2024 AIChE Annual Meeting

(242g) Investigation of the Effect of pH and Temperature on the Dispersion of MoOx Species on Transition Metal Oxide Supports

Authors

Tsilomelekis, G. - Presenter, Rutgers University
Thirulogachandar, D., Rutgers, The State University of New Jersey
Hu, H., RUTGERS THE STATE UNIVERSITY OF NJ
Molybdenum oxide supported on transition metal oxides are commonly used in the chemical and petrochemical industries for various reactions. Their performance depends strongly on a) the type of oxo-molybdenum sites present on the surface of supports and b) the nature and properties of the support used. It is shown in the literature that the nature of active molybdenum species spans a wide range of structures ranging from polymeric [(MoOx)] species to monomers with different number of terminal Mo=O functionalities. Controlling at the molecular level such sites require a thorough understanding of their synthesis method, especially during their adsorption stage on the supports.

In this work, we utilize in-situ Raman and ATR-FTIR measurements with simultaneous monitoring and control of the pH and temperature in one single vessel to study a) speciation dynamics and b) adsorption of MoOx species on the surface of various commercial support pellets. The equilibrium between the different molybdenum species is monitored spectroscopically and relevant model is developed. We show that the temperature significantly affects the distribution of the MoOx species in solution, specifically by shifting the equilibrium towards monomeric species at similar pH values. Moreover, we monitor in real time the adsorption of MoOx species on the surface of different supports thus enabling the development of data driven adsorption models for better synthesis control. Lastly, we utilize the concept of 2D-COS in Raman spectroscopic data to investigate the sequence of the adsorption of competing molybdenum sites as well as the possible influence of adsorption dynamics by leaching of other surface species present in the commercial catalyst supports.