SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "LAR1:ltu ;srt2:(2010-2019);pers:(Hedlund Jonas)"

Sökning: LAR1:ltu > (2010-2019) > Hedlund Jonas

  • Resultat 1-10 av 111
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Aguilar-Mamani, Wilson, et al. (författare)
  • Internal structure of a gel leading to NBA-ZSM-5 single crystals
  • 2018
  • Ingår i: Journal of porous materials. - : Springer. - 1380-2224 .- 1573-4854. ; 25:6, s. 1551-1559
  • Tidskriftsartikel (refereegranskat)abstract
    • Porous gel structures are formed during the synthesis of the zeolite ZSM-5 due to the reaction between a source of aluminosilicate, sodium hydroxide, water and a structure directing agent, such as e.g. tetrapropylammonium (TPA) or n-butylamine (NBA). In the present work, the formation of the gel in a heterogeneous system leading to the crystallization of NBA-ZSM-5 zeolite from leached metakaolin was studied extensively. The solid and liquid phases obtained after separation were analyzed by inductively coupled plasma sector field mass spectrometry, dynamic light scattering, extreme high resolution-scanning electron microscopy, energy dispersive spectroscopy, high resolution-transmission electron microscopy, X-ray diffraction and nitrogen gas adsorption. The main gel phase formed after hydrothermal treatment exhibited a sponge-like structure resembling those forming in (Na, TPA)-ZSM-5-based systems. For the first time, the walls of the main gel were shown to be inhomogenous and to possess a biphasic internal structure consisting of a mesoporous skeleton of aluminosilicate nanoparticles embedded in a silicate-rich soluble matrix of soft matter. The data presented in this paper is of primary importance to understand the mechanism by which the gel is consumed and contributes to the growth process of the zeolite crystals.
  •  
2.
  • Aguilar-Mamani, Wilson, et al. (författare)
  • Solution-mediated growth of NBA-ZSM-5 crystals retarded by gel entrapment
  • 2018
  • Ingår i: Journal of Crystal Growth. - : Elsevier. - 0022-0248 .- 1873-5002. ; 487, s. 57-64
  • Tidskriftsartikel (refereegranskat)abstract
    • The synthesis of flat tablet-shaped ZSM-5 crystals from a gel using metakaolin as aluminosilicate source and n-butyl amine as structure directing agent was investigated. The evolution inside the solid phase was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetry and mass spectrometry. A kinetic study indicated that the nucleation of the majority crystals occurred concurrently with the formation of the gel upon heating the starting liquid suspension. Microstructural evidences undeniably showed that the gel precipitated on ZSM-5 crystals and mineral impurities originating from kaolin. As a result, crystal growth was retarded by gel entrapment, as indicated by the configuration and morphology of the embedded crystals. The results presented herein are harmonized with a solution-mediated nucleation and growth mechanism. Our observations differ from the autocatalytic model that suggests that the nuclei rest inside the gel until released when the gel is consumed. Our results show instead that it is crystals that formed in an early stage before entrapment inside the gel that rest inside the gel until exposed at the gel surface. These results illustrate the limitation of the classical method used in the field to determine nucleation profiles when the crystals become trapped inside the gel.
  •  
3.
  • Aguilar, Wilson, et al. (författare)
  • Comparison between leached metakaolin and leached diatomaceous earth as raw materials for the synthesis of ZSM-5
  • 2014
  • Ingår i: SpringerPlus. - : Springer. - 2193-1801. ; 3:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Inexpensive raw materials have been used to prepare ZSM-5 zeolites with SiO2/Al2O3 molar ratios in the range 20 - 40. Kaolin or Bolivian diatomaceous earth was used as aluminosilicate raw materials and sodium hydroxide and n-butylamine were used as mineralizing agents and template. Dealumination of the raw materials by acid leaching made it possible to reach appropriate SiO2/Al2O3 ratios and to reduce the amount of iron and other impurities. After mixing the components and aging, hydrothermal treatment was carried out and the products were recovered The results clearly show for the first time that well-crystallized ZSM-5 can be directly prepared from leached metakaolin or leached diatomaceous earth using sodium hydroxide and n-butylamine as mineralizing agents and template under appropriate synthesis conditions. A longer induction time prior to crystallization was observed for reaction mixtures prepared from leached diatomaceous earth, probably due to slower digestion of the fossilized diatom skeletons as compared with that for microporous leached metakaolin. The use of leached diatomaceous earth allowed higher yield of ZSM-5 crystals within comparable synthesis times. However, low amounts of Mordenite formed, which was related to the high calcium content of diatomaceous earth. Another considerable advantage of diatomaceous earth over kaolin is that diatomaceous earth does not require heat treatment at high temperature for metakaolinization.
