五氧化二钒/铈改性二氧化钛催化甲醇高选择性氧化制备二甲氧基甲烷
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摘要
通过溶剂热法制备Ce掺杂的Ti O_2,利用等体积浸渍法制得一系列V_2O_5/Ce-TiO_2催化剂,并用于甲醇选择性氧化制二甲氧基甲烷(DMM)。采用XRD、UV-Vis、H_2-TPR、NH3-TPD等技术手段对催化剂进行了表征。结果表明,Ce掺杂改性后的TiO_2负载V_2O_5更有利于催化剂表面钒氧物种的分散,且钒氧物种主要以孤立的和聚合态的形式存在,没有形成V_2O_5晶相结构。Ce掺杂改性后,改变了TiO_2载体与钒氧物种间的作用力,Ce掺杂量越大,钒氧物种的还原温度逐渐向高温移动,使得催化剂的氧化还原能力减弱。Ce改性的TiO_2负载V_2O_5,Ce的改性量对催化剂的酸性质几乎没有影响,但是催化剂的酸性却随着V_2O_5负载量的增大而逐渐减弱。当Ce和Ti的摩尔比为0.01,V_2O_5的负载量为10%所得催化剂10V/1Ce-TiO_2具有较为适宜的氧化还原性和酸性,在反应温度160℃时,甲醇的转化率为39.6%,DMM的选择性高达99.9%。
The composite Ce-TiO_2 support was prepared through solvothermal treament of Ce( NO_3)_3 and butyl titanate. A series of V_2O_5/ Ce-TiO_2 catalysts with different vanadium loadings were obtained by incipient impregnation with ammonium metavanadate solution. The catalytic properties of V_2O_5/ Ce-TiO_2 for selective oxidation of methanol to dimethoxymethane( DMM) were investigated. The V_2O_5/ Ce-TiO_2 catalysts were characterized by XRD,UV-Vis,H_2-TPR,and NH_3-TPD. The results show that the dispersion of vanadium species is improved on the surface of Ce modified TiO_2. The interaction between vanadium species and supports is changed. The reduction temperature increases with the increasing Ce content. The Ce content in modified TiO_2 does not affect the acidity of the V2O5 supported catalysts,but the acidity of the catalysts decreases with the increasing of V_2O_5 content. For the catalyst of 10 V /1Ce-TiO_2( The numbers 10 and 1represent the mass percentage of V_2O_5 in the catalyst and molar ratio of Ce and TiO_2,respectively),the methanol conversion and DMM selectivity reach 39. 6% and 99. 9%,respectively,at 160 ℃.
The composite Ce-TiO_2 support was prepared through solvothermal treament of Ce( NO_3)_3 and butyl titanate. A series of V_2O_5/ Ce-TiO_2 catalysts with different vanadium loadings were obtained by incipient impregnation with ammonium metavanadate solution. The catalytic properties of V_2O_5/ Ce-TiO_2 for selective oxidation of methanol to dimethoxymethane( DMM) were investigated. The V_2O_5/ Ce-TiO_2 catalysts were characterized by XRD,UV-Vis,H_2-TPR,and NH_3-TPD. The results show that the dispersion of vanadium species is improved on the surface of Ce modified TiO_2. The interaction between vanadium species and supports is changed. The reduction temperature increases with the increasing Ce content. The Ce content in modified TiO_2 does not affect the acidity of the V2O5 supported catalysts,but the acidity of the catalysts decreases with the increasing of V_2O_5 content. For the catalyst of 10 V /1Ce-TiO_2( The numbers 10 and 1represent the mass percentage of V_2O_5 in the catalyst and molar ratio of Ce and TiO_2,respectively),the methanol conversion and DMM selectivity reach 39. 6% and 99. 9%,respectively,at 160 ℃.
引文
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[20]Gao X T,Wachs I E.Molecular Engineering of Supported Vanadium Oxide Catalysts Through Support Modification[J].Topics Catal,2002,18(3/4):243-250
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[23]GUO Heqin,LI Debao,CHEN Congbiao,et al.One-Step Oxidation of Methanol to Dimethoxymethane on V2O5/Ce O2Catalyst[J].Chinese J Catal,2012,33(5):813-818(in Chinese).郭荷芹,李德宝,陈从标,等.V2O5/Ce O2催化剂上甲醇氧化一步法合成二甲氧基甲烷[J].催化学报,2012,33(5):813-818.
