Geometric Model for Predicting the Morphology Evolution of a Multiparticle Agglomerate during Simultaneous Reaction and Sintering

SUJIT MODI, Onochie Okonkwo, Hao Zhou, Shalinee Kavadiya, Marcus Foston, Pratim Biswas, Washington University in St Louis

     Abstract Number: 193
     Working Group: Aerosol Physics

Abstract
The size and surface area of nanosized agglomerates play a crucial role in determining their performance in healthcare, energy storage, and catalysis ^[1]. Sintering rate, which governs the agglomerate size and the morphology, is traditionally obtained using mobility size techniques ^[2]. However, for materials that undergo decomposition reactions at sintering temperature the effect of the reaction on the observed mobility size change must be accounted for accurate estimation of sintering rates. To the best of our knowledge, existing modeling studies of sintering haven’t accounted for the simultaneous reactions. Thus, the sintering rate of a range of materials such as biomaterials including lignin and chitosan remains undetermined. In this study, we developed a novel geometric model (GM) to predict the evolution of size and morphology under simultaneous sintering and reaction. The model focus is on estimating sintering preexponential factor and activation energy, which are required to predict the evolution in size and morphology with time and temperature. Additionally, to demonstrate the application of developed GM, an alkali type lignin is used as a model compound and its preexponential factor and activation energy were estimated to be 6.6x10^-8 s. nm^-1 and 116.4 kJ (K. mol)^-1 respectively. Predictions of size and morphology using estimated values agreed with independent experimental measurements. This study provides first-time key insights into sintering rates of the lignin and provides operational guidelines for minimal aggregation and smooth operation in its continuous pyrolysis reactors. The developed GM is generalized and can also be applied to study other materials.

[1] Martins et al., Journal of Geophysical Research: Atmospheres 103, 32041-32050, 1998
[2] Cho et al., Aerosol science and technology 40, 309-319, 2006