# Particle Formation Mechanism of TiCl\({}_{4}\) Hydrolysis to Prepare Nano TiO\({}_{2}\)
###### Abstract  
This study utilizes Aspen Plus chemical process simulation software (V11), applies uniform nucleation theory and growth kinetics equations, and explores the particle formation mechanism of TiCl\({}_{4}\) hydrolysis to prepare nano TiO\({}_{2}\). In the water/ethanol system, the effects of the reaction time, reaction temperature, water addition, pH value, and ethanol amount on the crystal nucleation rate and TiO\({}_{2}\) particle distribution (PSD) were studied in detail by adding triethanolamine dropwise and using the Aspen Plus chemical process software simulation calculation method. The calculation results indicate that at room temperature, the formation of TiO\({}_{2}\) crystal nuclei mainly occurs in the first 300 s and then enters the growth stage. The reaction was carried out under neutral conditions at room temperature for 4 h in 1 mL TiCl\({}_{4}\), 6 mL C\({}_{6}\)H\({}_{15}\)NO\({}_{3}\), 15 mL H\({}_{2}\)O, and 30 mL C\({}_{2}\)H\({}_{5}\)OH. The maximum number of particles reached 195 mesh per cubic micrometer, and the particle size after crystal nucleus growth was smaller, with a D\({}_{50}\) of 6.15 nm. The distribution curve shows a normal distribution, which is basically consistent with the experimental results. When studying various factors, it was found that controlling the reaction time within 60 min and maintaining the reaction temperature at room temperature can reduce the particle size D\({}_{50}\) to 2.44 nm. Continuing to adjust the amount of water added, it was found that at 1 mL, D\({}_{50}\) decreased again to 0.19 nm. Adjusting the pH value found that maintaining the neutrality did not change the particle size. Continuing to adjust ethanol, it was found that adding an appropriate amount of ethanol promoted nucleation and growth. At 4 mL, the maximum number of particles reached 199 mesh per cubic micrometer, but D\({}_{50}\) slightly increased to 0.24 nm. TiCl\({}_{4}\) hydrolysis; particle formation mechanism; Aspen Plus chemical process simulation; particle distribution +
Footnote †: journal: Applied Sciences  
Despite the prevalent use of TiCl\({}_{4}\) hydrolysis in nano-TiO\({}_{2}\) synthesis, the mechanisms underpinning particle formation remain largely unexplored. Prior research has primarily investigated experimental methodologies to optimize nano-TiO\({}_{2}\) synthesis, rarely integrating computational simulations. Much of the existing work is grounded in theoretical formula analyses. For instance, [PERSON] et al. [8] elucidated the phase transition principles from ilmenite to niobite during titanium dioxide crystal production using quantum dynamics simulations. However, this research is not exhaustive, relying solely on theoretical foundations and experimentation, without adequate consideration of experimental errors and limitations. In contrast, [PERSON] et al. [9] examined the elastic properties of anatase nanotubes via Molecular Dynamics (MD) simulations. Such investigations, however, lean more towards kinetic models pertinent to adsorption and photocatalysis coupling simulation software with fundamental computations. Furthermore, the majority of studies focus excessively on the attributes of final products [10; 11], such as photocatalysis [12] and ultraviolet light absorption capacities [13]. Although these studies enhance our understanding of material properties, they fall short of offering comprehensive insights into and control over the physicochemical characteristics of nano-TiO\({}_{2}\), particularly concerning the particle formation mechanism. The interconnected processes of mass transfer, energy transfer, and separation occur on various scales, potentially ranging from the molecular to the macroscopic. To comprehensively understand and optimize these processes, multi-scale simulations are required. Aspen Plus [14] is a powerful tool capable of performing such analyses, with exceptional capabilities for solving chemical reactions, and material and energy balances.