Influence of reduction-oxidation pretreatment on the performance of bi-modal structure Co-based catalysts in Fischer-Tropsch synthesis
-
摘要: 以双介孔分布MCM-41分子筛为载体,采用等体积浸渍法制备了钴基催化剂,并考察了还原-氧化预处理方式对催化剂结构及费托合成催化性能的影响。新鲜催化剂经预处理之后,XRD结果显示钴物种主要以单质钴形式存在,且主要以面心立方钴晶型出现,晶粒粒径由原来的8.4nm增加到22.6nm,由于晶粒粒径的增大,拉曼峰呈现蓝移特征。SEM及TEM表征表明,预处理后催化剂中钴物种在载体中有较好的分散性。H2-TPR结果表明,新鲜催化剂经还原-氧化预处理后钴物种的还原温度降低,钴物种-载体间作用力增强。费托合成反应结果显示,经预处理后催化剂较新鲜催化剂活性低,甲烷选择性提高,但C5~18的选择性明显提高,尤其是C5~11的选择性可达到新鲜催化剂的两倍。Abstract: Co-based catalyst supported on bi-modal MCM-41 molecular sieves was prepared by incipient-wetness impregnation method; the influence of reduction and oxidation pretreatment on the catalyst structure and its performance in Fischer-Tropsch synthesis (FTS) was investigated. XRD results showed that the cobalt species in the catalyst after the pretreatment is in the form of metal cobalt with face centered cubic crystal phase and the crystallite size is increased from 8.4nm to 22.6nm, compared with the untreated one; due to the increase of crystallite size, the Raman characteristic peak shows a blue shift. SEM and TEM results indicated that the cobalt species exhibits good dispersibility. H2-TPR results indicated that the reduction temperature is reduced and the interaction between metal and support is strengthened after the pretreatment. As a result, the pretreated-catalyst exhibits lower FTS activity and higher selectivity to methane than the fresh catalyst; however, the selectivity to C5~18 products over the pretreated-catalyst is improved obviously, especially, the selectivity to C5~11, which is about twice as that over the untreated one.
-
Key words:
- bi-modal structure /
- MCM41 /
- Co-based catalyst /
- pretreatment /
- Fischer-Tropsch synthesis
-
王野, 康金灿, 张庆红. 费托合成催化剂的研究进展[J]. 石油化工, 2009, 38(12): 1255-1263. (WANG Ye, KANG Jin-can, ZHANG Qing-hong, Research advances in catalysts for Fischer-Tropsch synthesis[J]. Petrochemical Technology, 2009, 38(12): 1255-1263.) JONGSOMJIT B, GOODWIN J G. Co-support compound formation in Co/Al2O3 catalysts: Effect of reduction gas containing CO[J]. Catal Today, 2002, 77(3): 191-204. NOWICKI L, OLEWSKI T, BEDYK T, LEDAKOWICZ S. Effect of reduction conditions on the performance of the Cs-Cu/ZnO catalyst in the reaction of synthesis of higher aliphatic alcohols from synthesis gas[J]. Inzynieria Chemiczna I Procesowa, 2006, 27(1): 163-175. KOBYLINSKI T P, KIBBY C L, PANNELL R B, EDDY E G. Synthesis gas conversion using ROR-activated catalyst: US, 4605676. 1986-08-12. HUSSAIN S T, LARACHI F. Surface modification of supported Ru: Mn/SiO2 Fischer-Tropsch synthesis catalysts[J]. J Trace Microprobe Tech, 2002, 20(2): 197-209. 贾丽涛, 房克功, 陈建刚, 孙予罕. 预处理气氛对Co-ZrO2共沉淀催化剂结构的影响[J]. 