Acoustic and spectrometric monitoring of a heterogeneous reaction

1
Acoustic and spectrometric monitoring of a
heterogeneous reaction

• Alison Nordon,1 Luke Bellamy,1 Anthony Gachagan,2
  Gordon Hayward2 and David Littlejohn,1
• 1Department of Pure and Applied Chemistry/CPACT,
• 2Centre for Ultrasonic Engineering,
• University of Strathclyde, Glasgow, UK.

2
Introduction

• Acoustics used widely in construction industry,
  medicine and for underwater measurements
• Now starting to be used for process monitoring

• Active
• Velocity and attenuation

• Two types of acoustic measurements

• Passive (emission)

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Aim

• Investigate experimental factors that affect the
  passive acoustic signal
• Assess potential of passive acoustics for the
  monitoring of a heterogeneous reaction

4
Broadband acoustic emission system

• Transducers
• 150-1000 kHz (resonant mode at 90 kHz)
• 150-750 kHz

5
Signal processing
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Investigation of factors

• Itaconic acid in toluene used as a model system
• Factors investigated
• Repeatability of transducer attachment
• Position of transducer
• Particle concentration
• Particle size
• Stir rate
• Fill level

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1 L reactor
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200 g of itaconic acid in toluene(transducer 2)
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Transducer attachment(transducer 2)

• Same position (3)
• Transducer fixed
• RSD 1.6 (n5)
• Transducer reattached ?5
• RSD 7.5 (n25)
• Different positions (1-6)
• Largest RSD (23.6 ) for position 1 (n9)
• Statistically, no difference between signal area
  for position 3 and positions 1, 2, 4 or 5
• Principal component analysis shows that acoustic
  spectra at positions 3, 4 and 5 are similar

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Effect of concentration(transducer 1)
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Effect of concentration(transducer 1)
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Effect of particle size(transducer 1)
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Effect of stir rate(transducer 1)
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Effect of fill level(transducer 1)
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Heterogeneous reaction

• Esterification of itaconic acid with 1-butanol in
  toluene used as a model heterogeneous reaction

• Varied reaction conditions
• butanolitaconic acid
• temperature

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21 butanolitaconic acid at 70 C(transducer 1)
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Total ester concentration - HPLC
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Effect of butanol concentration(transducer 1)
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Effect of butanol concentration - HPLC
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Effect of temperature(transducer 1)
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Effect of temperature - HPLC
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Conclusions

• Signal transmitted through and around vessel wall
• ? not just from particulates close to the
  transducer
• Between run repeatability affected by variability
  of transducer attachment
• Acoustic signals sensitive to
• concentration of particulates
• particle size
• stir rate
• Such changes can be used for process monitoring,
  kinetic studies and end-point detection
• e.g. consumption of solid material in a
  heterogeneous reaction

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Acknowledgements

• Douglas McNab, CUE
• Paul Frake, GSK
• Ruth Waddell, CPACT