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摘要: 通过浸渍法对ZSM-5进行金属M(M为Mg、Ni、Sr)改性,合成法制备了M-ZSM-5-SBA-15复合分子筛,采用XRD、N2吸附-脱附、FT-IR、NH3-TPD和Py-FTIR等技术对样品进行表征,考察了HZSM-5的硅铝比、不同金属对ZSM-5-SBA-15复合分子筛烷基化性能的影响。结果表明,HZSM-5的硅铝比为80时,ZSM-5-SBA-15复合分子筛的烷基化性能较好,Sr的引入钝化了ZSM-5-SBA-15(80)的强B酸中心,降低了B酸与L酸的比值,Sr-ZSM-5-SBA-15(80)的甲苯甲醇烷基化性能明显提高,甲苯转化率为30.15%,对二甲苯选择性为77.41%。
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关键词:
- ZSM-5-SBA-15 /
- 金属改性 /
- 烷基化 /
- 对二甲苯
Abstract: ZSM-5 was modified by metal M (M for Mg, Ni or Sr) using impregnation method first, then the micro-mesoporous composite molecular sieve of M-ZSM-5-SBA-15 was synthesized by post synthesis. The samples were characterized by means of XRD, N2 adsorption-desorption, FT-IR, NH3-TPD and Py-FTIR. The influence of silica alumina ratio of the HZSM-5 and different metals modification on alkylation performance were investigated. The results showed that the ZSM-5/SBA-15 composite molecular sieve with silica alumina ratio of 80 showed the best performance in alkylation. The introduction of Sr passivated strong Brnsted acid centers and reduced the ratio of Brnsted acid and Lewis acid of ZSM-5-SBA-15(80), resulting in good performance in alkylation with a toluene conversion of 30.15% and a p-xylene selectivity of 77.41%.-
Key words:
- ZSM-5-SBA-15 /
- metal modified /
- alkylation /
- p-xylene
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表 1 样品的甲苯甲醇烷基化性能
Table 1 Alkylation catalytic properties of the samples
Catalyst Conversion xT /% Selectivity sPX /% Yield wPX /% 400℃ 420℃ 400℃ 420℃ 400℃ 420℃ ZSM-5-SBA-15(25) 32.43 33.52 52.35 53.88 16.98 18.06 ZSM-5-SBA-15(50) 31.35 32.22 59.71 57.78 18.72 18.62 ZSM-5-SBA-15(80) 28.72 30.31 67.78 64.03 19.47 19.41 ZSM-5-SBA-15(120) 26.84 27.42 68.68 67.29 18.43 18.45 ZSM-5-SBA-15(150) 23.15 24.34 69.78 68.42 16.15 16.65 表 2 样品的甲苯甲醇烷基化性能
Table 2 Alkylation catalytic properties of the samples
Catalyst Conversion xT /% Selectivity sPX /% Yield wPX /% 400℃ 420℃ 400℃ 420℃ 400℃ 420℃ ZSM-5-SBA-15(80) 28.72 30.31 67.78 64.03 19.47 19.41 Sr-ZSM-5-SBA-15(80) 30.15 31.67 77.41 73.08 23.34 23.15 Ni-ZSM-5-SBA-15(80) 25.37 26.43 69.98 67.48 17.75 17.83 Mg-ZSM-5-SBA-15(80) 20.24 21.42 70.67 69.04 14.30 14.78 表 3 样品的结构参数
Table 3 Structural properties of the the samples
Sample Specific surface area A/(m2·g-1) Porevolume v/(cm3·g-1) Porediameterd/(nm) ZSM-5(Si/Al=80) 325.58 0.10 0.57 SBA-15 844.07 1.11 5.27 ZSM-5-SBA-15(80) 820.08 0.94 4.46 Sr-ZSM-5-SBA-15(80) 811.69 0.94 4.18 表 4 ZSM-5-SBA-15(80)和Sr-ZSM-5-SBA-15(80)样品的Py-FTIR表征
Table 4 Brönsted acid sites and Lewis acid sites of ZSM-5-SBA-15(80) and Sr-ZSM-5-SBA-15(80) by Py-FTIR
ZSM-5-SBA-15(80) Sr-ZSM-5-SBA-15(80) B and L B L B and L B L 160℃ 0.014 0.172 0.186 0.012 0.183 0.195 250℃ 0.009 0.087 0.096 0.011 0.092 0.103 350℃ 0.069 0.092 0.161 0.109 0.094 0.203 450℃ 0.065 0.011 0.076 0.009 0.007 0.016 Total acid sites 0.157 0.362 0.519 0.141 0.376 0.517 B: Brönsted acid sites ; L: Lewis acid sites; B and L: Brönsted acid sites and Lewis acid sites -
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