γ-Al_2O_3/SAPO-34复合催化剂及其对MTO反应的催化性能
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摘要
采用介孔γ-Al_2O_3对微孔SAPO-34分子筛进行复合改性,利用水热包覆技术制备了γ-Al_2O_3/SAPO-34复合催化剂,研究了复合催化剂物化性质及其对甲醇制低碳烯烃(MTO)反应的催化性能。采用X射线衍射仪(XRD)、傅里叶红外光谱仪(FT-IR)、扫描电子显微镜(SEM)、氨气程序升温脱附法(NH_3-TPD)和物理吸附仪(BET)等手段对不同γ-Al_2O_3/SAPO-34复合催化剂的晶相组成、骨架结构、微观形貌、表面酸性及孔结构进行分析表征。结果表明,与物理共混催化剂相比,水热包覆法制得γ-Al_2O_3/SAPO-34复合催化剂形成了包覆相和微-介孔结构(微孔比表面积123 m~2/g,介孔比表面积95 m~2/g)。在常压、催化剂装载量1 g、水/醇摩尔比2/1、原料进料体积空速2 h~(-1)、N_2流速20 mL/min、反应温度380℃条件下,复合催化剂表现出优越的催化性能和反应寿命,甲醇转化率和低碳烯烃选择性分别达到100%和88%,催化剂寿命达到990 min,与物理共混催化剂相比,复合催化剂寿命延长了640 min。
Microporous SAPO-34 molecular sieve was promoted by mesoporous γ-Al_2O_3 via hydrothermal coating route to prepare γ-Al_2O_3/SAPO-34 composite catalyst, and the physicochemical properties and catalytic performance in methanol to lower olefin(MTO) of the composite catalysts were investigated. These obtained composite catalysts were extensively characterized by X-ray diffraction(XRD), fourier transform infrared spectroscopy(FT-IR), scanning electron microscope(SEM), NH_3-temperature programmed desorption(NH_3-TPD) and Brunner Emmet Teller(BET) techniques, to investigate their crystalline phase, skeletal structure, morphology, surface acidity and pore structure, respectively. Compared with the physically blending catalyst, the uniformly continuous coating phase and micro-mesoporous structure(microporous specific surface area of 123 m~2/g, mesoporous specific surface area of 95 m~2/g) were successfully obtained in the composite catalyst. The composite catalyst exhibits superior catalytic performances and reaction life-time, with methanol conversion of 100%, light olefins selectivity of 88%, and catalytic lifetime of 990 min under the conditions of atmospheric pressure, reaction temperature of 380 ℃, catalyst loading of 1 g, hydro/alcohol molar ratio of 2/1, nitrogen flow rate of 20 mL/min and feed speed of 2 h~(-1). Compared with the physically blending catalyst, the catalytic lifetime of the composite catalyst is extended by 640 min.
Microporous SAPO-34 molecular sieve was promoted by mesoporous γ-Al_2O_3 via hydrothermal coating route to prepare γ-Al_2O_3/SAPO-34 composite catalyst, and the physicochemical properties and catalytic performance in methanol to lower olefin(MTO) of the composite catalysts were investigated. These obtained composite catalysts were extensively characterized by X-ray diffraction(XRD), fourier transform infrared spectroscopy(FT-IR), scanning electron microscope(SEM), NH_3-temperature programmed desorption(NH_3-TPD) and Brunner Emmet Teller(BET) techniques, to investigate their crystalline phase, skeletal structure, morphology, surface acidity and pore structure, respectively. Compared with the physically blending catalyst, the uniformly continuous coating phase and micro-mesoporous structure(microporous specific surface area of 123 m~2/g, mesoporous specific surface area of 95 m~2/g) were successfully obtained in the composite catalyst. The composite catalyst exhibits superior catalytic performances and reaction life-time, with methanol conversion of 100%, light olefins selectivity of 88%, and catalytic lifetime of 990 min under the conditions of atmospheric pressure, reaction temperature of 380 ℃, catalyst loading of 1 g, hydro/alcohol molar ratio of 2/1, nitrogen flow rate of 20 mL/min and feed speed of 2 h~(-1). Compared with the physically blending catalyst, the catalytic lifetime of the composite catalyst is extended by 640 min.
引文
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[28]ALAMOLHODA S,KAZEMEINI M,ZAHERIAN A,et al.Reaction kinetics determination and neural networks modeling of methanol dehydration over nanoγ-Al2O3 catalyst[J].Journal of Industrial and Engineering Chemistry,2012,18(6):2059-2068.
[29]WEI L D,CAO Y,JING F D,et al.The role of iodide promoter in selective oxidation of methanol to formaldehyde[J].Catalysis Letters,1999,63(1/2):49-57.
[30]WU H J,HSU H K,CHIANG C M.Surface reactions of CH3I and CF3I with coadsorbed CH2I2on Ag(Ⅲ)as mechanistic probes for carbon-carbon bond formation via methylene insertion[J].Journal of the American Chemical Society,1999,121(18):4433-4442.
