介孔结构和助剂Zn对不同晶粒大小ZSM-5催化甲醇制芳烃反应性能的影响
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摘要
通过碱处理和添加助剂Zn对微米ZSM-5和纳米ZSM-5进行改性,获得具有不同孔结构和酸性质的催化剂。采用氮气吸附、X射线衍射、透射电镜、氨气程序升温脱附(NH_3-TPD)和热重(TG)技术对不同催化剂进行表征,结合催化性能评价,考察晶粒尺寸、介孔结构和Zn助剂对其催化甲醇制芳烃(MTA)反应性能的影响。结果表明,碱处理引入介孔后,孔体积均增大,总酸量都降低;微米催化剂外表面积显著增加,但纳米催化剂外表面积却有所下降;负载金属Zn后,比表面积、结晶度和总酸量都降低。在P=0.5MPa、T=430℃、WHSV=2h-1的反应条件下,负载Zn的微米催化剂由于具有较高的酸量,其芳烃与苯、甲苯和二甲苯(BTX)选择性最高,分别为85.11%和66.85%,但是稳定性较差,催化寿命仅为12h。但相较于未改性的纳米ZSM-5原粉来说,碱处理后又负载Zn的催化剂,液烃中芳烃选择性从纳米原粉的65.20%增加到80.82%,BTX选择性从纳米原粉的42.30%提高到49.56%,而在甲醇进样量增加4倍,即WHSV=8h-1时,催化剂仍显示出较好的稳定性,寿命可达84h。可见,在小晶粒ZSM-5上碱处理扩孔并引入Zn助剂可以有效提高甲醇制芳烃反应性能。
ZSM-5 catalysts with different pore structures and acidities were modified by alkali treatment and Zn introduction. The obtained catalysts were characterized by N_2 adsorption, XRD, TEM, NH_3-TPD and TG techniques, and the influences of crystal size, mesoporous structure and Zn metal additive on the catalytic performance of ZSM-5 for conversion of methanol to aromatics(MTA) were investigated in addition to the catalyst evaluation. The results indicated that after the formation of mesopore via alkali treatment, the pore volume of the catalysts increased, and the total acid amount decreased. The external surface area of the micro-ZSM-5 increased significantly but that of the nano-ZSM-5 decreased after alkali treatment. The surface area, crystallinity and total acid amount of ZSM-5 were decreased after the introduction of Zn species. MTA reaction was carried out in a fixed-bed reactor at 430℃ and WHSV of2 h-1 under 0.5 MPa and the Zn-loaded micron catalyst exhibited high acid amount, high aromatic selectivity of 85.11% and BTX selectivity of 66.85% in liquid hydrocarbons, but a short catalytic lifetime of only 12 hours. Compared with the unmodified nano-ZSM-5, the Zn-promoted mesoporous nano-ZSM-5 increased the aromatic selectivity from 65.20% to 80.82%, and the BTX value from 42.30% to 49.56%.The catalyst still displayed good catalytic stability when space velocity was up to 8 h-1 and the catalytic lifetime could reach 84 h. This work demonstrated that mesopore fabricating of nano-ZSM-5 catalyst by alkali treatment and then introducing Zn could effectively improve its MTA performance.
ZSM-5 catalysts with different pore structures and acidities were modified by alkali treatment and Zn introduction. The obtained catalysts were characterized by N_2 adsorption, XRD, TEM, NH_3-TPD and TG techniques, and the influences of crystal size, mesoporous structure and Zn metal additive on the catalytic performance of ZSM-5 for conversion of methanol to aromatics(MTA) were investigated in addition to the catalyst evaluation. The results indicated that after the formation of mesopore via alkali treatment, the pore volume of the catalysts increased, and the total acid amount decreased. The external surface area of the micro-ZSM-5 increased significantly but that of the nano-ZSM-5 decreased after alkali treatment. The surface area, crystallinity and total acid amount of ZSM-5 were decreased after the introduction of Zn species. MTA reaction was carried out in a fixed-bed reactor at 430℃ and WHSV of2 h-1 under 0.5 MPa and the Zn-loaded micron catalyst exhibited high acid amount, high aromatic selectivity of 85.11% and BTX selectivity of 66.85% in liquid hydrocarbons, but a short catalytic lifetime of only 12 hours. Compared with the unmodified nano-ZSM-5, the Zn-promoted mesoporous nano-ZSM-5 increased the aromatic selectivity from 65.20% to 80.82%, and the BTX value from 42.30% to 49.56%.The catalyst still displayed good catalytic stability when space velocity was up to 8 h-1 and the catalytic lifetime could reach 84 h. This work demonstrated that mesopore fabricating of nano-ZSM-5 catalyst by alkali treatment and then introducing Zn could effectively improve its MTA performance.
