3853-27-8Relevant academic research and scientific papers
Tuning the photochemical properties of the fulvalene-tetracarbonyl-diruthenium system
Lennartson, Anders,Lundin, Angelica,B?rjesson, Karl,Gray, Victor,Moth-Poulsen, Kasper
supporting information, p. 8740 - 8744 (2016/06/09)
In a Molecular Solar-Thermal Energy Storage (MOST) system, solar energy is converted to chemical energy using a compound that undergoes reversible endothermic photoisomerization. The high-energy photoisomer can later be converted back to the parent compound and the excess energy is released as heat. One of the most studied MOST systems is based on fulvalene-tetracarbonyl-diruthenium, and this paper demonstrates, for the first time, the possibility to tune the photochemical properties of this system by positive steric hindrance working on the fulvalene unit.
Experimental Evidence on the Formation of Ethene through Carbocations in Methanol Conversion over H-ZSM-5 Zeolite
Wang, Chao,Yi, Xianfeng,Xu, Jun,Qi, Guodong,Gao, Pan,Wang, Weiyu,Chu, Yueying,Wang, Qiang,Feng, Ningdong,Liu, Xiaolong,Zheng, Anmin,Deng, Feng
supporting information, p. 12061 - 12068 (2015/08/18)
The methanol to olefins conversion over zeolite catalysts is a commercialized process to produce light olefins like ethene and propene but its mechanism is not well understood. We herein investigated the formation of ethene in the methanol to olefins reaction over the H-ZSM-5 zeolite. Three types of ethylcyclopentenyl carbocations, that is, the 1-methyl-3-ethylcyclopentenyl, the 1,4-dimethyl-3-ethylcyclopentenyl, and the 1,5-dimethyl-3-ethylcyclopentenyl cation were unambiguously identified under working conditions by both solid-state and liquid-state NMR spectroscopy as well as GC-MS analysis. These carbocations were found to be well correlated to ethene and lower methylbenzenes (xylene and trimethylbenzene). An aromatics-based paring route provides rationale for the transformation of lower methylbenzenes to ethene through ethylcyclopentenyl cations as the key hydrocarbon-pool intermediates. Carbocation key: Three types of ethylcyclopentyl carbocations were identified under working conditions. The mechanistic link between ethene and these cations was established. An aromatic-based paring route provides rationale for the transformation of lower methylbenzenes to ethene through these cations.
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.
In Situ 13C Solid-State NMR and Ex Situ GC-MS Analysis of the Products of tert-Butyl Alcohol Dehydration on H-ZSM-5 Zeolite Catalyst
Stepanov, Alexander G.,Sidelnikov, Vladimir N.,Zamaraev, Kirill I.
, p. 157 - 167 (2007/10/03)
The hydrocarbon products that are formed upon dehydration at 296-673 K of tert-butyl alcohol (tBuOH), adsorbed on H-ZSM-5 zeolite in concentrations equal to that of active Al-OH-Si sites in the catalyst, have been analyzed by 13C solid-state MAS NMR and GC-MS.To facilitate 13C NMR analysis, the alcohol selectively labeled with 13C isotope in the COH group was used.It was found that tBuOH transforms to the adsorbed C8 butene dimers plus a trace amount of alkanes at 296 K.Butene dimers exist inside H-ZSM-5- pores in the form of interconverting adsorbed octene, octyl silyl ether, and octyl carbenium ion; octyl silyl ether is the main adsorption state.Fluxionality of the carbenium ion form provides a pathway for isomerization of the highly branched hydrocarbon skeleton of the initial alcohol to the predominantly linear one in the adsorbed butene dimer.The driving force for the isomerization into the linear structure is the shape selectivity induced by the small size of the zeolite channels.At 373 K the adsorbed butene dimers further crack into species that contain an average of about 6.5 carbon atoms, in addition to further alkanes.At 448 K the adsorbed C3-C7+, paraffins become the predominant hydrocarbon products observed with both in situ 13C NMR and ex situ GC-MS.Simultaneously, a mixture of adsorbed polyenes is formed.According to 13C CP/MAS NMR, polyenes exist in the zeolite pores in the form of rather stable cyclopentenyl cations.At 573-673 K adsorbed cyclopentenyl cations further transform into a mixture of condensed and simple aromatics and then into xylenes and toluene.Simultaneously, paraffins crack further to give mainly C3-C4 paraffinic species at 573 K and propane at 673K. - Keywords: alcohols; cracking; dehyrations; isomerizations; NMR spectroscopy
