Effects of sugars on the structure of SAPO-34 and its MTO performance
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摘要: 以廉价的木糖、蔗糖、淀粉和葡甘聚糖为硬模板剂成功合成出含多级孔道的SAPO-34分子筛，采用XRD、BET、SEM、TEM、ICP和NH3-TPD等手段对催化剂进行了表征，并在固定床上，研究了糖类硬模板剂对SAPO-34分子筛的结构以及MTO性能的影响。结果表明，糖类硬模板剂能够提升SAPO-34分子筛的比表面积、微孔和介孔体积。与常规SAPO-34分子筛相比，多级孔道SAPO-34分子筛的双烯选择性和寿命均高。介孔体积最大、酸量最少、酸性最弱的SAPO-34-z分子筛的寿命最长（130 min），高出常规SAPO-34分子筛（100 min）30%，分子筛寿命从长到短顺序为SAPO-34-z > SAPO-34-h > SAPO-34-d > SAPO-34-m > SAPO-34 > SAPO-34-p。含多级孔道的SAPO-34分子筛的双烯选择性均高于常规SAPO-34分子筛。Abstract: Hierarchical SAPO-34 zeolites were successfully synthesized using cheap xylose, sucrose, starch and glucomannan as hard template and characterized by means of XRD, BET, SEM, TEM, ICP and NH3-TPD. The effects of sugar hard template on the structure and MTO properties of as-prepared SAPO-34 zeolites were studied on a fixed bed. The results showed that introduction of carbohydrate hard template could increase the specific surface area, microporous and mesoporous volume of SAPO-34 zeolites. The olefin selectivity and lifetime of SAPO-34 were both higher than those of ordinary SAPO-34. The SAPO-34-z with the largest mesoporous volume, the least acidity amounts and the weakest acidity showed the longest lifetime (130 min), which was 30% longer than that of ordinary SAPO-34 (100 min). The lifetime of zeolites decreased in the order of SAPO-34-z > SAPO-34-h > SAPO-34-d > SAPO-34-m > SAPO-34 > SAPO-34-p. The olefin selectivity of hierarchical SAPO-34 zeolites is higher than that of conventional SAPO-34 zeolites.
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Key words:
- methanol /
- SAPO-34 /
- olefin /
- hierarchical
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图 1 SAPO-34分子筛和多级孔SAPO-34分子筛的XRD谱图
Figure 1 XRD spectra of SAPO-34 and hierarchical SAPO-34
图 2 常规SAPO-34分子筛和多级孔道SAPO-34分子筛的电镜照片
Figure 2 SEM images of SAPO-34 and hierarchical SAPO-34
图 3 常规SAPO-34分子筛(a)和SAPO-34-z分子筛(b)的TEM照片
Figure 3 TEM images of SAPO-34 (a) and SAPO-34-z (b)
图 4 不同SAPO-34分子筛的氮气吸附-脱附等温曲线
Figure 4 N2 adsorption-desorption isotherms of SAPO-34 and hierarchical SAPO-34
图 5 不同SAPO-34分子筛的孔径分布
Figure 5 Pore size distribution of SAPO-34 and hierarchical SAPO-34
图 6 SAPO-34和多级孔SAPO-34分子筛的NH3- TPD谱图
Figure 6 NH3-TPD profile of SAPO-34 and hierarchical SAPO-34
图 7 SAPO-34和多级孔SAPO-34分子筛的双烯选择性
Figure 7 Ethylene and propylene selectivity of different SAPO-34
表 1 SAPO-34分子筛的比表面积、孔体积和平均孔径
Table 1 Specific surface area, pore volume and average pore diameter of different SAPO-34
Zeolite Specific surface area A/(m2·g-1) Volume/(cm3·g-1) Average pore size d/nm vmicro vmeso SAPO-34 249.2 0.106 0.006 13.1 SAPO-34-p 467.3 0.212 0.009 26.7 SAPO-34-m 482.9 0.215 0.020 12.7 SAPO-34-z 441.7 0.201 0.024 13.5 SAPO-34-d 507.6 0.241 0.012 24.3 SAPO-34-h 499.4 0.223 0.012 12.5 
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表 2 SAPO-34分子筛的ICP分析
Table 2 ICP of different SAPO-34
Zeolite Chemical composition /% Si Al P O SAPO-34 9.82 18.81 18.96 52.41 SAPO-34-p 7.02 20.84 19.90 52.23 SAPO-34-m 5.3 21.81 20.73 52.17 SAPO-34-z 4.25 22.67 20.98 52.09 SAPO-34-d 8.00 20.23 19.49 52.27 SAPO-34-h 5.35 21.48 20.94 52.23
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表 3 不同SAPO-34分子筛的产物分布
Table 3 Product distribution of different SAPO-34
Product Yield w/% SAPO-34 SAPO-34-p SAPO-34-m SAPO-34-z SAPO-34-d SAPO-34-h CH4 1.6 1.7 0.7 0.3 0.8 0.1 C2H4 37.8 38.6 41.5 39.9 40.5 42.6 C2H6 2.0 2.3 2.0 1.6 1.6 1.7 C3H6 36.8 36.1 36.1 36.5 36.0 35.4 C3H8 6.8 7.2 7.0 7.7 5.5 7.8 C4 13.2 8.6 11.1 12.4 11.8 10.2 C5+C5+ 1.7 5.4 1.5 1.5 3.7 2.1 H2 0.1 0.1 0.1 0.1 0.1 0.1 ΣC2=+C3= 74.7 74.8 77.6 76.3 76.5 78.0
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