CH_3COONa处理HZSM-5分子筛及其催化性能
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摘要
采用不同浓度的CH_3COONa溶液和常规碱(NaOH和Na_2CO_3)溶液处理HZSM-5分子筛,对处理前后的HZSM-5分子筛负载Pt,制备Pt/HZSM-5催化剂用于丙烷脱氢反应。利用X射线衍射(XRD)、X射线荧光光谱(XRF)、扫描电镜(SEM)、比表面测试仪(BET)、NH_3-TPD(程序升温脱附法)和H2化学吸附等手段对处理前后的HZSM-5分子筛进行表征,并考察了不同浓度的CH_3COONa溶液和常规碱溶液处理对HZSM-5分子筛的晶体结构、表面形貌、孔结构、表面酸性及丙烷脱氢性能的影响。结果表明,CH_3COONa溶液具有碱改性作用,与常规碱溶液相比,采用CH_3COONa溶液处理HZSM-5分子筛,能够在对分子筛的晶体结构和表面形貌影响较小的基础上有效地引入介孔结构,具有较好的可调控性;随着CH_3COONa溶液浓度的增加,丙烷脱氢反应的丙烷初始转化率和丙烯选择性先升高后降低,当CH_3COONa溶液浓度为4.0 mol/L时,丙烷初始转化率和丙烯选择性均达到最高值,分别为34.5%和98.9%。
HZSM-5 zeolites were treated by CH_3COONa solution with different concentrations and conventional alkali(NaOH or Na_2CO_3) solution. Then, Pt was loaded on HZSM-5 zeolites before and after the treatment to synthesize Pt/HZSM-5 catalysts for propane dehydrogenation reaction. HZSM-5 zeolites were characterized by XRD, XRF, SEM,BET, NH_3-TPD, and H_2 chemisorption. The effect of CH_3 COONa solution with different concentrations and conventional alkali solution on crystal structure, surface morphology, pore structure, surface acidity, and propane dehydrogenation performance of HZSM-5 zeolites were investigated. The results showed that CH_3 COONa solution modified HZSM-5 zeolites by alkali. Compared with conventional alkali solution, the treatment of CH_3 COONa solution for HZSM-5 zeolites could more effectively and better controllably introduce the mesoporous structure with less influence on the crystal structure and surface morphology. With increase of the concentration of CH_3 COONa solution, the initial propane conversion and the propene selectivity in propane dehydrogenation firstly increased and then decreased. The catalyst treated by 4.0 mol/L CH_3 COONa solution exhibited the highest propane initial conversion and propene selectivity, which were 34.5% and 98.9%, respectively.
HZSM-5 zeolites were treated by CH_3COONa solution with different concentrations and conventional alkali(NaOH or Na_2CO_3) solution. Then, Pt was loaded on HZSM-5 zeolites before and after the treatment to synthesize Pt/HZSM-5 catalysts for propane dehydrogenation reaction. HZSM-5 zeolites were characterized by XRD, XRF, SEM,BET, NH_3-TPD, and H_2 chemisorption. The effect of CH_3 COONa solution with different concentrations and conventional alkali solution on crystal structure, surface morphology, pore structure, surface acidity, and propane dehydrogenation performance of HZSM-5 zeolites were investigated. The results showed that CH_3 COONa solution modified HZSM-5 zeolites by alkali. Compared with conventional alkali solution, the treatment of CH_3 COONa solution for HZSM-5 zeolites could more effectively and better controllably introduce the mesoporous structure with less influence on the crystal structure and surface morphology. With increase of the concentration of CH_3 COONa solution, the initial propane conversion and the propene selectivity in propane dehydrogenation firstly increased and then decreased. The catalyst treated by 4.0 mol/L CH_3 COONa solution exhibited the highest propane initial conversion and propene selectivity, which were 34.5% and 98.9%, respectively.
引文
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[4]QIU AN-DING,LI EN-XIA,FAN YI-NING.Effect on catalytic performance of PtSn/ZSM-5 catalyst for propane dehydrogenation.Chinese Journal of Catalysis,2007,28(11):970-974.
[5]LI JIAN-HUA,YANG DONG-HUA,LüAI-NING,et al.Synthesis and characterization of ZSM-5/EU-1 composite zeolite with core-shell structure by one step.Journal of Inorganic Materials,2016,31(5):492-498.
[6]ZHANG YI-WEI,ZHOU YU-MING,TANG MENG-HAN,et al.Effect of La calcination temperature on catalytic performance of PtSnNaLa/ZSM-5 catalyst for propane dehydrogenation.Chemical Engineering Journal,2012,181-182:530-537.
[7]SHEINTUCH M,LIRON O,RICCA A,et al.Propane dehydrogenation kinetics on supported Pt catalyst.Applied Catalysis A:General,2016,516:17-29.
[8]MASARU OGURA,SHIN-YA SHINOMIYA,JUNKO TATENO,et al.Alkali-treatment technique-new method for modification of structural and acid-catalytic properties of ZSM-5 zeolites.Applied Catalysis A:General,2001,219:33-43.
[9]FATHI S,SOHRABI M,FALAMAKI C.Improvement of HZSM-5 performance by alkaline treatments:comparative catalytic study in the MTG reactions.Fuel,2014,116:529-537.
[10]SHI GANG,LIN XIU-YING,FAN YU,et al.Desilication modification of ZSM-5 zeolite and its catalytic properties in hydro-upgrading.Journal of Fuel Chemistry and Technology,2013,41(5):589-560.
[11]LIU DONG-MEI,ZHAI YU-CHUN,MA JIAN,et al.Preparation of micro-mesoporous ZSM-5 modified by Na2CO3 and its catalytic performance for sulfur etherification.Acta Petrolei Sinica(Petroleum Processing Section),2015,31(1):38-44.
[12]GAO XIONG-HOU,TANG ZHI-CHENG,LU GONG-XUAN,et al.Butene catalytic cracking to ethylene and propylene on mesoporous ZSM-5 by desilication.Solid State Sciences,2010,12:1278-1282.
[13]OGURA M,SHINOMIYA S.Alkali-treatment technique-new method for modification of structural and acid-catalytic properties of ZSM-5 zeolites.Applied Catalysis A:General,2001,219(3):33-43.
[14]HAO CHEN,HAO CHENG,FANG ZHOU,et al.Catalytic fast pyrolysis of rice straw to aromatic compounds over hierarchical HZSM-5 produced by alkali treatment and metal-modification.Journal of Analytical and Applied Pyrolysis,2018,131:76-84.
[15]ZHANG YI-WEI,ZHOU YU-MING,QIU AN-DING,et al.Effect of Na addition on catalytic performance of PtSn/ZSM-5 catalyst for propane dehydrogenation.Acta Phys.-Chim.Sin.,2006,22(6):672-678.
[16]SUZUKI TETSUO,OKUHARA TOSHIO.Change in pore structure of MFI zeolite by treatment with NaOH aqueous solution.Microporous and Mesoporous Materials,2001,43(1):83-89.
[17]SONG YUE-QIN,FENG YAN-LONG,LIU FENG,et al.Effect of variations in pore structure and acidity of alkali treated ZSM-5 on the isomerization performance.Journal of Molecular Catalysis A:Chemical,2009,310(1/2):130-137.