物理化学学报, 2006, 22(11): 1404-1408. (JIA Li-tao, FANG Ke-gong, CHEN Jian-gang, SUN Yu-han. Effect of pretreatment atmospheres on the structure of the Co-ZrO2 catalyst prepared by precipitation method[J]. Acta Physico-Chimica Sinica, 2006, 22(11): 1404-1408.) 穆仕芳, 李德宝, 侯博, 贾丽涛, 陈建刚, 孙予罕. 一次还原气氛对还原-氧化-还原预处理Co/SiO2催化剂费托合成反应性能的影响[J]. 石油化工, 2009, 38(11): 1158-1163. (MU Shi-fang, LI De-bao, HOU Bo, JIA Li-tao, CHEN Jian-gang, SUN Yu-han. Effect of first reduction atmosphere on activity of reduction-oxidation-reduction activated Co/SiO2 catalyst for Fischer-Tropsch synthesis[J]. Petrochemical Technology, 2009, 38(11): 1158-1163.) 张俊岭, 陈建刚, 任杰, 孙予罕. 钴基F-T合成重质烃催化剂载体效应的研究[J]. 催化学报, 2001, 22(3): 275-278. (ZHANG Jun-lin, CHEN Jian-gang, REN Jie, SUN Yu-han. Studies of support effect of heavy hydrocarbon catalysts for Co-based Fischer-Tropsch synthesis[J]. Chinese Journal of Catalysis, 2001, 22(3): 275-278.) XIONG H, ZHANG Y, LIEW K, LI J. Fischer–Tropsch synthesis: The role of pore size for Co/SBA-15 catalysts[J]. J Mol Catal A, 2008, 295(1/2): 68-76. WANG S, ZHANG J, JIANG J. Porous ceria hollow microspheres: Synthesis and characterization[J]. Microporous Mesoporous Mater, 2009, 123(1/3): 349-353. PRIETO G, MARTÍNEZ A, MURCIANOA R. Cobalt supported on morphologically tailored SBA-15 mesostructures: The impact of pore length on metal dispersion and catalytic activity in the Fischer-Tropsch synthesis[J]. Appl Catal A, 2009, 367(1/2): 146-156. WANG H, WAN Y. Synthesis of ordered mesoporous Pd/carbon catalyst with bimodal pores and its application in water-mediated Ullmann coupling reaction of chlorobenzene[J]. J Mater Sci, 2009, 44(24): 6553-6562. JOB N, PEREIRA M F R, LAMBERT S. Highly dispersed platinum catalysts prepared by impregnation of texture-tailored carbon xerogels[J]. J Catal, 2006, 240(2): 160-171. SHINODA M, ZHANG Y, YONEYAMA Y. New bimodal pore catalysts for Fischer–Tropsch synthesis[J]. Fuel Process Technol, 2004, 86(1): 73-85. LI J, XU Y, WU D, SUN Y. Hollow mesoporous silica sphere supported cobalt catalysts for F-T synthesis[J]. Catal Today, 2009, 148(1/2): 148-152. XU C Y, ZHANG P X, YAN L. Blue shift of Raman peak from coated TiO2 nanoparticles[J]. J Raman Spectroscopy, 2001, 32(10): 862-865. ZHOU H, CHEN L, MALIK V, KNIES C, HOFMANN D M. Raman studies of ZnO: Co thin films[J]. Physica Status Solidi (a), 2007, 204(1): 112-117. Van STEEN E, SEWELL G S, MAKHOTHE R A, MIKELETHWAITE C, MANSTEIN H, de LANGE M ,OCONNOR C T. TPR study on the preparation of impregnated Co/SiO2 catalysts[J]. J Catal, 1996, 162(2): 220-229. 杨文书, 房鼎业, 相宏伟, 李永旺, 刘继森. Co/HMS和Co/SiO2催化剂的表征及在费-托合成反应中的催化性能[J]. 催化学报, 2005, 26(4): 329-334. (YANG Wen-shu, FANG Ding-ye, Xiang Hong-wei, LI Yong-wang, LIU Ji-sen, Characterization and catalytic performance of Co/HMS and Co/SiO2 catalysts for Fischer-Tropsch synthesis[J]. Chinese Journal of Catalysis, 2005, 26(4): 329~334.)
点击查看大图
计量
- 文章访问数: 1343
- HTML全文浏览量: 27
- PDF下载量: 791
- 被引次数: 0