结构导向剂局部环境的能量学对沸石合成的影响,Chemistry of Materials

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结构导向剂局部环境的能量学对沸石合成的影响
Chemistry of Materials ( IF 7.2 ) Pub Date : 2021-03-05 , DOI: 10.1021/acs.chemmater.0c04796
Stacey I. Zones ₁ , K. Jayanthi ₂ , Jesus Pascual ₁ , Dan Xie ₁ , Alexandra Navrotsky ₂

Affiliation

有机结构导向剂（SDA）在合成具有新型骨架和组成的SSZ-13（CHA结构）等沸石中起着至关重要的作用。从水性环境中除去疏水性SDA有机阳离子并将其掺入新兴的硅酸盐骨架中，有助于沸石的结晶。这项研究结合了几种实验方法，以了解随着SDA尺寸的改变，对成核形成SSZ-13的影响。我们研究了结晶速率，然后对产品中的SDA拟合进行建模以查看速率的相关性，然后对产品中SDA沸石的填充量进行了测量。然后，我们确定了转移相同系列有机SDA的驱动力，（C / N ⁺= 7–16）从水到氯仿，后者代表了亲水性较低的沸石环境。水和氯仿中每种SDA的溶解焓的量热法测量均提供了焓数据，并且在室温下均测量了转移反应的分布系数。从这些实验中，计算出相应的转移焓，熵和自由能。转移过程的热力学参数取决于C / N ⁺SDA结构中电荷的比率，位置和环境，是SDA制备目标沸石SSZ-13（CHA）的能力的良好度量。但是，在这种特殊的沸石合成中使用特殊的亲水性SDA作为反例也产生了快速的结晶速率，并证明通过SDA的对接结合最佳的SDA-fit，引发成核的机会可以提供SDA的最佳使用，提供了比溶液传递热力学更强的因子。

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Energetics of the Local Environment of Structure-Directing Agents Influence Zeolite Synthesis

Organic structure-directing agents (SDAs) play a crucial role in the synthesis of zeolites like SSZ-13 (CHA structure), with novel frameworks and compositions. Zeolite crystallization is aided by the removal of the hydrophobic SDA organocations from an aqueous environment and their incorporation into an emerging silicate framework. This study combined several experimental approaches to understand the influence on nucleation to form SSZ-13 as the size of the SDA was changed. We studied crystallization rates, then modeled the SDA fit in the product to look at correlations for the rates, and then performed the measurement of SDA zeolite filling in the products. Then, we moved to determine the driving force for the transfer of this same series of organic SDAs, (C/N⁺ = 7–16) from water to chloroform, the latter a proxy for a much less hydrophilic zeolitic environment. Calorimetric measurements of dissolution enthalpy for each SDA in water and chloroform provided enthalpy data and the distribution coefficients for the transfer reaction were measured, both at room temperature. From these experiments, the corresponding transfer enthalpy, entropy, and free energy were calculated. The thermodynamic parameters of the transfer process depend on the C/N⁺ ratio, location, and environment of the charge in the SDA structure and are a good measure of the ability of the SDA to make the target zeolite, SSZ-13 (CHA). However, the use of a particular, hydrophilic SDA as a counter-example in this particular zeolite synthesis also produced rapid crystallization rates and demonstrated that the opportunity to initiate nucleation, by virtue of docking of the SDA coupled with best SDA-fit, may provide the optimum use of the SDA, providing a stronger factor than the solution transfer thermodynamics.

更新日期：2021-03-23

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