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Adsorption: Journal of the International Adsorption Society (v.16, #6)
Doug Ruthven and Jörg Kärger: Their individual and collective contributions to the field of zeolite science and engineering by Dhananjai B. Shah (pp. 497-509).
Prof. Doug Ruthven and Prof. Jörg Kärger are two giants in the field of zeolite science and engineering. Over their academic careers encompassing almost forty years each, they have contributed significantly to the advancement of fundamental understanding of adsorption and diffusion in zeolites as well as their industrial applications. The author, in the beginning of his academic career, had an opportunity to spend two years as a post-doctoral fellow in Prof. Ruthven’s laboratory at the University of New Brunswick (1975–1977). This experience actually motivated me to spend my academic career in working in the field of zeolite adsorption and diffusion. Nearly thirty years later, I spent a year as a Gast Mercator Professor at the University of Leipzig in the laboratory of Prof. Kärger (2005–2006). These two opportunities at two different ends of my academic career provided me with unique perspectives to reflect on the important contributions made by Professors Ruthven and Kärger to the field of zeolite science and technology. This article summarizes my personal perspectives on the breadth and depth of their contributions.
Keywords: Prof. D.M. Ruthven; Prof. J. Kärger; Adsorption; Diffusion; Zeolites; Adsorption processes
Imaging of transient guest profiles in nanoporous host materials: a new experimental technique to study intra-crystalline diffusion by Christian Chmelik; Jörg Kärger (pp. 515-523).
The application of interference microscopy (IFM) and infrared microscopy (IRM) to monitoring transient concentration profiles during uptake and release of guest molecules in nanoporous materials has opened a novel technique for diffusion studies with adsorbed molecules. For the first time, the coefficients of transport diffusion and the surface permeabilities have become accessible by direct observation under non-equilibrium conditions. The examples presented in this communication include diffusion and permeation measurements with zeolites of the ferrierite type and with metal-organic frameworks (MOFs) of type ZIF-8
Keywords: Diffusion; Zeolites; MOFs; PFG NMR; Interference microscopy; IR microscopy
Studies of C8 aromatics adsorption in BaY and mordenite molecular sieves using the headspace technique by F. Murilo T. Luna; Juliana A. Coelho; J. Carlos F. Otoni; Artemis P. Guimarães; Diana C. S. Azevedo; Célio L. Cavalcante Jr. (pp. 525-530).
A headspace technique, that consists in analyzing the composition of the vapor phase in equilibrium with the condensed phase of a mixture in a sealed vial containing the adsorbent sample, has been recently applied to acquire equilibrium data for adsorption of xylenes in liquid phase. In this study, we used this technique to measure experimental binary equilibrium data for C8 aromatics in Y and mordenite zeolitic molecular sieves. For the Y zeolite, we also measured C8 aromatics quaternary equilibrium data. Measurements were made at temperatures between C 40–80 °C. A more tedious, but traditional, chromatographic pulses method was also used to validate some of the results.
Keywords: Xylenes; Adsorption; Headspace; Selectivity; Y zeolite; Mordenite
Characterization of the diffusion path in micro- and meso-porous materials from ZLC analysis by Qinglin Huang; Mladen Eić; Huining Xiao; Serge Kaliaguine (pp. 531-539).
It has been demonstrated that the main diffusion paths of micro- and meso-porous UL-zeolites could be characterized from the Zero Length Column (ZLC) desorption curves with an appropriate theoretical analysis (Malekian et al., in Ind. Eng. Chem. Res. 46:5067, 2007). The present work extends this method to study the ZLC desorption data of n-heptane/cumene/mesitylene in three mesoporous SBA-15 samples, 1-methylnaphthalene in MCM-48, cumene in SBA-16 and toluene/cumene in a microporous one-dimensional boron SSZ-42. The investigation results revealed that the structure of SBA-15, MCM-48 and SBA-16 behaved approximately as three-dimensional (isotropic) diffusion system, while SSZ-42 behaved as one-dimensional (anisotropic) diffusion systems. The diffusion path did not change within the measured temperature range, and by using different sorbate molecules. This work confirmed that this effective and relatively inexpensive method can be used as an additional tool for the characterization of porous materials.
