Study on the coke formation behavior on PtSn/Al2O3 propane dehydrogenation catalyst
-
摘要: 通过HRTEM、XRD、FT-IR、Raman、13C NMR、NH3-TPD、DTG及元素分析等表征手段，研究了丙烷脱氢PtSn催化剂积炭性质及其对催化剂结构的影响，分析了催化剂的积炭失活过程。结果表明，积炭覆盖活性位并堵塞催化剂孔道是催化剂失活主要因素；与新鲜催化剂相比，催化剂积炭完全失活后，Pt颗粒粒径并没有明显变化；完全失活时，XRD谱图出现了无定形石墨炭的衍射峰；随着积炭量的增加，焦的石墨化程度越高，芳构化程度加深，难以消除的炭增多，再生难度加大。提出丙烷在Pt活性位深度脱氢形成积炭并向载体转移的历程，认为更为稳定的C24H12是积炭前驱体。Abstract: The nature and effect of coke formation on PtSn dehydrogenation catalyst were investigated by various technologies, such as HRTEM, XRD, FT-IR, Raman, 13C NMR, NH3-TPD, DTG and ultimate analysis. The deactivation process of the catalyst was also discussed. The results showed that the catalyst deactivation was mainly caused by deposited carbon, which covered active sites and blocked the pores of the catalyst. The diffraction peaks of the amorphous graphite carbon were observed in the XRD patterns of the fully deactivated catalyst. Furthermore, the degree of aromatization and graphitization of coke formed in the catalyst were enhanced. It was difficult to regenerate the deactivated catalyst through coke elimination. It is proposed that the carbon deposit proceeded on the Pt active site by propane deep dehydrogenation and the deposited carbon could transfer to the surface of the support. The coke precursor is probably C24H12 when the coke content was accumulated to a certain degree.
-
Key words:
- coke /
- deactivation /
- dehydrogenation catalysts /
- aromatization /
- graphitization
-
图 1 催化剂的HRTEM照片
Figure 1 HRTEM images of the catalysts
(a): fresh catalyst; (b): sample C5 regenerated catalyst
图 2 不同积炭量催化剂的XRD谱图
Figure 2 XRD patterns of the catalysts with different carbon deposit
a: C5; b: fresh; c: C2; d: C1; e: C4
图 3 不同积炭量催化剂的FT-IR谱图
Figure 3 FT-IR spectra of the catalysts with different carbon deposit
图 4 不同积炭量催化剂的Raman谱图
Figure 4 Raman spectra of the catalysts with different carbon deposit
图 5 不同积炭量催化剂的13C NMR谱图
Figure 5 13C NMR spectra of the catalysts with different carbon deposit
图 6 不同积炭催化剂的DTG曲线
Figure 6 DTG profiles of the catalysts with different carbon deposit
表 1 不同积炭量催化剂的活性
Table 1 Effect of coke deposit amount on the catalytic activity
Sample Conversion xmol/% Selectivity smol/% Coke formation w/% Fresh* 35.46 94.36 - C1 35.42 95.28 1.57 C2 35.65 95.27 5.78 C3 33.42 96.08 7.68 C4 27.45 89.28 10.86 C5 3.84 49.36 27.89 reaction conditions: 600 ℃, H2/C3H8 (molar ratio)=1.2:1, atmospheric pressure, space velocity (volume)=2 500 h-1 * received after propane contacted with the catalyst 
下载: 导出CSV
表 2 不同积炭催化剂的比表面积及孔结构
Table 2 Surface area and porosity data of the catalyst samples
Sample Fresh C1 C2 C3 C5 Surface area A/(m2·g-1) 173 167 159 153 142 Pore volume v/(mL·g-1) 0.51 0.49 0.43 0.38 0.16 Average pore size d/nm 11.79 11.67 10.8 10.07 7.52
