本研究使用晶種誘導的結晶方式合成不同鋁與鎵比例之奈米尺徑H-[Ga, Al]ZSM-5，探討觸媒內布朗斯特酸與非骨架鎵對於甲醇轉化為芳香族(MTA)反應的協同效應。在物化性結果上，由於合成過程中鎵離子相對於鋁離子較難嵌入ZSM-5骨架內，因此鎵含量的提升會導致布朗斯特酸量下降，但非骨架鎵含量隨之上升。
在反應性測試上，發現含鎵觸媒比一般HZSM-5具有更高的芳香族產率，說明具有脫氫活性的非骨架鎵能夠促進MTA反應中芳香族的生成。為了證實非骨架鎵的效用，我們以酸處理的方式選擇性除去觸媒內的非骨架鎵，且與原先的觸媒進行比較，發現含鎵觸媒經酸處理後的芳香族產率有明顯下降，且脫氫訊號大幅降低，證實在非骨架鎵的協同下，觸媒能加速甲醇轉化為芳香族。而在所有觸媒中，非骨架鎵/布朗斯特酸比例為0.06的觸媒具有最高的芳香化能力(在500 oC的芳香族產率為79.5%)，此與布朗斯特酸和非骨架鎵之間的協同效應有關。在MTA反應中，相對多量的布朗斯特酸有助於甲醇與二甲醚進行脫水，以及後續低碳數烯烴類的聚合與環化反應，而非骨架鎵能將反應中間物的烯烷類脫氫，在布朗斯特酸的協同下加速芳香族的生成。

The aim of this study is to investigate the synergy of the extra-framework Ga species and the Brønsted acid of nanosized aluminogallosilicate MFI catalysts in methanol conversion to aromatics (MTA). A series of nanosized H-[Al]ZSM-5, H-[Ga, Al]ZSM-5, and H-[Ga]ZSM-5 catalysts with a fixed Si-to-M3+ ratio (M = Al and Ga) were synthesized by a seed-induced crystallization method. We found the concentration of the Brønsted acid decreased, while the concentration of extra-framework Ga species increased with the enhanced extent of Ga substitution in the catalysts. It is assumed that Ga is less prone to be incorporated into the ZSM-5 scaffold than Al is.
To reveal the catalytic nature of the extra-framework Ga species, an acid treatment was applied to selectively extract extra-framework Ga species of as-synthesized catalysts. A comparative evaluation of as-synthesized and acid-treated catalysts in MTA showed the dehydrogenative nature of the extra-framework Ga species, which is essential in the enhancement of aromatics. Among tested catalysts, H-[Ga, Al]ZSM-5 with a low extra-framework Ga-to-Brønsted acid ratio (0.06) was the most effective (The aromatics yield of 79.5% was achieved in MTA at 500 oC). The efficacy is due to the contact synergy of the extra-framework Ga species and the Brønsted acid. A high concentration of the Brønsted acid is needed to promote dehydration of methanol and dimethyl ether (DME) and then to facilitate subsequent oligomerization and cyclization. Extra-framework Ga species can dehydrogenate the intermediates including alkenes and alkanes, and with the assistance of neighboring Brønsted acid sites, cyclization can be accelerated.

1.Olah, G.A., Beyond oil and gas: the methanol economy. Angewandte Chemie International Edition, 2005. 44(18): p. 2636-2639.
2.Choudhary, V.R., et al., Characterization of coke on H-gallosilicate (MFI) propane aromatization catalyst.: Influence of coking conditions on nature and removal of coke. Microporous and Mesoporous Materials, 1998. 21(1): p. 91-101.
3.Specht, M., et al., Synthesis of methanol from biomass/CO2 resources. Synthesis, 1999. 2: p. 1-6.
4.Obert, R. and B.C. Dave, Enzymatic conversion of carbon dioxide to methanol: enhanced methanol production in silica sol-gel matrices. Journal of the American Chemical Society, 1999. 121(51).
5.Shahhosseini, H.R., et al., Multi-objective optimisation of steam methane reforming considering stoichiometric ratio indicator for methanol production. Journal of Cleaner Production, 2018. 180: p. 655-665.
6.Chen, N.Y., T.F. Degnan Jr., and L.R. Koenig, Liquid fuel from carbohydrates. Chemtech, 1986. 16: p. 506-511.
7.Hagen, J., Homogeneously catalyzed industrial processes. Industrial Catalysis: A Practical Approach, Second Edition, 2006: p. 59-82.
