Preparation and disproportionation properties of NaAlCl4/ZSM-5@γ-Al2O3 core-shell catalyst
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摘要: 针对氯硅烷残留物的危害性和资源化利用，通过歧化反应将副产物制备成经济效益更高的二甲基二氯硅烷。由田菁胶为粘结剂，以γ-Al2O3为壳，对ZSM-5分子筛表面进行修饰，构筑ZSM-5@γ-Al2O3核壳载体；然后，通过高温浸渍负载法，将NaAlCl4负载在ZSM-5@γ-Al2O3核壳载体表面。综合研究了不同Si/Al摩尔比的ZSM-5分子筛、不同NaAlCl4负载比例和AlCl3溶液浸渍时间对歧化制备反应二甲基二氯硅烷的影响。采用XRD、SEM、SEM-EDS、BET和FTIR对样品进行表征分析，结果表明，当温度为200℃，硅铝摩尔比为50，复盐NaAlCl4比例为8wt%，AlCl3浸渍时间为3 h时，催化剂活性达到最佳，产率为71.81%。通过NaAlCl4复盐负载ZSM-5@γ-Al2O3核壳表面，改善单一催化成分性能不稳定，提高催化效率，再分配氯硅烷副产品甲基三氯硅烷(M1)和三甲基氯硅烷(M3)，得到商业价值较高的二甲基二氯硅烷(M2) ，实现变废为宝。Abstract: In view of the harmness and resource utilization of chlorosilane residues, the by-products are prepared into dimethyldichlorosilane with higher economic benefit through disproportionation reaction. The ZSM-5@γ-Al2O3 core-shell carrier was constructed by modifying the surface of ZSM-5 molecular sieve with Tianjing gum as the binder and γ-Al2O3 as the shell. NaAlCl4 was loaded on the surface of ZSM-5@γ-Al2O3 core-shell carrier by high-temperature impregnation loading method. The effect of ZSM-5 molecular sieve with different Si/Al molar ratios on the disproportionation preparation of dimethyldichlorosilane, the effect of different NaAlCl4 loading ratios and the impregnation time of AlCl3 solution on the reaction of disproportionation preparation of dimethyldichlorosilane were investigated comprehensively, and the samples were characterized by XRD, SEM, SEM-EDS, BET and FTIR. The results show that the catalyst activity reach the optimum with 71.81% yield when the temperature is 200°C, the silica-alumina molar ratio is 50, the compound salt NaAlCl4 ratio is 8wt%, and the AlCl3 impregnation time is 3 h. The NaAlCl4 compound salt loading on the surface of the ZSM-5@γ-Al2O3 core-shell catalyst shows the improved catalytic efficiency and enhanced performance instability compared with single catalytic component. Further redistribution chlorosilane by-products methyl trichlorosilane (M1) and trimethylchlorosilane (M3) synthesis can obtain high commercial value dimethyl dichlorosilane (M2), so as to realize the transformation of waste into treasure.
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Key words:
- NaAlCl4 /
- ZSM-5 /
- γ-Al2O3 /
- core-shell /
- disproportionation /
- dimethyldichlorosilane /
- catalyst
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图 1 不同Si/Al摩尔比的ZSM-5@γ-Al2O3载体对二甲基二氯硅烷(M2)产率的影响(甲基三氯硅烷(M1)和三甲基氯硅烷(M3)的比例为1vol%，催化剂的用量为0.6 g)
Figure 1. Effect of ZSM-5@γ-Al2O3 carriers with different Si/Al molar ratios on the yield of dimethyldichlorosilane (M2) (Volume ratio of M1/M3 is 1vol%, and the amount of catalysts was 0.6 g)
图 2 NaAlCl4/ZSM-5@γ-Al2O3催化剂负载不同质量比例的NaAlCl4复盐对M2产率的影响(Na/Al摩尔比1，AlCl3溶液的浸渍时间2 h，M1/M3的体积比为1vol%，催化剂的用量为0.6 g)
Figure 2. Effect of NaAlCl4/ZSM-5@γ-Al2O3 catalyst loaded with different mass ratios of NaAlCl4 double salt on M2 yield (Molar ratio of Na/Al is 1, the impregnation time of AlCl3 solution is 2 h, the volume ratio of M1/M3 is 1vol% and the amount of catalysts is 0.6 g)
图 3 不同AlCl3溶液浸渍时间的NaAlCl4/ZSM-5@γ-Al2O3催化剂对M2产率的影响(Na/Al摩尔比1，复盐NaAlCl4负载比例8wt%，M1/M3的体积比为1vol%，催化剂的用量为0.6 g)
Figure 3. Effect of NaAlCl4/ZSM-5@γ-Al2O3 catalysts on the yield of M2 with different impregnation time of AlCl3 solution (Molar ratio of Na/Al is 1, the loading ratio of compound salt NaAlCl4 is 8wt%, the volume ratio of M1/M3 is 1vol%, and the amount of catalyst is 0.6 g)
图 4 ZSM-5@γ-Al2O3载体及NaAlCl4/ZSM-5@γ-Al2O3催化剂负载不同比例NaAlCl4复盐的XRD图谱
Figure 4. XRD patterns of ZSM-5@γ-Al2O3 support and NaAlCl4/ZSM-5@γ -Al2O3 catalysts supported with different proportions of NaAlCl4 compound salts
1—ZSM-5@γ-Al2O3; 2—4wt%NaAlCl4/ZSM-5@γ-Al2O3; 3—8wt%NaAlCl4/ZSM-5@γ-Al2O3; 4—12wt%NaAlCl4/ZSM-5@γ-Al2O3; 5—16wt%NaAlCl4/ZSM-5@γ-Al2O3
图 5 (a) 8wt%NaAlCl4/ZSM-5@γ-Al2O3催化剂的孔径分布曲线图；(b) 8wt%NaAlCl4/ZSM-5@γ-Al2O3催化剂的脱吸附图
Figure 5. (a) Pore size distribution curve of the porous media of 8wt%NaAlCl4/ZSM-5@γ-Al2O3 catalyst; (b) Desorption diagram of 8wt%NaAlCl4/ZSM-5@γ-Al2O3 catalyst
图 6 NaAlCl4/ZSM-5@γ-Al2O3催化剂的SEM-EDS能谱图：负载4wt% (a)、8wt% (b)、12wt% (c) 和16wt% (d) NaAlCl4的催化剂元素分布及其含量
Figure 6. SEM-EDS spectra of NaAlCl4/ZSM-5@γ-Al2O3 catalysts: Element distribution and content catalysts supported with 4wt% (a), 8wt% (b), 12wt% (c) and 16wt% (d) NaAlCl4
图 7 各催化剂SEM图像：(a) ZSM-5；(b) ZSM-5@γ-Al2O3；((c)~(f)) 负载NaAlCl4复盐4wt%、8wt%、12wt%、16wt%的NaAlCl4/ZSM-5@γ-Al2O3催化剂
Figure 7. SEM images of catalysts: (a) ZSM-5; (b) ZSM-5@γ-Al2O3; ((c)-(f)) NaAlCl4/ZSM-5@γ-Al2O3 catalysts loaded with 4wt%, 8wt%, 12wt%, 16wt% of NaAlCl4 compound salt, respectively
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