基于层状氢氧化物衍生复合氧载体的生物质化学链气化实验研究
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摘要
通过低饱和共沉淀法合成了类水滑石结构的层状氢氧化物(Layered Double Hydroxide,LDH)前驱体,经煅烧获得衍生Cu/Al/Zn、Cu/Al/Ni、Cu/Al/Ni/Zn高分散复合氧载体。采用XRD、XRF、H2-TPR、SEM及BET等分析手段对氧载体的结构及反应性能进行了表征,并通过固定床反应器开展了氧载体与生物质化学链气化实验。结果表明,合成的三种前驱体都具有典型的水滑石特征衍射峰,且层板稳定。Cu/Al/Zn前驱体层间厚度为0.264 2 nm,Ni2+引入后,层间距减小。前驱体煅烧后形成的复合氧载体中元素含量与制备试剂基本一致。氧载体中Zn、Ni元素的引入可提升Cu O的反应活性,降低H2还原的反应温度,Zn元素与Cu具有更好的协同作用。Cu/Al/Ni/Zn氧载体在固定床化学链气化中具有较好的碳转化率和气体产率,其碳转化率为82.03%。反应后氧载体比表面积为5.995 m2/g,具有较好的可再生性与抗烧结性,是生物质化学链气化反应较为理想的氧载体。
Layered double hydroxide( LDH) precursors with different metal elements were prepared by co-precipitation method at constant p H value; highly dispersed Cu / Al / Zn,Cu / Al / Ni and Cu / Al / Ni / Zn mixed metal oxygen carriers were obtained by calculation of the corresponding precursors. These oxygen carriers were characterized by XRD,XRF,H2-TPR,SEMand nitrogen adsorption and their activity in the chemical looping gasification( CLG) of biomass was investigated in a fixed bed reactor. The results indicated that typical hydrotalcite structure appears in the three precursors with stable layer board. The interlayer spacing of Cu / Al / Zn precursor is 0. 264 2 nm,larger than that of the Cu / Al / Ni precursor. The oxygen carriers derived from the corresponding precursors display similar elements contents as the preparation reagents. Due to the synergy among various metals,the Cu / Al / Ni / Zn oxygen carrier shows the highest reaction activity and anti-sintering ability.The addition of Ni and Zn has a positive effect on the activity of Cu O and reduce its reduction temperature; Zn shows a better synergistic effect than Ni with Cu. The carbon conversion reaches 82.03% for the CLG of biomass with Cu / Al / Ni / Zn as oxygen carrier; the surface area of Cu / Al / Ni / Zn remanis 5. 995 m2/ g after the CLG reaction,suggesting that it could be an ideal candidate for the CLG of biomass.
Layered double hydroxide( LDH) precursors with different metal elements were prepared by co-precipitation method at constant p H value; highly dispersed Cu / Al / Zn,Cu / Al / Ni and Cu / Al / Ni / Zn mixed metal oxygen carriers were obtained by calculation of the corresponding precursors. These oxygen carriers were characterized by XRD,XRF,H2-TPR,SEMand nitrogen adsorption and their activity in the chemical looping gasification( CLG) of biomass was investigated in a fixed bed reactor. The results indicated that typical hydrotalcite structure appears in the three precursors with stable layer board. The interlayer spacing of Cu / Al / Zn precursor is 0. 264 2 nm,larger than that of the Cu / Al / Ni precursor. The oxygen carriers derived from the corresponding precursors display similar elements contents as the preparation reagents. Due to the synergy among various metals,the Cu / Al / Ni / Zn oxygen carrier shows the highest reaction activity and anti-sintering ability.The addition of Ni and Zn has a positive effect on the activity of Cu O and reduce its reduction temperature; Zn shows a better synergistic effect than Ni with Cu. The carbon conversion reaches 82.03% for the CLG of biomass with Cu / Al / Ni / Zn as oxygen carrier; the surface area of Cu / Al / Ni / Zn remanis 5. 995 m2/ g after the CLG reaction,suggesting that it could be an ideal candidate for the CLG of biomass.
引文
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[2]UDOMSIRICHAKORN J,BASU P,ABDUL SALAM P,ACHARYA B.Ca O-based chemical looping gasification of biomass for hydrogenenriched gas production w ith in situ CO2capture and tar reduction[J].Fuel Process Technol,2014,127:7-12.
[3]HUANG Z,HE F,FENG Y,ZHAO K,ZHENG A,CHANG S,LI H.Synthesis gas production through biomass direct chemical looping conversion w ith natural hematite as an oxygen carrier[J].Bioresour Technol,2013,140:138-145.
[4]TIAN H,FISHER J C.Isotopic steam investigations of hematite(Fe2O3)for chemical looping combustion of methane[J].Catal Commun,2015,67:83-86.
[5]MEI D,ABAD A,ZHAO H,ADNEZ J.Characterization of a sol-gel derived Cu O/Cu Al2O4oxygen carrier for chemical looping combustion(CLC)of gaseous fuels:Relevance of gas-solid and oxygen uncoupling reactions[J].Fuel Process Technol,2015,133:210-219.
