Effect of lattice shrinking on the migration of water within zeolite LTA

\u3cp\u3eWater adsorption within zeolites of the Linde Type A (LTA) structure plays an important role in processes of water removal from solvents. For this purpose, knowing in which adsorption sites water is preferably found is of interest. In this paper, the distribution of water within LTA is investigated in several aluminum-substituted frameworks ranging from a Si:Al ratio of 1 (maximum substitution, framework is hydrophilic) to a Si:Al ratio of 191 (almost pure siliceous framework, it is hydrophobic). The counterion is sodium. In the hydrophobic framework, water is found in the large α-cages, whereas in the most hydrophilic frameworks, water is found preferably in the small β-cages. For frameworks with moderate aluminum substitution, β-cages are populated first, but at intermediate loading water favors α-cages instead. Framework composition and pressure therefore drive water molecules selectively towards α- or β-cages.\u3c/p\u3

Molecular Sieves for the Separation of Hydrogen Isotopes

International audienc

Molecular sieves for the separation of hydrogen isotopes

\u3cp\u3eStable molecular hydrogen isotopes, D\u3csub\u3e2\u3c/sub\u3e and T\u3csub\u3e2\u3c/sub\u3e, are both scarce and essential in several energy, industrial, and large-scale fundamental research applications. Due to the chemical similarity of these isotopes, their extraction and purification from hydrogen has relied for decades on expensive and energy-demanding processes. However, factoring in the phenomenon of quantum sieving could provide a new route for these separations. In this work, we have explored how to separate hydrogen isotopes by adsorption taking these quantum effects into account. To this end, we have conducted adsorption measurements to test our deuterium model and performed a widespread computational screening over 210 pure-silica zeolites for D\u3csub\u3e2\u3c/sub\u3e/H\u3csub\u3e2\u3c/sub\u3e and T\u3csub\u3e2\u3c/sub\u3e/H\u3csub\u3e2\u3c/sub\u3e separations. Based on low-coverage adsorption properties, a reduced set of zeolites have been singled out and their performance in terms of adsorption capacity, selectivity, and dynamic behavior have been assessed. Overall, the BCT-type zeolite clearly stands out for highly selective separations of both D\u3csub\u3e2\u3c/sub\u3e and T\u3csub\u3e2\u3c/sub\u3e over H\u3csub\u3e2\u3c/sub\u3e, achieving the highest reported selectivities at cryogenic temperatures. We also identified other interesting zeolites for the separation of hydrogen isotopes that offer an alternative way to tackle similar isotopic separations by an aimed selection or design of porous materials.\u3c/p\u3

Zeolites for CO\u3csub\u3e2\u3c/sub\u3e-CO-O\u3csub\u3e2\u3c/sub\u3e separation to obtain CO\u3csub\u3e2\u3c/sub\u3e-neutral fuels

\u3cp\u3eCarbon dioxide release has become an important global issue due to the significant and continuous rise in atmospheric CO\u3csub\u3e2\u3c/sub\u3e concentrations and the depletion of carbon-based energy resources. Plasmolysis is a very energy-efficient process for reintroducing CO\u3csub\u3e2\u3c/sub\u3e into energy and chemical cycles by converting CO\u3csub\u3e2\u3c/sub\u3e into CO and O\u3csub\u3e2\u3c/sub\u3e utilizing renewable electricity. The bottleneck of the process is that CO remains mixed with O\u3csub\u3e2\u3c/sub\u3e and residual CO\u3csub\u3e2\u3c/sub\u3e. Therefore, efficient gas separation and recuperation are essential for obtaining pure CO, which, via water gas shift and Fischer-Tropsch reactions, can lead to the production of CO\u3csub\u3e2\u3c/sub\u3e-neutral fuels. The idea behind this work is to provide a separation mechanism based on zeolites to optimize the separation of carbon dioxide, carbon monoxide, and oxygen under mild operational conditions. To achieve this goal, we performed a thorough screening of available zeolites based on topology and adsorptive properties using molecular simulation and ideal adsorption solution theory. FAU, BRE, and MTW are identified as suitable topologies for these separation processes. FAU can be used for the separation of carbon dioxide from carbon monoxide and oxygen and BRE or MTW for the separation of carbon monoxide from oxygen. These results are reinforced by pressure swing adsorption simulations at room temperature combining adsorption columns with pure silica FAU zeolite and zeolite BRE at a Si/Al ratio of 3. These zeolites have the added advantage of being commercially available.\u3c/p\u3

Potential of CO2 capture from flue gases by physicochemical and biological methods: a comparative study

The industrial viability of two emerging technologies for CO2 capture from flue gases, i.e., adsorption in porous commercial zeolites and biomass production by microalgae, is compared. Our study is organized in two steps: first, the best system is selected (either zeolite type or microalgae strain). Second, their performance is quantified and their advantages at real conditions discussed. For the physicochemical process, we find that commercial zeolite MFI is the best choice for CO2 capture from a typical industrial flue gas emission. Numerical dual PSA cycle simulations at ambient conditions yield 8 kg m-3 bed h-1 and an energy consumption of 0.987 MJ per kg of captured CO2. As regards the biological process, evaluation of several microalgae strains in continuous mode using low cost resources (waste water, fertilizers, flue gases), results in Scenedesmus almeriensis as the most promising strain. The maximal capacity of CO2 capture at laboratory conditions was 0.1 kg m-3 h -1 , allowing to produce up to 0.06 of kg m-3 h -1 of biomass (3% maximal photosynthetic efficiency). Although this is a significantly lower value, the produced biomass, being composed by carbohydrates, entails an overall economic yield of 0.6 € m- 3 ·day. To demonstrate reliability at large scale, experiments were performed in a 100 m2 pilot raceway reactor under outdoor conditions. We measured 54 g of CO2/m2 ·day (= 197 tn/ha·year) and a biomass productivity of 21 g/m2·day (= 75 tn/ha·year). The energy consumption approaches to 0.48 MJ/kgCO2, lower than zeolites adsorption. Still, zeolites can be advantageous as they offer higher productivity, lower energy consumption than amines-based methods, and possibility of producing added-value chemical products, such as methanol, CO or CH4

