Studies on microwave-assisted synthesis of ZnFe-LDHs and their performance in oxidative dehydrogenation of isopentene
-
摘要: 以微波辅助合成系列ZnFe-LDHs并用于异戊烯氧化脱氢，借助其表面易于羟基化的性质降低水烯比。结果表明，微波法可明显缩短合成时间，在微波功率为600 W、微波温度为95 ℃和微波时间为1 h的条件下可获得结晶度和纯度较高的ZnFe-LDHs。与传统法相比，以其为前驱体获得的催化剂在异戊烯氧化脱氢中表现出更高的活性和选择性，水烯比为5.7时，异戊二烯收率达到52%，选择性达83%，明显降低了水烯比。Abstract: A series of ZnFe-LDHs were prepared via microwave-assisted co-precipitation method based on the structural properties of layered double hydroxides (LDHs) and the advantages of microwave-assisted synthesis and used for oxidative dehydrogenation of isopentene. The H2O/C5H10 molar ratio was lowered due to the easily hydroxylic surface. The results indicate that the microwave method can significantly shorten the synthesis time. ZnFe-LDHs with high crystallinity and purity were obtained at the microwave power of 600 W, microwave temperature of 95 ℃ and microwave time of 1 h. Compared with conventional method, the ZnFe-LDHs catalysts prepared with microwave method generated precursors exhibited higher activity and selectivity in oxidative dehydrogenation of isopentene. 52% yield of isoprene and 83% selectivity were achieved when the H2O/C5H10 molar ratio was 5.7, which was greatly lowered.
-
Key words:
- microwave /
- ZnFe-LDHs /
- hydroxylation /
- steam-to-olefin molar ratio
-
图 1 不同M2+/M3+合成ZnFe-LDHs及焙烧后的XRD谱图
Figure 1 XRD patterns of ZnFe-LDHs prepared with different M2+/M3+(a) and after calcination(b)
图 2 不同M2+/M3+合成ZnFe-LDHs的SEM照片
Figure 2 SEM images of ZnFe-LDHs prepared with different M2+/M3+
图 3 不同M2+/M3+常规法合成ZnFe-LDHs的XRD谱图和SEM照片
Figure 3 XRD and SEM spectra of conventionally prepared ZnFe-LDHs with different M2+/M3+
图 4 不同微波条件合成ZnFe-LDHs的XRD谱图
Figure 4 XRD patterns of ZnFe-LDHs prepared under different microwave conditions
图 5 不同微波条件合成ZnFe-LDHs的SEM照片
Figure 5 SEM images of ZnFe-LDHs prepared under different microwave conditions
(a): 600W-80-1 h; (b): 600W-95-1 h; (c): 900W-95-0.5 h
图 6 不同Zn/Fe比值合成ZnFe-LDHs的XRD谱图(M2+/M3+=6)
Figure 6 XRD patterns of ZnFe-LDHs prepared with different Zn/Fe molar ratios(M2+/M3+=6)
图 7 不同Zn/Fe比值合成ZnFe-LDHs的SEM照片(M2+/M3+=6)
Figure 7 SEM images of ZnFe-LDHs prepared with different Zn/Fe molar ratios(M2+/M3+=6)
(a): Zn/Fe=0.25; (b): Zn/Fe=0.4; (c): Zn/Fe=0.5; (d): Zn/Fe=0.75
图 8 温度对微波法合成ZnFe-LDHs焙烧后催化剂上异戊二烯收率和选择性的影响
Figure 8 Influence of temperature on the yield and selectivity of isoprene of microwave-assisted synthesized ZnFe-LDHs after calcination
—●—: 900W-95-0.25 h; —▲—: 600W-80-1 h; —▼—: 600W-95-1 h; —◆—: 600W-95-1 h(0.75)
图 9 温度对微波法合成ZnFe-LDHs焙烧后催化剂上COx选择性及残氧浓度的影响
Figure 9 Influence of temperature on the selectivity of COx and concentration of residual oxygen of microwave-assisted synthesized ZnFe-LDHs after calcination