引文
[1]汪哲明,陈希强,许烽,等.甲醇制芳烃催化剂研究进展[J].化工进展, 2016, 35(5):1433-1439.WANG Z M, CHEN X Q, XU F, et al. Advance in the research and development of methanol to aromatic catalysts[J]. Chemical Industry and Engineering Progress, 2016, 35(5):1433-1439.
[2]陈庆龄,杨为民,滕加伟,等.中国石化煤化工技术最新进展[J].催化学报, 2013, 34(1):217-224.CHEN Q L, YANG W M, TENG J W, et al. Recent advances in coal to chemicals technology developed by Sinopec[J]. Chinese Journal of Catalysis, 2013, 34(1):217-224.
[3] ZHANG G Q, TING B, CHEN T F, et al. Conversion of methanol to light aromatics on Zn-modified nano-HZSM-5 zeolite catalysts[J].Industrial&Engineering Chemistry Research, 2014, 53(39):14932-14940.
[4] FEI W, WEI Y X, GUO M X. Atomic layer deposition of zinc oxide on HZSM-5 template and its methanol aromatization performance[J].Catalysis Letters, 2015, 145(3):860-867.
[5] LIANG T G, CHEN J L, QIN Z F, et al. Conversion of methanol to olefins over H-ZSM-5 zeolite:reaction pathway is related to the framework aluminum siting[J]. ACS Catalysis, 2016, 6(11):7311-7325.
[6] LOSCH P, PINAR A B, WILLINGER M G, et al. H-ZSM-5 zeolite model crystals:structure-diffusion-activity relationship in methanolto-olefins catalysis[J]. Journal of Catalysis, 2017, 345:11-23.
[7]潘红艳,田敏,何志艳,等.甲醇制烯烃用ZSM-5分子筛的研究进展[J].化工进展, 2014, 33(10):2625-2633.PAN H Y, TIAN M, HE Z Y, et al. Advances in research on modified ZSM-5 molecular sieves for conversion of methanol to olefins[J].Chemical Industry and Engineering Progress, 2014, 33(10):2625-2633.
[8] FIROOZI M, BAGHALHA M, ASADI M. The effect of micro and nano particle sizes of H-ZSM-5 on the selectivity of MTP reaction[J].Catalysis Communications, 2009, 10(12):1582-1585.
[9] NIU X J, GAO J, WANG K, et al. Influence of crystal size on the catalytic performance of H-ZSM-5 and Zn/H-ZSM-5 in the conversion of methanol to aromatics[J]. Fuel Processing Technology,2017, 157:99-107.
[10] SHAO J, FU T J, CHANG J W, et al. Effect of ZSM-5 crystal size on its catalytic properties for conversion of methanol to gasoline[J].Journal of Fuel Chemistry and Technology, 2017, 45(1):75-83.
[11] XING L Y, WEI Z H, WEN Z H, et al. Catalytic study for methanol aromatization over hierarchical ZSM-5 zeolite synthesized by kaolin[J]. Petroleum Science&Technology, 2017, 35(24):2235-2240.
[12] FENG W, GAO X F, DING C M, et al. Effect of weak base modification on ZSM-5 catalyst for methanol to aromatics[J]. Applied Organometallic Chemistry, 2017, 31(6):3625-3631.
[13] QI R Y, FU T J, WAN W L, et al. Pore fabrication of nano-ZSM-5zeolite by internal desilication and its influence on the methanol to hydrocarbon reaction[J]. Fuel Processing Technology, 2016, 155:191-199.
