不同硅铝摩尔比Pt@SOD催化氢与氧直接合成过氧化氢的性能
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摘要
在原位合成不同n(Si)∶n(Al)的方钠石(sodalites,SOD)过程中加入Pt的前驱体Pt(NH3)4Cl2,制备得到不同n(Si)∶n(Al)、封装Pt的方钠石(Pt@SOD),并通过原子吸收光谱、XRD、SEM、EDS、TEM、XPS等测试方法对Pt粒子封装效果进行表征。由表征之间的相互印证可以说明:Pt@SOD系列样品的Pt封装效果较好,Pt粒子在方钠石中均匀分散且粒径较为统一,但是表面仍有微量的Pt残留。将该系列样品作为催化剂用于H2、O2直接制备过氧化氢反应,Pt粒子较好的封装效果以及方钠石微小孔道(半径0.28nm)可有效阻止O2分子与封装的Pt粒子接触,限制副反应产物H2O生成,且H2可自由扩散,与Pt活性位点接触,从而使得Pt@SOD系列样品在H2、O2直接制备过氧化氢反应中,表现出了较好的H2O2选择性。其中,Pt@SOD-(Ⅱ)-n(Si)∶n(Al)=3混合n(Si)∶n(Al)=25的HZSM-5为催化剂,在2℃下反应1h时H2O2选择性达到44%.
Pt(NH3)4Cl2 was added as precursor of Pt in the in-situ synthesis of sodalite with different n(Si)∶n(Al)ratio to prepare different n(Si)∶n(Al)ratio of samples with good Pt encapsulation.The Pt@SOD samples were characterized by XPS,EDS and so on as having good Pt encapsulating effect,with trace amount of Pt on sodalite surface.The Pt@SOD series was further used in the direct synthesis of hydrogen peroxide(DSHP)from hydrogen and oxygen reaction to prevent the side reaction of H2 O formation,which is due to the good effect of Pt encapsulation and SOD pore size about 0.28 nm to prevent O2 contacting with Pt particles.The H2O2 selectivity of Pt@SOD-(Ⅱ)-Si:Al=3 mixed with n(Si)∶n(Al)=25 HZSM-5sample at 2 ℃DSHP reaction for 1hwas 44%.
Pt(NH3)4Cl2 was added as precursor of Pt in the in-situ synthesis of sodalite with different n(Si)∶n(Al)ratio to prepare different n(Si)∶n(Al)ratio of samples with good Pt encapsulation.The Pt@SOD samples were characterized by XPS,EDS and so on as having good Pt encapsulating effect,with trace amount of Pt on sodalite surface.The Pt@SOD series was further used in the direct synthesis of hydrogen peroxide(DSHP)from hydrogen and oxygen reaction to prevent the side reaction of H2 O formation,which is due to the good effect of Pt encapsulation and SOD pore size about 0.28 nm to prevent O2 contacting with Pt particles.The H2O2 selectivity of Pt@SOD-(Ⅱ)-Si:Al=3 mixed with n(Si)∶n(Al)=25 HZSM-5sample at 2 ℃DSHP reaction for 1hwas 44%.
引文
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[22] TILEKARATNE A,SIMONOVIS,J P,LPEZ FAGU'NDEZ M F,et al.Operando studies of the catalytic hydrogenation of ethylene on Pt(111)single crystal surfaces[J].ACS Catalysis,2012,2(11):2259-2268.
[23] PICCININI M,NTAINJUA E,EDWARDS J K,et al.Effect of the reaction conditions on the performance of Au-Pd/TiO2catalyst for the direct synthesis of hydrogen peroxide[J].Physical Chemistry Chemical Physics,2010,12(10):2488-2492.
[2] VAN SPEYBROECK V,HEMELSOET K,JOOS L,et al.Advances in theory and their application within the field of zeolite chemistry[J].Chemical Society Reviews,2015,44(20):7044-7111.
[3] XU R,PANG W,YU J,et al.Chemistry of zeolites and related porous materials:synthesis and structure[M].Singapore:John Wiley&Sons(Asia)Pte Ltd,2007.
[4] PAULING L.The structure of sodalite and helvite[J].Kristallogr,1930,74:213-225.
