Chemistry Question about Fossil fuels

Question

Can u help me to ans all these q?
1)some gaseous hydrocarbons such as methane and ethane can be obtained from petroleum by refining, yet they are not found in LPG. Why?
2) although propane and butane are odourless, LPG usually has a bad smell. why?
3) wt does town gas refer to?
4)why methane is not suitable to be liquified?
5) why pentane is not suitable to be liquified?

Answer 1

1. LPG is liquified before transport (XD). however, boiling points of methane and ethane are too low. liquifying them needs very high pressure and low temp.. this is an expensive procedures, yet dangerous. hence methane and ethane are not present in LPG.
2. an odourant is added into LPG (ethanethiol), so that bad smell can be detected if there's any gas leakage, and measures can be taken immediately.
3. mxture of methane, carbon monoxide and hydrogen, with some impurities like carbon dioxide and nitrogen.
4. boiling point of methane is very low. liquifying it needs very low temp. and high pressure, requiring special, cosy facilities.
5. pentane is already a liquid! with relative low boiling point (at least higher than room temperature).