[14] INOUE Y, NAKASHIRO K, ONO Y. Selective conversion of methanol into aromatic hydrocarbons over silver-exchanged ZSM-5 zeolites[J].Microporous Materials, 1995, 4(5):379-383.
[15] TIAN T, QIAN W Z, TANG X P, et al. Deactivation of Ag/ZSM-5catalyst in the aromatization of methanol[J]. Acta Physico-Chimica Sinica, 2010, 26(12):3305-3309.
[16] LOPEZ-SANCHEZ J A, CONTE M, LANDON P, et al. Reactivity of Ga2O3clusters on zeolite ZSM-5 for the conversion of methanol to aromatics[J]. Catalysis Letters, 2012, 142(9):1049-1056.
[17] AL-YASSIR N, AKHTAR M N, OGUNRONBI K, et al. Synthesis of stable H-galloaluminosilicate MFI with hierarchical pore architecture by surfactant-mediated base hydrolysis, and their application in propane aromatization[J]. Journal of Molecular Catalysis A:Chemical,2012, 360:1-15.
[18] MENTZEL U V, HOJHOLT K T, HOLM M S, et al. Conversion of methanol to hydrocarbons over conventional and mesoporous H-ZSM-5 and H-Ga-MFI:major differences in deactivation behavior[J].Applied Catalysis A:General, 2012, 417-418:290-297.
[19] WANG N, QIAN W, SHEN K, et al. Bayberry-like ZnO/MFI zeolite as high performance methanol-to-aromatics catalyst[J]. Chemical Communications, 2015, 52(10):2011-2014.
[20] XIN Y B, QI P Y, DUAN X P, et al. Enhanced performance of Zn-Sn/HZMS-5 catalyst for the conversion of methanol to aromatics[J].Catalysis Letters, 2013, 143(8):798-806.
[21] COQUEBLIN H, RICHARD A, UZIO D, et al. Effect of the metal promoter on the performances of H-ZSM5 in ethylene aromatization[J].Catalysis Today, 2016, 289:62-69.
[22] NI Y M, SUN A M, WU X L, et al. The preparation of nano-sized H[Zn, Al]ZSM-5 zeolite and its application in the aromatization of methanol[J]. Microporous&Mesoporous Materials, 2011, 143(2/3):435-442.
[23] BI Y, WANG Y L, CHEN X, et al. Methanol aromatization over HZSM-5 catalysts modified with different zinc salts[J]. Chinese Journal of Catalysis, 2014, 35(10):1740-1751.
[24] NIU X J, GAO J, MIAO Q, et al. Influence of preparation method on the performance of Zn-containing HZSM-5 catalysts in methanol-toaromatics[J]. Microporous&Mesoporous Materials, 2014, 197:252-261.
[25] WANG J Y, LI W H, HU J X. Study of methanol to aromatics on ZnHZSM-5 catalyst[J]. Journal of Fuel Chemistry&Technology, 2009,37(5):607-612.
[26] ZHOU J, HUA Z L, L Z C, et al. Direct synthetic strategy of mesoporous ZSM-5 zeolites by using conventional block copolymer templates and the improved catalytic properties[J]. ACS Catalysis,2011, 1(4):287-291.
[27] KIM Jeongnam, CHOI Minkee, RYOO Ryong. Effect of mesoporosity against the deactivation of MFI zeolite catalyst during the methanolto-hydrocarbon conversion process[J]. Journal of Catalysis, 2010, 269(1):219-228.
[28] AHMADPOUR J, TAGHIZADEH M. Catalytic conversion of methanol to propylene over high-silica mesoporous ZSM-5 zeolites prepared by different combinations of mesogenous templates[J]. Journal of Natural Gas Science&Engineering, 2015, 23:184-194.
[29] WANG Y X, SONG J J, BAXTER N C, et al. Synthesis of hierarchical ZSM-5 zeolites by solid-state crystallization and their catalytic properties[J]. Journal of Catalysis, 2017, 349:53-65.
[30] GROEN J C, PEFFER L A, MOULIJN J A, et al. Mechanism of hierarchical porosity development in MFI zeolites by desilication:the role of aluminium as a pore-directing agent[J]. Chemistry European Journal, 2005, 11(17):4983-4994.
