ZSM-12分子筛合成、表征与正癸烷加氢异构化反应催化性能
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摘要
以甲基三乙基溴化铵为模板剂,硅溶胶为硅源,Al_2(SO_4)_3·18H_2O为铝源制备了2种不同n(Si)/n(Al)的ZSM-12分子筛。采用XRD、XRF、氮气吸附-脱附、吡啶吸附红外光谱、SEM和TEM等表征了合成的分子筛样品。以正癸烷为模型化合物对合成的ZSM-12制备的Pt催化剂进行加氢异构化反应评价。结果表明,合成分子筛为纯相ZSM-12晶体,合成过程中物料反应完全,且铝原子完全处于分子筛骨架中,分子筛Br9nsted酸中心数量和强度随n(Si)/n(Al)变化而改变。以高n(Si)/n(Al)合成的ZSM-12分子筛为载体制备的Pt催化剂具有较高的异构选择性,且产物中含有较多的多支链异构体。将催化剂催化性能与分子筛物化性质关联得出,ZSM-12分子筛孔径较大,为了提高异构选择性和多支链异构体产率,需要更少和更弱的Br9nsted酸性中心。
ZSM-12 zeolites with different n(Si)/n(Al)were synthesized by using triethylmethylammonium bromide as template,silica gel as silicon source and Al2(SO4)3·18H2O as alumina source,respectively.The synthesized zeolite samples were detailed characterized by XRD,XRF,N2adsorption-desorption,pyridine adsorption FT-IR,SEM and TEM. The tests for paraffin hydroisomerization over the prepared catalysts were carried out with decane as the model molecule.The results revealed that the ZSM-12 zeolite samples were of pure crystals,and all silicon source and alumina source were used out during the synthesis.Moreover,all alumina atoms in the obtained zeolite samples were in the framework and the amount and strength of Br9 nsted acid sites were varied with the n(Si)/n(Al)in sample.The hydroisomerization selectivity over the Pt catalyst contained the ZSM-12 with high n(Si)/n(Al)value was higher,especially,the content of multibranched isomers in the product was higher,which can be attributed to the big pore diameter,weak and less Br9 nsted acid sites,based on the chemical and physical properties of the ZSM-12 zeolite.
ZSM-12 zeolites with different n(Si)/n(Al)were synthesized by using triethylmethylammonium bromide as template,silica gel as silicon source and Al2(SO4)3·18H2O as alumina source,respectively.The synthesized zeolite samples were detailed characterized by XRD,XRF,N2adsorption-desorption,pyridine adsorption FT-IR,SEM and TEM. The tests for paraffin hydroisomerization over the prepared catalysts were carried out with decane as the model molecule.The results revealed that the ZSM-12 zeolite samples were of pure crystals,and all silicon source and alumina source were used out during the synthesis.Moreover,all alumina atoms in the obtained zeolite samples were in the framework and the amount and strength of Br9 nsted acid sites were varied with the n(Si)/n(Al)in sample.The hydroisomerization selectivity over the Pt catalyst contained the ZSM-12 with high n(Si)/n(Al)value was higher,especially,the content of multibranched isomers in the product was higher,which can be attributed to the big pore diameter,weak and less Br9 nsted acid sites,based on the chemical and physical properties of the ZSM-12 zeolite.
引文
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[22]刘维桥,尚通明,周全法,等.金属助剂对Pt/SAPo-11催化剂物化及异构性能的影响[J].燃料化学学报,2010,38(2):212-217.(LIU Weiqiao,SHANGTongming,ZHOU Quanfa,et al.Study on the physicochemical and isomerization property of Pt/SAPO-11catalysts promoted by metallic additive[J].Journal of Fuel Chemistry and Technology,2010,38(2):212-217.)
[2]MITRAA,KIRBY C W,WANG Z B,et al.Synthesis of pure-silica MTW powder and supported films[J].Microporous and Mesoporous Materials,2002,54(1-2):175-186.
[3]吴伟,李凌飞,武光,等.具有介孔结构的ZSM-12分子筛的制备、表征及催化性能[J].催化学报,2009,30(6):531-536.(WU Wei,LI Lingfei,WU Guang,et al.Preparation,characterization,and catalytic performance of mesoporous ZSM-12 zeolite[J].Chinese Journal of Catalysis,2009,30(6):531-536.)
[4]CHEN C Y,X OUYANG,ZONES S I,et al.Characterization of shape selective properties of zeolites via hydroisomerization of n-hexane[J].Microporous and Mesoporous Materials,2012,164(1):71-81.
