Effect of Na promoter and reducing atmosphere on phase evolution of Fe-based catalyst and its CO2 hydrogenation performance
-
摘要: 本研究使用原位X射线衍射(in-situ XRD)技术，对Na/Fe2O3样品的还原及活化过程进行了原位表征，探究了Na含量、预处理气氛对Fe基催化剂物相的影响，并研究了铁氧化合物与铁碳化合物在CO2加氢过程中的协同作用。结合H2-TPR、CO + H2-TPSR-MS手段对催化剂样品进行了物化性质表征。结果表明，还原气氛为H2时，Na助剂修饰会抑制Fe2O3催化剂还原；然而还原气氛为合成气(CO/H2 = 1∶2)时，适量Na助剂会降低还原和活化温度，提高碳化铁含量。采用H2和合成气分别对Fe基催化剂进行还原处理，低碳烯烃选择性由0.3%提高至20.2%，CO2转化率由7.3%提升至25.8%；与纯Fe2O3相比，Na修饰后催化剂Fe5C2含量从8.5%提高到38.4%，C5+选择性由7.8%提升至37.0%，CH4选择性从43.2%降至14.9%。催化剂通过调节还原气氛和Na助剂修饰量有效调控Fe3O4和Fe5C2物相比例，提升Fe基催化剂CO2加氢活性和产物选择性。
-
关键词:
- in-situ XRD /
- Fe基催化剂 /
- Na助剂 /
- 还原气氛 /
- 物相变化
Abstract: Although alkali metal promoters have a considerable effect on the product distribution of CO2 hydrogenation over Fe-based catalysts, the mechanism of the active phase transformation is uncertain. The effects of Na modification and pretreatment atmosphere on phase evolution of Fe2O3 sample and the synergistic effect between iron oxides and carbides were investigated using in-situ X-ray diffraction ( in-situ XRD). The physiochemical properties of catalyst were characterized by H2-TPR and CO+H2-TPSR-MS. When the reducing environment is H2, Na promoter inhibited the reduction of Fe2O3. However, when the reducing atmosphere is syngas (CO/H2 = 1:2), a suitable amount of Na promoter decreased the reduction and activation temperatures, and increased the iron carbide concentration. The selectivity of light olefins increased from 0.3% to 20.2%, and CO2 conversion increased from 7.3% to 25.8% when syngas was used as the reducing gas compared to using H2 as the reducing gas. Compared with pure Fe2O3, the CH4 selectivity of Na modified Fe2O3 decreased from 43.2% to 14.9%, while the selectivity of C5+ increased from 7.8% to 37.0%, owing to the fact that the Fe5C2 content increased from 8.5% to 38.4%. The ratio of Fe3O4 to Fe5C2 in the catalyst could be effectively controlled by changing the reducing atmosphere and the amount of Na promoter, thereby improving the CO2 hydrogenation activity and target product selectivity.-
Key words:
- in-situ XRD /
- Fe-based catalyst /
- Na-promoter /
- reducing atmosphere /
- phases evolution
-
图 1 Fe2O3样品的XRD谱图
Figure 1 XRD patterns of the Fe2O3 samples
a: Fe2O3; b: 1Na-Fe2O3; c: 2Na-Fe2O3
图 2 样品的H2-TPR谱图
Figure 2 H2-TPR profiles of the samples
a: Fe2O3; b: 1Na-Fe2O3; c: 2Na-Fe2O3
图 3 样品在H2气氛下还原的原位XRD谱图
Figure 3 In-situ XRD patterns of the samples under a H2 reduction atmosphere
(a): Fe2O3; (b): 1Na-Fe2O3; (c): 2Na-Fe2O3
图 4 样品在合成气气氛下还原的原位XRD谱图
Figure 4 In-situ XRD patterns of the samples under a H2 + CO (CO/H2 = 1∶2) reduction atmosphere
(a): Fe2O3; (b): 1Na-Fe2O3; (c): 2Na-Fe2O3
图 5 样品的CO + H2-TPSR-MS谱图
Figure 5 CO + H2-TPSR-MS profiles of the samples
(a): Fe2O3; (b): 1Na-Fe2O3; (c): 2Na-Fe2O3
图 6 催化剂CO2加氢反应性能
Figure 6 Catalytic performance of samples on CO2 hydrogenation