[31] FU T J, CHANG J W, SHAO J, et al. Fabrication of a nano-sized ZSM-5 zeolite with intercrystalline mesopores for conversion of methanol to gasoline[J]. Journal of Energy Chemistry, 2017, 26(1):139-146.
[32] NI Y M, SUN A M, WU X L, et al. Aromatization of methanol over La/Zn/HZSM-5 catalysts[J]. Chinese Journal of Chemical Engineering,2011, 19(3):439-445.
[33] WANG X X, ZHANG J F, ZHANG T, et al. Mesoporous ZnZSM-5zeolites synthesized by onestep desilication and reassembly:a durable catalyst for methanol aromatization[J]. RSC Advances, 2016, 6(28):23428-23437.
[34] ZHANG J G, QIAN W Z, KONG C Y, et al. Increasing para-xylene selectivity in making aromatics from methanol with a surface-modified Zn/P/ZSM-5 catalyst[J]. ACS Catalysis, 2015, 5(5):2982-2988.
[35] ROWNAGHI A A, REZAEI F, HEDLUND J. Yield of gasoline-range hydrocarbons as a function of uniform ZSM-5 crystal size[J]. Catalysis Communications, 2011, 14(1):37-41.
[36] LI J H, TONG K, XI Z W, et al. Highly-efficient conversion of methanol to p-xylene over shape-selective Mg-Zn-Si-HZSM-5catalyst with fine modification of pore-opening and acidic properties[J]. Catalysis Science&Technology, 2016, 6(13):4802-4813.
[37]刘维桥,雷卫宁,尚通明,等. Zn对HZSM-5分子筛催化剂物化及甲醇芳构化反应性能的影响[J].化工进展, 2011, 30(9):1967-1971.LIU W Q, LEI W N, SHANG T M, et al. Physicochemical and methanol aromatization property of HZSM-5 catalyst promoted by Zn[J]. Chemical Industry and Engineering Progress, 2011, 30(9):1967-1971.
[38] YARIPOUR F, SHARIATINIA Z, SAHEBDELFAR S, et al. Effect of boron incorporation on the structure, products selectivities and lifetime of H-ZSM-5 nanocatalyst designed for application in methanol-toolefins(MTO)reaction[J]. Microporous&Mesoporous Materials, 2015,203:41-53.
[39] PINILLA-HERRERO I, BORFECCHIA E, HOLZINGER J, et al.High Zn/Al ratios enhance dehydrogenation vs hydrogen transfer reactions of Zn-ZSM-5 catalytic systems in methanol conversion to aromatics[J]. Journal of Catalysis, 2018, 362:146-163.
[2]陈庆龄,杨为民,滕加伟,等.中国石化煤化工技术最新进展[J].催化学报, 2013, 34(1):217-224.CHEN Q L, YANG W M, TENG J W, et al. Recent advances in coal to chemicals technology developed by Sinopec[J]. Chinese Journal of Catalysis, 2013, 34(1):217-224.
[3] ZHANG G Q, TING B, CHEN T F, et al. Conversion of methanol to light aromatics on Zn-modified nano-HZSM-5 zeolite catalysts[J].Industrial&Engineering Chemistry Research, 2014, 53(39):14932-14940.
[4] FEI W, WEI Y X, GUO M X. Atomic layer deposition of zinc oxide on HZSM-5 template and its methanol aromatization performance[J].Catalysis Letters, 2015, 145(3):860-867.
[5] LIANG T G, CHEN J L, QIN Z F, et al. Conversion of methanol to olefins over H-ZSM-5 zeolite:reaction pathway is related to the framework aluminum siting[J]. ACS Catalysis, 2016, 6(11):7311-7325.
[6] LOSCH P, PINAR A B, WILLINGER M G, et al. H-ZSM-5 zeolite model crystals:structure-diffusion-activity relationship in methanolto-olefins catalysis[J]. Journal of Catalysis, 2017, 345:11-23.
[7]潘红艳,田敏,何志艳,等.甲醇制烯烃用ZSM-5分子筛的研究进展[J].化工进展, 2014, 33(10):2625-2633.PAN H Y, TIAN M, HE Z Y, et al. Advances in research on modified ZSM-5 molecular sieves for conversion of methanol to olefins[J].Chemical Industry and Engineering Progress, 2014, 33(10):2625-2633.
[8] FIROOZI M, BAGHALHA M, ASADI M. The effect of micro and nano particle sizes of H-ZSM-5 on the selectivity of MTP reaction[J].Catalysis Communications, 2009, 10(12):1582-1585.
[9] NIU X J, GAO J, WANG K, et al. Influence of crystal size on the catalytic performance of H-ZSM-5 and Zn/H-ZSM-5 in the conversion of methanol to aromatics[J]. Fuel Processing Technology,2017, 157:99-107.
[10] SHAO J, FU T J, CHANG J W, et al. Effect of ZSM-5 crystal size on its catalytic properties for conversion of methanol to gasoline[J].Journal of Fuel Chemistry and Technology, 2017, 45(1):75-83.
[11] XING L Y, WEI Z H, WEN Z H, et al. Catalytic study for methanol aromatization over hierarchical ZSM-5 zeolite synthesized by kaolin[J]. Petroleum Science&Technology, 2017, 35(24):2235-2240.
[12] FENG W, GAO X F, DING C M, et al. Effect of weak base modification on ZSM-5 catalyst for methanol to aromatics[J]. Applied Organometallic Chemistry, 2017, 31(6):3625-3631.
[13] QI R Y, FU T J, WAN W L, et al. Pore fabrication of nano-ZSM-5zeolite by internal desilication and its influence on the methanol to hydrocarbon reaction[J]. Fuel Processing Technology, 2016, 155:191-199.
[14] INOUE Y, NAKASHIRO K, ONO Y. Selective conversion of methanol into aromatic hydrocarbons over silver-exchanged ZSM-5 zeolites[J].Microporous Materials, 1995, 4(5):379-383.
[15] TIAN T, QIAN W Z, TANG X P, et al. Deactivation of Ag/ZSM-5catalyst in the aromatization of methanol[J]. Acta Physico-Chimica Sinica, 2010, 26(12):3305-3309.
[16] LOPEZ-SANCHEZ J A, CONTE M, LANDON P, et al. Reactivity of Ga2O3clusters on zeolite ZSM-5 for the conversion of methanol to aromatics[J]. Catalysis Letters, 2012, 142(9):1049-1056.
[17] AL-YASSIR N, AKHTAR M N, OGUNRONBI K, et al. Synthesis of stable H-galloaluminosilicate MFI with hierarchical pore architecture by surfactant-mediated base hydrolysis, and their application in propane aromatization[J]. Journal of Molecular Catalysis A:Chemical,2012, 360:1-15.
[18] MENTZEL U V, HOJHOLT K T, HOLM M S, et al. Conversion of methanol to hydrocarbons over conventional and mesoporous H-ZSM-5 and H-Ga-MFI:major differences in deactivation behavior[J].Applied Catalysis A:General, 2012, 417-418:290-297.
[19] WANG N, QIAN W, SHEN K, et al. Bayberry-like ZnO/MFI zeolite as high performance methanol-to-aromatics catalyst[J]. Chemical Communications, 2015, 52(10):2011-2014.
[20] XIN Y B, QI P Y, DUAN X P, et al. Enhanced performance of Zn-Sn/HZMS-5 catalyst for the conversion of methanol to aromatics[J].Catalysis Letters, 2013, 143(8):798-806.
[21] COQUEBLIN H, RICHARD A, UZIO D, et al. Effect of the metal promoter on the performances of H-ZSM5 in ethylene aromatization[J].Catalysis Today, 2016, 289:62-69.
[22] NI Y M, SUN A M, WU X L, et al. The preparation of nano-sized H[Zn, Al]ZSM-5 zeolite and its application in the aromatization of methanol[J]. Microporous&Mesoporous Materials, 2011, 143(2/3):435-442.
[23] BI Y, WANG Y L, CHEN X, et al. Methanol aromatization over HZSM-5 catalysts modified with different zinc salts[J]. Chinese Journal of Catalysis, 2014, 35(10):1740-1751.
[24] NIU X J, GAO J, MIAO Q, et al. Influence of preparation method on the performance of Zn-containing HZSM-5 catalysts in methanol-toaromatics[J]. Microporous&Mesoporous Materials, 2014, 197:252-261.
