活性形貌对CuO/ZnO/Al_2O_3催化加氢反应的影响
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摘要
以硝酸铜、硝酸锌等为原料,采用沉淀-沉积法制备了载体是介孔Al_2O_3的CuO/ZnO/Al_2O_3催化剂,通过改变焙烧时间可得到不同活性组分形貌(团簇球状和棒状)的催化剂,并用于CO/CO_2加氢反应。通过XRD、BET、N_2吸附-脱附、TEM、H_2-TPR、CO_2-TPD、NH_3-TPD和FTIR对催化剂进行了表征与测试。结果表明,活性组分(CuO/ZnO)形貌的改变影响了催化剂的Cu O晶粒尺寸、比表面积、孔径及其还原性能,且对催化剂的酸性位点和碱性位点的相对数量影响较大。团簇球状催化剂中活性组分的分散度高、易还原、碱性位多、酸性位少,有利于甲醇的生成;而棒状催化剂中孔道不均匀、碱性位少、酸性位多,更有利于二甲醚(DME)的生成。活性测试结果表明,团簇球状催化剂表现出高甲醇选择性(95.05%)和低DME选择性(4.18%);棒状催化剂的产物选择性与团簇球状相反,表现出高DME选择性(75.41%)和低甲醇选择性(12.81%)。
CuO/ZnO/Al_2O_3 catalysts with mesoporous Al_2O_3 as support were prepared by precipitationdeposition method using cupric nitrate and zinc nitrate as raw materials.Catalysts possessing differen active component morphologies(globular clusters and rod-like structure)were obtained by changing calcination time and used for CO/CO_2 hydrogenation reaction.The catalysts were characterized and tested by XRD,BET,N_2 adsorption-desorption,TEM,H_2-TPR,CO_2-TPD,NH_3-TPD and FTIR.The results showed that the morphology of the active components affects the CuO grain size,specific surface area,pore size and reduction performance of the catalyst and has a great influence on the relative quantity of acid sites and basic sites of the catalysts.The catalyst with globular clusters has high dispersion of active components easy to reduce,more basic sites and less acid sites,which is favorable for the formation of methanol.While the rod-like catalyst has uneven pores,less basic sites and more acid sites,which is more conducive to the formation of dimethyl ether(DME).The activity test results revealed that the catalyst with globular clusters exhibited high methanol selectivity(95.05%)and low DME selectivity(4.18%).The rod-like catalyst displayed the opposite trend with high DME selectivity(75.41%)and low methanol selectivity(12.81%).
CuO/ZnO/Al_2O_3 catalysts with mesoporous Al_2O_3 as support were prepared by precipitationdeposition method using cupric nitrate and zinc nitrate as raw materials.Catalysts possessing differen active component morphologies(globular clusters and rod-like structure)were obtained by changing calcination time and used for CO/CO_2 hydrogenation reaction.The catalysts were characterized and tested by XRD,BET,N_2 adsorption-desorption,TEM,H_2-TPR,CO_2-TPD,NH_3-TPD and FTIR.The results showed that the morphology of the active components affects the CuO grain size,specific surface area,pore size and reduction performance of the catalyst and has a great influence on the relative quantity of acid sites and basic sites of the catalysts.The catalyst with globular clusters has high dispersion of active components easy to reduce,more basic sites and less acid sites,which is favorable for the formation of methanol.While the rod-like catalyst has uneven pores,less basic sites and more acid sites,which is more conducive to the formation of dimethyl ether(DME).The activity test results revealed that the catalyst with globular clusters exhibited high methanol selectivity(95.05%)and low DME selectivity(4.18%).The rod-like catalyst displayed the opposite trend with high DME selectivity(75.41%)and low methanol selectivity(12.81%).
引文
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[29]Sabour B,Peyrovi M H,HamouleT,et al.Catalytic dehydration of methanol to dimethyl ether(DME)over Al-HMS catalysts[J].Journal of Industrial and Engineering Chemistry,2014,20:222-227.
