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  • 1.
    Akhtar, Farid
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Andersson, Linnéa
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Keshavarzi, Neda
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Colloidal processing and CO2 capture performance of sacrificially templated zeolite monoliths2012In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 97, 289-296 p.Article in journal (Other academic)
    Abstract [en]

    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.

  • 2.
    Akhtar, Farid
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Luleå University of Technology, Sweden.
    Keshavarzi, Neda
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Shakarova, Dilshod
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Cheung, Ocean
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Aluminophosphate monoliths with high CO2-over-N2 selectivity and CO2 capture capacity2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 99, 55877-55883 p.Article in journal (Refereed)
    Abstract [en]

    Monoliths of microporous aluminophosphates (AlPO4-17 and AlPO4-53) were structured by binder-freepulsed current processing. Such monoliths could be important for carbon capture from flue gas. TheAlPO4-17 and AlPO4-53 monoliths exhibited a tensile strength of 1.0 MPa and a CO2 adsorption capacityof 2.5 mmol g1 and 1.6 mmol g1, respectively at 101 kPa and 0 C. Analyses of single component CO2and N2 adsorption data indicated that the AlPO4-53 monoliths had an extraordinarily high CO2-over-N2selectivity from a binary gas mixture of 15 mol% CO2 and 85 mol% N2. The estimated CO2 capturecapacity of AlPO4-17 and AlPO4-53 monoliths in a typical pressure swing adsorption (PSA) process at 20C was higher than that of the commonly used zeolite 13X granules. Under cyclic sorption conditions,AlPO4-17 and AlPO4-53 monoliths were regenerated by lowering the pressure of CO2. Regeneration wasdone without application of heat, which would regenerate them to their full capacity for CO2 adsorption.

  • 3.
    Hao, Wenming
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Keshavarzi, Neda
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Branger, Adrien
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Strong discs of activated carbons from hydrothermally carbonized beer waste2014In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 78, 521-531 p.Article in journal (Refereed)
    Abstract [en]

    Strong and dense activated carbon discs (ACDs) were synthesized and studied. The discs were produced in a multistep manner from a precursor based on hydrothermally treated beer waste (HTC-BW). The precursor was processed by pulsed current processing (PCP) into ACDs. These discs were activated by physical activation in CO2 at an elevated temperature. The ACDs had surface areas of ∼500 m2/g and contained significant amounts of micro-, meso-, and macropores. The effect on the temperature during the PCP and the presence of tar in the precursor were studied with respect to the properties of the discs. The ACDs had strengths up to 7.2 MPa with densities up to 1.4 g/cm3. The density is the highest reported for discs of activated carbon.

  • 4.
    Keshavarzi, Neda
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Structuring porous adsorbents and composites for gas separation and odor removal2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Porous zeolite, carbon and aluminophosphate powders have been colloidally assembled and post-processed in the form of monoliths, flexible free standing films and coatings for gas separation and odor removal. Zeolite 13X monoliths with macroporosites up to 50 vol% and a high CO2 uptake were prepared by colloidal processing and sacrificial templating. The durability of silicalite-I supports produced in a binder-free form by pulsed current processing (PCP) were compared with silicalite-I supports produced using clay-binders and conventional thermal treatment. Long-term acid and alkali treatment of the silicalite-I substrates resulted in removal of the clay binder and broadened the size-distribution of the interparticle macropores. Furthermore, strong discs of hydrothermally treated beer waste (HTC-BW) were produced by PCP and the discs were activated by physical activation in CO2 at high temperatures. The activated carbon discs showed high strength up to 7.2 MPa while containing large volume of porosities at all length scales. PCP was further used to structure aluminomphosphate powders (AlPO4-17 and AlPO4-53) into strong functional monoliths. The aluminophosphate monoliths had strengths of 1 MPa, high CO2 uptake and were easy to regenerate. Zeolite Y, silicalite and ZSM5 were selected as potential zeolite adsorbents for removal of sulfur containing compound, e.g. ethyl mercaptan (EM) and propyl mercaptan (PM). A novel processing procedure was used to fabricate free-standing films and coatings of cellulose nanofibrils (CNF) with a high content of nanoporous zeolite; 89 w/w% and 96 w/w%, respectively. Thin flexible free-standing films and coatings of zeolite-CNF on paperboards with thickness around 100 µm and 40 µm, respectively, were produced. Headspace solid phase microextraction (SPME) coupled to gas chromatography- mass spectroscopy (GC/MS) analysis showed that the zeolite-CNF films can efficiently remove considerable amount of odors below concentration levels that can be sensed by the human olfactory system.

