scholarly journals STUDY OF CARBON DIOXIDE ADSORPTION ON CHROMOXIDE CATALYST ON NON-STATIONARY CONCENTRATIONS

2018 ◽  
Vol 61 (7) ◽  
pp. 37 ◽  
Author(s):  
Nikolay I. Kol'tsov ◽  
Vladislav Kh. Fedotov
Keyword(s):  
Experimental Data ◽  
Carbon Dioxide ◽  
Chemical Kinetics ◽  
Carbon Dioxide Adsorption ◽  
Dissociative Mechanism ◽  
Simple Method ◽  
Desorption Process ◽  
Adsorption And Desorption ◽  
Additional Information ◽  
Adsorption Desorption

Investigation of the regularities of chemical processes, not only near but also far from the stationary state, gives additional information on their mechanisms. In this paper, we present a new method for estimating rate constants of adsorption-desorption processes from the experimentally measured values of the nonstationary concentrations of an adsorbed substance, based on calculating the instantaneous rates of the adsorption (or desorption) process. This method allows to connect unknown kinetic parameters of adsorption (desorption) of a substance on the catalyst surface for various most probable assumed mechanisms with the calculated values of the instantaneous rates of adsorption-desorption processes. As a consequence, the method makes it possible to solve two types of inverse problems of chemical kinetics: calculate point and interval values of rates constants of adsorption and desorption; determine the most likely mechanism from several proposed mechanisms of implementation of these processes. Using this method, point and interval values of the rates constants of adsorption and desorption of carbon dioxide were determined on the base of nonstationary experimental data on adsorption on the assumption of carbon dioxide adsorption on a chromoxide catalyst to three proposed mechanisms: linear, bimolecular and dissociative. Based on the results of calculations, the corresponding non-stationary dependences of carbon dioxide adsorption were restored, which were compared with the experimental data. The obtained results confirm that the previously established dissociative mechanism of adsorption of carbon dioxide on the chromoside catalyst is the most probable. The developed simple method does not require the use of complex optimization calculations and can be used to solve the inverse problem of chemical kinetics associated with the determination of mechanisms and the estimation of the rates constants of adsorption and desorption of substances on various catalysts.Forcitation:Kol’tsov N.I., Fedotov V.Kh. Study of carbon dioxide adsorption on chromoxide catalyst on non-stationary concentrations. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 7. P. 37-42

Diamine-Functionalization of a Metal-Organic Framework Adsorbent for Superb Carbon Dioxide Adsorption and Desorption Properties

ChemSusChem ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1694-1707 ◽  
Author(s):  
Woo Ram Lee ◽  
Jeong Eun Kim ◽  
Sung Jin Lee ◽  
Minjung Kang ◽  
Dong Won Kang ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Metal Organic Framework ◽  
Carbon Dioxide Adsorption ◽  
Adsorption And Desorption ◽  
Metal Organic ◽  
Organic Framework

scholarly journals Using An Exponential Equation to Describe Adsorption/Desorption Processes of Water on Composite Soil at Constant Pressure

2003 ◽  
Vol 21 (4) ◽  
pp. 383-388
Author(s):  
Lianxi Ma ◽  
James C. Holste ◽  
Kenneth R. Hall
Keyword(s):  
Experimental Data ◽  
Water Vapour ◽  
Constant Pressure ◽  
Exponential Equation ◽  
Desorption Process ◽  
Experimental Time ◽  
Long Time ◽  
Experimental Values ◽  
Adsorption Desorption

Using the assumption that adsorption as a function of time may be expressed by an exponential equation, viz. ΔM = g + he−t/τ, it is possible to obtain the amount of water vapour adsorbed by a composite soil without waiting for equilibrium, which usually takes a long time. Given the experimental data for the amounts adsorbed versus time, one can determine g, h and τ, together with the amounts adsorbed at equilibrium by extrapolating the above equation to t → ∞. It is also possible to calculate the error trends in these parameters as a function of time by comparing the values at time t with those obtained for the longest experimental time. The error trends of the equation with time arise from the comparison of the experimental values with those predicted by the exponential equation. We have discovered that although different lengths of time are necessary for different pressures, generally a time between 1.5τ and 2τ is sufficient to obtain reliable results with errors less than 5%. We have also found that this equation describes the desorption process as well.

scholarly journals Description of Carbon Dioxide Adsorption and Desorption onto Malaysian Coals under Subcritical Condition

2016 ◽  
Vol 148 ◽  
pp. 600-608 ◽  
Author(s):  
Mustafa Abunowara ◽  
Mohamad Azmi Bustam ◽  
Suriati Sufian ◽  
Usama Eldemerdash
Keyword(s):  
Carbon Dioxide ◽  
Carbon Dioxide Adsorption ◽  
Adsorption And Desorption ◽  
Subcritical Condition

scholarly journals Technical Note: Classical and statistical thermodynamic treatment of adsorption and desorption kinetics and rates

