Experimental Study On Preparation Of Fe-Mo/Al₂O₃ Catalysts Based On Microreactor

Catalysts are particularly essential for the preparation of carbon nanotubes?CNTs?.Due to the uneven mixing and imprecise control in the traditional stirred reactor,the prepared catalysts are poorly dispersed and the particle size distribution is uneven,which affect the performance and production of CNTs.Based on the advantages of precise control and rapid mixing of micro-fluid,microreactor breaks through the shackles of traditional batch process.Thus,microreactor becomes the key to realize refinement and efficient preparation of catalytic materials.In this work,Fe-Mo/Al2O3 catalysts were prepared in the microreactor,and the micro-structure of the catalysts and CNTs were characterized by various detection methods.It was found that the microreactor enhanced the distribution uniformity of precipitated components in the co-precipitation process,enhanced the internal forces between the active components and the carrier,and continuously affected the subsequent preparation process.Compared with the catalysts prepared by the traditional method,the catalysts prepared by the microreactor had small particle size and good catalytic activity,up to 64.04%.The catalytic graphitization of the CNTs was improved,and the diameter of CNTs was concentrated in 11-15 nm.The aging process,calcination process and reduction process of the catalyst were studied based on microreactor.In the aging experiment,the catalysts and the CNTs were characterized and analyzed for different temperature and time.The results showed that the aging temperature had a more obvious effect on the micro-structure and properties of Fe-Mo/Al₂O₃ catalyst than the aging time.The growth of crystal nuclei can be improved by increasing the aging temperature and extending the aging time.When the aging temperature was 40?and the aging time was 4h,the catalytic activity was high,and the CNTs had better quality.In the study of calcination experiment,three groups of calcination temperatures were set and compared from catalyst to CNTs.Although the catalysts carrier prepared by microreactor can play a better role,there still was different degrees of sintering agglomeration.When the roasting temperature increased from 350?to 600?,the crystallinity and particle size of the nanoparticles increased,and the proportion of the diameter of the carbon nanotubes increased.In addition,the activity of the catalyst was greatly affected by the calcination temperature.when the calcination temperature was450?,the activity of the catalyst Fe-Mo/Al₂O₃ was greater.The process of catalyst reduction is relatively easy to ignore its importance.After several experiments,the results showed that the catalysts reduced at 350?reduced the sintering degree,but the catalytic efficiency was greatly reduced and the defects of the carbon nanotubes were increased.When catalysts reduced at 600?,the conversion rate of carbon source propylene increased,and the defect degree of carbon nanotubes decreased obviously.Besides,under the premise of growth temperature of carbon source propylene at 660?,moderate reduction temperature could increase the catalytic performance of the catalyst.Among them,the catalytic activity of the catalysts calcined at 450?and reduced at 600?was relatively high,reaching74.76%.