一步合成CoSAPO-5分子筛及其在苯乙烯空气环氧化中的催化研究
|
摘要
本研究通过一步水热转动法原位合成了CoSAPO-5分子筛,通过两步法(先合成SAPO-5后经离子交换或浸渍法负载Co源)制备了Co/SAPO-5催化剂. XRD表征可看出所合成分子筛具有AFI的特征衍射峰,扫描电镜可看出CoSAPO-5分子筛晶体呈六方棱柱型,固体紫外图谱表明钴源存在于CoSAPO-5分子筛中. CoSAPO-5焙烧后显示出良好催化活性,催化苯乙烯空气环氧化产率为72. 2%;而Co/SAPO-5对苯乙烯的催化环氧化产率最高为56. 9%.比较两种制备方法,一步转动法合成CoSAPO-5操作简单,更利于钴源分散在骨架活性位置,所制取催化剂催化烯烃环氧化产率更高,综合表明一步转动法在催化剂制备中有很大的优势.
CoSAPO-5 molecular sieve has been one-step synthesized by rotating hydrothermal method,by which CoSAPO-5 catalyst has been prepared by calcination and shows much better catalytic activity compared with Co/SAPO-5 catalyst prepared by Co~(2+) ion-exchange or impregnation to introduce cobalt into SAPO-5(two-step method). CoSAPO-5 zeolite shows hexagonal morphology. UV-vis spectra indicate that Co~(2+) ions are present in CoSAPO-5 catalyst. CoSAPO-5 catalyst can converse 93. 2% styrene with 72. 2% epoxide yield,however,the epoxide yield is only 57% over Co/SAPO-5. Comparing with two-step methods,one-step method is more simple and easy to be conducted; moreover,CoSAPO-5 synthesized by one-step method facilitates the dispersion of Cobalt in the framework of zeolite,which is proven to be an efficient catalyst preparation method.
CoSAPO-5 molecular sieve has been one-step synthesized by rotating hydrothermal method,by which CoSAPO-5 catalyst has been prepared by calcination and shows much better catalytic activity compared with Co/SAPO-5 catalyst prepared by Co~(2+) ion-exchange or impregnation to introduce cobalt into SAPO-5(two-step method). CoSAPO-5 zeolite shows hexagonal morphology. UV-vis spectra indicate that Co~(2+) ions are present in CoSAPO-5 catalyst. CoSAPO-5 catalyst can converse 93. 2% styrene with 72. 2% epoxide yield,however,the epoxide yield is only 57% over Co/SAPO-5. Comparing with two-step methods,one-step method is more simple and easy to be conducted; moreover,CoSAPO-5 synthesized by one-step method facilitates the dispersion of Cobalt in the framework of zeolite,which is proven to be an efficient catalyst preparation method.
引文
[1]Tang Q H,Zhang Q H,Wu H L,et al.Epoxidation of styrene with molecular oxygen catalyzed by cobalt(II)-containing molecular sieves[J].J Catal,2005,230:384-397.
[2]Tang B,Lu X H,Zhou D,et al.Highly efficient epoxidation of styrene andα-pinene with air over Co2+-exchanged ZSM-5and Beta zeolites[J].Catal Commun,2012,21:68-71.
[3]Tang B,Lu X H,Zhou D,et al.Co2+-exchanged SAPO-5 and SAPO-34 as efficient heterogeneous catalysts for aerobic epoxidation of alkenes[J].Catal Commun,2013,31:42-47.
[4]章天骏,周丹,夏坤,等.微波辅助加热分子筛催化苯乙烯空气环氧化的研究[J].湖北大学学报(自然科学版),2016(5):461-464.
[5]Tang Q H,Wang Y,Liang J,et al.Co2+-Exchanged faujasite zeolites as efficient heterogeneous catalysts for epoxidation of styrene with molecular oxygen[J].Chem Commun,2004(4):440-441.
[6]夏坤,王艺,周丹,等.Co SAPO-5分子筛的快速合成及高效催化α-蒎烯与空气环氧化反应[J].高等学校化学学报,2018(5):941-948.
[7]Zhang X,Sun G,Yang R.Synthesis of zeolite Na A at low temperatures:characterization,cobalt Exchange and enhanced catalytic activity of styrene epoxidation[J].Petroleum Chemistry,2017,57(12):1093-1098.
