Liquid metal–organic frameworks

Metal–organic frameworks 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 (ZIF). 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.This work benefitted from the financial support of ANRT (thèse CIFRE 2015/0268). We acknowledge access to HPC platforms provided by a GENCI grant (A0010807069). TDB would like to thank the Royal Society for a University Research Fellowship

Main hydrogen production processes: An overview

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

Intensification of TSA processes using a microwave-assisted regeneration step

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°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

Adsorption of N2O using Fe-13X zeolites - A Possibility to Make a Process Intensification by Using Microwaves for the Regeneration Step

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

Pt/re/ceo2 based catalysts for co‐water–gas shift reaction: From powders to structured catalyst

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)