低量结构导向剂改进离子热法高效合成LTA型磷酸铝分子筛

doi:10.15541/jim20160062

摘要/Abstract

摘要：

在低的有机胺和离子液体用量条件下, 采用晶种协助改进的离子热法高效合成了LTA拓扑结构的磷酸铝分子筛, 考察了有机胺的类型、晶化温度、有机物种用量及晶种对LTA型分子筛合成的影响, 并优化了合成条件。合成结果表明, 即使初始凝胶中离子液体/Al₂O₃和有机胺/Al₂O₃的摩尔比均降低至0.67, 通过添加少量晶种的办法仍可成功合成LTA分子筛。在优化合成条件下, 分子筛产物的无机原子利用率可高达86%。采用XRD、SEM、氮气物理吸脱附、TG-DTA、CHN元素分析和¹³C NMR对上述分子筛的结构、形貌及孔穴中的有机物种进行了全面分析。结果表明所合成的LTA分子筛是一种同时含有微孔和介孔结构的多级孔分子筛, 吗啉和1-乙基-3-甲基咪唑阳离子之间的协同效应导向了LTA分子筛的生成。

关键词: 离子热合成, 晶种, 无溶剂合成, LTA沸石, 多级孔

Abstract:

Aluminophosphate molecular sieve with LTA topology was efficiently synthesized by seed-assisted and improved ionothermal method with low dosages of organic amines and ionic liquids (ILs). The influences of organic amine type, crystallization temperature, amount of organic species, and seed crystals on the synthesis of LTA-type material were investigated, to refine the synthetic conditions. The results indicate that LTA-type molecular sieve is synthesized even by adding small amount of seed crystal into initial gels, of which both molar ratios of ILs/Al₂O₃ and Amine/Al₂O₃ are decreased to 0.67. Utilization rate of inorganic raw materials during as-synthesis is up to 86% under optimal conditions. Structure and morphology of the products, together with organic species occluded in cavities were fully analyzed by XRD, SEM, N₂ physisorption, TG-DTA, CHN elemental analysis, and liquid ¹³C NMR. The results show that the resultant LTA molecular sieve is a hierarchically porous material with both micropores and mesopores inside. It is the cooperative structure-directing effect between morpholine and 1-ethyl-3-methylimidazolium cations that guides the formation of LTA molecular sieve.

Key words: ionothermal synthesis, seed crystals, solvent-free synthesis, LTA zeolite, hierarchical porous

中图分类号:

O614

赵新红, 高向平, 赵江波, 张晓晓, 郝志鑫. 低量结构导向剂改进离子热法高效合成LTA型磷酸铝分子筛[J]. 无机材料学报, 2016, 31(11): 1212-1218.

ZHAO Xin-Hong, GAO Xiang-Ping, ZHAO Jiang-Bo, ZHANG Xiao-Xiao, HAO Zhi-Xin. Highly Efficient Synthesis of LTA-type Aluminophosphate Molecular Sieve by Improved Ionothermal Method with Low Dosage of Structure-directing Agent[J]. Journal of Inorganic Materials, 2016, 31(11): 1212-1218.

图/表 9

表1 合成条件及其对应产物相

Table 1 Conditions and corresponding synthetic products

Sample	Al₂O₃:P₂O₅:HF:Amine :ILs (molar ratio)	Temper- ature/℃	Product phases
A1	1:1:1:1:2	150	LTA
A2	1:1:1:1^a:2	150	LTA+Impurities
A3	1:1:1:1^b:2	150	LTA+Impurities
A4	1:1:1:1^c:2	150	Amorphous
B1	1:1:1:1:2	170	LTA
B2	1:1:1:1:2	190	CHA
C1	1:1:1:0.33:0.67	150	CHA+Berlinite
C2	1:1:1:0.67:0.67	150	CHA+Berlinite
C3	1:1:1:0.5:1	150	CHA+Berlinite
C4	1:1:1:1:1	150	LTA+Impurities
D1	1:1:1:0.67:0.67^d	150	LTA+Amorphous
D2	1:1:1:0.5:1^d	150	CHA+Berlinite
D3	1:1:1:1:1^d	150	LTA+Impurities

图1 [emim]Br中加入不同有机胺所合成产物的XRD图谱

Fig. 1 XRD patterns of the products synthesized from [emim]Br adding with different amines

图2 原粉样品的SEM照片

Fig. 2 SEM images of the as-synthesized samples (a) A1; (b) A3; (c) B1; (d) B2; (e) C1; (f) C2; (g) C3; (h) C4; (i) D1; (j) D2; (k) D3. Bars are 10 μm

图3 不同晶化温度下所合成产物的XRD图谱

Fig. 3 XRD patterns of the products synthesized at different crystallization temperatures

图4 低的吗啉和离子液体加入量下所合成产物的XRD图谱

Fig. 4 XRD patterns of the products synthesized with low dosages of morpholine and ionic liquid

图 5 LTA型磷酸铝分子筛原粉(B1)的液体13C NMR和TG- DTA 图谱

Fig. 5 Solution 13C NMR and TG-DTA profiles of the as- synthesized LTA-type aluminophosphate molecular sieve (sample B1)

图 6 加入晶种的条件下所合成产物的XRD图谱

Fig. 6 XRD patterns of the products synthesized in the presence of seed crystals

图7 焙烧样品A1、B1、C4、D1和D3的氮气物理吸脱附等温线

Fig. 7 N2 adsorption/desorption isotherms of the calcined samples A1, B1, C4, D1, and D3

表2 代表性样品的N2物理吸脱附表征数据

Table 2 Nitrogen physisorption data of the representative samples

Samples	S_BET /(m²·g^-1)	S_Ext /(m²·g^-1)	V_Micropore /(m³·g^-1)^a	V_Mesopore /(m³·g^-1)^b
A1	692	89	0.281	0.089
B1	729	111	0.287	0.112
C4	566	65	0.233	0.083
D1	299	100	0.092	0.400
D3	654	111	0.252	0.159

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