[6]SHEN L H,WU J H,XIAO J.Experiments on chemical looping combustion of coal with a Ni O based oxygen carrier[J].Combust Flame,2009,156(3):721-728.
[7]FORUTAN H R,KARIMI E,HAFIZI A,RAHIMPOUR M R,KESHAVARZ P.Expert representation chemical looping reforming:A comparative study of Fe,M n,Co and Cu as oxygen carriers supported on Al2O3[J].J Ind Eng Chem,2015,21:900-911.
[8]ADáNEZ-RUBIO I,GAYN P,ABAD A,DE DIEGO L F,GARCA-LABIANO F,ADNEZ J.Evaluation of a spray-dried Cu O/Mg Al2O4oxygen carrier for the chemical looping w ith oxygen uncoupling process[J].Energy Fuels,2012,26(5):3069-3081.
[9]SIRIWARDANE R,TIAN H,MILLER D,RICHARDS G.Fluidized bed testing of commercially prepared Mg O-promoted hematite and Cu OFe2O3mixed metal oxide oxygen carriers for methane and coal chemical looping combustion[J].Appl Energy,2015,157:348-357.
[10]LI K Z,WANG H,WEI Y G,YAN D X.Direct conversion of methane to synthesis gas using lattice oxygen of Ce O2-Fe2O3complex oxides[J].Chem Eng J,2010,156(3):512-518.
[11]刘洁翔,张晓光.阴离子插层镁铝水滑石结构及相互作用的理论研究[J].燃料化学学报,2013,41(6):761-768.(LIU Jie-xiang,ZHANG Xiang-guang.Theoretical investigation on the structure of anions intercalated Mg Al-layered double hydroxides and the interaction betw een anions and host layer[J].J Fuel Chem Technol,2013,41(6):761-768.)
[12]WANG L,DALIN L,WATANABE H,TAMURA M,NAKAGAWA Y,TOMISHIGE K.Catalytic performance and characterization of Co/M g/Al catalysts prepared from hydrotalcite-like precursors for the steam gasification of biomass[J].Appl Catal B:Environ,2014,150:82-92.
[13]SONG Q L,LIU W,CHRISTOPHER D B,RYAN N H,EASAN S,STUART A S,JOHN S D.A high performance oxygen storage material for chemical looping processes w ith CO2capture[J].Energy Environ Sci,2013,6(1):288-298.
[14]LONG H,XU Y,ZHANG X Q,HU S J,SHANG S Y,YIN Y X,DAI X Y.Ni-Co/Mg-Al catalyst derived from hydrotalcite-like compound prepared by plasma for dry reforming of methane[J].J Energy Chem,2013,22(5):733-739.
[15]LI B S,YUAN S L.Synthesis,characterization,and evaluation of Ti Mg Al Cu mixed oxides as novel SOxremoval catalysts[J].Ceram Int,2014,40(8):11559-11566.
[16]GALINDO R,LPEZ-DELGADO A,PADILLA I,YATES M.Hydrotalcite-like compounds:A way to recover a hazardous waste in the aluminium tertiary industry[J].Appl Clay,2014,95:41-49.
[17]BHUIYAN M R,LIN S D,HSIAO T C.Effect of calcination on Cu-Zn-loaded hydrotalcite catalysts for C-C bond formation derived from methanol[J].Catal Today,2014,226:150-159.
[18]DALIN L,KOIKE M,CHEN J H,NAKAGAWA Y,TOMISHIGE K.Preparation of Ni-Cu/Mg/Al catalysts from hydrotalcite-like compounds for hydrogen production by steam reforming of biomass tar[J].Int J Hydrogen Energy,2014,39(21):10959-10970.
[19]SIRIWARDANE R,TIAN H J,SIMONYI T,POSTON J.Synergetic effects of mixed copper-iron oxides oxygen carriers in chemical looping combustion[J].Fuel,2013,108:319-333.
[20]HUANG Z,HE F,FENG Y P,ZHAO K,ZHENG A Q,CHANG S,WEI G Q,ZHAO Z L,LI H B.Biomass char direct chemical looping gasification using Ni O-modified iron ore as an oxygen carrier[J].Energy Fuels,2014,28(1):183-191.
[21]朱锡锋.生物质热解原理与技术[M].合肥:中国科学技术大学出版社,2006.(ZHU Xi-feng.Biomass Pyrolysis Principle and Technology[M].Hefei:University of Science and Technology of China Press,2006.)
[22]LUCREDIO A F,ASSAF J M,ASSAF E M.Reforming of a model sulfur-free biogas on Ni catalysts supported on Mg(Al)O derived from hydrotalcite precursors:Effect of La and Rh addition[J].Biomass Bioenergy,2014,60:8-17.
[23]GAO P,LI F,XIAO F K,ZHAO N,WEI W,ZHONG L S,SUN Y H.Effect of hydrotalcite-containing precursors on the performance of Cu/Zn/Al/Zr catalysts for CO2hydrogenation:Introduction of Cu2+at different formation stages of precursors[J].Catal Today,2012,194(1):9-15.