Silylation of SiO2 and its influence on the properties of cobalt-based catalysts for Fischer-Tropsch synthesis
-
摘要: 利用甲硅烷基化作用制得了不同疏水程度的SiO2载体,采用等体积浸渍法制备了质量分数为5%的一系列负载型钴催化剂。结合FT-IR、29Si CP MAS NMR、BET、XRD、Raman、XPS和H2-TPR等表征手段,考察了SiO2甲硅烷基化对钴基催化剂物相结构、还原行为以及费-托合成催化性能的影响。催化剂在固定床反应器中,在p=2.0 MPa、t=240 ℃、n(H2)/n(CO)=2和GHSV=1 000 h-1的条件下进行评价。结果表明,随 SiO2 疏水程度的增加,钴催化剂的Co3O4晶粒长大且晶型趋于完整,钴硅相互作用减弱,还原度增加,催化剂的活性增强。Abstract: Silylated SiO2 with different hydrophobicities was prepared before the impregnation of cobalt precursor to obtain Co-based catalysts in Fischer-Tropsch synthesis. The effect of silylation on the crystallite structure and reduction behaviors of the resultant cobalt catalysts was investigated by FT-IR, 29Si CP MAS NMR, N2 sorption, XRD, Raman, XPS, and H2-TPR; their catalytic performance in Fischer-Tropsch synthesis was evaluated in a fixed-bed reactor under 2.0 MPa, 240 ℃, n(H2)/n(CO) ratio of 2, and space velocity (GHSV) of 1 000 h-1. The results indicated that compared with unsilylated SiO2, silylated SiO2 leads to larger and more perfect Co3O4 crystallite, weaker interaction between cobalt and silica, and higher reducibility; As a result, the activity of cobalt catalysts is enhanced and higher CO conversion is achieved for Fischer-Tropsch synthesis.
-
Key words:
- cobalt /
- SiO2 /
- silylation /
- hydrophobic /
- Fischer-Tropsch synthesis
-
KHODAKOV A Y, CHU W, FONGARLAND P. Advances in the development of novel cobalt Fischer-Tropsch catalysts for synthesis of long-chain hydrocarbons and clean fuels[J]. Chem Rev, 2007, 107(5): 1692-1744. LECKEL D. Diesel production from Fischer-Tropsch: The past, the present, and new concepts[J]. Energy Fuels, 2009, 23(5): 2342-2358. XIE R Y, LI D B, HOU B, WANG J G, JIA L T, SUN Y H. Silylated Co3O4-m-SiO2 catalysts for Fischer-Tropsch synthesis[J]. Catal Commun, 2011, 12(7): 589-592. DAVIS B H. Fischer-Tropsch synthesis: Comparison of performances of iron and cobalt catalysts[J]. Ind Eng Chem Res, 2007, 46(26): 8938-8945. KHODAKOV A Y. Fischer-Tropsch synthesis: Relations between structure of cobalt catalysts and their catalytic performance[J]. Catal Today, 2009, 144(3/4): 251-257. ZHANG J L, CHEN J G, REN J, LI Y W, SUN Y H. Support effect of Co/Al2O3 catalysts for Fischer-Tropsch synthesis[J]. Fuel, 2003, 82(5): 581-586. SAIB A M, CLAEYS M, van STEEN E. Silica supported cobalt Fischer-Tropsch catalysts: Effect of pore diameter of support[J]. Catal Today, 2002, 71(3/4): 395-402. PUSKAS I, FLEISCH T H, HALL J B, MEYERS B L, ROGINSKI R T. Metal-support interactions in precipitated, magnesium-promoted cobalt-silica catalysts[J]. J Catal, 1992, 34(2): 615-628. 银董红, 李文怀, 杨文书, 钟炳. 钴基催化剂在 Fischer-Tropsch 合成烃中的研究进展[J]. 化学进展, 2001, 13(2): 118-127. (YIN Dong-hong, LI Wen-huai, YANG Wen-shu, ZHONG Bing. Progress in cobalt-based catalysts in Fischer-Tropsch synthesis of Hydrocarbons[J]. Progress in Chemistry, 2001, 13(2): 118-127.) ZHANG J L, CHEN J G, REN J, SUN Y H. Chemical treatment of γ-Al2O3 and its influence on the propertiesof Co-based catalysts for Fischer-Tropsch synthesis[J]. Appl Catal A, 2003, 243(1): 121-133. KIM D J, DUNN B C, COLE P, TURPIN G, ERNST R D, PUGMIRE R J, KANG M, KIM J M, EYRING E M. Enhancement in the reducibility of cobalt oxides on a mesoporous silica supported cobalt catalyst[J]. Chem Commun, 2005, (11): 1462-1464. MARTNEZ A, PRIETO G. Breaking the dispersion-reducibility dependence in oxide-supported cobalt nanoparticles[J]. J Catal, 2007, 245(2): 470-476. SHAN Y Y, LIWE K Y, LI J L. Effect of silylation of SBA-15 on its supported cobalt catalysts for Fischer-Tropsch synthesis[J]. Chinese Journal