The hydrocarbon feedstocks, the raw materials used in petroleum refining industry, need to be refined before they can be used in numerous products and processes. A large part of the hydrocarbon feedstocks are submitted to a so called hydrotreating process. The purpose of hydrotreating is to reduce the amounts of impurities in the hydrocarbon feedstocks.
In particular, hydrotreating aims the removal of sulfur and nitrogen compounds.
The hydrocarbon feedstocks often contain sulfur and nitrogen compounds. These compounds are responsible of the release of sulfur oxides and nitrogen oxides in the atmosphere when the hydrocarbon products are used as fuel and burnt. These sulfur oxides and nitrogen oxides are considered harmful for the environment. As a consequence, national and international regulators are continuously imposing lower nitrogen and sulfur contents in fuel so as to reduce pollution of the environment by reducing as much as possible the quantities of these compounds when the fuel is burnt. There is thus an increased need to develop more efficient hydrotreating processes.
The efficiency of hydrotreating process relies in part on the activity of hydrotreating catalysts used. These catalysts allow converting feedstocks into useable materials. Nevertheless, during use, the activity of the hydrotreating catalysts decreases. The resulting spent catalysts may thus be used in less demanding kinds of hydrotreating processes after they are at least regenerated.
However, the regenerated catalysts do not show as high activity as the original catalysts due to agglomerates of the catalyst metals formation.
Numerous processes have been developed in order to reactivate the spent catalysts such as for example the so called rejuvenation process. The rejuvenation aims to restore the original activity of the catalysts or at least an activity superior to the one obtained after a simple regeneration step. However, the efficiency of the rejuvenation process may depend on several parameters such as: the catalyst to be treated, the operational conditions of the process or the rejuvenating agent used.
Thus, there is still a need to develop efficient and easy to implement processes for restoring the activity of the spent catalysts.