Pluton PULLUMBI - Academia.edu (original) (raw)

Papers by Pluton PULLUMBI

Metal-organic frameworks are chemically versatile materials, and excellent candidates for many ap... more 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.

Journal of Chemical Physics, Apr 8, 1995

Graphite oxide was silylated by dimethyloctylchlorosilane under various conditions. Silylated gra... more Graphite oxide was silylated by dimethyloctylchlorosilane under various conditions. Silylated graphite oxide was obtained and the maximum silicon content reached 0.17 mol/graphite oxide unit when the butylamine/dimethyloctylchlorosilane/graphite oxide unit ratio was about 19/16/1. The above maximum silicon content was much smaller than that obtained for graphite oxide silylated by octyltrichlorosilane, probably because of the steric hindrance of methyl groups against oxygen containing groups on the surface of graphite oxide. At the same time, the smaller amount of butylamine was needed to scavenge the HCl molecules formed as a byproduct, reflecting the smaller number of chlorine atom in the dimethyloctylchlorosilane molecule.

ChemInform, Jun 22, 2010

ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Le projet MISHY (2010-2014) a pour objectif le developpement de membranes de carbonitrure de sili... more Le projet MISHY (2010-2014) a pour objectif le developpement de membranes de carbonitrure de silicium permselectives a l’hydrogene obtenues par CVD assiste par plasma micro-ondes (MO-PECVD). Le consortium de ce projet est compose d’Air Liquide, coordinateur du projet, leader mondial des gaz industriels, d’IREIS HEF groupe specialise dans le traitement de surface par PVD et PECVD, de CTI, PME produisant des les ceramiques industrielles en particulier pour les applications de traitement des gaz, et de l’IEM, Institut Europeen des Membranes, qui a mene les premieres etudes prospectives sur ce type de membrane [1]. Au cours de ce projet, differentes tâches ont ete realisees : - conception et mise au point de supports tubulaires ceramiques a porosite asymetrique ; - conception et realisation d’un reacteur de laboratoire permettant de deposer une couche mince par PECVD sur un support tubulaire mesoporeux ; - transfert des resultats precedemment obtenus sur des membranes laboratoires par P...

Journal of Physical Chemistry C, Mar 12, 2018

DOAJ (DOAJ: Directory of Open Access Journals), Nov 1, 2022

Metal-organic frameworks (MOFs) are a family of chemically diverse materials, with applications i... more 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. Research so far has focused almost entirely on crystalline structures, yet a clear trend has emerged shifting the emphasis onto disordered states of MOFs, including "defective by design" crystals, as well as amorphous phases such as glasses and gels. Here we introduce a MOF liquid, a strongly associated liquid obtained by melting a zeolitic imidazolate framework (ZIF), with retention of chemical configuration, coordinative bonding modes, and porosity of the parent crystalline 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, focusing on structural characterization at the molecular scale, dynamics of the species, and thermodynamics of the solid-liquid transition. 2 Crystalline metal-organic frameworks have been proposed for application in a variety of situations which take advantage of their highly ordered and nanoporous structures, e.g. gas sorption and separation, 1-3 catalysis 4 and ion transport. 5 Inherent defects, 6 structural disorder 7 and nearubiquitous flexibility 8 present significant challenges in the development of highly robust, selective systems from perfect crystals. However, they also present opportunities, in creating functional "defective by design" materials. 9,10 Non-crystalline, or amorphous MOF systems are formed by avoidance of crystallization, or induced collapse of crystalline systems by pressure, temperature, or ball-milling. 11 In the case of the zeolitic imidazolate framework (ZIF) family, 12,13 which adopt similar structures to inorganic zeolites and are formed from M n+ (M n+ = e.g. Li + , B + , Zn 2+) inorganic nodes connected by Im based (Im = imidazolate, C 3 H 3 N − 2) ligands, such amorphous systems resemble the continuous random network of amorphous SiO 2. Recently, the formation of a molten ZIF state from a crystalline phase was observed in an inert argon atmosphere. No mass loss was observed during the formation of the liquid, which upon cooling yielded a melt-quenched glass, possessing an extended Zn-Im-Zn coordination network. 14 Unlike reversible solid-liquid transitions in 1D or 2D coordination polymers which occur below 500 K, 15 melting processes in ZIFs have only been observed at high temperatures, i.e. those exceeding 700 K. The novelty of the liquid and glass states means microscopic insight into the mechanism of melting, and the nature of the liquid produced are of great interest when considering the generality of the mechanism in the wider MOF family. However, thus far, the narrow temperature range and poorly understood kinetics-time stability of the fleeting liquid phase have precluded information on any liquid MOF state. Particularly salient and intriguing considerations pertaining to the liquid involve (i) "memory" of the crystalline framework conferred by remnant framework connectivity, (ii) coordinative framework dynamics and (iii) the proximity of structure to that of an ionic or a strongly associated liquid. 16 The ability to form hybrid "porous liquids", analogous to that of the organic systems of the Cooper and James groups, 17 would present a significant advance in the field, and help shift attention away from the solid state.

Catalysts, Nov 10, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Processes

Nitrous oxide (N2O) is considered the primary source of NOx in the atmosphere, and among several ... more 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...

