单一模板剂两段变温法合成球状多级孔ZSM-5分子筛
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摘要
以四丙基氢氧化铵为单一模板剂,分别以硅酸或水玻璃为硅源,采用低温老化、高温晶化两段变温法合成球状多级孔ZSM-5分子筛;利用XRD、FT-IR、SEM、TEM以及氮气吸-脱附等手段对样品进行表征;并分析球状多级孔ZSM-5分子筛的形成机制。结果表明:所得多级孔ZSM-5分子筛产品主要由直径约为2μm的规则球状颗粒所组成,而其颗粒内的晶间介孔和大孔主要来自于棒状纳米晶堆积而成的;与商业ZSM-5分子筛相比,该产品具有较高的相对结晶度,同时具有更大的BET总比表面积、介孔比表面积和介孔孔容,其中以硅酸为硅源合成的多级孔ZSM-5分子筛样品总比表面积、介孔比表面积和介孔孔容增加量分别达到114 m~2/g、152 m~2/g和0.094 cm~3/g;低温老化阶段硅铝酸盐凝胶在四丙基铵根离子的诱导下首先形成大量纳米晶核,晶核接着在高温晶化阶段逐渐生长成纳米微晶,纳米微晶随后继续长大成棒状纳米晶体并自组装团聚成球状多级孔ZSM-5分子筛。
Hierarchical ZSM-5 zeolites with spherical structure were successfully synthesized via a facile two-step hydrothermal process at low temperature aging and high temperature crystallization period,in which the water glass or silicic acid were selected as silicon source and the tetrapropylammonium hydroxide( TPAOH) was used as the single template. The zeolites were characterized with XRD,FT-IR,N2 adsorption-desorption isotherms,SEM and TEM,through which the formation mechanism of the hierarchical ZSM-5 zeolites with spherical structure was investigated. The results indicate that the hierarchical ZSM-5 zeolite consists of regular spherical particles with around 2 μm in diameter and possesses intercrystalline meso-and macropores generated from the aggregation of bar-shape ZSM-5 nanocrystals. Compared with commercial ZSM-5 zeolite,the as-synthesized products with high relative crystallinity have larger BET specific surface area,mesopore surface area and mesopore volume. And the increasing amounts of the above three parameters for hierarchical ZSM-5 zeolites synthesized with silicic acid as silicon source are reached 114 m~2/g,152 m~2/g and 0. 094 cm~3/g,respectively. It is proposed that the aluminosilicate gel forms nano nuclei firstly with the induction effect of TPA+at the low temperature aging stage. Then,the crystal nucleus grew gradually to become nanocrystalline under the high temperature crystallization process. Finally,the aggregated nanocrystalline continues to grow up into bar-shape ZSM-5 nanocrystals and self-assemble into regular spherical structure.
Hierarchical ZSM-5 zeolites with spherical structure were successfully synthesized via a facile two-step hydrothermal process at low temperature aging and high temperature crystallization period,in which the water glass or silicic acid were selected as silicon source and the tetrapropylammonium hydroxide( TPAOH) was used as the single template. The zeolites were characterized with XRD,FT-IR,N2 adsorption-desorption isotherms,SEM and TEM,through which the formation mechanism of the hierarchical ZSM-5 zeolites with spherical structure was investigated. The results indicate that the hierarchical ZSM-5 zeolite consists of regular spherical particles with around 2 μm in diameter and possesses intercrystalline meso-and macropores generated from the aggregation of bar-shape ZSM-5 nanocrystals. Compared with commercial ZSM-5 zeolite,the as-synthesized products with high relative crystallinity have larger BET specific surface area,mesopore surface area and mesopore volume. And the increasing amounts of the above three parameters for hierarchical ZSM-5 zeolites synthesized with silicic acid as silicon source are reached 114 m~2/g,152 m~2/g and 0. 094 cm~3/g,respectively. It is proposed that the aluminosilicate gel forms nano nuclei firstly with the induction effect of TPA+at the low temperature aging stage. Then,the crystal nucleus grew gradually to become nanocrystalline under the high temperature crystallization process. Finally,the aggregated nanocrystalline continues to grow up into bar-shape ZSM-5 nanocrystals and self-assemble into regular spherical structure.
