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摘要: 水热晶化一步合成了BHZSM-5分子筛，投料SiO2/Al2O3=100、200，其中，B2O3/Al2O3=1，研究了其甲醇制丙烯（MTP）催化活性。硼改性提高了丙烯选择性，并有利于稳定活性。硼修饰引起合成样品的强B酸量减少；水热（480℃）环境条件下，BHZSM-5的强B酸量保留量约50%，相比HZSM-5，酸性位点保留较多，显示增强的水热稳定性；同时骨架Al分布发生了变化：位于晶体直孔道和正弦孔道的Al稳定，孔道交叉口的Al易于脱除，有利于基于烯烃循环机理的MTP活性。水热处理空速由1 h-1增加到9 h-1，B酸量进一步下降，晶体孔道交叉口的Al脱除更多。Abstract: BHZSM-5 zeolite was synthesized using one-step hydrothermal crystallization by changing SiO2/Al2O3 (100 and 200) with B2O3/Al2O3=1. The catalytic activity for methanol to propylene (MTP) was studied. Boron modification lead to increased propylene selectivity and improved stability. Boron modification reduced the amount of the strong Brønsted (B) acid sites. Subjected to hydrothermal treatment at 480 ℃, BHZSM-5 remained 50% of the amount of the strong B acid sites, higher than that of HZSM-5, showing enhanced hydrothermal stability. The distribution of the framework Al also changed. The Al located in the straight and the sinusoidal channels of the ZSM-5 crystal was stable whereas those at the channel intersections was easy to be removed, favoring the MTP activity via the olefin cycle mechanism. As the hydrothermal treatment velocity was increased from 1 h-1 to 9 h-1, the B acid sites amount of the BHZSM-5 further decreased and more Al at the intersections was removed.
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Key words:
- boron modification /
- HZSM-5 /
- methanol to propylene /
- Brønsted acidity /
- Al distribution
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表 1 样品命名及投料配比
Table 1 Names and charging compositions of synthetic samples
Name SiO2 /Al2O3 B2O3 /Al2O3 SiO2 /(Al2O3+B2O3) BHZ-5-100 100 1 50 HZ-5-100 100 0 100 BHZ-5-200 200 1 100 HZ-5-200 200 0 200 
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表 2 合成样品的Py-FTIR酸性
Table 2 Acidity of synthetic samples derived from Py-FTIR
Sample B /(μmol·g-1) Total B/(μmol·g-1) Total L /(μmol·g-1) weak medium strong strong BHZ-5-100 225 107 96 428 12 HZ-5-100 102 89 174 365 55 BHZ-5-200 178 136 51 365 10 HZ-5-200 123 56 94 273 41
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表 3 样品的孔结构
Table 3 Textural properties of different samples
Sample WSHV/h-1 Crystallinity /% ABET/(m2·g-1) vtotal/(cm3·g-1) vmicro/(cm3·g-1) vmeso/(cm3·g-1) BHZ-5-100 1 108 352 0.206 0.137 0.069 HZ-5-100 1 163 359 0.231 0.141 0.090 BHZ-5-100 0 99 395 0.201 0.142 0.059 HZ-5-100 0 100 388 0.200 0.146 0.054 BHZ-5-100 9 106 349 0.199 0.136 0.063 HZ-5-100 9 166 347 0.214 0.135 0.079
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表 4 样品的峰面积
Table 4 Proportions of deconvolution peak areas for different samples
Samples WSHV/h-1 Proportions /% Al(d)/Al(c) Al(e) 58 Al(d) 56 Al(c) 54 Al(b) 53 Al(a) 52 BHZ-5-100 1 12 30 25 17 15 1.20 HZ-5-100 1 10 25 23 19 21 1.08 BHZ-5-200 1 6 28 23 16 26 1.21 HZ-5-200 1 4 28 27 20 21 1.03 BHZ-5-100 0 4 29 29 18 19 1.00 HZ-5-100 0 4 29 23 18 25 1.26 BHZ-5-200 0 4 29 31 4 31 0.93 HZ-5-200 0 4 29 29 4 33 1.00 BHZ-5-100 9 13 31 23 16 16 1.37 HZ-5-100 9 9 26 24 20 19 1.08 BHZ-5-200 9 5 30 24 16 24 1.25 HZ-5-200 9 5 27 25 20 23 1.08
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表 5 样品的Py-FTIR酸性
Table 5 Acidity of samples derived from Py-FTIR
Sample WSHV /h-1 B /(μmol·g-1) Total B /(μmol·g-1) Total L /(μmol·g-1) weak medium strong strong BHZ-5-100 1 120 22 49 191 2 HZ-5-100 1 93 31 40 164 38 BHZ-5-200 1 69 25 24 118 0 HZ-5-200 1 49 34 22 105 24 BHZ-5-100 9 122 36 34 192 2 HZ-5-100 9 53 42 31 126 29 BHZ-5-200 9 98 2 51 151 0 HZ-5-200 9 27 31 11 69 21
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表 6 水热处理样品的MTP产物选择性
Table 6 Product selectivity of MTP on hydrothermally treated samples
Samples WSHV /h-1 Selectivity s/% C3=/C2= HTI C1 C2= C2 C3= C3 C4= C5+ BHZ-5-100 1 5.0 26.2 0.3 31.1 3.5 8.8 16.1 1.18 0.31 HZ-5-100 1 4.3 20.4 0.2 27.5 2.5 7.3 20.2 1.35 0.32 BHZ-5-200 1 2.6 26.9 0.2 36.2 2.3 10.4 14.5 1.35 0.20 HZ-5-200 1 2.8 23.9 0.2 36.3 2.2 9.6 17.2 1.52 0.22 BHZ-5-100 0 8.3 28.7 0.7 26.0 5.1 7.1 17.2 0.91 0.36 HZ-5-100 0 9.8 27.4 0.7 22.6 5.4 6.1 21.1 0.82 0.43 BHZ-5-200 0 6.2 28.3 0.4 30.5 3.7 7.7 17.5 1.08 0.25 HZ-5-200 0 7.8 28.4 0.6 27.7 5.1 7.7 17.0 0.97 0.31 BHZ-5-100 9 4.4 25.3 0.3 33.6 2.6 9.2 17.1 1.33 0.24 HZ-5-100 9 4.9 25.5 0.2 32.9 2.8 9.5 16.1 1.29 0.26 BHZ-5-200 9 2.3 27.6 0.3 37.4 3.3 9.5 11.2 1.35 0.25 HZ-5-200 9 1.9 23.8 0.3 37.4 3.1 10.0 15.8 1.52 0.23 time-on-stream: 6 h; methanol conversion: 100%
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