Co负载量对Co/TiO_2催化CO_2甲烷化性能影响
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摘要
采用沉淀-沉积法制备出w(Co)=10%、15%、20%和25%的Co/TiO_2催化剂,并用于催化CO_2甲烷化反应。通过XRD、TEM、N_2吸附-脱附、H_2程序升温还原(H_2-TPR)和CO_2程序升温脱附(CO_2-TPD)对催化剂进行了表征与测试。结果表明,Co的负载影响了催化剂中Co3O4晶粒尺寸、比表面积、孔径以及催化剂的还原性能,且Co物种与TiO_2载体发生了强相互作用。其中,w(Co)=20%的Co/TiO_2催化剂中Co颗粒平均尺寸约为8nm,比表面积及孔径分别为40.9 m2/g和6.96 nm,且Co分散度达10.1%,从而更有利于CO_2甲烷化反应。此外,w(Co)=20%的Co/TiO_2催化剂表面具有最大的中强碱位量(28μmol/g),从而可活化更多的CO_2。活性测试结果表明,当反应温度为400℃、压力0.5 MPa、原料气空速3 600 m L/(g·h)、V(H_2)/V(CO_2)=4时,w(Co)=20%的Co/TiO_2催化剂的活性最好,其CO_2转化率和CH_4选择性可分别达到69.9%和98.3%,且在20 h内保持稳定。
A series of Co/TiO_2 catalysts with different Co loadings amounts[w( Co) = 10%,15%,20% and25% ]were prepared by deposition-precipitation method. The catalytic performances for the CO_2 methanation were investigated. These catalysts were characterized by XRD,TEM,N2 adsorption-desorption,temperature programmed reduction of hydrogen( H2-TPR),and temperature programmed desorption of carbon dioxide( CO_2-TPD). The results showed the Co loading amount could affect the crystallite size of Co_3O_4,the BET surface area and reducing properties of catalysts,and a strong interaction was observed between Co species and TiO_2. The Co/TiO_2 catalyst with 20% Co loading amount exhibited a smaller Co particle size of 8 nm and a good Co dispersion of 10. 1%,and the BET surface area and pore size were 40. 9 m2/g and 6. 96 nm,respectively,which would favor the CO_2 methanation. In addition,a maximum medium basicity of 28 μmol/g was observed on the Co/TiO_2 catalyst with 20% Co loading amount,indicating more CO_2 molecules were activated on the catalyst surface. The activity test indicated that the optimal catalytic performance was obtained over Co/TiO_2 catalyst with 20% Co loading amount showed the best catalytic performance and kept stable in 20 h,under the conditions of 400 ℃,0. 5 MPa,a gaseous hourly space velocity of 3 600 m L/( g·h) and V( H2)/V( CO_2) =4,and the CO_2 conversion and methane selectivity were 69. 9% and 98. 3%,respectively.
A series of Co/TiO_2 catalysts with different Co loadings amounts[w( Co) = 10%,15%,20% and25% ]were prepared by deposition-precipitation method. The catalytic performances for the CO_2 methanation were investigated. These catalysts were characterized by XRD,TEM,N2 adsorption-desorption,temperature programmed reduction of hydrogen( H2-TPR),and temperature programmed desorption of carbon dioxide( CO_2-TPD). The results showed the Co loading amount could affect the crystallite size of Co_3O_4,the BET surface area and reducing properties of catalysts,and a strong interaction was observed between Co species and TiO_2. The Co/TiO_2 catalyst with 20% Co loading amount exhibited a smaller Co particle size of 8 nm and a good Co dispersion of 10. 1%,and the BET surface area and pore size were 40. 9 m2/g and 6. 96 nm,respectively,which would favor the CO_2 methanation. In addition,a maximum medium basicity of 28 μmol/g was observed on the Co/TiO_2 catalyst with 20% Co loading amount,indicating more CO_2 molecules were activated on the catalyst surface. The activity test indicated that the optimal catalytic performance was obtained over Co/TiO_2 catalyst with 20% Co loading amount showed the best catalytic performance and kept stable in 20 h,under the conditions of 400 ℃,0. 5 MPa,a gaseous hourly space velocity of 3 600 m L/( g·h) and V( H2)/V( CO_2) =4,and the CO_2 conversion and methane selectivity were 69. 9% and 98. 3%,respectively.
引文
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[34]Zhou R,Rui N,Fan Z,et al.Effect of the structure of Ni/Ti O2catalyst on CO2methanation[J].International Journal of Hydrogen Energy,2016,41(47):22017-22025.
[35]Fei Jinhua(费金华),Hou Zhaoyin(侯昭胤),Qi Gongxin(齐共新),et al.Methanation of carbon dioxide by hydrogenating over Ni supported on Al2O3catalysts[J].Chemical Journal of Chinese Universities(高等学校化学学报),2002,23(3):457-460.