a: Fe2O3, (Pretreatment: 450 ℃, H2, GHSV = 1000 h−1, 4 h) b: Fe2O3; c: 1Na-Fe2O3; d: 2Na-Fe2O3,(Pretreatment: 450 ℃, CO/H2 = 1∶2, GHSV = 1000 h−1, 4 h)Reaction conditions: 320 ℃, CO2/H2 = 1∶3, GHSV = 1000 h−1, 3 MPa
图 7 样品预处理后铁物种含量
Figure 7 Iron species content of different samples
a: Fe2O3-H2; b: Fe2O3-CO + H2 (CO/H2 = 1∶2); c: 1Na-Fe2O3-CO + H2 (CO/H2 = 1∶2); d: 2Na-Fe2O3-CO + H2 (CO/H2 = 1∶2) Pretreatment: 450 ℃, GHSV = 1000 h−1, 4 h
图 8 1Na-Fe2O3样品CO2加氢反应原位XRD谱图
Figure 8 In-situ XRD patterns of 1Na-Fe2O3 for CO2 hydrogenation
Pretreatment: 450 ℃, CO/H2 = 1∶2, 4 h Reaction conditions: 320 ℃, CO2/H2 = 1∶3, 0.1 MPa, 10 h
表 1 Fe2O3还原反应的热力学分析
Table 1 Thermodynamic analysis of Fe2O3 reduction reaction
Reaction ${\Delta rH}_{{298}}^{ϴ}$/ (kJ·mol−1) ${\Delta r{G} }_{{298}}^{ϴ}$/ (kJ·mol−1) Kp 3Fe2O3 + H2 = 2Fe3O4 + H2O −6.018 −32.772 5.52 × 105 3Fe2O3 + CO = 2Fe3O4 + CO2 −47.184 −61.391 5.72 × 1010 
下载: 导出CSV
表 2 Fe2O3样品的晶粒尺寸
Table 2 Crystal size for different samples
Sample Fe2O3 particle sizea/nm Fe2O3 59.2 1Na-Fe2O3 41.7 2Na-Fe2O3 46.2 a: calculated by Scherrer equation according to the XRD results
下载: 导出CSV
-
[1] 相宏伟, 杨勇, 李永旺. 碳中和目标下的煤化工变革与发展[J]. 化工进展,2022,41(3):1399−1408. doi: 10.16085/j.issn.1000-6613.2021-2314XIANG Hong-wei, YANG Yong, LI Yong-wang. Transformation and development of coal chemical industry under the goal of carbon neutralization[J]. Chem Ind Eng Prog,2022,41(3):1399−1408. doi: 10.16085/j.issn.1000-6613.2021-2314 [2] LU Q, ROSEN J, ZHOU Y S, HUTCHINGS G C, KIMMEL Y G, CHEN J G, JIAO F. A selective and efficient electrocatalyst for carbon dioxide reduction[J]. Nat Commun,2014,5:3242. doi: 10.1038/ncomms4242 [3] WANG W, WANG S P, MA X B, GONG J L. Recent advances in catalytic hydrogenation of carbon dioxide[J]. Chem Soc Rev,2011,40(7):3703−3727. doi: 10.1039/c1cs15008a [4] POROSOFF D M, YANG X F, BOSCOBOINKIK J G. CHEN J G. Molybdenum carbide as alternative catalysts to precious metals for highly selective reduction of CO2 to CO[J]. Angew Chem Int Ed,2014,53(26):6705−6709. doi: 10.1002/anie.201404109 [5] MARTIN O J, MARTIN A, MONDELLI C, MITCHELL S F, SEGAWA T, HAUERT R, DROUILLY C, DANIEL C F, JAVIER P R. Indium oxide as a superior catalyst for methanol synthesis by CO2 hydrogenation[J]. Angew Chem Int Ed,2016,55:6261−6265. doi: 10.1002/anie.201600943 [6] STUDT F, SHARAFUTDINOV I, ABILD-PEDERSEN F F, ELKJAER C S, HUMMELSHOJ J, DAHL S, CHORKENDORFF I K, NORSKOV J. Discovery of a Ni-Ga catalyst for carbon dioxide reduction to methanol[J]. Nat Chem,2014,6(4):320−324. doi: 10.1038/nchem.1873 [7] GRACIANI J, MUDIYANSELAGE K, XU F E, BABER A, EVANS J D, SENANAYAKE S J, STACCHIOLA D, LIU P, HRBEK J F, SANZ J A, RODRIGUEZ J. Highly active copper-ceria and copper-ceria-titania catalysts for methanol synthesis from CO2[J]. Sci,2014,345(6196):546−550. doi: 10.1126/science.1253057 [8] MORET S J, DYSON P, LAURENCZY G. Direct synthesis of formic acid from carbon dioxide by hydrogenation in acidic media[J]. Nat Commun,2014,5:4017. doi: 10.1038/ncomms5017 [9] ZHU Y, ZHANG S R, YE Y C, ZHANG X Q, WANG L, ZHU W, CHENG F, TAO