8.Wang, H. and M. Frenklach, Transport properties of polycyclic aromatic hydrocarbons for flame modeling. Combustion and flame, 1994. 96(1-2): p. 163-170.
9.Weitkamp, J., Zeolites and catalysis. Solid State Ionics, 2000. 131(1-2): p. 175-188.
10.Olsbye, U., et al., Conversion of Methanol to Hydrocarbons: How Zeolite Cavity and Pore Size Controls Product Selectivity. Angewandte Chemie International Edition, 2012. 51(24): p. 5810-5831.
11.Stöcker, M., Methanol-to-hydrocarbons: catalytic materials and their behavior1. Microporous and Mesoporous Materials, 1999. 29(1-2): p. 3-48.
12.Chang, C.D., A.J. Silvestri, and R.L. Smith, Production of gasoline hydrocarbons. 1975, Google Patents.
13.Chang, C.D., A.J. Silvestri, and R.L. Smith, Production of gasoline hydrocarbons, U.p. office, Editor. 1975.
14.Chang, C.D. and A.J. Silvestri, The conversion of methanol and other O-compounds to hydrocarbons over zeolite catalysts. Journal of Catalysis, 1977. 47(2): p. 249-259.
15.Dejaifve, P., et al., Reaction pathways for the conversion of methanol and olefins on H-ZSM-5 zeolite. Journal of Catalysis, 1980. 63(2): p. 331-345.
16.Inoue, Y., K. Nakashiro, and Y. Ono, Selective conversion of methanol into aromatic hydrocarbons over silver-exchanged ZSM-5 zeolites. Microporous Materials, 1995. 4(5): p. 379-383.
17.Robinson, J.G., D.I. Barnes, and A.M. Carswell, Alumina and/or silica catalysts supported on microporous glass. 1983, Google Patents.
18.Parker, L.M. and D.M. Bibby, Synthesis and some properties of two novel zeolites, KZ-1 and KZ-2. Zeolites, 1983. 3(1): p. 8-11.
19.Hoelderich, W.D., W.D.D. Mross, and M.D. Schwarzmann, Verfahren zur Herstellung von Aromaten aus Methanol und/oder Dimethylether. 1983, Google Patents.
20.Chao, K.-j., et al., Temperature-programmed desorption studies on ZSM—5 zeolites. Zeolites, 1984. 4(1): p. 2-4.
21.Cęckiewicz, S., Conversion of methanol into light hydrocarbons on erionite–offretite (T) zeolite. Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 1984. 80(11): p. 2989-2998.
22.Itoh, H., et al., Role of acid property of various zeolites in the methanol conversion to hydrocarbons. J. Catal.;(United States), 1984. 85(2).
23.Xu, Y., et al., An investigation into the conversion of methanol to hydrocarbons over a SAPO-34 catalyst using magic-angle-spinning NMR and gas chromatography. Catalysis Letters, 1990. 4(3): p. 251-260.
24.Ravishankar, R., et al., Characterization and catalytic properties of zeolite MCM-22. Microporous Materials, 1995. 4(1): p. 83-93.
25.Mikkelsen, Ø. and S. Kolboe, The conversion of methanol to hydrocarbons over zeolite H-beta. Microporous and Mesoporous Materials, 1999. 29(1): p. 173-184.
26.Dahl, I.M. and S. Kolboe, On the Reaction Mechanism for Hydrocarbon Formation from Methanol over SAPO-34: I. Isotopic Labeling Studies of the Co-Reaction of Ethene and Methanol. Journal of Catalysis, 1994. 149(2): p. 458-464.
27.Dahl, I.M. and S. Kolboe, On the Reaction Mechanism for Hydrocarbon Formation from Methanol over SAPO-34: 2. Isotopic Labeling Studies of the Co-reaction of Propene and Methanol. Journal of Catalysis, 1996. 161(1): p. 304-309.
28.Sun, X., et al., On reaction pathways in the conversion of methanol to hydrocarbons on HZSM-5. Journal of Catalysis, 2014. 317: p. 185-197.
29.Conte, M., et al., Modified zeolite ZSM-5 for the methanol to aromatics reaction. Catalysis Science & Technology, 2012. 2(1): p. 105-112.
30.Zhang, J., et al., Increasing para-xylene selectivity in making aromatics from methanol with a surface-modified Zn/P/ZSM-5 catalyst. ACS Catalysis, 2015. 5(5): p. 2982-2988.
