硅铝比对Cu-Co/ZSM-5-Al_2O_3催化剂性能的影响
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摘要
采用物理混合法制备了不同硅铝比的ZSM-5与Al_2O_3的混合载体,并采用浸渍法制备Cu-Co基催化剂,考查其对合成气制混合醇性能的影响,并用Ar物理吸-脱附、H2程序升温还原(H2-TPR)、X射线光电子能谱(XPS)等手段对其结构性能进行了表征。结果表明:当混合载体中ZSM-5硅铝比为50时,载体形成了新的孔道结构,有利于消除载体的堆积现象,促进载体活性物种的分散,更有利于表面活性物种的还原,同时改变了表面活性物中的化学状态,从而使合成气制备低碳混合醇具有较高的反应活性和选择性。在5.0MPa,300℃,V(H2)∶V(CO)∶V(N2)=4∶2∶1,GHSV=7200m L·h~(-1)反应条件下,不同硅铝比的混合载体催化剂表现出不同的催化活性,其中当混合载体中ZSM-5硅铝比为50时,CO转化率和C~(2+)醇类选择性分别达到21.31%和41.80%。
ZSM-5 zeolite with different Si/Al ratio and Al_2O_3 were used to prepare hybrid supported Cu-Co based catalysts.The properties of lower carbon mixed alcohols synthesis from syngas were studied. The textual and structural properties of the catalysts were studied using Ar physics-stripping in low temperature,H_2-temperature programmed reduction(H_2-TPR),X-ray photoelectron spectroscopy(XPS). The results indicate that when the hybrid supported with Si/Al ratio of 50 would form the new channel structure and beneficial to eliminate the phenomenon of the accumulation of carrier,the hybrid supported contributed to high metal dispersion,be beneficial to the reduction of surface active species,changed the chemical state of the surface activity at the same time,thus improve the conversion and selectivity of the reaction. In 5.0MPa,300℃,V(H_2)∶V(CO)∶V(N_2)=4∶2∶1,GHSV=7200m L·h~(-1) reaction conditions,hybrid supported catalysts with different Si/Al ratio showed different catalytic activity. When the Si/Al ratio of ZSM-5 zeolite to 50 of ZSM-5/Al_2O_3,the CO conversion was 21.31% and the C~(2+) alcohol selectivity was 41.80%.
ZSM-5 zeolite with different Si/Al ratio and Al_2O_3 were used to prepare hybrid supported Cu-Co based catalysts.The properties of lower carbon mixed alcohols synthesis from syngas were studied. The textual and structural properties of the catalysts were studied using Ar physics-stripping in low temperature,H_2-temperature programmed reduction(H_2-TPR),X-ray photoelectron spectroscopy(XPS). The results indicate that when the hybrid supported with Si/Al ratio of 50 would form the new channel structure and beneficial to eliminate the phenomenon of the accumulation of carrier,the hybrid supported contributed to high metal dispersion,be beneficial to the reduction of surface active species,changed the chemical state of the surface activity at the same time,thus improve the conversion and selectivity of the reaction. In 5.0MPa,300℃,V(H_2)∶V(CO)∶V(N_2)=4∶2∶1,GHSV=7200m L·h~(-1) reaction conditions,hybrid supported catalysts with different Si/Al ratio showed different catalytic activity. When the Si/Al ratio of ZSM-5 zeolite to 50 of ZSM-5/Al_2O_3,the CO conversion was 21.31% and the C~(2+) alcohol selectivity was 41.80%.
引文
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[5]Khodakov A Y,Zholobenko V L,Bechara R,et al.Impact of Aqueous Impregnation on the Long-range Ordering and Mesoporous Structure of Cobalt Containing MCM-41 and SBA-15 Materials[J].Microporous and Mesoporous Materials,2005,79(s1-3):29-39.
[6]WANG Jing-juan,Chernavskii P A,Khodakov A Y,et al.Structure and Catalytic Performance of Alumina-supported Copper Cobalt Catalysts for Carbon Monoxide Hydrogenation[J].Journal of Catalysis,2012,286(4):51-61.
[7]WANG Jing-juan,Chernavskii P A,WANG Ye,et al.Influence of the Support and Promotion on the Structure and Catalytic Performance of Copper-cobalt Catalysts for Carbon Monoxide Hydrogenation[J].Fuel,2013,103(1):1111-1122.
[8]WANG Zi,Spivey J J.Effect of Zr O2,Al2O3and La2O3on Cobalt Copper Catalysts for Higher Alcohols Synthesis[J].Applied Catalysis A General,2015,507:75-81.
[9]HE Ying-ping,LIU Min,DAI Cheng-yi,et al.Modification of Nanocry-stalline ZSM-5 Zeolite with Tetrapropylammonium Hydroxide and Its Catalytic Performance in Methanol to Gasoline Reaction[J].Chinese Journal of Catalysis,2013,34(6):1148-1158.
[10]F Jiao,J Li,X Pan,et al.Selective Conversion of Syngas to Light Olefins[J].Science,2016,351(6277):1065-1068.
[11]Cheng Kang,Gu Bang,Liu Xiao-liang,et al.Direct and Highly Selective Conversion of Synthesis Gas to Lower Olefins:Design of a Bifunctional Catalyst Combining Methanol Synthesis and Carbon-Carbon Coupling[J].Angewandte Chemie-International Edition,2016.
[12]王树国,吴东,孙予罕,等.Al MCM-48介孔分子筛的合成研究[J].燃料化学学报,2001,29(z1):26-27.
[13]Wang J J,Chernavskii P A,Khodakov A Y,et al.Structure and Catalytic Performance of Alumina-supported Copper-cobalt Catalysts for Carbon Monoxide Hydrogenation[J].Journal of Catalysis,2012,286(4):51-61.
[14]崔云鹤,铜钴硅催化剂上合成气制备低碳混合醇的研究[D].厦门大学,2012.
[15]Xu X D,Doesburg E B M,Scholten J J F.Synthesis of Higher Alcohols from Syngas-recently Patented Catalysts and Tentative Ideas on the Mechanism[J].Catalysis Today,1987,2(1):125-170.
[16]丁凡舒,聂小娃,刘民,等.Fe基催化剂上二氧化碳加氢制C2+烃的研究进展[J].应用化学,2016,33(2):123-132.
[17]王峰,任杰,李永旺.密度泛函法计算C-1-C-(14)正构烃生成焓及C-C键裂解能[J].应用化学,2009,26(12):114-118.