四甲基氢氧化铵辅助合成SSZ-13分子筛及其甲醇制烯烃的催化性能

以N,N,N-三甲基金刚烷氢氧化铵(TMAdaOH)为模板剂合成SSZ-13分子筛，探讨有机季铵碱四甲基氢氧化铵(TMAOH)取代体系中的氢氧化钠(NaOH)对SSZ-13分子筛合成的影响，采用X射线衍射(XRD)、扫描电子显微镜(SEM)、傅里叶红外光谱(FT-IR)、热重-微商热重(TG-DTG)、NH₃程序升温脱附(NH₃-TPD)和N₂吸附-脱附等手段对合成样品进行表征，分析合成凝胶的硅/铝比对SSZ-13分子筛的结晶度、比表面积、酸量等的影响，并考察了SSZ-13分子筛在甲醇制烯烃(MTO)反应中的催化性能。结果表明，当有机碱TMAOH完全取代NaOH时，合成样品的结晶度从92.68%提高至108.75%，且合成体系的硅/铝比(n(SiO₂)/n(Al₂O₃))范围可以显著拓宽(33~100)，合成产物的硅/铝比也相应提高，比表面积可增大至约800 m²/g，强酸量减少，SSZ-13分子筛样品在MTO催化反应中表现出了更长的寿命和更高的双烯(乙烯+丙烯)选择性。

Synthesis of SSZ-13 Molecular Sieve Using Tetramethylammonium Hydroxide as an Auxiliary and Its Catalytic Performance in Methanol to olefinsReaction

Effects of the replacement of NaOH by tetramethylammonium hydroxide (TMAOH) on the synthesis of SSZ-13 molecular sieve were investigated in the presence of the N,N,N-trimethyl-1-adamantanammonium hydroxide (TMAdaOH) as structure-directing agent. The influences of silica/alumina ratios in synthetic gel on the structural, textural and acidic properties of SSZ-13 molecular sieve were investigated. The obtained SSZ-13 molecular sieves were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), thermogravimetry-derivative thermogravimetry (TG-DTG), NH₃-temperature programmed desorption (NH₃-TPD) and N₂ physisorption techniques. The catalytic performance of the SSZ-13 molecular sieves was evaluated by methanol to olefins (MTO) reaction. Results demonstrate that the crystallinity of the product significantly increases from 92.68% to 108.75% when the organic alkali TMAOH completely take place of the inorganic NaOH. The silica/alumina ratio in synthesis gel ranges from 33 to 100, thus accordingly enhancing the silica/alumina ratio of molecular sieves. Meanwhile, these materials possess large BET surface area of 800 m²/g and low strong acid amount, therefore exhibit longer catalytic lifetime and higher light olefin (ethylene + propylene) selectivity than conventional SSZ-13 catalysts in MTO reaction.