Advances in High Temperature Oxygen Analysis
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This document summarizes a webinar about oxygen analysis using the rapid OXY cube. It discusses the advantages of high temperature oxygen determination at 1500°C compared to lower temperature methods. The rapid OXY cube allows matrix-independent oxygen analysis using glassy carbon tubes. It also features backflush chromatography to remove interfering gases and ensure accurate results. Examples are given showing the instrument's use for coal, fuels, liquids and other samples.
![Boudouard Equilibrium At a Glance
4/27/2015 Webinar
• The higher the temperature, the
more CO.
• T > 1000°C for sub-percent CO2
formation.
• T > 1200°C requires unique
technical solutions.
T [°C] CO2 [%] CO [%]
450 98 2
600 77 23
700 42 58
800 6 94
900 3 97
1000 1 99](https://image.slidesharecdn.com/2015-04advancesinhightemperatureoxygenanalysis-150428024605-conversion-gate01/85/Advances-in-High-Temperature-Oxygen-Analysis-8-320.jpg)
Advances in High Temperature Oxygen Analysis
- 1. Advances in High Temperature Oxygen Analysis April, 27th 2015 Dr. Dominik Margraf Webinar
- 2. 4/27/2015 Webinar Content Introduction1 "high T" vs. "low T" oxygen determination2 rapid OXY cube features3 Application Examples4 Summary5
- 3. Why Oxygen Analysis? 4/27/2015 Webinar • Oxygen is an important parameter to describe: • coke and coal (ASTM D3176) • gasoline and methanol fuels (ASTM D5622) • polymers (fire resistance) • fine chemicals (quality control) • two approaches: • indirect: 100% - CHN% - S% - ash% = O% • direct measurement via pyrolysis
- 4. Indirect Oxygen Analysis • indirect approach: 100% - CHN% - S% - ash% = O% • mainly applied to coal and coke • drawbacks: • time and resources consuming • summation of errors • up to three instruments required 4/27/2015 Webinar
- 5. CHN + S according to ASTM D3176 4/27/2015 Webinar • CHN with vario MACRO cube compliant to ASTM D5373 • S with rapid CS cube in S mode compliant to ASTM D4239
- 6. Direct Oxygen Analysis: Reductive Pyrolysis • sample is combusted in helium atmosphere in presence of carbon (C) • sample oxygen (O) is converted to carbon monoxide (CO) • CO is detected • simplified chemical representation: O2 + 2 C 2 CO • basic prerequisite: all oxygen must be converted to CO 4/27/2015 Webinar
- 7. Simplified Pyrolysis Chemistry basic prerequisite for accurate measurements: all O2 must be converted to CO, but • CO may react with carbon to CO2 and vice versa • 2 CO ⇆ CO2 + C (Boudouard equilibrium) depending on temperature a mixture of CO and CO2 results leading to wrong oxygen content 4/27/2015 Webinar
- 8. Boudouard Equilibrium At a Glance 4/27/2015 Webinar • The higher the temperature, the more CO. • T > 1000°C for sub-percent CO2 formation. • T > 1200°C requires unique technical solutions. T [°C] CO2 [%] CO [%] 450 98 2 600 77 23 700 42 58 800 6 94 900 3 97 1000 1 99
- 9. 4/27/2015 Webinar Content Introduction1 "high T" vs. "low T" oxygen determination2 rapid OXY cube features3 Application Examples4 Summary5
- 10. “high T” vs. “low T” oxygen determination 4/27/2015 Webinar • temperature approx. 1500°C • matrix independent, no CO2 formation • temperature approx. 1100°C • matrix dependent, (sub)-percent CO2 formation “low T” oxygen determinationrapid OXY cube
- 11. Drawbacks of “low T” oxygen determination • Matrix dependency causes frequent, time consuming calibration • Sulfates / phosphates are hard to digest leading to wrong experimental results • Fluorinated species damage quartz glass reactors (SiO2 + 4 HF SiF4 + 2 H2O) • Fluorinated species yield erroneous results 4/27/2015 Webinar
- 12. “high T” vs. “low T” oxygen determination 4/27/2015 Webinar • temperature approx. 1500°C • matrix independent, no CO2 formation • no matrix standards needed • excellent, highly precise results • ready to go, stand-alone analyzer • temperature approx. 1100°C • matrix dependent, sub-percent CO2 formation • frequent matrix standards needed • “good” – “very good” results “low T” oxygen determinationrapid OXY cube
- 13. CHNS + O packages 4/27/2015 Webinar • The perfect solution for CHNS + O analysis: • vario MICRO, EL or MACRO cube for CHNS • rapid OXY cube for high end O analysis • two independent instruments • attractive package price
- 14. 4/27/2015 Webinar Content Introduction1 "high T" vs. "low T" oxygen determination2 rapid OXY cube features3 Application Examples4 Summary5
- 15. rapid OXY cube features 4/27/2015 Webinar • world’s only stand-alone, dedicated oxygen analyzer • benchtop instrument • standard electric supply • full digital control
- 16. rapid OXY cube features 4/27/2015 Webinar • convenient slide-out furnace • no tool access • double reactor design using an outer ceramic tube with glassy carbon insert
- 17. rapid OXY cube features 4/27/2015 Webinar • inner and outer tube • Sample gas inside inner glassy carbon tube • Protecting gas between inner glassy carbon tube and outer ceramic tube • Protecting gas helium or inexpensive argon