—■—: ZnFe-600W-95-1 h-0.5; —●—: ZnFe-600W-95-1 h-0.75; —▲—: ZnFe-900W-95-0.25 h-0.5
图 10 氧烯比对ZnFe-MW-600W-95-1 h-0.5上异戊烯氧化脱氢反应的影响
Figure 10 Influence of oxygen/isopentene ratio on the reaction results of oxidative dehydrogenation of isopentene over ZnFe-MW-600W-95-1 h-0.5
图 11 空速对ZnFe-MW-600W-95-1 h-0.5上异戊烯氧化脱氢反应的影响
Figure 11 Influence of space velocity on the reaction results of oxidative dehydrogenation of isopentene over ZnFe-MW-600W-95-1 h-0.5
(t=390 ℃, O2:H2O:C5H10=0.95:5.7:1)
图 12 水烯比对ZnFe-MW-600W-95-1 h-0.5上异戊烯氧化脱氢反应的影响
Figure 12 Influence of steam/isopentene ratio on the reaction results of oxidative dehydrogenation of isopentene over ZnFe-MW-600W-95-1 h-0.5(O2:C5H10=0.95:1, WHSV=1.0 h-1)
—■—: conversion; —▲—: selectivity of isoprene; —●—: yield of isoprene
图 13 ZnFe-MW-600W-95-1 h-0.5上异戊烯氧化脱氢反应随时间的变化
Figure 13 Variation of reaction results of oxidative dehydrogenation of isopentene over ZnFe-MW-600W-95-1 h-0.5 (O2:H2O:C5H10=0.95:5.7:1, WHSV=1.0 h-1)
-
[1] MANNING H E. Oxidative dehydrogenation utilizing manganese ferrite: CN, 3671606[P], 1972-06-20. [2] CICHOWSKI R S. Oxidative dehydrogenation catalyst and process of preparation thereof: CN, 3862910[P]. 1975-01-28. [3] HOWON L, JUNG J C, KIM H. Oxidative dehydrogenation of n-butene to 1, 3-butadiene over sulfated ZnFe2O4 catalyst[J]. Catal Lett, 2009, 133: 321-327. doi: 10.1007/s10562-009-0195-5 [4] XU C L, GAO Y, LIU X H, Xin R R, WANG ZH. Hydrotalcite reconstructed by in situ rehydration as a highly active solid base catalyst and its application in aldol condensations[J]. RSC Adv, 2013, 3: 793-801. doi: 10.1039/C2RA21762G [5] TANASOI S, TANCHOUX N, URDA A, TICHIT D, SANDULESCU I, FAJULA F, MARCU I C. New Cu-based mixed oxides obtained from LDH precursors, catalysts for methane total oxidation[J]. Appl Catal A: Gen, 2009, 363: 135-142. doi: 10.1016/j.apcata.2009.05.007 [6] BAHRANOWSKI K, BUENO G, CORBERAN V C, KOOLI F, SERWICKA E M, VALENZUELA R X, WCISLO K. Oxidative dehydrogenation of propane over calcined vanadate-exchanged Mg, Al-layered double hydroxides[J]. Appl Catal A, 1999, 185: 65-73. doi: 10.1016/S0926-860X(99)00113-1 [7] YE X N, MA N, HUA W M, YUE Y H, MIAO C X, XIE Z K, GAO Z. Dehydrogenation of ethylbenzene in the presence of CO2 over catalysts prepared from hydrotalcite-like precursors[J]. J Mol Catal A: Chem, 2004, 217: 103-108. doi: 10.1016/j.molcata.2004.02.024 [8] SHEN J Y, GUANG B, TU M, CHEN Y. Preparation and characterization of Fe-MgO catalysts obtained from hydrotalcite-like compounds[J]. Catal Today, 1996, 30: 77-82. doi: 10.1016/0920-5861(95)00329-0 [9] ARAMENDIA