31.Ono, Y., Transformation of lower alkanes into aromatic hydrocarbons over ZSM-5 zeolites. Catalysis Reviews, 1992. 34(3): p. 179-226.
32.Schreiber, M.W., et al., Lewis–Brønsted Acid Pairs in Ga/H-ZSM-5 To Catalyze Dehydrogenation of Light Alkanes. Journal of the American Chemical Society, 2018. 140(14): p. 4849-4859.
33.Al-Yassir, N., et al., Synthesis of stable H-galloaluminosilicate MFI with hierarchical pore architecture by surfactant-mediated base hydrolysis, and their application in propane aromatization. Journal of Molecular Catalysis A: Chemical, 2012. 360: p. 1-15.
34.Nowak, I., et al., Effect of H2–O2 pre-treatments on the state of gallium in Ga/H-ZSM-5 propane aromatisation catalysts. Applied Catalysis A: General, 2003. 251(1): p. 107-120.
35.Faro Júnior, A.C., et al., XAFS study of H-ZSM5 catalysts modified with gallium. Catalysis Today, 2008. 133-135: p. 913-918.
36.Ausavasukhi, A. and T. Sooknoi, Tunable activity of [Ga] HZSM-5 with H2 treatment: Ethane dehydrogenation. Catalysis Communications, 2014. 45: p. 63-68.
37.Fricke, R., et al., Incorporation of gallium into zeolites: Syntheses, properties and catalytic application. Chemical reviews, 2000. 100(6): p. 2303-2406.
38.Al-Yassir, N., M. Akhtar, and S. Al-Khattaf, Physicochemical properties and catalytic performance of galloaluminosilicate in aromatization of lower alkanes: a comparative study with Ga/HZSM-5. Journal of Porous Materials, 2012. 19(6): p. 943-960.
39.Choudhary, V.R., et al., Aromatization of dilute ethylene over Ga-modified ZSM-5 type zeolite catalysts. Microporous and mesoporous materials, 2001. 47(2-3): p. 253-267.
40.Choudhary, V.R. and S.K. Jana, Benzylation of benzene by benzyl chloride over Fe-, Zn-, Ga- and In-modified ZSM-5 type zeolite catalysts. Applied Catalysis A: General, 2002. 224(1): p. 51-62.
41.Choudhary, V.R., S.K. Jana, and B.P. Kiran, Alkylation of benzene by benzyl chloride over H-ZSM-5 zeolite with its framework Al completely or partially substituted by Fe or Ga. Catalysis Letters, 1999. 59(2): p. 217-219.
42.Choi, S.-W., et al., Propane dehydrogenation catalyzed by gallosilicate MFI zeolites with perturbed acidity. Journal of Catalysis, 2017. 345(Supplement C): p. 113-123.
43.Dwyer, F.G. and A.B. Schwartz, Katalysator und dessen verwendung Catalyst and its use. 1978, German Patent and Trade Mark Office.
44.Kaeding, W.W., Methanol conversion to para-xylene using a zeolite catalyst containing an oxide of boron, magnesium, phosphorus, or mixtures. 1978, Google Patents.
45.Ono, Y., H. Adachi, and Y. Senoda, Selective conversion of methanol into aromatic hydrocarbons over zinc-exchanged ZSM-5 zeolites. Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 1988. 84(4): p. 1091-1099.
46.Wang, J.-y., et al., CONVERSION OF LOWER ALCOHOLS INTO AROMATICS OVER CATION-MODIFIED HZSM-5 ZEOLITES [J]. Chinese Journal of Catalysis, 1993. 3: p. 012.
47.Ono, Y., et al., Ag-ZSM-5 as a catalyst for aromatization of alkanes, alkenes, and methanol, in Studies in Surface Science and Catalysis. 1994, Elsevier. p. 1773-1780.
48.Freeman, D., R.P. Wells, and G.J. Hutchings, Methanol to hydrocarbons: enhanced aromatic formation using a composite Ga2O3–H-ZSM-5 catalyst. Chemical Communications, 2001(18): p. 1754-1755.
49.Freeman, D., R.P. Wells, and G.J. Hutchings, Conversion of methanol to hydrocarbons over Ga2O3/H-ZSM-5 and Ga2O3/WO3 catalysts. Journal of Catalysis, 2002. 205(2): p. 358-365.
50.Barthos, R., et al., Aromatization of methanol and methylation of benzene over Mo2C/ZSM-5 catalysts. Journal of Catalysis, 2007. 247(2): p. 368-378.
