How difficult is the purification process? Is it as difficult as uranium hexafloride gas?
Yes, gas centrifuge appears to be a leading method.
'The purification starts with “simple” isotopic purification of silicon. The major breakthrough was converting this Si to silane (SiH4), which is then further refined to remove other impurities. The ultra-pure silane can then be fed into a standard epitaxy machine for deposition onto a 300-mm wafer.'
https://www.eejournal.com/article/silicon-purification-for-q...
Doesn’t silane like catching fire when it sees an oxygen molecule? The other day I heard about it being used as rocket fuel for lunar ISRU applications.
A rocket and a sandblaster at the same time.
This is no worse than before. All electronic grade silicon is already produced starting from silane or trichlorosilane, and both are about equally hazardous to handle. See this overview of producing purified silicon:
"Chemistry of the Main Group Elements - 7.10: Semiconductor Grade Silicon"
https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/...