduces the adsorbent capacity of the zeolites, which can be recovered through MW-assisted regeneration at 350 °C. Moreover, the MW-assisted TSA assured an energy and purge gas saving up to 63% and 82.5%, respectively, compared to a traditional regeneration process, resulting in effective process intensification.

Nitrous oxide (N2O) was recognized as a strong greenhouse gas that can be reduced by applying post-treatment technologies. N2O catalytic decomposition is considered the most attractive method for N2O abatement due to its easy operation and high efficiency. Among several catalysts, the cobalt-based mixed oxides have been identified as the most performing for this reaction. In this work a NixCo3-xO4 catalyst was prepared, characterized by means of nitrogen physisorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray fluorescence spectroscopy (XRF), and tested in the N2O decomposition reaction in presence of two different reactant mixtures, by using N2O and O2 with two different vol% as reactants, in order to evaluate the effect of the latter on the catalytic behavior. The results demonstrated that the concentrations of N2O and O2 in the gaseous stream strongly influenced the activity of the catalyst, indeed, by halving the O2 concentration, the N2O conversion increases from 54 % to 79 %. The NixCo3-xO4 sample resulted a promising catalyst for N2O decomposition reaction of gaseous stream containing up to 5 vol% of N2O, also in presence of O2.

Nitrous oxide is an effective greenhouse gas, which also greatly contributes to the depletion of the stratospheric ozone. Among the most common abatement methods, the capture of N2O by adsorption and the consequent reutilization appears as the best technique. In this work, the adsorption – regeneration cycle of N2O on 13X zeolites has been intensified by electrification of the process. More in detail, the regeneration step has been conducted in an innovative way, by employing a microwave heating. For the adsorption step, a concentrated stream consisting of 40 %vol N2O has been used, while the regeneration one was carried out using a stream of 100 %vol Ar and a power of 500 W for microwave heating. Each complete adsorption – regeneration cycle has been repeated several times, considering both wet and dry conditions for the gas mixture to be adsorbed, to prove the repeatability of the process. The results of the tests revealed that microwaves allowed to regenerate the solid adsorbent bed, by obtaining a significant reduction in the purge gas consumption and a recovery of 100 %. Therefore, employing a microwave-assisted regeneration step led to a process intensification, with respect to a conventional Temperature Swing Regeneration.

A novel adsorption differential volumetric apparatus was developed for the determination of diffusional time constants in nanoporous materials and applied to diffusion of nitrogen and argon in commercial pellets of 4A zeolite. The system is designed for high rates of data acquisition allowing to determine mass transfer time constants of seconds over the pressure range from vacuum to 130 kPa. Diffusion of N-2 and Ar on a single pellet and fragments obtained from the pellet are studied between -10 degrees C and 35 degrees and 0.8 to 55 kPa. These systems are chosen as representing weak adsorption to demonstrate the sensitivity of the apparatus that gives a good signal-to-noise ratio even with a single pellet in the entire pressure range. The systems studied confirm micropore diffusion control and an isothermal diffusion model was shown to reproduce accurately the observed kinetics using reduced pressure plots. As the crystal size in the pellet is not known accurately, the resulting activation energies and the ratio of diffusional time constants of N-2 and Ar were used to validate the results against known literature values.

The energy consumption in the temperature swing adsorption (TSA) process is essentially due to the heating of the purge gas used in the regeneration of the adsorbent bed. The use of microwave (MW) irradiation, replacing the traditional heating technique, can result in process acceleration and energy costs reduction: the electromagnetic energy is directly converted into thermal energy inside the adsorbent bed, all the resistances to the heat transfer are overcome, and the heat flow becomes the opposite of the conventional one. In this work, the innovative MW-assisted regeneration of zeolites bed is investigated. A dedicated laboratory plant was set up, and the optimal operating conditions were studied and determined. The results highlighted (i) the heating of the zeolites up to 300 degrees C, (ii) an energy efficiency of 75 % (due to a more uniform heat transfer to the adsorbent) and (iii) the consecutive tests showed a perfect repeatability of the results in terms of CO2 adsorption and desorption, so evidencing that no modification occurred in zeolites after MW irradiation. In addition, both the adsorption and desorption steps were modelled through a simulation tool specifically realized in Air Liquide, and the results showed a good agreement between the predicted and experimental values.

Landfill gas (LFG) produced from municipal solid waste substrates represents an important source of RNG and the market for its upgrade is facing significant challenges in terms of energy consumption and operating costs. To ensure higher CH4 yields and avoid its release in the atmosphere, the LFG is collected below the atmospheric pressure by the use of a vacuum pump that results in the contamination of the LFG by air and particularly N2. Most of the proposed solutions, propose a two-step separation process in which the CO2 removal takes place in the first one while N2 removal in the second. This study focuses on the removal of the N2 from a decarbonated methane stream by a four-step PSA cycle. The impact of several parameters on process performance has been investigated using numerical simulations with the aim of simplifying the unit design and operational performances. In particular we investigate the effect of the pressure at the end of the desorption step showing that it is possible to operate the cycle with the desorption pressure slightly above atmospheric one. This allows avoiding the use of a dedicated vacuum pump with, however, a penalty in the energy required.

