Porous solids for biogas upgrading

In this work, we will present sorption equilibrium, kinetic and fixed bed data of CO2, CH4 in MOF-508b and zeolite 13X at 303, 323 and 343 K and partial pressures up to 4.5 bar. These data are fitted with appropriate isotherm models. At the same time single, binary and ternary breakthrough curves were measured to provide required data to develop and validate a mathematical model based on the LDF approximation for the mass transfer, which could be used in the design (simulation) of a cyclic adsorption processes (PSA) for the purification of biogas and CO2 sequestration

Adsorption technologies for BIOGAS upgrading and CO2 sequestration

Through this work it is shown that a new 13X zeolite can improve significantly the existing PSA technologies for BIOGAS upgrading with selectivities CO2/CH4 that can reach the value 34 and amounts adsorbed of CO2 around 5.2 mmol/g. A mathematical model was also developed and validated through experimental data to design PSA adsorption processes for biogas upgrading and CO2 sequestration.info:eu-repo/semantics/publishedVersio

Adsorption and separation of CO2/CH4 on binderless beads of 13X zeolite

The sorption equilibrium of CO2 and CH4 has been investigated on the binderless beads of 13X zeolite between 313 and 373 K and pressure up to 4 atm. The amount adsorbed of CO2 and CH4 is around 5.2 mmol/gads and 1.2 mmol/gads, respectively, at 313 K and 4 atm. Comparing these values with the ones in literature the value of CO2 is 20% higher than in similar 13X binder pellets

Letter to the editor

The authors of the open access article focus in section 3.2— “What can be measured and what can go Wrong” on the work of [1] to explain that a nonlinear ZLC under equilibrium control is very similar to a normal ZLC response in kinetic control and care must be taken in analyzing ZLC data.info:eu-repo/semantics/publishedVersio

Separation of Hexane Isomers in ZIF-8 by Fixed Bed Adsorption

The performance of porous metal organic framework ZIF-8 in the separation of all five hexane isomers (nC6, 2MP, 3MP, 23DMB, 22DMB) is evaluated through a series of multicomponent breakthrough adsorption experiments, at the temperatures of 373, 423, and 473 K and up to total hexane isomers pressure of 0.5 bar. The reported data show for all experiments the following sorption hierarchy: nC6 ≫ 2MP > 3MP ≫ 23DMB > 22DMB. At the temperature of 373 K and total hydrocarbon pressure of 0.5 bar the mixture loading of hexane isomers can go up to 2.15 mol·kg-1. In addition, at the same temperature the selectivities measured by the ratio of the loadings between linear plus monobranched (nC6, 2MP, 3MP) relatively to the dibranched (23DMB, 22DMB) isomers range between 34-55. The results also show that the sorption of nC6 is equilibrium based in contrast with the sorption of branched isomers which is kinetically controlled. The dibranched isomer 22DMB is practically excluded from the framework followed closely by 23DMB. The adsorption equilibrium experimental data are modeled by the Sips isotherm and the breakthrough data are simulated through a mathematical model developed in Matlab code using the method of lines (MOL), the results being in qualitative agreement. From the numerical simulations it was found that diffusivity of the branched paraffins in ZIF-8 is 2 orders of magnitude lower than for the linear nC6, and that the diffusivity of the dibranched paraffins is three times lower than for the monobranched ones. This work shows that ZIF-8 has the ability to purely separate the linear nC6 from its branched isomers and partially separate mono- from dibranched isomers if proper experimental conditions are setup, the result being important for the octane upgrade of gasoline.We acknowledge financial support from (1) Project ref POCI-01-0145-FEDER-016517 (PTDC/QEQ-PRS/3599/2014) funded by FEDER through COMPETE2020 and FCT; (2) AIProcMat@N2020 Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020, with the reference NORTE-01-0145-FEDER-000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF), and (3) by Project POCI-01-0145-FEDER-006984 Associate Laboratory LSRE-LCM funded by ERDF through COMPETE2020, Programa Operacional Competiti-vidade e Internacionalização (POCI), and by national funds through FCT Fundação para a Ciência e a Tecnologia.info:eu-repo/semantics/publishedVersio

