SAPO-18/SAPO-34共晶分子筛的合成及表征

Synthesis and Characterization of Intergrowth Structured SAPO-18 / SAPO-34

以三乙胺（TEA）和N,N-二异丙基乙胺（DIEA）为双模板剂经恒温水热晶化法合成了SAPO-18（AEI结构）与SAPO-34（CHA结构）两相共生的SAPO分子筛.考察了DIEA用量、硅铝比及晶化时间等因素的影响,并通过X射线衍射（XRD）、扫描电子显微镜（SEM）和氨气程序升温脱附（NH3-TPD）等手段对所得样品的晶相、形貌和酸性进行了表征.结果表明,当n（DIEA）/n（Al2O3）=0.2,n（Si O2）/n（Al2O3）=0.6,晶化时间为4 d时,得到形貌规整,结晶度高且AEI/CHA结构比为74∶26的共生相SAPO分子筛.随着晶化时间的延长,SAPO-18在AEI/CHA共生相中所占比例逐渐上升,表明SAPO-5,SAPO-34和SAPO-18三者中SAPO-18的热力学稳定性最高.二甲醚制烯烃（DTO）催化性能测试结果表明,AEI/CHA共晶结构比为74/26的共生相分子筛具有较高的催化活性和双烯（C2^=＋C3^=）选择性（84.29%）,同时积碳生成速率较慢.

SAPO-18 （AEI structure） and SAPO-34 （CHA structure） intergrowth structured silicoaluminophosphate molecular sieves were synthesized hydrothermally with trimethylamine（TEA） and N,N-diisopropylethyl- amine（DIEA） as double templates. Influencing factors, such as DIEA content, SiOJA1203 molar ratio and crystallization time were investigated in detail. The crystalline phase, morphology and acidic property of the products were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and temperature-programmed desorption of ammonia（ NH3-TPD）, respectively. The results showed that well crystallized, morphology uniformed AEI/CHA intergrowth structured silicoaluminophosphate molecular sieves with AEI/ CHA= 74/26 could be synthesized under the following synthesis conditions： n （DIEA）/n （AEI）= 0. 2, n（ SiO2 ）/n（ AI203 ）= 0.6 and the crystallization time 96 h. The extending of crystallization time resulted in the disappearance of SAPO-5 and the gradual increase of AEI/CHA proportion. It is therefore concluded that the thermodynamic stability of SAPO-5, SAPO-34, SAPO-18 increased in this order. Dimethylether-to-olefins （DTO） reaction was chosen to test the catalytic performance of the prepared catalysts. The prepared catalyst using TEA-DIEA as double templates exhibited excellent catalytic performance in DTO （dimethyl ether to olefins） process. The conversion of dimethylether and selectivity of ethylene and propylene are up to 100% and 84.29%, respectively.