海绵辅助离子液体干胶法合成ZSM-22分子筛大颗粒

doi:10.15541/jim20140575

摘要/Abstract

摘要：

采用海绵辅助的以离子液体作为结构导向剂的干凝胶转换法制备了宏观尺寸在毫米级的全硅ZSM-22沸石分子筛大颗粒, 干凝胶的制备采用了酸环境下水解含有离子液体结构导向剂的硅源的特殊方法。结果表明, 海绵辅助的离子液体干胶法对于颗粒状形貌的形成起了关键作用, 在合成过程中不加入海绵或者在传统水热合成路线中加入海绵都得不到具有这种宏观颗粒形貌的ZSM-22沸石。实验系统考察了海绵的添加量、添加时间及干胶晶化时间对合成的影响, 发现在微波老化结束后向合成体系添加适量的海绵, 有利于合成高结晶度的颗粒状全硅ZSM-22沸石。N₂O-TPD实验结果表明, 所得颗粒状ZSM-22负载氧化铜后对于N₂O的吸附能力优于后处理粘结剂成型的ZSM-22分子筛, 说明调控沸石分子筛的宏观形貌对于沸石分子筛的吸附能力具有重要作用。

关键词: ZSM-22, 宏观形貌控制, 海绵, 离子液体, 干胶法, N2O程序升温脱附

Abstract:

Pure-silica ZSM-22 particles with millimeter size were directly synthesized by adding polyurethane foam (PU foam) in ionic liquid-directed dry-gel-conversion process, where the dry gel was prepared under the unusual acidic condition for hydrolyzing the silica precursor with 1,3-alkylimidazolium ionic liquid as the structure directing agent (SDA). Both the PU foam and the ionic liquid-directed dry-gel-conversion process played essential roles in the formation of macroscopic morphology, because only powder-like sample could be obtained in the absence of foam, and moreover, no such special morphology could be achieved on ZSM-22 zeolite prepared by the PU foam-added traditional hydrothermal synthetic route. Various synthetic parameters were systematically studied, including the influence of PU foam, adding time and adding amount of PU foam, as well as the crystallization time. Pure phase ZSM-22 particles with the highest crystallinity can be obtained by adding appropriate volume of PU foam after microwave aging. Finally, the directly synthesized ZSM-22 particles were modified by impregnating CuO, which exhibited superior N₂O adsorption property to the CuO-impregnated post-molded ZSM-22 particles with binding materials. The results indicate that there is an important influence of the macro-morphology on the adsorption performance of zeolites.

Key words: ZSM-22, macro-morphology control, polyurethane foam, ionic liquid, dry gel conversion, N2O-TPD

中图分类号:

O613

闻海萌, 宋军, 王重庆, 周瑜, 王军. 海绵辅助离子液体干胶法合成ZSM-22分子筛大颗粒[J]. 无机材料学报, 2015, 30(6): 615-620.

WEN Hai-Meng, SONG Jun, WANG Chong-Qing, ZHOU Yu, WANG Jun. Directly Synthesis of ZSM-22 Particles by Adding Polyurethane Foam in Ionic Liquid-directed Dry-gel-conversion[J]. Journal of Inorganic Materials, 2015, 30(6): 615-620.

图/表 7

图1 样品的宏观照片及SEM照片

Fig. 1 Macro photographs and SEM images of samples Macro photographs of (a) dry gel, (b) as-synthesized ZSM-22 particles, (c) as-calcined ZSM-22 particles, (d) product synthesized by dry gel conversion without PU foam; (e, f) SEM images of as-calcined ZSM- 22 particles

图2 水热合成样品的XRD图谱及宏观照片

Fig. 2 XRD patterns and picture (inset) of product synthesized by hydrothermal synthesis method

图3 不同合成条件得到样品的XRD图谱

Fig. 3 XRD patterns of as-calcined ZSM-22 particles synthesized under different conditions (A) With different volumes of PU foam: (a) 2 cm3; (b) 4 cm3; (c) 8 cm3; (B) Adding the PU foam (a) before hydrolysis of TEOS, (b) before aging with microwave; (C) With 16 cm3 PU foam and different crystallization time: (a) 1 d, (b) 2 d, (c) 3 d

图4 170℃晶化(a) 1 d和 (b) 2 d的ZSM-22大颗粒SEM照片

Fig. 4 SEM images of as-calcined ZSM-22 particles crystallized at 170℃ for (a) 1 d and (b) 2 d

图5 颗粒状ZSM-22的N2吸脱附曲线及FT-IR曲线

Fig. 5 (A) N2 adsorption-desorption isotherm of as-calcined ZSM-22 particle synthesized with PU foam of 16 cm3; (B) FT-IR spectra of (a) as-synthesized and (b) as-calcined ZSM-22 particle obtained with PU foam of 16 cm3

图6 CuO/ZSM-22颗粒XRD图谱及N2吸附-脱附曲线

Fig. 6 (A) XRD patterns and (B) N2 adsorption-desorption isotherm of the CuO/ZSM-22 particles

