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Trends and Developments in Process GC in the Petrochemical Industry Tom Lynch

Trends and Developments in Process GC in the Petrochemical Industry Tom Lynch BP Chemicals, Hull, England. Future Strategy for Process Plant Analysis.

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Trends and Developments in Process GC in the Petrochemical Industry Tom Lynch

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  1. Trends and Developments in Process GC in the Petrochemical Industry Tom Lynch BP Chemicals, Hull, England

  2. Future Strategyfor Process Plant Analysis • Petrochemical plants are large high volume assets often producing several hundred thousand tonnes per year (Hull has 6 plants making >2m TPA) • Goal—Provide faster real-time control of processes and product release through application of new analyser technology. • Consequence—reduce routine lab testing and move to on-line and at-line analysis. • Laboratory becomes a function focussed on the development of on-line and at-line process analysis and specialist problem solving.

  3. Conventional Process GC Or back to the time when Dinosaurs still walked on the earth! • Safety requirements – Certification (limits performance). • Generally single application, may use sample stream switching. • Generally Packed columns • Air bath isothermal ovens • Simple detectors, generally max of 2 per instrument • Short cycle time can be very important • Simple but inflexible data processing • Relied heavily on column switching and multidimensional techniques with valves to achieve separations • Operator interaction via a screen on the instrument So What’s Changed?

  4. The Siemens Advance Maxum 2 Process GC • Complete Plug and Play Components • Dual Air Bath or Dual Airless Ovens • 8 Channels of EPC • Flexible 10 port valves (>12) • New Detectors • TCD 6 measurement and 2 reference cells per unit • FID with integral independant heater • up to 3 detector units per GC ( eg 24 TCD cells) • Capillary columns • “Live Switching Technology” • Parallel Chromatography • EZChrom software for control and data processing • Open system & Network Communications

  5. Siemens:- Live Switching • Live Switching isused exclusively by Siemens in their On-Line GCs and has many advantages over conventional valve switching including • Suitable for use with packed and capillary columns, very low dead volume. • Completely pneumatic - no mechanical valves (more reliable). • Inert system, important for highly active compounds such as organic acids. • One live –T piece can replace 2 conventional valves!!

  6. EPC 2 EPC 3 EPC 1 NV SPLIT NV NV PURGE CUT OUTLET OUTLET Standard Pressure Control Electronic Pressure Control Simplifying Multidimensional Chromatography

  7. Methyl Acetate Process Stream • Crucial forprocess control result determines whether stream is diverted to off spec. • Currently carried out using 2 analysers • One for methanol (~10%) and water (~1%) • The other for ppm butyl acetate (normally <5ppm) • Main aim is to carry out both analysis on one instrument • Secondary aim is to include other components of interest such as methyl acetate (85%) and the other impurities, namely acetone (0.1%) and ethyl methyl ketone (EMK) (250ppm), could be useful.

  8. Methyl Acetate Process StreamThe “live-T “ solution • 2 x 30m 0.32id DB 624 columns joined by “live T” • Cut from column 1 outlet to FID for ppm levels • Straight to column 2 for further separation and detection by TCD for water and other % level components

  9. Methyl Acetate Stream: Chromatograms • The sample is injected onto Column 1 and the early eluting components namely water, methanol, acetone, and methyl acetate are allowed to continue through to Column 2 for further separation and then detection by the TCD. • After the methyl acetate has passed into column 2 the live T is activated and the later eluting components, namely EMK and butyl acetate are directed out the cut vent for detection at the FID.

  10. -0.0100 -0.0105 -0.0110 -0.0110 -0.0115 -0.0115 -0.0120 -0.0120 200 210 220 230 240 250 260 270 280 290 300 310 Seconds -0.0100 Butyl acetate -0.0105 Methyl Acetate Stream: Butyl Acetate

  11. Methyl Acetate Stream: Summary • A single analyser application has replaced two analysers • The new method uses a single inject valve with a single capillary column cut at its mid point and re-joined with a live T. The old methods needed 2 inject valves 3 stream switch valves and 5 columns. • In addition to hardware there will be significant utilities savings and lower maintenance. • More components can be determined for free!!!

  12. Multidimensional Process GCTrace Propionic Acid in Pure Acetic Acid • Crucial for both process control and product specification. • The acids are highly polar and activewhich gives severe problemsdue to adsorption on surfaces in current process GCs with valve switching. • None of the existing analysers give satisfactory performance with the heart cut method and would not be acceptable for direct product rundown.. • Could Live switching provide the necessary performance?

