从煤、生物质或天然气出发经甲醇制烯烃正在成为最重要的非石油路线低碳烯烃和液态燃料的生产途径。基于SAPO-34和HZSM-5催化剂,甲醇制低碳烯烃(MTO),甲醇制丙烯(MTP)和甲醇制汽油(MTG)已经实现了工业化。与此同时,甲醇制烯烃反应机理也一直是学术界和工业界研究的焦点,然而由于甲醇转化机理十分复杂,且往往受多种因素的影响,使得机理研究工作至今未给出明确详尽的结论。据文献报道,在具有较大笼或交叉孔道结构的SAPO-34, SSZ-13和Hβ催化剂上,甲醇转化主要是通过烃池机理进行。烃池物种包括多甲苯及其对应的质子化产物。随着HZSM-5上甲醇转化双循环机理的提出,近期人们开始关注一维孔道分子筛上的甲醇转化反应,试图通过抑制芳烃循环使得甲醇转化主要通过烯烃甲基化裂解机理进行,发现在具有一维十元环孔道结构的HZSM-22分子筛上甲醇转化能够达到这一效果,产物主要以C3+烯烃为主，乙烯的生成较少。该催化体系的发现对于甲醇制丙烯过程的开发具有重要的意义,然而除了分子筛的拓扑结构,催化剂的酸强度对甲醇转化也具有重要的影响，值得深入研究。为此,本文采用同位素切换/共进料实验,色质谱(GC-MS),热分析(TGA)以及原位红外实验(in situ FTIR)等技术系统研究两种一维十元环结构分子筛HZSM-22和SAPO-11酸强度对于甲醇转化和催化剂失活机理的影响,为开发新型催化剂和优化反应条件以调节产物选择性提供理论指导。
12C/13C-甲醇切换实验表明, HZSM-22和SAPO-11催化的甲醇转化机理主要是烯烃循环,然而由于酸强度的差异导致两种分子筛上甲基化反应和裂解反应对烯烃最终产物分布贡献不同。对于HZSM-22分子筛,催化活性较高，当反应温度低于400 oC时,产物以C5+高碳烃为主,随着反应温度的升高,产物以C2–C4低碳烃为主,且乙烯的增长速率高于丙烯；对于SAPO-11分子筛,催化活性较低，无论反应温度高或低,甲醇转化产物均以C5+高碳烃为主。以上结果表明,催化剂的活性与酸强度相关，且随着反应温度的升高,在酸性较强的HZSM-22分子筛上高碳烃的裂解活性要远高于酸性较弱的SAPO-11分子筛。该推论得到13C-甲醇和12C-1-丁烯共进料实验数据的支持。失活催化剂的GC-MS和TG结果显示,催化剂的失活与酸强度和反应温度密切相关：对于HZSM-22分子筛,较低温度下(<450 oC)催化剂的失活源于稠环化合物的生成和积累,高温下(>450 oC)的失活是源于分子筛表面石墨碳的沉积；对于SAPO-11分子筛,低温下(<400 oC)的失活源于稠环芳烃的生成和积累,高温下(>400 oC)的失活是源于分子筛表面石墨碳的沉积。此外,由于酸强度的差异,与SAPO-11相比,低温下积碳物种更倾向于在HZSM-22分子筛孔口快速形成。这也是HZSM-22分子筛在低温下快速失活的原因。为了进一步证明该结论,本文采用原位红外装置对HZSM-22催化甲醇转化过程中的Br?nsted酸和芳烃物种进行了连续监测。结果显示,在最初的15 min内归属为Br?nsted酸的峰(3585 cm–1)有明显的下降,但随着反应时间的延长, Br?nsted酸的量不再发生变化；与此同时,归属为芳烃物种的峰(3136 cm–1)增加到一定程度后随着反应时间的延长也几乎不再增加。这进一步说明了低温下HZSM-22分子筛的失活是由非活性芳烃积碳物种堵塞孔口造成的。
The conversion of methanol to hydrocarbons has been investigated over HZSM-22 and SAPO-11. Both of these catalysts possess one-dimensional 10-ring channels, but have different acidic strengths. Comparison studies and 12C/13C isotopic switching experiments were conducted to eval-uate the influence of the acidic strength of the catalyst on the conversion of methanol, as well as its deactivation mechanism. Although the conversion of methanol proceeded via an alkene methyla-tion-cracking pathway over both catalysts, the acidity of the catalysts had a significant impact on the conversion and product distribution of these reactions. The stability of the catalysts varied with temperature. The catalysts were deactivated at high temperature by the deposition of graphitic coke on their outer surface. Deactivation also occurred at low temperatures a result that the pores of the catalyst were blocked by polyaromatic compounds. The co-reaction of 13C-methanol and 12C-1-butene confirmed the importance of the acidity of the catalyst on the distribution of the hy-drocarbon products.