[25] WANG J Y, LI W H, HU J X. Study of methanol to aromatics on ZnHZSM-5 catalyst[J]. Journal of Fuel Chemistry&Technology, 2009,37(5):607-612.
[26] ZHOU J, HUA Z L, L Z C, et al. Direct synthetic strategy of mesoporous ZSM-5 zeolites by using conventional block copolymer templates and the improved catalytic properties[J]. ACS Catalysis,2011, 1(4):287-291.
[27] KIM Jeongnam, CHOI Minkee, RYOO Ryong. Effect of mesoporosity against the deactivation of MFI zeolite catalyst during the methanolto-hydrocarbon conversion process[J]. Journal of Catalysis, 2010, 269(1):219-228.
[28] AHMADPOUR J, TAGHIZADEH M. Catalytic conversion of methanol to propylene over high-silica mesoporous ZSM-5 zeolites prepared by different combinations of mesogenous templates[J]. Journal of Natural Gas Science&Engineering, 2015, 23:184-194.
[29] WANG Y X, SONG J J, BAXTER N C, et al. Synthesis of hierarchical ZSM-5 zeolites by solid-state crystallization and their catalytic properties[J]. Journal of Catalysis, 2017, 349:53-65.
[30] GROEN J C, PEFFER L A, MOULIJN J A, et al. Mechanism of hierarchical porosity development in MFI zeolites by desilication:the role of aluminium as a pore-directing agent[J]. Chemistry European Journal, 2005, 11(17):4983-4994.
[31] FU T J, CHANG J W, SHAO J, et al. Fabrication of a nano-sized ZSM-5 zeolite with intercrystalline mesopores for conversion of methanol to gasoline[J]. Journal of Energy Chemistry, 2017, 26(1):139-146.
[32] NI Y M, SUN A M, WU X L, et al. Aromatization of methanol over La/Zn/HZSM-5 catalysts[J]. Chinese Journal of Chemical Engineering,2011, 19(3):439-445.
[33] WANG X X, ZHANG J F, ZHANG T, et al. Mesoporous ZnZSM-5zeolites synthesized by onestep desilication and reassembly:a durable catalyst for methanol aromatization[J]. RSC Advances, 2016, 6(28):23428-23437.
[34] ZHANG J G, QIAN W Z, KONG C Y, et al. Increasing para-xylene selectivity in making aromatics from methanol with a surface-modified Zn/P/ZSM-5 catalyst[J]. ACS Catalysis, 2015, 5(5):2982-2988.
[35] ROWNAGHI A A, REZAEI F, HEDLUND J. Yield of gasoline-range hydrocarbons as a function of uniform ZSM-5 crystal size[J]. Catalysis Communications, 2011, 14(1):37-41.
[36] LI J H, TONG K, XI Z W, et al. Highly-efficient conversion of methanol to p-xylene over shape-selective Mg-Zn-Si-HZSM-5catalyst with fine modification of pore-opening and acidic properties[J]. Catalysis Science&Technology, 2016, 6(13):4802-4813.
[37]刘维桥,雷卫宁,尚通明,等. Zn对HZSM-5分子筛催化剂物化及甲醇芳构化反应性能的影响[J].化工进展, 2011, 30(9):1967-1971.LIU W Q, LEI W N, SHANG T M, et al. Physicochemical and methanol aromatization property of HZSM-5 catalyst promoted by Zn[J]. Chemical Industry and Engineering Progress, 2011, 30(9):1967-1971.
[38] YARIPOUR F, SHARIATINIA Z, SAHEBDELFAR S, et al. Effect of boron incorporation on the structure, products selectivities and lifetime of H-ZSM-5 nanocatalyst designed for application in methanol-toolefins(MTO)reaction[J]. Microporous&Mesoporous Materials, 2015,203:41-53.
[39] PINILLA-HERRERO I, BORFECCHIA E, HOLZINGER J, et al.High Zn/Al ratios enhance dehydrogenation vs hydrogen transfer reactions of Zn-ZSM-5 catalytic systems in methanol conversion to aromatics[J]. Journal of Catalysis, 2018, 362:146-163.