Write a blog post comparing catalytic cracking and catalytic hydrocracking processes with respect to feedstocks, process objectives, and products.

Catalytic cracking is a process utilized by petroleum refineries which has been around for nearly a century. The reason this process became so popular is mainly due to its increased yield of gasoline with a higher octane rating, compared to a yield that would be achieved from thermal cracking. This process differs in a few ways from thermal cracking, as catalytic cracking incorporates the use of a catalyst, is more flexible in its feedstock, and does not require as high of temperatures and pressures as thermal cracking would.

Amongst the different types of catalytic cracking processes is Fluid Catalytic Cracking (FCC), introduced in 1942. This process in particular has seen a large use in the refining industry as it has a very flexible feedstock, which is usually straight-run atmospheric gas oil (AGO) and light vacuum gas oil (LVGO). Utilizing an acidic catalyst, long chains of n-alkanes are broken into shorter branched chains of isoalkanes, as well as cycloalkanes and aromatics. Different methods of catalytic cracking are used in refineries to produce LPG, cycle oils, and light hydrocarbons such as propane and butane, in addition to high-octane gasoline. Through alkylation and polymerization, these light hydrocarbons are used as feedstock to produce higher molecular weight isoalkanes and olefins which ultimately end up in the high-octane gasoline pool. Coking occurs during the cracking reactions, which works to deactivate the catalyst. When the coke is burned off with air, the temperature of the catalyst particles increases from the heat released by this, which provides the required energy for cracking to occur with minimal loss. This is what ultimately makes the cracking process so thermally efficient.

In 1958, the first commercial use of a process known as catalytic hydrocracking occurred. While catalytic cracking can support a wide range of feedstocks, hydrocracking is even more flexible and selective. Its main use in the refining industry is for its ability to produce light and middle distillates including large amounts of hydrogen, as well as its respect for environmental regulations that seek to limit the quantities of sulfur and aromatic hydrocarbon emissions. While these are all useful items, the overall goal of this process is to produce diesel and jet fuel from highly aromatic feedstocks such as residue and LGO from FCC. This is achieved by causing a decrease in the molecular weight and boiling point of heavy oils. The incorporation of bi-functional catalysts systems helps to keep coking under control. Hydrocracking involves a hydrogen-addition process, providing high yields of the desired distillates while avoiding the production of low-grade byproducts such as heavy oils, gas, and coke.