Highly atom-economic synthesis and scale-up production of zinc-aluminum layered double hydroxides

• Published in: Chemical engineering science 2024-01, Vol.283, p.119376, Article 119376
• Main Authors: Li, Kaitao, Li, Wenze, Zhao, Yifan, Liu, Wendi, Tian, Rui, Lin, Yanjun
• Format: Article
• Language: English
• Subjects: Atomic economic reaction; Layered double hydroxides; Reaction mechanism; Scale-up; Smoke suppression property; Structural stability
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2023.119376

A novel, one-step and green reaction route with 100% atom economy was proposed to prepare ZnAl LDHs based on a “dissolution-nucleation-diffusion” reaction mechanism. [Display omitted] •A novel one-step, green reaction method with 100% atom economy is proposed to prepare ZnAl LDHs to replace the traditional coprecipitation method for industrial production.•A dissolution–nucleation–diffusion mechanism is presented for the formation of ZnAl LDHs with a two-dimensional diffusion process as the rate-determining step according to the D2 kinetic model.•Structure studies revealed that ZnO6 hexahedral structure in ZnAl LDHs was less stable than ZnO4 tetrahedral structure in ZnO at high temperature (≥160 °C), which is beneficial for reaction process control to prepare pure ZnAl LDHs.•The ZnAl LDHs reduced the smoke density of PVC by 51.8 %, the scaled-up production was realized on a 1000 t/a industrial production line. ZnAl layered double hydroxides (LDHs) has been widely applied as functional additives in polymers. The common coprecipitation method used to synthesize ZnAl LDHs has an atomic utilization of only 44.35 %, and is accompanied with the formation of sodium salt by-product, ZnO impurities and lots of waste water. In this work, we proposed a green and cost-effective synthesis route with 100 % atom economy to prepare ZnAl LDHs from mixed metal oxides and hydroxides. Pure ZnAl LDHs was synthesized at 120 °C. A dissolution-nucleation-diffusion reaction mechanism was proposed through structural and morphological studies and reaction kinetics calculations. The prepared ZnAl LDHs exhibited excellent smoke suppression properties, with a reduction in the smoke density of PVC from 705 to 340. This proposed method was successfully scaled-up and applied on a 1000 t/a industrial production line, providing a valuable opportunity for the reaction design and large-scale preparation of LDHs and other inorganic compounds.