Due to its characteristics, hydrogen is considered the energy carrier of the future. Its use as a fuel generates reduced pollution, as if burned it almost exclusively produces water vapor. Hydrogen can be produced from numerous sources, both of fossil and renewable origin, and with as many production processes, which can use renewable or non-renewable energy sources. To achieve carbon neutrality, the sources must necessarily be renewable, and the production processes themselves must use renewable energy sources. In this review article the main characteristics of the most used hydrogen production methods are summarized, mainly focusing on renewable feedstocks, furthermore a series of relevant articles published in the last year, are reviewed. The production methods are grouped according to the type of energy they use; and at the end of each section the strengths and limitations of the processes are highlighted. The conclusions compare the main characteristics of the production processes studied and contextualize their possible use.

The mass transfer coefficient is a fundamental property needed to design adsorption gas separations. A collaborative study is presented where commercial LiLSX beads used in air vacuum swing adsorption for the production of oxygen are tested in two volumetric apparatuses. The initial results based on the software available in the commercial system seemed to point to a surface barrier model for the adsorption kinetics of nitrogen, but this system is known to be macropore diffusion controlled. A detailed model of the system and a new way of representing the experimental data are used to show that the mass transfer kinetics is clearly a diffusion process. Guidelines and recommendations on which tests are needed to ensure the correct use of a volumetric system in this case are presented. Through the correct interpretation of the flow through the valve in the two volumetric apparatuses, consistency in the mass transfer time constant is achieved. The effect of using the correct diffusion time constant vs the one obtained using the traditional approach is demonstrated comparing a typical oxygen vacuum swing adsorption process. A drop in performance of nearly 15% in both productivity and energy consumption is predicted if the incorrect diffusion time constant is used.

While metal–organic frameworks have been mostly studied in their crystalline form, recent advances have been made on their amorphous phases, both in fundamental understanding and in relation to possible applications. In particular, the zeolitic imidazolate (ZIF) glasses, that can be obtained from quenching liquid ZIFs, have shown promise. However, the details of their microscopic structure are very hard to probe experimentally. Here we use ab initio molecular dynamics simulations to investigate the nature of the ZIF glasses obtained from quenching molten ZIFs in silico. Through computational modeling of the melt–quench process on three different ZIF crystals, we aim to understand the effect of topology and chemistry upon the structure of the glass, compared to crystalline precursor and high temperature liquid. It is the first direct computational description of MOF glasses at the quantum chemical level.

Gas separation by adsorption processes such as pressure swing adsorption (PSA) presents an attractive alternative for upgrading biogas to biomethane. A new vacuum pressure swing adsorption (VPSA) cycle is proposed for a unit designed to purify pre-cleaned biogas (40% CO(2)and 60% CH4) in industrial conditions (feed flow rate more than 500 Nm(3)/h and large-volume equipment). The process simulations performed to optimize the VPSA unit consider the kinetic separation of the feed components by using an appropriate carbon molecular sieve (CMS) adsorbent having a high kinetic separation selectivity for CO(2)with respect to CH4. The designed VPSA unit is composed of five columns that perform three equalization steps. Minimizing methane losses during the regeneration steps necessitates injecting part of the off-gas rich in CO(2)at the bottom of the column during the production step to push the CH(4)forward. The produced biomethane meets the specification (97% CH4) of grid injection purity. The developed cycle allows a CH(4)recovery of 92% to be obtained with a specific energy consumption of 0.35 kWh/Nm(3), thus meeting the initial requirements for industrial exploitation of VPSA technology for biomethane purification from biogas sources.

This work focuses on the development of a Pt/Re/CeO2-based structured catalyst for a single stage water–gas shift process. In the first part of the work, the activity in water–gas shift reactions was evaluated for three Pt/Re/CeO2-based powder catalysts, with Pt/Re ratio equal to 1/1, 1/2 ad 2/1 and total loading ≈ 1 wt%. The catalysts were prepared by sequential dry impregnation of commercial ceria, with the salts precursors of rhenium and platinum; the activity tests were carried out by feeding a reacting mixture with a variable CO/H2O ratio, equal to 7/14, 7/20 and 7/24, and the kinetic parameters were determined. The model which better described the experimental results involves the water–gas shift (WGS) reaction and CO as well as CO2 methanation. The preliminary tests showed that the catalyst with the Pt/Re ratio equal to 2/1 had the best performance, and this was selected for further investigations. In the second part of the work, a structured catalyst, obtained by coating a commercial aluminum alloy foam with the chosen catalytic formulation, was prepared and tested in different reaction conditions. The results demonstrated that a single stage water–gas shift process is achievable, obtaining a hydrogen production rate of 18.7 mmol/min at 685 K, at τ = 53 ms, by feeding a simulated reformate gas mixture (37.61 vol% H2, 9.31 vol% CO2, 9.31 vol% CO, 42.19 vol% H2O, 1.37 vol% CH4).

