Features of technology of preparation of catalytic systems by thermal decomposition for synthesis of carbon nanotubes

Resumo

The critical task for the manufacturing process management of metal-metal oxide catalysts (as exemplified by Co–Mo/Al₂O₃–MgO) for the synthesis of carbon nanotubes (CNT) was solved with application of a new technology. The following main characteristic groups of the catalytic systems determining their quality were identified and discussed: physical and mechanical (bulk density and tapped density; repose, tapped, and collapse angles), the degree of feedstock conversion (shares of the mass loss during heating and calcination), the catalyst activity (the CNT specific yield by the catalyst and their specific surface), and indirect indicators (pH of the aqueous suspension and the true density). Methods and modes of the study selected parameters of the catalyst were experimentally proved and analytical equipment was recommended. A new control factor of the thermal decomposition stage of the catalyst was identified. It is the specific consumption of dehydrated air. Its impact on the catalyst performance was shown. Necessary and sufficient specific consumption for the catalyst Co–Mo/Al₂O₃–MgO making it possible to stabilize the quality indicators was determined, which is equal to 55 kg_air/kg_catalyst. Metrological approaches to the certification of the produced catalysts, Co–Mo/Al2O3–MgO, under the conditions of an actual carbon nanotechnology enterprise (NanoTechCenter Ltd., Tambov, Russia) were considered, which allowed increasing the catalyst quality. The relative divergence of the mass loss during calcination was reduced from 110.0% to 24%; the specific yield, from 64.9% to 8.5%; and the specific surface area of nanotubes, from 45.6% to 15.4%.