scholarly journals A Contribution to the Experimental Microkinetic Approach of Gas/Solid Heterogeneous Catalysis: Measurement of the Individual Heats of Adsorption of Coadsorbed Species by Using the AEIR Method

Catalysts ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 265 ◽  
Author(s):  
Daniel Bianchi
Keyword(s):  
Adsorption Equilibrium ◽  
Adsorption Models ◽  
Heats Of Adsorption ◽  
Elementary Steps ◽  
Mathematical Expressions ◽  
Adsorption Temperature ◽  
Adsorption Of Co ◽  
The Individual ◽  
Adsorption Desorption ◽  
Ir Bands

The two first surface elementary steps of a gas/solid catalytic reaction are the adsorption/desorption at least one of the reactants leading to its adsorption equilibrium which can be or not disturbed by the others surface elementary steps leading to the products. The variety of the sites of a conventional catalyst may lead to the formation of different coadsorbed species such as linear, bridged and threefold coordinated species for the adsorption of CO on supported metal particles. The aim of the present article is to summarize works performed in the last twenty years for the development and applications of an analytical method named Adsorption Equilibrium InfraRed spectroscopy (AEIR) for the measurement of the individual heats of adsorption of coadsorbed species and for the validation of mathematical expressions for their adsorption coefficients and adsorption models. The method uses the evolution of the IR bands characteristic of each of coadsorbed species during the increase in the adsorption temperature in isobaric conditions. The presentation shows that the versatility of AEIR leads to net advantages as compared to others conventional methods particularly in the context of the microkinetic approach of catalytic reactions.

Thermo-kinetic investigation of heavy metal ions adsorption onto lignin considering coupled adsorption–desorption mechanisms: Modeling and experimental validation

2018 ◽  
Vol 09 (02) ◽  
pp. 1850014
Author(s):  
Farnaz Seyedvakili ◽  
Mohammad Samipoorgiri
Keyword(s):  
Heavy Metal ◽  
Metal Ions ◽  
Heavy Metal Ions ◽  
Individual Characteristics ◽  
Adsorption And Desorption ◽  
Isotherm Equation ◽  
Proposed Model ◽  
Isotherm And Kinetic Models ◽  
The Individual ◽  
Adsorption Desorption

A coupled adsorption–desorption thermo-kinetic model is developed incorporating both adsorption and desorption reactions. A local pseudo-equilibrium condition at the interface of adsorbent and adsorbate bulk phases was used as isotherm equation which can even be applied for multi-pollutants scenarios. The developed model is then validated using collected experimental data of heavy metal ions (Pb, Cu, Cd, Zn, and Ni). Comparisons were made for a number of isotherm and kinetic models to examine the performance of the proposed model. The developed model revealed desirable accuracy and superiority over other models in predicting the adsorption behavior and can be used for other systems of concern. The model correlates the adsorption kinetic with an [Formula: see text] value of 0.9391 and desorption kinetic with an [Formula: see text] value of 0.9383. By application of the proposed model to any available adsorption datasets, the individual characteristics of adsorption and desorption can be determined.

Absorption Equilibrium and Thermodynamics of Fenugreek Yellow Pigment on Macroporous Resins

2011 ◽  
Vol 233-235 ◽  
pp. 91-94
Author(s):  
Feng Han ◽  
Wen Hong Li ◽  
Xuan Tang ◽  
Dong Li
Keyword(s):  
Free Energy ◽  
Thermodynamic Parameters ◽  
Gibbs Free Energy ◽  
Adsorption Equilibrium ◽  
Yellow Pigment ◽  
Adsorption Models ◽  
Freundlich Model ◽  
Langmuir Adsorption ◽  
Macroporous Resins ◽  
Equilibrium Data

The adsorption equilibrium and thermodynamics of pigment extracted from Fenugreek after degumming on macroporous resins was investigated under differentinitial concentrations. The suitability of the Freundlich and Langmuir adsorption models to the equilibrium data was investigated. The model fitness was determined by R2 . Thermodynamic parameters were calculated by the Van’t Hof equation.The results showed that Freundlich model gave a better fit of adsorption isotherms than Langmuir models. The positive value of enthalpy(∆H) indicated that the adsorption was endothermic, the negative value of Gibbs free energy (∆G) showed the spontaneous and favoured nature of adsorption, and the entropy(∆S) was positive.The resins LS-46 showed an effective adsorbtion for Fenugreek yellow pigment.

Heterogeneous Interactions of Methylamines on porous Adsorbents Part II. Interactions on Silica–Alumina and Silica Gel Surfaces of Di- and Tri-methylamine in the Region of their Boiling Points

1972 ◽  
Vol 50 (15) ◽  
pp. 2451-2456 ◽  
Author(s):  
W. G. Cook ◽  
R. A. Ross
Keyword(s):  
Silica Gel ◽  
Surface Coverage ◽  
Adsorbed Layer ◽  
Silica Gels ◽  
Heats Of Adsorption ◽  
Boiling Points ◽  
Silica Alumina ◽  
Desorption Isotherms ◽  
Adsorption Desorption ◽  
Heterogeneous Interactions

The adsorption of di- and tri-methylamine has been studied at 280 and 276°K, respectively, on a range of silica gels and on silica–alumina. Adsorption–desorption isotherms and isothermal calorimetric heats of adsorption were measured. Heats of adsorption for di-methylamine on silica gel varied from 29.0 kcal/mol at θ = 0.05 to 12.0 kcal/mol at monolayer completion, while for silica–alumina the heats fell from 31.4 to 9.0 kcal/mol between these same values of surface coverage. For tri-methylamine on silica gel, heats fell from 21.0, θ = 0.05, to 10.3 kcal/mol, θ = 1.00, while heats of 21.4 and 9.9 kcal/mol, respectively, were found at these same surface coverages on silica–alumina. The values of the heats of adsorption are discussed in terms of interactions in the adsorbed layer which are believed to be influenced by the pore sizes in the adsorbent and by the basicity of the amine molecules.

