低硅SAPO-34分子筛的复合模板剂法合成及其对甲醇制烯烃的催化性能

系统考察了模板剂比例和晶化条件对复合模板剂(三乙胺+四乙基氢氧化铵)法合成低硅SAPO-34分子筛的影响;评价了合成产物对甲醇制烯烃的催化性能.结果表明,190℃晶化时不易合成低硅SAPO-34分子筛,而170℃晶化、模板剂组成为2Et3N+0.3TEAOH时可合成纯相SAPO-34分子筛.较高温度晶化时,延长晶化时间,SAPO-34有向SAPO-5转晶的趋势,而较低温度晶化时则相反.与晶化3 d的分子筛样品相比,170℃晶化5 d后的分子筛样品的比表面积较大、强酸中心较多、弱酸中心较少、对甲醇制烯烃反应的催化寿命较长.

Synthesis of Low Silicon SAPO-34 Molecular Sieve by Composite Template Method and Its Catalytic Performance from Methanol to Olefin

The effect of template content and crystallization conditions on synthesizing SAPO-34 molecular sieve with low silicon content was systematically investigated.The catalytic perfor-mance of resultant synthetic product for methanol to olefin reaction was evaluated.It was found that SAPO-34 molecular sieve was hardly synthesized at a crystallization temperature of 190 ℃,while pure SAPO-34 could be successfully synthesized at a crystallization temperature of 170 ℃ from composite template of 2Et3N＋0.3TEAOH.During crystallization at a higher temperature,SAPO-34 phase tended to be transformed into SAPO-5 with extending crystallization time;and SAPO-5 phase tended to be transformed into SAPO-34 during crystallization at a lower temperature.Moreover,as compared with the SAPO-34 product obtained after three-day crystallization at 170 ℃,the one obtained after five-day crystallization at the same temperature had a larger specific surface area and possessed more strong acid sites and less weak acid sites as well as longer catalytic stability for methanol to olefin reaction.