Potential of CO2 capture from flue gases by physicochemical and biological methods: A comparative study

We compare the industrial viability of two emerging technologies for CO2 capture from flue gases, i.e., adsorption in porous commercial zeolites and biomass production by microalgae. Our study is organized in two steps: first, the best system is selected (either zeolite type or microalgae strain). Second, their performance is quantified and their advantages at real conditions discussed. For the physicochemical process, we find that commercial zeolite MFI is the best choice for CO2 capture from a typical industrial flue gas emission. Numerical dual PSA cycle simulations at ambient conditions yield 8 kg m−3 bed h−1 and an energy consumption of 0.987 MJ per kg of captured CO2. As regards the biological process, evaluation of several microalgae strains in continuous mode using low-cost resources (waste water, fertilizers, flue gases), results in Scenedesmus almeriensis as the most promising strain. The maximal capacity of CO2 capture at laboratory conditions was 0.1 kg m−3h−1, allowing to produce up to 0.06 of kg m−3h−1 of biomass (3% maximal photosynthetic efficiency). Although this is a significantly lower value, the produced biomass, being composed by carbohydrates, entails an overall economic yield of 0.6 € m−3·day. To demonstrate reliability at large scale, experiments were performed in a 100 m2 pilot raceway reactor under outdoor conditions. We measured 54 g of CO2/m2·day (=197 tn/ha·year) and a biomass productivity of 21 g/m2·day (=75 tn/ha·year). The energy consumption approaches to 0.48 MJ/kgCO2, lower than zeolites adsorption. Still, zeolites can be advantageous as they offer higher productivity, lower energy consumption than amines-based methods, and possibility of producing added-value chemical products, such as methanol, CO or CH4

Zeolites for CO2-CO-O2 separation to obtain CO2-neutral fuels

Carbon dioxide release has become an important global issue due to the significant and continuous rise in atmospheric CO2 concentrations and the depletion of carbon-based energy resources. Plasmolysis is a very energy-efficient process for reintroducing CO2 into energy and chemical cycles by converting CO2 into CO and O2 utilizing renewable electricity. The bottleneck of the process is that CO remains mixed with O2 and residual CO2. Therefore, efficient gas separation and recuperation are essential for obtaining pure CO, which, via water gas shift and Fischer-Tropsch reactions, can lead to the production of CO2-neutral fuels. The idea behind this work is to provide a separation mechanism based on zeolites to optimize the separation of carbon dioxide, carbon monoxide, and oxygen under mild operational conditions. To achieve this goal, we performed a thorough screening of available zeolites based on topology and adsorptive properties using molecular simulation and ideal adsorption solution theory. FAU, BRE, and MTW are identified as suitable topologies for these separation processes. FAU can be used for the separation of carbon dioxide from carbon monoxide and oxygen and BRE or MTW for the separation of carbon monoxide from oxygen. These results are reinforced by pressure swing adsorption simulations at room temperature combining adsorption columns with pure silica FAU zeolite and zeolite BRE at a Si/Al ratio of 3. These zeolites have the added advantage of being commercially available

Comparison of depopulation and S19‐RB51 vaccination strategies for control of bovine brucellosis in high prevalence areas

E-mail for correspondence: [email protected] vaccination can minimise the diagnostic problems associated with S19 vaccination of adult cattle, but its use for bovine brucellosis (BB) control remains controversial. Here, the evolution of BB prevalence in five high prevalence areas in Spain subjected to different control measures is described: herd depopulation of infected herds (I–III) or mass vaccination with RB51 and S19‐RB51 vaccination of replacement heifers (IV–V). Annual data from the eradication campaigns were analysed at the special incidence area (SIA) level and the time to obtain herd prevalence levels of <1 per cent (‘controlled status’) was obtained at the local veterinary unit (LVU) level and compared using Cox's proportional hazard model. A higher annual rate of decrease in herd prevalence was observed in the SIAs subjected to vaccination (46.9%, 95% CI 43.5% to 50.0%) compared with those managed using stamping out (14.9%, 95% CI 9.6% to 19.9%). No significant differences in the time to achieve controlled status were observed between the stamping‐out and vaccination strategies used at the LVU level, with median times of 60 (stamping‐out LVUs) and 63 (vaccination LVUs) months. These results suggest that RB51 mass vaccination, in combination with the S19‐RB51 vaccination of replacement heifers and strict implementation of other eradication measures, may provide results at least comparable with those resulting from a herd depopulation based strategy.Depto. de Sanidad AnimalCentro de Vigilancia Sanitaria Veterinaria (VISAVET)Fac. de VeterinariaTRUEpu