Cu-Mg-Al催化剂催化甲醇裂解制氢的研究
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摘要
利用共沉淀法制备了一系列不同铜镁铝摩尔比的Cu-Mg-Al催化剂,并用于固定床上甲醇裂解制氢的研究。采用BET、XRD、H_2-TPR和CO_2-TPD等表征手段对催化剂的结构和物化性质进行表征,并分析其对甲醇制氢反应催化性能的影响。结果表明,以1∶2∶1的铜镁铝摩尔比制得的催化剂对甲醇裂解制氢反应具有较高的催化活性,可改善前驱体的结晶度,增大催化剂的比表面积,增强催化剂的可还原性和碱性,从而提高了甲醇裂解制氢的转化率和气体收率,并抑制了液相副产物的生成。使用该催化剂,在压力为1. 0 MPa、反应温度为280℃、体积空速为0. 5 h~(-1)的反应条件下,甲醇的转化率为99. 28%,气体收率为97. 75%,液相副产物质量分数为1. 25%,反应稳定运行180 h后催化剂未发现明显失活。
A series of Cu-Mg-Al catalysts with different Cu/Mg/Al molar ratio are prepared via co-precipitation method.Their catalytic performance for hydrogen production by methanol cracking is investigated in a fixed bed rector and their structure and physic-chemical properties are characterized by BET,XRD,H_2-TPR,CO_2-TPD,etc.The results show that Cu-Mg-Al catalyst with a Cu/Mg/Al molar ratio of 1 ∶2 ∶1 can enhance catalytic performance for hydrogen production by methanol cracking because it has an increased crystallinity of the precursor,a larger surface area,an enhanced reducibility and an improved alkalinity. The conversion rate of methanol can reach 99. 28%,the gas yield can achieve 97. 75% and the content of byproducts in liquid phase is as low as 1. 25% when the reaction is performed over Cu_1Mg_2Al_1 catalyst under the reaction conditions that the pressure is 1. 0 MPa,reaction temperature at 280℃ and volume space velocity at 0. 5 h~(-1).After experiencing 180 h of reaction,the catalyst does not show deactivation in the system.
A series of Cu-Mg-Al catalysts with different Cu/Mg/Al molar ratio are prepared via co-precipitation method.Their catalytic performance for hydrogen production by methanol cracking is investigated in a fixed bed rector and their structure and physic-chemical properties are characterized by BET,XRD,H_2-TPR,CO_2-TPD,etc.The results show that Cu-Mg-Al catalyst with a Cu/Mg/Al molar ratio of 1 ∶2 ∶1 can enhance catalytic performance for hydrogen production by methanol cracking because it has an increased crystallinity of the precursor,a larger surface area,an enhanced reducibility and an improved alkalinity. The conversion rate of methanol can reach 99. 28%,the gas yield can achieve 97. 75% and the content of byproducts in liquid phase is as low as 1. 25% when the reaction is performed over Cu_1Mg_2Al_1 catalyst under the reaction conditions that the pressure is 1. 0 MPa,reaction temperature at 280℃ and volume space velocity at 0. 5 h~(-1).After experiencing 180 h of reaction,the catalyst does not show deactivation in the system.
引文
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[3]Raróg-Pilecka W,Szmigiel D,Kowalczyk Z,et al.Ammonia decomposition over the carbon-based ruthenium catalyst promoted with barium or cesium[J].Journal of Catalysis,2003,218(2):465-469.
[4]Patel S,Pant K K.Selective production of hydrogen via oxidative steam reforming of methanol using Cu-Zn-Ce-Al oxide catalysts[J].Chemical Engineering Science,2007,62(18-20):5436-5443.
[5]Ilinich O,Ruettinger W,Liu X.Cu-Al2O3-CuAl2O4water-gas shift catalyst for hydrogen production in fuel cell applications:Mechanism of deactivation under start-stop operating conditions[J].Journal of Catalysis,2007,247(1):112-118.
[6]Wang X,Gorte R J.A study of steam reforming of hydrocarbon fuels on Pd/ceria[J].Applied Catalysis A General,2002,224(1):209-218.
[7]S S,Silva H,Brand2o L,et al.Catalysts for methanol steam reforming-A review[J].Applied Catalysis B Environmental,2010,99(1):43-57.
[8]Matsumura Y,Tanaka K,Tode N,et al.Catalytic methanol decomposition to carbon monoxide and hydrogen over nickel supported on silica[J].Journal of Molecular Catalysis A Chemical,2000,152(1):157-165.
[9]Shen G C,S.I F,Matsumoto S,et al.Steam reforming of methanol on binary Cu/Zn O catalysts:Effects of preparation condition upon precursors,surface structure and catalytic activity[J].Journal of Molecular Catalysis A Chemical,1997,124(2):123-136.
[10]Velu S,Suzuki K,Osaki T.Selective production of hydrogen by partial oxidation of methanol over catalysts derived from CuZnAlayered double hydroxides[J].Catalysis Letters,1999,62(2-4):159-167.
[11]周性东,陈晓蓉,梅华.Mg O改性CuZnAl催化剂上甲醇裂解制氢[J].精细化工,2016,33(5):541-545.
[12]Zhang S,Liu Q,Fan G,et al.Highly-dispersed copper-based catalysts from Cu-Zn-Al layered double hydroxide precursor for gasphase hydrogenation of dimethyl oxalate to ethylene glycol[J].Catalysis Letters,2012,142(9):1121-1127.
[13]申延明,吴静,唐杨军,等.CuMgAl类水滑石的制备与表征(英文)[J].硅酸盐学报,2009,37(2):285-290.
[14]Zhe-Ming N I,Xue J L.Synthesis of CuMgAl layered double hydroxides for efficient photocatalysis of rhodamine B[J].Chemical Journal of Chinese Universities,2013,34(3):503-508.
[15]Feng,A Y J,Li B,et al.Synthesis and structural analysis of Cu-NiMg-Al-CO3hydrotalcite-like materials[J].Acta Chimica Sinica,2003,61(1):78-83.
[16]Hui Z.Studies on structures and properties of Mg Al and Mg Fe layered double hydroxides[J].Chinese Journal of Inorganic Chemistry,2002,18(8):833-838.
[17]冯拥军,李殿卿,李春喜,等.Cu-Ni-Mg-Al-CO3四元水滑石的合成及结构分析[J].化学学报,2003,61(1):78-83.
[18]Chen T,Huifang X U,Wang Y,et al.Structural evolvement of heating treatment of Mg/Al-LDH and preparation of mineral mesoporous materials[J].Acta Geologica Sinica English Edition,2006,80(2):170-174.
[19]Kannan S,Dubey A,Knozinger H.Synthesis and characterization of CuMgAl ternary hydrotalcites as catalysts for the hydroxylation of phenol[J].Journal of Catalysis,2005,231(2):381-392.
[20]温斌,何鸣元,宋家庆,等.含铜类水滑石催化材料热分解过程的研究[J].无机化学学报,2000,16(1):58-62.
[21]张国强,李集伟,杨乐夫,等.阳离子掺杂水滑石的制备及其性质研究[J].物理化学学报,2006,22(2):146-151.
[22]杨行远,徐广通,卢立军,等.TPR技术及其在催化研究中的应用现状[J].现代科学仪器,2012,(6):57-61.