TY - JOUR A1 - Brzezinka, Klaus-Werner A1 - Trunschke, A. A1 - Hoang, D. L. A1 - Radnik, J. A1 - Brückner, A. A1 - Lieske, H. T1 - Transition metal oxide/carbon composite catalysts for n-alkane aromatization: Structure and catalytic properties N2 - Nanocrystalline particles of high temperature pretreated titania, zirconia or hafnium oxide, embedded in a carbon matrix, have been found to catalyze the aromatization of n-octane into ethylbenzene (EB) and o-xylene (OX) with high selectivity. The carbon matrix itself is catalytically not active, but seems to co-operate with the transition metal oxides in such a way that the various metal oxide/carbon composite materials exhibit equal selectivity patterns. In detail, the carbon component stabilizes a high dispersion of the oxides during the high temperature pretreatment procedure. This thermal treatment results in a destruction of surface acidity of the oxides, which would otherwise be responsible for undesirable consecutive and parallel reactions. Moreover, the carbon component is involved in the deep dehydrogenation of alkanes to multiple unsaturated alkenes. This is explained by the ability of surface carbon atoms to interact with hydrogen. The bulk and surface structure of the catalysts have been characterized by XRD, specific surface area measurements, XPS, UPS, Raman spectroscopy, in situ ESR and DRIFT spectroscopy. KW - Aromatization KW - Dehydrocyclization KW - n-Octane KW - Monofunctional catalysts KW - Zirconia KW - Titania KW - Oxide/carbon composites PY - 2001 DO - https://doi.org/10.1016/S0926-860X(00)00736-5 SN - 0926-860X SN - 1873-3875 VL - 208 IS - 1-2 SP - 381 EP - 392 PB - Elsevier CY - Amsterdam AN - OPUS4-1083 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hoang, D. L. A1 - Dittmar, A. A1 - Schneider, M. A1 - Trunschke, A. A1 - Lieske, H. A1 - Brzezinka, Klaus-Werner A1 - Witke, Klaus T1 - Evidence of lanthanum-chromium mixed oxides formed in CrOx/La2O3 model catalysts N2 - CrOx/La2O3 mixed oxides, prepared by impregnating La2O3 with appropriate aqueous solutions of (NH4)2CrO4 and calcining at 600 °C for 4 h, have been investigated by means of XRD, TPR, XPS, DRIFTS, and Raman spectroscopy (RS). The formation of the compounds La2CrO6, La(OH)CrO4 and LaCrO4 under these conditions was evidenced. Strong peaks at 864, 884, 913, and 921 cm-1, as well as weak peaks at 136, 180, 354, 370, and 388 cm-1 in the RS spectrum of CrOx/La2O3 have been assigned to La2CrO6. KW - Lanthanum-chromium mixed oxides KW - La2CrO6 KW - LaCrO4 KW - TPR KW - XPS KW - XRD KW - DRIFTS KW - Raman spectroscopy PY - 2003 DO - https://doi.org/10.1016/S0040-6031(02)00491-4 SN - 0040-6031 SN - 1872-762X VL - 400 SP - 153 EP - 163 PB - Elsevier CY - Amsterdam AN - OPUS4-2397 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -