CuO含量对Pd/Al_2O_3催化剂乙醇氧化性能的影响
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摘要
采用浸渍法制备了一系列具有不同CuO含量的Pd-CuO/Al_2O_3催化剂,并将其用于乙醇氧化反应,其结构与性质通过XRD、H2-TPR和NH_3-TPD等手段进行分析。结果发现,催化剂的活性并不是随着CuO含量的增加而增强,Pd-1.0%CuO/Al_2O_3催化剂表现出最佳的活性,其点火温度和完全转化温度比Pd/Al_2O_3催化剂至少降低了50℃。与Pd/Al_2O_3催化剂相比,含CuO催化剂增强的衍射峰强度以及氢化钯分解峰的消失,说明Pd-Cu合金结构的形成有利于Pd、Cu物种之间的协同作用。对于Pd-1.0%CuO/Al_2O_3催化剂来说,还原峰向低温的移动以及还原峰面积的增大说明该催化剂上氧化性物质更易被还原且数量在增加,这对于氧化反应是十分有利的,新出现的还原峰表示Pd、Cu的相互作用生成了新物种。NH_3-TPD结果中更高含量的低温酸有利于高活性,而且新出现的脱附峰说明形成了新的酸性位点。
A series of Pd/Al_2O_3-CuO catalysts with different CuO contents were prepared by impregnation method. The catalysts were then used in the ethanol oxidation reaction and their structures and properties were investigated by using XRD, H2-TPR and NH_3-TPD techniques. The results showed that thereactivity was not always enhanced with the increase of CuO contents. The Pd-1.0%CuO/Al_2O_3 catalystshowed the best performance whose T50 and T90decreased more than 50℃ in comparison with Pd/Al_2O_3.Compared to Pd/Al_2O_3 catalyst, catalysts with CuO showed an enhancement in diffraction peak intensity but no decomposition of palladium hydride, indicating that the Pd-Cu alloy structure was formed leadingto the synergistic effect between Pd and Cu species. For Pd-1.0%CuO/Al_2O_3, the shift of reduction peak tolow temperatures and the increase in area demonstrated the reduction of the oxidizing substances on thecatalyst and the amount of them was increased which was beneficial to the oxidation reaction. The newreduction peak illustrated that the interaction between Pd and Cu had produced some new species. NH_3-TPD results showed the high content of low temperature acid was conducive to the high reactivity and the new desorption peak indicated that new acidic sites were formed on the Pd-1.0%CuO/Al_2O_3 catalyst.
A series of Pd/Al_2O_3-CuO catalysts with different CuO contents were prepared by impregnation method. The catalysts were then used in the ethanol oxidation reaction and their structures and properties were investigated by using XRD, H2-TPR and NH_3-TPD techniques. The results showed that thereactivity was not always enhanced with the increase of CuO contents. The Pd-1.0%CuO/Al_2O_3 catalystshowed the best performance whose T50 and T90decreased more than 50℃ in comparison with Pd/Al_2O_3.Compared to Pd/Al_2O_3 catalyst, catalysts with CuO showed an enhancement in diffraction peak intensity but no decomposition of palladium hydride, indicating that the Pd-Cu alloy structure was formed leadingto the synergistic effect between Pd and Cu species. For Pd-1.0%CuO/Al_2O_3, the shift of reduction peak tolow temperatures and the increase in area demonstrated the reduction of the oxidizing substances on thecatalyst and the amount of them was increased which was beneficial to the oxidation reaction. The newreduction peak illustrated that the interaction between Pd and Cu had produced some new species. NH_3-TPD results showed the high content of low temperature acid was conducive to the high reactivity and the new desorption peak indicated that new acidic sites were formed on the Pd-1.0%CuO/Al_2O_3 catalyst.
引文
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[18] UMAR A, ALSHAHRANI A A, ALGARNI H, et al. CuOnanosheets as potential scaffolds for gas sensing applications[J].Sensors&Actuators B:Chemical, 2017, 250:24-31.
[19] LOU X R, LIU P F, LI J, et al. Effects of calcination temperatureon Mn species and catalytic activities of Mn/ZSM-5 catalyst forselective catalytic reduction of NO with ammonia[J]. AppliedSurface Science, 2014, 307:382-387.
[20] SANJA P, VLADIMIR S, TAMáS V, et al. Diversity of Pd-Cuactive sites supported on pristine carbon nanotubes in terms ofwater denitration structure sensitivity[J]. Applied Catalysis A:General, 2018, 559:187-194.
[21] LIU W W, FENG Y S, WANG G Y, et al. Characterization and reactivity ofγ-Al2O3supported Pd-Cu bimetallic nanocatalysts forthe selective oxygenization of cyclopentene[J]. Chinese ChemicalLetters, 2016, 27:905-909.
[22] ZHOU R X, ZHAO B, YUE B H. Effects of CeO2-ZrO2present in Pd/Al2O3catalysts on the redox behavior of PdOx and their combustionactivity[J]. Applied Surface Science, 2008, 254(15):4701-4707.
[23] MOLENBROEK A M, HAUKKA S, CLAUSEN B S. Alloying in Cu/Pdnanoparticle catalysts[J]. Journal of Physical Chemistry B, 1998, 102(52):10680-10689.
[24] BATISTA J, PINTAR A, MANDRINO D, et al. XPS and TPRexaminations ofγalumina-supported Pd-Cu catalysts[J]. AppliedCatalysis A:General, 2001, 206(1):113-124.
[25] ZHANG Z X, JIANG Z, SHANGGUAN W F. Low-temperaturecatalysis for VOCs removal in technology and application:a state-of-the-art review[J]. Catalysis Today, 2016, 264:270-278.
[26] LIOTTA L F. Catalytic oxidation of volatile organic compounds onsupported noble metals[J]. Applied Catalysis B:Environmental, 2010,100(3/4):403-412.
[27] DAVIS J L, BARTEAU M A. The influence of oxygen on the selectivityof alcohol conversion on the Pd(111)surface[J]. Surface Science, 1988,197(1):123-152.-
[2]张桂芹,姜德超,李曼,等.城市大气挥发性有机物排放源及来源解析[J].环境科学与技术, 2014, 37(120):195-200.ZHANG Guiqin, JIANG Dechao, LI Man, et al. Emission sourcesand analytical sources of volatile organic compounds in urbanatmospheric[J]. Environmental Science&Technology, 2014, 37(120):195-200.
[3] MIRZAEI A, LEONARDI S G, NERI G. Detection of hazardousvolatile organic compounds(VOCs)by metal oxide nanostructures-based gas sensors:a review[J]. Ceramics International, 2016, 42(14):15119-15141.
[4]李振宇,李顶杰,黄格省,等.燃料乙醇发展现状及思考[J].化工进展, 2013, 32(7):1457-1467.LI Zhenyu, LI Dingjie, HUANG Gesheng, et al. Insights oncurrent development of fuel ethanol[J]. Chemical Industry andEngineering Progress, 2013, 32(7):1457-1467.
[5] RINTRAMEE K, KARIN F, RUPPRECHTER G, et al. Ethanoladsorption and oxidation on bimetallic catalysts containingplatinum and base metal oxide supported on MCM-41[J]. AppliedCatalysis B:Environmental, 2012, 115/116:225-235.
[6] LI H J, QI G S, TANA, et al. Low-temperature oxidation ofethanol over a Mn0.6Ce0.4O2mixed oxide[J]. Applied Catalysis B:Environmental, 2011, 103(1/2):54-61.
[7]彭雨程,王恒,冯俊小,等.催化燃烧技术处理VOCs的研究进展[J].环境与可持续发展, 2015, 40(3):97-100.PENG Yucheng, WANG Heng, FENG Junxiao, et al. Latestresearches of catalytic combustion of removing VOCs[J].Environment and Sustainable Development, 2015, 40(3):97-100.
[8] TSOU J, MAGNOUX P, GUISNET M, et al. Catalytic oxidation ofvolatile organic compounds:oxidation of methyl-isobutyl-ketoneover Pt/zeolite catalysts[J]. Applied Catalysis B:Environmental,2005, 57(2):117-123.
[9] GARCIA T, AGOURAM S, SáNCHEZ-ROYO J F, et al. Deepoxidation of volatile organic compounds using ordered cobaltoxides prepared by a nanocasting route[J]. Applied Catalysis A:General, 2010, 386(1/2):16-27.
[10] ZHENG G, HOHN K L. Catalytic oxidation of methanol onnanoscale copper oxide and nickel oxide[J]. Industrial&Engineering Chemistry Research, 2004, 43(1):30-35.
[11] MERGLER Y J, AALST A V, DELFT J V, et al. CO oxidation overpromoted Pt catalysts[J]. Applied Catalysis B:Environmental,1996, 10(4):245-261.
[12] FERNáNDEZ G M, MARTI A A, BELVER C, et al. Behavior ofpalladium-copper catalysts for CO and NO elimination[J]. Journalof Catalysis, 2000, 190(2):387-395.
[13] TIDAHY H L, SIFFERT S, WYRWALSKI F, et al. Catalyticactivity of copper and palladium based catalysts for toluene totaloxidation[J]. Catalysis Today, 2007, 119(1-4):317-320.
[14] GüNTER M M, RESSLER T, JENTOFT R E, et al. Redoxbehavior of copper oxide/zinc oxide catalysts in the steamreforming of methanol studied by in situ X-ray diffraction andabsorption spectroscopy[J]. Journal of Catalysis, 2001, 203(1):133-149.
[15] RAJESH H, OZKAN U S. Complete oxidation of ethanol,acetaldehyde and ethanol/methanol mixtures over copper oxide and copper-chromium oxide catalysts[J]. Industrial&EngineeringChemistry Research, 1993, 32(8):1622-1630.
[16] LI W W, QIANG Z M, ZHANG T, et al. Efficient degradation ofpyruvic acid in water by catalytic ozonation with PdO/CeO2[J].Journal of Molecular Catalysis A:Chemical, 2011, 348(1/2):70-76.
[17] HUANG S Y, ZHANG C B, HE H. Complete oxidation of o-xylene over Pd/Al2O3catalyst at low temperature[J]. CatalysisToday, 2008, 139(1/2):15-23.
[18] UMAR A, ALSHAHRANI A A, ALGARNI H, et al. CuOnanosheets as potential scaffolds for gas sensing applications[J].Sensors&Actuators B:Chemical, 2017, 250:24-31.
[19] LOU X R, LIU P F, LI J, et al. Effects of calcination temperatureon Mn species and catalytic activities of Mn/ZSM-5 catalyst forselective catalytic reduction of NO with ammonia[J]. AppliedSurface Science, 2014, 307:382-387.
[20] SANJA P, VLADIMIR S, TAMáS V, et al. Diversity of Pd-Cuactive sites supported on pristine carbon nanotubes in terms ofwater denitration structure sensitivity[J]. Applied Catalysis A:General, 2018, 559:187-194.
[21] LIU W W, FENG Y S, WANG G Y, et al. Characterization and reactivity ofγ-Al2O3supported Pd-Cu bimetallic nanocatalysts forthe selective oxygenization of cyclopentene[J]. Chinese ChemicalLetters, 2016, 27:905-909.
[22] ZHOU R X, ZHAO B, YUE B H. Effects of CeO2-ZrO2present in Pd/Al2O3catalysts on the redox behavior of PdOx and their combustionactivity[J]. Applied Surface Science, 2008, 254(15):4701-4707.
[23] MOLENBROEK A M, HAUKKA S, CLAUSEN B S. Alloying in Cu/Pdnanoparticle catalysts[J]. Journal of Physical Chemistry B, 1998, 102(52):10680-10689.
[24] BATISTA J, PINTAR A, MANDRINO D, et al. XPS and TPRexaminations ofγalumina-supported Pd-Cu catalysts[J]. AppliedCatalysis A:General, 2001, 206(1):113-124.
[25] ZHANG Z X, JIANG Z, SHANGGUAN W F. Low-temperaturecatalysis for VOCs removal in technology and application:a state-of-the-art review[J]. Catalysis Today, 2016, 264:270-278.
[26] LIOTTA L F. Catalytic oxidation of volatile organic compounds onsupported noble metals[J]. Applied Catalysis B:Environmental, 2010,100(3/4):403-412.
[27] DAVIS J L, BARTEAU M A. The influence of oxygen on the selectivityof alcohol conversion on the Pd(111)surface[J]. Surface Science, 1988,197(1):123-152.-