SYNTHESIS, CRYSTAL-STRUCTURE REDETERMINATION AND VIBRATIONAL-SPECTRA OF BETA-VOSO4

Dark bluish-green prismatic crystals of the compound beta-VOSO4, suitable for X-ray structure determination, have been obtained from solutions of V2O5 in molten K2S2O7/Na2S2O7 under sulfuric acid synthesis gas or flue gas atmospheres. Slow cooling from 480 to 420-440 degrees C gave a large crop of crystals of beta-VOSO4, and the crystal structure has been accurately redetermined. The compound crystallizes in the orthorhombic crystal system, space group Pnma (No. 62) with a = 7.376(3), b = 6.269, c = 7.082(3) Angstrom and Z = 4. It contains distorted VO6 octahedra linked together in a zigzag course parallel to the a-axis by sharing opposite corners in infinite chains along which adjacent VO6 octahedra are also connected by a bridging sulfate group. The remaining two oxygen atoms of the sulfate groups link by corner sharing to upper and lower lying VO6 octahedra along the b-axis, thus forming a three-dimensional network. Within the VO6 octahedron a short V-O bond [1.598(2) Angstrom], four in-plane (equatorial) bonds with intermediate lengths (1.994-1.998 Angstrom) and a bond opposite to the short one with a length of 2.271(2) Angstrom are found. The infrared and Raman spectra of the compound have been recorded and interpreted. The importance of beta-VOSO4 as deactivation product of working SO2 oxidation catalyst model melts and industrial catalysts is discussed.