参考文献
| [1] | Olsbye U;Svelle S;Bjorgen M;Beato P,Janssens T V W,Joensen F,Bordiga S,Lillerud K P .[J].Angew Chem Int Ed,2012,51:5810. |
| [2] | 魏迎旭,张大治,刘中民,苏宝连.沸石和SAPO分子筛催化卤代甲烷转化制烯烃和汽油：一种新的MTO和MTG路线[J].催化学报,2012(01):11-21. |
| [3] | St?cker M .[J].Microporous Mesoporous Mater,1999,29:3. |
| [4] | Tian P;Wei Y X;Ye M;Liu Z M .[J].ACS Catal,2015,5:1922. |
| [5] | Hemelsoet, K.;Van Der Mynsbrugge, J.;De Wispelaere, K.;Waroquier, M.;Van Speybroeck, V. .Unraveling the reaction mechanisms governing methanol-to-olefins catalysis by theory and experiment[J].Chemphyschem: A European journal of chemical physics and physical chemistry,2013(8):1526-1545. |
| [6] | Liang J;Li H Y;Zhao S;Guo W G,Wang R H,Ying M L .[J].Appl Catal,1990,64:31. |
| [7] | Koempel H;Liebner W .[J].Stud Surf Sci Catal,2007,167:261. |
| [8] | Chang C D .[J].Catal Today,1992,13:103. |
| [9] | Yurchak S .[J].Stud Surf Sci Catal,1988,36:251. |
| [10] | Topp-J?rgensen J .[J].Stud Surf Sci Catal,1988,36:293. |
| [11] | Chen J Q;Bozzano A;Glover B;Fuglerud T,Kvisle S .[J].Catal Today,2005,106:103. |
| [12] | Dahl IM.;Kolboe S. .ON THE REACTION MECHANISM FOR HYDROCARBON FORMATION FROM METHANOL OVER SAPO-34 .2. ISOTOPIC LABELING STUDIES OF THE CO-REACTION OF PROPENE AND METHANOL[J].Journal of Catalysis,1996(1):304-309. |
| [13] | Dahl I M;Kolboe S .[J].J Catal,1994,149:458. |
| [14] | Dahl I;Kolboe S .[J].Catal Lett,1993,20:329. |
| [15] | Arstad B;Kolboe S .[J].J Am Chem Soc,2001,123:8137. |
| [16] | Song WG.;Nicholas JB.;Heneghan CS.;Haw JF. .Methylbenzenes are the organic reaction centers for methanol-to-olefin catalysis on HSAPO-34[J].Journal of the American Chemical Society,2000(43):10726-10727. |
| [17] | Wang, C.-M.;Wang, Y.-D.;Liu, H.-X.;Xie, Z.-K.;Liu, Z.-P. .Catalytic activity and selectivity of methylbenzenes in HSAPO-34 catalyst for the methanol-to-olefins conversion from first principles[J].Journal of Catalysis,2010(2):386-391. |
| [18] | Hereijgers, B.P.C.;Bleken, F.;Nilsen, M.H.;Svelle, S.;Lillerud, K.-P.;Bj?rgen, M.;Weckhuysen, B.M.;Olsbye, U. .Product shape selectivity dominates the Methanol-to-Olefins (MTO) reaction over H-SAPO-34 catalysts[J].Journal of Catalysis,2009(1):77-87. |
| [19] | Xu S T;Zheng A M;Wei Y X;Chen J R,Li J Z,Chu Y Y,Zhang M Z,Wang Q Y,Zhou Y,Wang J B,Deng F,Liu Z M .[J].Angew Chem Int Ed,2013,52:11564. |
| [20] | Wulfers M J;Jentoft F C .[J].ACS Catal,2014,4:3521. |
| [21] | Li J Z;Wei Y X;Chen J R;Xu S T,Tian P,Yang X F,Li B,Wang J B,Liu Z M .[J].ACS Catal,2015,5:661. |
| [22] | Wang C M;Wang Y D;Xie Z K;Liu Z P .[J].J Phys Chem C,2009,113:4584. |
