The liquid phase ring-opening of octamethylcy-clotetrasiloxane(D_4) was investigated over Pt-H_2SO_4/Zrmontmorillonite catalyst. Montmorillonite(Mt), Zr-Mt, H_2SO_4/Mt, H_2SO_4/Zr-Mt and Pt-H_2SO_4/Zr-Mt were also det...The liquid phase ring-opening of octamethylcy-clotetrasiloxane(D_4) was investigated over Pt-H_2SO_4/Zrmontmorillonite catalyst. Montmorillonite(Mt), Zr-Mt, H_2SO_4/Mt, H_2SO_4/Zr-Mt and Pt-H_2SO_4/Zr-Mt were also detected for evaluation. The catalysts were characterized by X-ray fluorescence, X-ray diffraction, nitrogen adsorption–desorption, NH_3-TPD and pyridine-FTIR measurements. In comparison to activate clay which is used in the industry of catalyst, Zr-Mt catalyst displayed stronger acidity and more excellent catalytic activity in the polymerization of D_4, polymethylhydrosiloxane(D_4 H) and hexamethyldisiloxane(MM) to low-hydro silicone oil. Relative to Zr-Mt, the acidity of H_2SO_4/Zr-Mt was noticeably improved and the catalyst exhibited a higher capability of ring-opening of D_4 conversion and yield of low-hydro silicone oil. To enhance the stability of H_2SO_4/Zr-Mt catalyst, a small amount of metals(Pt) was doped. The nitrogen adsorption–desorption results indicated that pore textural parameters of the Pt-H_2SO_4/Zr-Mt had not changed with larger specific surface area. Compared with H_2SO_4/Zr-Mt, the total acidity of Pt-H_2SO_4-Zr/Mt catalyst retained, but the content of the Br?nsted acid increased and the content of the Lewis acid decreased. The Pt-H_2SO_4-Zr/Mt catalyst displayed higher catalyst reproducibility. After 40 h reaction of polymerization, the yield of low-hydro silicone oil decreased from 93% to 42% over H_2SO_4/Zr-Mt catalyst, while the yield of low-hydro silicone oil reduced from 93% to 78%over Pt-H_2SO_4/Zr-Mt catalyst. A sharp decrease in catalytic activity after 35 h of Pt-H_2SO_4/Zr-Mt catalyst was detected. Furthermore, Pt-H_2SO_4/Zr-Mt was completely regenerated under appropriate condition and appeared good repeatability in the D_4, D_4 Hand MM to low-hydro silicone oil.展开更多
Pt supported on mesoporous silica SBA-15 was investigated as a catalyst for low temperature selective catalytic reduction（SCR） of NO by C 3 H 6 in the presence of excess oxygen.The prepared catalysts were characteri...Pt supported on mesoporous silica SBA-15 was investigated as a catalyst for low temperature selective catalytic reduction（SCR） of NO by C 3 H 6 in the presence of excess oxygen.The prepared catalysts were characterized by means of XRD,BET surface area,TEM,NO-TPD,NO/C 3 H 6-TPO,NH 3-TPD,XPS and 27 Al MAS NMR.The effects of Pt loading amount,O 2 /C 3 H 6 concentration,and incorporation of Al into SBA-15 have been studied.It was found that the removal efficiency increased significantly after Pt loading,but an optimal loading amount was observed.In particular,under an atmosphere of 150 ppm NO,150 ppm C 3 H 6,and 18 vol.% O 2,0.5% Pt/SBA-15 showed remarkably high catalytic performance giving 80.1% NOx reduction and 87.04% C 3 H 6 conversion simultaneously at 140°C.The enhanced SCR activity of Pt/SBA-15 is associated with its outstanding oxidation activities of NO to NO 2 and C 3 H 6 to CO 2 in low temperature range.The research results also suggested that higher concentration of O 2 and higher concentration of C 3 H 6 favored NO removal.The incorporation of Al into SBA-15 improved catalytic performance,which could be ascribed to the enhancement of catalyst surface acidity caused by tetrahedrally coordinated AlO 4.Moreover,the catalysts could be easily reused and possessed good stability.展开更多
Employing hot tungsten filament to thermal dissociate molecular hydrogen,we generated gas phase atomic hydrogen under ultra-high vacuum(UHV)conditions and investigated its interaction with Pt(111) surface.Thermal deso...Employing hot tungsten filament to thermal dissociate molecular hydrogen,we generated gas phase atomic hydrogen under ultra-high vacuum(UHV)conditions and investigated its interaction with Pt(111) surface.Thermal desorption spectroscopy(TDS)results demonstrate that adsorption of molecular hy- drogen on Pt(111)forms surface Had species whereas adsorption of atomic hydrogen forms not only surface Had species but also bulk Had species.Bulk Had species is more thermal-unstable than surface Had species on Pt(111),suggesting that bulk Had species is more energetic.This kind of weakly- adsorbed bulk Had species might be the active hydrogen species in the Pt-catalyzed hydrogenation reactions.展开更多
