以相同的组成及晶化温度,首次采用载体预陈化法在α-Al_2O_3载体外表面成功合成NaX型沸石膜.水热处理前,载体在合成母液中经室温陈化,而后在363 K下进行水热处理.通过控制陈化时间,研究陈化对所合成沸石膜的影响.研究发现,陈化把沸石合成分为成核阶段及晶体生长阶段,并能够很好地控制沸石的成核和膜生长.陈化期间,非均相的水凝胶相中形成的沸石晶核沉积在载体表面,形成晶体生长的诱导层.较少的陈化时间会产生杂晶相,如方钠石(SOD)、菱沸石(CHA)、方沸石(ANA),这些杂晶相是沸石FAU的竞争相.随着陈化时间的增加,方解石(FAU)则变成了主要相,而为了获得纯的RAU沸石相,至少陈化一天.分别用XRD和SEM鉴别膜的晶体结构及观察膜的形貌和厚度;通过单气体的渗透测试表征气体传递特性.结果显示,陈化对膜的晶粒大小、晶体互生性以及表面覆盖度有着重要的影响;陈化2天后晶化形成的NaX沸石膜对H_2/N_2的渗透通量及理想选择性最高分别可达37/10 mol/(m~2·Pa·s)和110.
With the fixed composition and crystallization temperature, NaX zeolite membranes were synthesized successfully on α-Al_2O_3 support tube pre-aged in the hydrogel phase. Prior to the hydrothermal treatment, a- Al_2O_3 support was aged in the synthesis mixture at the room- temperature, subsequently, a hydrothermal synthesis process was conducted at 373 K. The influence of aging in the membrane synthesis was investigated by controlling aging time. It was demonstrated that, during the aging process, zeolite nucleus were formed from the heterogeneous gel on support surface and became induction layer. In addition, aging process divides the zeolite synthesis into two steps, i. e. mucleation and crystal growth, and the zeolite nucleation and membrane growth can be well controlled. It was also found that less aging resulted in the formation of other heterocrystal-lization phases like sodalite (SOD), chabazite (CHA), and analcime (ANA), well- known as byproducts against faujasite(FAU). FAU becames the main product with increasing of the aging period. In order to gain the pure phase faujasite,aging of more than one day was required. X- Ray diffraction and scanning electron mi-croscopy were used for indentifying the crystal structure and observing the morphology and thickness of mem-brane, while the transportation properties was characterized by single gas permeate test. The results show that the aging has a significant influence on the crystal size of membrane, intergrowth property and surface coverage.Permeation and ideal selectivity of the membrane for H_2 and N_2 are 37/10 mol/(m~2·Pa·s) and 110,respectively.
参考文献
| [1] | Hidetoshi Kita;Kazunobu Fuchida;Tatsuya Horita;Hidetoshi Asamura;Hidetoshi Asamura .Preparation of Faujasite membranes and their permeation properties[J].Separation and Purification Technology,2001(1):261-268. |
| [2] | Clet G;Jansen J C;Bekkum H .Synthesis of a zeolite Y coating on stainless steel support[J].CHEMISTRY OF MATERIALS,1999,11:1696-1702. |
| [3] | Valtchev V;Mintova S .The effect of the metal substrate composition on the crystallization of zeolite coatings[J].Zeolites,1995,15:171-175. |
| [4] | Ayse Erdem-Senatalar;Melkon Tatlier;Mustafa Urgen .Preparation of zeolite coatings by direct heating of the substrates[J].Microporous and Mesoporous Materials,1999(3):331-343. |
| [5] | Yongan Yan;S. Ray Chaudhuri;Arnab Sarkar .Synthesis of Oriented Zeolite Molecular Sieve Films with Controlled Morphologies[J].Chemistry of Materials,1996(2):473-479. |
| [6] | Chau Joseph Lik Hang;Tellez Carlos .The role of surface chemistry in zeolite membrane formation[J].Journal of Membrane Science,2000(1/2):257-275. |
| [7] | Tooru Nakazawa;Masayoshi Sadakata;Tatsuya Okubo .Early stages of MFI film formation[J].Microporous and Mesoporous Materials,1998(4/6):325-332. |
| [8] | Exter M J;BekkumH;Rijn C J M et al.Stability of oriented silicalite-1 films in view of zeolite membrane preparation[J].Zeolites,1997,19:13-20. |
| [9] | Davis M E;Lobo R E .Zeolite and molecular sieve synthesis[J].Chemistry of Materials,1992,4:7-9. |
| [10] | Wan Cheong Wong;Louisa Tak Yin Au;Prudence P.S. Lau;Carlos Tellez Ariso;King Lun Yeung .Effects of synthesis parameters on the zeolite membrane morphology[J].Journal of Membrane Science,2001(2):141-161. |
| [11] | Yang S Y;Vlessidis A G;Evmiridis N P .Influence of gel composition and crystallization condition on the conventional synthesis of zeolites[J].Industrial and Engineering Chemistry Research,1997,36:1622-1631. |
| [12] | Ogura M.;Kawazu Y.;Takahashi H.;Okubo T. .Aluminosilicate species in the hydrogel phase formed during the aging process for the crystallization of FAU zeolite[J].Chemistry of Materials,2003(13):2661-2667. |
| [13] | Ginter D M;Bell A T;Radke C J .The effects of gel aging on the synthesis of NaY zeolite from colloidal silica[J].Zeolites,1992,12:742-749. |
| [14] | Ginter D M;Went G T;Bell A T et al.A physicochemical study of the aging of colloidal silica gels used in zeolite Ysynthesis[J].Zeolites,1992,12:733-741. |
| [15] | Yanfeng Zhang;Zhongqiang Xu;Qingling Chen .Synthesis of small crystal polycrystalline mordenite membrane[J].Journal of Membrane Science,2002(2):361-368. |
- 下载量()
- 访问量()
- 您的评分：
-
10%
-
20%
-
30%
-
40%
-
50%