of Catalysis, 2009, 30(11): 1091-1095. ZHANG Y, HANAYAMA K, TSUBAKI N. The surface modification effects of silica support by organic solvents for Fischer-Tropsch synthesis catalysts[J]. Catal Commun, 2006, 7(5): 251-254. ZHANG Y, LIU Y, YANG G H, SUN S L, TSUBAKI N. Effects of impregnation solvent on Co/SiO2 catalyst for Fischer-Tropsch synthesis: A highly active and stable catalyst with bimodal sized cobalt particles[J]. Appl Catal A, 2007, 321(1): 79-85. SHI L H, LI D B, HOU B, WANG Y L, SUN Y H. The modification of SiO2 by various organic groups and its influence on the properties of cobalt-based catalysts for Fischer-Tropsch synthesis[J]. Fuel Process Techno, 2010, 91(4): 394-398. SHI L H, LI D B, HOU B, SUN Y H. Organic modification of SiO2 and its influence on the properties of Co-based catalysts for Fischer-Tropsch synthesis[J]. Chin J Catal, 2007, 28(11): 999-1002. DUAN X L, YUAN D R, SUN Z H, SUN H Q, XU D, LV M K. Synthesis and characterization of ZnAl2O4/SiO2 nanocomposites by sol-gel method[J]. J Crystal Growth, 2003, 252(1/3): 4-8. LI G S, LI P L, SMITH R L, INOMATA H. Characterization of the dispersion process for NiFe2O4 nanocrystals in a silica matrix with infrared spectroscopy and electron paramagnetic resonance[J]. J Mol Struct, 2001, 560(1/3): 87-93. IZUTSU H, NAIR P K, KIYOZUMI Y, MIZWKAMI F. Structure and properties of TiO2-SiO2 prepared by sol-gel method in the presence of tartaric acid[J]. Mater Res Bull, 1997, 32(9): 1303-1311. RAO A V, WAGH P B, HARANATH D, RISBUD P P, KUMBHARE S D. Influence of temperature on the physical properties of TEOS silica xerogels[J]. Ceram Int, 1999, 25(6): 505-509. SHIMOJIMA A, UMEDA N, KURODA K. Synthesis of layered inorganic-organic nanocomposite films from mono-, di-, and trimethoxy(alkyl)silane-tetramethoxysilane systems[J]. Chem Mater, 2001, 13(10): 3610-3616. LIU Y H, LIN H P, MOU C Y. Direct method for surface silyl functionalization of mesoporous silica[J]. Langmuir, 2004, 20(8): 3231-3239. JIA M J, SEIFERT A, THIEL W R. Mesoporous MCM-41 materials modified with oxodiperoxo molybdenum complexes: Efficient catalysts for the epoxidation of cyclooctene[J]. Chem Mater, 2003, 15(11): 2174-2180. JONGSOMJIT B, WONGSALEE T, PRASERTHDAM P. Catalytic behaviors of mixed TiO2-SiO2-supported cobalt Fischer-Tropsch catalysts for carbon monoxide hydrogenation[J]. Mater Chem Phys, 2006, 97(2/3): 343-350. JONGSOMJIT B, PANPRANOT J, GOODWIN J G. ffect of zirconia-modified alumina on the properties of Co/γ-Al2O3 catalysts[J]. J Catal, 2003, 215(1): 66-77. JONGSOMJIT B, PANPRANOT J, GOODWIN J G. Co-support compound formation in alumina-supported cobalt catalysts[J]. J Catal, 2001, 204(1): 98-109. JONGSOMJIT B, SAKDAMNUSON C, PRASERTHDAM P. Dependence of crystalline phases in titania on catalytic properties during CO hydrogenation of Co/TiO2 catalysts[J]. Mater Chem Phys, 2005, 89(2/3): 395-401. SCHANKE D, VADA S, BLEKKAN E A, HILMEN A M, HOLMEN A. Study of Pt-promoted cobalt CO hydrogenation catalysts[J]. J Catal, 1995, 156(1): 85-95. ZHOU W, CHEN J G, FANG K G, SUN Y H. The deactivation of Co/SiO2 catalyst for Fischer-Tropsch synthesis at different ratios of H2 to CO[J]. Fuel Process Technol, 2006, 87(7): 609-616. RODRIGUES E L, BUENO J M C. Co/SiO2 catalysts for selective hydrogenation of crotonaldehyde: II Influence of the Co surface structure on selectivity[J]. Appl Catal A, 2002, 232(1/2): 147-158. REUEL R C, BARTHOLOMEW C H. Effects of support and dispersion on the CO hydrogenation activity/selectivity properties of cobalt[J]. J Catal, 1984, 85(1): 78-88.
点击查看大图
计量
- 文章访问数: 1329
- HTML全文浏览量: 21
- PDF下载量: 822
- 被引次数: 0