F. Catalytic conversion of carbon dioxide to methane on rutheniumcobalt bimetallic nanocatalysts and correlation between surface chemistry of catalysts under reaction conditions and catalytic performances[J]. ACS Catal,2012,2(11):2403−2408. doi: 10.1021/cs3005242 [10] ISTRY H, VARELA A S S. BONIFACIO C, ZEGKINOGLOU I, SINEV I, CHOI Y W, KISSLINGER K A, STACH E C, YANG J, STRASSER P, CUENYA B R. Corrigendum: Highly selective plasma-activated copper catalysts for carbon dioxide reduction to ethylene[J]. Nat Commun,2016,7:12945. doi: 10.1038/ncomms12945 [11] WEI J, SUN J, WEN Z Y, FANG C Y, GE Q J, XU H Y. New insights into the effect of sodium on Fe3O4-based nanocatalysts for CO2 hydrogenation to light olefins[J]. Catal Sci Technol,2016,6:4786−4793. doi: 10.1039/C6CY00160B [12] SHROFF M D, KALAKKAD D S, COULTER K E, KOHLER S D, HARRINGTON M S, JACKSON N B, SAULT A G, DATYE A K. Activation of precipitated iron Fischer-Tropsch synthesis catalysts[J]. J Catal,1995,156:185−207. doi: 10.1006/jcat.1995.1247 [13] DING M Y, YANG Y, WU B S, WANG T J, MA L L, XIANG H W, LI Y W. Transformation of carbonaceous species and its influence on catalytic performance for iron-based Fischer-Tropsch synthesis catalyst[J]. J Mol Catal A: Chem,2011,351:165−173. doi: 10.1016/j.molcata.2011.10.001 [14] 高新华, 王康洲, 张建利, 马清祥, 范素兵, 赵天生. CO/CO2催化加氢双功能催化剂新进展[J]. 石油学报,2019,35(6):1228−1238.GAO Xin-hua, WANG Kang-zhou, ZHANG Jian-li, MA Qing-xiang, FAN Su-bing, ZHAO Tian-sheng. New development of bifunctional catalysts for CO/CO2 catalytic hydrogenation[J]. Acta Pet Sin: Pet Proc Sect,2019,35(6):1228−1238. [15] ZHAO H B, LIU J X, YANG C, YAO S Y, SU H Y, GAO Z R, DONG M, WANG J G, HOU Y L, LI W X, MA D. Synthesis of iron-carbide nanoparticles: identification of the active phase and mechanism of Fe-based Fischer-Tropsch synthesis[J]. CCS Chem,2021,196:2712−2724. [16] YAO R W, WEI J, GE Q J, XU J, HAN Y, MA Q X, XU H Y, SUN J. Monometallic Iron catalysts with synergistic Na and S for higher alcohols synthesis via CO2 hydrogenation[J]. Appl Catal B: Environ,2021,298:120556. doi: 10.1016/j.apcatb.2021.120556 [17] 段建国, 王亚雄, 刘全生, 周晨亮. 费托合成铁基催化剂关键影响因素研究进展[J]. 无机盐工业,2017,49(11):1−7.DUAN Jian-guo, WANG Ya-xiong, LIU Quan-sheng, ZHOU Chen-liang. Research advance in key influencing factors of iron-based catalyst for Fischer-Tropsch synthesis[J]. Inorg Chem,2017,49(11):1−7. [18] 张建利, 王旭, 马丽萍, 于旭飞, 马清祥, 范素兵, 赵天生. 层状K/Mg-Fe-Al催化剂的制备及其CO加氢性能研究[J]. 燃料化学学报,2017,45(12):1489−1498. doi: 10.3969/j.issn.0253-2409.2017.12.011ZHANG Jian-li, WANG Xu, MA Li-ping, YU Xu-fei, MA Qing-xiang, FAN Su-bing, ZHAO Tian-sheng. Preparation of layered K /Mg-Fe-Al catalysts and its catalytic performances in CO hydrogenation[J]. J Fuel Chem Technol,2017,45(12):1489−1498. doi: 10.3969/j.issn.0253-2409.2017.12.011 [19] 定明月, 杨勇, 相宏伟, 李永旺. 费托合成Fe基催化剂中铁物相与活性的关系[J]. 