Supercritical CO2 intercalation of layered silicates

Serhatkulu, Gulay
Dilek Hacıhabiboğlu, Çerağ
Gulari, Esin
In this study, we use supercritical CO2 as the processing medium for intercalating the structure of natural clay, Cloisite Na+, and depositing CO2-philic sugar acetate, P-D-galactose pentaacetate, between the layers of the clay. Based on our measurements of the phase behavior of the P-D-galactose pentaacetate-CO2 system, we select two processing conditions: a dense gas solution (DGS) at 40 degrees C and 11.7 MPa with 2.4 wt.% sugar acetate in CO2 and a gas-expanded liquid (GEL) at 40 degrees C and 7.9 MPa with 6.1 wt.% sugar acetate in CO2. The morphology of the as-received natural clay and clay samples processed under the DGS and the GEL conditions is determined by wide-angle X-ray diffraction (XRD), transmission electron microscopy (TEM) and low-energy electron diffraction (LEED) methods. The XRD results indicate intercalation of the clay layers. While the ordered structure remains, the gallery spacing between Cloisite Ne layers is doubled, from 0.3 1 to 0.52 and 0.59 nm for DGS- and GEL-processing conditions, respectively. The LEED patterns of the processed clays show bright spots characteristic of the highly crystalline sugar acetate superimposed on the halo pattern of the clay, confirming the deposition of the sugar acetate in the intercalated structure of the clay after scCO(2) processing.


Enhanced solubility of siloxy-modified polyhedral oligomeric silsesquioxanes in supercritical carbon dioxide
Demirtas, Cansu; Dilek Hacıhabiboğlu, Çerağ (Elsevier BV, 2019-01-01)
Alkyl siloxy functionalization increases the solubility of polyhedral oligomeric silsesquioxanes (POSS) in supercritical carbon dioxide over an order of magnitude compared to its counterpart with fluoroalkyl groups. The studied component, octatrimethylsiloxy POSS also exhibits higher solubility than other previously studied POSS types with various alkyl and methacryl groups. The octatrimethylsiloxy POSS-CO2 solid-vapor equilibrium curves have been constructed at temperatures between 308 and 328 K by measuri...
Phase Behavior of Carbon Dioxide and Polyhedral Oligomeric Silsesquioxanes with Two Different Functional Groups
Dumanlilar, Beril; Dilek Hacıhabiboğlu, Çerağ (Elsevier BV, 2020-09-01)
Phase behavior of carbon dioxide and polyhedral oligomeric silsesquioxanes (POSS) modified with two different functional groups is studied in the temperature range of 308-323 K, up to 22 MPa. Different than the common types, one of the eight functional groups attached to the Si atoms of these POSS is a CO2-philic functional group, methacryl, while the rest are branched alkyl chains, either isooctyl (MIOPOSS) or isobutyl (MIBPOSS). Methacrylisobutyl POSS-CO2 binary system exhibits pressure-induced melting te...
Optimization of supercritical CO2 extraction of Thymbra spicata oil
Sonsuzer, S; Şahin, Serpil; Yılmaz, Levent (Elsevier BV, 2004-07-01)
The supercritical fluid extraction (SFE) of aroma compounds from Thymbra spicata was studied. Response surface methodology (RSM) was used to optimize the parameters of the supercritical fluid extraction. Independent variables were temperature (40, 50 and 60 degreesC), pressure (80, 100 and 120 bar) and time (30, 60 and 90 min). Dependent variables were yield, monoterpene, sesquiterpene and oxygenated monoterpene contents.
Phase behavior of 1,3,5-tri-tert-butylbenzene-carbon dioxide binary system
Dilek Hacıhabiboğlu, Çerağ; Gulari, Esin (Elsevier BV, 2008-01-01)
1,3,5-tri-tert-butylbenzene (TTBB) is solid at ambient conditions, and has substantial solubility in liquid and supercritical carbon dioxide. We present the phase behavior of TTBB-CO2 binary system at temperatures between 298 and 328 K and at pressures up to 20 MPa. Phase diagrams showing the liquid-vapor, solid-liquid and solid-vapor equilibrium envelopes are constructed by pressure-volume-temperature measurements in a variable-volume sapphire cell. TTBB is highly soluble in CO2 over a wide range of compos...
Cyclacenes having mono boron or nitrogen atom in the backbone - a theoretical study
Türker, Burhan Lemi; Gumus, S (Elsevier BV, 2004-04-09)
Semi-empirical molecular orbital treatment at the level of AMI unrestricted Hartree-Fock type calculations was performed on the Huckel type boron and nitrogen substituted cyclacenes. Substitution is done either in a peri position or a fusion points. Boron substitution is found to be destabilizing. whereas nitrogen substitution has stabilizing effect on parent cyclacenes.
Citation Formats
G. Serhatkulu, Ç. Dilek Hacıhabiboğlu, and E. Gulari, “Supercritical CO2 intercalation of layered silicates,” JOURNAL OF SUPERCRITICAL FLUIDS, pp. 264–270, 2006, Accessed: 00, 2020. [Online]. Available: