Study of copper-chromium oxide catalyst
| Autor: | Gustav Plesch, František Hanic, K. Putyera |
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| Rok vydání: | 1989 |
| Předmět: |
Chromate conversion coating
Thermal decomposition Inorganic chemistry Oxide Infrared spectroscopy chemistry.chemical_element Condensed Matter Physics Copper Catalysis Ammonia chemistry.chemical_compound chemistry Crystal data Chromium oxide Physical chemistry Composition (visual arts) Physical and Theoretical Chemistry Ammonium chromate Instrumentation |
| Zdroj: | Thermochimica Acta. 145:19-32 |
| ISSN: | 0040-6031 |
| DOI: | 10.1016/0040-6031(89)85123-8 |
| Popis: | Basic copper(II)-ammine ammonium chromate (BCAAC) of the composition [(Cu 2+ ) 1+ x (NH 4 + ) y (OH − ) 2 2x + y (NH 3 ) z (CrO 4 2− )] was prepared by the reaction of basic copper(II)-ammonium chromate (BCAC) with ammonia. Compounds with coefficients x , y , z varying in the approximate intervals 0 x y z p NH 3 . According to the results of IR, electronic and EPR spectra, NH 3 substitutes for oxygen and hydroxyl groups bound to Cu(II) and [Cu(NH 3 ) 4 ] 2+ complexcations are formed in BCAAC. This reaction is reversible at room temperature and it can be written schematically as Download full-size image At 130° C and 180° C ammonia desorption takes place in the process of the thermal decomposition. At ca. 205 ° C an explosive Cr(VI) to Cr(III) reduction leads to copper-chromium oxide catalyst with highly disordered structure. After its heating to 500° C a system, which contains crystalline CuO and a metastable CuCr 2 O 4 with a unit cell of orthorhombic symmetry ( a = 0.593 nm, b = 0.603 nm, c = 0.779 mn) was obtained. The activity of the catalyst in the hydrogenation-alkylation reaction is lower than the activity of the one prepared from BCAC at 270 °C. |
| Databáze: | OpenAIRE |
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