氨铜比对蒸氨法Cu/SiO_2催化剂活性组分演变及二氧化碳加氢性能的影响
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摘要
铜催化剂表面铜活性物种的性质与分散度是影响CO_2加氢性能的关键因素。以硅溶胶为载体、铜氨络合物为铜源采用蒸氨法制备了Cu/SiO_2催化剂考察了氨铜比对Cu/SiO_2催化剂表面铜活性物种的形成和CO_2加氢制甲醇反应性能的影响。通过N_2-physisorption、TEM、XRD、IR和BET等技术对催化剂的结构和性质进行了表征。结果显示,铜氨溶液中适当的氨浓度,有利于铜氨配体的形成和蒸氨过程中铜活性组分的均匀分布,有利于层状硅酸铜和氧化铜双活性组分的形成。在反应温度523 K,反应压力2.5 MPa,进气比V(CO_2):V(H_2):V(N_2)=10:30:4,反应空速1800 mL_(STP)/(g·h)的条件下,氨铜比为4的Cu/SiO_2-N4催化剂获得较优CO_2加氢催化性能,CO_2的转化率31%,CH_3OH的选择性54.8%,CH_3OH的收率17%。
The nature and distribution of surface copper active species on the copper based catalysts are crucial for the catalytic hydrogenation of CO_2 to methanol. Silica supported copper catalyst Cu/SiO_2 was prepared by ammonia evaporation(AE) method with different ammonia-copper molar ratio and characterized by N2-physisorption,TEM,XRD,IR and BET techniques. Performance of the Cu/SiO_2 catalysts on the hydrogenation of CO_2 reaction was also evaluated with a feed gas ratio of V(CO_2) ∶ V(H_2) ∶ V(N2) =10∶ 30∶ 4under 523 K,2. 5 MPa. The results indicated that the ammonia-copper molar ratio in the AE method exerted profound effects on the copper loading,texture properties and surface composition of the Cu/SiO_2 catalysts.Catalysts with the proper copper loading,smaller copper particle size,larger metallic copper surface area and good dispersion of copper species could be obtained by using a proper ammonia-copper molar ratio. The Cu/SiO_2-N4 catalyst with an optimal ratio of ammonia to copper of 4 can achieve CO_2 conversion of 31%,CH_3OH selectivity of 54. 8% and CH_3OH yield of 17% under the above condition.
The nature and distribution of surface copper active species on the copper based catalysts are crucial for the catalytic hydrogenation of CO_2 to methanol. Silica supported copper catalyst Cu/SiO_2 was prepared by ammonia evaporation(AE) method with different ammonia-copper molar ratio and characterized by N2-physisorption,TEM,XRD,IR and BET techniques. Performance of the Cu/SiO_2 catalysts on the hydrogenation of CO_2 reaction was also evaluated with a feed gas ratio of V(CO_2) ∶ V(H_2) ∶ V(N2) =10∶ 30∶ 4under 523 K,2. 5 MPa. The results indicated that the ammonia-copper molar ratio in the AE method exerted profound effects on the copper loading,texture properties and surface composition of the Cu/SiO_2 catalysts.Catalysts with the proper copper loading,smaller copper particle size,larger metallic copper surface area and good dispersion of copper species could be obtained by using a proper ammonia-copper molar ratio. The Cu/SiO_2-N4 catalyst with an optimal ratio of ammonia to copper of 4 can achieve CO_2 conversion of 31%,CH_3OH selectivity of 54. 8% and CH_3OH yield of 17% under the above condition.
引文
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[7]齐共新.CO2催化加氢合成醇、醚等含氧化合物的Cu基催化剂及其机理研究[D].杭州:浙江大学,2001.
[8]Kusama H,Okabe K,Sayama K,et al.Alcohol synthesis by catalytic hydrogenation of CO2over Rh-Co/Si O2[J].Applied Organometallic Chemistry,2000,14(12):836-840.
[9]Marc D Porosoff,Jingguang G Chen.Trends in the catalytic reduction of CO2by hydrogen over supported monometallic and bimetallic catalysts[J].Journal of Catalysis,2013,301:30-37.
[10]Brown N J,Weiner J,Hellgardt K,et al.Phosphinate stabilised Zn O and Cu colloidal nanocatalysts for CO2hydrogenation to methanol[J].Chemical Communications,2013,49(94):11074-11076.
[11]王丹君,陶芙蓉,赵华华,等.Cu/Zn O/Al2O3催化剂的共沉淀-蒸氨法制备及其对二氧化碳加氢制甲醇的研究[J].分子催化,2011(2):124-129.
[12]郭园园.二氧化碳加氢合成甲醇Cu/Zr O2/CNTs催化剂的研究[D].广州:华南理工大学,2013.
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[14]Hong Zhongshan,Cao Yong,Deng Jingfa,et al.CO2hydrogenation to methanol over Cu/Zn O/Al2O3catalysts prepared by a novel gel-network-coprecipitation method[J].Catalysis Letters,2002,82(1/2):37-44.
[15]Yue Hairong,Zhao Yujun,Zhao Shuo,et al.A copperphyllosilicate core-sheath nanoreactor for carbon-oxygen hydrogenolysis reactions[J].Nature Communications,2013(4):2339-2346.
[16]杨文龙,赵玉军,王胜平,等.铜硅催化剂中层状硅酸铜的形成过程[J].化学工业与工程,2016,33(1):1-5.
[17]Toupance T,Kermarec M,Lambert J F,et al.Conditions of formation of copper phyllosilicates in silica-supported copper catalysts prepared by selective adsorption[J].Journal of Physical Chemistry B,2002,106(9):2277-2286.
[18]Gong J,Yue H,Zhao Y,et al.Synthesis of ethanol via syngas on Cu/Si O2catalysts with balanced Cu0-Cu+sites[J].J Am Chem Soc,2012,134(34):13922-13925.