Preparation of plasma modified CuO/γ-Al2O3 catalyst and its catalytic performance in the combustion of low-concentration methane
-
摘要: 为了研究CuO/γ-Al2O3催化低浓度甲烷燃烧性能,采用普通浸渍法和低温等离子体改性的方法分别制备了CuO/γ-Al2O3和CuO/γ-Al2O3-P催化剂,并用于低浓度甲烷燃烧,考察了Cu负载量和等离子体改性工艺对其催化活性的影响。结果表明,Cu负载量为7%时,催化剂的活性最强。改性气体、气体空速、放电电压、放电频率、等离子体处理时间均是影响催化剂活性的因素。氧气适合用作催化剂的改性气体,而氮气不宜作为改性气体使用。氧气作为改性气体时,最佳的改性工艺条件为峰峰值电压45 kV、放电频率14.71 kHz、等离子体处理时间30 min、氧气空速20 mL/(min·g)。在此工艺条件下制备的催化剂用于低浓度甲烷催化燃烧,可使t10降低23 ℃、t50降低6 ℃、t90降低19 ℃,同时,可使反应的活化能由79.27 kJ/mol降低为76.12 kJ/mol。催化剂的SEM、BET、XRD、XPS、H2-TPR表征结果表明,等离子体对催化剂的改性作用主要在于增大了催化剂的比表面积、促使催化剂中Cu周围电子云密度降低及体相氧向表面氧迁移,从而利于甲烷在催化剂表面的吸附、活化和转化。Abstract: A series of CuO/γ-Al2O3 catalysts were prepared by conventional impregnation and then modified with low temperature plasma at atmospheric pressure in a dielectric barrier discharge (DBD) reactor. These modified catalysts were used in the catalytic combustion of low-concentration methane. The effects of Cu loading and plasma modification process on the activity of CuO/γ-Al2O3 catalyst were investigated. The results show that the catalytic activity is the best when the loading of Cu is 7%. Modification gas and its space velocity, discharge voltage, discharge frequency, plasma treatment time are the factors that affect the activity of the catalyst. O2 plasma treatment has effect on increasing the activity of CuO/γ-Al2O3 catalyst, and N2 plasma treatment reduces the catalytic activity. When oxygen as the modification gas, the optimum modification process conditions are 45 kV of the discharge voltage, 14.71 kHz of the discharge frequency, 30 min of the plasma treatment time, and 20 mL/(min·g) of the oxygen space velocity. The catalyst, which is modified under the above process conditions, exhibits excellent catalytic activity for the combustion of low-concentration methane. Using this catalyst, t10, t50 and t90 are decreased by 23, 6 and 19 ℃, respectively. Compared with the conventional CuO/γ-Al2O3 catalyst, the plasma modified CuO/γ-Al2O3 catalyst can depress the apparent activation energy of the catalytic combustion reaction of low-concentration methane from 79.27 to 76.12 kJ/mol. The parent and modified samples were characterized by diverse techniques including SEM, BET, XRD, XPS and H2-TPR. The results show that the O2 plasma can adjust specific surface area, the electron density around atom Cu and mobility of bulk phase oxygen of the catalyst, thereby affect the adsorption, activation and conversion of methane on the surface of the catalyst in the combustion of low-concentration methane.
