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Synthesis of hierarchical beta zeolite by using a bifunctional cationic polymer and the improved catalytic performance

机译：利用双功能阳离子聚合物合成分级β沸石及其改进的催化性能

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摘要

Hierarchical beta zeolites have been hydrothermally synthesized by using commercial cationic polymer PDADMA as both microporogen and mesoporogen. The influence of various synthetic parameters on the products was systematically investigated. Products with narrow SiO2/Al2O3 ratios were obtained under static crystallization conditions. By employing rotational conditions and adding seeds in the initial gel, higher SiO2/Al2O3 ratios over a wider range of 25 to 50 could be successfully achieved, which showed an obvious improvement. The C-13 NMR, TG, XRF, N-2 sorption as well as molecular mechanics simulation results indicated that PDADMA was incorporated in the final product without decomposition, acting as a SDA for the formation of beta zeolite and mesoporogen simultaneously. Further studies on the crystallization process revealed that hierarchical structures templated by PDADMA had been formed in the early solid. The amorphous Si-Al species around the micropore channels gradually evolved to the beta structure with the assistance of PDADMA, whereas the mesopores formed in the initial period remained less changed. A solid-mediated mechanism is thus proposed for the synthesis. Characterization results showed that the obtained products had sphere-like morphology composed of 10-20 nm crystalline domains, high mesopore volumes, and large external surface areas. More importantly, the hierarchical beta zeolites exhibited greatly enhanced catalytic activity and stability in the cracking reaction of triisopropylbenzene.
机译：通过使用商业阳离子聚合物PDADMA作为微孔原和中孔原，已经水热合成了分级β沸石。系统地研究了各种合成参数对产品的影响。在静态结晶条件下获得了具有窄SiO2 / Al2O3比的产品。通过采用旋转条件并在初始凝胶中添加种子，可以成功地在25至50的较宽范围内获得更高的SiO2 / Al2O3比，这显示出明显的改善。 C-13 NMR，TG，XRF，N-2吸附以及分子力学模拟结果表明，PDADMA被并入最终产物中而没有分解，同时作为SDA同时形成β沸石和介孔原。对结晶过程的进一步研究表明，由PDADMA模板化的分层结构已在早期固体中形成。在PDADMA的帮助下，微孔通道周围的非晶Si-Al物种逐渐演化为β结构，而在初始阶段形成的中孔变化较小。因此提出了用于合成的固体介导的机理。表征结果表明，所获得的产物具有由10-20nm的晶域，高的中孔体积和大的外表面积组成的球形样形态。更重要的是，分层的β沸石在三异丙基苯的裂化反应中表现出大大增强的催化活性和稳定性。

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