Cracking Help

[renny 123]

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What is the difference between thermal/steam cracking and catalytic cracking? I know what each does but how is what they produce different? Or when is each Used?

Thankyou

[~caramello~]

My understanding is that Catalytic cracking is used to break down long hydrocarbons into an alkane and an alkene. It can't break down a molecule completely to ethylene like steam cracking can. Thermal/Steam breaks the hydrocarbons into very small chains like ethylene.

[annabackwards]

Catalytic cracking
- temp is ~500c
- uses zeolites as a catalyst
- decomposes large carbon chained hydrocarbons into alkanes and alkenes. But usually they are larger alkanes and alkenes (instead of ethene) and so process has to be repeated

Thermal or Steam cracking
- temp is 700 - 1000c
- no catalyst involved
- completely breaks it down to ethene without having to repeat the process; no alkanes produced

[mostwanted092]

Ethylene originates form crude oil which is obtained from biomass.

Catalytic cracking
the crude oil is taken to a fractional distillator where it is distillated to separate the large hydrocarbons from the small hydrocarbons. the large hydrocarbons are then catalytically cracked form higher molecular weight hydrocarbons into smaller molecular weight hydrocarbons. this is produced under high temp., the presence of a catalyst (zeolite)

Thermal cracking is the non catalytic process. it involves mixing the hydrocarbons with steam then passing it through a very hot copper tube

HOPE IT HELP!! =)

[emmcyclopedia]

^^ agreeing with everyone here =]
BUT would just like to add that for the chemistry syllabus, and according to HSC marker Patricia Stockbridge, we are only required to know about catalytic cracking and NOT thermal/steam cracking for our exams =]

[annabackwards]

^
If that's the case, then even better. That's one thing less i have to remember ^^

[renny 123]

Thankyou everyone