Highly optimized CO2 capture by inexpensive nanoporous covalent organic polymers and their amine composites

2015 ◽  
Vol 183 ◽  
pp. 401-412 ◽  
Author(s):  
Hasmukh A. Patel ◽  
Cafer T. Yavuz
Keyword(s):  
Flue Gas ◽  
Gas Flow ◽  
Low Cost ◽  
High Specific Surface Area ◽  
Organic Polymers ◽  
Mixed Gas ◽  
Gas Streams ◽  
Promising Application ◽  
Adsorption Of Co ◽  
Adsorption Desorption

Carbon dioxide (CO2) storage and utilization requires effective capture strategies that limit energy penalties. Polyethylenimine (PEI)-impregnated covalent organic polymers (COPs) with a high CO2 adsorption capacity are successfully prepared in this study. A low cost COP with a high specific surface area is suitable for PEI loading to achieve high CO2 adsorption, and the optimal PEI loading is 36 wt%. Though the adsorbed amount of CO2 on amine impregnated COPs slightly decreased with increasing adsorption temperature, CO2/N2 selectivity is significantly improved at higher temperatures. The adsorption of CO2 on the sorbent is very fast, and a sorption equilibrium (10% wt) was achieved within 5 min at 313 K under the flow of simulated flue gas streams. The CO2 capture efficiency of this sorbent is not affected under repetitive adsorption–desorption cycles. The highest CO2 capture capacity of 75 mg g−1 at 0.15 bar is achieved under dry CO2 capture however it is enhanced to 100 mg g−1 in the mixed gas flow containing humid 15% CO2. Sorbents were found to be thermally stable up to at least 200 °C. TGA and FTIR studies confirmed the loading of PEIs on COPs. This sorbent with high and fast CO2 sorption exhibits a very promising application in direct CO2 capture from flue gas.

scholarly journals Characterizations and Application of Supported Ionic Liquid [bmim][CF3SO3]/SiO2 in CO2 Capture

2017 ◽  
Vol 888 ◽  
pp. 485-490
Author(s):  
Tengku Sharifah Marliza ◽  
Mohd Ambar Yarmo ◽  
Azizul Hakim ◽  
Maratun Najiha Abu Tahari ◽  
Yun Hin Taufiq-Yap
Keyword(s):  
Ionic Liquid ◽  
Atmospheric Pressure ◽  
Gas Adsorption ◽  
Chemical Properties ◽  
Industrial Applications ◽  
Supported Ionic Liquid ◽  
Adsorption Of Co ◽  
Adsorption Desorption ◽  
Physical And Chemical ◽  
And Chemical Properties

Supported ionic liquid (IL) [bmim][CF3SO3] on SiO2 was prepared, characterized and its potential evaluated for CO2 capture via adsorption and desorption studies using gas adsorption analyzer. The physical and chemical properties were determined using N2 adsorption/desorption and CO2-TPD analysis. The increasing IL loading caused a drastic decrease in the surface area as well as pore volume due to the confinement of IL within the micropore and mesopore area. However, the increasing IL loading increased the basicity of the sorbent which significantly enhanced CO2 chemisorption. Supported [bmim][CF3SO3] on SiO2 revealed the physical and chemical adsorption of CO2 and resulted in a remarkable CO2 adsorption capacity at atmospheric pressure and room temperature (66.7 mg CO2/gadsorbent) which has great potential in industrial applications.

scholarly journals Modification to L-H Kinetics Model and Its Application in the Investigation on Photodegradation of Gaseous Benzene by Nitrogen-Doped TiO2

Catalysts ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 326 ◽  
Author(s):  
Peng Sun ◽  
Jun Zhang ◽  
Wenxiu Liu ◽  
Qi Wang ◽  
Wenbin Cao
Keyword(s):  
Adsorption Equilibrium ◽  
Illumination Intensity ◽  
Desorption Process ◽  
Doped Tio2 ◽  
Coverage Ratio ◽  
Nitrogen Doped ◽  
Desorption Equilibrium ◽  
Adsorption Desorption ◽  
Kinetics Of ◽  
Gaseous Benzene

In this paper, the Langmuir-Hinshelwood (L-H) model has been used to investigate the kinetics of photodegradation of gaseous benzene by nitrogen-doped TiO2 (N-TiO2) at 25 °C under visible light irradiation. Experimental results show that the photoreaction coefficient kpm increased from 3.992 × 10−6 mol·kg−1·s−1 to 11.55 × 10−6 mol·kg−1·s−1 along with increasing illumination intensity. However, the adsorption equilibrium constant KL decreased from 1139 to 597 m3·mol−1 when the illumination intensity increased from 36.7 × 104 lx to 75.1 × 104 lx, whereas it was 2761 m3·mol−1 in the absence of light. This is contrary to the fact that KL should be a constant if the temperature was fixed. This phenomenon can be attributed to the breaking of the adsorption-desorption equilibrium by photocatalytically decomposition. To compensate for the disequilibrium of the adsorption-desorption process, photoreaction coefficient kpm was introduced to the expression of KL and the compensation form was denoted as Km. KL is an indicator of the adsorption capacity of TiO2 while Km is only an indicator of the coverage ratio of TiO2 surface. The modified L-H model has been experimentally verified so it is expected to be used to predict the kinetics of the photocatalytic degradation of gaseous benzene.

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