My replies to me356 are inline below, with further comments to follow
To fix very fast filling I recommend to add extra volume to the cell, at least by connecting there extra empty cylinder with roughly 50x of the current reactor volume. This will help in at least 3 different ways. When volume is bigger than even with the current valve system it should be much easier to add exact amount of D.
The filling of the cell was done carefully, using three calibrated steps of isolated volumes between the gas cylinder and the cell. The amount of gas is therefore well controlled. In this case it was the amount of D2 that produced 250 Pa of pressure in the cell with no mesh during repeated calibration of this process.
possibilities why this is happening:
1 Mesh was saturated with Hydrogen in some way we dont know prior the run - for example from transportation - we have no idea what airplane shipping is doing to the meshes.
This seems to be the most likely explanation. One thought: he meshes were packed in individual zip-lock bags, where they remained for weeks or months prior to my use. The references below suggest that under some conditions Palladium might strip hydrogen directly from polyethylene. Perhaps Alan Smith will comment on this.
2 There was outgasing of the reactor in some way
There is always some outgasing from this reactor at 250C. Past analysis by mass spec. showed this to be substantially nitrogen, which is present in stainless steels from the foundry process. Typically this is 3-5 Pa/hr after settling, in line with what is currently shown in the chart below.
References:
From https://link.springer.com/article/10.1007/s11244-021-01452-x
Ali et al. showed that dehydrogenation beyond equilibrium was possible using a catalytic reactor with a palladium-silver tubular membrane to separate the produced hydrogen in-situ.
From
https://www.science.org/doi/10.1126/science.add1088
Conk et al. developed a preliminary method to produce propylene from a sequence of reactions between waste polyethylene and fresh ethylene. Specifically, the process involves a small extent of desaturation of each polyethylene chain by a dehydrogenation catalyst,