[24]Eraiah R K,Madras G.Metal-metal Charge Transfer and Interfacial Charge Transfer Mechanism for the Visible Light Photocatalytic Activity of Cerium and Nitrogen Co-doped Ti O2[J].J Sol Gel Sci Technol,2014,71(2):193-203.
[25]Lu X L,Qin Z F,Dong M,et al.Selective Oxidation of Methanol to Dimethoxymethane over Acid-modified V2O5/Ti O2Catalysts[J].Fuel,2011,90(4):1335-1339.
[26]Berndt H,Martin A,Br ckner A,et al.Structureand Catalytic Properties of VOx/MCM Materials for the Partial Oxidation of Methane to Formaldehyde[J].J Catal,2000,191(2):384-400.
[27]Peńa M L,Dejoz A,Fornés V,et al.V-containing MCM-41 and MCM-48 Catalysts for the Selective Oxidation of Propane in Gasphase[J].Appl Catal A,2001,209(1/2):155-64.
[28]Zhao H Y,Bennici S,Shen J,et al.Influence of the Host Oxide of Sulfated-titania Catalysts on Partial Cxidation Methanol Reaction[J].Appl Catal A,2010,385(1/2):224-231.
[29]Liu H C,Iglesia E.Selective One-Step Synthesis of Dimethoxymethane via Methanol or Dimethyl Ether Oxidation on H3+nVnMo12-nPO40Keggin Structures[J].J Phys Chem B,2003,107(39):10840-10847.
[2]Li H,Li J P,Xiao F K,et al.One-step Synthesize of Dimethoxymethane from Methanol over Mn/Re/Cu Catalysts[J].J Fuel Chem Technol,2009;37(5):613-617.
[3]Royer S,Sécordel X,Brandhorst M,et al.Amorphous Oxide as a Novel Efficient Catalyst for Direct Selective Oxidation of Methanol to Dimethoxymethane[J].Chem Commun,2008,7(7):865-867.
[4]MU Shifang,SHANG Rujing,WEI Lingchao,et al.Research Progress in Catalyst System for One-step Selective Oxidation of Methanol to Methylal[J].Mod Chem Ind,2011,31(5):11-15(in Chinese).穆仕芳,尚如静,魏灵朝,等.甲醇选择氧化一步法制甲缩醛催化体系研究进展[J].现代化工,2011,31(5):11-15.
[5]Anthony C R,White L M.Selective Electrochemical Oxidation of Methanol to Dimethoxymethane Using Ru/Sn Catalysts[J].J Mol Catal A,2005,227(1/2):113-117.
[6]ZHANG Shenghong,ZHANG Hongpeng,LI Weizhen,et al.Effects of Zirconia Crystallite Phases on the Structures of Mo Ox/Zr O2Catalysts and Their Properties in the Selective Oxidation of Methanol[J].Acta Phys Chim Sin,2010,26(7):1879-1886(in Chinese).张胜红,张鸿鹏,李为臻,等.Zr O2晶相对Mo Ox/Zr O2催化剂结构及其甲醇选择氧化性能的影响[J].物理化学学报,2010,26(7):1879-1886.
[7]Fu Y C,Shen J S.Selective Oxidation of Methanol to Dimethoxymethane under Mild Conditions over V2O5/Ti O2with Enhanced Surface Acidity[J].Chem Commun,2007,21(21):2172-2174.
[8]Li H,Li J P,Xiao F K,et al.One-step Synthesis of Dimethoxymethane from Methanol over Mn/Re/Cu Catalysts[J].J Fuel Chem Technol,2009,37(5):613-617.
[9]Fuji K,Nakano S,Fujita E.An Improved Method for Methoxymethylation of Alcohols Under Mild Acidic Conditions[J].Synthesis,1975,4:276-277.
[10]Zhang Y H,Drake I J,Briggs D N,et al.Synthesis of Dimethyl Carbonate and Dimethoxy Methane over Cu-ZSM-5[J].J Catal,2006,244(2):219-229.
[11]XU Chunmei,ZHANG Mingsen.Preparation of Methylal from Methanol and Polyoxymethylene[J].Petrochem Technol,2008,37(9):896-899(in Chinese).许春梅,张明森.甲醇与多聚甲醛反应制备甲缩醛[J].石油化工,2008,37(9):896-899.
[12]Fu Y C,Zhu H Y,Shen J Y.Thermal Decomposition of Dimethoxymethane and Dimethyl Carbonate Catalyzed by Solid Acids and Bases[J].Thermochim Acta,2005,435(1/2):88-92.
