基于介尺度解聚-重组装的分子筛材料的制备和性能调控：从天然矿物合成分子筛的基础研究

Modern industrial synthesis of aluminosilicate molecular sieves typically involves the use of aluminum- and silicon-containing inorganic chemicals that are derived from natural bauxite and quartz minerals through complicated processes associated with huge waste generation and extensive energy consumption. Furthermore, the most common and successful approach so far for synthesizing hierarchical zeolites is to introduce a hard or soft mesoscale template into the zeolite synthesis system, however, its large scale application looks bleak because of the high cost and serious environmental pollution associated with the use of mesopore/macropore-directing templates. Therefore, direct synthesis of molecular sieves from natural aluminosilicates through a “green chemistry” route without experiencing any intermediate steps to produce chemicals and without using any mesoscale/macroscale template has been pursued in recent years because of its great potential in reducing the generation of hazardous wastes, saving energy, and possibly altering the properties of the resulting molecular sieve. By systematically investigating the depolymerization behavior of highly polymerized natural aluminosilicates in different activation processes and the re-assembly behavior of the mesoscale structures formed after activation, this proposal aims at developing a novel submolten salt activation method to efficiently depolymize natural aluminosilicates and manipulate the mesoscale structure of the resulting activation products, understanding the relationship between mesoscale structure, reactivity and self-assembly behavior, and establishing a generic green route to synthesizing aluminosilicate molecular sieves directly from natural aluminosilicate minerals. Additionally, we will explore the possibility to synthesize hierarchical zeolites via the assembly of mesoscale zeolite precursors with using any secondary mesoscale/macroscale template and aluminum- and silicon-containing chemicals. It is hoped that the success of this proposed project will revolutionize the traditional synthesis route of aluminosilicate molecular sieves that heavily relies on the use of chemicals.

作为现代化学工业的基石，硅铝分子筛已被广泛应用于石油化工、精细化工、日用化工以及环境保护等领域。虽然基于分子筛材料的分离和催化过程被认为是绿色过程工业发展的重要方向，然而无论是传统的微孔分子筛材料的合成，还是基于模板组装的介孔、多级孔分子筛材料的合成，均不是绿色的合成过程，这就给基于分子筛材料的分离和催化过程从源头实现绿色化带来了巨大的挑战。本项目拟基于对天然硅铝矿物在介尺度上的解组装-重组装过程的基础研究，发展有效活化天然硅铝矿物、调控其介尺度结构的方法，建立天然硅铝矿物活化产物的介尺度结构-反应活性-组装行为之间系统关联，形成不依赖于无机化工产品硅铝源的分子筛绿色合成新方法，尝试基于分子筛纳米晶介尺度聚集体的多样化组装，探索在无介(大)孔模板剂的导向作用下完全从天然硅铝矿物的介尺度活化产物制备多级孔道催化材料的新途径，为分子筛的绿色合成和高性能化制备奠定理论基础和提供技术源头。

作为现代化学工业的基石，硅铝分子筛已被广泛应用于石油化工、精细化工、日用化工以及环境保护等领域。虽然基于分子筛材料的分离和催化过程被认为是绿色过程工业发展的重要方向，然而无论是传统的微孔分子筛材料的合成，还是基于模板组装的介孔、等级孔分子筛材料的合成，均不是绿色的合成过程，这就给基于分子筛材料的分离和催化过程从源头实现绿色化带来了巨大的挑战。本项目基于对天然硅铝矿物在介尺度上的解组装-重组装过程的基础研究，发展了基于天然硅铝矿物的分子筛绿色合成和高性能化制备新过程。所取得的主要进展如下：(1) 首创了耦合机械-化学作用的黏土矿物拟固相解聚方法，解聚温度和时间分别从800 oC和4 h降到100 oC和0.5 h；(2)基于分子筛纳米晶介尺度聚集体的多样化，发展出了在无介(大)孔模板剂的导向作用下基于介尺度组装等级孔分子筛材料的绿色合成新路线，创制出了等级孔ZSM-5分子筛材料；(3)首次完成了等级孔ZSM-5分子筛的规模化生产，并率先实现了其在催化裂化(FCC)汽油加氢改质中的工业应用，总加工能力达到660万吨/年，突破了降低汽油烯烃含量与保持辛烷值这一制约国VI清洁汽油生产的卡脖子问题。该项目的成功实施为分子筛的绿色合成、高性能化制备和规模化应用奠定理论基础和提供技术源头。