4045-53-8Relevant articles and documents
Methylbenzene hydrocarbon pool in methanol-to-olefins conversion over zeolite H-ZSM-5
Wang, Chao,Xu, Jun,Qi, Guodong,Gong, Yanjun,Wang, Weiyu,Gao, Pan,Wang, Qiang,Feng, Ningdong,Liu, Xiaolong,Deng, Feng
, p. 127 - 137 (2015/11/09)
The formation and reactivity of a methylbenzenes (MBs) hydrocarbon pool in the induction period of the methanol-to-olefins (MTO) reaction over zeolite H-ZSM-5 was investigated and the mechanistic link of MBs to ethene and propene was revealed. Time evolution analysis of the formed MBs and 12C/13C methanol-switching experiments indicate that in the induction period bulkier compounds such as tetraMB and pentaMB have higher reactivity than their lighter counterparts such as p/m-diMB and triMB. By correlating the distribution of MBs trapped on H-ZSM-5 with ethene and propene, we found that tetraMB and pentaMB favor the formation of propene, while p/m-diMB and triMB mainly contribute to the formation of ethene. On the basis of this relationship, the olefin (ethene and propene) selectivity can be controlled by regulating the distribution of trapped MBs by varying the silicon-to-aluminum ratio of ZSM-5, reaction temperature, and space velocity. The reactivity of MBs and the correlation of MBs with olefins were also verified under steady-state conditions. By observation of key cyclopentenyl and pentamethylbenzenium cation intermediates using in situ solid-state NMR spectroscopy, a paring mechanism was proposed to link MBs with ethene and propene. P/M-diMB and triMB produce ethylcyclopentenyl cations followed by splitting off of ethene, while tetraMB and pentaMB generate propyl-attached intermediates, which eventually produce propene. This work provides new insight into the MBs hydrocarbon pool in MTO chemistry.
An Electron Spin Resonance Study of the Methylcyclopentadienyl Radicals, MenH5-nC5 (n=1-5)
Davies, Alwyn G.,Lusztyk, Ewa,Lusztyk, Janusz
, p. 729 - 736 (2007/10/02)
The radicals MenC5H5-n have been generated by photolysis of the corresponding hydrocarbons (n=3-5) or mercury derivatives (n=0-5) and their e.s.r. spectra have been recorded.The spectra are interpreted in terms of thermal population of the ψA and ψS molecular orbitals, for which the predicted hyperfine coupling constants are calculated by the McLachlan equation, taking λ 0.75 and Q(C5H5) -30 and Q(Me5C5) 31.85 G.The energy separations between the ψA and ψS MOs can be rationalised on the assumption that a methyl substituent on a carbon atom of the cyclopentadienyl carrying a unit ?-electron has a destablising interaction, within a factor of two, of 10 kJ mol-1.