图7 CuO/ZSM-22颗粒样品的N2O-TPD曲线

Fig. 7 N2O-TPD curves of CuO/ZSM-22 particles

参考文献 20

[1]	GOUNDER R, IGLESIA E.The catalytic diversity of zeolites: confinement and solvation effects within voids of molecular dimensions. Chem. Commun., 2013, 49(37): 3854-3856.
[2]	BUI L, LUO H, GUNTHER W R, et al.Domino reaction catalyzed by zeolites with bronsted and lewis acid sites for the production of valerolatone from furfural.Angew. Chem. Int. Ed., 2013, 52(31): 8022-8025.
[3]	LUPULESCU A I, RIMER J D.In situ imaging of silicalite-1 surface growth reveals the mechanism of crystallization.Science, 2014, 344(6185): 729-732.
[4]	OEZASSLAN M, HEGGEN M, STRASSER P.Size-dependent morphology of dealloyed bimetallic catalysts: linking the nano to the macro scale.J. Am. Chem. Soc., 2012, 134(1): 514-524.
[5]	SUN Z K, DENG Y H, ZhAO D Y, et al. Hierarchically ordered macro-/mesoporous silica monolith: tuning macropore entrance size for size-selective adsorption of proteins.Chem. Mater., 2011, 23(8): 2176-2184.
[6]	VASILIEV P, AKHTAR F, GRINS J, et al.Strong hierarchically porous monoliths by pulsed current processing of zeolite powder assemblies.ACS Appl. Mater. Interface, 2010, 2(3): 732-737.
[7]	XUE C F, WANG J X, TU B, et al.Hierarchically porous silica with ordered mesostructure from confinement self-assembly in skeleton scaffolds.Chem. Mater., 2010, 22(2): 494-503.
[8]	SERRANO D P, ESCOLA J M, PIZARRO P.Synthesis of strategies in the search for hierarchical zeolites.Chem. Soc. Rev., 2013, 42(9): 4004-4035.
[9]	LI X, WANG X P, CHEN H G, et al.Hierarchically porous bioactive glass scaffolds synthesized with a PUF and P123 contemplated approach. Chem. Mater., 2007, 19(17): 4322-4326.
[10]	XUE C F, TU B, ZHAO D Y.Evaporation-induced coating and self-assembly of ordered mesoporous carbon-silica composite particles with macroporous architecture on polyurethane foams.Adv. Funct. Mater., 2008, 18(24): 3914-3921.
[11]	CAI R, LIU Y, YAN Y S.Ambient pressure dry-gel conversion method for zeolite MFI synthesis using ionic liquid and microwave heating.J. Am. Chem. Soc., 2010, 132(37): 12776-12777.
[12]	ZHOU J, HUA Z, ZHAO J J, et al.A micro/mesoporous aluminosilicate: key factors affecting framework crystallization during steam-assisted synthesis and its catalytic property.J. Mater. Chem, 2010, 20(32): 6764-6771.
[13]	ZHANG X Y, SHEN Q, HE C, et al.Investigation of selective catalytic reduction of N2O by NH3 over an Fe-Mordenite catalyst: reaction mechanism and O2 effect.ACS Catal., 2012, 2(4): 512-520.
[14]	ZHOU H B, HU P L, HUANG Z, et al.Preparation of NiCe mixed oxides for catalytic decomposition of N2O.Ind. Eng. Chem. Res., 2013, 52(12): 4504-4509.
[15]	HABER J, NATTICH M, MACHEJ T.Alkali-metal promoted rhodium-on-alumina catalysts for nitrous oxide decomposition.Appl. Catal., B, 2008, 77(3/4): 278-283.
[16]	ATES A, REITZMANN A, WATERS G. Surface oxygen generated upon N2O activation on iron containing ZSM-5 type zeolites with different elemental composition. Appl. Catal., B, 2012, 119-120: 329-339.
[17]	LI C L, SHEN Y S, SHEN S B, et al.Supported Ni-La-Ox for catalytic decomposition of N2O I: component optimization and synergy.RSC Adv., 2014, 4(55): 29107-29119.
[18]	CHANG K S, SONG H, PARK Y S, et al.Analysis of N2O decomposition over ﬁxed bed mixed metal oxide catalysts made from hydrotalcite-type precursors.Appl. Catal., A, 2004, 273(1/2): 223-231.
[19]	WEN H M, ZHOU Y, WANG J, et al.Pure-silica ZSM-22 zeolite rapidly synthesized by novel ionic liquid-directed dry-gel conversion. RSC Adv., 2014, 4(91): 49647-49654.
[20]	SADOWSKA K, GORA-MAREK K, DATKA J.Accessibility of acid sites in hierarchical zeolites: quantitative IR studies of pivalonitrile adsorption.J. Phys. Chem., 2013, 117(18): 9237-9244.