The RCD process is a method for treating heavy atmospheric and vacuum residues to transform them into high-quality products suitable for market demands. One of its primary goals is to reduce sulfur compounds (HDS) and other contaminants from RFCC feedstock while minimizing the consumption of nano-catalysts in RFCC units. This optimization significantly enhances refinery profitability, making RCD units a vital part of pre-treating RFCC feedstock.

During the RCD process, the residue from atmospheric and vacuum distillation towers (AR, VR) is filtered and pumped into fixed-bed reactors. Simultaneously, hydrogen supplied by makeup compressors enters the reactors from below. The HDS reaction takes place in the presence of nano-catalysts, and the output products are separated into gas and liquid phases. These are further processed in a fractionator and an H₂S scrubber to produce light gases, light and heavy naphtha, low-sulfur fuel oil, and sulfur-extracted hydrogen gas.

The nano-catalysts used in RCD units include nickel-molybdenum/alumina and cobalt-molybdenum/alumina catalysts. Nickel-molybdenum nano-catalysts excel in hydrogenation, while cobalt-molybdenum variants are more efficient in hydrocracking.

In Iran, the RCD process is implemented at the Imam Khomeini (RA) Refinery in Shazand to prepare feedstock for RFCC units. Operating beyond its nominal capacity of 265,000 barrels per day, the refinery produces 16 million liters of gasoline, 12 million liters of diesel, 3 million liters of Euro-4 kerosene, and approximately 1,800 tons of LPG daily.

These outputs are derived from atmospheric and vacuum distillation towers, where high-pressure, high-temperature reactions occur in the presence of nano-catalysts and 90–93% pure hydrogen gas. The result is a range of refined products, including diesel, kerosene, heavy naphtha, light raw naphtha, treated residue, and light hydrocarbons. The primary product—low-sulfur fuel oil (60,000 barrels per day)—is used as feedstock for RFCC units, while hydrocarbon gases are treated with amine to remove hydrogen sulfide and recycled into the system.

The development of these nano-catalysts was achieved through a partnership contract between the Petroleum Industry Research Institute, the knowledge-based company Shahr Catalyst Roz Arvand, and the Imam Khomeini (RA) Refinery in Shazand. Supported by the National Iranian Oil Refining and Distribution Company, this initiative focused on localizing, expanding knowledge, and scaling up the industrial production of nano-catalysts for hydrocracking and hydrotreating heavy oil fractions (RCD). After extensive laboratory evaluations and successful pilot tests at the refinery, these nano-catalysts are now utilized in strategic industries nationwide.

It is noteworthy that the RFCC unit consumes 15 tons of nano-catalysts daily. Previously, the production of these nano-catalysts was monopolized by a limited number of companies in Europe, Asia, and the United States, with imports primarily sourced from Germany, China, and Russia. This dependency resulted in significant foreign currency outflows and administrative challenges for refinery managers.

With the innovative production of advanced nano-catalysts by Shahr Catalyst Roz Arvand, Iran has become the first country in the region and the sixth globally to achieve the technical know-how and industrial-scale production of these complex nano-catalysts. Experts affirm that the localized RFCC nano-catalyst matches or exceeds international standards and quality benchmarks. This breakthrough offers competitive advantages and alleviates financial pressures on refineries, particularly in securing foreign currency for imports.