Desulfurization
Sulfur containing compounds are one of the most common contaminants in hydrocarbons. It must be mentioned even a trace amount of these compounds can cause different problems such as corrosion, reducing process efficiency, environmental hazards & undesirable side reactions.
Niroonamad adsorptive desulfurization technology (ADS) is a promising and economical method with regard to energy consumption, because the adsorption process can be achieved at ambient pressure, temperature and without use of any expensive hydrogen as well as catalyst. This method relies on surfer’s compounds absorption & does not require hydrogen. In the adsorption process, the adsorbents used in the process selectively grab the sulfur.
The removal of sulfur from transportation fuel and petrochemicals is gaining more attention due to the increased awareness of the adverse effects of burning sulfur containing oils on human health and the environment. Furthermore, these compounds also cause corrosion & deactivation of the catalysts.
The traditional method for eliminating sulfur from fuel is the hydrodesulfurization process, where light sulfur compounds (such as sulfides, thiols, and thiophenes) react with hydrogen at high pressure (> 3 MPa) and temperature (300–500 °C) to form hydrogen sulfide and reduce the sulfur content in the fuel. Nevertheless, refractory sulfur containing compounds, such as dibenzothiophenes (particularly with alkyl substituents at 4 and 6 positions), barely react with hydrogen under these operating conditions and remain in the fuel. Thus, alternative technologies have been proposed such as adsorptive desulfurization (ADS), oxidative desulfurization (ODS), extractive desulfurization (EDS) & bio desulfurization (BDS).
Oxidative desulfurization is a method in which chemical reaction on proceed between an oxidant and sulfur containing compounds. Generally, ODS process involves two phases: In the first phase oxidation of sulfur takes place, then in second phase sulfur removed from the starting material. There are two major problems associated with ODS. First, the oxidants chosen do not always perform selectively. Some oxidants cause unwanted side reactions that reduce the quantity and quality of the light oil. The second problem is the selection of a suitable solvent for the extraction of the sulfur compounds. Using the wrong solvent may result in removing desirable aromatic/olefin compounds from the fuel or extracting less than desired amount of the sulfur compounds from the fuel. Reaction selectivity, safety and cost are important concerns for the selection of oxidant, catalyst and operating conditions for ODS processing.
For EDS, a special type of solvent such as acetonitrile, N, N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and N-methylimidazole (MIM), can extract sulfur containing compounds. Like the second phase of ODS process using the wrong solvent may result in removing desirable compounds. In addition, these solvents dissolve much in oil. This phenomenon resulted in a loss of extractant and secondary pollution of the oil.
BDS has drawn wide attention recently because of its green processing of fossil fuel. However, the slowness of the removal process is a major hindrance in the use of BDS process.
Niroonamad adsorptive desulfurization is a high performance treatment process without using any chemicals such as solvents. In this process, feed is treated via special type of adsorbents to remove undesirable sulfur containing compounds. The process properties are as follow:
- Low operating costs & initial capital investments compared to other desulfurization processes
- Adsorbent is Multiple re-generable, can be re-activated several times
- Mild operating conditions (low temperature & pressure)
- This process does not require expensive hydrogen
- Adsorption of contaminants on the active sites of the pores of adsorbent
- Environmentally safe to dispose adsorbents once exhausted.