[13]Liu J W,Fu Y C,Sun Q,et al.Ti O2Nanotubes Supported V2O5for the Selective Cxidation of Methanol to Dimethoxymethane[J].Micro Meso Mater,2008,116(1/2/3):614-621.
[14]Kaichev V V,Popova G Y,Chesalov Y A,et al.Selective Oxidation of Methanol to Form Dimethoxymethane and Methyl Formate over a Monolayer V2O5/Ti O2Catalyst[J].J Catal,2014,311(3):59-70.
[15]Fan Z H,Guo H Q,Fang K G,et al.Efficient V2O5/Ti O2Composite Catalysts for Dimethoxymethane Synthesis from Methanol Selective Oxidation[J].RSC Adv,2015,5(31):24795-24802.
[16]Sun Q,Fu Y C,Liu J W,et al.Structural,Acidic and Redox Properties of V2O5-Ti O2-SO2-4Catalysts[J].Appl Catal A,2008,334(1/2):26-34.
[17]Yuan Y Z,Shido T,Iwasawa Y.The New Catalytic Property of Supported Rhenium Oxides for Selective Oxidation of Methanol to Methylal[J].Chem Commun,2000,15(46):1421-1422.
[18]WU Jianbing,WANG Hui,QIN Zhangfeng,et al.Selective Oxidation of Methanol to Dimethoxymethane over V2O5/Ti O2-Zr O2[J].J Fuel Chem Technol,2011,39(1):64-68(in Chinese).武建兵,王辉,秦张峰,等.V2O5/Ti O2-Zr O2催化剂上甲醇选择氧化制甲缩醛[J].燃料化学学报,2011,39(1):64-68.
[19]CHEN Wenlong,LIU Haichao.Relationship Between the Structures of Metal Oxide Catalysts and Their Properties in Selective Oxidation of Methanol[J].Acta Phys Chim Sin,2012,28(10):2315-2326(in Chinese).陈文龙刘海超.甲醇选择氧化金属氧化物催化剂的结构与其催化性能的关系[J].物理化学学报,2012,28(10):2315-2326.
[20]Gao X T,Wachs I E.Molecular Engineering of Supported Vanadium Oxide Catalysts Through Support Modification[J].Topics Catal,2002,18(3/4):243-250
[21]Goodrow A,Bell A T.A Theoretical Investigation of the Selective Oxidation of Methanol to Formaldehyde on Isolated Vanadate Species Supported on Titania[J].J Phys Chem C,2008,112(34):13204-13214
[22]Lee S M,Chong S.Promotional Effect of Vanadium on the Selective Catalytic Oxidationof NH3to N2over Ce/V/Ti O2Catalyst[J].Appl Catal B,2015,163(163):30-39.
[23]GUO Heqin,LI Debao,CHEN Congbiao,et al.One-Step Oxidation of Methanol to Dimethoxymethane on V2O5/Ce O2Catalyst[J].Chinese J Catal,2012,33(5):813-818(in Chinese).郭荷芹,李德宝,陈从标,等.V2O5/Ce O2催化剂上甲醇氧化一步法合成二甲氧基甲烷[J].催化学报,2012,33(5):813-818.
[24]Eraiah R K,Madras G.Metal-metal Charge Transfer and Interfacial Charge Transfer Mechanism for the Visible Light Photocatalytic Activity of Cerium and Nitrogen Co-doped Ti O2[J].J Sol Gel Sci Technol,2014,71(2):193-203.
[25]Lu X L,Qin Z F,Dong M,et al.Selective Oxidation of Methanol to Dimethoxymethane over Acid-modified V2O5/Ti O2Catalysts[J].Fuel,2011,90(4):1335-1339.
[26]Berndt H,Martin A,Br ckner A,et al.Structureand Catalytic Properties of VOx/MCM Materials for the Partial Oxidation of Methane to Formaldehyde[J].J Catal,2000,191(2):384-400.
[27]Peńa M L,Dejoz A,Fornés V,et al.V-containing MCM-41 and MCM-48 Catalysts for the Selective Oxidation of Propane in Gasphase[J].Appl Catal A,2001,209(1/2):155-64.
[28]Zhao H Y,Bennici S,Shen J,et al.Influence of the Host Oxide of Sulfated-titania Catalysts on Partial Cxidation Methanol Reaction[J].Appl Catal A,2010,385(1/2):224-231.
[29]Liu H C,Iglesia E.Selective One-Step Synthesis of Dimethoxymethane via Methanol or Dimethyl Ether Oxidation on H3+nVnMo12-nPO40Keggin Structures[J].J Phys Chem B,2003,107(39):10840-10847.