-
Key words:
- CuO/γ-Al2O3 /
- plasma /
- catalyst /
- ventilation air methane /
- catalytic combustion /
- modification
-
表 1 不同催化剂的催化活性
Table 1 Catalytic activity of different catalyst
Catalyst t10/℃ t50/℃ t90/℃ 7%CuO/γ-Al2O3-P 377 466 531 7%CuO/γ-Al2O3 400 472 550 -
[1] 霍春秀, 李强.乏风瓦斯催化燃烧实验研究[J].矿业安全与环保, 2014, 41(4):1-3. doi: 10.3969/j.issn.1008-4495.2014.04.001HUO Chun-xiu, LI Qiang. Experimental study on catalytic combustion of ventilation air methane[J]. Min Saf Environ Prot, 2014, 41(4):1-3. doi: 10.3969/j.issn.1008-4495.2014.04.001 [2] 陈艳容, 李浩杰, 杨仲卿, 樊湖.超声改性的Cu/Al2O3-MgO催化剂结构及其超低浓度甲烷催化燃烧性能[J].燃料化学学报, 2015, 43(1):122-128. doi: 10.3969/j.issn.0253-2409.2015.01.019CHEN Yan-rong, LI Hao-jie, YANG Zhong-qing, FAN Hu. Structure of CuO/Al2O3-MgO catalyst modified by ultrasound assisted dispersion and its catalytic performance in the combustion of lean methane[J]. J Fuel Chem Technol, 2015, 43(1):122-128. doi: 10.3969/j.issn.0253-2409.2015.01.019 [3] 史兵兵, 江志东.低浓度甲烷催化燃烧La0.8Ca0.2FeO3/MgO蜂窝催化剂[J].天然气化工(C1化学与化工), 2013, 38(3):12-17. doi: 10.3969/j.issn.1001-9219.2013.03.003SHI Bing-bing, JIANG Zhi-dong. La0.8Ca0.2FeO3/MgO honeycombs for catalytic lean burn of methane[J]. Nat Gas Chem Ind, 2013, 38(3):12-17. doi: 10.3969/j.issn.1001-9219.2013.03.003 [4] 陈玉娟, 刘晓阳, 刘生玉, 张素红.矿井乏风低浓度甲烷CuO/Al2O3催化燃烧性能研究[J].中国煤炭, 2014, 40(7):126-130. doi: 10.3969/j.issn.1006-530X.2014.07.033CHEN Yu-juan, LIU Xiao-yang, LIU Sheng-yu, ZHANG Su-hong. Research of catalytic combustion performance of coal mine ventilation air with low concentration methane by CuO/Al2O3 catalyst[J]. Chin Coal, 2014, 40(7):126-130. doi: 10.3969/j.issn.1006-530X.2014.07.033 [5] 朱丽华, 徐锋, 崔宝君, 高宏亮.低温等离子体改性CuO/ZrO2催化剂上乏风瓦斯催化燃烧性能[J].煤炭学报, 2017, 42 http://xueshu.baidu.com/s?wd=paperuri%3A%286e70fff335c666af393503f62006fdb9%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fkns.cnki.net%2FKCMS%2Fdetail%2Fdetail.aspx%3Ffilename%3DMTXB2017S2013%26dbname%3DCJFD%26dbcode%3DCJFQ&ie=utf-8&sc_us=11348155167918765787S2):391-397. ZHU Li-hua, XU Feng, CUI Bao-jun, GAO Hong-liang. Catalytic combustion of ventilation air methane over CuO/ZrO2 catalyst modified by low temperature plasma[J]. J Chin Coal Soc, 2017, 42(S2):391-397. http://xueshu.baidu.com/s?wd=paperuri%3A%286e70fff335c666af393503f62006fdb9%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fkns.cnki.net%2FKCMS%2Fdetail%2Fdetail.aspx%3Ffilename%3DMTXB2017S2013%26dbname%3DCJFD%26dbcode%3DCJFQ&ie=utf-8&sc_us=11348155167918765787 [6] 朱丽华, 徐锋, 高宏亮, 崔宝君, 吴庆友.等离子体改性对CuO/ZrO2催化乏风瓦斯燃烧的影响[J].