引文
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[18]ZHANG H,WANG G,ZHENG J,et al.Synthesis of hierarchical ZSM-5 composed of nanocrystals without a secondary template[J].Catalysis Letters,2016,45:481-483.
[19]SANHUEZA V,KELM U,CID R,et al.Synthesis of ZSM-5 from diatomite:a case of zeolite synthesis from a natural material[J].Journal of Chemical Technology and Biotechnology,2004,79(7):686-690.
[20]CHENG Y,WANG L J,LI J S,et al.Preparation and characterization of nanosized ZSM-5 zeolites in the absence of organic template[J].Materials Letters,2005,59:3427-3430.
[21]KIRSCHHOCK C E A,RAVISHANKAR R,VERSPEURT F,et al.Identification of precursor species in the formation of MFI zeolite in the TPAOH-TEOS-H2O system[J].The Journal of Physical Chemistry B,1999,103(24):4965-4971.
[22]WANG W,LI G,LI W,et al.Synthesis of hierarchical TS-1 by caramel templating[J].Chemical Communications,2011,47:3529-3531.
[23]HUANG L M,GUO W P,DENG P,et al.Investigation of synthesizing MCM-41/ZSM-5 composites[J].The Journal of Physical Chemistry B,2000,104(13):2813-2817.
[24]SUN H,WANG J,HU J,et al.Rapid synthesis of small crystal Fe ZSM-5 by a two-stage varying-temperature technique[J].Catalysis Letters,2000,69(3/4):245-250.
[2]VOGT E T,WECKHUYSEN B M.Fluid catalytic cracking:recent developments on the grand old lady of zeolite catalysis[J].Chemical Society Reviews,2015,44(20):7342-7370.
[3]MENG X,NAWAZ F,XIAO F S.Templating route for synthesizing mesoporous zeolites with improved catalytic properties[J].Nano Today,2009,4(4):292-301.
[4]PEREZ-RAMIREZ J,CHRISTENSEN C H,EGEBLAD K,et al.Hierarchical zeolites:enhanced utilization of microporous crystals in catalysis by advances in materials design[J].Chemical Society Reviews,2008,37(11):2530-2542.
[5]THIBAULT-STARZYK F,STAN I,ABELLO S,et al.Quantification of enhanced acid site accessibility in hierarchical zeolites-the accessibility index[J].Journal of Catalysis,2009,264(1):11-14.
[6]SHI J,WANG Y,YANG W,et al.Recent advances of pore system construction in zeolite-catalyzed chemical industry processes[J].Chemical Society Reviews,2015,44:8877-8903.
[7]WEI Y,PARMENTIER T E,JONG K P,et al.Tailoring and visualizing the pore architecture of hierarchical zeolites[J].Chemical Society Reviews,2015,44:7234-7261.
[8]SUN M H,HUANG S Z,CHEN L H,et al.Applications of hierarchically structured porous materials from energy storage and conversion,catalysis,photocatalysis,adsorption,separation,and sensing to biomedicine[J].Chemical Society Reviews,2016,45(12):3479-3563.
[9]SCHWIEGER W,MACHOKE A G,WEISSENBERGER T,et al.Hierarchy concepts:classification and preparation strategies for zeolite containing materials with hierarchical porosity[J].Chemical Society Reviews,2016,45:3353-3376.
[10]BAI P,WU P,XING W,et al.Synthesis and catalytic properties of ZSM-5 zeolite with hierarchical pores prepared in the presence of n-hexyltrimethylammonium bromide[J].Journal of Materials Chemistry A,2015,3:18586-18597.