[36]Thiessen J,Rose A,Meyer J,et al.Effects of manganese and reduction promoters on carbon nanotube supported cobalt catalysts in Fischer-Tropsch synthesis[J].Microporous and Mesoporous Materials,2012,164:199-206.
[37]Han C W,Majumdar P,Marinero E E,et al.Highly stable bimetallic Au-lr/Ti O2catalyst:physical origins of the intrinsic high stability against sintering[J].Nano Letters,2015,15(12):8141-8147.
[38]Hsieh B-J,Tsai M-C,Pan C-J,et al.Tuning metal support interactions enhances the activity and durability of Ti O2-supported Pt nanocatalysts[J].Electrochimica Acta,2017,224:452-459.
[39]Gao Y,Liang Y,Chambers S A.Thermal stability and the role of oxygen vacancy defects in strong metal support interaction-Pt on Nbdoped Ti O2(100)[J].Surface Science,1996,365(3):638-648.
[2]Du X L,Jiang Z,Su D S,et al.Research progress on the indirect hydrogenation of carbon dioxide to methanol[J].Chemsuschem,2016,9(4):322-332.
[3]Zhou X,Su T,Jiang Y,et al.Cu O-Fe2O3-Ce O2/HZSM-5bifunctional catalyst hydrogenated CO2for enhanced dimethyl ether synthesis[J].Chemical Engineering Science,2016,153:10-20.
[4]Fujiwara M,Satake T,Shiokawa K,et al.CO2hydrogenation for C2+hydrocarbon synthesis over composite catalyst using surface modified HB zeolite[J].Applied Catalysis B:Environmental,2015,179:37-43.
[5]Liu Rong(刘蓉),Wang Pengfei(王鹏飞),Zha Fei(查飞),et al.Preparation of rare earths modified SAPO-34 and its catalysis performance in synthesis of light olefins from CO2hydrogenation[J].Fine Chemicals(精细化工),2016,33(4):413-418.
[6]Inui T,Takeguchi T.Effective conversion of carbon dioxide and hydrogen to hydrocarbons[J].Catalysis Today,1991,10(1):95-106.
[7]Lin Q,Liu X Y,Jiang Y,et al.Crystal phase effects on the structure and performance of ruthenium nanoparticles for CO2hydrogenation[J].Catalysis Science&Technology,2014,4(7):2058-2063.
[8]Karelovic A,Ruiz P.CO2hydrogenation at low temperature over Rh/gamma-Al2O3catalysts:effect of the metal particle size on catalytic performances and reaction mechanism[J].Applied Catalysis B:Environmental,2012,113:237-249.
[9]Wang F,Li C,Zhang X,et al.Catalytic behavior of supported Ru nanoparticles on the{100},{110},and{111}facet of Ce O2[J].Journal of Catalysis,2015,329:177-186.
[10]Hetterley R D,Mackey R,Jones J T A,et al.One-step conversion of acetone to methyl isobutyl ketone over Pd-mixed oxide catalysts prepared from novel layered double hydroxides[J].Journal of Catalysis,2008,258(1):250-255.
[11]De la Osa A R,De Lucas A,Romero A,et al.Influence of the catalytic support on the industrial Fischer-Tropsch synthetic diesel production[J].Catalysis Today,2011,176(1):298-302.
[12]Munnik P,de Jongh P E,de Jong K P.Control and impact of the nanoscale distribution of supported cobalt particles used in Fischer-Tropsch catalysis[J].Journal of the American Chemical Society,2014,136(20):7333-7340.
[13]Zhou G,Wu T,Xie H,et al.Effects of structure on the carbon dioxide methanation performance of Co-based catalysts[J].International Journal of Hydrogen Energy,2013,38(24):10012-10018.
[14]Zhou G,Wu T,Zhang H,et al.Carbon dioxide methanation on ordered mesoporous Co/KIT-6 catalyst[J].Chemical Engineering Communications,2014,201(2):233-240.
[15]Khodakov A Y,Chu W,Fongarland P.Advances in the development of novel cobalt Fischer-Tropsch catalysts for synthesis of long-chain hydrocarbons and clean fuels[J].Chemical Reviews,2007,107(5):1692-1744.
[16]Qian Dong(钱东),Yan Zaoxue(闫早学),Shi Mao(石毛),et al.Sol-gel preparation and photocatalytic activities of Ti O2nanoparticles[J].The Chinese Journal of Nonferrous Metal(中国有色金属学报),2005,15(5):817-822.
[17]Eschemann T O,Bitter J H,de Jong K P.Effects of loading and synthesis method of titania-supported cobalt catalysts for FischerTropsch synthesis[J].Catalysis Today,2014,228:89-95.
[18]Samiee L,Shoghi F,Vinu A.Fabrication and electrocatalytic application of functionalized nanoporous carbon material with different transition metal oxides[J].Applied Surface Science,2013,265:214-221.
[19]Adelkhani H,Ghaemi M.Characterization of manganese dioxide electrodeposited by pulse and direct current for electrochemical capacitor[J].Journal Of Alloys and Compounds,2010,493(1):175-178.
