I got this question in a practice test and looking through the textbook/tsfx i couldnt find out it was done.

The furthest I got was that the propane loses a methyl group (-CH3) and the spare bond from that disconnection forms a double bond which makes ethene.

Is that how it works? What catalysts/conditions are needed?

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2 Answers

C3H8 becomes C2H4 by losing a CH4 (do the atom 'accounting', i.e: 3 carbons in propane, 2 carbons in ethene, so 1 carbon left over - repeat for hydrogen).

Therefore, the reaction is simply that propane turns into ethene and methane. This process is under the umbrella term of 'cracking' type reactions. A cracking reaction is one a hydrocarbon is 'cracked' into various smaller molecules.

Usually you need high temperatures to do this, but no oxygen, or else the propane would combust - we don't want that ;-). Without a catalyst it is referred to as thermal cracking, with a catalyst (I don't know which one), it is called catalytic cracking. I studied this in the old VCE Chemistry course (before 2008), but I'm not sure if it is still relevant to the new study design.

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to  Mr.Li..
I wanna ask you for a question..
for new paten by BASF (Process making isopropanol from propane).it describe that in the dehidrogenation&propane cracking (as step 1 in IPA plant),that invention need Oxygen and steam?
what funtion of they performance of that reaction?

second, to get propylene need dehydrogenation reaction, but why in that reactor comprising propane cracking and its product are methane and ethene.. They're as impurities in further step.
So, what must there propane cracking??

sorry to disturb..
tx before..

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