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Impregnation of zeolite membranes for enhanced selectivity

Jonas Lindmark ; Jonas Hedlund ; Sang Kompiang Wirawan (Institutionen för kemi- och bioteknik, Kemisk reaktionsteknik) ; Derek Creaser (Institutionen för kemi- och bioteknik, Kemisk reaktionsteknik) ; Mingrun Li ; Daliang Zhang ; Xiaodong Zou
Journal of Membrane Science (0376-7388). Vol. 365 (2010), 1-2, p. 188-197.
[Artikel, refereegranskad vetenskaplig]

A new method to enhance the selectivity of zeolite membranes for alternative separation tasks has been developed. Calcined MFI membranes were impregnated with a solution of Ca(NO3)2 in methanol and calcined at 600 °C to thermally decompose the nitrate. SEM and EDS data indicated that calcium compounds were evenly distributed in the entire MFI film and in addition, a few crystals of a calcium compound were observed on top of the film in some locations. A HR-TEM investigation showed that calcium compounds were present in low concentration in the sample and that the interiors of the MFI crystals remained fully crystalline after impregnation and calcination. However, the HR-TEM investigation could neither confirm nor rule out the occurrence of calcium compounds in the pores in the interiors of the crystals. In accordance with the SEM and TEM observations, XRD data showed that calcium compounds on top of the film were relatively large CaCO3 crystals and that the zeolite film remained crystalline after impregnation. However, eventual calcium compounds in the pores of the zeolite could not be studied by XRD since these would probably generate a very weak signal of amorphous material. FTIR data indicated that impregnation increased the amount of both physisorbed and chemisorbed CO2, the latter resulting in carbonate species in the film. n-Hexane/helium adsorption branch permporometry showed that the high quality of the membranes remained after modification. The single component permeance ratio CO2/H2 increased from 0.6 to 1.5 after impregnation. Calculations indicated that the increased CO2/H2 single component permeance ratios were both an effect of increased adsorption of CO2 in the film and reduced pressure drop in the support. The dual component separation factor α CO2/H2 at room temperature increased drastically from 0.7 (H2 selective) to 3.4 (CO2 selective) after impregnation. This work shows for the first time that impregnation procedures can be used to tailor the diffusion properties of zeolite membranes in a similar way as impregnation procedures are used to tailor the catalytic performance of catalysts.

Nyckelord: zeolite membrane, impregnation, carbon dioxide, separation, selectivity



Denna post skapades 2010-11-15. Senast ändrad 2015-03-30.
CPL Pubid: 129116

 

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Institutioner (Chalmers)

Institutionen för kemi- och bioteknik, Kemisk reaktionsteknik (2005-2014)

Ämnesområden

Materialkemi
Molekylära transportprocesser i kemisk processteknik

Chalmers infrastruktur