Charles Kritkausky & Alex ConnorRefinement of the heaviest crude oil components relies on the hydrocracking process, in which large hydrocarbons are heated in the presence of hydrogen, breaking down into the smaller hydrocarbons commonly used as fuels. While the presence of hydrogen minimizes the formation of coke-forming radicals,

significant coke formation still occurs on a scale harmful to the reactor. The use of red med, a bauxite compound created from the production of aluminum, as a catalyst reduces coking of the reactor and provides an increase in the yield of desirable fuels in the hydrocracking reaction, making the reaction a more

sustainable process.

A representation of the hydrocracking reaction of n-Heptane

Hydrocracking is commonly used for the breakdown of vacuum residue, the heaviest crude oil fraction that is created as a byproduct of distillation. This vacuum residue is unusable as fuel, as its combustion generates a significant level of pollutants. Hydrocracking allows this previously unusable fuel source to be utilized as light fuels such as diesel.

In order to perform hydrocracking in an efficient manner, catalysts are necessary to limit coking. The creation of coke obstructs and potentially damages the reactor, incurring high maintenance and labor costs if left unchecked. The use of catalysts limits the formation of coke, and helps decrease these costs. However, previously available catalysts were expensive and contained rare metals like molybdenum and tungsten, limiting the sustainability of the process. Red mud is a superior catalyst to those previously available, as it is more effective at limiting coking and is available for a significantly cheaper price.

Prior to the discovery of its catalytic properties, red mud was considered to be a dangerous waste product. Over 70 million tons of red mud are produced each year, which is primarily stored in ponds as no application had was previously available. Red mud samples have pH levels as high as 13, and its storage raised major concerns pertaining to public safety, groundwater pollution, and soil contamination. An example of the hazards associated with red mud storage is the 2010 spill in Ajka, Hungary, in which one of these storage ponds ruptured, killing four people and contaminating 40 square kilometers of land. The use of red mud as a catalyst not only increases the sustainability of oil refinement, but removes a harmful pollutant from the environment as well benefitting environmental sustainability as well.

Image of the area surrounding the red mud spill in Ajka, Hungary in 2010

Ongoing research is focusing on the activation of red mud, which further decreases coke formation and increases yields of desirable fuels. Current methods include the introduction of red mud into acidic solution, and imprinting with colloidal polystyrene particles. Each of these methods increases the surface area of the sites on the molecule that interact with large hydrocarbons like those found in vacuum residue, making the catalyst more effective in facilitating the reaction. The use of red mud molecules imprinted with polystyrene particles with a diameter of less than 700 nanometers has been found to provide the best catalytic performance.

Comparison of the yield of the hydrogen reaction using variously activated red mud

HYDROCRACKING OF VACUUM RESIDUE AND THE USE OF RED MUD CATALYSTS