- 18. glassy carbon vs. „low T quartz tube“ 4/27/2015 Webinar • no bloating of quartz glass tube (might lead to furnace damage) • no background from glassy carbon (fluorine containing samples release oxygen from quartz glass) • short life time of pyrolysis quartz tube • life time glassy carbon tube: just don’t drop it on the floor! bloated quartz glass pyrolysis tube
- 19. rapid OXY cube functional principle 4/27/2015 Webinar InletFeeder Sample Input • sample wrapped in silver foil • sample inlet via patented, blank-free ball valve
- 20. rapid OXY cube functional principle 4/27/2015 Webinar Gas Formation Pyrolysis helium InletFeeder Sample Input • 1500°C • glassy carbon pyrolysis tube • sample wrapped in silver foil • sample inlet via patented, blank-free ball valve
- 21. rapid OXY cube functional principle 4/27/2015 Webinar Gas Formation Pyrolysis helium InletFeeder Sample Input helium TCD Detector out Detector in Gas Handling Detection U CO absorption column • CO trapped with advanced purge & trap column • Release of CO via temperature controlled desorption for excellent • peak separation • peak focusing • N2, H2, CH4 recorded as dummy peaks • CO is quantified • 1500°C • glassy carbon pyrolysis tube • sample wrapped in silver foil • sample inlet via patented, blank-free ball valve
- 22. General Chemistry Problem 4/27/2015 Webinar • Problem: pyrolysis is not as well defined as combustion • Unwanted pyrolysis gases from slow reactions pollute clean carrier gas after quantitative CO absorption on purge & trap column • wrong results
- 23. General Chemistry Problem 4/27/2015 Webinar • Problem: pyrolysis is not as well defined as combustion • Unwanted pyrolysis gases from slow reactions pollute clean carrier gas after quantitative CO absorption on purge & trap column • wrong results • Solution: Elementar’s unique backflush chromatography
- 24. without backflush chromatography 4/27/2015 Webinar Gas Formation Pyrolysis helium flow InletFeeder Sample Input helium reference TCD Detector out Detector in Gas Handling Detection U CO absorption column background from unwanted pyrolysis gases (general chemistry problem) are flushed with helium carrier gas into TCD causing wrong experimental results
- 25. Analysis of caffeine without backflush 4/27/2015 Webinar • perfect peak separation via advanced purge & trap chromatography • descending CO baseline owing to unwanted pyrolysis gases entering TCD
- 26. with backflush chromatography 4/27/2015 Webinar Gas Formation Pyrolysis helium flow InletFeeder Sample Input helium reference TCD Detector out Detector in Gas Handling Detection U CO absorption column • pyrolysis tube is by-passed after trapping CO • desorption of CO with clean helium
- 27. Analysis of caffeine with backflush 4/27/2015 Webinar • perfect peak separation via advanced purge & trap chromatography • perfect CO baseline for highly accurate results
- 28. backflush chromatography 4/27/2015 Webinar • Problem: Pyrolysis is not as well defined as combustion. Interferences can lead to wrong results. • Solution: backflush chromatography • Adsorption of CO during pyrolysis phase • Desorption with clean helium by-passing pyrolysis tube • Result: perfect baseline, full recovery, accurate measurement
- 30. 4/27/2015 Webinar Content Introduction1 "high T" vs. "low T" oxygen determination2 rapid OXY cube features3 Application Examples4 Summary5
- 31. How to tackle hygroscopic samples such as coal 4/27/2015 Webinar • water residues in samples or hygroscopic samples lead to wrong oxygen content • coal is commonly dried at 105°C under inert atmosphere prior to elemental analysis • no tedious drying steps with 80°C DrySampleTM carousel
- 32. rapid OXY cube liquid injection 4/27/2015 Webinar • 50 positions with auto-clean • up to 100 µl injection volume • temperature control available rapid OXY cube + automated liquid sample system
- 33. liquid samples: proof of principle 4/27/2015 Webinar • 34 consecutive 1-hexanol injections • theoretical value: 15.66% • mean: 15.65% • abs. SD: 0.03% • excellent results • excellent repeatability • excellent accuracy
- 34. Oxygen Content in Gasoline Blending 4/27/2015 Webinar • oxygen content correlates to unwanted CO emission in engines • minimum oxygen content is legal requirement (e.g. Clean Air Act) • pure fossil gasoline with low oxygen content is blended with high oxygen content biofuels
- 35. 4/27/2015 Webinar Content Introduction1 "high T" vs. "low T" oxygen determination2 rapid OXY cube features3 Application Examples4 Summary5
- 36. Your advantages at a glance: • no distortion of analytical results through interfering gases • unmatched user-friendliness and highest operating comfort • Sample weights < 1 mg - 300 mg • long life time of pyrolysis tube 4/27/2015 Webinar
- 37. Elementar thanks for your attention ! further questions? margraf@elementar.de 4/27/2015 Webinar