2021 ◽  
Author(s):  
Daniel A. Knopf ◽  
Markus Ammann
Keyword(s):  
Chemical Kinetics ◽  
Surface Coverage ◽  
Aerosol Particles ◽  
Statistical Thermodynamic ◽  
Desorption Kinetics ◽  
Desorption Energy ◽  
Desorption Process ◽  
Adsorption And Desorption ◽  
The Impact ◽  
Standard States

Abstract. Adsorption and desorption represent the initial processes of the interaction of gas species with the condensed phase. It has important implications for evaluating heterogeneous (gas-to-solid) and multiphase chemical kinetics involved in catalysis, environmental interfaces, and, in particular, aerosol particles. When describing gas uptake, gas-to-particle partitioning, and the chemical transformation of aerosol particles the desorption lifetime is a crucial parameter to assess the underlying chemical kinetics such as surface reaction and surface-to-bulk transfer. The desorption lifetime, in turn, depends on the desorption free energy which is affected by the chosen adsorbate model and standard states. To assess the impact of those conditions on desorption energy and, thus, desorption lifetime, we provide a complete classical and statistical thermodynamic treatment of the adsorption and desorption process considering transition state theory for two typically applied adsorbate models, the 2D ideal gas and the 2D ideal lattice gas, the latter being equivalent to Langmuir adsorption. Both models apply to solid and liquid substrate surfaces. We derive the thermodynamic and microscopic relationships for adsorption and desorption equilibrium constants, adsorption and desorption rates, first-order adsorption and desorption rate coefficients, and the corresponding pre-exponential factors. Although, some of these derivations can be found in the literature, this study aims to bring all derivations into one place to facilitate the interpretation and analysis of desorption energies for their application in multiphase chemical kinetics. This exercise allows for a microscopic interpretation of the underlying processes including the surface accommodation coefficient and highlights the importance of the choice of adsorbate model and standard states when analyzing and interpreting adsorption and desorption processes. We demonstrate how the choice of adsorbate model choice affects equilibrium surface concentrations and coverages, desorption rates, and decay of the adsorbate species with time. In addition, we show how those results differ when applying a concentration- or activity-based description. Our treatment demonstrates that the pre-exponential factor can differ by orders of magnitude depending on the choice of adsorbate model with similar effects on the desorption lifetime, yielding significant uncertainties in the desorption energy. Furthermore, uncertainties in surface coverage and assumptions in standard surface coverage can lead to significant changes in desorption energies derived from measured desorption rates. Providing a comprehensive thermodynamic and microscopic representation aims to guide theoretical and experimental assessments of desorption energies and estimate potential uncertainties in applied desorption energies and corresponding desorption lifetimes important for improving our understanding of multiphase chemical kinetics.

scholarly journals Utilization of spent dregs for the production of activated carbon for CO2 adsorption

2017 ◽  
Vol 19 (2) ◽  
pp. 44-50 ◽  
Author(s):  
Jarosław Serafin
Keyword(s):  
Carbon Dioxide ◽  
Activated Carbon ◽  
Density Functional ◽  
Activated Carbons ◽  
Density Functional Theory Method ◽  
Textural Properties ◽  
Carbon Dioxide Adsorption ◽  
Functional Theory ◽  
Surface Areas ◽  
Adsorption Desorption

Abstract The objective of this work was preparation of activated carbon from spent dregs for carbon dioxide adsorption. A saturated solution of KOH was used as an activating agent. Samples were carbonized in the furnace at the temperature of 550°C. Textural properties of activated carbons were obtained based on the adsorption-desorption isotherms of nitrogen at −196°C and carbon dioxide at 0°C. The specific surface areas of activated carbons were calculated by the Brunauer – Emmett – Teller equation. The volumes of micropores were obtained by density functional theory method. The highest CO2 adsorption was 9.54 mmol/cm3 at 0°C – and 8.50 mmol/cm3 at 25°C.

Characterising the Differences between the Adsorption and Desorption Processes in a Desiccant Layer by Detailed Numerical Modelling

2012 ◽  
Vol 326-328 ◽  
pp. 690-695
Author(s):  
C.R. Ruivo ◽  
J.J. Costa ◽  
A.R. Figueiredo
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Channel Wall ◽  
Water Adsorption ◽  
Sorption Isotherms ◽  
Transfer Coefficients ◽  
Desorption Process ◽  
Adsorption And Desorption ◽  
Adsorption Desorption ◽  
Simultaneous Heat

In this paper, the performance of a channel element of a hygroscopic matrix is evaluated by detailed numerical modeling. The adopted physical model takes into account the gas-side and solid-side resistances to heat and mass transfer, as well as the simultaneous heat and mass transfer occurring simultaneously with the water adsorption/desorption process in the desiccant porous channel wall domain. The desiccant medium is silica gel RD, the equilibrium being characterized by sorption isotherms. Appropriate convective transfer coefficients are taken into account for the calculation of the heat and mass transfer phenomena between the airflow and the channel wall. The response of the channel element to a step change in the airflow states is simulated, the results enabling the investigation of some differences between the adsorption and desorption processes.

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