[11]SUN H,PENG P,WANG Y,et al.Preparation,scaleup and application of meso-ZSM-5 zeolite by sequential desilication:dealumination[J].Journal of Porous Materials,2017,24(6):1513-1525.
[12]吕仁庆,罗立文,项寿鹤,等.水热处理的HZSM-5分子筛的孔结构及活性研究[J].石油大学学报(自然科学版),2002,26(3):97-100.LRenqing,LUO Liwen,XIANG Shouhe,et al.Pore texture and cracking activity of HZSM-5 zeolites treated with steam[J].Journal of the University of Petroleum,China(Edition of Natural Science),2002,26(3):97-100.
[13]刘振,马志鹏,孙常庚,等.硬模板法制备微孔-介孔复合SAPO-11分子筛及其长链烷烃异构化反应[J].中国石油大学学报(自然科学版),2014,38(2):153-158.LIU Zhen,MA Zhipeng,SUN Changgeng,et al.Synthesis of meso-microporous SAPO-11by hard template method and its catalytic application for long-chain alkanes hydroisomerization[J].Journal of China University of Petroleum(Edition of Natural Science),2014,38(2):153-158.
[14]于庆君,李春义,山红红,等.纳米棒插接多级孔ZSM-11分子筛形貌影响因素研究[J].中国石油大学学报(自然科学版),2016,40(2):155-161.YU Qingjun,LI Chunyi,SHAN Honghong,et al.Factors affecting the intergrowth morphology of hierarchical ZSM-11 microspheres[J].Journal of China University of Petroleum(Edition of Natural Science),2016,40(2):155-161.
[15]YANG X Y,TIAN G,CHEN L H,et al.Well-organized zeolite nanocrystal aggregates with interconnected hierarchically micro-meso-macropore systems showing enhanced catalytic performance[J].Chemistry-A European Journal,2011,17:14987-14995.
[16]SUN M H,CHEN L H,LI X Y,et al.A comparative study of hierarchically micro-meso-macroporous solidacid catalysts constructed by zeolites nanocrystals synthesized via a quasi-solid-state crystallization process[J].Microporous and Mesoporous Material,2013,182:122-135.
[17]YANG J,YU S,HU H,et al.Synthesis of ZSM-5 hierarchical microsphere-like particle by two stage varying temperature crystallization without secondary template[J].Chemical Engineering Journal,2011,166:1083-1089.
[18]ZHANG H,WANG G,ZHENG J,et al.Synthesis of hierarchical ZSM-5 composed of nanocrystals without a secondary template[J].Catalysis Letters,2016,45:481-483.
[19]SANHUEZA V,KELM U,CID R,et al.Synthesis of ZSM-5 from diatomite:a case of zeolite synthesis from a natural material[J].Journal of Chemical Technology and Biotechnology,2004,79(7):686-690.
[20]CHENG Y,WANG L J,LI J S,et al.Preparation and characterization of nanosized ZSM-5 zeolites in the absence of organic template[J].Materials Letters,2005,59:3427-3430.
[21]KIRSCHHOCK C E A,RAVISHANKAR R,VERSPEURT F,et al.Identification of precursor species in the formation of MFI zeolite in the TPAOH-TEOS-H2O system[J].The Journal of Physical Chemistry B,1999,103(24):4965-4971.
[22]WANG W,LI G,LI W,et al.Synthesis of hierarchical TS-1 by caramel templating[J].Chemical Communications,2011,47:3529-3531.
[23]HUANG L M,GUO W P,DENG P,et al.Investigation of synthesizing MCM-41/ZSM-5 composites[J].The Journal of Physical Chemistry B,2000,104(13):2813-2817.
[24]SUN H,WANG J,HU J,et al.Rapid synthesis of small crystal Fe ZSM-5 by a two-stage varying-temperature technique[J].Catalysis Letters,2000,69(3/4):245-250.