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Thermal Analysis Techniques in Chemical Engineering

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  1. Thermal Analysis Terry A. Ring Chemical Engineering University of Utah

  2. Different Techniques • Thermometric Titration (TT) • Heat of mixing • Thermal Mechanical Analysis (TMA) • Thermal Expansion Coefficient • Dynamic Mechanical Analysis (DMA) • Viscoelastic Properties • Differential Scanning Calorimetric (DSC) • Heat flow during Transitions • Thermal Gravimetric Analysis (TGA) • Weight Loss due to decomposition • Derivative Thermogravimetric Analysis (DTG) • Differential Thermal Analysis (DTA) • Heat of Transitions • Temperature Programmed Desorption (TPD) • Temperature at which gas is desorbed from (catalyst) surface • Emission gas Thermoanalysis (EGT)

  3. Basic Principle • Sample is heated at a constant heating rate • Sample’s Property Measured • Wt TGA • Size TMA • Heat Flow DSC • Temp DTA • Gas evolved TPD

  4. TGA • Constant Heating Rate • Initial Temp • Final Temp • Heating Rate (°C/min) • Data • Weight vs Time • Weight vs Temp. • Differential This Data (DTG)

  5. DSC

  6. DSC • Constant Heating Rate • Initial Temp • Final Temp • Heating Rate (°C/min) • Data • Heat flow to sample minus Heat flow to reference vs Time (Temp.) • Measures heat of crystallization Polymer without weight change in this temperature range

  7. DTA • Sample and Reference Placed in Heater • Constant Heating Rate • Initial Temp • Final Temp • Heating Rate (°C/min) • Data • Temp of Sample vs Time (or Temp) • Temp of Reference vs Time (or Temp) • Reference should be inert, e.g. nothing but latent heat • Measures • Heat of crystallization • Glass Transition Temperature

  8. DTA + DTG

  9. TMA • Constant Heating Rate • Initial Temp • Final Temp • Heating Rate (°C/min) • Data • Size of Sample vs Time (or Temp.) • Measures • Thermal Expansion Coefficient • Volume change on crystalization or crystal transformations • Sintering • Glass Transitions in Polymers

  10. TMA Polymer with glass transition

  11. DMA • Constant Heating Rate • Initial Temp • Final Temp • Heating Rate (°C/min) • Data • Force vs Time (or Temp.) • Force delay vs Time (or Temp.) • Viscoelastic Properties • Storage and Loss Modulus • Measures • Glass Transition • Viscoelastic Properties Polymer with Glass Transition

  12. We have TGA - only • Heating a sample of Calcium oxalate • Ca(C204)*xH2O  Ca(C204) *H2O + x-1 H2O • Ca(C204)*H2O Ca(C204) + H2O • Ca(C204)  CaCO3 + CO • CaCO3  CaO + CO2

  13. TGA • Constant Heating Rate • Initial Temp • Final Temp • Heating Rate (°C/min) • Data • Weight vs Time • Weight vs Temp. • Differential This Data (DTG)

  14. TGA – Ca(C204)*xH2O

  15. Different Heating Rates

  16. Heating Rate • Heating Too Fast • Overlaps Transitions • Interpretation Problems • Kinetics of Decomposition • Sample Size • Mass Transfer • Convective Mass Transfer • Pore Diffusion • Heat Transfer • Convective Heat Transfer • Thermal Conductivity • Porous solid

  17. Precipitated Zr5O8(SO4)2*15 H2O This sample was dried fro 48 hrs at 110C before TGA analysis. What is going on?

  18. Analysis of Filtrate from Precipitation • Precipitation • 5ZrOCl2 + 2H2SO4 + xH2O  Zr5O8(SO4)2*15 H2O (s) + 10 HCl • Decomposition • Zr5O8(SO4)2*15 H2O (s)  Zr5O8(SO4)2*14 H2O (s) + H2O (v) • Zr5O8(SO4)2 5 ZrO2 (s) +2 SO2 (v)

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