Catalyst Performance Of Pt-Sn/MWCNTs (Modified) On The Dehydrogenation Of Propane

Preparation of excellent catalysts is the key to the manufacture of highvalue-added propylene during the dehydrogenation of propane technology.In the study，the Pt-Sn catalysts were supported on modified multiwalledcarbon nanotubes (MWCNTs) for dehydrogenation of propane. To date, theoxidation of CNTs with acid solution or strong oxidant is well kown, butsome disadvantages still exist. Therefore, three effective methods arecarried out to modify MWCNTs: calcination at high temperature with airatmosphere, activation of MWCNTs in nitric acid vapor and combination ofboth. The effects of three methods on the catalyst are discussed in details.The structures of MWCNTs after treatment of high-temperature air arecharacterized by SEM, TEM and XRD methods‘The result indicates thatthe framework of CNT almost keeps the raw MWCNTs, and a few defectsappear on the surface of MWCNTs. The hydrophilia of carboxy groupobtained on the surface of MWCNTs was characterized by TG and IRtechniques. Moreover, the influence of the calcination time on the catalystperformance is studied and gains the best calcinations conditions. Resultsmanifest that the propane conversion and selectivity increased firstly andthen decreased after the Pt-Sn/A-MWCNTs (450°C,80min) catalysts morethan once.And the catalytic performance is optimal through regenerative forthree times and exceeds alumina supported catalyst in the same condition..Similarly, SEM and TEM spectroscopy methods are used tocharacterize the MWCNTs treated by nitric acid vapor. The resultsdemonstrates that the length of MWCNTs becomes shorter significantly,more port openings and defect positions. The active component is dispersedwell and the diameter of the particles are l-3nm for Pt-Sn/MWCNTs (H120°C4.5-7.5h) from TEM. The hydrophilia of carboxyl group was characterizedby TG and IR techniques. Modified MWCNTs are more excellent supporter,compared with y-A1203. The influences of activation time and temperatureon the catalyst performance are also studied to obtain the best activationconditions.Finally, the effects of three modified methods on the catalyticperformance are also investigated. The level of reactivation of MWCNTs,the size of the catalyst particle, the distribution of the metal component, andthe interaction between Pt-Sn and carrier, give rise to different catalytic performance, according to the TEM，SEM,]R. Raman and TPR analysis. Itcomes to a conclusion that the activation of MWCNTs under nitric acidvapor is simplest and the most effective method to modify MWCNTs.