The present study is focused on the influence of a routine step, washing, following the preparation of calcined rare earth exchanged Y zeolite, on its hydrothermal stability. The hydrothermal stability of REY products...The present study is focused on the influence of a routine step, washing, following the preparation of calcined rare earth exchanged Y zeolite, on its hydrothermal stability. The hydrothermal stability of REY products, which were washed by different reagents, was observed and characterized by XRD, ICP, NMR, etc. The results reveal that the amount and the chemical type of the acidic media used for washing can significantly influence the content of remaining non-framework aluminum (NFA) and consequently further affect the hydrothermal stability of the washed REY products. The content of remaining non-framework aluminum can be well correlated with the crystallinity of REY products.展开更多
分析Ti-β分子筛催化1-己烯环氧化反应过程中的失活的原因,研究其失活过程及再生方法;采用^(13)C MAS NMR和GC-MS等手段分析Ti-β分子筛的积炭情况,并采用XPS、UV-Vis和EDX等手段研究其钛物种变化;进一步以二甲基亚砜溶剂处理失活Ti-β...分析Ti-β分子筛催化1-己烯环氧化反应过程中的失活的原因,研究其失活过程及再生方法;采用^(13)C MAS NMR和GC-MS等手段分析Ti-β分子筛的积炭情况,并采用XPS、UV-Vis和EDX等手段研究其钛物种变化;进一步以二甲基亚砜溶剂处理失活Ti-β分子筛,对其进行再生研究。结果表明:Ti-β分子筛循环使用10次以后,1-己烯转化率降低至新鲜剂的30%以下;在此过程中,Ti-β分子筛中的部分骨架钛转化为非骨架钛,同时1,2-己二醇副产物堵塞孔道或者覆盖活性中心,两者共同导致Ti-β分子筛失活。以二甲基亚砜在160℃条件下对失活的Ti-β分子筛处理可以脱除大部分吸附的1,2-己二醇,使其催化1-己烯环氧化反应的活性恢复至新鲜剂的83%。展开更多
采用27Al MAS NMR、N2吸附-脱附、IR等表征技术及XRD Rietveld结构精修的方法,通过清除和交换引入非骨架铝,探讨了USY沸石中非骨架铝的形态。结果表明,27Al MAS NMR化学位移为0的非骨架铝以游离在超笼中的非骨架铝为主,化学位移为30-50...采用27Al MAS NMR、N2吸附-脱附、IR等表征技术及XRD Rietveld结构精修的方法,通过清除和交换引入非骨架铝,探讨了USY沸石中非骨架铝的形态。结果表明,27Al MAS NMR化学位移为0的非骨架铝以游离在超笼中的非骨架铝为主,化学位移为30-50的非骨架铝与沸石骨架存在键合作用;晶体学可识别的离子态非骨架铝存在于方钠石笼的SⅠ′和SⅡ′位置,其中,SⅠ′位置的非骨架铝与沸石骨架3个O3原子及与其配位的三重轴的O形成不稳定的四配位结构,SⅡ′位置的Al不与沸石骨架O形成配位。超笼中未发现可识别的离子态非骨架铝。聚合态非骨架铝的存在将堵塞沸石孔道,影响微孔吸附性能,并掩盖B酸中心。清除非骨架铝后,可以使沸石孔道畅通,使B酸中心得到恢复。展开更多
文摘The present study is focused on the influence of a routine step, washing, following the preparation of calcined rare earth exchanged Y zeolite, on its hydrothermal stability. The hydrothermal stability of REY products, which were washed by different reagents, was observed and characterized by XRD, ICP, NMR, etc. The results reveal that the amount and the chemical type of the acidic media used for washing can significantly influence the content of remaining non-framework aluminum (NFA) and consequently further affect the hydrothermal stability of the washed REY products. The content of remaining non-framework aluminum can be well correlated with the crystallinity of REY products.
文摘分析Ti-β分子筛催化1-己烯环氧化反应过程中的失活的原因,研究其失活过程及再生方法;采用^(13)C MAS NMR和GC-MS等手段分析Ti-β分子筛的积炭情况,并采用XPS、UV-Vis和EDX等手段研究其钛物种变化;进一步以二甲基亚砜溶剂处理失活Ti-β分子筛,对其进行再生研究。结果表明:Ti-β分子筛循环使用10次以后,1-己烯转化率降低至新鲜剂的30%以下;在此过程中,Ti-β分子筛中的部分骨架钛转化为非骨架钛,同时1,2-己二醇副产物堵塞孔道或者覆盖活性中心,两者共同导致Ti-β分子筛失活。以二甲基亚砜在160℃条件下对失活的Ti-β分子筛处理可以脱除大部分吸附的1,2-己二醇,使其催化1-己烯环氧化反应的活性恢复至新鲜剂的83%。
文摘采用27Al MAS NMR、N2吸附-脱附、IR等表征技术及XRD Rietveld结构精修的方法,通过清除和交换引入非骨架铝,探讨了USY沸石中非骨架铝的形态。结果表明,27Al MAS NMR化学位移为0的非骨架铝以游离在超笼中的非骨架铝为主,化学位移为30-50的非骨架铝与沸石骨架存在键合作用;晶体学可识别的离子态非骨架铝存在于方钠石笼的SⅠ′和SⅡ′位置,其中,SⅠ′位置的非骨架铝与沸石骨架3个O3原子及与其配位的三重轴的O形成不稳定的四配位结构,SⅡ′位置的Al不与沸石骨架O形成配位。超笼中未发现可识别的离子态非骨架铝。聚合态非骨架铝的存在将堵塞沸石孔道,影响微孔吸附性能,并掩盖B酸中心。清除非骨架铝后,可以使沸石孔道畅通,使B酸中心得到恢复。
