Effect of Mg/P mol ratio on the catalytic performance of NiW/MgAPO-5 in the hydrocracking of tetralin to BTEX
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摘要: 以水热法合成的一系列镁磷物质的量比不同的MgAPO-5分子筛为载体，采用等体积共浸渍的方法制备NiW/MgAPO-5催化剂。采用X射线衍射（XRD）、N2物理吸附、扫描电子显微镜（SEM）、氨气程序升温脱附（NH3-TPD）、吡啶吸附红外光谱（Py-FTIR）和氢气程序升温还原（H2-TPR）对载体和负载型催化剂进行了表征。以四氢萘为模型化合物，在小型固定床上考察了不同镁磷物质的量比的催化剂加氢裂化制BTEX性能。结果表明，Mg/P（mol ratio）对MgAPO-5载体的晶相、镁含量、形貌和酸性质产生显著的影响，并且Mg2+引入到了分子筛骨架。催化性能评价结果表明，NiW负载量相同时，四氢萘的转化率由载体MgAPO-5的酸强度决定，而BTEX的选择性在载体酸性和催化剂加氢组分相匹配处达到最优。当Mg/P（mol ratio）为0.05时，四氢萘的转化率最高，而BTEX的选择性则在Mg/P（mol ratio）为0.03时达到最大。Abstract: A series of MgAPO-5 molecular sieves with a wide range of Mg/P mol ratios in the gel was synthesized by a hydrothermal process.Using MgAPO-5 as acidic supports, the bifunctional NiW/MgAPO-5 catalysts were prepared by impregnation method, and applied to the hydrocracking of tetralin to produce BTEX.The synthesized MgAPO-5 molecular sieves and NiW/MgAPO-5 samples were characterized by XRD, N2 adsorption, SEM, NH3-TPD, Py-FTIR and H2-TPR.The results exhibit that the Mg/P mol ratio has a great influence on the unit cell parameters, morphology, the Mg content and the acidity of MgAPO-5 samples, and the ion of Mg2+ is incorporated into the framework.In the hydrocracking of tetralin, with the same amount of NiW, the activity of NiW/MgAPO-5 is primarily controlled by the acidic strength of MgAPO-5.The selectivity of BTEX was determined by the combined effect of the acidity of MgAPO-5 and the (de) hydrogenation function of NiW.The highest conversion is achieved with the Mg/P mol ratio of 0.05, and the best BTEX selectivity is obtained with the Mg/P mol ratio of 0.03.
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Key words:
- MgAPO-5 /
- Mg/P (mol ratio) /
- tetralin /
- hydrocracking /
- BTEX
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图 1 MgAPO-5催化剂的XRD谱图
Figure 1 XRD patterns of MgAPO-5 catalysts
a: M0; b: M1; c: M3; d: M5; e: M10; f: NiW/M3
图 2 MgAPO-5催化剂的SEM照片
Figure 2 SEM images of MgAPO-5 catalysts
(a): M0; (b): M1; (c): M3; (d): M5; (e): M10； (f): M20
图 3 MgAPO-5催化剂的NH3-TPD谱图
Figure 3 NH3-TPD profiles of MgAPO-5 catalysts
a: M0; b: M1; c: M3; d: M5; e: M10
图 5 MgAPO-5催化剂的Py-FTIR谱图
Figure 5 Py-FTIR spectra of MgAPO-5 samples
a: M0; b: M1; c: M3; d: M5; e: M10
图 6 催化剂的H2-TPR谱图
Figure 6 H2-TPR profiles of catalysts
a: NiW/M0; b: NiW/ M1; c: NiW/M3; d: NiW/M5; e: NiW/M10
图 7 四氢萘在不同镁磷比的NiW/MgAPO-5 催化剂上加氢裂化反应转化率和BTEX选择性
Figure 7 Conversion and BTEX selectivity of tetralin hydrocracking over NiW/MgAPO-5 catalysts with different Mg/P mol ratios
表 1 载体MgAPO-5的织构性质
Table 1 Textural properties of MgAPO-5 samples
Sample Mg/P (mol ratio) Unit cell parameters/nm V/nm3 BET
A/(m2·g-1)a(=b) c M0 0.00 1.363 0.835 1.551 63 M1 0.01 1.364 0.836 1.556 70 M3 0.03 1.376 0.840 1.591 140 M5 0.05 1.381 0.837 1.596 151 M10 0.10 1.383 0.839 1.604 133 
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表 2 MgAPO-5催化剂的酸性质
Table 2 Acidity of the calcined MgAPO-5 molecular sieves
Sample Acidity/(μmmol·g-1)a Brönsted/Lewisb At AW AS 200 ℃ 400 ℃ M0 22.12 - - - - M1 43.20 33.36 9.84 0.44 0.64 M3 84.01 47.32 36.68 0.33 0.29 M5 97.71 60.45 37.26 0.21 0.16 M10 200.45 117.43 83.01 0.46 0.42 a: results of NH3-TPD b: calculated from FT-IR spectra
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