DCHAS-L Archives, Jul 14, 2023 - Re: [DCHAS-L] Filling balloons with hydrogen gas

Hi Craig,

Thank you very much. The OPRD article is very helpful.

Parr hydrogenation instruments and reactors are very effective for safe hydrogenation at lab scales. Maximum fires during hydrogenations occur during the catalyst transfer to the vessel (rxn. flask) and the catalyst filtration (product isolation). The researcher must be aware of catalyst transfer safety and filtration tricks (not to use a high vacuum and keep the Celite and catalyst bed wet). When the researchers are unaware of these hazards and hazard elimination strategies, that is the biggest challenge. The lab's housekeeping also plays an important role in preventing fire during catalyst manipulations. Even a few catalyst particles with adsorbed hydrogen on their surfaces can initiate a fire. It is all about skills and applying best practices for such manipulations.

Sincerely,

Tilak

From: ACS Division of Chemical Health and Safety DCHAS-L**At_Symbol_Here**Princeton.EDU On Behalf Of Craig Merlic
Sent: Thursday, July 13, 2023 10:57 AM
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Subject: Re: [DCHAS-L] Filling balloons with hydrogen gas

All,

A key point for this discussion is reaction scale. Yes, a dedicated line would be nice, but many synthetic organic chemists might run reactions at 0.0001 to 0.1 mol scale. Assuming 1 mol at STP is 22.4 L, then only 0.002 to 2.2 L of hydrogen gas is needed. So a “party” balloon ends up being very convenient. A ¼” pressurized stainless steel line is not convenient to deliver 20 mL of gas. So balloons have indeed been used for decades. That said, I do agree that walking around the lab holding a rubber balloon filled with hydrogen gas is not a good idea.

For 0.1 to 1 mol scale, and especially when pressure is needed, synthetic chemists will use a Parr Hydrogenation apparatus with a dedicated line from the hydrogen cylinder.

https://www.parrinst.com/products/hydrogenation/

Hydrogen gas is very hazardous, but used hydrogenation catalysts have been the source of many small lab fires, so a very important paper on this topics is:

“Influence of Solvents and Additives on the Pyrophoricity of Palladium on Carbon Catalyst after Hydrogenation” Christine Fannes,* Stef Verbruggen, Bart Janssen, and Brecht Egle, Org. Process Res. Dev. 2021, 25, 2438−2441. https://doi.org/10.1021/acs.oprd.1c00190

Craig

Craig A. Merlic

Professor of Chemistry, UCLA Department of Chemistry and Biochemistry

Executive Director, UC Center for Laboratory Safety

http://cls.ucla.edu

Los Angeles, CA 90095-1569

From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> on behalf of Alyssa Brand <abrand**At_Symbol_Here**LBL.GOV>
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Date: Wednesday, July 12, 2023 at 10:13 AM
To: <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Subject: Re: [DCHAS-L] Filling balloons with hydrogen gas

Let me preface this with: I am no expert in the safe use of hydrogen gas. But I wonder why a balloon would be used rather than a dedicated, regulated gas line. My main concern with this would be the potential for ignition of the hydrogen due to a static electricity discharge, and I would think that using plastic components might not only increase the risk of a static discharge occurring, but prevent the use of bonding and grounding. If I'm entirely off base, feel free to ignore me. As I said, not an expert.

Alyssa

On Fri, Jul 7, 2023 at 10:54 AM davivid <davivid**At_Symbol_Here**well.com> wrote:

We do hydrogenations and hydrogenolysis in our lab in quantities of up
to several moles. The equipment is assembled in a hood. Hydrogen is
plumbed into the hood via 1/4" polyethylene tubing cable tied to the
drop ceiling from tanks located elsewhere in the lab. The hydrogen
regulator is set to deliver the lowest feasible pressure and the outlet
valve set to deliver the lowest feasible flow.

The assembled equipment is charged with the reactants and solvents then
evacuated using a small diaphragm pump in the hood through a stopcock. A
two-way stopcock can be used but a three-way stopcock is preferred as it
does not require disconnection of the tubing from the system when
switching between evacuation and fill. Hydrogen is then let into the
evacuated system via the stopcock and fills the balloon. The hydrogen
flow can be shut off at the system using the stopcock. If desired, the
evacuation and fill procedure can be repeated multiple times to flush
residual air from the system.

We use mylar balloons from the Dollar Store as they are more capacious,
stronger, less permeable, and more solvent resistant than rubber
balloons. If you go this route you will need to fit the tubing several
inches into the mouth of the balloon to reach past the internal valve.

The attached photo shows the method we use to connect the balloons to
the system. A gas inlet adapter is fitted with Tygon tubing which then
connects to 1/4" polyethylene tubing. The joint between the two types of
tubing is secured by two wraps of cable tie and sealed with grease. The
tubing extends into the balloon to the point indicated by the arrow. The
joint between the balloon and the 1/4" line is sealed with grease and
fastened by wrapping several times with the ribbon from the balloon.

Best regards
Dave Lane
Chief Science Officer
Artisyn Laboratories

On 7/6/23 12:27 PM, Laura Cunningham wrote:
> Hi all,
>
> Does anyone have recommendations on how to *safely* fill a balloon with hydrogen? The hydrogen tank in this scenario is in an open lab, and the hydrogen filled balloon is for a hydrogenation reaction. The gas tank is located close enough to a fume hood that piping the hydrogen into the fume hood might be feasible. Wondering what other people’s experiences have been with this.
>
> Thanks,
> Laura
>
> Sent from Proton Mail for iOS
>
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