| 1. |
- Akhtar, Farid, et al.
(författare)
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Colloidal processing and CO2 capture performance of sacrificially templated zeolite monoliths
- 2012
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 97, s. 289-296
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Sacrificial templating of suspension cast and subsequently thermally treated zeolite monoliths with glassy carbon spheres and fibers yielded zeolite 13X and silicalite-1 monoliths with macroporosities up to 50 vol%. Homogeneous distribution of the macroporosity in hierarchically porous monoliths was obtained by tailoring the surface chemistry of the carbon particles by polyelectrolyte-assisted adsorption of zeolite particles. The effect of amount of kaolin binder and temperature for the thermal treatment on the monoliths strength, surface area and CO2 uptake was studied by diametral compression tests, electron microscopy, X-ray diffraction and gas adsorption. Cyclic adsorption and regeneration measurements showed that zeolite 13X monoliths display a high CO2 uptake while the silicalite-1 monoliths could be regenerated with a relatively low energy penalty.
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| 2. |
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| 3. |
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| 4. |
- Akhtar, Farid, et al.
(författare)
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Structuring adsorbents and catalysts by processing of porous powders
- 2014
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 34:7, s. 1643-1666
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Tidskriftsartikel (refereegranskat)abstract
- Microporous materials such as zeolites, metal organic frameworks, activated carbons and aluminum phosphates are suitable for catalysis and separation applications. These high surface area materials are invariably produced in particulate forms and need to be transformed into hierarchically porous structures for high performance adsorbents or catalysts. Structuring of porous powders enables an optimized structure with high mass transfer, low pressure drop, good heat management, and high mechanical and chemical stability. The requirements and important properties of hierarchically porous structures are reviewed with a focus on applications in gas separation and catalysis. Versatile powder processing routes to process porous powders into hierarchically porous structures like extrusion, coatings of scaffolds and honeycombs, colloidal processing and direct casting, and sacrificial approaches are presented and discussed. The use and limitations of the use of inorganic binders for increasing the mechanical strength is reviewed, and the most important binder systems, e.g. clays and silica, are described in detail. Recent advances to produce binder-free and complex shaped hierarchically porous monoliths are described and their performance is compared with traditional binder-containing structured adsorbents. Needs related to better thermal management and improved kinetics and volume efficiency are discussed and an outlook on future research is also given.
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| 5. |
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| 6. |
- Andersson, Linnéa, et al.
(författare)
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Colloidal processing and CO2-capture performance of hierarchically porous Al2O3-zeolite 13X composites
- 2012
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Ingår i: Journal of Ceramic Science and Technology. - 2190-9385. ; 3:1, s. 9-16
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Tidskriftsartikel (refereegranskat)abstract
- Hierarchically porous composites for CO2-capture have been produced by coating the inner walls of foam-like macroporous alumina monoliths, produced by templated synthesis, with microporous zeolite 13X particles. Homogeneous and dense coatings of the particulate adsorbent were obtained when the impregnation process was performed at a pH above 9. At this pH-level the colloidally stable suspensions of the negatively charged zeolite 13X particles could fill all the voids of the highly connected pore space of the alumina supports and attach to the monolith walls, which had been pre-coated with poly(ethylene imine). A CO2-uptake as high as 5 mmol CO2/g zeolite 13X was achieved for alumina-zeolite 13X composites through minimisation of the added inorganic binder, kaolin, to only 3.0 wt% with respect to zeolite content, and through optimisation of the thermal treatment.
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| 7. |
- Andersson, Linnéa, et al.
(författare)
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Evaluating pore space in macroporous ceramics with water-based porosimetry
- 2013
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Ingår i: Journal of The American Ceramic Society. - : Wiley. - 0002-7820 .- 1551-2916. ; 96:6, s. 1916-1922
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Tidskriftsartikel (refereegranskat)abstract
- We show that water-based porosimetry (WBP), a facile, simple, and nondestructive porosimetry technique, accurately evaluates both the pore size distribution and throat size distribution of sacrificially templated macroporous alumina. The pore size distribution and throat size distribution derived from the WBP evaluation in uptake (imbibition) and release (drainage) mode, respectively, were corroborated by mercury porosimetry and X-ray micro-computed tomography (μ-CT). In contrast with mercury porosimetry, the WBP also provided information on the presence of “dead-end pores” in the macroporous alumina.