黑龙江科技大学学报, 2017, 27(4):443-447. doi: 10.3969/j.issn.2095-7262.2017.04.024ZHU Li-hua, XU Feng, GAO Hong-liang, CUI Bao-jun, WU Qing-you. Effect of plasma treatment on performance of CuO/ZrO2 catalyst in combustion of ventilation air methane[J]. J Heilongjiang Univ Sci Technol, 2017, 27(4):443-447. doi: 10.3969/j.issn.2095-7262.2017.04.024 [7] WARMUZINSKI K. Harnessing methane emissions from coal mining[J]. Process Saf Environ Prot, 2008, 86(5):315-320. doi: 10.1016/j.psep.2008.04.003 [8] SU S, CHEN H. Characteristics of coal mine ventilation air flows[J]. J Environ Manage, 2008, 86(1):44-62. doi: 10.1016-j.jenvman.2006.11.025/ [9] 刘欢, 梁文俊, 李坚, 王洪明, 何洪.乏风瓦斯流向变换催化燃烧试验研究[J].工业催化, 2013, 21(3):65-69. doi: 10.3969/j.issn.1008-1143.2013.03.013LIU Huan, LIANG Wen-jun, LI Jian, WANG Hong-ming, HE Hong. Experimental research on flow reverse catalytic combustion of ventilation air methane[J]. Ind Catal, 2013, 21(3):65-69. doi: 10.3969/j.issn.1008-1143.2013.03.013 [10] 刘文革, 郭德勇, 徐鑫, 刘建周, 段利叶.新型铜锰复合通风瓦斯甲烷氧化催化剂制备与活性研究[J].中国矿业大学学报, 2014, 43(5):887-904. http://d.old.wanfangdata.com.cn/Periodical/zgkydxxb201405018LIU Wen-ge, GUO De-yong, XU Xin, LIU Jian-zhou, DUN Li-ye. Synthesis and activity of novel Cu-Mn composite catalyst for ventilation air methane combustion[J]. J Chin Univ Min Technol, 2014, 43(5):887-904. http://d.old.wanfangdata.com.cn/Periodical/zgkydxxb201405018 [11] 徐鑫, 刘文革, 刘建周, 韩甲业, 范传凤. Pd/Zr/Al2O3风排瓦斯燃烧整体催化剂催化反应机理[J].煤炭学报, 2017, 42(3):659-664. http://xueshu.baidu.com/s?wd=paperuri%3A%283e82a03eca7468afb0c0168425b63ec0%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fkns.cnki.net%2FKCMS%2Fdetail%2Fdetail.aspx%3Ffilename%3DMTXB201703015%26dbname%3DCJFD%26dbcode%3DCJFQ&ie=utf-8&sc_us=14214366804071738595XU Xin, LIU Wen-ge, LIU Jian-zhou, HAN Jia-ye, FAN Chuan-feng. Catalytic reaction mechanism of Pd/Zr/Al2O3 catalyst for ventilation air methane combustion[J]. J Chin Coal Soc, 2017, 42(3):659-664. http://xueshu.baidu.com/s?wd=paperuri%3A%283e82a03eca7468afb0c0168425b63ec0%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fkns.cnki.net%2FKCMS%2Fdetail%2Fdetail.aspx%3Ffilename%3DMTXB201703015%26dbname%3DCJFD%26dbcode%3DCJFQ&ie=utf-8&sc_us=14214366804071738595 [12] 张力, 刘建军, 杨仲卿, 郑世伟.硫中毒对Cu/γ-Al2O3催化含硫低浓度甲烷燃烧特性的影响[J].燃料化学学报, 2014, 42(5):1-6. http://xueshu.baidu.com/s?wd=paperuri%3A%28223109e5453a76339a8ee1f928be989a%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fkns.cnki.net%2FKCMS%2Fdetail%2Fdetail.aspx%3Ffilename%3DRLHX201405019%26dbname%3DCJFD%26dbcode%3DCJFQ&ie=utf-8&sc_us=13761698783404621755ZHANG Li, LIU Jian-jun, YANG Zhong-qing, ZHENG Shi-wei. The effects of sulfur poisoning on combustion characteristics of low concentration methane with SO2 over Cu/γ-Al2O3catalysts[J]. J Fuel Chem Technol, 2014, 42(5):1-6. http://xueshu.baidu.com/s?wd=paperuri%3A%28223109e5453a76339a8ee1f928be989a%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fkns.cnki.net%2FKCMS%2Fdetail%2Fdetail.aspx%3Ffilename%3DRLHX201405019%26dbname%3DCJFD%26dbcode%3DCJFQ&ie=utf-8&sc_us=13761698783404621755 [13] 刘建军, 杨仲卿, 张力. Ni的引入对Cu/γ-Al2O3催化剂上含硫低浓度甲烷燃烧特性的影响[J].