Sorption and kinetics of CO2 and CH4 in binderless beads of 13X zeolite

The sorption equilibrium of CO2 and CH4 in binderless beads of 13X zeolite has been investigated between 313 and 373 K and pressure up to 4 atm. The amount adsorbed of CO2 and CH4 is around 5.2 mmol/gads and 1.2 mmol/gads, respectively, at 313 K and 4 atm. Comparing these values with the ones in literature the value of CO2 is 20% higher than in CECA 13X binder pellets. It is also found that isotherms are pronounced Type I for CO2 and almost linear for CH4. The CO2 isotherms were modeled using a simple deviation from Langmuir isotherm that takes into account interaction between adsorbed molecules at adjacent sites (Fowler model) suggesting a moderate repulsion. Henry’s constants range from 143 to 11.1 mmol/gads.atm for CO2 and 0.45 to 0.27 mmol/gads.atm for CH4 between 313 and 373 K, respectively. The heats of sorption at zero coverage are 43.1 kJ/mol for CO2 and 9.2 kJ/mol for CH4. The sorption kinetics has been investigated by the Zero-Length Column technique (ZLC). Recipes to analyze ZLC desorption curves in pellets of adsorbents are reviewed and it is derived a criteria which indicates that for the sorption rate be measured macroscopically the time of the experiment (that should be above a few seconds) is directly calculated with the following expression: t0:1 7:02 10 2 r2c Dc. Based on such criteria it is shown that crystal diffusivity of CO2 in 13X can be measured macroscopically by ZLC, being the same measurement for CH4 practically impossible. The crystal diffusivity of CO2 measured experimentally is 5.8 10 15 m2/s and 1.3 10 15 m2/s at 373 and 313 K, respectively. These values are comparable to the ones measured by a frequency response and pulse chromatography techniques reported in literature. The ZLC desorption curves for CH4 were measured under an equilibrium regim

Adsorption equilibrium and diffusion ofmethane and carbon dioxide on binderless beads of 13X zeolite

Equilibrium and kinetics of sorption of CO2 and CH4 on a new type of binderless on of 13X zeolite. The equilibrium data is measured in a breakthrough apparatus and the kinetic data by the ZLC technique

Separation of hexane isomers in metal-organic frameworks

In this work we study the effect of the functionalization of UiO-66(Zr) architecture with three different organic ligands: 2-aminoterephthalic acid (NH2-H2BDC), 2-nitroterephthalic acid (NO2-H2BDC) and 2-bromoterephthalic acid (Br-H2BDC) on the separation of hexane isomers by adsorption viewing the upgrading of TIP processes. The functionalized MOFs were synthesized and fully characterized applying established techniques: X-ray powder diffraction (XRPD), Infra-Red spectroscopy (IR), Thermo Gravimetric analysis (TGA) and nitrogen adsorption measurement. The potential of separation of the hexane isomers in the synthesized MOFs has been assessed by ISBN: 988-84-695-3536-3 T12-7 performing several screening studies in a breakthrough apparatus exploiting the effect of temperature and partial pressure, demonstrating that functionalization changes sorption behavior improving the separation between 22DMB and the other isomers. Figure 2 shows an experimental breakthrough curve performed in a bed packed with amino functionalized UiO-66 (UiO-66_NH2) where it can be seen that this material is able to separate high RON di-branched isomers (22DMB) from the low RON parents mono (3MP) and linear (nHEX) ones

Designing a simple volumetric apparatus for measuring gas adsorption equilibria and kinetics of sorption. Application and validation for CO

The screening of adsorbents (zeolites, MOFs, ACs, etc) requires the measurement of adsorption equilibria and kinetics at the milligram scale. In this regard, a volumetric apparatus (constant volume variable pressure – batch adsorber) has been developed for studying adsorption equilibria and kinetics of sorption. Its validation was accomplished by studying the adsorption equilibria of carbon dioxide (CO2), methane (CH4) and nitrogen (N2) and the kinetics of sorption of CO2 on commercial binder-free 4A zeolite. The data collected has an acceptable agreement with already published values by a gravimetric and breakthrough flow technique. The isotherms were modeled using Sips model from low pressure till 8 bar at 303, 343 and 373 K. The sorption kinetics of CO2 was measured from the uptake rate experiments and fitted with a solid-film linear-driving-force model (LDF). It was observed that the LDF mass transfer coefficients increase with pressure and temperature. Finally, the statistical analysis of the data was performed by Response Surface Methodology (RSM) to determine the interactions among process variables such as temperature and pressure in the respective gas adsorption equilibria data.Authors would like to acknowledge Kristin Gleichmann and Chemiewerk Bad Koestritz GmbH for kindly providing the binder-free beads of 4A zeolite. This work was financially supported by: 1) Project ′′VALORCOMP′′ (ref.0119_VALORCOMP_2_P), financed through INTERREG V A Spain Portugal (POCTEP) 2014-2020, under the European Regional Development Fund (ERDF). 2) Project POCI-01-0145- FEDER006984-Associate Laboratory LSRE-LCM funded by ERDF through COMPETE2020, Programa Operacional Competitividade e Internacionalizaç˜ao (POCI), and by national funds through Foundation for Science and Technology (FCT, Portugal) and ERDF under Programme PT2020 to CIMO (UID/AGR/00690/2019); 4) M. Karimi also recognizes a PhD research grant awarded by FCT –under SFRH/BD/ 140550/2018.info:eu-repo/semantics/publishedVersio