Shape-selective catalysts for the disproportionation of toluene were prepared by the modification of the cylinder-shaped ZSM-5 zeolite extrudates with chemical liquid deposition with TEOS （tetraethyl orthosilicate）....Shape-selective catalysts for the disproportionation of toluene were prepared by the modification of the cylinder-shaped ZSM-5 zeolite extrudates with chemical liquid deposition with TEOS （tetraethyl orthosilicate）.Various parameters for preparing catalysts were changed to investigate the suitable conditions.The resulting cata-lysts were tested in a pressured fixed bed reactor and characterized by SEM （scanning electron microscopy）.The conversion of toluene and para-xylene selectivity were influenced remarkably by the n（SiO2）/n（Al2O3） ratio of ZSM-5 zeolite,the type and amount of deposition agent,acid and solvent used,and the time and cycle of deposition treatment.TEOS was proved to be a more efficient agent than the conventional polysiloxanes when the deposition amount was low.The catalyst prepared at the suitable conditions exhibited a high para-xylene selectivity of 91.1% with considerable high conversion of 25.6%.SEM analyses confirmed the formation of a layer of amorphous silica on the external surface of ZSM-5 zeolie crystals,which was responsible for the highly enhanced shape-selectivity.展开更多
血压是指血液对血管壁的侧压,血压分为收缩压（高压）和舒张压（低压）。《中国高血压防治指南》（2005年修订版）将高血压定义为：在未用抗高血压药情况下,收缩压140 mmHg和/或舒张压90 mm Hg[1]。高血压是我国最常见的心血管疾病,其...血压是指血液对血管壁的侧压,血压分为收缩压（高压）和舒张压（低压）。《中国高血压防治指南》（2005年修订版）将高血压定义为：在未用抗高血压药情况下,收缩压140 mmHg和/或舒张压90 mm Hg[1]。高血压是我国最常见的心血管疾病,其发生率在成年人中高达20%,并且高血压在我国的发病率呈逐年上升的趋势。展开更多
基金Supported by the Key Natural Science Foundation for Universities of Jiangsu Province（06KJA53012） the National Natural Science Foundation of China（20776069 20976084）
文摘Shape-selective catalysts for the disproportionation of toluene were prepared by the modification of the cylinder-shaped ZSM-5 zeolite extrudates with chemical liquid deposition with TEOS （tetraethyl orthosilicate）.Various parameters for preparing catalysts were changed to investigate the suitable conditions.The resulting cata-lysts were tested in a pressured fixed bed reactor and characterized by SEM （scanning electron microscopy）.The conversion of toluene and para-xylene selectivity were influenced remarkably by the n（SiO2）/n（Al2O3） ratio of ZSM-5 zeolite,the type and amount of deposition agent,acid and solvent used,and the time and cycle of deposition treatment.TEOS was proved to be a more efficient agent than the conventional polysiloxanes when the deposition amount was low.The catalyst prepared at the suitable conditions exhibited a high para-xylene selectivity of 91.1% with considerable high conversion of 25.6%.SEM analyses confirmed the formation of a layer of amorphous silica on the external surface of ZSM-5 zeolie crystals,which was responsible for the highly enhanced shape-selectivity.
文摘血压是指血液对血管壁的侧压,血压分为收缩压（高压）和舒张压（低压）。《中国高血压防治指南》（2005年修订版）将高血压定义为：在未用抗高血压药情况下,收缩压140 mmHg和/或舒张压90 mm Hg[1]。高血压是我国最常见的心血管疾病,其发生率在成年人中高达20%,并且高血压在我国的发病率呈逐年上升的趋势。