[31]DUAN C,ZHANG X,ZHOU R,et al.Comparative studies of ethanol to propylene over HZSM-5/SAPO-34catalysts prepared by hydrothermal synthesis and physical mixture[J].Fuel Processing Technology,2013,108:31-40.
[32]RAZAVIAN M,FATEMI S.Synthesis and application of ZSM-5/SAPO-34 and SAPO-34/ZSM-5 composite systems for propylene yield enhancement in propane dehydrogenation process[J].Microporous&Mesoporous Materials,2015,201:176-189.
[33]薛建伟,吴岚,吕志平,等.F-ZSM-5沸石的合成及对偏三甲苯-甲醇烷基化制均四甲苯的催化性能研究[J].燃料化学学报,2000,28(1):16-19.(XUE Jianwei,WU Lan,LZhiping,et al.Synthesis of F-ZSM-5and performance for 1,2,4-TrMB alkylation with methanol to 1,2,4,5-TeMB[J].Journal of Fuel Chemistry and Technology,2000,28(1):16-19.)
[2]TIAN P,WEI Y,YE M,et al.Methanol to olefins(MTO):From fundamentals to commercialization[J].ACS Catalysis,2015,5(3):1922-1938.
[3]HAW J F,SONG W G,MARCUS D M,et al.The mechanism of methanol to hydrocarbon catalysis[J].Accounts of Chemical Research,2003,36(5):317-326.
[4]KAREN H,JEROEN V D M,KRISTOF D W,et al.Unraveling the reaction mechanisms governing methanolto-olefins catalysis by theory and experiment[J].ChemPhysChem,2013,14(8):1526-1545.
[5]HIROTA Y,MURATA K,MIYAMOTO M,et al.Light olefins synthesis from methanol and dimethylether over SAPO-34 nanocrystals[J].Catalysis Letters,2010,140(1/2):22-26.
[6]何长青,刘中民,蔡光宇,等.双模板法控制SAPO-34分子筛的晶粒尺寸[J].分子催化,1994,8(3):207-212.(HE Changqing,LIU Zhongmin,CAI Guangyu,et al.Adjusting the crystallite size of SAPO-34molecular sieve by the dual template method[J].Journal of Molecular Catalysis(China),1994,8(3):207-212.)
[7]HU H,CAO F,YING W,et al.Study of coke behavior of catalyst during methanol-to-olefins process based on a special TGA reactor[J].Chemical Engineering Journal,2010,160(2):770-778.
[8]NISHIYAMA N,KAWAGUCHI M,HIROTA Y,et al.Size control of SAPO-34crystals and their catalyst life in the methanol-to-olefin reaction[J].Applied Catalysis A General,2009,362(1):193-199.
[9]YING L,YE M,CHENG Y W,et al.Characteristics of coke deposition over a SAPO-34 catalyst in the methanol-to-olefins reaction[J].Petroleum Science&Technology,2015,33(9):984-991.
[10]YUAN C,WEI Y X,LI J Z,et al.Temperatureprogrammed methanol conversion and coke deposition on fluidized-bed catalyst of SAPO-34[J].Chinese Journal of Catalysis,2012,33(2):367-374.
[11]梁光华,狄春雨,王龙,等.不同铝源合成SAPO-34分子筛及其MTO催化性能[J].石油学报(石油加工),2014,30(5):885-890.(LIANG Guanghua,DIChunyu,WANG Long,et al.Effect of aluminum sources on the synthesis of SAPO-34and its catalytic properties for MTO reaction[J].Acta Petrolei Sinica(Petroleum Processing Section),2014,30(5):885-890.)
[12]王龙,李晓峰,王平,等.片层SAPO-34分子筛的合成、表征及其在甲醇制烯烃(MTO)中的催化性能[J].石油学报(石油加工),2016,32(2):355-361.(WANGLong,LI Xiaofeng,WANG Ping,et al.Synthesis and characterization of SAPO-34 molecular sieve with lamellar morphology and its catalytic[J].Acta Petrolei Sinica(Petroleum Processing Section),2016,32(2):355-361.)
[13]WANG C,YANG M,TIAN P,et al.Dual templatedirected synthesis of SAPO-34 nanosheet assemblies with improved stability in the methanol to olefins reaction[J].Journal of Materials Chemistry A,2015,3(10):5608-5616.
[14]SERRANO D P,ESCOLA J M,PIZARRO P.Synthesis strategies in the search for hierarchical zeolites[J].Chemical Society Reviews,2013,42(9):4004-4035.
[15]WANG F,SUN L,CHEN C,et al.Polyethyleneimine templated synthesis of hierarchical SAPO-34 zeolites with uniform mesopores[J].RSC Advances,2014,4(86):46093-46096.