[5]姚国欣.21世纪润滑油基础油生产技术和市场前景[J].石油商技,2001,19(2):1-5.(YAO Guoxin,Production techanology&market prospect for lube base oil in 21st century[J].Petroleum Products Application Research,2001,19(2):1-5.)
[6]钱伯章.润滑油基础油生产技术进展[J].润滑油与燃料,2013,23(3):1-9.(QIAN Bozhang.Development of production technology for lube base oil[J].Lubes&Fuels,2013,23(3):1-9.)
[7]ROMERO M D,DE LUCAS A,CALLES J A,et al.Bifunctional catalyst NiHZSM-5:Effects of the nickel incorporation method[J].Appllied Catalysis A-General,1996,146(2):425-441.
[8]SASTRE G,CHICA A,CORMA A.On the mechanism of alkane isomerisation(isodewaxing)with unidirectional 10-member ring zeolites:A molecular dynamics and catalytic study[J].Journal of Catalysis,2000,195(2):227-236.
[9]MARTENS J A,VANBUTSELEA G,JACOBS P A,et al.Evidences for pore mouth and key-lock catalysis in hydroisomerization of long n-alkanes over 10-ring tubular pore bifunctional zeolites[J].Catalysis Today,2001,65(2-4):111-116.
[10]MARTENS J A,SOUVERIJNS W,VERRELST W,et al.Selective isomerization of hydrocarbon chains on external surfaces of zeolite crystals[J].Angew Chemical International Edition English,1995,34(22):2528-2530.
[11]PARTON R,UYTTERHOEVEN L,MARTENS J A,et al.Synergism of ZSM-22 and Y zeolites in the bifunctional conversion of n-alkanes[J].Applied Catalysis,1991,76(1):131-142.
[12]EMEIS C A.Determination of integrated molar extinction coefficients for infrared absorption bands of pyridine adsorbed on solid acid catalysts[J].Journal of Catalysis,1993,141(2):347-354.
[13]DENAYER J F,BARON G V,VANBUTSELE G,et al.Modeling of adsorption and bifunctional conversion of n-alkanes on Pt/H-ZSM-22 zeolite catalyst[J].Chemical Engineering Science,1999,54(15):3553-3561.
[14]SOUVERJINS W,MARTENS J A,UYTTERHOEVEN L,et al.Selective key-lock catalysis in dimethylbranching of alkanes on Ton type zeolites[J].Study in Surface Science and Catalysis,1997,105(97):1285-1292.
[15]OKI M,ADEDIGBA A,TERUOKI T,et al.Microwave-assisted hydrothermal synthesis of submicron ZSM-22zeolites and their applications in light olefin production[J].Microporous and Mesoporous Materials,2015,206(1):136-143.
[16]KUMAR N,LINDFORS L E,BYGGNINGSBACKA R,et al.Synthesis and characterization of H-ZSM-22,ZnZSM-22and Ga-H-ZSM-22zeolite catalysts and their catalytic activity in the aromatization of n-butane[J].Appllied Catalysis A-General,1996,139(1-2):189-199.
[17]ALVAREZ F,RIBEIRO F R,PEROT G,et al.Hydroisomerization and hydrocracking of alkanes 7:Influence of the balance between acid and hydrogenating functions on the transformation of n-decane on PtHYcatalysts[J].Journal of Catalysis,1996,162(2):179-189.
[18]ZHANG W M,PANAGIOTIS G S.Effect of zeolite structure and acidity on the product selectivity and reaction mechanism for n-octane hydroisomerization and hydrocracking[J].Journal of Catalysis,1999,182(2):400-416.
[19]BATALHA N,PINARD L,BOUCHY C,et al.n-Hexadecane hydroisomerization over Pt-HBEAcatalysts:Quantification and effect of the intimacy between metal and protonic sites[J].Journal of Catalysis,2013,307:122-131.
[20]BI Y F,XIA G F,HUANG W G,et al.Hydroisomerization of long chain n-paraffins:The role of the acidity of the zeolite[J].RSC Advances,2015,120(5):99201-99206.
[21]FRANK B,KARSTEN F,MARKO B,et al.Hydroisomerization of long-chain paraffins over nanosized bimetallic Pt-Pd/H-beta catalysts[J].Catalysis Science&Technology,2014,11(4):4045-4054.
[22]刘维桥,尚通明,周全法,等.金属助剂对Pt/SAPo-11催化剂物化及异构性能的影响[J].燃料化学学报,2010,38(2):212-217.(LIU Weiqiao,SHANGTongming,ZHOU Quanfa,et al.Study on the physicochemical and isomerization property of Pt/SAPO-11catalysts promoted by metallic additive[J].Journal of Fuel Chemistry and Technology,2010,38(2):212-217.)