[20]Shen H L,Hu H H,Liang D Y,et al.Effect of calcination temperature on the microstructure,crystallinity and photocatalytic activity of Ti O2hollow spheres[J].Journal of Alloys and Compounds,2012,542:32-36.
[21]Modak S,Ammar M,Mazaleyrat F,et al.XRD,HRTEM and magnetic properties of mixed spinel nanocrystalline Ni-Zn-Cu-ferrite[J].Journal of Alloys and Compounds,2009,473(1-2):15-19.
[22]Liu J,Li C,Wang F,et al.Enhanced low-temperature activity of CO2methanation over highly-dispersed Ni/Ti O2catalyst[J].Catalysis Science&Technology,2013,3(10):2627-2633.
[23]Khodakov A Y,Griboval-Constant A,Bechara R,et al.Pore size effects in Fischer-Tropsch synthesis over cobalt-supported mesoporous silicas[J].Journal of Catalysis,2002,206(2):230-241.
[24]Martínez A n,López C,Márquez F,et al.Fischer-Tropsch synthesis of hydrocarbons over mesoporous Co/SBA-15 catalysts:the influence of metal loading,cobalt precursor,and promoters[J].Journal of Catalysis,2003,220(2):486-499.
[25]Wang J A,Cuan A,Salmones J,et al.Studies of sol-gel Ti O2and Pt/Ti O2catalysts for NO reduction by CO in an oxygen-rich condition[J].Applied Surface Science,2004,230(1-4):94-105.
[26]Duvenhage D J,Coville N J.Fe:Co/Ti O2bimetallic catalysts for the Fischer-Tropsch reaction Part 2.The effect of calcination and reduction temperature[J].Applied Catalysis A:General,2002,233(1-2):63-75.
[27]Jacobs G,Das T K,Zhang Y Q,et al.Fischer-Tropsch synthesis:support,loading,and promoter effects on the reducibility of cobalt catalysts[J].Applied Catalysis A:General,2002,233(1-2):263-281.
[28]Rossetti I,Lasso J,Finocchio E,et al.Ti O2-supported catalysts for the steam reforming of ethanol[J].Applied Catalysis A:General,2014,477:42-53.
[29]Gao J,Hou Z,Guo J,et al.Catalytic conversion of methane and CO2to synthesis gas over a La2O3-modified Si O2supported Ni catalyst in fluidized-bed reactor[J].Catalysis Today,2008,131(1-4):278-284.
[30]Huang Wei(黄巍),Wang Jungang(王俊刚),Sun Zhiqiang(孙志强),et al.Effect of reduction temperature on performance of double mesoporous Co-based catalysts in Fischer-Tropsch synthesis[J].Journal of Fuel Chemistry and Technology(燃料化学学报),2014,42(1):81-86.
[31]Yin H,Chen J,Zhang J.Effects of calcination and reduction temperature on catalytic performance of Ni/Ti O2catalyst for hydrogenation of p-nitrophenol to p-animophenol[J].Chinese Journal of Catalysis,2007,28(5):435-440.
[32]Wierzbicki D,Debek R,Motak M,et al.Novel Ni-La-hydrotalcite derived catalysts for CO2methanation[J].Catalysis Communications,2016,83:5-8.
[33]Wierzbicki D,Baran R,Dbek R,et al.The influence of nickel content on the performance of hydrotalcite-derived catalysts in CO2methanation reaction[J/OL].International Journal of Hydrogen Energy,doi:10.1016/j.ijhydene.2017.02.148.
[34]Zhou R,Rui N,Fan Z,et al.Effect of the structure of Ni/Ti O2catalyst on CO2methanation[J].International Journal of Hydrogen Energy,2016,41(47):22017-22025.
[35]Fei Jinhua(费金华),Hou Zhaoyin(侯昭胤),Qi Gongxin(齐共新),et al.Methanation of carbon dioxide by hydrogenating over Ni supported on Al2O3catalysts[J].Chemical Journal of Chinese Universities(高等学校化学学报),2002,23(3):457-460.
[36]Thiessen J,Rose A,Meyer J,et al.Effects of manganese and reduction promoters on carbon nanotube supported cobalt catalysts in Fischer-Tropsch synthesis[J].Microporous and Mesoporous Materials,2012,164:199-206.
[37]Han C W,Majumdar P,Marinero E E,et al.Highly stable bimetallic Au-lr/Ti O2catalyst:physical origins of the intrinsic high stability against sintering[J].Nano Letters,2015,15(12):8141-8147.
[38]Hsieh B-J,Tsai M-C,Pan C-J,et al.Tuning metal support interactions enhances the activity and durability of Ti O2-supported Pt nanocatalysts[J].Electrochimica Acta,2017,224:452-459.
[39]Gao Y,Liang Y,Chambers S A.Thermal stability and the role of oxygen vacancy defects in strong metal support interaction-Pt on Nbdoped Ti O2(100)[J].Surface Science,1996,365(3):638-648.