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| 8. |
- Andersson, Linnéa, et al.
(författare)
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Permeability, pore connectivity and critical pore throat control of expandable polymeric sphere templated macroporous alumina
- 2011
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Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454 .- 1873-2453. ; 59:3, s. 1239-1248
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Tidskriftsartikel (refereegranskat)abstract
- We have regulated the permeability in macroporous alumina materials by manipulating the connectivity of the pore phase and the sizes of the smallest constrictions between connected pores. Templating with particle-coated expandable polymeric spheres (EPS) significantly increased the fraction of isolated pore clusters, and reduced both the sizes and the number of connections with neighboring pores, as determined by three-dimensional evaluation with X-ray micro-computed tomography. The stable particle coating, applied onto the EPS surfaces using polyelectrolyte multilayers, reduced the volume expansion and the coalescence of the EPS at elevated temperatures, which reduced the simulated permeability by as much as two orders of magnitude compared to templating with uncoated EPS in materials of similar porosities. We show that the Katz-Thompson model accurately predicts the permeability for the macroporous alumina materials with porosities of 46-76%. This suggests that the permeability to fluid flow in these materials is governed by the smallest constrictions between connected pores: the critical pore throat diameter.
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| 9. |
- Andersson, Linnéa, 1978-
(författare)
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Shaping Macroporous Ceramics : templated synthesis, X-ray tomography and permeability
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Macroporous ceramic materials have found widespread technological application ranging from particulate filters in diesel engines, tissue engineering scaffolds, and as support materials in carbon capture processes. This thesis demonstrates how the pore space of macroporous alumina can be manipulated, analysed in three-dimensions (3D) using visualisation techniques, and functionalised with a CO2-adsorbing material. A novel method was developed to produce macroporous alumina materials: by combining sacrificial templating with thermally expandable polymeric microspheres and gel-casting of an alumina suspension. This method offers a versatile production of macroporous ceramics in which the level of porosity and the pore size distribution can easily be altered by varying the amount and type of spheres. The permeability to fluid flow could be regulated by controlling the connectivity of the pore space and the size of the smallest constrictions between the pores. Sacrificial templating with particle-coated expandable spheres significantly increased the fraction of isolated pore clusters and reduced both the sizes and the numbers of connections between neighbouring pores, compared to templating with un-coated spheres. The macroporous alumina materials were characterised with X-ray micro-computed tomography (μ-CT). The 3D data-sets obtained by X-ray μ-CT were used to calculate the spatial variation in porosity, the throat and pore size distributions and to calculate the permeability to fluid flow. The throat and pore size distributions were also able to be accurately quantified in only one extrusion and intrusion cycle with water-based porosimetry; a relatively novel and simple characterisation technique. The pore walls of the macroporous alumina materials were also coated with zeolite films by a colloidal processing technique. The CO2-uptake of the coated alumina materials and of hierarchically porous monoliths of zeolites was evaluated and compared.
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| 10. |
- Andersson, Linnéa, et al.
(författare)
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Three-dimensional structure analysis by X-ray micro-computed tomography of macroporous alumina templated with expandable microspheres
- 2010
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Ingår i: Journal of the European Ceramic Society. - Amsterdam, Netherlands : Elsevier. - 0955-2219 .- 1873-619X. ; 30:12, s. 2547-2554
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Tidskriftsartikel (refereegranskat)abstract
- The three-dimensional (3D) structures of macroporous alumina, produced by a novel method that combines gel casting with expandable polymericmicrospheres as a sacrificial templating material, have been characterised by X-ray micro-computed tomography (µ-CT). The grey-scale intensitytomogram data produced by the X-ray µ-CT was segmented into porous and solid phases and the individual pores were identified. We comparedtwo-dimensional slices of the analysed data with the corresponding scanning electron microscopy images and showed that the structural featuresof the pores were well reproduced in the X-ray µ-CT images. 3D visualisations of the pore structure and the pore network were also shown. Theopen porosity obtained from X-ray µ-CT corresponded well with the porosity derived from mercury porosimetry for pores larger than the voxeldimension (3 µm). The quantitative analysis also yielded information on the spatial variations in porosity and the number of connected neighboursof pores. The 3D data was used to relate the calculated permeability to the open porosity.
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