改进的无溶剂法制备FeAPO-11分子筛及其催化性能
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摘要
在文献中所报道AEL型分子筛无溶剂合成法的基础上,引入低温预处理、机械化学预处理、晶种和双氧水等合成变量进行具有特定形貌或孔结构的高结晶度的FeAPO-11分子筛的合成,并将制备的分子筛作为催化剂应用于苯酚的羟基化反应中。采用XRD、SEM、氮气物理吸脱附以及紫外可见漫反射光谱(UV-Vis DRS)等手段对FeAPO-11分子筛进行表征,深入探讨了催化剂上铁元素含量、铁物种分布和比表面积等因素对苯酚羟基化反应的影响。结果表明,低温预处理和双氧水的引入能显著提高FeAPO-11分子筛的结晶度,在特定条件下能制备出具有规则纳米晶聚集体形貌的FeAPO-11分子筛。催化结果表明,苯酚羟基化反应的诱导期长短主要取决于FeAPO-11催化剂中非骨架铁形式的多核铁的含量。在被考察的5个催化剂中,FeAPO-11-LHSB由于具有规则的纳米晶聚集体形貌、高的外表面积及骨架铁含量,在苯酚羟基化反应中展示出最优的性能,其苯二酚的产率和选择性分别为33.6%和67.6%。
Based on the solvent-free synthesis method of AEL-type molecular sieves in the literature,FeAPO-11 molecular sieves with high crystallinity,specific morphology or pore structure were synthesized by introducing some additional synthetic variables,including low temperature pretreatment,mechanochemical pretreatment,seed crystals and hydrogen peroxide.Their catalytic performance was investigated using phenol hydroxylation as a probe reaction.The synthesized FeAPO-11 molecular sieves were further characterized by XRD,SEM,N_2 physisorption and UV-Vis DRS.Moreover,the effects of content and distribution of Fe species,and surface area of the catalysts on the phenol hydroxylation reaction were thoroughly studied.Characterization results indicate that combination of low temperature pretreatment and hydrogen peroxide can significantly improve the crystallinity of FeAPO-11 zeolite.Especially,under some specific conditions,FeAPO-11 molecular sieve with uniform nanocrystalline aggregates morphology can be successfully prepared.The catalytic reaction results suggest that the induction period of phenol hydroxylation reaction is mainly determined by the amount of multi-nuclear iron in the form of non-framework iron species in FeAPO-11 catalysts. Among the five selected catalysts,due to its regular nanocrystalline aggregates morphology,high external surface area and high iron content in the framework,FeAPO-11-LHSB exhibites the best performance with 33.6% dihydroxybenzene yield and 67.6% selectivity.
Based on the solvent-free synthesis method of AEL-type molecular sieves in the literature,FeAPO-11 molecular sieves with high crystallinity,specific morphology or pore structure were synthesized by introducing some additional synthetic variables,including low temperature pretreatment,mechanochemical pretreatment,seed crystals and hydrogen peroxide.Their catalytic performance was investigated using phenol hydroxylation as a probe reaction.The synthesized FeAPO-11 molecular sieves were further characterized by XRD,SEM,N_2 physisorption and UV-Vis DRS.Moreover,the effects of content and distribution of Fe species,and surface area of the catalysts on the phenol hydroxylation reaction were thoroughly studied.Characterization results indicate that combination of low temperature pretreatment and hydrogen peroxide can significantly improve the crystallinity of FeAPO-11 zeolite.Especially,under some specific conditions,FeAPO-11 molecular sieve with uniform nanocrystalline aggregates morphology can be successfully prepared.The catalytic reaction results suggest that the induction period of phenol hydroxylation reaction is mainly determined by the amount of multi-nuclear iron in the form of non-framework iron species in FeAPO-11 catalysts. Among the five selected catalysts,due to its regular nanocrystalline aggregates morphology,high external surface area and high iron content in the framework,FeAPO-11-LHSB exhibites the best performance with 33.6% dihydroxybenzene yield and 67.6% selectivity.