[30]Khandan N,Kazemeini M,Aghaziarati M,et al.Determining an optimum catalyst for liquid-phase dehydration of methanol to dimethyl ether[J].Applied Catalysis A:General,2008,349:6-12.
[31]Guangjun L,Chuantao G,Wanbin Z,et al.Hydrogen production from methanol decomposition using Cu-Al spinel catalysts[J].Journal of Cleaner Production,2018,183:415-423.
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[2]Branco J B,Ferreira A C,Goncalves A P,et al.Synthesis of methanol using copper-f block element bimetallic oxidesas catalysts and greenhouse gases(CO2,CH4)as feedstock[J].Journal of Catalysis,2016,341:24-32.
[3]Ben S,Yuan F,Zhu Y.Effect of Zr addition on catalytic performance of Cu-Zn-Al oxides for CO2 hydrogenation to methanol[J].Chemical Research in Chinese University,2016,32(6):1005-1009.
[4]Wu J,Saito M,Takeuchi M,et al.The stability of Cu/ZnO-based catalysts in methanol synthesis from a CO2-rich feed and from a CO-rich feed[J].Applied Catalysis A:General,2001,218:235-240.
[5]Dong X,Liu X,Chen Y,et al.Screening of bimetallic M-Cu-BTCMOFs for CO2 activation and mechanistic study of CO2 hydrogenation to formic acid:A DFT study[J].Journal of CO2 Utilization,2018,24:64-72
[6]Gupta M,Smith M L,Spivey J J.Heterogeneous catalytic conversion of dry syngas to ethanol and higher alcohols on Cu-based catalysts[J].ACS Catalysis,2011,1(6):641-656.
[7]Gong J L,Yue H R,Zhao Y J,et al.Synthesis of ethanol via syngas on Cu/SiO2 catalysts with balanced Cu0-Cu+sites[J].Journal of the American Chemical Society,2012,134(34):13922-13925.
[8]Zhang Q,Fan F,Xu G,et al.Steam reforming of dimethyl ether over a novel anodic g-Al2O3 supported copper bi-functional catalyst[J].International Journal of Hydrogen Energy,2013,38:10305-10314.
[9]Xiao J,Mao D,Guo X M,et al.Effect of TiO2,ZrO2,and TiO2-ZrO2on the performance of CuO-ZnO catalyst for CO2 hydrogenation to methanol[J].Applied Surface Science,2015,338:146-153.
[10]Yoshihara J,Campbell C T.Methanol synthesis and reverse water-gas shift kinetics over Cu(110),model catalysts:structural sensitive[J].Journal of Catalysis.1996,161(2):776-782.
[11]Peter C,Ib C,Ida K,et al.Transient behavior of Cu/ZnO-based methanol synthesis catalysts[J].Journal of Catalysis,2009,262:65-72.
[12]Yuan Q,Yin A X,Luo C,et al.Facile synthesis for ordered mesoporousγ-aluminas with high thermal stability[J].Journal of the American Chemical Society,2008,130:3465-3472.
[13]Morris S M,Fulvio P F,Jaroniec M.Ordered mesoporous aluminasupported metal oxides[J].Journal of the American Chemical Society,2008,130:15210-15216.
[14]Kanjanasoontorn N,Permsirivanich T,Numpilai T,et al.Structureactivity relationships of hierarchical meso-macroporous alumina supported copper catalysts for CO2 hydrogenation:effects of calcination temperature of alumina support[J].Catalysis Letters,2016,146:1943-1955.
[15]Wang Y,Chen Y,Yu F,et al.One-step synthesis of dimethyl ether from syngas on ordered mesoporous copper incorporated alumina[J].Journal of Energy Chemistry,2016,25:775-781.
[16]Ham H,Kim J,Cho S J,et al.Enhanced stability of spatially confined copper nanoparticles in an ordered mesoporous alumina for dimethyl ether synthesis from syngas[J].ACS Catalysis,2016,6:5629-5640.