下载: 导出CSV
表 3 积炭催化剂红外吸收峰的归属和可能结构
Table 3 Assignation and possible structure of FT-IR absorption peak
Wave./cm-1 Assignation Possible structure 3 460 νOH C-OH 2 921 νasCH2 -CH2- 2 853 νCH ＞CH- 1 631 δC=C -C=C-or Ar 1 570 δC=C -C=C-or Ar 1 460 δCH2 -CH2- 1 380 δs CH3 -CH3 1 086 νC-O -C-OH 780 δAr-H Ar 737 δAr-H Ar
下载: 导出CSV
表 4 不同积炭催化剂的酸量及酸分布
Table 4 Acid amount and acid distribution of the catalysts with different carbon deposit
Sample Total acid amount/(mmol·g-1) Acid distribution/(mmol·g-1) 150-250 ℃ 250-400 ℃ 400-500 ℃ Fresh 0.420 0.075 0.259 0.087 C1 0.348 0.055 0.234 0.060 C2 0.337 0.049 0.232 0.056 C3 0.329 0.048 0.230 0.051 C4 0.279 0.041 0.198 0.040 C5 0.039 0.023 0.009 0.007
下载: 导出CSV
表 5 催化剂中的C、H含量分析
Table 5 Carbon and hydrogen content of the catalysts with different carbon deposit
Sample C1 C2 C4 C5 C w/% 1.57 5.78 10.86 27.89 H w/% 0.15 0.26 0.46 1.26 H/C (mol ratio) 1.14 0.54 0.50 0.27
下载: 导出CSV
-
[1] RAZAVIAN M, FATEMI S. Synthesis and application of ZSM-5/SAPO-34 and SAPO-34/ZSM-5 composite systems for propylene yield enhancement in propane dehydrogenation process[J]. Microporous Mesoporous Mater, 2015, 201:176-189. doi: 10.1016/j.micromeso.2014.09.022 [2] LONG L, LANG W, YAN X, XIA K, GUO Y. Yttrium-modified alumina as support for trimetallicPtSnIn catalysts with improved catalytic performance in propane dehydrogenation[J]. Fuel Process Technol, 2016, 146:48-55. doi: 10.1016/j.fuproc.2016.02.012 [3] ZHOU S, ZHOU Y, SHI J, ZHANG Y, SHENG X, ZHANG Z. Synthesis of Ce-doped mesoporous γ -alumina with enhanced catalytic performance for propane dehydrogenation[J]. J Mater Sci, 2015, 50:3984-3993. doi: 10.1007/s10853-015-8954-8 [4] ZHANG Y, ZHOU Y, HUANG L, ZHOU S, SHENG X, WANG Q, ZHANG C. Structure and catalytic properties of the Zn-modified ZSM-5 supported platinum catalyst for propane dehydrogenation[J]. Chem Eng J, 2015, 270:352-361. doi: 10.1016/j.cej.2015.01.008 [5] ANNALAND M S, KUIPERS J A M, SWAAIJ W P M. A kinetic rate expression for the time-dependent coke formation rate during propane dehydrogenation over a platinum alumina monolithic catalyst[J]. Catal Today, 2001, 66:427-436. doi: 10.1016/S0920-5861(00)00640-4 [6] LARSSON M, HULTEN M, BLEKKAN E A, ANDERSSON B. The effect of reaction conditions and time on stream on the coke formed during propane dehydrogenation[J]. J Catal, 1996, 164(1):44-53. doi: 10.1006/jcat.1996.0361 [7] 张海娟, 王振宇, 李江红, 乔凯, 张舒冬.反应条件对丙烷脱氢催化剂积炭行为的影响[J].