Keywords: Micro- and meso-porous material; Diffusion path, ZLC technique
Adsorption of N-hydrocinnamoyl-N-phenylhydroxylamine on pure minerals by Ramanathan Natarajan; Jatin Sharma; Inderjit Nirdosh (pp. 541-548).
Equilibrium adsorption studies of N-hydrocinnamoyl-N-phenylhydroxylamine (HCNPHA) on galena, sphalerite, pyrite, chalcopyrite and quartz at pH 9 and 10 are reported. All adsorption isotherms followed Langmuir model, however, Freundlich type was observed for quartz. As HCNPHA is a strong chelating agent, formation of monolayers by chemisorption appeared to be the most probable mechanism of adsorption on the base-metal sulphide minerals. Specific adsorption of HCNPHA on iron containing minerals, namely, chalcopyrite and pyrite, was about three times that on galena and sphalerite, and specific adsorption on quartz was the lowest amongst the minerals studied. Specific adsorptions (in μmol/g) of HCNPHA on the minerals at pH 9 are: sphalerite: 30.5; galena: 26.9; chalcopyrite: 112.3; pyrite: 145.4; quartz: 2.9. Compared to pH 9, specific adsorption of HCNPHA on the minerals decreased at pH 10, indicating hydroxylation of mineral sites due to higher hydroxide ion concentration at pH 10. A spectral-colorimetric procedure was developed for the quantitative estimation of HCNPHA. Due to deprotonation of hydroxamic acids direct estimation using UV absorption was not possible. Hence, complexation of HCNPHA with Fe3+ was used to develop a purple coloured complex that absorbs in the visible region with λ max =500 nm. Change in concentration of HCNPHA was measured from absorbance of the HCNPHA- Fe3+ complex at 500 nm.
Keywords: Hydroxamic acids; Pure minerals; Adsorption; UV spectra; Mineral processing
Production of low sulfur diesel fuel via adsorption: an equilibrium and kinetic study on the adsorption of dibenzothiophene onto NaY zeolite by Jianzhun Jiang; Flora T. T. Ng (pp. 549-558).
The adsorption of dibenzothiophene (DBT) in hexadecane onto NaY zeolite has been studied by performing equilibrium and kinetic adsorption experiments. The influence of several variables such as contact time, initial concentration of DBT and temperature on the adsorption has been investigated. The results show that the isothermal equilibrium can be represented by the Langmuir equation. The maximum adsorption capacity at different temperatures and the corresponding Langmuir constant (K L ) have been deduced. The thermodynamic parameters (ΔG 0,ΔH 0,ΔS 0) for the adsorption of DBT have also been calculated from the temperature dependence of K L using the van’t Hoff equation. The value of ΔH 0,ΔS 0 are found to be −30.3 kJ mol−1 and −33.2 J mol−1 K−1 respectively. The adsorption is spontaneous and exothermic. The kinetics for the adsorption process can be described by either the Langmuir model or a pseudo-second-order model. It is found that the adsorption capacity and the initial rate of adsorption are dependent on contact time, temperature and the initial DBT concentration. The low apparent activation energy (12.4 kJ mol−1) indicates that adsorption has a low potential barrier suggesting a mass transfer controlled process. In addition, the competitive adsorption between DBT, naphthalene and quinoline on NaY was also investigated.
Keywords: Dibenzothiophene; Adsorption; NaY zeolite; Sulfur removal; Adsorptive model; Enthalpy of adsorption
Metal organic frameworks showing hydrocarbon adsorption properties commensurate with their pore structure by David Olson; Anjian Lan; Jonathan Seidel; Kunhao Li; Jing Li (pp. 559-565).
Commensurate adsorption occurs when the number of molecules adsorbed per unit cell relates to the symmetry of the framework and its topology. While rare in zeolite materials, commensurate adsorption has been observed in several MOF materials. In some MOF materials, several molecules having dimensions within a limited size range show this effect. This paper describes the commensurate adsorption properties of three MOF materials and also two MOFs showing unusual combined structure-composition adsorption features.