Journal of the Chemical Society, 1998

HAL (Le Centre pour la Communication Scientifique Directe), May 26, 2019

International audienceAdsorption separation technology is a widely used technology for the separa... more International audienceAdsorption separation technology is a widely used technology for the separation and the purification of gases and liquids in a wide range of fields. Processes such as pressure swing adsorption (PSA) present an interesting tool for biogas upgrading. The performance of PSA process is controlled by many parameters such as number of beds, cycle step durations, pressure ratio, recycle rate and most importantly the nature and the characteristics of the adsorbent. The selection of an appropriate adsorbent for bio-methane production from biogas by pressure swing adsorption remains a key element for enhancing the performance of PSA technology. Reported experimental results on bio-methane, upgrade from biogas using PSA, show that the performance is highly dependent on the different used adsorbents. In order to rationalize the process of adsorbent selection for a given biogas feed composition, we have developed an approach based on numerical simulations, at the reactor level, of a PSA process used to upgrade the biogas in bio-methane with CH4 purity higher than 98%. These simulations were coupled to molecular-based simulation for optimizing the adsorbent that gives the best performance for a given feed composition. We use the optimal adsorbent characteristics for selecting available adsorbents having similar characteristics. In order to validate the selection of the adsorbents, a series of experimental tests ranging from pure component adsorption isotherms to breakthrough adsorption experiments are carried out together with dynamic flow conditions where the selected adsorbents are characterized using CO 2 /CH 4 gas mixtures. The effects of feed flow rate, number of beds, cycle step durations and purge-to-feed ratio are studied. The optimal operating parameters of the process are obtained from simulations. This cycle will be then tested in PSA pilot plants for biogas upgrading purposes

Reaction Engineering for Pollution Prevention, 2000

Publisher Summary This chapter examines the effects of oxygen enrichment of combustion air on the... more Publisher Summary This chapter examines the effects of oxygen enrichment of combustion air on the incinerator operational and environmental performances. The molecular electrostatic potentials were used as a tool to characterize the relative stabilities and reactive properties of a number of halogen substituted dibenzo-p-dioxins (“dioxins”) and dibenzo-furans (“furans”). Tests were done in two different configurations: second grate primary air enrichment and second and third grate primary air enrichment. In both configurations, the flue gas volume was kept constant. Standard gas analyses were performed in the boiler and the stack. Dioxins and furans samplings were done in the stack for six hours per sample. The analyses of the collected samples were done subsequently by the GC–MS technique. The result obtained during the tests on the incinerator was that the average dioxins and furans emissions were decreased by a factor of 3 when oxygen enrichment was used. The mechanisms of dioxins and furans formation observed were that the formation of propargyl radicals was an important pathway for their synthesis.

Adsorption, 2020

Gas separation by adsorption processes such as pressure swing adsorption (PSA) presents an attrac... more 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% CH 4) in industrial conditions (feed flow rate more than 500Nm 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 CH 4. 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% CH 4) of grid injection purity. The developed cycle allows a CH 4 recovery of 92% to be obtained with a specific energy consumption of 0.35kWh/Nm 3 , thus meeting the initial requirements for industrial exploitation of VPSA technology for biomethane purification from biogas sources.

Le travail a pour but l'amelioration des connaissances des hydrures des metaux du groupe 13 p... more Le travail a pour but l'amelioration des connaissances des hydrures des metaux du groupe 13 par une double approche de spectroscopie ir en matrice et de calculs quantiques. Ont ete identifiees les trois especes mh#n n=1, 2, 3 apres irradiation uv-visible selective d'agregats metal-hydrogene. La connaissance de la totalite de leur spectre vibrationnel ainsi que ceux de leurs varietes isotopiques h/d a permis de preciser leur structure et leur champ de force. Ces resultats experimentaux sont parfaitement corrobores par plusieurs types de calculs quantiques, parmi lesquels la methode dft se revele efficace et de moindre cout. D'autres hydrures ont ete caracterises de facon plus ou moins complete ; en particulier on s'est interesse a un tetrahydrure d'aluminium, de structure tetraedrique que les calculs demontrent etre en fait l'anion a1h#4 isoelectronique de sih#4. Des applications complementaires de la methode dft ont ete realisees sur des metaux carbonyles ant...

Separation and Purification Technology, 2022

Bulletin de la Société Chimique de France, 1996

Une nouvelle voie d'acces a des bis-polyazamacrocycles est decrite. Elle est realisee par con... more Une nouvelle voie d'acces a des bis-polyazamacrocycles est decrite. Elle est realisee par condensation d'un intermediaire N,N'N-triboctetraazamacrocycle ou N,N'-diboctriazamacrocycle avec un derive bis-electrophile de l'o-, m-, p-zylene, ou de l'anthracene. L'utilisation du groupement protecteur tert-butyloxycarbonyle (Boc), aisement elimine par action de HCl 6 M ou du TFA, permet d'obtenir les synthons proteges. Les derives bismacrocycliques pontes par un groupement anthracenyle ou o-zylenyle sont prepares au depart des precurseurs dichlorure d'acide : les diamides ainsi formes sont reduits par BH 3 -THF puis la deprotection est effectuee par un traitement acide. La N-alkylation des macrocycles proteges par le 1,3- ou 1,4-bis(bromomethyl)benzene conduit aux bis-macrocycles correspondants, et les composes cibles sont obtenus apres acidification du milieu. Des mesures par RPE de la distance spin-spin pour les complexes de cuivre ont ete effectuees ...

Microporous and Mesoporous Materials, 2019

The mass transfer coefficient is a fundamental property needed to design adsorption gas separatio... more 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.

Energies

N2O has a global warming potential about 300 times higher than CO2, and even if its contribution ... more 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 zeolite...

Metal--organic frameworks (MOFs) are a family of chemically diverse materials, with applications ... more 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. Research so far has focused almost entirely on crystalline structures, yet a clear trend has emerged shifting the emphasis onto disordered states of MOFs, including "defective by design" crystals, as well as amorphous phases such as glasses and gels. Here we introduce a MOF liquid, a strongly associated liquid obtained by melting a zeolitic imidazolate framework (ZIF), with retention of chemical configuration, coordinative bonding modes, and porosity of the parent crystalline 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, focusing on structural characterization at the molecular scale, dynamics of the sp...