In situ diagnostics of zeolite crystallization by ultrasonic monitoring

The crystal growth of zeolites A and X was tracked by the on-line monitoring of the transport properties of ultrasonic (US) waves in the reaction mixture during the crystallization. Characteristic variations in the mechanical properties of the synthesis gels caused by its development and the onset and the completion of the crystal growth step have been identified by the phase sensitive measurement of the velocity and amplitude of ultrasonic (US) waves. This was verified by ex situ XRD analysis and particle size measurements. The interaction of gel and US waves is discussed. It is demonstrated that real-time in situ US diagnostics are a promising tool for the investigation of zeolite crystallization and for industrial process control.