A series of metal-modified HZSM-5 catalysts were prepared by impregnation and were used for ethylbenzene dealkylation of the mixed C8 aromatics(ethylbenzene,m-xylene and o-xylene).The effects of different supported me...A series of metal-modified HZSM-5 catalysts were prepared by impregnation and were used for ethylbenzene dealkylation of the mixed C8 aromatics(ethylbenzene,m-xylene and o-xylene).The effects of different supported metals(Pt,Pd,Ni,Mo)on catalytic performance,including reaction conditions,were investigated.The physicochemical properties of catalysts were characterized by means of XRD,BET,TEM and NH_(3)-TPD.Experimental results showed that metallic modification obviously increased the ethylbenzene conversion and reduced the coke deposition,greatly improving the catalyst stability.The distinction of ethylbenzene conversion depended on the interaction between hydrogenation reactivity and acidic cracking of bifunctional metal-modified zeolites.Compared with Pt and Ni,Pd and Mo were easier to disperse into HZSM-5 micropores during loading metals.The acidic density of different metal-modified HZSM-5 declined in the following order:HZSM-5>Pt/HZSM-5>Pd/HZSM-5>Ni/HZSM-5>Mo/HZSM-5.The activity of ethylene hydrogenation decreased with Pt/HZSM-5>Pd/HZSM-5>Ni/HZSM-5>Mo/HZSM-5.In comparison,Pd/HZSM-5 showed the best catalytic performance with both high activity and high selectivity,with less cracking loss of m-xylene and o-xylene.Moreover,the following reaction conditions were found to be preferable for ethylbenzene dealkylation over Pd/HZSM-5:340℃,1.5 MPa H2,WHSV 4 h^(−1),H_(2)/C84 mol/mol.展开更多
Geoporphyrins, isolated from source rock, were analyzed on electron ionization mass spectrometry （EIMS） and Tandem mass spectrometry （MS/MS）. The spectrum of ElMS shows that the geoporphyrins are mainly composed o...Geoporphyrins, isolated from source rock, were analyzed on electron ionization mass spectrometry （EIMS） and Tandem mass spectrometry （MS/MS）. The spectrum of ElMS shows that the geoporphyrins are mainly composed of two types: DPEP and eito. Most of the porphyrin carbon numbers are greater than C<sub>32</sub>. The daughter spectra of the molecular ions (C<sub>34-36</sub>DPEPs) display the loss of methyl and ethyl groups, which indicate there are ethyl and propyl groups in the mother ions. The average condensed structural formulae, derived from the data of the spectra on MS/MS, have clearly shown the composition of the substituents on the porphyrin pyrrole ring, and the regular changes of the substituents reveal the characteristics of the dealkylation of the porphyrins in the geosphere.展开更多
基金supported by the National Natural Science Foundation of China(Nos.20873091,51174277)China National Petroleum Corporation Innovation Research Funds(No.2012D-5006-0505).
文摘A series of metal-modified HZSM-5 catalysts were prepared by impregnation and were used for ethylbenzene dealkylation of the mixed C8 aromatics(ethylbenzene,m-xylene and o-xylene).The effects of different supported metals(Pt,Pd,Ni,Mo)on catalytic performance,including reaction conditions,were investigated.The physicochemical properties of catalysts were characterized by means of XRD,BET,TEM and NH_(3)-TPD.Experimental results showed that metallic modification obviously increased the ethylbenzene conversion and reduced the coke deposition,greatly improving the catalyst stability.The distinction of ethylbenzene conversion depended on the interaction between hydrogenation reactivity and acidic cracking of bifunctional metal-modified zeolites.Compared with Pt and Ni,Pd and Mo were easier to disperse into HZSM-5 micropores during loading metals.The acidic density of different metal-modified HZSM-5 declined in the following order:HZSM-5>Pt/HZSM-5>Pd/HZSM-5>Ni/HZSM-5>Mo/HZSM-5.The activity of ethylene hydrogenation decreased with Pt/HZSM-5>Pd/HZSM-5>Ni/HZSM-5>Mo/HZSM-5.In comparison,Pd/HZSM-5 showed the best catalytic performance with both high activity and high selectivity,with less cracking loss of m-xylene and o-xylene.Moreover,the following reaction conditions were found to be preferable for ethylbenzene dealkylation over Pd/HZSM-5:340℃,1.5 MPa H2,WHSV 4 h^(−1),H_(2)/C84 mol/mol.
文摘Geoporphyrins, isolated from source rock, were analyzed on electron ionization mass spectrometry （EIMS） and Tandem mass spectrometry （MS/MS）. The spectrum of ElMS shows that the geoporphyrins are mainly composed of two types: DPEP and eito. Most of the porphyrin carbon numbers are greater than C<sub>32</sub>. The daughter spectra of the molecular ions (C<sub>34-36</sub>DPEPs) display the loss of methyl and ethyl groups, which indicate there are ethyl and propyl groups in the mother ions. The average condensed structural formulae, derived from the data of the spectra on MS/MS, have clearly shown the composition of the substituents on the porphyrin pyrrole ring, and the regular changes of the substituents reveal the characteristics of the dealkylation of the porphyrins in the geosphere.