  •  
4.
  •  
5.
  • Akhtar, Farid, et al. (författare)
  • Hierarchically porous binder-free silicalite-1 discs : a novel support for all-zeolite membranes
  • 2011
  • Ingår i: Journal of Materials Chemistry. - 0959-9428 .- 1364-5501. ; 21:24, s. 8822-8828
  • Tidskriftsartikel (refereegranskat)abstract
    • Thermal expansion mismatch between the zeolite film and the support is an important cause for the formation of defects and cracks during the fabrication and use of zeolite membranes. We have studied how silicalite-1 discs with a permeability comparable to commercially available alumina supports can be produced by pulsed current processing (PCP) as a novel substrate for all-zeolite membranes. Hierarchically porous and mechanically strong membrane supports where the surface area and crystallography of the silicalite-1 particles were maintained could be obtained by carefully controlling the thermal treatment during PCP consolidation. In situ X-ray diffraction and dilatometry showed that the coefficient of thermal expansion (CTE) of the silicalite-1 substrate was negative in the temperature range 200-800 degrees C while the commonly used alumina substrate displayed a positive CTE. The critical temperature variation, Delta T, and thicknesses for crack-free supported zeolite films with a negative CTE were estimated using a fracture energy model. Zeolite films with a thickness of 1 mu m can only sustain a relatively modest Delta T of 100 degrees when supported onto alumina substrates while the all-zeolite membranes can support temperature variations above 500 degrees
  •  
6.
  •  
7.
  • Akhtar, Farid, et al. (författare)
  • Preparation of graded silicalite-1 substrates for all-zeolite membranes with excellent CO2/H-2 separation performance
  • 2015
  • Ingår i: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 493, s. 206-211
  • Tidskriftsartikel (refereegranskat)abstract
    • Graded silicalite-1 substrates with a high gas permeability and low surface roughness have been produced by pulsed current processing of a thin coating of a submicron silicalite-1 powder onto a powder body of coarser silicalite-1 crystals. Thin zeolite films have been hydrothermally grown onto the graded silicalite-1 support and the all-zeolite membranes display an excellent CO2/H-2 separation factor of 12 at 0 degrees C and a CO2 permeance of 21.3 x 10(-7) mol m(-2) s(-1) Pa-1 for an equimolar CO2/H-2 feed at 505 kPa and 101 kPa helium sweep gas. Thermal cracking estimates based on calculated surface energies and measured thermal expansion coefficients suggest that all-zeolite membranes with a minimal thermal expansion mismatch between the graded substrate and the zeolite film should remain crack-free during thermal cycling and the critical calcination step.
  •  
8.
  •  
9.
  •  
10.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-10 av 111
Typ av publikation
tidskriftsartikel (88)
konferensbidrag (22)
doktorsavhandling (1)
Typ av innehåll
refereegranskat (101)
övrigt vetenskapligt/konstnärligt (10)
Författare/redaktör
Grahn, Mattias (42)
Mouzon, Johanne (27)
Korelskiy, Danil (25)
Holmgren, Allan (21)
Zhou, Ming (14)
visa fler...
Sjöberg, Erik (10)
Zhou, Han (10)
Bhuiyan, Iftekhar Ud ... (8)
Potapova, Elisaveta (8)
Sandström, Linda (7)
Yu, Liang, 1986- (7)
Akhtar, Farid (6)
Carabante, Ivan (6)
Antzutkin, Oleg (6)
Yu, Liang (5)
Bergström, Lennart (4)
Garcia, Gustavo (4)
Faisal, Abrar (4)
Ohlin, Lindsay (4)
Farzaneh, Amirfarrok ... (4)
Öberg, Sven (3)
Cabrera, Saul (3)
Ojuva, Arto (3)
Wirawan, Kompiang (3)
Forsmo, Seija (3)
Öhrman, Olov (3)
Forsmo, S.P.E. (3)
Nobandegani, Mojtaba ... (3)
Forsberg, Fredrik (2)
Kota, Hanumantha Rao (2)
Bacsik, Zoltan (2)
Creaser, Derek, 1966 (2)
Johansson, Björn (2)
Aguilar-Mamani, Wils ... (2)
Aguilar, Wilson (2)
Rayson, Mark (2)
Dobryden, Illia (2)
Kumpiene, Jurate (2)
Gebart, Rikard (2)
Ikumapayi, Fatai (2)
Berggren, Andreas (2)
Larsson, Anna-Carin (2)
Fouladvand, Shahpar (2)
Yang, Xiaofang (2)
Nabavi, Mohammad Sad ... (2)
Öhrman, Olov G. W. (2)
Forsmo, Seija P.E. (2)
Fredriksson, Andreas (2)
Westerstrand, Magnus (2)
visa färre...
Lärosäte
Luleå tekniska universitet (111)
RISE (4)
Stockholms universitet (3)
Chalmers tekniska högskola (2)
Kungliga Tekniska Högskolan (1)
Sveriges Lantbruksuniversitet (1)
Språk
Engelska (111)
Forskningsämne (UKÄ/SCB)
Teknik (111)
Naturvetenskap (16)
Medicin och hälsovetenskap (1)

År

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy