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Development of b-oriented MFI membranes on graded alpha-alumina supports
2007 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The zeolite crystal structure MFI has straight pores in the b-direction. It is believed that membranes with b-oriented MFI crystals have high flux and a low amount of cracks, and may be very well suited for separation of hydrocarbon isomers with a diameter of about 6 Å, such as xylenes. The aim of this work was to prepare b-oriented MFI membranes on graded supports, by further improving a technique developed at the department. The membranes were prepared using a seeding technique. b-Oriented seed adsorption was facilitated by first creating a smooth substrate, by spin coating a layer of 100 nm zirconia particles on graded alumina substrates. Discrete 550 and 330 nm flat MFI seeds were adsorbed b-oriented, assisted by ultra-sound treatment. The flat 180 nm seeds made in this work were aggregated, and hence could not adsorb b-oriented. Films were prepared using two different synthesis solutions. One film was grown with a synthesis solution for 500 nm flat seeds (here denoted solution 1), a solution that was assumed to favour b-oriented growth of the films. Films were also grown with the 'standard' synthesis solution used at the department (here denoted solution 2). The film grown in solution 1 was very thick (about 50 micrometer). Due to competitive growth, this film was c-oriented. Solution 2 favoured 'twins' (90° rotational intergrowths), which gave a film with a-, b- and oblique orientation from a b-oriented seed layer. Two membranes made with solution 2 were tested in gas permeation measurements. The results were promising, but showed that further improvement is necessary.

Place, publisher, year, edition, pages
Keyword [en]
Physics Chemistry Maths
Keyword [sv]
Fysik, Kemi, Matematik
URN: urn:nbn:se:ltu:diva-42703ISRN: LTU-EX--07/149--SELocal ID: 0ad9ea0b-491f-4865-9e33-9fd1b509a362OAI: diva2:1015928
Subject / course
Student thesis, at least 30 credits
Educational program
Chemical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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