51.Lopez-Sanchez, J.A., et al., Reactivity of Ga 2 O 3 clusters on zeolite ZSM-5 for the conversion of methanol to aromatics. Catalysis letters, 2012. 142(9): p. 1049-1056.
52.Niu, X., et al., Influence of preparation method on the performance of Zn-containing HZSM-5 catalysts in methanol-to-aromatics. Microporous and Mesoporous Materials, 2014. 197: p. 252-261.
53.Mintova, S., J.-P. Gilson, and V. Valtchev, Advances in nanosized zeolites. Nanoscale, 2013. 5(15): p. 6693-6703.
54.Majano, G., et al., Seed-induced crystallization of nanosized Na-ZSM-5 crystals. Industrial & engineering chemistry research, 2009. 48(15): p. 7084-7091.
55.Xue, T., et al., Seed-induced synthesis of mesoporous ZSM-5 aggregates using tetrapropylammonium hydroxide as single template. Microporous and Mesoporous Materials, 2012. 156: p. 97-105.
56.Serrano, D., et al., Molecular and meso-and macroscopic properties of hierarchical nanocrystalline ZSM-5 zeolite prepared by seed silanization. Chemistry of Materials, 2009. 21(4): p. 641-654.
57.Koo, J.-B., et al., Direct synthesis of carbon-templating mesoporous ZSM-5 using microwave heating. Journal of Catalysis, 2010. 276(2): p. 327-334.
58.Ng, E.P., et al., Micro‐to Macroscopic Observations of MnAlPO‐5 Nanocrystal Growth in Ionic‐Liquid Media. Chemistry-A European Journal, 2010. 16(43): p. 12890-12897.
59.Ren, N., et al., Controllable and SDA-free synthesis of sub-micrometer sized zeolite ZSM-5. Part 1: Influence of alkalinity on the structural, particulate and chemical properties of the products. Microporous and Mesoporous Materials, 2011. 139(1): p. 197-206.
60.Ren, N., et al., Controllable and SDA-free synthesis of sub-micrometer sized zeolite ZSM-5. Part 2: Influence of sodium ions and ageing of the reaction mixture on the chemical composition, crystallinity and particulate properties of the products. Microporous and Mesoporous Materials, 2012. 147(1): p. 229-241.
61.Bjørgen, M., et al., Methanol to gasoline over zeolite H-ZSM-5: Improved catalyst performance by treatment with NaOH. Applied Catalysis A: General, 2008. 345(1): p. 43-50.
62.Rownaghi, A.A. and J. Hedlund, Methanol to gasoline-range hydrocarbons: Influence of nanocrystal size and mesoporosity on catalytic performance and product distribution of ZSM-5. Industrial & Engineering Chemistry Research, 2011. 50(21): p. 11872-11878.
63.Shen, K., et al., Centrifugation-free and high yield synthesis of nanosized H-ZSM-5 and its structure-guided aromatization of methanol to 1, 2, 4-trimethylbenzene. Journal of Materials Chemistry A, 2014. 2(46): p. 19797-19808.
64.Larkin, P., Infrared and Raman spectroscopy: principles and spectral interpretation. 2017: Elsevier.
65.Monqueca, R., et al., Analytical method for the determination of intra- and extraframework gallium species in zeolite catalyst. Zeolites, 1992. 12(7): p. 806-809.
66.Gao, Y., et al., Modified seeding method for preparing hierarchical nanocrystalline ZSM-5 catalysts for methanol aromatisation. Microporous and Mesoporous Materials, 2016. 226: p. 251-259.
67.Groen, J.C. and J. Pérez-Ramı́rez, Critical appraisal of mesopore characterization by adsorption analysis. Applied Catalysis A: General, 2004. 268(1): p. 121-125.
68.Su, X., et al., Synthesis of nanosized HZSM-5 zeolites isomorphously substituted by gallium and their catalytic performance in the aromatization. Chemical Engineering Journal, 2016. 293: p. 365-375.
69.Brunner, E., et al., Magic-angle-spinning NMR studies of acid sites in zeolite H-ZSM-5. Journal of Catalysis, 1991. 127(1): p. 34-41.
70.Freude, e.D. and J. Haase, Quadrupole effects in solid-state nuclear magnetic resonance, in Special Applications. 1993, Springer. p. 1-90.
71.Bayense, C.R., et al., Determination of gallium in H (Ga) ZSM5 zeolites by gallium-71 MAS NMR spectroscopy. The Journal of Physical Chemistry, 1992. 96(2): p. 775-782.
