Inorganic Microporous Membranes for Gas Separation in Fossil Fuel ...

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4 Results and discussion DTA µV/mg 0.1 0.0 -0.1 -0.2 -0.3 -0.4 Exo 8YSZ 8YSZ +F127 8YSZ +F127 +Acetyl acetone +caproic acid 100 200 300 400 500 600 T [ºC] A 81 Weigth [%] 100 90 80 70 60 50 40 30 8YSZ 8YSZ +F127 +Acetyl acetone +Caproic acid 100 200 300 400 500 600 Figure 48 DTA (A) and TG (B) curves 8YSZ dried sols of blank, +F127 and AcCa+F127 T [ºC] 8YSZ +F127 In summary, first 8YSZ powder can be prepared microporously with the addition of acetyl acetone as the precursor modifier and caproic acid as the condensation catalyst to the sol. However, the specific surface area of only ~50 m 2 /g of this microporous material might form membrane layers with too low porosity. This could lead to low permeabilities, see page 96. Second, the 8YSZ sol is, in combination with block copolymer Pluronic #F127 mesostructuring the nanocrystals and offers the most interesting mesoporous membrane material due to its high specific surface area. The block copolymer F127 seems to prevent densification during the firing steps. The F127 mesostructering of 8YSZ can be interesting for several applications such as catalytic reactions or membranes that may be more suited for separating bulkier molecules. Third, the formation of porous 8YSZ is less effective for extraction compared to regular calcination. Extraction of the dried 8YSZ sols results in amorphous material with relative large pore sizes. Forth, the organics in the sols are gradually released during the calcination. As a consequence, these ZrO2 coatings should be calcined carefully in the first temperature period (up to 450ºC) in order to maintain the film morphology unchanged. 4.3.2.2 Amine approach-TiO2 A combination of type I and IV N2-sorption isotherms is obtained when the dried TiO2 DEA sols are calcined at 400, 500 and 600ºC (Figure 49). Similar trends are found in literature. 83 The BET specific surface area (SBET) of the TiO2 samples decreases with increasing calcination temperature (Table 23). This trend is coupled with an increase in the pore size (BJH algorithm 130 ) from 3.8, 6.1 to 8 nm and an increase of crystal size B
4 Results and discussion from 11.3, 15.1 to 22.1 nm determined with the Scherer equation for respectively 400, 500 and 600 ºC. The relative micropore volume (Vmicro/Vtotal) decreases from 25 at 400ºC to 8% at 600ºC. TiO2 microstructure properties trends clearly indicate a densification of the material with increasing calcination temperature. Table 23 Microstructure properties of dried TiO2 sols Calcination Temp. in [ºC] Equivalent 1 M HNO3 Crystal size nm SBET m 2 /g Vtotal cm 3 /g Vmicro cm 3 /g BJH nm 140 7 amorphous - - - - 400 7 11.3 216 0.24 0.06 3.8 400 10 - 214 0.26 0.06 3.8 500 7 15.1 90 0.18 0.03 6.1 500 10 - 75 0.16 0.02 6.0 600 7 22.1 36 0.09 0.01 8.0 The effect on the TiO2 microstructural properties was studied by changing the quantity of the hydrolysis solution. The hydrolysis solution (1 M HNO3) was increased from 7 equivalent to 10 equivalent to the titanium precursor. The microstructure properties are listed in Table 23. The specific surface area and the relative microporous absorbed volume of the TiO2 powders calcined at 400 and 500ºC seem be independent on the increase of equivalent 7 to 10 of the hydrolysis solution. This indicates that the sol modification is mild as expected from similar average particle size in the sol. An average particle size of 4.4 nm was found with 7 equivalent 1 M HNO3and 4.1 nm with 10 equivalent 1 M HNO3. The dried TiO2 sols listed in Table 23 transform from XRD-amorphous to anatase TiO2 in the temperature range of 140-400ºC. The TiO2-TG plot (Figure 50) shows a weight loss with three decomposition steps in the interval of 30-600ºC. The weight loss below ~225ºC is assigned to the water desorption and organic removal. The decomposition step between 225 and 475ºC can be related to the gradual decomposition of the amine ligands on the outer and inner surface of the material which is believed to be bonded more strong than e.g. n-propanol. The third step in weight loss is small. The DTA pattern is complementary with the TG observations. The exothermic peak in the DTA plot at ~225ºC suggests the removal of loosely bound organic residues. The second broad exothermic peak (320-360ºC) might be related to the gradual decomposition of the amine groups in combination with the gradual anatase TiO2 crystallisation. 82
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Mitglied der Helmholtz-Gemeinschaft
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Forschungszentrum Jülich GmbH Inst
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List of Abbreviations Ac Acetyl Ace
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Summary CO2 capture and storage mig
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Zusammenfassung Die Abtrennung und
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Content Content CONTENT............
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1 Introduction and aims 1 Introduct
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2 Theoretical background 2 Theoreti
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2 Theoretical background 2.1.2 Micr
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2 Theoretical background Poly-cryst
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2 Theoretical background membranes
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2 Theoretical background Dry or wet
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2 Theoretical background the materi
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2 Theoretical background Figure 11
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2 Theoretical background due to its
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2 Theoretical background 2.3.3.2 Mi
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Page 48 and 49: 3 Experimental 3 Experimental The m
Page 50 and 51: 3 Experimental vacuum sample holder
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Page 56 and 57: 3 Experimental 3.4 Characterisation
Page 58 and 59: 3 Experimental Element analysis The
Page 60 and 61: 3 Experimental Additionally, the hy
Page 62 and 63: 4 Results and discussion Abundance
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Page 102 and 103: 4 Results and discussion In pure Ti
Page 104 and 105: 4 Results and discussion In summary
Page 106 and 107: 4 Results and discussion Intensity
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Page 110 and 111: 4 Results and discussion ~50nm TiO2
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Page 126 and 127: 6 References 22. Shao, Z., Dong, H.
Page 128 and 129: 6 References 65. Van den Berg, A. W
Page 130 and 131: 6 References 108. Wen, T. L., Heber
Page 132 and 133: Curriculum Vitae - George van der D
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Page 137: Band | Volume 8 ISBN 978-3-89336-52
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Inorganic Microporous Membranes for Gas Separation in Fossil Fuel ...

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