Catalytic Cracking process was developed back in the 1920’s by Eugene Houdry to upgrade and put to better use residue using a process based on cyclic fixed bed configuration, which was later commercialized in the 1930’s.1 Since then the process has been altered and upgraded into its current form as a fluidized bed catalytic cracking (FCC) process.1 The feedstock for this process is often light gas oil obtained from a vacuum distillation column.1 The process takes the feedstock and cracks ow value high molecular weight hydrocarbons to more valuable products of low molecular weight. This includes products such as gasoline, LPG Diesel, petrochemical feedstock’s such as propylene, and C4 gases like isobutylene, Isobutene, and butane.1 The major reactions is the process are cracking, Isomerization, Dethrogeneration, Hydrogen transfer, Cyclization, Condensation, Alkylation, and Dealkylation.1
Today Fluid Catalytic Cracking provides 50% of all transportation fuel, and 35% pf total gasoline fuel. In the process there are several specific steps that take place. The first step is the reaction step, in which the feedstock reacts with catalyst and cracks into different hydrocarbons.1 Secondly the regeneration steps takes place, in which the catalyst is reactivated by burning off cook, and recirculated to reactor.1 The fractionation step is next, in which the cracked hydrocarbon stream is separated into its various products. 1
As technology progressed and as feed stocks became heavier with large concentrations sulfur, nitrogen, and heavy metals, a new process was in demand to obtain desirable products. Hydrocracking meet that need by providing a more versatile process which could convert low quality feed stock into high quality products like gasoline, naphtha, kerosene, diesel, and hydro wax used as petrochemical feedstock. 1 This process uses a wide variety of feedstock’s like naphtha, atmospheric gas oil, vacuum gas oils, coke oils, catalytically cracked light and heavy cycle oil, cracked residue, and deasphalted oil.1 The end products from this feed are high quality products will excellent product quality, and low sulfur content.1 The feed in this process goes from straight run gas oil, vacuum gas oils, cycle oils, coker gas oils, thermally cracked stocks, solvent deasphalted residual oil, straight run naphtha, cracked naphtha, into desirable products including liquefied petroleum gas, motor gasoline, reformer feeds, aviation turbine fuel, diesel fuels, heating oils, solvent and thinners, lube oil, and FCC feed.1
When we compare catalytic cracking to hydrocracking we see two very different processes.1 Catalytic cracking is defined as a carbon rejection process, where Hydro-cracking is hydrogen addition process. Catalytic also uses riser-regeneration-configuration, where hydro uses down flow packed bed.1 The products for catalytic are LPG’s and gasoline, and for hydro they are kerosene and diesel.1 Catalytic cracking produces products which are rich in unsaturated components, where hydro cracking results in products with few aromatics, low sulfur and nitrogen content.1
References
- Lecture 5: Catalytic Cracking: Fluid Catalytic Cracking and Hydro-cracking