72.Playford, H.Y., et al., Characterization of Structural Disorder in γ-Ga2O3. The Journal of Physical Chemistry C, 2014. 118(29): p. 16188-16198.
73.Bigey, C. and B.L. Su, Propane as alkylating agent for alkylation of benzene on HZSM-5 and Ga-modified HZSM-5 zeolites. Journal of Molecular Catalysis A: Chemical, 2004. 209(1): p. 179-187.
74.Al-majnouni, K.A., et al., High-Temperature Decomposition of Brønsted Acid Sites in Gallium-Substituted Zeolites. The Journal of Physical Chemistry C, 2010. 114(45): p. 19395-19405.
75.Fang, Y., et al., Aromatization over nanosized Ga-containing ZSM-5 zeolites prepared by different methods: Effect of acidity of active Ga species on the catalytic performance. Journal of Energy Chemistry, 2017. 26(4): p. 768-775.
76.Kofke, T.J.G., R.J. Gorte, and W.E. Farneth, Stoichiometric adsorption complexes in H-ZSM-5. Journal of Catalysis, 1988. 114(1): p. 34-45.
77.Chal, R., et al., Overview and industrial assessment of synthesis strategies towards zeolites with mesopores. ChemCatChem, 2011. 3(1): p. 67-81.
78.Kanezashi, M., et al., Characteristics of ammonia permeation through porous silica membranes. AIChE journal, 2010. 56(5): p. 1204-1212.
79.Bobonich, F.M., Crystallization of zeolites as formation of inclusion compounds. Theoretical and Experimental Chemistry, 1994. 30(3): p. 106-116.
80.Segawa, K. and T. Hiroyasu, Highly selective methylamine synthesis over modified mordenite catalysts. Journal of Catalysis, 1991. 131(2): p. 482-490.
81.Zhang, Y., et al., Cadmium Modified HZSM-5: A Highly Efficient Catalyst for Selective Transformation of Methanol to Aromatics. Industrial & Engineering Chemistry Research, 2017. 56(44): p. 12508-12519.
82.Lai, P.-C., et al., Methanol aromatization over Ga-doped desilicated HZSM-5. RSC Advances, 2016. 6(71): p. 67361-67371.
83.Lai, P.C., et al., Methanol Conversion to Aromatics over Ga–supported HZSM‐5 with Evolved Meso‐ and Microporosities by Desilication. ChemistrySelect, 2016. 1(20): p. 6335-6344.
84.Bjørgen, M., et al., Methanol to gasoline over zeolite H-ZSM-5: Improved catalyst performance by treatment with NaOH. Applied Catalysis A: General, 2008. 345(1): p. 43-50.
85.Zhang, G.Q., et al., Conversion of Methanol to Light Aromatics on Zn-Modified Nano-HZSM-5 Zeolite Catalysts. Industrial & Engineering Chemistry Research, 2014. 53(39): p. 14932-14940.
86.Yu, L., et al., Transformation of Isobutyl Alcohol to Aromatics over Zeolite-Based Catalysts. ACS Catalysis, 2012. 2(6): p. 1203-1210.
87.Qian, W. and F. Wei, RECTOR TECHNOLOGY FOR METHANOL TO AROMATICS. Multiphase Reactor Engineering for Clean and Low-Carbon Energy Applications, 2017: p. 295.
88.Schulz, H., “Coking” of zeolites during methanol conversion: Basic reactions of the MTO-, MTP- and MTG processes. Catal. Today, 2010. 154(3–4): p. 183-194.
89.Mintova, S., M. Jaber, and V. Valtchev, Nanosized microporous crystals: emerging applications. Chemical Society Reviews, 2015. 44(20): p. 7207-7233.
90.van Donk, S., et al., Generation, Characterization, and Impact of Mesopores in Zeolite Catalysts. Catalysis Reviews, 2003. 45(2): p. 297-319.
91.Khare, R. and A. Bhan, Mechanistic studies of methanol-to-hydrocarbons conversion on diffusion-free MFI samples. Journal of Catalysis, 2015. 329: p. 218-228.
92.Schulz, H., “Coking” of zeolites during methanol conversion: Basic reactions of the MTO-, MTP- and MTG processes. Catalysis Today, 2010. 154(3–4): p. 183-194.
93.Cheng, Y.-T. and G.W. Huber, Chemistry of Furan Conversion into Aromatics and Olefins over HZSM-5: A Model Biomass Conversion Reaction. ACS Catalysis, 2011. 1(6): p. 611-628.