引文
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[25]XIN H,LIU J,FAN F,et al.Mesoporous ferrosilicates with high content of isolated iron species synthesized in mild buffer solution and their catalytic application[J].Microporous&Mesoporous Materials,2008,113(1):231-239.
[26]LI B,XU J,LIU J,et al.Preparation of mesoporous ferrisilicate:Incorporation of iron onto mesoporous silica network by a novel route[J].Materials Letters,2012,78(7):147-149.
[27]ZHAO X,ZHANG X,HAO Z,et al.Synthesis of FeAPO-5 molecular sieves with high iron contents via improved ionothermal method and their catalytic performances in phenol hydroxylation[J].Journal of Porous Materials,2018,25(2):1007-1016.
[28]YANG R,LI G,HU C.The preparation of Fe/woodbased activated carbon catalyst for phenol hydroxylation from Fe2+and Fe3+precursors[J].Catalysis Science&Technology,2015,5(4):2486-2495.
[29]KAMEGAWA T,ANDO T,ISHIGURO Y.Hydroxylation of phenol on iron-containing mesoporous silica with hierarchical macroporous architecture[J].Bulletin of the Chemical Society of Japan,2015,88(4):572-574.
[30]DAI P,PETTY R,INGRAM C.et al.Metal substituted aluminophosphate molecular sieves as phenol hydroxylation catalysts[J].Applied Catalysis A:General,1996,143:101-110.
[2]KIM J,BHATTACHARJEE S,JEONG K E,et al.CrAPO-5catalysts having a hierarchical pore structure for the selective oxidation of tetralin to 1-tetralone[J].New Journal of Chemistry,2010,34(12):2971-2978.
[3]ZHAO X,KANG C,WANG H,et al.Ionothermal synthesis of FeAlPO-16 molecular sieve by microwave irradiation in eutectic mixture[J].Journal of Porous Materials,2011,18(5):615-621.
[4]PEETERS M P J,HAAN J W D,VEN L J M V D,et al.Hydration of AlPO4-11 studied with X-ray powder diffraction and aluminum-27and phosphorus-31 NMR[J].Journal of Physical Chemistry,1993,(20):5363-5369.
[5]SINHA A K,KUMAR S,SIVASANKER S.Transformation of n-hexane over microporous molecular sieves:Studies over MeAPO-11and MeAPSO-11[J].Reaction Kinetics&Catalysis Letters,1999,68(2):307-312.
[6]SINGHA P S,KOSUGEB K,RAMASWAMYC V,et al.Characterization of MeAPO-11s synthesized conventionally and in the presence of fluoride ions and their catalytic properties in the oxidation of ethylbenzene[J].Applied Catalysis A:General,1999,177(2):149-159.
[7]QI X,ZHANG L,XIE W,et al.Synthesis of coppersubstituted aluminophosphate molecular sieves(CuAPO-11)and their catalytic behavior for phenol hydroxylation[J].Applied Catalysis A:General,2004,276(1):89-94.
[8]REN L,WU Q,YANG C,et al.Solvent-free synthesis of zeolites from solid raw materials[J].Journal of the American Chemical Society,2012,134(37):15173-15176.
[9]MAJANO G,BORCHARDT L,MITCHELL S,et al.Rediscovering zeolite mechanochemistry-A pathway beyond current synthesis and modification boundaries[J].Microporous&Mesoporous Materials,2014,194(8):106-114.
[10]VALTCHEV V,MINTOVA S,DIMOV V,et al.Tribochemical activation of seeds for rapid crystallization of zeolite Y[J].Zeolites,1995,15(3):193-197.
[11]IYOKI K,ITABASHI K,OKUBO T.Progress in seedassisted synthesis of zeolites without using organic structure-directing agents[J].Microporous&Mesoporous Materials,2014,189:22-30.
[12]CUNDY C S,COX P A.The hydrothermal synthesis of zeolites:History and development from the earliest days to the present time[J].Chemical Reviews,2003,103(3):663-702.