[8]Wei X L,Lu X H,Zhang T J,et al.Synthesis and catalytic application of SAPO-5 by dry-gel conversion for the epoxidation of styrene with air[J].Micropor Mesopor Mater,2015,214:80-87.
[9]Zhou D,Tang B,Lu X H,et al.Co2+-exchanged MOR and 5A zeolites as efficient solid catalysts for the epoxidation of styrene with air[J].Catal Commun,2014,45,124-128.
[10]Zhou D,Lu X H,Xu J,et al.Dry gel conversion method for the synthesis of organic-inorganic hybrid MOR zeolites with modifiable catalytic activities[J].Chemistry of Materials,2012,24(21):4160-4165.
[11]Qi B,Lu X H,Fang S Y,et al.Aerobic epoxidation of olefins over the composite catalysts of Co-ZSM-5(L)with bi-/tridentate Schiff-base ligands[J].Journal of Molecular Catalysis A:Chemical,2011,334(1-2):44-51.
[12]Xu G,Xia Q H,Lu XH,et al.Selectively catalytic epoxidation of styrene with dry air over the composite catalysts of CoZSM-5 coordinated with ligands[J].Journal of Molecular Catalysis A:Chemical,2007,266(1/2):180-187.
[13]Chen Z,Zhu S H,Li P Y,et al.Fabricating self-assembled SAPO-5 with tailored mesoporosity and acidity using a single template[J].Cryst Eng Comm,2017,19:5275-5284.
[2]Tang B,Lu X H,Zhou D,et al.Highly efficient epoxidation of styrene andα-pinene with air over Co2+-exchanged ZSM-5and Beta zeolites[J].Catal Commun,2012,21:68-71.
[3]Tang B,Lu X H,Zhou D,et al.Co2+-exchanged SAPO-5 and SAPO-34 as efficient heterogeneous catalysts for aerobic epoxidation of alkenes[J].Catal Commun,2013,31:42-47.
[4]章天骏,周丹,夏坤,等.微波辅助加热分子筛催化苯乙烯空气环氧化的研究[J].湖北大学学报(自然科学版),2016(5):461-464.
[5]Tang Q H,Wang Y,Liang J,et al.Co2+-Exchanged faujasite zeolites as efficient heterogeneous catalysts for epoxidation of styrene with molecular oxygen[J].Chem Commun,2004(4):440-441.
[6]夏坤,王艺,周丹,等.Co SAPO-5分子筛的快速合成及高效催化α-蒎烯与空气环氧化反应[J].高等学校化学学报,2018(5):941-948.
[7]Zhang X,Sun G,Yang R.Synthesis of zeolite Na A at low temperatures:characterization,cobalt Exchange and enhanced catalytic activity of styrene epoxidation[J].Petroleum Chemistry,2017,57(12):1093-1098.
[8]Wei X L,Lu X H,Zhang T J,et al.Synthesis and catalytic application of SAPO-5 by dry-gel conversion for the epoxidation of styrene with air[J].Micropor Mesopor Mater,2015,214:80-87.
[9]Zhou D,Tang B,Lu X H,et al.Co2+-exchanged MOR and 5A zeolites as efficient solid catalysts for the epoxidation of styrene with air[J].Catal Commun,2014,45,124-128.
[10]Zhou D,Lu X H,Xu J,et al.Dry gel conversion method for the synthesis of organic-inorganic hybrid MOR zeolites with modifiable catalytic activities[J].Chemistry of Materials,2012,24(21):4160-4165.
[11]Qi B,Lu X H,Fang S Y,et al.Aerobic epoxidation of olefins over the composite catalysts of Co-ZSM-5(L)with bi-/tridentate Schiff-base ligands[J].Journal of Molecular Catalysis A:Chemical,2011,334(1-2):44-51.
[12]Xu G,Xia Q H,Lu XH,et al.Selectively catalytic epoxidation of styrene with dry air over the composite catalysts of CoZSM-5 coordinated with ligands[J].Journal of Molecular Catalysis A:Chemical,2007,266(1/2):180-187.
[13]Chen Z,Zhu S H,Li P Y,et al.Fabricating self-assembled SAPO-5 with tailored mesoporosity and acidity using a single template[J].Cryst Eng Comm,2017,19:5275-5284.