[16]ZHIBIN L,JOAQUIN M T,PATRICIA C,et al.Methanol to olefins:Activity and stability of nanosized SAPO-34molecular sieves and control of selectivity by silicon distribution[J].Physical Chemistry Chemical Physics,2013,15(35):14670-14680.
[17]ASKARI S,SEDIGHI Z,HALLADJ R.Rapid synthesis of SAPO-34nano-catalyst by dry gel conversion method templated with morphline:Investigating the effects of experimental parameters[J].Microporous&Mesoporous Materials,2014,197(10):229-236.
[18]AGHAEI E,HAGHIGHI M.Effect of crystallization time on properties and catalytic performance of nanostructured SAPO-34 molecular sieve synthesized at high temperatures for conversion of methanol to light olefins[J].Powder Technology,2015,269:358-370.
[19]HEYDEN H V,MINTOVA S,BEIN T.Nanosized SAPO-34 synthesized from colloidal solutions[J].Chemistry of Materials,2008,20(9):2956-2963.
[20]MIAO Y,PENG T,CHAN W,et al.A top-down approach to prepare silicoaluminophosphate molecular sieve nanocrystals with improved catalytic activity[J].Chemical Communications,2014,50(15):1845-1847.
[21]HAJIASHRAFI T,KHARAT A N,DAUTH A,et al.Preparation and characterization of lanthanide modified SAPO-34 nano catalysts and measurement of their activity for methanol to olefin conversion[J].Reaction Kinetics Mechanisms&Catalysis,2014,113(2):585-603.
[22]OBRZUT D L,ADEKKANATTU P M,THUNDIMADATHIL J,et al.Reducing methane formation in methanol to olefins reaction on metal impregnated SAPO-34molecular sieve[J].Reaction Kinetics&Catalysis Letters,2003,80(1):113-121.
[23]WANG K,CAO G,KENNEDY G J,et al.Pore modification of H-SAPO-34 using dialkyl zinc:Structural characterization and reaction pathway[J].Journal of Physical Chemistry C,2011,115(38):18611-18617.
[24]NIE R F,LEI H,PAN S Y,et al.Core-shell structured CuO-ZnO@H-ZSM-5 catalysts for COhydrogenation to dimethyl ether[J].Fuel,2011,90(7):419-425.
[25]LEE S G,KIM H S,KIM Y H,et al.Dimethyl ether conversion to light olefins over the SAPO-34/ZrO2composite catalysts with high lifetime[J].Journal of Industrial and Engineering Chemistry,2014,20(1):61-67.
[26]李婷,曹建新,刘飞.碘甲烷热裂解制低碳烯烃体系热力学分析[J].石油学报(石油加工),2015,31(3):712-719.(LI Ting,CAO Jianxin,LIU Fei.Thermodynamic analysis of methyl iodide pyrolysis to light olefins[J].Acta Petrolei Sinica(Petroleum Processing Section),2015,31(3):712-719.)
[27]KHALEEL A,SHEHADI I,AL-MARZOUQI A.Catalytic conversion of chloromethane to methanol and dimethyl ether over mesoporousγ-alumina[J].Fuel Processing Technology,2011,92(9):1783-1789.
[28]ALAMOLHODA S,KAZEMEINI M,ZAHERIAN A,et al.Reaction kinetics determination and neural networks modeling of methanol dehydration over nanoγ-Al2O3 catalyst[J].Journal of Industrial and Engineering Chemistry,2012,18(6):2059-2068.
[29]WEI L D,CAO Y,JING F D,et al.The role of iodide promoter in selective oxidation of methanol to formaldehyde[J].Catalysis Letters,1999,63(1/2):49-57.
[30]WU H J,HSU H K,CHIANG C M.Surface reactions of CH3I and CF3I with coadsorbed CH2I2on Ag(Ⅲ)as mechanistic probes for carbon-carbon bond formation via methylene insertion[J].Journal of the American Chemical Society,1999,121(18):4433-4442.
[31]DUAN C,ZHANG X,ZHOU R,et al.Comparative studies of ethanol to propylene over HZSM-5/SAPO-34catalysts prepared by hydrothermal synthesis and physical mixture[J].Fuel Processing Technology,2013,108:31-40.
[32]RAZAVIAN M,FATEMI S.Synthesis and application of ZSM-5/SAPO-34 and SAPO-34/ZSM-5 composite systems for propylene yield enhancement in propane dehydrogenation process[J].Microporous&Mesoporous Materials,2015,201:176-189.
[33]薛建伟,吴岚,吕志平,等.F-ZSM-5沸石的合成及对偏三甲苯-甲醇烷基化制均四甲苯的催化性能研究[J].燃料化学学报,2000,28(1):16-19.(XUE Jianwei,WU Lan,LZhiping,et al.Synthesis of F-ZSM-5and performance for 1,2,4-TrMB alkylation with methanol to 1,2,4,5-TeMB[J].Journal of Fuel Chemistry and Technology,2000,28(1):16-19.)