[13]KASAHARA S,ITABASHI K,IGAWA K.Clear aqueous nuclei solution for faujasite synthesis[J].Studies in Surface Science&Catalysis,1986,28:185-192.
[14]CEJKA J,BEKKUM H,CORMA A,et al.Introduction to Zeolite Science and Practice[M].3rd Revised Edition.Amsterdam:Elsevier,2007:57-60.
[15]FENG G,CHENG P,YAN W,et al.Accelerated crystallization of zeolites via hydroxyl free radicals[J].Science,2016,351(6278):1188-1191.
[16]CHOI J S,YOON S S,JANG S H,et al.Phenol hydroxylation using Fe-MCM-41catalysts[J].Catalysis Today,2006,111(3):280-287.
[17]WU C,KONG Y,GAO F,et al.Synthesis,characterization and catalytic performance for phenol hydroxylation of Fe-MCM41with high iron content[J].Microporous&Mesoporous Materials,2008,113(1-3):163-170.
[18]LIU H,LU G,GUO Y,et al.Study on the synthesis and the catalytic properties of Fe-HMS materials in the hydroxylation of phenol[J].Microporous&Mesoporous Materials,2008,108(1):56-64.
[19]HAN B,SHI X,ZHANG Y,et al.Influences of pore sizes on the catalytic activity of Fe-MCM-41 in hydroxylation of phenol[J].Asian Journal of Chemistry,2013,25(16):9087-9091.
[20]FAN W,LI R,DOU T,et al.Solvent effects in the synthesis of CoAPO-5,-11and-34molecular sieves[J].Microporous&Mesoporous Materials,2005,84(1-3):116-126.
[21]徐如人,庞文琴,于吉红,等.分子筛与多孔材料化学[M].北京:科学出版社,2004:145-155.
[22]LI L D,SHEN Q,YU J J,et al.Fe-USY zeolite catalyst for effective decomposition of nitrous oxide[J].Environmental Science&Technology,2007,41(22):7901-7906.
[23]KUMAR M S,SCHWIDDER M,GRNERT W,et al.On the nature of different iron sites and their catalytic role in Fe-ZSM-5DeNOx,catalysts:New insights by a combined EPR and UV/VIS spectroscopic approach[J].Journal of Catalysis,2004,227(2):384-397.
[24]LIU C,SHAN Y,YANG X,et al.Iron(II)-8-quinolinol/MCM-41-catalyzed phenol hydroxylation and reaction mechanism[J].Journal of Catalysis,1997,168(1):35-41.
[25]XIN H,LIU J,FAN F,et al.Mesoporous ferrosilicates with high content of isolated iron species synthesized in mild buffer solution and their catalytic application[J].Microporous&Mesoporous Materials,2008,113(1):231-239.
[26]LI B,XU J,LIU J,et al.Preparation of mesoporous ferrisilicate:Incorporation of iron onto mesoporous silica network by a novel route[J].Materials Letters,2012,78(7):147-149.
[27]ZHAO X,ZHANG X,HAO Z,et al.Synthesis of FeAPO-5 molecular sieves with high iron contents via improved ionothermal method and their catalytic performances in phenol hydroxylation[J].Journal of Porous Materials,2018,25(2):1007-1016.
[28]YANG R,LI G,HU C.The preparation of Fe/woodbased activated carbon catalyst for phenol hydroxylation from Fe2+and Fe3+precursors[J].Catalysis Science&Technology,2015,5(4):2486-2495.
[29]KAMEGAWA T,ANDO T,ISHIGURO Y.Hydroxylation of phenol on iron-containing mesoporous silica with hierarchical macroporous architecture[J].Bulletin of the Chemical Society of Japan,2015,88(4):572-574.
[30]DAI P,PETTY R,INGRAM C.et al.Metal substituted aluminophosphate molecular sieves as phenol hydroxylation catalysts[J].Applied Catalysis A:General,1996,143:101-110.