Dehua Wang,Beibei Gao,Dong Fan,Miao Yang,Peng Tian,Zhongmin Liu
Two novel SAPO molecular sieves, detonated as DNL-8 and DNL-9, were synthesized by an aminothermal co-templating strategy. This approach employed diisopropanolamine (DIPA) as both the solvent and the primary organic structure-directing agent (OSDA), with benzyltrimethylammonium chloride (BTACl) or trimethylamine (TMA) serving as a co-OSDA. 13C MAS NMR results demonstrate that the organics occluded in the crystals are the combination of TMA & DIPA for both samples. Three-dimensional (3D) rotation electron diffraction (RED) was used to elucidate their structures, revealing that both the DNL-8 and DNL-9 are the intergrowth of CHA/GME framework. In combination with the simulated XRD patterns of the intergrowths, the GME/CHA ratio is estimated to be 80%GME/20%CHA for DNL-8 and 20%GME/80%CHA for DNL-9. Interestingly, DNL-9 exhibits remarkable catalytic performance in the methanol amination reaction with a super-high selectivity of monomethylamine (MMA) plus dimethylamine (DMA) (~ 96 wt%), suggesting its potential application for the synthesis of MMA and DMA.
Yuan Hu,Yuan-Yuan Yue,Chan Wang,Hai-Bo Zhu,S. Ted Oyama,Xiao-Jun Bao
Hierarchical zeolites show great promise in green chemical and petrochemical processes, but their syntheses usually involve the use of nitrogen-/halogen-containing templates whose removal from the as-synthesized zeolites via calcination inevitably leads to serious environmental pollution, high energy consumption and sometimes destruction of zeolite frameworks. We report an eco-friendly and acid-degradable polymer denoted as PK3 as a multifunctional template to synthesize single-crystal hierarchical zeolites. It is shown that by strongly interacting with zeolite aluminosilicate gel precursors, PK3 acts as a structure-directing agent for the nucleation and crystallization of the amorphous gel into protozeolite crystals, and via its adsorption on the surfaces of protozeolite crystals, PK3 greatly inhibits their growth and thereby results in the formation of zeolitic nanocrystals. Furthermore, these thermodynamically unstable nanocrystals encapsulating PK3 spontaneously aggregate, then align in an oriented manner, and at last ripen, leading to the formation of single-crystal zeolite particles with interconnected mesopores. Importantly, the removal of PK3 from the as-synthesized zeolites can be achieved by a simple acid treatment. Thanks to these unique characteristics of PK3, a nitrogen-/halogen-free and combustion-free route is successfully achieved for synthesizing hierarchical MFI, MOR and GME zeolites. Moreover, the synthesized MFI zeolite exhibits superior catalytic activity in cracking low-density polyethylene.
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