Abstract
Methyl gallate (MG) and ethyl ferulate (EF) with a benzene ring were separately used as aromatic organic chelating ligands (aOCLs) to prepare two versions of TiO2-ZrO2-aOCL composite sols via hydrolysis and polycondensation reactions with titanium(IV) isopropoxide (Ti(OC3H7)4) and zirconium(IV) butoxide (Zr(OC4H9)4). Thermogravimetric and FT-IR analysis of dry gels revealed that aromatic rings were present in the residual organic matter when the gel was fired under nitrogen at 300 °C. In X-ray diffraction (XRD) measurements, the TiO2-ZrO2 composite material prepared using these two aOCLs showed an amorphous structure with no crystalline peaks for TiO2 and ZrO2. In N2 adsorption/desorption measurements at 77 K, the TiO2-ZrO2 samples using the aOCLs as a template appeared porous with a larger specific surface area than TiO2-ZrO2 without aOCL. TiO2-ZrO2-aOCL composite membranes were prepared by coating and firing TiO2-ZrO2-aOCL sol onto a SiO2 intermediate layer using an α-alumina porous tube as a substrate. Compared with the TiO2-ZrO2 membrane, the TiO2-ZrO2-aOCL membranes had higher gas permselectivity. The TiO2-ZrO2-EF membrane showed a He permeance of 2.69 × 10−6 mol m−2 s−1 Pa−1 with permeance ratios of He/N2 = 10.6 and He/CF4 = 163, while the TiO2-ZrO2-MG membrane revealed a bit less He permeance at 8.56 × 10−7 mol m−2 s−1 Pa−1 with greater permeance ratios of He/N2 = 61.7 and He/CF4 = 209 at 200 °C. A microporous TiO2-ZrO2 amorphous structure was obtained by introducing aOCL. The differences in the side chains of each aOCL could possibly account for the differences in the microporous structures of the resultant TiO2-ZrO2-aOCL membranes.
Highlights
Separation of the molecular mixtures in chemical plants is an important unit operation.This operation, consumes about 40% of the energy consumption of the chemical process, which makes this an important issue [1]
Inorganic membranes are superior to general organic polymeric membranes in terms of thermal stability, chemical resistance, and mechanical strength, and they are expected to have utility under environments and in conditions where organic polymer membranes are of no use. [11]
Gas separation layers were formed using TiO2-ZrO2 composite sols, which were prepared by employing methyl gallate (MG) and ethyl ferulate (EF) as aromatic organic chelating ligands (aOCLs)
Summary
Separation of the molecular mixtures in chemical plants is an important unit operation. A gas separation membrane prepared with TiO2 and ZrO2 materials would be considered compatible with various chemical processes It is very difficult, to control pore sizes small compatible with various chemical processes. Spijksma et al prepared have applied TiO2 -ZrO2 composite materials to gas separation membranes. The objective of this study was to develop a TiO2 -ZrO2 composite gas separation membrane using using a new aromatic organic chelating ligand (aOLC). Gas separation layers were formed using TiO2-ZrO2 composite sols, which were prepared by employing MG and EF as aOCLs. We attempted to control the effective pore size for gas permeation by using the above two aOCLs with different side chains attached to the benzene ring. Gas separation layers were formed using TiO2 -ZrO2 composite sols, which were prepared by employing.
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