Following the development of a fixed- bed (Houdry process, 1936) and a moving-bed (Thermafor Catalytic Cracking, 1941) catalytic cracking process, fluid-bed catalytic cracking (FCC, 1942) became the most widely used process worldwide because of the improved thermal efficiency of the process and the high product selectivity achieved, particularly after the introduction of crystalline zeolites as catalysts in the 1960s.

Catalytic Cracking processes were developed during the Second World War and became widely used ever since because of their improved thermal efficiency and the high product selectivity to produce gasoline with a higher octane number. Also, catalysts and additives are very significant for the selectivity and flexibility of catalytic cracking; the introduction of zeolite catalysts in 1965 has had a huge impact on the industry processes.

In 1936, the first full scale industrial catalytic process was developed. It was known as the Houdry Catalytic cracking process, which used much less expensive catalysts, such as clay, natural alumina and silica particles. For this process, the gas oil feed stock must be heated to high temperatures and is fed to a fixed-bed reactor containing the catalyst particles. The product stream is sent to the separator to produce gas, gasoline, light cycle oil (LCO), and heavy cycle (HCO) products. A problem that faced this process was the deactivation of the catalyst bed because of coking. Thus, the process included swing reactors to switch between periodically to overcome this issue. After switching, the reactor is stripped with stream to remove the liquid products from the catalyst bed. The coke is then burnt off to reactivate the catalyst bed. A small percentage of the heat generated by burning off the coke could be used to supply heat for catalytic cracking, however the thermal efficiency of this reaction is considered low.

However, more efficient catalytic cracking processes have been developed. Such process include thermafor catalytic cracking and fluid catalytic cracking. Thermofor cracking utilizes a moving catalyst bed. In addition, catalyst particles used in this process are synthetic and thus have consistent and homogenous properties. This process is a slightly more thermal efficient process than the Houdry process. In comparison, the fluid catalytic cracking utilizes a fluidized catalyst bed. This catalytic cracking process is considered the most thermal efficient process. Also, this process enables the production of large quantities of light distillates known as crackate without the addition of hydrogen by burning off the coke.

Catalytic hydrocracking is relatively a recent addition to the petroleum industry. The main reasons for its development are the increasing demand for light and middle distillates, the large quantities of hydrogen as a by-product from catalytic reforming, and the limits imposed on sulfur and aromatics content in motor fuel. Hydrocracking is able to process a wide range of feedstocks. Its main process objective is to decrease the molecular weight and boiling point of the heavy oils from a mostly aromatic feedstock. Through the hydrocracking process, it is possible to convert an aromatic compound to a paraffin compound with out rejecting any carbon. The catalysts used for such reactions include platinum and palladium metals, however, care must be taken as they can be easily poisoned by sulfur.

Source:

Course Website

Wikipedia