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
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.