  13. EPC 2 EPC 3 EPC 1 FID SPLIT TCD PURGE OUTLET Multidimensional Process GCTrace Propionic Acid in Pure Acetic Acid FFAP FFAP

  14. 0.008 ~300ppm 0.006 Propionic Acid 0.004 0.002 0.008 Residual Acetic Acid 0.006 0.000 Volts Residual Acetic Acid 600 590 580 570 560 550 540 530 520 510 610 0.004 Seconds Propionic Acid 355 ppm 0.002 0.000 Multidimensional Process GCTrace Propionic Acid in Pure Acetic Acid • LEFT Current On-lineGC where propionic acid is “heartcut” using 2 valves and 3 GC columns. Note peaks not resolved and poor peak shapes with tailing. • RIGHT Same analysis using 1Live-T and 2 columns on a Siemens Advance Maxum. There is baseline resolution between the acetic and propionic acid and less peak tailing giving lower detection limits and better accuracy and precision. Also once installed the T-piece is maintenance free. Live switching instead of valves means • From this to this with:- • Less hardware • Lower maintenance • Improved accuracy and precision • i.e. Better quality for less cost!

  15. Permanganate Time for Acetic Acid • Permanganate Time is a wet chemical test which gives a measure of the amount of readily oxidisable impurities which will react with potassium permanganate in solution. • In order to pass the pink/purple colour of the permanganate must not be discharged within the time specified for that product. For Acetic Acid the specified permanganate time is 2 hours. • All standard Pharmacopoeia and ASTM methods are based on a visual end-point relying on the detection of the pink colour of residual permanganate in a brown background. • Permanganate Time is a product specification for Acetic acid and Anhydride, Ethanol, Methanol, Acetone, Pyridine and Tricresyl phosphate. • We have now identified the impurities in acetic acid which consume the permanganate so could we infer product quality for permanganate time using results from a process GC.

  16. EPC 1 EPC2 EPC3 Live t-piece FID SLIV Col 1 FFAP Col 2 CPSil 5 NV 2 NV 3 NV 1 TCD Split vent Permanganate Time for Acetic Acid • 2 columns with a live-T for the cut and backflush. • A 15m x 530μ id J&W DB-FFAP retains the acetic acid while allowing the non-acidics to pass on to Column 2 a 30m x 530μ DB-624 and then detected by FID. • The acid is then backflushed from column 1. • Quantifies mesityl oxide (MO), methyl crotonate (MC) and methyl 3,3-dimethylacrylate (MDMA). • Cycle time for the method was 6 mins compared to 3 hours.

  17. Permanganate Time for Acetic Acid Typical chromatograms obtained from the GC method for a sample (red trace) with a permanganate time of 73 minutes overlaid with another sample (blue trace) with a predicted permanganate time of circa 24 hours

  18. Multiple Linear Regression of Residual Permanganate in Acetic Acid from GC Data

  19. Permanganate Time for Acetic Acid Summary • Product quality for acetic acid with respect to permanganate time can be inferred from process GC data by measuring ppm levels of key impurities. • A measure of product quality can be obtained on-line every 6 minutes, previous best was a lab result after 3 hours which only gave a pass or fail. • This will allow much tighter control of the process and allow product to be exported directly without intermediate storage. • It will also allow chemists to better understand what causes the formation of these impurities in the process and look for ways to minimise their production.

  20. EPC 2 EPC 3 EPC 1 FID TCD SPLIT TCD TCD CUT OUTLET PURGE OUTLET Multiple Detectors for Performance Monitoring

  21. Multiple Detectors for Performance Monitoring

  22. The Future? • The role of the laboratory GC will diminish while the role of the on-line process GC will increase • The new generation of hardware allows extensive use of multidimensional hyphenated systems and this will only increase. • Process GC can provide useful inferential measurements for other product quality tests. • Process GCs will change dramatically. They will become highly automated systems with self diagnostic fault finding allowing predictive maintenance and self validation. • Miniaturisation will further facilitate the use of fast GC and cheap multiple detectors which will allow the development on new instruments which include all the features above.

  23. A Final Message • You've carefully thought out all the angles. • You've done it a thousand times. • It comes naturally to you. • You know what you're doing, its what you've been trained to do your whole life. • You don’t need to use new technology • Nothing could possibly go wrong, right ?

  24. Think Again!

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