M A, AVILES Y, BORAU V. Thermal decomposition of Mg/Al and Mg/Ga layered double hydroxides: a spectroscopic study[J]. J Mater Chem, 1999, 9: 1603-1607. doi: 10.1039/a900535h [10] VIAL S, PREVOT V, FORANO C. Novel route for layered double hydroxides preparation by enzymatic decomposition of urea[J]. J Phys Chem Solids, 2006, 67: 1048-1053. doi: 10.1016/j.jpcs.2006.01.024 [11] KANNAN S, VIR JASRA R. Microwave assisted rapid crystallization of Mg-M(Ⅲ) hydrotalcite where M(Ⅲ)=Al, Fe or Cr[J]. J Mater Chem, 2000, 10: 2311-2314. doi: 10.1039/b004219f [12] BENITO P, LABAJOS F M, ROCHA J, RIVES V. Influence of microwave radiation on the textural properties of layered double hydroxides[J]. Micropor Mesopor Mater, 2006, 94: 148-158. doi: 10.1016/j.micromeso.2006.03.038 [13] HONGO T, IEMURA T, YAMAZAKI A. Adsorption ability for several harmful anions and thermal behavior of Zn-Fe layered double hydroxide[J]. J Ceram Soc Jpn, 2008, 116: 192-197. doi: 10.2109/jcersj2.116.192 [14] PARIDA K M, MOHAPATRA L. Carbonate intercalated Zn/Fe layered double hydroxide: A novel photocatalyst for the enhanced photo degradation of azo dyes[J]. Chem Eng J, 2012, 179: 131-139. doi: 10.1016/j.cej.2011.10.070 [15] SEFTEL E M, COOL P, LUTIC D. Mg-Al and Zn-Fe layered double hydroxides used for organic species storage and controlled release[J]. Mater Sci Eng C, 2013, 33: 5071-5078. doi: 10.1016/j.msec.2013.08.041 [16] FETTER G, BOTELLO A, LARA V H, BOSCH P. Detrital Mg(OH)2 and Al(OH)3 in microwaved hydrotalcites[J]. J Porous Mater, 2001, 8: 227-232. doi: 10.1023/A:1012292807651 [17] GUO K, DUAN W ZH, WANG X D, WU Y, WANG H. Microwave assisted synthesis of ethylene glycol intercalated nickel aluminumlayered double hydroxides[J]. Chin J Appl Chem, 2016, 33: 84-91. http://yyhx.ciac.jl.cn/EN/Y2016/V33/I1/84 [18] LIAW B J, CHENG D S, YANG B L. Oxidative dehydrogenation of 1-butene on iron oxyhydroxides and hydrated iron oxides[J]. J Catal, 1989, 118: 312-326. doi: 10.1016/0021-9517(89)90320-5 [19] LIAW B J, CHENG D S, LEE S B. Effect of steam on the oxidative dehydrogenation of butene over magnesium ferrites with and without chromium substitution[J]. Appl Catal, 1991, 70: 161-173. doi: 10.1016/S0166-9834(00)84161-5 [20] MCINTYRE N S, ZETARUK D G. X-ray photoelectron spectroscopic studies of iron oxides[J]. Anal Chem, 1997, 49: 1521-1529. doi: 10.1021/ac50019a016 [21] CHEN B H, MA Y S, DING L B, XU L S, WU Z F, YUAN Q, HUANG W X. Reactivity of hydroxyls and water on a CeO2(111) thin film surface: the role of oxygen vacancy[J]. J Phys Chem C, 2013, 117: 5800-5810. doi: 10.1021/jp312406f -
下载:
点击查看大图
计量
- 文章访问数: 87
- HTML全文浏览量: 41
- PDF下载量: 9
- 被引次数: 0
