活化晶种调节SAPO-34的性质及其对甲醇制烯烃反应催化寿命的增强

doi:10.15541/jim20200059

摘要/Abstract

摘要：

无溶剂法合成沸石法在多个方面优于常规水热合成法, 近年来引起广泛关注, 但是采用该方法合成的微孔SAPO-34沸石催化剂的催化寿命较短, 无法满足甲醇制烯烃工业应用的要求。本研究中开发了一种改良的无溶剂法, 使用该法合成了具有优异甲醇制烯烃反应性能的SAPO-34催化剂。该法在合成体系中引入酸活化晶种, 通过调节沸石晶化动力学来调控催化剂的物理化学性质。采用不同技术对无溶剂法合成的系列SAPO-34催化剂的结构性质进行了分析表征。结果表明：与未引入晶种合成的父代样品相比, 添加晶种得到的子代SAPO-34样品具有更高的结晶度、比表面积及低的强酸中心密度, 对甲醇制烯烃反应的催化寿命可延长到480 min, 远远优于对应的父代样品(40 min)。这一结果证实了无溶剂合成中晶种的使用可有效调节沸石的性质, 可见该方法在提高沸石催化性能方面具有巨大潜力。

关键词: SAPO-34沸石, 甲醇制烯烃反应, 无溶剂合成, 活化晶种

Abstract:

Solvent-free synthesis of zeolites has received extensive attention in recent years, because it is advantageous over conventional hydrothermal synthesis. Nevertheless, SAPO-34, a micropore zeolite, prepared by this method does not satisfy the catalytic lifetime requirements of the methanol-to-olefins (MTO) reaction. Herein, an improved solvent-free approach was developed to synthesize SAPO-34 catalysts with enhanced MTO reaction performance, in which acid-etched seed crystals were introduced to modulate the physico-chemical properties of the zeolite via crystallization kinetics regulation. The results indicated that the SAPO-34 samples prepared from seed-containing precursor gels show considerably higher crystallinity, larger surface area, but lower strong acid site density than the parent sample. In particular, the catalytic lifetime of the SAPO-34 catalyst prepared from activated seeds was remarkably prolonged to 480 min, which was significantly superior to that of the parent sample (40 min). The result confirmed the validity of the seeding approach for modifying the zeolite properties via the solvent-free synthesis and the potential of the approach in improving catalytic performance.

Key words: SAPO-34, methanol to olefins reaction, solvent-free synthesis, activated seeds

中图分类号:

TQ174

张栋强, 路惠惠, 苏娜, 李贵贤, 季东, 赵新红. 活化晶种调节SAPO-34的性质及其对甲醇制烯烃反应催化寿命的增强[J]. 无机材料学报, 2021, 36(1): 101-106.

ZHANG Dongqiang, LU Huihui, SU Na, LI Guixian, JI Dong, ZHAO Xinhong. Modulation of SAPO-34 Property with Activated Seeds and Its Enhanced Lifetime in Methanol to Olefins Reaction[J]. Journal of Inorganic Materials, 2021, 36(1): 101-106.

图/表 9

Fig. 1 XRD patterns of SAPO-34 synthesized with different types of seeds

Fig. 2 SEM images of samples in the presence of various types of seeds (a) SP34; (b) SP34-RS; (c) SP34-AS0.1; (d) SP34-AS0.01; (e) SP34-AS0.001; (f) SP34-AS0.0001

Table 1 Textural properties, acid amount and catalytic lifetime of different samples in MTO reaction

Sample	Textual properties					Acid amount ^c			Lifetime /min
Sample	S_BET/(m²·g^-1)	S_mic/(m²·g^-1)	S_ext/(m²·g^-1)	V_mic^a/(cm³·g^-1)	V_meso^b/(cm³·g^-1)	Weak	Medium and strong	Total	Lifetime /min
SP34	250	68	182	0.029	0.342	2.77	5.37	8.14	40
SP34-RS	316	291	24	0.136	0.068	0.86	2.05	2.91	100
SP34-AS_0.1	547	530	17	0.247	0.057	0.97	2.55	3.52	480
SP34-AS_0.01	552	532	20	0.249	0.056	1.42	3.41	4.83	300
SP34-AS_0.001	568	553	15	0.254	0.052	0.85	2.20	3.05	420
SP34-AS_0.0001	568	547	21	0.256	0.049	1.27	3.15	4.42	330

Fig. 3 N2 adsorption/desorption isotherms of SP34, SP34-RS and SP34-ASX (X=0.1, 0.01, 0.001, 0.0001)

Fig. 4 NH3-TPD profiles of SP34, SP34-RS and SP34-ASX (X=0.1, 0.01, 0.001, 0.0001)

Fig. 5 Methanol conversion over SP34, SP34-RS and SP34-ASX (X=0.1, 0.01, 0.001, 0.0001) catalysts with time-on-stream in the MTO reaction

Fig. S1 Relative crystallinity of SAPO-34 synthesized in the presence of various kinds of seed crystals

Fig. S2 Pore size distribution of SP34, SP34-RS and SP34-ASX (X=0.1, 0.01, 0.001, 0.0001 mol/L)

Fig. S3 Deconvolution of NH3-TPD curves of SP34, SP34-RS and SP34-ASX (X=0.1, 0.01, 0.001, 0.0001 mol/L)

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