Keywords: Metal organic framework; MOF; Commensurate; Adsorption
Triamine-grafted pore-expanded mesoporous silica for CO2 capture: Effect of moisture and adsorbent regeneration strategies by Rodrigo Serna-Guerrero; Youssef Belmabkhout; Abdelhamid Sayari (pp. 567-575).
Adsorption of carbon dioxide (CO2) was investigated on triamine-grafted, pore-expanded MCM-41 mesoporous silica (TRI-PE-MCM-41). Measurements of adsorption capacity using mass spectrometry showed an enhanced CO2 adsorption capacity in humid streams compared to dry CO2. This was corroborated with breakthrough experiments, which also showed that TRI-PE-MCM-41 offered a practically infinite selectivity towards CO2 over nitrogen. Cyclic measurements of pure CO2 and CO2:N2 = 10:90 mixture using different regeneration modes showed that amine-grafted PE-MCM-41 is particularly suitable for CO2 removal using temperature swing adsorption (TSA) at adsorption temperatures higher than ambient, while temperature-vacuum swing adsorption (TVSA) may be attractive at ambient temperature.
Keywords: CO2 capture; Adsorption capacity; Adsorption selectivity; Adsorbent regeneration; TSA; TVSA
Synthesis of chiral mesoporous silica and its potential application to asymmetric separation by Toshiyuki Yokoi; Syusaku Sato; Yoichiro Ara; Daling Lu; Yoshihiro Kubota; Takashi Tatsumi (pp. 577-586).
Chiral mesoporous silica (CMS) has been successfully synthesized in the presence of basic amino acids; the use of basic amino acids in combination with the chiral anionic surfactant is advantageous for the formation of CMS in terms of uniformity in the twisted morphology. We first demonstrate that thus obtained chiral mesoporous silicas can be used for the enantioselective separation of racemic compounds; the helical rod-shaped CMS is found to be capable of asymmetric separation of racemic N-trifluoroacetylalanine ethyl ester (CF3CO-Ala-OEt). The left handedness-rich CMS shows asymmetric preferential adsorption of the L isomer and vice versa.
Keywords: AMS; Chiral mesoporous silica; Basic amino acid; Handedness; Asymmetric separation
Optimisation of carbon dioxide recovery from flue gas in a TPSA system by Vinay Mulgundmath; F. Handan Tezel (pp. 587-598).
Power stations and industrial processes burning fossil fuels account for the largest percentage of carbon dioxide emissions. Carbon capture and sequestration has received enormous global attention to reduce the carbon footprint and combat global warming. Adsorption has become an alternative technique to the conventional absorption process for capturing carbon dioxide due to its low operating and capital costs.In this study, Pressure Swing Adsorption (PSA) process has been compared with Thermal Pressure Swing Adsorption (TPSA) process for CO2 recovery from a flue gas composition of 10% CO2 (by vol) in N2 using Ceca 13X adsorbent. A factorial design set of experiments was performed to optimise the carbon dioxide recovery and study the effects and interaction of four control parameters namely, purge/feed flow ratio, purge time, purge gas temperature and adsorption column pressure.Results indicated that better regeneration conditions used in a TPSA cycle was essential over a PSA cycle for regaining maximum adsorption capacity of the used Ceca 13X adsorbent. It was found that Purge time had a significant effect on the CO2 recovery followed by Column pressure, purge/feed flow ratio and purge temperature. A Minitab® statistical software was used to analyse the data. It was found that the test of significance for lack of fit showed the fitted model to be an adequate representation of the experimental data. The results showed that to maximise the CO2 recovery, highest values of the control parameters have to be used.
Keywords: Carbon dioxide recovery from flue gas; Carbon capture; Carbon dioxide sequestration; Recycle of carbon dioxide; 13X zeolite; Pressure swing adsorption (PSA); Temperature pressure swing adsorption (TPSA)