  • 5.
    Keshavarzi, Neda
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Akhtar, Farid
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Chemical durability of hierarchically porous silicalite-I membrane substrates in aqueous media2013In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 28, no 17, 2253-2259 p.Article in journal (Refereed)
    Abstract [en]

    Zeolite-based supports for inorganic membranes intended for gas separation have the potential to increase the resistance to thermal shock-induced cracking compared with ceramic or metallic substrates. We have studied the effect of exposure at 90 degrees C of hierarchically porous silicalite-I substrates to aqueous solutions at pH 2.0, 10.6, and 13.0 for periods up to 168 h. Silicalite-I supports were produced in binder-free form by pulsed current processing and using clay-binders by conventional thermal treatment. Long-term (168 h) acid and alkali treatment of the silicalite-I substrates results in a slight removal of silicon (in acid) and aluminum (in alkali) and does not affect the specific surface area and the crystalline microporous structural features but broadens the size distribution of the macropores. The mechanical strength remains unchanged after exposure to both alkaline and acidic solutions and the binder-free substrates display more than 20 times higher strength than the binder-containing materials.

  • 6.
    Keshavarzi, Neda
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mashayekhy Rad, Farshid
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Mace, Amber
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ansari, Farhan
    Akhtar, Farid
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Berglund, Lars
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nanocellulose-Zeolite Composite Films for Odor EliminationManuscript (preprint) (Other academic)
    Abstract [en]

    Free standing and strong odor-removing composite films of cellulose nanofibrils (CNF) with a high content of nanoporous zeolite adsorbents have been produced by colloidal processing. Thermogravimetric desorption analysis (TGA) and infrared spectroscopy combined with computational simulations showed that three commercially available zeolites- silicalite, ZSM5 and zeolite Y, have a high affinity and uptake of important odors like ethanethiol and propanethiol, also in the presence of water. Highly flexible and strong free standing zeolite-CNF films with a thickness up to 115 μm and an adsorbent loading above 80 w/w% were obtained by gelation and vacuum filtration. Zeolite-CNF films displayed high mechanical strength of up to 10 MPa. Headspace solid phase microextraction (SPME) coupled to gas chromatography- mass spectroscopy (GC-MS) analysis showed that the CNF-zeolite films can eliminate volatile thiol-based odors to concentrations below the detection ability of the human olfactory system. The odor-removing performance of the zeolite-cellulose nanofibril films could enable improved transport and storage of fruits and vegetables rich in odors, e.g. onion and the tasty but foul-smelling South-East Asian Durian fruit.

  • 7.
    Keshavarzi, Neda
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Rad, Farshid Mashayekhy
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Mace, Amber
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ansari, Farhan
    Akhtar, Farid
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Berglund, Lars
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nanocellulose-Zeolite Composite Films for Odor Elimination2015In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 26, 14254-14262 p.Article in journal (Refereed)
    Abstract [en]

    Free standing and strong odor-removing composite films of cellulose nanofibrils (CNF) with a high content of nanoporous zeolite adsorbents have been colloidally processed. Thermogravimetric desorption analysis (TGA) and infrared spectroscopy combined with computational simulations showed that commercially available silicalite-1 and ZSM-5 have a high affinity and uptake of volatile odors like ethanethiol and propanethiol, also in the presence of water. The simulations showed that propanethiol has a higher affinity, up to 16%, to the two zeolites compared with ethanethiol. Highly flexible and strong free-standing zeolite CNF films with an adsorbent loading of 89 w/w% have been produced by Ca-induced gelation and vacuum filtration. The CNF-network controls the strength of the composite films and 100 mu m thick zeolite CNF films with a CNF content of less than 10 vol % displayed a tensile strength approaching 10 MPa. Headspace solid phase microextraction (SPME) coupled to gas chromatography mass spectroscopy (GC/MS) analysis showed that the CNF zeolite films can eliminate the volatile thiol-based odors to concentrations below the detection ability of the human olfactory system. Odor removing zeolite-cellulose nanofibril films could enable improved transport and storage of fruits and vegetables rich in odors, for example, onion and the tasty but foul-smelling South-East Asian Durian fruit.

1 - 7 of 7
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  • apa
  • ieee
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  • en-US
  • fi-FI
  • nn-NO
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  • Other locale
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