采用水热法成功将镁(Mg)引入ZSM-5分子筛骨架结构中,系统考察了Mg含量对分子筛孔的结构、酸性质、骨架铝(framework aluminum,Al_(F))分布及催化生物乙醇制丙烯(bioethanol to propylene,ETP)反应性能的影响。结果表明,随着Mg含量的增加...采用水热法成功将镁(Mg)引入ZSM-5分子筛骨架结构中,系统考察了Mg含量对分子筛孔的结构、酸性质、骨架铝(framework aluminum,Al_(F))分布及催化生物乙醇制丙烯(bioethanol to propylene,ETP)反应性能的影响。结果表明,随着Mg含量的增加,分子筛介孔体积显著增大,结晶度略有下降。氨气程序升温脱附(NH3-TPD)和吡啶红外(Py-IR)分析结果显示,Mg的引入有效降低了分子筛总酸量和强酸强度,同时提高了Brønsted酸的比例。固体核磁共振(^(27)Al MAS NMR)和紫外可见漫反射光谱(UV-Vis DRS)表明,Mg的引入促使Al_(F)从通道交叉处向正弦或直通道迁移,并减少了铝对(aluminum pair,Al_(pair))的形成。催化反应评价结果显示,适量Mg改性的分子筛(2-MgHZ5)表现出最优的ETP性能,丙烯选择性从改性前的ZSM-5(HZ5)的26.8%提高至29.5%,丙烯选择性维持在不低于10%的时间更是从HZ5的15 h显著延长至30 h,这归因于其适中的酸强度、丰富的介孔结构以及Al分布的优化有效抑制了芳烃循环和积碳生成,促进了烯烃-环戊二烯循环路径。展开更多
Nanosized alumina powders were prepared from Al(NO3)3·9H2O and (NH4)2CO3 through the synthesis of ammonium aluminium carbonate hydroxide (AACH) and followed by calcination. TG DTA, XRD, TEM and BET were employed ...Nanosized alumina powders were prepared from Al(NO3)3·9H2O and (NH4)2CO3 through the synthesis of ammonium aluminium carbonate hydroxide (AACH) and followed by calcination. TG DTA, XRD, TEM and BET were employed to study the process of AACH thermal decomposition and to characterize the products obtained. The results show that high purity (99.97%) and nanosized spherical α Al2O3 powders with the diameter of 40～50nm and BET surface area 32.5m2·g-1 can be obtained by calcining AACH at 1150℃for 1.5h, the sequence of phase transformation during calcination was AACH →amorphous Al2O3 →γ Al2O3 →α Al2O3, and the activation energy of AACH decomposition is (115±5)kJ·mol-1.展开更多
Aluminas were prepared by precipitation of aqueous aluminum nitrate solution using ammonium carbonate and ammonium hydroxide as precipitation agent respectively. The prepared samples were characterized by TG/DTA, XRD,...Aluminas were prepared by precipitation of aqueous aluminum nitrate solution using ammonium carbonate and ammonium hydroxide as precipitation agent respectively. The prepared samples were characterized by TG/DTA, XRD, surface area, pore volume and average pore diameter and the results were compared. The activity and stability of the close-coupled catalysts supported by aluminas prepared by different precipitating agent were compated. The alumina formed by ammonium carbonate showed larger surface area, pore volume, average pore diameter, higher thermal stability and better support property than that formed by ammonium hydroxide. The precusor of NH4Al(OH)2CO3 in the ammonium cabonate process was responsible for the difference.展开更多
文摘采用水热法成功将镁(Mg)引入ZSM-5分子筛骨架结构中,系统考察了Mg含量对分子筛孔的结构、酸性质、骨架铝(framework aluminum,Al_(F))分布及催化生物乙醇制丙烯(bioethanol to propylene,ETP)反应性能的影响。结果表明,随着Mg含量的增加,分子筛介孔体积显著增大,结晶度略有下降。氨气程序升温脱附(NH3-TPD)和吡啶红外(Py-IR)分析结果显示,Mg的引入有效降低了分子筛总酸量和强酸强度,同时提高了Brønsted酸的比例。固体核磁共振(^(27)Al MAS NMR)和紫外可见漫反射光谱(UV-Vis DRS)表明,Mg的引入促使Al_(F)从通道交叉处向正弦或直通道迁移,并减少了铝对(aluminum pair,Al_(pair))的形成。催化反应评价结果显示,适量Mg改性的分子筛(2-MgHZ5)表现出最优的ETP性能,丙烯选择性从改性前的ZSM-5(HZ5)的26.8%提高至29.5%,丙烯选择性维持在不低于10%的时间更是从HZ5的15 h显著延长至30 h,这归因于其适中的酸强度、丰富的介孔结构以及Al分布的优化有效抑制了芳烃循环和积碳生成,促进了烯烃-环戊二烯循环路径。
文摘Nanosized alumina powders were prepared from Al(NO3)3·9H2O and (NH4)2CO3 through the synthesis of ammonium aluminium carbonate hydroxide (AACH) and followed by calcination. TG DTA, XRD, TEM and BET were employed to study the process of AACH thermal decomposition and to characterize the products obtained. The results show that high purity (99.97%) and nanosized spherical α Al2O3 powders with the diameter of 40～50nm and BET surface area 32.5m2·g-1 can be obtained by calcining AACH at 1150℃for 1.5h, the sequence of phase transformation during calcination was AACH →amorphous Al2O3 →γ Al2O3 →α Al2O3, and the activation energy of AACH decomposition is (115±5)kJ·mol-1.
文摘Aluminas were prepared by precipitation of aqueous aluminum nitrate solution using ammonium carbonate and ammonium hydroxide as precipitation agent respectively. The prepared samples were characterized by TG/DTA, XRD, surface area, pore volume and average pore diameter and the results were compared. The activity and stability of the close-coupled catalysts supported by aluminas prepared by different precipitating agent were compated. The alumina formed by ammonium carbonate showed larger surface area, pore volume, average pore diameter, higher thermal stability and better support property than that formed by ammonium hydroxide. The precusor of NH4Al(OH)2CO3 in the ammonium cabonate process was responsible for the difference.
