Methanol converting to propylene on weakly acidic and hierarchical porous MFI zeolite
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摘要: 使用葡萄糖辅助模板合成了H-[B,Al]-ZSM-5 沸石并用于催化甲醇转化制丙烯。优越的丙烯选择性和活性持久性关联于有利于丙烯生成的高的弱酸/强酸比例以及有利于改善反应物扩散的防止快速积炭的高的介孔率。较多的位于MFI沸石直/正弦孔道的骨架铝增加了产物丙烯/乙烯比归因于促进的丙烯生成。低的酸密度有助于高的丙烯/乙烯比。B/Al比为2 且(Al2+B2)/Si 比为0.01的HZ5-G-2B 样品用于甲醇制丙烯反应,在原料CH3OH/H2O(1∶1.2) 重时空速为1.8 h−1 、480 °C反应条件下,丙烯选择性为51.6%,
${\rm{C}}_{2-4}^ {=} $ 烯烃选择性为83.7%,甲醇完全转化。丙烯/乙烯比为2。催化活性保持580 h稳定。Abstract: H-[B,Al]-ZSM-5 zeolites were synthesized with glucose as assistant template to catalyze methanol converting toward propylene. The superior catalytic performance in terms of the propylene selectivity and the activity longevity was related to high ratio of weak acid to strong acid for favorable production of propylene and to high mesoporosity for improved diffusion of reactants and prevention from fast coking. More framework Al siting in the straight or sinusoidal channels of the MFI zeolite could also enhance the propylene/ethylene ratio due to the promotional effect on propylene formation. Low weak acid density was conducive to the production of high propylene/ethylene ratio. With the B/Al ratio of 2 and the (Al2+B2)/Si ratio of 0.01, HZ5-G-2B was applied in the methanol to propylene reaction at CH3OH/H2O (1∶1.2) WHSV of 1.8 h−1 and 480 °C. Propylene selectivity of 51.6%, the${\rm{C}}_{{2-4}}^ {=} $ selectivity of 83.7% and complete conversion of methanol were achieved. The propylene/ethylene ratio was 2. The catalytic activity kept stable for 580 h.-
Key words:
- H-[B /
- Al]-ZSM-5 /
- weak acidity /
- mesoporosity /
- MTP
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Table 1 Textural properties of synthetic samples
Sample Measured molar ratio* Crysta-llinity/% BET area/(m2·g−1) Pore volume/(cm3·g−1) Mesoporosity/% Si/Al2 B/Al (Al2+B2)/Si micro meso total micro meso total HZ5-G-9B 220 5.1 0.030 98 279 58 337 0.12 0.14 0.26 53 HZ5-G-2B 230 1.3 0.010 95 254 72 326 0.11 0.30 0.41 73 HZ5-G-1B 224 0.7 0.008 89 295 48 343 0.13 0.23 0.36 63 HZ5-G 218 0 0.005 96 316 57 373 0.14 0.10 0.22 45 HZ5-1B − − − − 382 33 415 0.17 0.02 0.19 10 HZ5 220 0 0.005 − − − − − − − − *: charged Si/Al2=200, B/Al=9, 2, 1, 0, 0 Table 2 Percentage of deconvoluted peak areas for synthetic samples
Sample Percentage/% Al56/Al54 52 53 54 56 58 HZ5-G-9B 12 13 20 47 8 2.04 HZ5-G-2B 8 12 23 45 9 2.03 HZ5-G-1B 10 13 25 42 10 1.68 HZ5-G 12 14 30 31 12 1.03 Table 3 Surface acidity of synthetic samples
Sample Temp./°C Acid amount/(μmol NH3·g−1) W/S
ratioWeak acid density/
(μmol·m−2)Acid/(μmol·g−1) weak strong weak strong B L HZ5-G-9B 170 373 213 38 5.6 0.63 130 3 HZ5-G-2B 175 374 167 41 4.1 0.51 126 3 HZ5-G-1B 174 369 139 40 3.5 0.41 94 4 HZ5-G 168 362 92 42 2.2 0.25 80 1 Table 4 Catalytic activity of synthetic samples for MTP
Sample TOS/h Product selectivity/% P/E HTI C1 ${\rm{C}}_{2}^ {=} $ C2 ${\rm{C}}_{3}^ {=} $ C3 ${\rm{C}}_{4}^ {=} $ C4 ${\rm{C}}_{5+} $ ${\rm{C} }_{{2-4}}^ {=}$ HZ5-G-9B 480 3.4 25.4 0.3 47.9 3.4 10.4 0.7 7.1 83.7 1.9 0.05 HZ5-G-2B 580 3.7 22.8 0.3 50.1 2.1 11.6 0.7 6.4 84.5 2.2 0.04 HZ5-G-1B 230 4.3 24.1 0.5 44.4 3.3 11.4 0.6 7.6 79.9 1.8 0.05 HZ5-G 80 1.8 25.2 0.6 41.1 4.3 12.6 0.7 13.5 78.9 1.6 0.07 HZ5 23 6.5 24.9 0.5 38.9 4.9 11.5 0.8 15.7 75.3 1.5 0.08 -
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