The green and sustainable synthesis of nanometer ZSM-5 without organotemplates via utilizing the recycled mother liquid

Abstract

The development of green and sustainable techniques for synthesizing classes of significant industrial materials, like zeolites, has been recognized as an inevitable trend in recent years. Herein, an efficient and environmentally friendly route was exploited for the synthesis of nanometer ZSM-5 zeolites with recycled mother liquid and seed-assistance. Physical characterization and component analysis revealed that the unutilized species in the raw materials remain in a stable concentration range during the nine recycling experiments, and these recyclable species were successfully applied for the preparation of ZSM-5 zeolites as part of the raw materials. It is noticed that the particle size of the ZSM-5 aggregates (∼0.3–0.5 μm) synthesized from the recycled mother liquid sharply decreases compared to that using fresh catalyst (∼1.1–1.4 μm), which is attributed to the synergetic effect of the self-made S-1 seeds and the primary structural units with memory effects in the mother liquid, which is helpful for promoting the formation of small-sized particles. Furthermore, the as-obtained samples possess almost the same catalytic performance in cyclohexene hydration as fresh catalyst, even though the mother liquid was recycled nine times. These satisfactory results indicate that this cycled synthesis process effectively utilized the ingredients in the mother liquid and avoided waste liquid discharge to achieve clean and efficient synthesis. Additionally, the green process opens a pathway to sustainable zeolite preparation in industry compared to conventional methods.