Project
Hydrogen desorption and sorption properties of boronhydride sodalites: model systems for hydrogen containing reservoir minerals

Prof. Dr. Josef-Christian Buhl
Institute of Mineralogy, University of Hannover, Germany

The investigation of new materials for hydrogen storage is of potential interest for future energy management. Beside metal hydrides being well established up to now, even zeolites have been discussed as potential materials for hydrogen storrage [1,2,3]. Beside the treatment of pre-formed zeolites under hydrogen atmosphere at high pressures Barrer already suggested an impregnation of zeolites with boron hydride salts [4]. In this way, however, only the big α-cages of zeolites can be filled and the hydride ions rapidly decompose by reaction with water from the air. Another way could be a direct synthesis of hydride anion containing sodalites. The long term stable inclusion of boron hydride anions into the cavities of sodalite was recently described by us first for the aluminosilicate system [5]. This new sodalite has a high degree of cage fillings with tetrahydroborate anions and shows a durable protection of the enclathrated hydride by the surrounding aluminosilicate network.

On the basis of the experience on synthesis of alumino-silicate sodalites with tetrahydro-borate anions we plan to investigate the desorption and resorption properties of NaBH₄^- sodalite and related T-atom substituated sodalites. Because the sodalite matrix prevents hydrolysis of the enclathrated BH₄^- anions special reactions like a controlled release of hydrogen could be possible independent on age of the sample. The investigations on the reaction behaviour of the enclathrated BH₄^- anions will be performed in dependence of the gas atmosphere and pressure (air, argon, hydrogen), the temperature and heating rate as well as the degree of hydride anion fillings of the sodalite host structure. The influence on the openings of the sodalite six-ring “windows” will be studied by using T-atom substituted samples (GeAl- and GaSi- species).

Besides typical characterization of the as synthesized samples by XRD and IR spectroscopy the reaction behaviour will be analysed by high temperature XRD in a special gas pressure cell as well as by simultaneous thermoanalysis (TG/DSC) and high temperature hard mode infrared spectroscopy.

From the project we expect new informations on principles of the secure incorporation of hydroborate into sodalite cavities being even of interest for zeolites A, X and Y, the new materials maybe have also the potential to be versatile catalysts for regioselective reduction reactions in organic chemistry [6].

Literature:
1. J. Weitkamp, M. Fritz M, St. Ernst, J. Hydrogen Energ. 20 (12) (1995) 967.
2. M. G. Nijkamp, J. E. M. J. Raaymakers,A. J. van Dillen, K. P. de Jong KP, Applied Physics A-Materials Science & Processing 72 (2001) 619
3. M. Momirlan, T. N. Veziroglu, Renewable & Sustainable Energy Rev. 6 (2002) 141
4. R.M. Barrer, Hydrothermal Chemistry of Zeolites, Academic press, London, 1982.
5. J.-C. Buhl, T. M. Gesing, C. H. Rüscher, Ber. Dtsch. Miner. Ges, Beih. z. Eur. J. Mineral. 16 (2004) No. 1, 24.
6. R. Sreekumar, R. Padmakumar, P. Rugmini, Tetrahedron Letters 39 (1998) 5151