The fluorine laboratory has two separate fume hoods for the handling of elementary fluorine and hydrogen fluoride. The lab is furthermore equipped for the work with other reactive gases such as carbonyl fluoride (COF2) or boron trifluoride (BF3) and high temperatures (up to 900 °C).
Besides general safety instructions, our group has developed a specialized health and safety briefing for active and neighboring staff, as well as organizational precautions including a fully equipped HF/aHF first aid kit and the so called “HF Pass” summarizing first aid measures in case of delayed intoxications. Additionally, we are using separate gas detectors for fluorine and hydrogen fluoride gas.
The Fluorine Fume Hood:
In the fluorine modified fume hood, with all the walls as well as the full ventilation system are made of V4A stainless steel, together with a raised maximum exhaust flow rate of 1200 m3/h. The fluorine gas is supplied by the Solvay Fluor GmbH and is stored in a five liter gas tank (200 g fluorine gas, 28 bar), which is safely stored inside the fume hood. Reactions with fluorine gas are carried out using a Monel vacuum line (see picture below), where all connections are sealed with Swagelok tube fitting.
Schematic diagram of Monel vacuum line setup for the work with elementary fluorine gas. Areas in red = permanently under elemental fluorine gas; blue = permanently under nitrogen; green = permanently under vacuum.
To neutralize excessive fluorine gas, the Monel vacuum line is connected to a soda lime tower, a copper cylinder filled with granulated calcium hydroxide and additionally potassium- and sodium hydroxide. The soda lime is able to neutralize both fluorine and hydrogen fluoride gas.
Located on the outside of the fume hood, there are two terminals, one for the pressure meters and one to regulate the two independent mass flow controllers for fluorine and nitrogen gas.
Currently, our fluorine lab is used for the fluorination of carboranates, solid state catalysts for the methanol synthesis, as well as cathode materials in batteries.
The Hydrogen Fluoride Fume Hood:
The hydrogen fluoride fume hood is a modified standard fume hood with a full automatic gas absorption system, localized on top of it. The system can absorb various toxic, acidic and basic gases, such as hydrogen fluoride or ammonia. It can be activated for the work and only needs two minutes to be fully operational. All parts of the fume hood and the absorption unit are made of chemical resistant plastic.
The fume hood is equipped with a stainless steel vacuum line for the work with anhydrous hydrogen fluoride gas (five liters with a maximum pressure of 2 bar) and even small amounts of elementary fluorine gas.
Schematic diagram of the stainless steel vacuum line for the work with anhydrous hydrogen fluoride and small amounts of elementary fluorine gas. Areas in red = permanently under hydrogen fluoride gas; blue = permanently under inert gas; green = permanently under vacuum.
Similar to the Monel line in the fluorine fume hood, the stainless steel vacuum line is connected to a soda lime tower to neutralize hydrogen fluoride or elementary fluorine gas.
Our group uses anhydrous hydrogen fluoride for reactions, such as the synthesis of XeF2 out of the elements. Besides this, our fluorine lab is also equipped for the work with concentrated aqueous hydrofluoric acid, which is used for example for dip coating of silicon wafers.
Residual traces of water and organic solvent can cause unwanted or even dangerous side reactions with fluorine or hydrogen fluoride. Therefore, besides to the specialized equipment shown above, we have another standard fume hood designated to the fluorine lab. It is equipped with a grease-free Schlenk line to dry reactor vessels or starting material from solvents, such as acetone or water.