CRYSTAL-STRUCTURE OF A HYDROGEN-SULFIDE SORPTION COMPLEX OF ZEOLITE LTA

The crystal structure of a hydrogen sulfide sorption complex of Na-12- A, Na-12-A .12H2S (a = 12.289(8) Angstrom), has been determined by sin gle-crystal X-ray diffraction techniques in the cubic space group <Pm( 3)over bar m> at 21(1)degrees C. The structure was refined to the fina l error indices R = 0.047 and R(w) = 0.033 with 153 reflections for wh ich I > 3 sigma(I). Twelve H2S molecules are sorbed per unit cell. Eig ht Na+ ions are found at two different 6-oxygen-ring sites, where each coordinates to three framework oxygens at ca. 2.32(2) Angstrom. Six o f the eight Na+ ions extend 0.47(1) Angstrom into the large cavity fro m the (111) planes of the 6 rings, where each coordinates at 2.98(2) A ngstrom to one H2S sulfur in the large cavity. The remaining two 6 rin g Na+ ions do not associate with H2S and are located near the centers of their 6 rings. Three Na+ ions are found in 8-oxygen-ring planes, wh ere each coordinates to one framework oxygen at 2.39(2) Angstrom and t o two H2S sulfurs in the large cavities at 2.74(3) Angstrom. The twelf th Na+ ion coordinates to the four framework oxygens of a 4-ring at 2. 71(3) Angstrom, and to one or two of the above H2S molecules at 2.78(6 ) Angstrom. The sodalite cavities are empty. (C) Elsevier Science Inc. 1996