ИСТИНА

The method of preparation metal-carbon nanocomposites based on IR-pyrolyzed polyacrylonitrile (IR-PAN) and platinum group metal nanoparticles was developed. The metal-carbon composites were prepared under the conditions of IR pyrolysis of a precursor based on polyacrylonitrile (PAN), detonation nanodiamonds (DND) and PdCl2 or PtCl4 and RuCl3. Pyrolysis was performed in an IR chamber of a setup for pulse photon annealing. The carbonization of PAN and metal reduction in the presence of hydrogen which is released during dehydrogenation of backbone polymer chain of PAN took place simultaneously. The TEM study showed that irrespective of the intensity of IR pyrolysis, metallic particles were distributed over sizes in a narrow interval, the mean sizes were 6–8 nm. According to the XRD data for nanocomposites prepared at 700–1000°C there were two intensity peaks corresponded to Pt and Pt13Ru27 intermetallic compound reflection angles. For Pd-carbon nanocomposites the increase of Pd lattice period was estimated due to the solution of hydrogen eliminating from PAN chain under destruction. IR spectroscopy study showed that metal ions formed complexes with the conjugation system being formed and bound to –CN terminal groups and the nearest conjugated bonds –C=N–C=N–. Thus, PAN helps to distribute metal particles finely and prevents metal nanoparticles aggregation. The additional carbon components (like DND or CNT) were added to increase specific area that is important in catalytic reaction. The samples IR-PAN-DND/Pt-Ru were tested as the catalysts in modeling reaction of cyclohexane dehydrogenation. The increasing of IR-PAN content from 0 to 10 mass.% caused significant increase of cyclohexane conversion (from 10% to 95%). The samples IR-PAN-DND /Pd showed the absolute selectivity for cyclohexanone. Thus, for the first time metal-carbon nanocomposites were developed under the conditions of IR-pyrolysis of precursors based on PAN and PdCl2 or PtCl4 and RuCl3 salts. The nanocomposites are promising for application as effective catalysts for dehydrogenation of cyclohexane and cyclohexanole.