[17]Witoon T,Bumrungsalee S,Chareonpanich M,et al.Effect of hierarchical meso-macroporous alumina-supported copper catalyst for methanol synthesis from CO2 hydrogenation[J].Energy Conversion and Management,2015,103:886-894.
[18]Baltes C,Vukojevi S,Schuth F.Correlations between synthesis,precursor,and catalyst structure and activity of a large set of CuO/ZnO/Al2O3 catalysts for methanol synthesis[J].Journal of Catalysis,2008,258:334-344.
[19]Galván Cá,Schumann J,Behrens M,et al.Reverse water-gas shift reaction at the Cu/ZnO interface:influence of the Cu/Zn ratio on structure-activity correlations[J].Applied Catalysis B Environmental,2016,195:104-111.
[20]Lei H,Nie R,Wu G,et al.Hydrogenation of CO2 to CH3OH over Cu/ZnO catalysts with different ZnO morphology[J].Fuel,2015,154:161-166.
[21]Valant A L,Comminges C,Tisseraud C,et al.The Cu-ZnO synergy in methanol synthesis from CO2,Part 1:Origin of active site explained by experimental studies and a sphere contact quantification model on Cu+Zn O mechanical mixtures[J].Journal of Catalysis,2015,324:41-49.
[22]Hong L,Hou Z,Xie J.Hydrogenation of CO2 to CH3OH over CuO/ZnO/Al2O3 catalysts prepared via a solvent-free routine[J].Fuel,2016,164:191-198.
[23]Zhu Y F,Kong X,Li X Q,et al.Cu nanoparticles inlaid mesoporous Al2O3 as a high-performance bifunctional catalyst for ethanol synthesis via dimethyl oxalate hydrogenatin[J].ACS Catalysis,2014,4:3612-3620.
[24]Takeishi K,Wagatsuma Y,Ariga H,et al.Promotional effect of water on direct dimethyl ether synthesis from carbon monoxide and hydrogen catalyzed by Cu-Zn/Al2O3[J].ACS Sustainable Chemistry&Engineering,2017,5:3675-3680.
[25]Frusteri F,Cordaro M,Cannilla C,et al.Multifunctionality of Cu-ZnO-ZrO2/H-ZSM5 catalysts for the one-step CO2-to-DMEhydrogenation rection[J].Applied Catalysis B:Environmental,2015,162:57-65.
[26]Berg R V D,Prieto G,Korpershoek G,et al.Structure sensitivity of Cu and CuZn Catalysts relevant to industrial methanol synthesis[J].Nature Communications,2016,7:13057.
[27]Yang H Y,Gao P,Zhang C,et al.Core-shell structured Cu@m-SiO2and Cu/ZnO@m-SiO2 catalysts formethanol synthesis from CO2hydrogenation[J].Catalysis Communications,2016,84:56-60.
[28]Hosseini S Y,Nikou M R K.Investigation of different precipitating agents effects on performance ofγ-Al2O3 nanocatalysts for methanol dehydration to dimethyl ether[J].Journal of Industrial and Engineering Chemistry,2014,20:4421-4428.
[29]Sabour B,Peyrovi M H,HamouleT,et al.Catalytic dehydration of methanol to dimethyl ether(DME)over Al-HMS catalysts[J].Journal of Industrial and Engineering Chemistry,2014,20:222-227.
[30]Khandan N,Kazemeini M,Aghaziarati M,et al.Determining an optimum catalyst for liquid-phase dehydration of methanol to dimethyl ether[J].Applied Catalysis A:General,2008,349:6-12.
[31]Guangjun L,Chuantao G,Wanbin Z,et al.Hydrogen production from methanol decomposition using Cu-Al spinel catalysts[J].Journal of Cleaner Production,2018,183:415-423.
[32]Jiang H Q,Bongard H,Schmidt W,et al.One-pot synthesis of mesoporous Cu-γ-Al2O3 as bifunctional catalyst for direct dimethyl ether synthesis[J].Microporous and Mesoporous Materials,2012,164:3-8.