基金Supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘The liquid phase ring-opening of octamethylcy-clotetrasiloxane(D_4) was investigated over Pt-H_2SO_4/Zrmontmorillonite catalyst. Montmorillonite(Mt), Zr-Mt, H_2SO_4/Mt, H_2SO_4/Zr-Mt and Pt-H_2SO_4/Zr-Mt were also detected for evaluation. The catalysts were characterized by X-ray fluorescence, X-ray diffraction, nitrogen adsorption–desorption, NH_3-TPD and pyridine-FTIR measurements. In comparison to activate clay which is used in the industry of catalyst, Zr-Mt catalyst displayed stronger acidity and more excellent catalytic activity in the polymerization of D_4, polymethylhydrosiloxane(D_4 H) and hexamethyldisiloxane(MM) to low-hydro silicone oil. Relative to Zr-Mt, the acidity of H_2SO_4/Zr-Mt was noticeably improved and the catalyst exhibited a higher capability of ring-opening of D_4 conversion and yield of low-hydro silicone oil. To enhance the stability of H_2SO_4/Zr-Mt catalyst, a small amount of metals(Pt) was doped. The nitrogen adsorption–desorption results indicated that pore textural parameters of the Pt-H_2SO_4/Zr-Mt had not changed with larger specific surface area. Compared with H_2SO_4/Zr-Mt, the total acidity of Pt-H_2SO_4-Zr/Mt catalyst retained, but the content of the Br?nsted acid increased and the content of the Lewis acid decreased. The Pt-H_2SO_4-Zr/Mt catalyst displayed higher catalyst reproducibility. After 40 h reaction of polymerization, the yield of low-hydro silicone oil decreased from 93% to 42% over H_2SO_4/Zr-Mt catalyst, while the yield of low-hydro silicone oil reduced from 93% to 78%over Pt-H_2SO_4/Zr-Mt catalyst. A sharp decrease in catalytic activity after 35 h of Pt-H_2SO_4/Zr-Mt catalyst was detected. Furthermore, Pt-H_2SO_4/Zr-Mt was completely regenerated under appropriate condition and appeared good repeatability in the D_4, D_4 Hand MM to low-hydro silicone oil.
基金supported by the National Natural Science Foundation of China (21703050, 21271153, 21373181)China Postdoctoral Science Foun‐dation (512200‐X91701)Special Research Foundation of Young Teachers in Hangzhou Dianzi University (ZX150204307002/032)~~
基金supported by the National Natural Science Foundation of China (No. 20807027)the National High-Tech Research and Development Program (863) of China (No. 2010AA064907)
文摘Pt supported on mesoporous silica SBA-15 was investigated as a catalyst for low temperature selective catalytic reduction（SCR） of NO by C 3 H 6 in the presence of excess oxygen.The prepared catalysts were characterized by means of XRD,BET surface area,TEM,NO-TPD,NO/C 3 H 6-TPO,NH 3-TPD,XPS and 27 Al MAS NMR.The effects of Pt loading amount,O 2 /C 3 H 6 concentration,and incorporation of Al into SBA-15 have been studied.It was found that the removal efficiency increased significantly after Pt loading,but an optimal loading amount was observed.In particular,under an atmosphere of 150 ppm NO,150 ppm C 3 H 6,and 18 vol.% O 2,0.5% Pt/SBA-15 showed remarkably high catalytic performance giving 80.1% NOx reduction and 87.04% C 3 H 6 conversion simultaneously at 140°C.The enhanced SCR activity of Pt/SBA-15 is associated with its outstanding oxidation activities of NO to NO 2 and C 3 H 6 to CO 2 in low temperature range.The research results also suggested that higher concentration of O 2 and higher concentration of C 3 H 6 favored NO removal.The incorporation of Al into SBA-15 improved catalytic performance,which could be ascribed to the enhancement of catalyst surface acidity caused by tetrahedrally coordinated AlO 4.Moreover,the catalysts could be easily reused and possessed good stability.
基金the National Natural Science Foundation of China(Grant No.20503027)Talent Program of Chinese Academy of SciencesChina Postdoc-toral Science Foundation(Grant No.2005038479)
文摘Employing hot tungsten filament to thermal dissociate molecular hydrogen,we generated gas phase atomic hydrogen under ultra-high vacuum(UHV)conditions and investigated its interaction with Pt(111) surface.Thermal desorption spectroscopy(TDS)results demonstrate that adsorption of molecular hy- drogen on Pt(111)forms surface Had species whereas adsorption of atomic hydrogen forms not only surface Had species but also bulk Had species.Bulk Had species is more thermal-unstable than surface Had species on Pt(111),suggesting that bulk Had species is more energetic.This kind of weakly- adsorbed bulk Had species might be the active hydrogen species in the Pt-catalyzed hydrogenation reactions.