Carbon molecular sieves are used in kinetically controlled separation processes. The mass transport in these materials can be quite complex as a result of their structure. In this contribution carbon dioxide uptake in a commercial carbon molecular sieve is analysed to show that the dynamic response does not correspond to a single mass transfer time constant. Experimental checks are discussed that ensure linearity and isothermal conditions as both have to be excluded in order to interpret correctly the dynamic curves. Surface barrier plus diffusion in micropores is compared to a distribution of surface barriers and the results show that a simple log-normal distribution of time constants reproduces with high accuracy the experimental transients. This is consistent with the way carbon molecular sieves are manufactured and requires only the definition of the variance of the distribution and the time constant at the mean.

Chemical and petrochemical companies are increasingly realizing that their sustainable development critically depends upon development of new innovative processes that use more efficiently materials and energy. As overall separation/ purification processes account for 40-60% of capital and operating costs, their amelioration can significantly reduce costs, energy use and waste generation by increasing profits. Gas separation by adsorption technology is a well-established unit operation in chemical and petrochemical industries due to its efficiency for dealing with a large range of gas separations including impurity removal, gas purification, and separation in recycle streams. The technology is far from being mature and opportunities to expand its domain of applicability and improve its efficiency are high in a context where better understanding of physical phenomena and technological progress in materials and engineering research are integrated. Major contribution for innovations in gas separation by adsorption technology relates to the discovery of new adsorbents with better separation characteristics coupled to process development and its optimization using multi-objective and multi-domain numerical approaches. This short review identifies technological gaps and drivers for accelerating the development of industrially important gas separations by adsorption.

Metal–organic frameworks are chemically versatile materials, and excellent candidates for many applications from carbon capture to drug delivery, through hydrogen storage. While most studies so far focus on the crystalline MOFs, there has been a recent shift to the study of their disordered states, such as defective structures, glasses, gels, and very recently liquid MOFs. Following the publication of the melting mechanism of zeolitic imidazolate framework ZIF-4, we use here molecular simulation in order to investigate the similarities and differences with two other zeolitic imidazolate frameworks, ZIF-8 and ZIF-zni. We perform first principles molecular dynamics simulations to study the melting phenomena and the nature of the liquids obtained, focusing on structural characterization at the molecular scale, dynamics of the species, and thermodynamics of the solid–liquid transition. We show how the retention of chemical configuration, the changes in the coordination network, and the variation of the porous volume in the liquid phase are influenced by the parent crystalline framework.

The molecular mechanism of action underlying general anesthesia remains a matter of controversy. One proposed mode of action involves binding of anesthetic molecules to membrane proteins such as ligand gated ion channels, thereby modulating their function. An alternative mode of action discussed in the literature is through binding to the lipid bilayer. We chose to explore both modes of action at the molecular level by studying two types of targets: pure lipid bilayer systems such as POPC, and a lipid bilayer with the pentameric ligand-gated ion channel GLIC inserted into it. Sauguet et al. recently solved the structure of GLIC in complex with the general anesthetic Xenon [1], describing a multitude of binding sites. Here, we studied the effect of a series of three Noble gases: Argon, Krypton and Xenon. We have performed molecular dynamics (MD) simulations to gain key insights on the Noble gases binding location and affinity. Different gas:lipid ratios were used to characterize their effect on the physical properties of the membrane, as well as their affinity for the core of the lipid bilayer. Microsecond-long flooding simulations, combined with free energy calculations, were run to characterize access to binding sites and quantify binding affinities of Nobles Gases on the GLIC channel. This work extends and generalizes our previous study on bromoform action on GLIC, that revealed a complex network of interconnected binding sites, possibly all contributing in concert to the anesthetic effect [2]. We go beyond previous work by considering the measurable effect on lipid bilayer properties induced by the Noble gases therefore providing a better description of key pathways for anesthetic action. [1] Sauguet et al. Plos One. 2016. doi: 10.1371/ journal.pone.0149795 [2] Laurent, Murail et al. Structure. 2016. doi: 10.1016/j.str.2016.02.014

Metal-organic frameworks (MOFs) are a family of chemically diverse materials, with applications in a wide range of fields, covering engineering, physics, chemistry, biology and medicine. Until recently, research has focused almost entirely on crystalline structures, yet now a clear trend is emerging, shifting the emphasis onto disordered states, including 'defective by design' crystals, as well as amorphous phases such as glasses and gels. Here we introduce a strongly associated MOF liquid, obtained by melting a zeolitic imidazolate framework. We combine in situ variable temperature X-ray, ex situ neutron pair distribution function experiments, and first-principles molecular dynamics simulations to study the melting phenomenon and the nature of the liquid obtained. We demonstrate from structural, dynamical, and thermodynamical information that the chemical configuration, coordinative bonding, and porosity of the parent crystalline framework survive upon formation of the MOF liquid.