催化学报,2010,31(9):1145−1150.DING Ming-yue, YANG Yong, XIANG Hong-wei, LI Yong-wang. Relationship between iron phase and activity of iron-based Fischer-Tropsch synthesis catalyst[J]. Chin J Catal,2010,31(9):1145−1150. [20] BUKUR B D, KORANNE M, LANG X S, RAO K R P M P, HUFFMAN G. Pretreatment effect studies with a precipitated iron Fischer-Tropsch catalyst[J]. Appl Catal A: Gen,1995,126(1):85−113. doi: 10.1016/0926-860X(95)00020-8 [21] 傅献彩, 沈文霞, 姚天扬, 侯文华. 物理化学上册[M]. 第五版 南京大学化学化工学院: 高等教育出版社, 1989.FU Xian-cai, SHEN Wen-xia, YAO Tian-yang, HOU Wen-hua. Physical Chemistry (Vol. 1) [M]. 5th ed. School of Chemistry and Chemical Engineering, Nanjing University: Higher Education Press, 1989. [22] 冯波, 武鹏, 李永龙. 原位XRD研究Fe2O3的还原机理[J]. 天然气化工,2021,46(1):66−68 + 106.FENG Bo, WU Peng, LI Yong-long. In situ XRD analysis of reduction mechanism of Fe2O3[J]. Nat Gas Chem Ind,2021,46(1):66−68 + 106. [23] XU Y, ZHAI P, DENG Y C, XIE J L, LIU X, WANG S, MA D. Highly selective olefin production from CO2 hydrogenation on iron catalysts: a subtle synergy between manganese and sodium additives[J]. Angew Chem Int Ed,2020,59:21736−21744. doi: 10.1002/anie.202009620 [24] ZHANG Z Q, HUANG G X, TANG X L, YIN H R, KANG J C, ZHANG Q H, WANG Y. Zn and Na promoted Fe catalysts for sustainable production of high-valued olefins by CO2 hydrogenation[J]. J Fuel Chem Technol,2022,309:122105. [25] 卢鹏飞. Fe3O4/Ni-分子筛串联催化CO2加氢制高碳烃反应性能及机理研究[D]. 银川: 宁夏大学, 2021.LU Peng-fei. Catalytic performance and mechanism of Fe3O4/Ni-zeolite tandem catalysts for CO2 hydrogenation to heavy hydrocarbons[D]. Yinchuan: Ningxia University, 2021. [26] 位重洋. 铁基催化剂结构调控及其催化二氧化碳合成烯烃的研究[D]. 郑州: 郑州大学, 2020.WEI Chong-yang. Iron-based catalyst structure regulation and its catalyitic synthesis of carbon dioxide to olefins[D]. Zhengzhou: Zhengzhou University, 2020. [27] 马龙, 张玉玺, 高新华, 马清祥, 张建利, 赵天生. Fe3O4@PI催化剂的制备及其费托合成性能[J]. 燃料化学学报,2020,48(7):813−820. doi: 10.3969/j.issn.0253-2409.2020.07.006MA Long, ZHANG Yu-xi, GAO Xin-hua, MA Qing-xiang, ZHANG Jian-li, ZHAO Tian-sheng. Preparation of Fe3O4@PI and its catalytic performances in Fischer-Tropsch synthesis[J]. J Fuel Chem Technol,2020,48(7):813−820. doi: 10.3969/j.issn.0253-2409.2020.07.006 [28] ZHANG Y L, CAO C X, ZHANG C, ZHANG Z P, LIU X L, YANG Z X, ZHU M H, MENG B, XU J, HAN Y F. The study of structure-performance relationship of iron catalyst during a full life cycle for CO2 hydrogenation[J]. J Catal,2019,378:51−62. doi: 10.1016/j.jcat.2019.08.001 [29] PHAM T H, QI Y Y, YANG J, DUAN X Z, QIAN G, ZHOU X G, CHEN D, YUAN W K. Insights into Hägg Iron-carbide-catalyzed Fischer-Tropsch synthesis: suppression of CH4 Formation and enhancement of C–C coupling on χ-Fe5C2 (510)[J]. ACS Catal,2015,5(4):2203−2208. doi: 10.1021/cs501668g [30] LI J F, CHENG X F, ZHANG C H, CHANG Q, WANG J, WANG X P, LV Z G, DONG W S, YANG Y, LI Y W. Effect of alkalis on iron-based Fischer-Tropsch synthesis catalysts: Alkali-FeOx interaction, reduction, and catalytic performance[J]. Appl Catal A: Gen,2016,528:131−141. doi: 10.1016/j.apcata.2016.10.006 -
点击查看大图
计量
- 文章访问数: 2994
- HTML全文浏览量: 33
- PDF下载量: 54
- 被引次数: 0