| [23] | Bj?rgen M;Olsbye U;Petersen D;Kolboe S .[J].J Catal,2004,221:1. |
| [24] | Li J Z;Wei Y X;Chen J R;Tian P,Su X,Xu S T,Qi Y,Wang Q Y,Zhou Y,He Y L,Liu Z M .[J].J Am Chem Soc,2012,134:836. |
| [25] | Li J Z;Wei Y X;Xu S T;Tian P,Chen J R,Liu Z M .[J].Catal Today,2014,226:47. |
| [26] | Svelle S;Joensen F;Nerlov J;Olsbye U,Lillerud K P,Kolboe S,Bj?rgen M .[J].J Am Chem Soc,2006,128:14770. |
| [27] | Bjorgen M;Svelle S;Joensen F;Nerlov J,Kolboe S,Bonino F,Palumbo L,Bordiga S,Olsbye U .[J].J Catal,2007,249:195. |
| [28] | Svelle S;Olsbye U;Joensen F;Bj?rgen M .[J].J Phys Chem C,2007,111:17981. |
| [29] | Teketel S;Svelle S;Lillerud K-P;Olsbye U .[J].ChemCatChem,2009,1:78. |
| [30] | Teketel S;Olsbye U;Lillerud K-P;Beato P,Svelle S .[J].Microporous Mesoporous Mater,2010,136:33. |
| [31] | Li J Z;Wei Y X;Liu G Y;Qi Y,Tian P,Li B,He Y L,Liu Z M .[J].Catal Today,2011,171:221. |
| [32] | Li J Z;Wei Y X;Qi Y;Tian P,Li B,He Y L,Chang F X,Sun X D,Liu Z M .[J].Catal Today,2011,164:288. |
| [33] | Yuen L-T;Zones S I;Harris T V;Gallegos E J,Auroux A .[J].Microporous Mater,1994,2:105. |
| [34] | Bleken F;Bj?rgen M;Palumbo L;Bordiga S,Svelle S,Lillerud K-P,Olsbye U .[J].Top Catal,2009,52:218. |
| [35] | Westg?rd Erichsen, M.;Svelle, S.;Olsbye, U..H-SAPO-5 as methanol-to-olefins (MTO) model catalyst: Towards elucidating the effects of acid strength[J].Journal of Catalysis,2013:94-101. |
| [36] | Yang G J;Wei Y X;Xu S T;Chen J R,Li J Z,Liu Z M,Yu J H,Xu R R .[J].J Phys Chem C,2013,117:8214. |
| [37] | Guisnet M;Costa L;Ribeiro F R .[J].J Mol Catal A,2009,305:69. |
| [38] | Buchholz A;Wang W;Xu M;Arnold A,Hunger M .[J].Microporous Mesoporous Mater,2002,56:267. |
| [39] | 李冰,田鹏,齐越,张琳,徐舒涛,苏雄,樊栋,刘中民.SAPO-11分子筛晶化过程研究[J].催化学报,2013(03):593-603. |
| [40] | Jiang Y J;Huang J;Dai W L;Hunger M .[J].Solid State Nucl Magn Reson,2011,39:116. |
| [41] | Müller M;Harvey G;Prins R .[J].Microporous Mesoporous Mater,2000,34:281. |
| [42] | 郑安民,黄信炅,王强,张海禄,邓风,刘尚斌.固体核磁共振技术在固体酸催化剂表征及催化反应机理研究之应用进展[J].催化学报,2013(03):436-491. |
| [43] | Hunger M;Anderson M W;Ojo A;Pfeifer H .[J].Microporous Mater,1993,1:17. |
| [44] | Hunger M .Bronsted acid sites in zeolites characterized by multinuclear solid-state NMR spectroscopy[J].Catalysis Reviews. Science and Engineering,1997(4):345-393. |
| [45] | Zhang W P;Ma D;Liu X C;Liu X M,Bao X H.[M].Chem Commun,1999:1091. |
| [46] | Borade R B;Adnot A;Kaliaguine S .[J].Zeolites,1991,11:710. |
| [47] | Sousa Z S B;Cesar D V;Henriques C A;Teixeira da Silva V .[J].Catal Today,2014,234:182. |
- 下载量()
- 访问量()
- 您的评分：
-
10%
-
20%
-
30%
-
40%
-
50%