[5] GOUZINIS A,TSAPATSIS M.On the preferred orientation and microstructural manipulation of molecular sieve films prepared by secondary growth[J].Chemistry of Materials,1998,10(9):2497-2504.
[6] JULBE A,MOTUZAS J,CAZEVIELLE F,et al.Synthesis of sodalite/αAl2O3composite membranes by microwave heating[J].Separation and Purification Technology,2003,32(1/3):139-149.
[7] LEE S R,SON Y H,JULBE A,et al.Vacuum seeding and secondary growth route to sodalite membrane[J].Thin Solid Films,2006,495(1/2):92-96.
[8] GOEL S,ZONES S I,IGLESIA E.Encapsulation of metal clusters within MFI via interzeolite transformations and direct hydrothermal syntheses and catalytic consequences of their confinement[J].Journal of the American Chemical Society,2014,136(43):15280-15290.
[9] WU Z,GOEL S,CHOI M,et al.Hydrothermal synthesis of LTA-encapsulated metal clusters and consequences for catalyst stability,reactivity,and selectivity[J].Journal of Catalysis,2014,311(3):458-468.
[10] NIEMANTSVERDRIET H,VAN HELDEN P,HENSEN E,et al.Catalysis for fuels:general discussion[J].Faraday Discussions,2017,197:165-205.
[11] HASSAN I,GRUNDY H D.Structure of basic sodalite Na8Al6Si6O24(OH)2·2H2O[J].Acta Crystallographica,1983,39(1):3-5.
[12] PAN L,LIU W,CHEN W,et al.Crystal structure and band gap studies of sodalite:experimental and calculated results[J].Journal of Molecular Structure,2016,1106:59-63.
[13] ASTALA R,AUERBACH S M,MONSON P A.Density functional theory study of silica zeolite structures:stabilities and mechanical properties of SOD,LTA,CHA,MOR,and MFI[J].The Journal of Physical Chemistry B,2004,108(26):9208-9215.
[14] ROBBEN L,WOLPMANN M,BOTTKE P,et al.Disordered but primitive gallosilicate hydro-sodalite:Structure and thermal behaviour of a framework with novel cation distribution[J].Microporous and Mesoporous Materials,2018,256:206-213.
[15]鲁桂梅.方钠石的合成及其吸附性能的研究[D].大连:大连理工大学,2008.LU G.Study on synthesis of sodalite and its Adsorpiton propreties[D].Dalian:Dalian University of Teachnology,2008.
[16] BAERLOCHER C,MCCUSKER L B,OLSON D H.Atlas of zeolite framework types[M].Amsterdam:Elsevier,2007.
[17] YAO J,ZHANG L,WANG H.Synthesis of nanocrystalline sodalite with organic additives[J].Materials Letters,2008,62(24):4028-4030.
[18] LUGER S,FELSCHE J.FISCHER P.Structure of hydroxysodalite Na8[AlSiO4]6(OH)2,apowder neutron diffraction study at 8K[J].Acta Crystallographica,1987,43(1):1-3.
[19] BELVISO C,CAVALCANTE F,NICEFORO G.,et al.Sodalite,faujasite and A-type zeolite from 2∶1dioctahedral and 2∶1∶1trioctahedral clay minerals.A singular review of synthesis methods through laboratory trials at a low incubation temperature[J].Powder Technology,2017,320:483-497.
[20] ZAERA F.Key unanswered questions about the mechanism of olefin hydrogenation catalysis by transition-metal surfaces:a surface-science perspective[J].Physical Chemistry Chemical Physics,2013,15(29):11988-12003.
[21] ZAERA F.The surface chemistry of metal-based hydrogenation catalysis[J].ACS Catalysis,2017,7(8):4947-4967.
[22] TILEKARATNE A,SIMONOVIS,J P,LPEZ FAGU'NDEZ M F,et al.Operando studies of the catalytic hydrogenation of ethylene on Pt(111)single crystal surfaces[J].ACS Catalysis,2012,2(11):2259-2268.
[23] PICCININI M,NTAINJUA E,EDWARDS J K,et al.Effect of the reaction conditions on the performance of Au-Pd/TiO2catalyst for the direct synthesis of hydrogen peroxide[J].Physical Chemistry Chemical Physics,2010,12(10):2488-2492.