General questions concerning flow chemistry

  1. How much compound can be reduced on one catalyst column?

    It depends on the type and the molecular weight of the compound; with the shortest column, on average, at least 500 mg is reduced, but we have reduced up to 10g of certain compounds without any catalyst deactivation.

  2. What kind of solvents cannot be used in the H-Cube®?

    • With the PEEK H-Cube®:

      Marginally Suitable (these solvents do not attack the PEEK tubing but may cause swelling which may weaken the PEEK tubing)

      • Dichloromethane (DCM)
      • Tetrahydrofuran (THF)
      • Dimethyl sulfoxide (DMSO)
      • Triethylamine (TEA)

      Not recommended (these chemicals will attack the PEEK tubing)

      • Aqua regia
      • Bromine/dibromoethane
      • Bromine (dry)
      • Bromine (wet)
      • Chlorine (liquid)
      • Hydrobromic acid (100%)
      • Hydrobromic acid (20%)
      • Hydrobromic acid (10%)
      • Hydrofluoric Acid (100%)
      • Nitric acid (100%)
      • Phenol (conc.)
      • Sulphuric acid (100%)
      • Sulphuric acid (70%)
    • With the SS H-Cube

      Not recommended:

      • Aqua regia
      • Bromine/dibromoethane
      • Bromine (dry)
      • Bromine (wet)
      • Chlorine (liquid)
      • Hydrobromic acid
      • Hydrofluoric Acid
      • Nitric acid
      • Phenol
      • Sulphuric acid
      • Hydrochloric acid

    Usual solvents to be used are: EtOH, MeOH.

  3. How long does the electrolytic cell last for?

    The guarantee for the cell is one year.

  4. What happens with the Oxygen?

    It is separated from the hydrogen by an SPE (Solid Polymer Electrolyte) membrane, and then recycled back out of cell with the water and is vented out the back of the instrument.

  5. What can I do if ThalesNano doesn’t supply the catalyst that I want?

    If you describe what you want, ThalesNano can prepare it for you. Ask info@thalesnano.com [1] for details.

  6. How many times is it recommended to top up the water level?

    When full, the water reservoir has enough water to generate hydrogen for a full working week. However, for the sake of procedure, we recommend you check the water level every day, e.g. every morning before you start working with H-Cube®. The stainless steel model has a water level monitor on the touch screen.

  7. Is there a safety shut-off if the water tank is empty?

    Yes. A message will appear warning the user that the water tank is empty and the user will not be allowed to operate the H-Cube® until the water tank has been refilled.

  8. What happens if the cell runs dry?

    The membrane inside the cell will dry out and it eventually causes the cell to malfunction.

  9. How pure is the Hydrogen and how much is the water content of it?

    99.99% H2. A water separator is responsible for the removal of H2O.

  10. How do you dispose of a used CatCart®?

    A deactivating vial containing a solution of sodium hydrogen sulfite comes with a CatCart® purchase. Once the CatCart® is finished with, it is placed in the deactivation vial and this renders the catalyst non-pyrophoric. You can dispose of the deactivated cartridge in the same way as you would heterogeneous catalyst from a batch reactor.

  11. What is the internal volume of hydrogen in the H-Cube®?

    The internal volume of hydrogen at 1 bar is approximately 3 cm3, therefore at 100 bar is 300 cm3.

  12. Do you have any cross-contamination when using different compounds on the same cartridge?

    If enough washing with fresh solvent and hydrogen is allowed between samples, e.g. 10 ml, to wash off any residual product from the column there will be no cross-contamination. The amount of solvent used depends on how polar the compound is and the type of solvent used.

  13. Do you have to degas the solvent before the reaction?

    No, because the amount of O2 is too small.

  14. How can you perform selective hydrogenation reactions?

    The user can vary the pressure of hydrogen (Henry's Law), temperature or use a more selective catalyst from the list.

  15. What is the maximum H2 flow?

    30 cm3/min (in Full H2 mode).

  16. What is the volume of the reaction line?

    Approximately 2.5 cm3 including the CatCart®, therefore the time taken for the compound to pass through the reactor at 1mL/min is 2.5 minutes.

  17. Is there any partially poisoned catalyst available?

    A selection of poisoned catalysts for selective reduction are available, including Lindlar's catalyst and Pt sulfided catalysts.

  18. Can the catalyst in the CatCart® be used longer than the catalyst in a batch reactor?

    In certain reactions, the product formed, e.g. primary amine, will bind strongly to the catalyst leading to deactivation overtime. In the H-Cube®, the deactivation will take place over a longer period of time because the deactivating product is always flowed out of the catalyst, so the product has a very short residence time on the catalyst. In a batch reactor, the product, starting material, and catalyst mixture are always in contact with each other throughout the entire experiment, so as the product concentration increases the deactivation of the catalyst will also increase.

  19. How do we know that the catalyst is still active after repeated use?

    You can either try one of the validation reactions (e.g. 5-nitroindole reduction), or you can make your reactions in more fractions, test the result of each, and recycle back the non-reduced fraction on a new column.

  20. What happens if there is a H2 leak inside the machine?

    There is a H2 detector, which automatically shuts down the H-Cube® when hydrogen is detected. The power supply is located in a separate unit outside of the H-Cube® box to remove the risk of sparks.

  21. Does the machine stop automatically if the pressure goes higher than 100 bar?

    No, but the HPLC pump cannot generate more than 200 bars, and the machine is tested to survive that pressure. Also, a pressure which is too much for the HPLC pump is indicated on the flow rate display with a blinking “57”, and the pump will stop, which results in the quick drop of the pressure.

ThalesNano Nanotechnology Inc, H-1031 Budapest, Záhony u. 7., Graphisoft Park, Hungary
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