天然气化工, 2014, 39(2):38-42. http://www.cnki.com.cn/Article/CJFDTOTAL-TRQH201402013.htm.ZHANG Hai-juan, WANG Zhen-yu, LI Jiang-hong, QIAO Kai, ZHANG Shu-dong. Effect of reaction conditions on coke formation over the catalyst for propane dehydrogenation[J]. Nat Gas Chem Ind, 2014, 39(2):38-42. http://www.cnki.com.cn/Article/CJFDTOTAL-TRQH201402013.htm [8] YANG J, STANSBERRY P G, ZONDLO J W, STILLER A H. Characteristics and carbonization behaviors of coal extracts[J]. Fuel Process Technol, 2002, 79(3):207-215. doi: 10.1016/S0378-3820(02)00177-7 [9] EISENBACH D, GALLEI E. Infrared spectroscopic investigations relating to coke formation on zeolites:I. Adsorption of hexene-1 and n-hexane on zeolites of type Y[J]. J Catal, 1979, 56(3):377-389. doi: 10.1016/0021-9517(79)90130-1 [10] Van DOOM J, MOULIJN J A. Extraction of spent hydrotreating catalysts studied by fouriertransform infra-red spectroscopy[J]. Fuel Process Technol, 1990, 26(1):39-51. doi: 10.1016/0378-3820(90)90022-K [11] MATSUSHITA K, HAUSER A, MARAFI A, KOIDE R, STANISLAUS A. Initial coke deposition onhydrotreating catalysts. Part 1. Changes in coke properties as a function of time onstream[J]. Fuel, 2004, 83(7/8):1031-1038. [12] CERQUEIRA H S, SIEVERS C, JOLY G, MAGNOUX P, LERCHER J A. Multitechnique characterization of coke produced during commercial resid FCC operation[J]. Ind Eng Chem Res, 2005, 44(7):2069-2077. doi: 10.1021/ie048963k [13] DUMONT M, CHOLLON G, DOURGES M A, PAILLER R, BOURRAT X, NASLAIN R, BRUNEEL J L, COUZI M. Chemical, microstructural and thermal analyses of a naphthalene-derived mesophase pitch[J]. Carbon, 2002, 40(9):1475-1486. doi: 10.1016/S0008-6223(01)00320-7 [14] LI J, NAGA K, OHZAWA Y, SHAMES A I, PANICH A M. Effect of surface fluorination on the electrochemical behavior of petroleum cokes for lithium ion battery[J]. J Fluorine Chem, 2005, 126(2):265-273. doi: 10.1016/j.jfluchem.2004.09.034 [15] 于德泉, 杨峻山, 谢晶曦.分析化学手册(第五分册), 核磁共振波谱分析[M].北京:化学工业出版社, 1998..YU De-quan, YANG Jun-shan, XIE Jing-xi. Handbook of Analytical Chemistry-Nuclear magnetic resonance spectroscopy analysis (Vol.5)[M]. BeiJing:Chemical Industry Press, 1998. [16] PRADHAN A R, JONG S J, TSAI T C, LIU S B. An ex situ methodology for characterization of coke by TGA and 13C CP-MAS NMR spectroscopy[J], Appl Catal A:Gen, 1997, 165:489-497. doi: 10.1016/S0926-860X(97)00231-7 [17] 张涛, 徐竹生.长链烷烃脱氢铂锡工业催化剂的表面积炭特征[J].石油化工, 1992(12):794-799. http://www.cnki.com.cn/Article/CJFDTOTAL-SYHG199212001.htm.ZHANG Tao, XU Zhu-sheng. Characteristic of carbon deposits on Pt-Sn commercial catalyst for the dehydrogenation of paraffins[J]. Petrochem Technol, 1992(12):794-799. http://www.cnki.com.cn/Article/CJFDTOTAL-SYHG199212001.htm [18] LI Q, SUI Z, ZHOU X, ZHU Y, ZHOU J, CHEN D. Coke formation on Pt-Sn/A12O3catalyst in propane dehydrogenation:Coke characterization and kinetic study[J]. Top Catal, 2011, 54:888-896. doi: 10.1007/s11244-011-9708-8 -
点击查看大图
计量
- 文章访问数: 89
- HTML全文浏览量: 32
- PDF下载量: 10
- 被引次数: 0