燃料化学学报, 2014, 42(10):1253-1258. doi: 10.3969/j.issn.0253-2409.2014.10.016LIU Jian-jun, YANG Zhong-qing, ZHANG Li. Effect of Ni addition on the catalytic performance of Cu/γ-Al2O3 in the combustion of lean methane containing SO2[J]. J Fuel Chem Technol, 2014, 42(10):1253-1258. doi: 10.3969/j.issn.0253-2409.2014.10.016 [14] YANG Z, GRACE J R. Combustion of low-concentration coal bed methane in a fluidized bed reactor[J]. Energy Fuels, 2011, 25(3):975-980. doi: 10.1021/ef101573y [15] 黄亮.非热等离子体促进甲烷活化转化的研究[D].杭州: 浙江大学, 2012.HUANG Liang. Study on activation and conversion of methane using non-thermal plasma[D]. Hangzhou: Zhejiang University, 2012. [16] 王月娟, 郭美娜, 鲁继青, 罗孟飞.介孔Al2O3负载PdO催化甲烷燃烧反应性能[J].催化学报, 2011, 39(9):1496-1501. http://d.old.wanfangdata.com.cn/Periodical/cuihuaxb201109010WANG Yue-juan, GUO Mei-na, LU Ji-qing, LUO Meng-fei. Mesoporous alumina supported PdO catalysts for catalytic combustion of methane[J]. Chin J Catal, 2011, 39(9):1496-1501. http://d.old.wanfangdata.com.cn/Periodical/cuihuaxb201109010 [17] 王海涛.甲烷部分氧化制合成气中等离子体对催化剂的改性研究[D].天津: 天津大学, 2004.WANG Hai-tao. Effect of low temperature plasma on catalyst during partial oxidation of methane to syngas[D]. Tianjin: Tianjin University, 2004. [18] FOIX M, GUYON C, TATOULIAN M, COSTA D. Study of the use of fluidized bed plasma reactors for the treatment of alumina supported palladium catalyst:Application for SCR NOx by CH4 in stationary sources[J]. Catal Commun, 2010, 12(1):20-24. [19] BELESSI V C, LADAVOS A K, POMONIS P J. Methane combustion on La-Sr-Ce-Fe-O mixed oxides:Bifunctional synergistic action of SrFeO3-x and CeOx phases[J]. Appl Catal B:Environ, 2001, 31(3):183-187. doi: 10.1016/S0926-3373(00)00279-4 [20] ABBASI R, WU L, WANKE S E. Kinetics of methane combustion over Pt and Pt-Pd catalysts[J]. Chem Eng Res Des, 2012, 90(11):1930-1942. doi: 10.1016/j.cherd.2012.03.003 [21] 张佳瑾, 李建伟, 朱吉钦, 王越, 陈标华.助剂对Cu-Mn复合氧化物整体式催化剂催化低浓度甲烷燃烧反应性能的影响[J].催化学报, 2011, 32(8):1380-1386. http://d.old.wanfangdata.com.cn/Periodical/cuihuaxb201108012ZHANG Jia-jin, LI Jian-wei, ZHU Ji-qin, WANG Yue, CHEN Biao-hua. Effect of promoter on the performance of Cu-Mn complex oxide monolithic catalysts for lean methane catalytic combustion[J]. Chin J Catal, 2011, 32(8):1380-1386. http://d.old.wanfangdata.com.cn/Periodical/cuihuaxb201108012