Steam cracking and FCC

FCC stands for catalytic cracking, a process that converts heavy oils into lighter ones; the end products are gasoline, diesel, and liquefied gas. You can learn more about this in the area dedicated to exchanges on refining technologies. Steam cracking to produce ethylene and propylene? I don’t understand what that means – steam cracking? Please describe it in detail as well.

Steam cracking: Petroleum hydrocarbons such as ethane, or petroleum fractions such as naphtha (gasoline) and gas oil (diesel), undergo molecular fragmentation and dehydrogenation reactions at high temperatures (above 750°C) in the presence of water vapor, along with minor reactions such as polymerization and condensation. The main purpose of steam cracking in industry is to produce ethylene, as well as by-products such as propylene and butadiene, which are low-molecular-weight olefins, and light aromatic hydrocarbons like benzene, toluene, and xylene; in addition, small amounts of heavy aromatic hydrocarbons are also generated. Steam cracking is an endothermic reaction that usually takes place in a tubular furnace: the feedstock and steam are preheated before being fed into the furnace tubes, where they are heated to 750–900°C to undergo cracking. Subsequently, they enter a quench boiler to cool down rapidly, then pass through a quencher and cryogenic separation units (at temperatures below –100°C), from which various cracking products are obtained. Steam cracking is the main method for producing low-molecular-weight olefins such as ethylene and propylene, and it forms the basis of the robust petrochemical industry. The above content is from Baidu Baike; I believe it’s sufficient to understand what steam cracking means. Steam cracker, that is, a steam cracking unit, should be mentioned in English literature. FCC refers to the explanation given by fross-zhang above, namely catalytic cracking. Catalytic cracking is one of the processes in petroleum refining; it involves the cracking of heavy oils under the action of heat and catalysts, resulting in the production of cracked gas, gasoline, diesel, and other products. The raw material is heavy distillate oil obtained through crude oil distillation (or other petroleum refining processes); or deasphalted residue resulting from mixing a small amount of residue oil into heavy distillate oil and then subjecting it to solvent deasphalting ； Or all use atmospheric residue or vacuum residue. During the reaction process, non-volatile carbon-like substances deposit on the catalyst and condense into coke, reducing the catalyst’s activity. It is necessary to burn off this coke using air (see catalyst regeneration) in order to restore the catalyst’s activity and provide the heat required for the cracking reaction. Catalytic cracking is one of the main processes in oil refineries for producing gasoline from heavy oils. The gasoline produced has a high octane rating (around 80 on the Motor Method), good stability, and the cracking gas (a type of refinery gas) contains large amounts of propylene, butylene, and isomeric hydrocarbons.

Olefins are present in the cracking gas and require further separation