Direct synthesis of hydrogen peroxide(DSHP)was studied over Pd loaded on HZSM-5 nanosheets(Pd/ZN).Pd nanoparticles with average size of ca.4.3 nm were introduced into the adjacent nanosheet layers(thickness of ca.2.9 ...Direct synthesis of hydrogen peroxide(DSHP)was studied over Pd loaded on HZSM-5 nanosheets(Pd/ZN).Pd nanoparticles with average size of ca.4.3 nm were introduced into the adjacent nanosheet layers(thickness of ca.2.9 nm)by impregnation method.Pd/ZN with theoretical Si/Al molar ratio of 25 showed the highest selectivity for H2O2 among the prepared catalysts,together with highest formation rate of H2O2(38.0 mmol·(g cat)^-1·h^-1),1.9 times than that of Pd supported on conventional HZSM-5 zeolite(Pd/CZ-50).Better catalytic performance of nanosheet catalysts was attributed to the promoted Pd dispersion which promoted H2 dissociation,more BrΦnsted acid sites and stronger metal-support interaction which inhibited the dissociation of O-O bond in H2O2.The embedded structure sufficiently protected the Pd nanoparticles by space confinement which restrained the Pd leaching,leading to a better catalytic stability with 90%activity retained after 3 cycles,which was almost 3 times than that of Pd/CZ-50(30.4%activity retained).展开更多
分别以硅/铝摩尔比为40、200、300、400的ZSM-5分子筛为载体,以金属镧为活性组分,制备一系列催化裂化(FCC)轻汽油异构化/芳构化催化剂,通过X射线衍射(XRD)、N_(2)吸附-脱附、^(27)Al MAS NMR、氨气程序升温脱附(NH_(3)-TPD)、吡啶红外吸...分别以硅/铝摩尔比为40、200、300、400的ZSM-5分子筛为载体,以金属镧为活性组分,制备一系列催化裂化(FCC)轻汽油异构化/芳构化催化剂,通过X射线衍射(XRD)、N_(2)吸附-脱附、^(27)Al MAS NMR、氨气程序升温脱附(NH_(3)-TPD)、吡啶红外吸附(Py-FTIR)、扫描电镜(SEM)等手段对其进行表征。以FCC轻汽油为原料,研究了La/ZSM-5分子筛硅/铝摩尔比变化对异构化/芳构化反应性能的影响。结果表明:随着ZSM-5硅/铝摩尔比的增加,其酸强度逐渐降低,B酸与L酸酸量比值减小,芳烃产率呈现先增加后减少的趋势;当硅/铝摩尔比为200时,Bronsted(B)酸与Lewis(L)酸酸量比值最低,FCC轻汽油异构化/芳构化性能最高;在反应温度380℃、压力1.0 MPa、氢/油体积比100和体积空速1.0 h^(-1)的条件下,La/ZSM-5-200分子筛催化剂作用下异构化/芳构化产品与反应原料相比,烯烃体积分数降低32.81百分点,异构烷烃体积分数增加18.24百分点,芳烃体积分数增加到5.97%,辛烷值降低5.38个单位,达成以芳构/异构反应为主的大幅度降烯烃的目标,为京Ⅵ(B)汽油标准的实施提供了技术支持。展开更多
基金Financial supports by the National Natural Science Foundation of China(21776210)Science and Technology Research Project of Henan Province(No.202102210048)。
文摘Direct synthesis of hydrogen peroxide(DSHP)was studied over Pd loaded on HZSM-5 nanosheets(Pd/ZN).Pd nanoparticles with average size of ca.4.3 nm were introduced into the adjacent nanosheet layers(thickness of ca.2.9 nm)by impregnation method.Pd/ZN with theoretical Si/Al molar ratio of 25 showed the highest selectivity for H2O2 among the prepared catalysts,together with highest formation rate of H2O2(38.0 mmol·(g cat)^-1·h^-1),1.9 times than that of Pd supported on conventional HZSM-5 zeolite(Pd/CZ-50).Better catalytic performance of nanosheet catalysts was attributed to the promoted Pd dispersion which promoted H2 dissociation,more BrΦnsted acid sites and stronger metal-support interaction which inhibited the dissociation of O-O bond in H2O2.The embedded structure sufficiently protected the Pd nanoparticles by space confinement which restrained the Pd leaching,leading to a better catalytic stability with 90%activity retained after 3 cycles,which was almost 3 times than that of Pd/CZ-50(30.4%activity retained).
文摘分别以硅/铝摩尔比为40、200、300、400的ZSM-5分子筛为载体,以金属镧为活性组分,制备一系列催化裂化(FCC)轻汽油异构化/芳构化催化剂,通过X射线衍射(XRD)、N_(2)吸附-脱附、^(27)Al MAS NMR、氨气程序升温脱附(NH_(3)-TPD)、吡啶红外吸附(Py-FTIR)、扫描电镜(SEM)等手段对其进行表征。以FCC轻汽油为原料,研究了La/ZSM-5分子筛硅/铝摩尔比变化对异构化/芳构化反应性能的影响。结果表明:随着ZSM-5硅/铝摩尔比的增加,其酸强度逐渐降低,B酸与L酸酸量比值减小,芳烃产率呈现先增加后减少的趋势;当硅/铝摩尔比为200时,Bronsted(B)酸与Lewis(L)酸酸量比值最低,FCC轻汽油异构化/芳构化性能最高;在反应温度380℃、压力1.0 MPa、氢/油体积比100和体积空速1.0 h^(-1)的条件下,La/ZSM-5-200分子筛催化剂作用下异构化/芳构化产品与反应原料相比,烯烃体积分数降低32.81百分点,异构烷烃体积分数增加18.24百分点,芳烃体积分数增加到5.97%,辛烷值降低5.38个单位,达成以芳构/异构反应为主的大幅度降烯烃的目标,为京Ⅵ(B)汽油标准的实施提供了技术支持。
